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Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
Construction Project Management: A Practical Guide to Field Construction Management
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Construction Project Management: A Practical Guide to Field Construction Management

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  • 1. Table of ContentsÂTitle PageCopyright PagePrefaceÂChapter 1 - Construction PracticesÂ1.1 Introduction1.2 Construction Industry1.3 Construction Project1.4 Project Stages1.5 Owner1.6 Architect-Engineer1.7 Prime Contractor1.8 Competitive Bidding1.9 Negotiated Contracts1.10 Combined Bidding and Negotiation1.11 Subcontracting1.12 Design-Bid-Construct1.13 Fast Tracking1.14 Construction Contract Services1.15 Construction Services1.16 Design-Construct1.17 Construction Management1.18 Fixed-Sum Contract1.19 Cost-Plus-Fee Contracts1.20 Work-by-Force Account1.21 Turnkey and BOT Contracts1.22 Speculative Construction
  • 2. 1.23 Management during the Design Phase1.24 Management of Field Construction1.25 Project Manager1.26 Project Manager QualificationsÂChapter 2 - Management SystemÂ2.1 Need for Project Management2.2 Project Management Characteristics2.3 Discussion Viewpoint2.4 Management Procedures2.5 Time and Cost Management2.6 Planning and Scheduling2.7 CPM Procedure2.8 Time Monitoring and Control2.9 Project Cost System2.10 Estimating the Project2.11 Project Cost Accounting2.12 Resource Management2.13 Project Financial Control2.14 Automating Project Management Tasks2.15 Manual Methods2.16 Discussion Format2.17 Example ProjectÂChapter 3 - Project Cost EstimatingÂ3.1 Project Cost System3.2 Preliminary Cost Estimates
  • 3. 3.3 Final Cost Estimate3.4 Highway Bridge3.5 Quantity Survey3.6 Management Input3.7 Field Supervision3.8 Construction Methods3.9 General Time Schedule3.10 Construction Equipment3.11 Summary Sheets3.12 Material Costs3.13 Labor Costs3.14 Indirect Labor Costs3.15 Labor Unit Costs3.16 Equipment Cost Estimating3.17 Equipment Expense3.18 Determination of Equipment Cost Rates3.19 Equipment Production Rates3.20 Bids from Subcontractor3.21 Project Overhead3.22 Home Office Overhead3.23 Markup3.24 Contract Bonds3.25 Recap Sheet3.26 Project BudgetÂChapter 4 - Project PlanningÂ4.1 CPM Procedure4.2 Planning Phase4.3 Job Activities4.4 Job Logic
  • 4. 4.5 Restraints4.6 Beginning-to-End Planning4.7 Top-Down Planning and the Work Breakdown Structure4.8 Precedence Notation4.9 Precedence Diagram4.10 Network Format4.11 Lag Relationships4.12 Precedence Diagram for Highway Bridge4.13 Value of Precedence Network4.14 Repetitive Operations4.15 Network Interfaces4.16 Master Network4.17 Subnetworks4.18 Computer Applications for PlanningÂChapter 5 - Project SchedulingÂ5.1 Scheduling Procedure5.2 Activity Times5.3 Rules for Estimating Activity Durations5.4 Estimating Activity Durations5.5 Time Contingency5.6 Project Weather Delays5.7 Network Time Computations5.8 Early Activity Times5.9 Project Duration5.10 Late Activity Times5.11 Total Float5.12 Critical Path5.13 Free Float5.14 Activity Time Information
  • 5. 5.15 Float Paths5.16 Early-Start Schedule5.17 Tabular Time Schedules5.18 Activities and Calendar Dates5.19 Calendars for Weather5.20 Sorts5.21 Lags between Activities5.22 Pipeline Scheduling Computations5.23 Pipeline Summary Diagram5.24 Interface Computations5.25 Hammock Activity5.26 Milestones5.27 Time-Scaled Networks5.28 Nature and Significance of Floats5.29 Bar Charts5.30 Bar Chart for Repetitive Operations5.31 Computer Applications for SchedulingÂChapter 6 - Production PlanningÂ6.1 Introduction6.2 Planning Team6.3 Reengineering the Project6.4 Planning for Production6.5 Support Planning6.6 Technical Problems6.7 Personnel Planning6.8 Safety Planning6.9 Planning for Quality6.10 Material Ordering and Expediting6.11 Material Handling, Storage, and Protection
  • 6. 6.12 Equipment Planning6.13 Production Methods6.14 Activity Planning6.15 Production Checklists6.16 Look-Ahead Schedules6.17 Planning the Paperwork6.18 Putting the Plans on PaperÂChapter 7 - Project Time AccelerationÂ7.1 Time Schedule Adjustments7.2 Need for Time Reduction7.3 General Time-Reduction Procedure7.4 Shortening the Longest Time Path7.5 Project Direct Costs7.6 Variation of Activity Direct Cost with Time7.7 Project Indirect Costs7.8 Time-Cost Trade-off by Computer7.9 Practical Aspects of Time Reduction7.10 Reduction of the Highway Bridge Duration7.11 Time Reduction of Highway Bridge by Expediting7.12 Least-Cost Expediting of the Highway Bridge7.13 Limitations on Time-Reduction Steps7.14 Variation of Total Project Cost with Time7.15 Expedited Highway Bridge Schedule7.16 Milestone and Interface Events7.17 Project ExtensionÂChapter 8 - Resource Management
  • 7. Â8.1 Objective8.2 Project Resource Management8.3 Aspects of Resource Management8.4 Tabulation of Labor Requirements8.5 Project Labor Summary8.6 Variation in Labor Demand8.7 Manpower Leveling8.8 Heuristic Manpower Leveling8.9 Numerical Example8.10 Labor Leveling in Practice8.11 Restricted Labor Supply8.12 Complex Labor Scheduling8.13 Equipment Management8.14 Equipment Scheduling8.15 Software Application8.16 Material Scheduling8.17 Subcontractor Scheduling8.18 Resource ExpeditingÂChapter 9 - Project Time ManagementÂ9.1 Time Management System9.2 Aspects of Time Management9.3 Key-Date Schedules9.4 Adjustment of Move-in Date9.5 Detailed Schedules9.6 Progress Measurement9.7 Progress Reporting9.8 Bar Charts
  • 8. 9.9 Highway Bridge as of July 149.10 Weekly Progress Reports9.11 Field Progress Narrative9.12 July 21 Status of Highway Bridge9.13 Progress Analysis9.14 Corrective Action9.15 Network Updating9.16 Manual Updating Calculations9.17 Scheduling Software9.18 Schedule Information on the Job9.19 Project Progress CurvesÂChapter 10 - Project Cost SystemÂ10.1 Objectives of a Cost System10.2 Project Cost Control10.3 Data for Estimating10.4 Project Cost Code10.5 Usage of Project Cost Code10.6 Project Cost Accounting10.7 Labor and Equipment Costs10.8 Cost Accounting Reports10.9 Labor Time Reporting10.10 Time Card Preparation10.11 Measurement of Work Quantities10.12 Work Quantities from Network Activities10.13 Cost Records and Reports10.14 Weekly Labor Reports10.15 Weekly Labor Cost Report10.16 Equipment Cost Accounting10.17 Charging Equipment to the Project
  • 9. 10.18 Equipment Time Reports10.19 Weekly Equipment Cost Report10.20 Special Aspects of Equipment Charges10.21 Monthly Cost Forecast10.22 Time-Cost Envelope10.23 Earned Value Management System10.24 Forecasting Final Project Results Using the EVMS10.25 Special Cost Accounting Problems10.26 Production Cost Reduction10.27 Information for Estimating10.28 Postproject Evaluation10.29 Software Applications10.30 Accuracy of EstimatingÂChapter 11 - Project Financial ManagementÂ11.1 Financial Control11.2 Progress Payments11.3 Pay Requests for Unit-Price Contracts11.4 Project Cost Breakdown11.5 Pay Requests for Lump-Sum Contracts11.6 Use of Time-Control Activities for Pay Requests11.7 Pay Requests for Cost-Plus Contracts11.8 Payments to Subcontractors11.9 Schedule of Payments by Owner—Unit-Price Contract11.10 Schedule of Payments by Owner—Lump-Sum Contract11.11 Final Payment11.12 Cash Flow11.13 Cash Disbursement Forecasts11.14 Cash Income Forecasts11.15 Disbursement Controls
  • 10. 11.16 Project Changes11.17 Contract Change Orders11.18 Claims11.19 Daily Job LogÂChapter 12 - Scheduling ApplicationsÂ12.1 Role of the Schedule12.2 Operational Schedules12.3 Schedule Presentation Formats12.4 Schedule Analysis to Determine Project Delays12.5 Impacted Baseline Schedule12.6 But-for or Collapsed As-Built Schedule12.7 Legal Schedules12.8 Handling Weather Effects and Other Unknowns12.9 Presenting the ScheduleÂA - Highway Bridge Bid-Item Summary SheetsB - SI Unit Highway Bridge Bid-Item Summary SheetsC - Highway Bridge Project OutlineD - Arrow NotationE - The PERT ProcedureF - Analysis of Estimating AccuracyG - Highway Bridge Case StudiesIndex
  • 11. This book is printed on acid-free paper.  Copyright © 2008 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in CanadaÂNo part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978)646-8600, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at www.wiley.com/go/permissions. Limit of Liability/Disclaimer of Warranty: While the publisher and the author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor the author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information about our other products and services, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging-in-Publication Data: Clough, Richard Hudson. Construction project management : a practical guide to field construction management / Richard H. Clough, Glenn A. Sears, S. Keoki Sears.—5th ed. p. cm. Includes index. ISBN 978-0-471-74588-4 (hbk. : CD-ROM) 1. Construction industry—Management. 2. Project management. I. Sears, Glenn A. II. Sears, S. Keoki. III. Title. TH438.C62 2008 692’.8—dc22 2007032130Â
  • 12. PrefaceThis book is about Critical Path Method (CPM)-based planning and scheduling as applied to theconstruction industry. The book’s distinguishing feature is the use of one example projectthroughout to demonstrate planning, scheduling, project acceleration, resource management, timecontrol, financial control and the project cost system. The example project is a highway bridge.It has been suggested that a building project might be more appropriate for many readers. We haveseriously considered that suggestion, although the complexity of even a simple building tends toobscure project management fundamentals in logistical detail and diminish the clarity of the book. Thebridge example, although a civil engineering project, typifies the basics of construction by incorporatingcritical aspects of most construction projects: the construction of foundations, concrete work, structuralsteel, and finish work, all of which require labor and equipment supervision, subcontractor management,and material expediting. The entire highway bridge project takes 10 weeks to construct and can becompletely illustrated in 70 distinct activities.This fifth edition has been updated with current labor, material, and equipment pricing and includes acomplete estimate for the highway bridge. Scheduling and management concepts, such as WorkBreakdown Structures (WBS) and the Earned Value Management System (EVMS), are developed in thisedition. An estimate in SI units is included in Appendix B for readers outside the United States.Of particular interest is Chapter 6, which includes discussions of production planning as it affectspersonnel, safety, quality, paperwork, and material control. A site layout drawing shows the location oftemporary buildings, formwork fabrication, material laydown and staging area, fire extinguishers, andfirst aid kits. Much of the information in this chapter is gleaned from years of construction experienceand is unique to this text.For generations Men, Machines, Materials, Methods, and Money have been the five Ms of construction.Efficient usage of these five resources is the essence of construction management. However, in recentyears, an important change in these basic resources has occurred. Women now constitute an importantpart of the construction industry. They occupy responsible positions in the field trades and at all levelsof management. Construction terms like “journeyman,†“foreman,†and“piledriverman†have been used in the industry for literally hundreds of years. Because suchwords are the only ones generally recognized, these words are used in this text but are not meant in anyway to imply gender. At times, the word “he†or “him†is used as a singular pronoun. Suchuse of the masculine gender is done solely for the sake of readability and has no presumption of gender.The authors of this text recognize and applaud the important contribution that women have made andare making to the construction industry.This book teaches a method for capturing, modeling, and viewing the entirety of a construction projectso that it can be effectively planned and managed from start to finish. Consequently, many of theillustrations are quite large and presented on extra-wide pages called tip-ins. Due to productionlimitations, these tip-ins can only be inserted at specific intervals throughout the book rather than at thepoint they are referenced. Where a tip-in is referenced, guidance is provided on where to locate thefigure within the text. In some cases, the tip-ins are located in the chapter following the point wherethey are referenced.This fifth edition represents 37 years of publication and three generations of authors. We trust that thisfully updated edition will continue as a principal reference for today’s professionals and aninstructive guide for tomorrow’s constructors.ÂS. Keoki Sears, London, EnglandGlenn A. Sears, Durango, ColoradoJanuary 2008
  • 13. 1 Construction Practices 1.1 IntroductionThe objective of this book is to present and discuss the management of field construction projects.These projects involve a great deal of time and expense, so close management control is required if theyare to be completed within the established time and cost limitations. The text also develops anddiscusses management techniques directed toward the control of cost, time, resources, and projectfinance during the construction process. Emphasis is placed on practical and applied procedures ofproven efficacy. Examples relate to field construction practices.Effective management of a project also requires a considerable background of general knowledge aboutthe construction industry. The purpose of this chapter is to familiarize the reader with certainfundamentals of construction practice that will be useful for a complete understanding of thediscussions presented in later chapters. 1.2 Construction IndustryIn terms of the dollar value of output produced, the construction industry is the largest singleproduction activity of the U.S. economy. The annual expenditure of approximately $1.2 trillion forconstruction in 2006 accounts for more than 9 percent of the gross national product (GNP). Thus, almost1 of every 10 dollars spent for goods and services in the United States is spent on construction. Theconstruction industry is directly responsible for approximately 6 percent of private employment (or 5percent of total jobs) in the United States, making it one of the nation’s largest employers.Not only does the construction industry touch the lives of virtually everyone on a daily basis; it occupiesa fundamental position in many national economies. This large and pervasive industry is regarded as thebellwether of economic growth in the United States. Periods of national prosperity usually areassociated with high levels of construction activity. One is the natural result of the other.The construction industry is heterogeneous and enormously complex. There are several majorclassifications of construction that differ markedly from one another: housing, nonresidential building,heavy, highway, utility, and industrial. In addition, these construction types are further divided intomany specialties, such as electrical, concrete, excavation, piping, and roofing.Construction work is accomplished by contractors who vary widely in size and specialty. Somecontractors choose to concentrate on a particular task or aspect of the construction project and aretherefore referred to as specialty contractors. Others assume broader responsibility for acomprehensive work package and are referred to as prime contractors. Commonly, prime contractorswill subcontract specific aspects of a project to the specialty contractors, forming a contractual web ofprime contractors and specialty contractors. Within the industry, very large contractors handle annualvolumes in excess of $15 billion; their annual budgets rival the gross national products of many smallcountries. However, the construction industry is typified by small businesses. 1.3 Construction ProjectConstruction projects are intricate, time-consuming undertakings. The total development of a projectnormally consists of several phases requiring a diverse range of specialized services. In progressing frominitial planning to project completion, the typical job passes through successive and distinct stages thatdemand input from such disparate areas as financial organizations, governmental agencies, engineers,architects, lawyers, insurance and surety companies, contractors, material manufacturers and suppliers,and building tradesmen.During the construction process itself, even a structure of modest proportions involves many skills,materials, and literally hundreds of different operations. The assembly process must follow a naturalorder of events that constitutes a complicated pattern of individual time requirements and restrictivesequential relationships among the structure’s many segments.
  • 14. To some degree each construction project is unique—no two jobs are ever exactly the same. In itsspecifics, each structure is tailored to suit its environment, arranged to perform its own particularfunction, and designed to reflect personal tastes and preferences. The vagaries of the construction siteand the possibilities for creative and utilitarian variation of even the most standardized building productcombine to make each construction project a new and different experience. The contractor sets up its“factory†on the site and, to a large extent, custom builds each structure.The construction process is subject to the influence of highly variable and sometimes unpredictablefactors. The construction team, which includes architects, engineers, building tradesmen,subcontractors, material dealers, and others, changes from one job to the next. All the complexitiesinherent in different construction sites—such as subsoil conditions, surface topography, weather,transportation, material supply, utilities and services, local subcontractors, labor conditions, andavailable technologies—are an innate part of construction.Consequently, construction projects are typified by their complexity and diversity and by thenonstandardized nature of their production. The use of factory-made modular units may diminish thisindividuality somewhat, but it is unlikely that field construction will ever be able to adapt completely tothe standardized methods and product uniformity of assembly line production. On the contrary, manymanufacturing processes are moving toward “one-off†produc on and adop ng many of theproject management tools originating in the construction industry. 1.4 Project StagesA construction project proceeds in a rather definite order; the stages of development that follow aretypical. A. Planning and DefinitionOnce an owner has identified the need for a new facility, he or she must define the requirements anddelineate the budgetary constraints. Project definition involves establishing broad project characteristics,such as location, performance criteria, size, configuration, layout, equipment, services, and other ownerrequirements needed to establish the general aspects of the project. Conceptual planning stops short ofdetailed design, although a considerable amount of preliminary architectural or engineering work maybe required. The definition of the work is basically the responsibility of the owner, although a designprofessional may be called in to provide technical assistance and advice. B. DesignThe design phase involves the architectural and engineering design of the entire project. It culminates inthe preparation of final working drawings and specifications for the total construction program. Inpractice, design, procurement, and construction often overlap, with procurement and constructionbeginning on certain segments as soon as the design is completed and drawings and specificationsbecome available. C. Procurement and Construction“Procurement†refers to the ordering, expedi ng, and delivering of key project equipment andmaterials, especially those that may involve long delivery periods. This function may or may not behandled separately from the construction process itself. “Construction†is, of course, the processof physically erecting the project and putting the materials and equipment into place, and this involvesproviding the manpower, construction equipment, materials, supplies, supervision, and managementnecessary to accomplish the work. 1.5 OwnerThe owner, whether public or private, is the instigating party that gets the project financed, designed,and built. Public owners are public bodies of some kind, and range from the federal government downthrough state, county, and municipal entities to a multiplicity of local boards, commissions, andauthorities. Public projects are paid for by appropriations, bonds, or other forms of financing and arebuilt to perform a defined public function. Public owners must proceed in accordance with applicablestatutes and administrative directives pertaining to advertising for bids, bidding procedure, constructioncontracts, contract administration, and other matters relating to the design and construction process.
  • 15. Private owners may be individuals, partnerships, corporations, or various combinations thereof. Mostprivate owners have the structure built for their own use: business, habitation, or otherwise. However,some private owners do not intend to be the end users of the constructed facility; rather, they plan tosell, lease, or rent the completed structure to others. These end users may or may not be known to theowners at the time of construction. 1.6 Architect-EngineerThe architect-engineer, also known as the design professional, is the party or firm that designs theproject. Because such design is architectural or engineering in nature, or often a combination of the two,the term “architect-engineer†is used in this book to refer to the design professional, regardless ofthe applicable specialty or the relationship between the architect-engineer and the owner.The architect-engineer can occupy a variety of positions with respect to the owner for whom the designis undertaken. Many public agencies and large corporate owners maintain their own in-house designcapability. In such instances, the architect-engineer is the design arm of the owner. In the traditionaland most common arrangement, the architect-engineer is a private and independent design firm thataccomplishes the design under contract with the owner. Where the “design-construct†mode ofconstruction is used, the owner contracts with a single party for both design and construction. In suchcases the architect-engineer is a branch of, or is affiliated in some way with, the construction contractor. 1.7 Prime ContractorA prime contractor, also known as a general contractor, is the firm that is in prime contract with theowner for the construction of a project, either in its entirety or for some designated portion thereof. Inthis regard, the owner may choose to use a single prime contract or several separate prime contracts.Under the single-contract system, the owner awards construction of the entire project to one primecontractor. In this situation, the contractor brings together all the diverse elements and inputs of theconstruction process into a single, coordinated effort and assumes full, centralized responsibility for thedelivery of the finished job, constructed in accordance with the contract documents. The primecontractor is fully responsible to the owner for the performance of the subcontractors and other thirdparties to the construction contract.When separate contracts are used, the project is not constructed under the centralized control of asingle prime contractor. Rather, several independent contractors work on the project simultaneously,and each is responsible for a designated portion of the work. Each of the contractors is in contract withthe owner and each functions independently of the others. Hence, each of these contractors is a primecontractor. Responsibility for coordination of these contractors may be undertaken by the owner, thearchitect-engineer, a construction manager, or one of the prime contractors who is paid extra toperform certain overall job management duties. 1.8 Competitive BiddingThe owner selects a prime contractor on the basis of competitive bidding, negotiation, or somecombination of the two. A large proportion of the construction in the United States is done bycontractors that obtain their work in bidding competition with other contractors. The competitivebidding of public projects is often required by law and is standard procedure for public agencies.Essentially all public construction work is done by this method. When bidding a project, the contractorestimates how much the structure will cost using the architect-engineer’s drawings andspecifications as a basis for the calculations. The contractor then adds a reasonable profit to this costand guarantees to do the entire job for the stated price.Bid prices quoted by the bidding contractors most often constitute the principal basis for selection ofthe successful contractor, with the low bidder usually receiving the contract award. Most biddingdocuments stipulate that the work shall be awarded to the “lowest responsible bidder.†This givesthe owner the right to reject the proposal of a bidding contractor if the contractor is judged to beunqualified for some reason. If its bid is selected, the contractor is obligated to complete the work inexchange for the contract amount.Competitive bidding can also be used where the successful contractor is determined on a basis otherthan the estimated cost of the construction. For example, where the contract involves payment of a
  • 16. prescribed fee to the contractor, the amount of the fee is sometimes used as a basis of competitionamong contractors. Construction management services are sometimes obtained by an owner using thefees proposed by the different bidders as the basis for contract award. This is often referred to as a fee-based bid. 1.9 Negotiated ContractsAt times it can be advantageous for an owner to negotiate a contract for its project with a preselectedcontractor or small group of contractors. It is common practice for an owner to forgo the competitivebidding process and to handpick a contractor on the basis of its reputation and overall qualifications todo the job. A contract is negotiated between the owner and the chosen contractor. Clearly, suchcontracts can include any terms and provisions that are mutually agreeable to the parties. Mostnegotiated contracts are of the cost-plus-fee type, a subject that will be developed more fully later. 1.10 Combined Bidding and NegotiationAn owner sometimes will combine elements of both competitive bidding and negotiation. One suchprocess is to have a bid where the competing contractors are required to submit their qualificationsalong with their bids and are encouraged to tender suggestions as to how the cost of the project couldbe reduced. The owner then interviews those contractors whose proposals appear most favorable andnegotiates a contract with one of them. 1.11 SubcontractingThe extent to which a general contractor will subcontract work depends greatly on the nature of theproject and the contractor’s own organization. There are instances where the job is entirelysubcontracted, so the general contractor provides only supervision, job coordination, project billing, andperhaps general site services. At the other end of the spectrum are those projects where the generalcontractor does no subcontracting, choosing to do the work entirely with its own forces. Customarily,however, the prime contractor will perform the basic project operations and will subcontract theremainder to various specialty contractors. Types of work with which the prime contractor isinexperienced or for which it is not properly equipped are usually subcontracted, since qualifiedsubcontractors generally are able to perform their specialty faster and less expensively than the generalcontractor. In addition, many construction specialties have specific licensing, bonding, and insurancerequirements that would be costly for the general contractor to secure for intermittent use.When the prime contractor engages a specialty firm to accomplish a particular portion of the project,the two parties enter into a contract called a subcontract. No contractual relationship is therebyestablished between the owner and the subcontractor. When a general contractor sublets a portion ofits work to a subcontractor, the prime contractor remains responsible under its contract with the ownerfor any negligent or faulty performance by the subcontractor. The prime contractor assumes completeresponsibility to the owner for the direction and accomplishment of the total work. An important part ofthis responsibility is the coordination and supervision of the subcontractors. 1.12 Design-Bid-ConstructTraditionally, field construction is not begun until the architect-engineer has completed and finalized thedesign. This sequence is still predominant in the industry and is referred to as the design-bid-constructprocedure. While completing one step before initiating the next may be acceptable to owners on someprojects, it will be unacceptably slow to other owners. A number of financial considerations dictate theearliest possible completion date for many construction projects. It is possible to reduce the totaldesign-construction time required for some projects by starting the construction before completedesign of the entire project has been accomplished. 1.13 Fast Tracking“Fast tracking†refers to the overlapping accomplishment of project design and construc on. Asthe design of progressive phases of the work is finalized, these work packages are put under contract, aprocess also commonly referred to as phased construction. Early phases of the project are underconstruction while later stages are still on the drawing boards. This procedure of overlapping the designand construction can appreciably reduce the total time required to achieve project completion. Forobvious reasons, fast tracking and phased construction sometimes can offer attractive advantages tothe owner and also can be the source of severe coordination problems.
  • 17. 1.14 Construction Contract ServicesA myriad of contract forms and types are available to the owner for accomplishing its constructionneeds, and all of them call for defined services to be provided under contract to the owner. The scopeand nature of such services can be made to include almost anything the owner wishes. The selection ofthe proper contract form appropriate to the situation is an important decision for the owner and is onedeserving of careful consideration and consultation.The construction contract can be made to include construction, design-construct, or constructionmanagement services, each of which is discussed in the next three sections. 1.15 Construction ServicesA large proportion of construction contracts provide that the general contractor have responsibility tothe owner only for accomplishment of the field construction. Under such an arrangement, thecontractor is completely removed from the design process and has no input into it. Its obligation to theowner is limited to constructing the project in full accordance with the contract terms.Where the contractor provides construction services only, the usual arrangement is for a privatearchitect-engineer firm to perform the design in contract with the owner. Under this arrangement, thedesign professional acts essentially as an independent design contractor during the design phase and asan agent of the owner during construction operations. The architect-engineer acts as a professionalintermediary between the owner and contractor and often represents the owner in matters ofconstruction contract administration. Under such contractual arrangements, the owner, architect-engineer, and contractor play narrowly defined roles, and the contractor is basically in an adversarialrelationship with the other two. 1.16 Design-ConstructWhen the owner contracts with a single firm for both design and construction and possibly procurementservices, this is referred to as a design-construct project. This form of contract is usually negotiated,although occasionally it is competitively bid. Usually the contractor has its own design section witharchitects and engineers as company employees. In other cases, however, the architect-engineer can bea contractor’s corporate affiliate or subsidiary, or the contractor can enter into a joint venturearrangement with an independent architect-engineer firm for a given project or contract.The team concept is basic to design-construct. The owner, designer, and builder work cooperatively inthe total development of the project. The contractor provides substantial input into the design processon matters pertaining to materials, construction methods, cost estimates, and construction timeschedules. In recent years, owners have shown increasing acceptance and usage of this concept, largelydue to the economies of cost and time that can be realized by melding the two functions of design andconstruction. Injecting contractor experience and expertise into the design process offers the possibilityof achieving cost savings for the owner. Because fast tracking is possible under a design-constructcontract, the owner may well have the beneficial use of the structure considerably before it would haveunder the more traditional design-bid-construct arrangement.A “turnkey†contract is similar to a design-construct contract. The difference lies in the greaterrange of responsibilities that the contractor undertakes on behalf of the owner under a turnkeyarrangement. For example, a turnkey contract often includes such services as land selection andacquisition, project financing, project equipage procurement, and leasing of the completed facility. 1.17 Construction ManagementThe term “construction management†is applied to the provision of professional managementservices to the owner of a construction project with the objective of achieving high quality at minimumcost. Such services may encompass only a defined portion of the construction program, such as fieldconstruction, or they may include total project responsibility. The objective of this approach is to treatproject planning, design, and construction as integrated tasks within a construction system. Whereconstruction management is used, a nonadversarial team is created consisting of the owner,construction manager, architect-engineer, and contractor. The project participants, by working togetherfrom project inception to project completion, attempt to serve the owner’s best interests inoptimum fashion. By striking a balance between construction cost, project quality, and completion
  • 18. schedule, the management team strives to produce for the owner a project of maximum value withinthe most economical time frame. Construction management does not include design or constructionservices per se, but involves management direction and control over defined design and constructionactivities.Construction management services are performed for the owner for a stipulated fee by design firms,contractors, and professional construction managers. Such services range from merely coordinatingcontractors during the construction phase to broad-scale responsibilities over project planning anddesign, project organization, design document review, construction scheduling, value engineering, fieldcost monitoring, and other management services. Selection of the construction manager by the owner issometimes accomplished by competitive bidding using both fee and qualifications as bases for contractawards. Usually, however, the construction management arrangement is considered to be aprofessional services contract and is negotiated. These contracts normally provide for a fixed fee plusreimbursement of management costs. 1.18 Fixed-Sum ContractA fixed-sum contract requires the contractor to complete a defined package of work in exchange for asum of money fixed by the contract. Should the actual cost of the work exceed this figure, thecontractor absorbs the loss. The owner is obligated to make only such total payment as is stipulated inthe contractual agreement. A fixed-sum contract may be either lump sum or unit price.With a lump-sum contract, the contractor agrees to complete a stipulated package of work in exchangefor a single lump sum of money. Use of this form of contract is obviously limited to those constructionprojects where both the nature and quantity of each work type can be accurately and completelydetermined before the contract sum is set.A unit-price contract requires the contractor to perform certain well-defined items of work inaccordance with a schedule of fixed prices for each unit of work put into place. The total sum of moneypaid to the contractor for each work item is determined by multiplying the contract unit price by thenumber of units actually done on the job. The contractor is obligated to perform the quantities of workrequired in the field at the quoted unit prices, whether the final quantities are greater or less than thoseinitially estimated by the architect-engineer. This is subject to any contract provision forredetermination of unit prices when substantial quantity variations occur. Unit-price contracts areespecially useful on projects where the nature of the work is well defined but the quantities of workcannot be accurately forecast in advance of construction. 1.19 Cost-Plus-Fee ContractsCost-plus-fee contracts provide that the owner reimburse the contractor for all construction costs andpay a fee for its services. How the contractor’s fee is determined is stipulated in the contract, and anumber of different procedures are used in this regard. Commonly used are provisions that the fee shallbe a stipulated percentage of the total direct cost of construction or that the fee shall be a fixed sum.Incentive clauses are sometimes included that give the contractor an inducement to complete the job asefficiently and expeditiously as possible through the application of bonus and penalty variations to thecontractor’s basic fee. A guaranteed maximum cost is frequently included in cost-plus contracts.Under this form, the contractor agrees that it will construct the total project in full accordance with thecontract documents and that the cost to the owner will not exceed some total price. 1.20 Work-by-Force AccountThe owner may elect to act as its own constructor rather than have the work done by a professionalcontractor. If the structure is being built for the owner’s own use, this method of construction iscalled the force-account system. In such a situation, the owner may accomplish the work with its ownforces and provide the supervision, materials, and equipment itself. Or the owner may choose tosubcontract the entire project, assuming the responsibility of coordinating and supervising the work ofthe subcontractors. Because public projects generally must be contracted out on a competitive-bid basis,force-account work by a public agency usually is limited to maintenance, repair, or cases of emergency.Force-account work can also be coupled with other contracting methods discussed earlier in this chapterto handle specific aspects of the project that cannot be clearly defined or have undergone significantchange. In such cases, the contractor performs the associated work at the direction of the owner andbills for these services on a time and materials basis.
  • 19. Over the years, many studies have revealed that most owners cannot perform field construction worknearly as well or as inexpensively as professional contractors. The reason for these findings is obvious:The contractor is intimately familiar with materials, equipment, construction labor, and methods. Itmaintains a force of competent supervisors and workers and is equipped to do the job. Only when theowner conducts a steady and appreciable volume of construction and applies the latest fieldmanagement techniques is it economically feasible for it to carry out its own construction operations. 1.21 Turnkey and BOT ContractsFixed-sum, cost-plus-fee, and work-by-force account contracting methods all require owners tocoordinate initial planning, design, construction, and facilities start-up. These tasks distract the ownersfrom their core business responsibilities. For this reason, some owners also contract theseresponsibilities to the contractor. Turnkey and build-operate-transfer (BOT) contracts provide a vehiclefor complete project delivery by the contractor.In a turnkey arrangement, the owner provides the facility design requirements to the contractor, whichdesigns and constructs the facility under a single contract. The single contract eliminates the need forowner coordination and reduces project duration. Upon completion, the key to the project is turnedover to the owner and the contract is closed out.BOT contracts are an extension of the turnkey method. The contractor designs, constructs, operates,and maintains the facility for a predetermined concessionary period. In most cases, the contractorreceives no payment from the owner for these services but retains all or a portion of the revenuesearned by the project during the concession. This contracting method generally is used for bridges,highways, power plants, and similar projects that generate a long-term revenue stream. At the end ofthe concession period, ownership transfers from the contractor to the owner. 1.22 Speculative ConstructionWhen owners build structures for sale or lease to other parties, they engage in what is commonlyreferred to as speculative construction. Housing and commercial properties like shopping centers andwarehousing facilities are common examples of such construction. In tract housing, for instance,“merchant†builders develop land and build housing for sale to the general public. This is a form ofspeculative construction through which developers act as their own prime contractors. They builddwelling units on their own account and employ sales forces to market their products. In muchspeculative housing, contractors build for unknown buyers. In commercial applications, however,construction does not normally proceed until suitable sale or lease arrangements have been made.Leases are usually necessary so that the developers can arrange their financing. It also enables them tobuild to the lessee’s individual specifications. Most speculative builders function more as land orcommercial developers than as contractors, choosing to subcontract all or most of the actualconstruction work. 1.23 Management during the Design PhaseProject cost and time control actually begin during the design phase. In the initial design stages,estimates such as annual cost to the owner and total life-cycle costs of the facility are made. Technicaljob standards are weighed against cost, function, maintenance, and appearance with the objective ofminimizing the full cost of constructing, operating, and maintaining the new facilities over their usefullife. As the design develops, construction methods and material alternatives are subjected to valueanalysis as a rational means of optimizing the entire construction process in terms of cost and time. Costbudgets—ranging from preliminary to final—are prepared as the design approaches completion.Time control during the design stage is directed toward minimizing construction time consistent withproject quality and total cost. The delivery times of materials and project equipment are checked.Where long delivery periods are involved, the design is changed or procurement is initiated as soon asthe design has progressed sufficiently to allow detailed purchasing specifications to be drawn.Construction methods are chosen whose cost characteristics are favorable and for which adequate laborand construction equipment will be available as needed. A preliminary project time schedule usually isprepared as the design progresses. 1.24 Management of Field Construction
  • 20. Discussions up to this point have demonstrated that owners have the option of using many differentprocedures to get their structures built. Regardless of the variability of these procedures, however, oneparty assumes management responsibility for the field construction process. Depending on the methodsused by the owner, this party may be the owner, the architect-engineer, a construction manager, or ageneral contractor.The management of field construction customarily is done on an individual project basis, with a projectmanager being made responsible for all aspects of the construction. For large projects, a field officeusually is established directly on the job site for the use of the project manager and his staff. A goodworking relationship with a variety of outside persons and organizations, such as architects, engineers,owners, subcontractors, material and equipment dealers, labor unions, and regulatory agencies, is animportant part of guiding a job through to its conclusion. Field project management is directed towardpulling together all the diverse elements necessary to complete the project satisfactorily. Managementprocedures presented later will, in general, be discussed only as they apply to field construction,although they are equally applicable to the entire project, from concept to start-up. 1.25 Project ManagerThe project manager organizes, plans, schedules, and controls the field work and is responsible forgetting the project completed within the time and cost limitations. He acts as the focal point for allfacets of the project and brings together the efforts of all organizations having input into theconstruction process. He coordinates matters relevant to the project and expedites project operationsby dealing directly with the individuals and organizations involved. In any such situation where eventsprogress rapidly and decisions must be consistent and informed, the specific leadership of one person isneeded. Because he has the overall responsibility, the project manager must have broad authority overall elements of the project. The nature of construction is such that the manager often must take actionquickly on his own initiative, and it is necessary that he be empowered to do so. To be effective, he musthave full control of the job and be the one voice that speaks for the project. Project management is afunction of executive leadership and provides the cohesive force that binds together the several diverseelements into a team effort for project completion.Large projects normally will have a full-time project manager who is a member of the firm’s topmanagement or who reports to a senior executive of the company. The manager may have a projectteam to assist him, or he may be supported by a central office functional group. When smaller contractsare involved, a single individual may act as project manager for several jobs simultaneously. Animportant aspect of a project manager’s position is that his duties normally are separate from thoseof field supervision. The day-to-day direction of field operations is handled by a site supervisor or fieldsuperintendent whose duties involve working with the foremen, coordinating the subcontractors,directing construction operations, and keeping the work progressing smoothly and on schedule. The factis that construction project authority is a partnership effort between the project manager and the fieldsuperintendent, who work very closely together. Nevertheless, centralized authority is necessary for theproper conduct of a construction project, and the project manager is the central figure. 1.26 Project Manager QualificationsThe effective project manager must possess four essential attributes. First, he must have a considerablebackground of practical construction experience so that he is thoroughly familiar with the workings andintricacies of the industry. Without such a basic grounding in construction fundamentals, the projectmanager would be completely unprepared to carry out his responsibilities.Second, the project manager must have, or have available to him, persons with expertise andexperience in the application of specialized management techniques to the planning, scheduling, andcontrol of construction operations. These procedures have been developed specifically for application toconstruction projects and are those discussed in this book. Because much of the management system isusually computer based, the project manager must have access to adequate computer support services.Third, the project manager must have the capacity to step back from the complex details of dailyconstruction operations and look into the future—planning for upcoming activities, checking materialdeliveries, determining manpower and training requirements, identifying possible changes to the work,and other future problem areas.
  • 21. Fourth, the project manager must have the personality and insight that will enable him to workharmoniously with other people, often under very strained and trying circumstances. The manager,after all, cannot accomplish everything through his efforts alone. He must work with and through peoplein the performance of his duties. Doing this requires an appreciation and understanding of the humanfactor. Without this, his other attributes, however commendable, will be of limited effectiveness.
  • 22. 2 Management System 2.1 Need for Project ManagementIn most construction contracts, the contractor is given only one opportunity to set its price (the bid).From that point on, profits are determined by the project manager’s ability to save money throughbetter planning of daily operations and the skill to make good decisions. If a project is to be constructedwithin its established budget and time schedule, close management control of field operations is anecessity. Project conditions such as technical complexity, importance of timely completion, resourcelimitations, and substantial costs put great emphasis on the planning, scheduling, and control ofconstruction operations. Unfortunately, the construction process, once set into motion, is not a self-regulating mechanism and requires expert guidance if events are to conform to plans.It must be remembered that projects are one-time and largely unique efforts of limited time durationthat involve work of a nonstandardized and variable nature. Field construction work can be affectedprofoundly by events that are difficult, if not impossible, to anticipate. Under such uncertain and shiftingconditions, field construction costs and time requirements are changing constantly and can seriouslydeteriorate with little or no advance warning. The presence of uncertainty in construction does notsuggest that planning is impossible but rather that it will assume a monumental role in the success orfailure of the project. The greater the level of uncertainty in the project, the greater the need forexhaustive project planning and skilled and unremitting management effort.Under most competitively bid, fixed-sum contracts calling for construction services only, the generalcontractor exercises management control over construction operations. Self-interest is the essentialmotivation in such cases, the contractor being obligated by contract to meet a prescribed completiondate and to finish the project for a stipulated sum. The surest way for the contractor to achieve its ownobjectives, and those of the owner in the bargain, is by applying some system of project management.Serving the best interests of the owner is the primary emphasis of project control under other forms ofcontracts. Field management under design-construct, construction management, and many cost-pluscontracts is directed principally toward providing the owner with professional advisory andmanagement services to best achieve the owner’s objectives. 2.2 Project Management CharacteristicsIn its most common context, the term “management†relates to the planning, organizing, directing,and controlling of a business enterprise. Business management is essentially a continuing and internalactivity involving that company’s own personnel, finances, property, and other resources.Construction project management, however, applies to a given project, the various phases of whichusually are accomplished by different organizations. Therefore, the management of a constructionproject is not so much a process of managing the internal affairs of a single company as it is one ofcoordinating and regulating all of the elements needed to accomplish the job at hand. Thus, the typicalproject manager must work extensively with organizations other than his own. In such circumstances,much of his authority is conferred by contractual terms or power of agency and is therefore less directthan that of the usual business manager. Project management is accomplished largely through thepersonnel of different employers working closely together. 2.3 Discussion ViewpointAs mentioned previously, the responsibility for field construction management rests with differentparties, depending on owner preference and the nature of the contracting procedure. Whether theowner, architect-engineer, general contractor, or a construction manager performs such duties is verymuch a matter of context. The basics of the pertinent management procedures are essentially the same,however, regardless of the implementing party. Nevertheless, to show detailed workings and examplesof such management methods, it is necessary to present the material from the specific viewpoint of oneof these parties. Thus, where the nature of the discussion requires such designation, the treatment ofmanagement methods herein will be from the particular viewpoint of the general contractor. 2.4 Management Procedures
  • 23. Field construction has little in common with the assembly-line production of standardized products.Standard costs, time-and-motion studies, process flowcharts, and line-of-balance techniques—alltraditional management devices used by the manufacturing industries—have not lent themselves wellto general construction applications. Historically, construction project management has been arudimentary and largely intuitive process, aided by the useful but inadequate bar chart (see Section5.29.)Over the years, however, new scientific management concepts have been developed and applied.Application of these principles to construction has resulted in the development of techniques for themanagement control of construction cost, time, resources, and project finance, treating the entireconstruction process as a unified system. Comprehensive management control is applied from inceptionto completion of construction operations.Field project management starts with the onset of construction, at which point a comprehensiveconstruction budget and detailed time schedule of operations are prepared. These constitute theaccepted cost and time goals used as a blueprint for the actual construction process. After the projecthas begun, monitoring systems are established that measure the actual costs and progress of the workat periodic intervals. The reporting system provides progress information that is measured against theprogrammed targets. Comparison of field expense and progress with the established plan quicklydetects exceptions that must receive prompt management attention. Data from the system can be usedto make corrected forecasts of costs and time to complete the work.The process just described is often called a management-by-exception procedure. When applied to agiven project, it emphasizes the prompt and explicit identification of deviations from an established planor norm. Reports that highlight exceptions from the standard enable the manager to recognize quicklythose project areas requiring attention. As long as an item of work is progressing in accordance with theplan, no action is needed, but there are always plenty of problem areas that do require attention.Management-by-exception devices are useful, and this book emphasizes their application.In addition to cost and time, the field management system is necessarily concerned with themanagement of job resources and with project financial control. Resources in this context refer tomaterials, labor, construction equipment, and subcontractors. Resource management is primarily aprocess of the advance recognition of project needs, scheduling and expediting of the resourcesrequired, and adjusting the demands where necessary. Project financial control involves theresponsibility of the project manager for the total cash flow generated by the construction work and theterms of the contract.As indicated by the preceding discussion, there are several different aspects of a project control system.Each of these major management topics is treated separately in the chapters that follow. It must berecognized, however, that these aspects are highly interrelated segments of a total project managementprocess. 2.5 Time and Cost ManagementProject time and cost management are based on time and cost schedules developed for the project andan information system that will provide data for comparing expected with actual performance. Theinformation or monitor system measures, evaluates, and reports job progress, comparing it with theplanned performance, which keeps the project manager apprised of the nature and extent of anydeviation. When deviations do occur, the manager takes whatever action is considered feasible andeffective to correct the situation. Costs and time can quickly get out of hand on construction projectswhere production conditions are volatile. Job monitoring must detect such aberrations quickly. Cost andtime control information must be timely with little delay between field work and management review ofperformance. This timely information gives the project manager a chance to evaluate alternatives andtake corrective action while an opportunity still exists to rectify problem areas.In a sense, all management efforts are directed toward cost control because expedient completion ofsafe and high-quality projects represents both construction savings for the contractor and beneficialusage for the owner. In practice, however, time and cost management are spoken of and applied asseparate, although interrelated, procedures. One aspect of this separation is the difference in jobbreakdown structure used for time and cost control purposes. The distinctive character of the two
  • 24. procedures requires that the project be divided into two different sets of elements: project componentsfor time control and work classifications for cost control.The realities of a field project make the strict control of every detail unattainable in a practical sense.Consequently, it must be recognized that the time and cost management methods discussed in thisbook are imperfect procedures, affording results of reasonable accuracy and to managers whose powersto control are far from absolute. Project management procedures offer no panacea for constructionproblems. They provide no magic answers, and the management information generated is no betterthan the quality of the input data. Nevertheless, a reasonably good basis is established for informeddecision making. 2.6 Planning and SchedulingPlanning, the first step in the process of construction time control, is discussed at length in Chapter 4.On the basis of a detailed study of job requirements, planning establishes what is to be done, how it isto be done, and the order in which it will proceed. The planning function is accomplished by dividing theproject into many components or time-consuming steps, called activities, and establishing the sequencein which they will be performed. An example of an activity might be “Install boiler†or “Set barjoists.†The results of project planning are shown graphically in the form of a network diagram. Thisdiagram can be drawn using either of two different graphical notation systems, “precedence†or“arrow.†Precedence nota on is emphasized herein and is used throughout for discussionpurposes. The arrow convention is presented in Appendix D.A detailed time study of the planning network is then conducted, with adjustments to the plan beingmade as necessary to meet the project completion date. Some selective shortening of key constructionactivities may be in order at this point. Manpower and construction equipment requirements areevaluated for the individual job activities, with adjustments being made to minimize unbalanced orconflicting demands. On the basis of these studies, the contractor establishes a calendar-date scheduleof the anticipated start and finish times for each activity. The resulting time schedule, subject to periodicrevision and correction during construction, is the essential basis for the day-to-day time control of theproject. Such a schedule serves as an exceptionally effective early-warning device for detecting whenand where the project is falling behind schedule and the impact that these delays will have on theproject as a whole. The several facets of project scheduling are the topics of Chapters 5, 7, and 9. 2.7 CPM ProcedureThe planning and scheduling of construction projects normally uses a network-based managementprocedure referred to as the Critical Path Method (CPM). CPM was developed especially to provide aneffective and workable procedure for planning and scheduling construction operations. Widely used bythe construction industry, and frequently a contract requirement, CPM involves a definite body ofmanagement procedures and is the basis for the planning and scheduling methods discussed in thisbook.The heart of CPM is a graphical job plan that shows all the construction activities necessary for jobcompletion and the order in which they will be done. This graphical network portrays, in simple anddirect form, the complex time relationships and constraints among the various segments of a project. Ithas the tremendous advantage of easily accommodating modifications, refinements, and corrections. Itprovides the project manager with 12 invaluable time control information and devices:1. Concise information regarding the planned sequence of construction operations2. A means to predict with reasonable accuracy the time required for overall project completion and thetimes to reach intermediate construction goals (commonly called milestones)3. Proposed start and finish calendar dates for project activities consistent with the construction plan4. Identification of those “critical†ac vi es whose e pedient e ecu on is crucial to mely projectcompletion5. A guide for reducing project time6. A basis for scheduling subcontractors and material deliveries to the job site
  • 25. 7. A basis for balanced scheduling of manpower and construction equipment on the project8. The rapid evaluation of time requirements for alternative construction methods9. An effective model for numerically computing project status10. An essential vehicle for progress reporting, recording, and analysis11. A basis for evaluating the time effects of construction changes and delays12. A language for the communication of plans, processes, and goals for the entire project team 2.8 Time Monitoring and ControlWhen field operations begin, the order in which the project proceeds is in accordance with an approvedjob plan. During the construction period, advancement of the work is monitored by measuring andreporting field progress at regular intervals. These data are analyzed and time-control measures aretaken as appropriate to keep the work progressing on schedule.Progress measurement for time-control purposes is an approximate process and is based ondetermining the time status of each individual job activity. Progress normally is measured by notingthose activities that have been completed and estimating the remaining time required to completethose in process. When compared with the latest planned schedule, these data give the manager animmediate indication of the time status of each job activity. Because activities seldom start or finishexactly as scheduled, the field information also serves as the basis for occasional updates that yieldrevised project completion dates and corrected time schedules for the construction yet to be done. Theworkings of project time control are discussed in Chapter 9. 2.9 Project Cost SystemThe project cost system is concerned with the control of expenses on current projects and the gatheringof production information for use in estimating the cost of future work. The application of cost controlsto a construction project actually begins when the costs are estimated initially. It is then that the projectbudget is established. This is the budget used by the project manager for cost-control purposes duringfield construction.If there is to be an opportunity for genuine cost control, it must be possible to detect cost overrunspromptly by making frequent comparisons between actual and budgeted expenses of production duringthe construction process. In addition, the actual costs must be determined in sufficient detail to enableproject management to locate the source of cost overruns. During construction, cost accountingmethods are applied to obtain the actual production rates and costs as they occur. Specifically designedsummary reports are prepared periodically to pinpoint work areas where costs are exceeding thebudget. This management-by-exception cost system immediately identifies for the project managerwhere production costs are unsatisfactory and management action is needed. If the project managertakes timely and suitable corrective measures, cost overruns often can be minimized and futureexpenditures brought into line with budget estimates. In addition to maintaining a continuous check onproduction costs for cost-control purposes, the project cost system yields valuable information neededfor estimating future construction work. Average production rates and unit costs are obtained fromcompleted projects and maintained in permanent and easily accessible databases. These records of pastcost experience are a valuable resource to the estimator when new projects are being estimated.For both cost-control and estimating purposes, a construction project must be broken down intostandardized and categorized building blocks, often called cost codes, work types, or Work BreakdownStructure (WBS) elements. Hence, cost information gathered during the construction phase must betracked using the same cost codes that will be used in producing future estimates. This allows thehistorical cost information to be recalled and assembled in a variety of different ways to producereasonable cost estimates of future projects. Some examples of work types might be “footingconcrete, place (cy)†or “structural steel, erect (ton).†These classi ca ons are used throughouta company’s cost system. Each work type is assigned a unique and permanent cost code numberthat is used consistently by all company personnel and that does not change from project to project.Chapter 10 presents a detailed treatment of a project cost system.
  • 26. 2.10 Estimating the ProjectWhen the project design has been finalized, a complete and detailed cost estimate is prepared. Thecontractor uses this estimate for bidding and subsequent cost-control purposes. With cost-plus andconstruction management contracts, a similar estimate is compiled, essentially for the owner’s cost-control purposes during construction. The final estimate is based on a detailed quantity takeoff that is acompilation of the total amounts of elementary work classifications required. The costs of labor,construction equipment, and materials are computed on the basis of the work quantities involved.Subcontract amounts are obtained from bids submitted by subcontractors to the general contractor.Taxes, overhead, and surety bonds are added as required.Of all the costs involved in the construction process, those of labor and construction equipment are themost difficult to estimate and control. Fundamentally, the estimating of such costs is based onproduction rates. A production rate can be expressed as hours of labor or equipment time required toaccomplish a unit amount of a given work type. An example of this is the number of labor hoursrequired to erect a ton of structural steel. Production rates also can be expressed as the number of unitsof a work type that can be done per unit of time, such as per hour. An example of such a production rateis the number of cubic yards of excavation that a power shovel can perform in one hour. For quick andconvenient application, production rates frequently are converted to costs per unit of work. The sourceof production rates and unit costs is the company’s cost accounting system. When the cost estimatehas been completed, the project control budget is prepared. This schedule of costs is the standard towhich the actual costs of production are compared during field operations. Chapter 3 discussesestimating project costs and preparing the project budget. 2.11 Project Cost AccountingProject cost accounting is the process of obtaining actual production rates and unit costs from ongoingprojects. This system provides the basic information for project cost control and for estimating newwork. Because of the uncertain nature of labor and equipment costs, these two items of expense aresubjected to detailed and frequent analysis during the construction period. They are the main emphasisof a construction cost accounting system. Basic elements of this system are labor and equipment workhours, hourly expense rates for labor and equipment, and the quantity of work accomplished during thespecified period. These data are analyzed and periodic cost reports are produced. These cost reportscompare budgeted with actual costs of production for each work type and are used for cost-controlpurposes. These reports not only enable comparisons to be made between budgeted and actualexpenses as the work proceeds, but also provide a basis for making forecasts of the final project cost.They also record production rates and unit costs for future use in estimating.Cost accounting, unlike financial accounting, is not conducted entirely in terms of cost. To establishproduction rates and unit costs, work quantities and hours of labor and equipment usage must also bedetermined. Consequently, accurately measuring and reporting work quantities completed, and theassociated hours of labor and equipment expended in the field, are integral parts of a cost accountingsystem. 2.12 Resource ManagementThe term “resources†refers to manpower, construc on equipment, materials, and subcontractors.These resources totally control job progress and must be managed carefully during the constructionprocess. Schedules of future resource needs are prepared and positive steps taken to assure thatadequate job support will be available as required. Favorable material deliveries require skilledattention to procurement, shop drawing review and approval, expediting, and quality control. Laborcrews and construction equipment must be scheduled and arranged. Subcontractors must be keptinformed of the overall job schedule and given advance notice when their services are required, andtheir work must be coordinated with the total project effort.Resource management involves other aspects as well. Job schedules occasionally must be adjusted toreduce the daily demand for certain resources to more practical levels. Impracticable bunching of jobresources must be leveled to a smoother and more attainable demand profile. Resource managementand its procedures are discussed in Chapter 8. 2.13 Project Financial Control
  • 27. For management purposes, a construction project is treated essentially as a separate and autonomouseffort requiring resources and input from a variety of sources. For income and expense, profit or loss,and general financial accounting purposes, each project is handled separately and individually. Thesignificance of this method is that the project manager generally has responsibility for the control ofproject financial matters. Of concern here are considerations ranging from total project cash flow toeveryday matters of contract administration. Monthly pay requests, an estimated schedule of paymentsby owner, project cash forecasts, changes to the contract, and disbursements to material dealers andsubcontractors are all examples of project financial matters subject to management control procedures.Methods and procedures applicable to project financial management are discussed in Chapter 11. 2.14 Automating Project Management TasksThe management and control of project time, cost, resources, and finance by the contractor during thefield construction process require that the project manager originate, manipulate, summarize, andinterpret large volumes of numerical data. In order to generate such information and apply it inoptimum fashion, the project manager customarily relies on computer software to provide a wide rangeof data processing and to automate routine tasks. Project managers must react quickly to changingconditions, and their decisions must be made with the secure knowledge that they are acting on thebasis of adequate, accurate, and current intelligence. Modern management software can greatly assistin making this information available and in providing information for the evaluation of alternate coursesof action. With most of the time-consuming data manipulation automated, the project manager candevote more time to problem solving and developing more profitable approaches.However, because of the continuous emergence of new machines and new software support, thisvolume makes no effort to discuss specific hardware configurations or the workings of software incurrent usage for project management purposes. Rather, emphasis is placed on sources of information,the management significance of the data generated by the computer, and how these data are applied tothe control of a construction project. 2.15 Manual MethodsThe preceding discussion of computer applications to job management is not meant to imply thatmanual methods have no place in the system. The project manager may rely on hand methods forlimited portions of a project and to carry out computations for making quick checks, to determine theeffect of changes, or to study a specialized portion of the work.Even when the calculations are automated, the project manager must understand the computationalprocedures that are an innate part of the techniques applied. The manager’s intimate familiaritywith the workings of the procedures will provide an intuitive feel and grasp of a project that cannot beobtained in any other way. Because manual methods are useful in their own right and a thoroughunderstanding of the computational methods involved with the computer generation of managementdata is crucial to the proper application of project control methods, this book discusses in step-by-stepfashion the manual calculation of the several kinds of construction management tools. 2.16 Discussion FormatSeveral different management procedures are presented in the chapters that follow. In an attempt toprovide a sense of continuity while going from one topic to another, an Example Project is used as acontinuing basis for the succeeding series of discussions. In order to acquaint the reader both with thedetailed workings of certain procedures and the broad applicability of others, examples of constructionwork ranging from modest to comprehensive in extent are needed. To provide examples of both macro-and micro-work packages, a large-scale project consisting of several separate segments or subprojectsserves as the Example Project.Two segments of the Example Project are used for illustrative purposes where a considerable scope ofconstruction activity is needed to present a given management application. An individual subproject isadopted where the level of detail is such that the procedure is best explained by using an example oflimited proportions. Several project management actions are presented subsequently using segments ofthe Example Project as the basis for discussion. Each major management responsibility is the subject ofa different chapter. The changes, modifications, revisions, and corrections that are discussed in any onechapter are limited to that chapter and do not carry forward to the next. For purposes of clarity, the
  • 28. methods presented in each chapter are discussed independently of one another and are applied, in turn,to the original, unchanged Example Project. 2.17 Example ProjectThe Example Project involves the construction of an earth dam and some appurtenant structures. Thecompleted project will serve a number of purposes, including flood control, irrigation, and recreation.The dam will be constructed across an existing river, the flow of which is highly variable with the season.A permanent reservoir will be formed, the extent of which will vary considerably during the year. Thejob site covers a considerable geographical area that is undeveloped and unpopulated.Figure 2.1Example ProjectThe design of the Example Project has been completed, and working drawings and specifications arenow available. The owner is a public agency, and the project will be competitively bid by prequalifiedcontractors. Accordingly, project field management will be carried out by the successful primecontractor. Public notice of the receipt of proposals has been given as required by law, biddingdocuments are available, and the bidding process is about to begin. The entire Example Project will beawarded by a single contract to the low-bidding prime contractor. Because of the nature of the workinvolved, unit-price bidding will be used. The contract will contain a time requirement for completion ofthe construction, and liquidated damages will apply in the event of late contract completion.
  • 29. The flowchart in Figure 2.1 depicts the overall Example Project and the principal operations that will becovered by the construction contract. This figure shows the major aspects of the work, the generalsequence of which will be as described. One of the first operations must be the diversion of the riveraway from the dam site area. The borrow areas from which the earth dam material is to be obtained arelocated some distance from the dam site and must be stripped of surface soil and vegetation. Haul roadsbetween the dam and the borrow areas must be developed, keeping grades to a minimum andproviding hard, smooth rolling surfaces. After the river diversion, borrow development, and haul roadshave been accomplished, construction of the dam itself can proceed.While this preparatory work and the dam are under way, other segments of the Example Project canprogress simultaneously. A concrete emergency spillway is to be built at a location removed from themain dam itself. The new reservoir area necessitates the relocation of five miles of existing natural gaspipeline, and a new bridge must be built where an adjoining highway crosses a reservoir inlet. Theclosure and removal of the river diversion will be the final major construction operation. The highwaybridge and the pipeline relocation will be used to illustrate several construction managementapplications.
  • 30. 3 Project Cost Estimating 3.1 Project Cost SystemDuring the design phase of a construction project, the project costs are continuously approximated andreviewed following each design change to ensure that they will not exceed the owner’s budget. Thisworking budget is generally referred to as the engineer’s or architect’s estimate. Upon designcompletion, the field cost-control system is initiated by making a final, detailed cost estimate of theentire work. The construction contractor or another party who will be directly involved in the fieldoperations normally prepares this “contractor’s es mate.†The contractor’s es mate isthen reduced to a working construction budget and forms the basis of the construction cost controlsystem.During the construction process, cost accounting methods (discussed in Chapter 10) are used to retrieveactual construction expenses from ongoing construction operations. This information is then used forcost control purposes on the current project and for estimating the cost of future projects. Additionally,the cost system provides considerable information pertinent to project financial control (discussed inChapter 11). This chapter discusses cost-estimating procedures and how the final project budget isobtained. 3.2 Preliminary Cost EstimatesPreliminary estimates of future construction expenditures, made during the project planning and designphases, are necessarily approximate because they are compiled before the project is completely defined.Making such conceptual estimates is an art quite different from determining the final detailed estimateof construction costs.Fundamentally, all conceptual price estimates are based on some system of gross unit costs obtainedfrom previous construction work. These unit costs are extrapolated forward in time to reflect currentmarket conditions, project location, and the particular character of the job presently underconsideration. Some of the methods commonly used to prepare preliminary estimates include:Cost per Function EstimateThis analysis is based on the estimated expenditure per unit of use, such as cost per patient, student,seat, or car space. Construction expense may also be approximated as the average outlay per unit of aplant’s manufacturing or production capacity. These parameters are generally used as a method ofquickly defining facilities costs at the inception of a project when only raw marketing information isknown, such as the number of patients that a planned hospital will hold. This broad method ofdeveloping costs can also provide a powerful check on more detailed estimates once they have beengenerated.Index Number EstimateThis method involves estimating the price of a proposed structure through updating the constructioncost of a similar existing facility. It is done by multiplying the original construction cost of the existingstructure by a national price index that has been adjusted to local conditions, such as weather, laborexpense, materials costs, transportation, and site location. A price index is the ratio of presentconstruction cost to the original construction outlay for the type of structure involved. Many forms ofprice indexes are available in various trade publications.Unit Area Cost EstimateThis method of estimating facilities costs is an approximate cost obtained by using an estimated pricefor each unit of gross floor area. The method is used frequently in building and residential homeconstruction. It provides an accurate approximation of costs for structures that are standardized or havea large sampling of historical cost information from similar structures. This type of estimate is used oftenin the industry to compare the relative worth of various facilities.
  • 31. Unit Volume Cost EstimateThis estimate is based on an approximated expenditure for each unit of the total volume enclosed. Thisestimating method works well in defining the costs of warehouses and industrial facilities.Panel Unit Cost EstimateThis analysis is based on unit costs per square unit area of floors, unit length of perimeter walls,partition walls, and unit roof area. Generally this form of estimating is used to improve the precedingestimates once additional detailed information about the facility is known.Parameter Cost EstimateThis estimate involves unit costs, called parameter costs, for each of several different buildingcomponents or systems. The prices of site work, foundations, floors, exterior walls, interior walls,structure, roof, doors, glazed openings, plumbing, heating and ventilating, electrical, and other items aredetermined separately by the use of estimated parameter costs. These unit expenses can be based ondimensions or quantities of the components themselves or on the common measure of building squarefootage.Partial Takeoff EstimateThis analysis uses quantities of major work items taken from partially completed design documents.These are priced using estimated unit prices for each work item taken off. During the design stage, thistype of estimate is considered to provide the most accurate preliminary costs. Yet the feasibility of thismethod is highly dependent on the availability of completed design documents. Generally this estimatecannot be made until well into the design process. Hence it is often used to refine the previouslydiscussed estimating methods. 3.3 Final Cost EstimateThe final cost estimate of a project is prepared when finalized working drawings and specifications areavailable. This detailed estimate of construction expense is based on a complete and detailed survey ofwork quantities required to accomplish the work. The process involves the identification, compilation,and analysis of the many items of cost that will enter into the construction process. Such estimating,which is done before the work is actually performed, requires careful and detailed study of the designdocuments, together with an intimate knowledge of the prices, availability, and characteristics ofmaterials, construction equipment, and labor.It must be recognized that even the final construction estimate is of limited accuracy and that it bearslittle resemblance to the advance determination of the production costs of mass-produced goods. Byvirtue of standardized conditions and close plant control, a manufacturer can arrive at the futureexpense of a unit of production with considerable precision. Construction estimating, by comparison, isa relatively crude process. The absence of any appreciable standardization together with a myriad ofunique site and project conditions make the advance computation of exact construction expenditures amatter more of accident than design. Nevertheless, a skilled and experienced estimator, using costaccounting information gleaned from previous construction work of a similar nature, can do a crediblejob of predicting construction disbursements despite the project imponderables normally involved. Thecharacter or location of a construction project sometimes presents unique problems, but some basicprinciples for which there is precedent almost always apply.When pricing a job of some size, there will undoubtedly be more than one person involved in thequantity takeoff and pricing phases. The term “estimator†is used herein to refer to whoever maybe involved with the estimating procedure being discussed.There are probably as many different estimating procedures as there are estimators. In any processinvolving such a large number of intricate manipulations, variations naturally result. The form of thedata generated, the sequential order followed, the nature of the elementary work classifications used,the mode of applying costs—all are subject to considerable diversity. Individual estimators develop andmold procedures to fit their own context and to suit their own preferences. In this volume, rather than
  • 32. attempt any detailed discussion of estimating methods, only the general aspects of constructionestimating are presented. 3.4 Highway BridgeTo illustrate the workings of several major aspects of project management, including the cost system, itwill be useful to have a construction job large enough to be meaningful, but not so large that its sheersize will obscure the basic objectives. The highway bridge, a segment of the Example Project, has beenselected to serve as the basis for discussion of a project estimating and cost system. Although thehighway bridge would be estimated and bid as a part of the total Example Project, it has been isolatedhere for demonstration purposes.The highway bridge to be erected is a single-span vehicular bridge that will cross a small ravine. Thebridge is of a deck-girder type and is of composite steel-concrete construction. Figures 3.1 and 3.2 showthe bridge profile and a transverse section. The two abutments are of reinforced concrete, eachconsisting of a breast wall and two wing walls. Each abutment rests on a heavy concrete footingsupported by twenty-eight 40-foot-long H-section steel piles. The 10-inch-thick reinforced concretepaving slab is supported by seven W363150 steel floor girders. A steel guardrail is required to extend thelength of the bridge along each side. All exposed structural concrete is to be given a rubbed finish, andall of the metal surfaces are to be painted.Figure 3.1Highway bridge, profile
  • 33. Figure 3.2Highway bridge, transverse sectionThe owner of the Example Project is a public agency, and the entire work, including the highway bridge,is to be competitively bid on the basis of unit prices. The final estimate and working job budget that willbe obtained in the sections that follow are those prepared by the prime contractor for its bidding andcost-control purposes. The design has been completed, and bidding documents, including finalizeddrawings and specifications, are in the hands of the bidding contractors.Figure 3.3, the proposal form to be used for the bidding of the highway bridge, shows 12 bid items andthe engineer’s quantity estimate of each. The bidding contractor fills in the Unit Price, column 5, andEstimated Amount, column 6, after the estimating process has been completed (see Figure 3.9).Figure 3.3Highway bridge, bid form 3.5 Quantity SurveyThe first step in preparing the final price estimate of the highway bridge is the preparation of a quantitysurvey. This survey is simply a detailed compilation of the nature and quantity of each work typerequired. Taking off quantities is done in substantial detail, with the bridge being divided into many
  • 34. different work types or classifications. Such a takeoff is made where unit-price bidding is involved, eventhough the architect-engineer customarily provides estimated quantities of each bid item with thebidding documents. A basic reason for making a quantity survey for unit-price bidding is that most biditems cannot be priced without breaking the work down into smaller subdivisions. Another reason isthat the architect-engineer’s quantity estimates, such as those given in column 4 of Figure 3.3, arespecifically stated to be approximations only. Making the quantity survey also provides the estimatorwith the intimate familiarity of job requirements so vital to realistic project pricing.The estimator takes the dimensions and numbers of units of each work type from the design drawings,enters them on quantity sheets, and extends them into totals. The summarized results of the quantitysurvey on the highway bridge are shown in Figure 3.4. This figure does not show any quantities forpainting. This is because the prime contractor normally limits its takeoff to work items it might carry outwith its own forces. The contractor intends to subcontract the highway bridge painting and thus did nottake off quantities of this specialized work category.Figure 3.4Highway bridge, work quantitiesA comparison of Figures 3.3 and 3.4 will show that the architect-engineer’s estimate and thecontractor’s takeoff are the same insofar as the quantities of the individual bid items are concerned.Quantities estimated by the architect-engineer and by the bidding contractors do not always check; attimes, the differences can be substantial. However, for such a relatively precise work package as thehighway bridge, it is reasonable to assume that agreement of the quantity figures will be relatively closein all cases. 3.6 Management InputEarly in the estimating process, certainly before the work is priced, a number of important managementdecisions must be made concerning the project and how construction operations are to be conducted.When the job is being priced, the estimator must exert every effort to price each work type asrealistically as possible. To do this, major decisions must be made concerning project organization, the
  • 35. major construction methods to be used, the sequential order of operations, and what constructionequipment will be utilized. These four considerations require management attention and are ofconsuming importance to the bidding process.A new project cannot be intelligently priced until some major management determinations have beenmade concerning the conduct of the work. It is clear, therefore, that there must be some regular andusual procedure for the estimator to precipitate such decision making. An effective means of doing thisis to have a prebid meeting of knowledgeable company personnel who have the authority to makedecisions and binding commitments. If at all possible, the group should include the proposed projectmanager and the field superintendent. At this meeting, details of the job are discussed, jobrequirements are reviewed, alternative choices are evaluated, and decisions are made. 3.7 Field SupervisionBefore pricing the job, it is always good practice to identify the top supervisors who will be assigned to it.The reason for this is not only to establish specific salary requirements, but also to recognize that mostjob supervisors do better in terms of construction costs on some portions of a project than on others.Some superintendents are known to be very good at getting a job out of the ground but do not performas well during later phases of the construction. A given supervisor may be experienced with one type ofequipment but not with another. The pricing of a project must take into account the special abilities ofkey field personnel.The matching of field supervisory talents with the demands of a particular project is one of the mostimportant management actions. The best management system in the world cannot overcome thehandicap of poor supervision. The importance of an experienced, skilled, and energetic field supervisoryteam cannot be overemphasized. 3.8 Construction MethodsSeldom is there a job operation that can be performed in only one manner. Preferably, the choice ofmethod is made after evaluating the time and cost characteristics of the feasible alternatives. This is notto say that a detailed cost study must be undertaken before making decisions concerning alternativeways of doing every construction operation. Frequently, convention, together with experience andequipment availability, prescribes most of these choices to the estimator. However, there are timeswhen these operational choices are sufficiently important to justify conducting a detailed comparativestudy.Many examples of alternative construction methods can be cited, such as procedures to be followed inunderpinning an adjacent structure, how best to brace an excavation, what method of scaffolding to use,and how to dewater the site. All of these involve judgments of major import to the conduct of the work.The proper evaluation of alternatives can require considerable time and extensive engineering studies.It is obvious, however, that the principal construction procedures to be used must be identified beforethe job can be intelligently priced. 3.9 General Time ScheduleWhen a new project is being estimated, it is necessary to devise a general plan and operational timeschedule. Estimators customarily do this during the takeoff stage, although often in an informal andalmost subconscious way. Small jobs may require little investigation in this regard, but larger projectsdeserve more than a cursory time study. Time is of prime importance on all projects, in part becausemost contracts impose a required project completion date on the contractor.An approximate construction schedule is also important for project pricing purposes. Many of the joboverhead expenses are directly related to the duration of the construction period. When a calendar ofwork operations is prepared, the time periods required for each of the major job parts can beestablished, as well as the kinds of weather to be anticipated. This calendar provides invaluableinformation to the estimator concerning equipment and labor productivity, cold weather operations,necessity of multiple shifts or overtime, and other such matters.Devising a general job plan and time schedule must start with a study of project requirements. Thisstudy will enable an approximation to be made of the times necessary to accomplish each of the majorjob segments. Next, the sequence in which these segments must proceed is established. The result is a
  • 36. bar chart—a series of bars plotted against a horizontal time scale showing the completion date of theoverall project and the approximate calendar times during which the various parts of the job willproceed. Each bar represents the beginning, duration, and completion of some designated segment ofthe total project. Together, the bars make up a time schedule for the entire job. If the bar chartcompletion date is not consonant with owner requirements, the estimator will have to rework the jobplan.Although the bar chart has had the advantage of some general planning, it cannot be regarded as theequivalent of a detailed network analysis. However, the development of a CPM job schedule requiresconsiderable time and effort. Consequently, on a competitively bid job, a contractor usually will notmake a full-scale time study until it has been proclaimed the successful bidder and awarded the contract.This practical fact emphasizes the need for making a reasonably accurate general time schedule of theproject during the bidding period.Figure 3.5 shows the general time schedule for the highway bridge. It indicates that a constructionperiod of about 15 weeks will be necessary. Subsequent refinement and development of the job planwill undoubtedly disclose imperfections. Nevertheless, if the development of Figure 3.5 has receivedadequate consideration, it will serve as an acceptably accurate job picture for pricing purposes.Considerable job planning has already occurred to develop the job schedule to this stage.Figure 3.5Highway bridge, general time schedule 3.10 Construction EquipmentProjects that are of the highway, heavy, or utility category normally require considerable amounts ofconstruction equipment for their accomplishment. A substantial proportion of the total cost of theseprojects is associated with such equipment; however, equipment expenses vary greatly with the typeand size of the individual unit. Commensurately, the detailed pricing of equipment on the bridge projectcannot proceed very far until equipment selection decisions have been made in fairly specific terms. It isessential that the estimator be able to price the job with reasonable assurance that he is doing so on thebasis of the equipment types that actually will be used during construction operations.To illustrate the workings of equipment decisions, consider the equipment commitments made for thehighway bridge. A decision to use transit-mix concrete obtained from a commercial concern obviatesthe need for a field concrete plant. For pouring concrete, placing structural steel, and driving steel piles,a 50-ton crane equipped with an 80-foot boom will be used. A 7,200-foot-pound double-acting hammerand a 900-cubic-foot-per-minute portable air compressor with hose and connections will be used for thepile driving. A tractor with a low-boy trailer and a 25-ton crane will be needed for transport andassembly of the pile driving rig. A crawler tractor with bulldozer blade will do the unclassified excavation,and a 1-cubic-yard backhoe will be used for the structural excavation. A flatbed truck, trowelingmachine, and concrete saw will complete the list of larger equipment needs. Smaller equipment such asconcrete vibrators and assorted small tools will be provided as needed and priced elsewhere. These arethe kinds of advance equipment decisions that must be made during the estimating stage. 3.11 Summary SheetsAfter the quantity survey has been completed and decisions concerning methods and equipment havebeen made, the total quantities are transferred from the quantity sheets to summary sheets for pricing
  • 37. purposes. On lump-sum projects, it is standard practice to transfer all quantities of work pertaining to asingle construction classification to the same summary sheet before pricing them. As an example,concrete quantities and prices would appear on a concrete summary sheet. Similar summary sheets areprepared for the other work classifications, such as excavation, concrete forms, masonry, and carpentry.On a unit-price job like the highway bridge, each summary sheet lists the work types necessary toaccomplish the total quantity of a single bid item and may include several different classifications ofwork. Figure 3.6 is the summary sheet for Bid Item No. 6, Concrete, abutments, on the highway bridge.The summary sheets for the other 11 bid items are presented in Appendix A. A metric version of all theestimating figures is shown in Appendix B. In Figure 3.6 and in the summary sheets in Appendices A andB, an identifying number designates each work type. These are the contractor’s standard costaccount numbers that are basic to the workings of its cost accounting system. When the takeoff is beingcompiled for a new project, the work is broken down into the standard elementary classificationsestablished by this system. Each of these standard work types bears a unique cost account number. Thecoding system is discussed further in Chapter 10.Figure 3.6Highway bridge, bid-item summary sheet
  • 38. 3.12 Material CostsIt is customary for the contractor to solicit and receive specific price quotations for most of the materialsrequired by the job being priced. Exceptions to this generality are stock items such as plyform, nails, andlumber, which the contractor purchases in large quantities and of which a running inventory ismaintained. Written quotations for special job materials are desirable so that such importantconsiderations as prices, freight charges, taxes, delivery schedules, and guarantees are explicitlyunderstood. Most material suppliers tender their quotations on printed forms that include stipulationspertaining to terms of payment and other considerations. For the highway bridge project, the contractorwill receive during the bidding period written price quotations from material dealers covering specificjob materials, such as transit-mix concrete, structural and reinforcing steel, steel pilings, and guardrails.Consequently, if the quantity survey has been prepared with precision, materials usually can beaccurately priced.
  • 39. When material costs are entered on the summary sheets, they must all have a common basis, forexample, delivered to the job site and without sales tax. Prices as entered will ordinarily include freight,drayage, storage, and inspection. It is common practice to enter material prices without tax, adding thisas a lump-sum amount on the final recap sheet (see Section 3.25).It is not unusual for the owner to provide certain materials to the contractor for use on the project,although this does not occur on the highway bridge. In such a case, contractors need not add thismaterial price into their estimates. However, all other charges associated with the material, such ashandling and installation expense, must be included. 3.13 Labor CostsThe real challenge in pricing construction work is determining labor and equipment expenditures. Theseare the categories of construction expense that are inherently variable and the most difficult to estimateaccurately. To do an acceptable job of establishing these outlays, the estimator must make a completeand thorough job analysis, maintain a comprehensive library of unit costs and production rates frompast projects, and obtain advance decisions regarding how construction operations will be conducted.Contractors differ widely in how they estimate labor costs. Some choose to include all elements of laborexpense in a single hourly rate. Others evaluate direct labor cost separately from indirect cost. Somecontractors compute regular and overtime labor costs separately, while others combine scheduledovertime with straight time to arrive at an average hourly rate. Some evaluate labor charges usingproduction rates; others use labor unit costs. There are usually good reasons for a contractor toevaluate its labor expense as it does, and there certainly is no single correct method that must befollowed. The procedures described in this chapter are commonly used and are reasonablyrepresentative of general practice.Basic to the determination of the labor cost associated with any work category is the production rate.Figure 3.6, in which the labor expense of pouring the abutment concrete on the bridge project isdetermined, is a good example of a production rate. The figure shows that a placement rate of 8.75cubic yards of concrete per hour is used as the production rate for the prescribed concrete crew. Thedirect labor cost to pour the entire 280 cubic yards of abutment concrete is obtained by multiplying thetime required to pour the concrete (280 ÷ 8.75 = 32 hours) by the direct hourly wage rate of the entirecrew ($284.00), giving a direct labor cost of $9,088. To this must be added indirect labor costs of $3,181,giving a total labor charge of $12,269 to accomplish this particular item of work. The distinctionbetween direct and indirect labor expenses is discussed in Section 3.14.The most reliable source of labor productivity information is obtained from cost accounting reportscompiled from completed projects. Labor cost information is also available from a wide variety ofpublished sources. While information of this type can be very useful at times, it must be emphasizedthat labor productivity differs from one geographical location to another and varies with season andmany other job factors. Properly maintained labor records from recent jobs completed in the locale ofthe project being estimated reflect, to the maximum extent possible, the effect of local and seasonalconditions. 3.14 Indirect Labor CostsDirect labor cost is determined from the workers’ basic wage rates, that is, the hourly rates used forpayroll purposes. Indirect labor costs are those expenses that are additions to the basic hourly rates andthat are paid by the employer. Indirect labor expense involves various forms of payroll taxes, insurance,and a wide variety of employee fringe benefits. Employer contribution to social security, unemploymentinsurance, workers’ compensation insurance, and contractor’s public liability and propertydamage insurance are all based on payrolls. Employers in the construction industry typically provide forvarious kinds of fringe benefits, such as pension plans, health and welfare funds, employee insurance,paid vacations, and apprenticeship programs. The charge for these benefits customarily is based ondirect payroll costs. Premiums for workers’ compensation insurance and most fringe benefits differconsiderably from one craft to another.Indirect labor costs are substantial in amount, often constituting a 35 to 55 percent addition to directpayroll expenses. Exactly when and how indirect labor costs are added into a project estimate isunimportant so long as it is done. For estimating purposes, total labor outlay can be computed in one
  • 40. operation by using hourly labor rates, which include both direct and indirect costs. However, thisprocedure may not interrelate well with labor cost accounting methods. For this reason, direct andindirect labor charges often are computed separately when job prices are being estimated. Onecommonly used scheme is to add a percentage allowance for indirect costs to the total direct laborexpense, either for the entire project or for each major work category. Because of the appreciablevariation in indirect costs from one classification of labor to another, it may be preferable to computeindirect labor costs at the same time that direct labor expense is obtained for a given work type. This isthe method followed in Figure 3.6 and Appendices A and B. 3.15 Labor Unit CostsDirect labor cost was computed in Section 3.13 for a given work type using hourly crew payroll expensetogether with the work quantity and appropriate production rate. A widely used alternative to thisprocedure involves the use of “labor unit costs.†A labor unit cost is the direct labor expense perunit of production of a work type. To illustrate, reference is again made to concrete placing in Figure 3.6.This figure shows that 32 hours of crew time are required to place 280 cubic yards of abutment concreteat a total direct labor outlay of $9,088. Dividing $9,088 by 280 yields $32.46. This value of $32.46 is alabor unit cost; it is the average direct labor charge of pouring 1 cubic yard of abutment concrete. Thus,the direct labor cost of pouring the abutment concrete could have been computed in Figure 3.6 simplyby multiplying the total of 280 cubic yards of abutment concrete by the labor unit expense of $32.46.The same value of $9,088 would have been obtained.The use of labor unit costs in estimating practice usually is limited to the determination of direct laborexpense. Once the direct labor cost is computed for a given work category, the applicable indirect laborcost is determined by multiplying the direct labor expense by the appropriate percentage figure. Laborunit prices are used in Figure 3.6 to compute the direct labor costs of fabricating the abutment formsand for placing and stripping the abutment forms.When labor unit costs are being used, care must be exercised to see that they are based on theappropriate levels of work productivity and the proper wage rates. Also, estimators must be verycircumspect when using labor unit costs that they have not developed themselves. For the same workitems, different estimators will include different expenses in their labor unit costs. It is never advisableto use a labor unit cost derived from another source without knowing exactly what categories ofexpense it does and does not include. 3.16 Equipment Cost EstimatingUnfortunately, the term “equipment†does not have a unique connotation in the constructionindustry. A common usage of the word refers to scaffolding, hoists, power shovels, paving machines,and other such items used by contractors to accomplish the work. However, the term“equipment†also is used with reference to various kinds of mechanical and electrical furnishingsthat become a part of the finished project, such as boilers, escalators, electric motors, and hospitalsterilizers. In this text, “equipment†refers only to the contractor’s construction equipage. Theterm “materials†will be construed to include all items that become a part of the nished structure,including the electrical and mechanical plant.Equipment costs, like those of labor, are difficult to evaluate and price with precision. Equipmentaccounts for a substantial proportion of the total construction expense of most engineering projects butis less significant for buildings. When the nature of the work requires major items of equipment, such asearth-moving machines, concrete plants, and truck cranes, detailed studies of the associated costs mustbe made. Expenses associated with minor equipment items, such as power tools, concrete vibrators,and concrete buggies, are not normally subjected to detailed study. A standard expense allowance foreach such item required is included, usually based on the duration it will be required on the job. Thecost of small tools, wheelbarrows, water hoses, extension cords, and other such items are covered by alump-sum allowance sometimes obtained as a small percentage of the total labor cost of the project.To estimate the expense of major equipment items as realistically as possible, early managementdecisions must be made concerning the equipment sizes and types required and the manner in whichthe necessary units will be provided to the project. A scheme sometimes used when the duration of theconstruction period will be about equal to the service life of the equipment is to purchase all new orrenovated equipment for the project and sell it at the cessation of construction activities. The difference
  • 41. between the purchase price and the estimated salvage value is entered into the job estimate as a lump-sum equipment expenditure.Equipment often is rented or leased. Rental can be especially advantageous when the job site is farremoved geographically from the contractor’s other operations, for satisfying temporary peakdemand, or for providing specialized or seldom used equipment. Leasing is a common and widely usedmeans of acquiring construction equipment and may be a desirable alternative to equipment ownership.Leasing can free the contractor’s funds, thus improving its working capital position. Under certaincircumstances, lease payments compare favorably with ownership expense. Many leases provide that,at the expiration of the lease period, the contractor will have a purchase option if it has continuing needof the machine and if it is worth the additional payment. Lease agreements for construction equipmentnormally extend for periods of one year or more, whereas renting is usually of shorter term. Chargesassociated with the rental or lease of equipment items are figured into the job by applying the lease orrental rates to the time periods that the equipment will be needed on the project.Where purchase and sale, rental, or lease is involved, equipment operating expenses must also becomputed and included in the project estimate. Operating costs include charges such as fuel, oil, grease,filters, repairs and parts, tire replacement and repairs, maintenance labor, and supplies. There is somedifference of opinion about whether the wages of equipment operators should be included in theequipment operating cost. Some contractors prefer to regard the labor associated with equipmentoperation as a labor rather than an equipment cost. Others include the labor as a part of equipmentoperating expense. Logically, it would seem preferable to treat equipment operating labor like any otherlabor cost rather than include it with equipment operating expense. For purposes of discussion herein,equipment operators’ wages are treated as a labor cost and are not included as an equipmentexpense.When bidding work with rented or leased equipment, contractors have access to equal equipment costsand cannot leverage this often substantial expense as a competitive advantage in pricing the job. This isone of the reasons contractors commonly elect to own their own equipment. Under thesecircumstances, equipment charges are customarily expressed as the sum of ownership expense andoperating costs. Ownership expenses are those of a fixed nature and include depreciation, interest oninvestment or financing charges, taxes, insurance, and storage. Operating expenses have been definedpreviously. 3.17 Equipment ExpenseAs described in Section 3.13, direct labor costs are computed from work quantities by combining a laborproduction rate with the applicable hourly wage scales. Most equipment costs are calculated in muchthe same fashion except, of course, that equipment production rates and equipment hourly costs mustbe used. The hourly wage rates of various labor categories are immediately determinable, usually fromapplicable labor contracts, prescribed prevailing wage rates, or established area practice. This is not truefor equipment. Contractors must establish their own equipment hourly rates as well as their equipmentproduction rates. For most items of operating equipment ownership, lease or rental expense iscombined with operating costs to form an estimated total charge per operating hour. Power shovels,tractor scrapers, and trenchers are examples of equipment whose expenses are usually expressed interms of hourly rates.There are some classes of construction equipment where it is more appropriate to express costs interms of units other than operating hours. The charge for commercial prefabricated concrete formsmight be better spread over an estimated number of reusages. Items such as towers and scaffolding arerequired at the job site on a continuous basis during particular phases of the work, and operating hourshave no significance in such cases. Costs in terms time units, such as calendar months, are moreappropriate for such equipment items. The charges for some classes of production equipment arefrequently expressed in terms of expense per unit of material produced. Portland cement concrete-mixing plants, asphalt paving plants, and aggregate plants are familiar instances of this. Move-in,erection, dismantling, and move-out expenses, also called mobilization and demobilization costs, areentirely independent of equipment operating time and production and are not, therefore, included inequipment hourly rates. These equipment expenses are separately computed for inclusion in theestimate. Mobilization of the pile driving rig for the highway bridge is an example of this type ofequipment cost and is shown in Bid Item No. 4 of Appendices A and B.
  • 42. 3.18 Determination of Equipment Cost RatesThe determination of cost rates for the equipment items to be used on a project being estimated is animportant matter and requires considerable time and effort. It must be remembered that estimators arealways working in the future and that the equipment rates they use in their estimates are their bestapproximations of what such costs will be when the project actually is being built.The standard way in which future equipment cost is determined is through the use of historicalequipment cost records as contained in a contractor’s equipment accounting system. The source ofownership and operating cost data for a specific piece of equipment is its ledger account. An importantpart of a contractor’s general accounting system is the equipment accounts where actual ownershipand operating expenses are recorded as they are incurred. A separate account often is set up for eachmajor piece of equipment. This account serves to maintain a detailed and cumulative record of the useof, and all expenses chargeable to, that equipment item. All expenditures associated with that piece ofequipment, regardless of their nature or the project involved, are charged to that account. Theseexpenses include depreciation, investment costs, operating outlays, repairs, parts, overhauls, andpainting. A cumulative record of that equipment item’s usage in the field is also maintained. Thesedata constitute a basic resource for reducing ownership and operating expense to a total equipmentcost rate. The sum of ownership and operating expense expressed as a cost per unit of time (operatinghour, week, month) often is referred to either as the budget rate or the internal rental rate of anequipment item. This latter term refers to the usual construction accounting practice where equipmenttime on the project during construction is charged against the job at that rate. The term “internalrental rate†indicates that pro t and company overhead are excluded and must therefore be addedto the project estimate.The preceding discussion assumes that equipment accounting is done on an individual machine basis.However, contractors vary somewhat in how they maintain their equipment accounts, some preferringto keep equipment costs by categories of equipment rather than by individual units. These firms use asingle account for all equipment items of a given size and type and compute an average budget ratebased on the composite experience with all of the units included. Thus, the same expense rate is appliedfor any unit of a given equipment type regardless of differences in age or condition. Because the actualcosts and productivity of individual units can vary substantially, working with individual equipment itemswould seem to have merit and is the basis for the discussions herein.There are many external sources of information concerning ownership and operating costs of a widerange of construction equipment. Manufacturers, equipment dealers, and a large assortment ofpublications offer such data. It must be realized, however, that these are typical or average figures andthat they must be adjusted to reflect contractor experience and methods and to accommodate thespecific circumstances of the project being estimated. Climate, altitude, weather, job location andconditions, operator skill, field supervision, and other factors can and do have a profound influence onequipment expense. When a new piece of equipment is procured for which there is no cost history,equipment expense must be estimated using available sources of reliable information.In the case of the highway bridge, reference to Figure 3.6 shows the budget rate for the 50-ton crane tobe $105 per operating hour. This does not include the wages of the operator, the expense of which isincluded in labor cost. 3.19 Equipment Production RatesIn addition to equipment cost, equipment production rates also are often needed for the computationof equipment expense in a construction estimate. Paralleling the case of labor, applying equipmenthourly expenses and production rates to job quantities enables the estimator to compute totalequipment charges for the project. Equipment unit costs also can be determined. These are equipmentcosts per unit of production. Equipment production rates, like those of labor, are subject to considerablevariation and are influenced by a host of job-site conditions. In addition, some equipment productionrates must be computed using specific job conditions, such as haul distances, grades, and rollingresistance. Estimators must consider and evaluate these factors when they are pricing a new project.There are several sources of equipment production information. Probably the most reliable are costaccounting records from past projects. Advice from the equipment operators themselves can be veryuseful at times. If a new piece of equipment is involved with which there has been no prior experience,
  • 43. production information provided by the equipment manufacturer or dealer can be of assistance. Thereare many rules of thumb and many published sources of information concerning average equipmentproduction rates. Stopwatch spot checks made to obtain the productivity of specific equipment items onpast projects can be of value. In this regard, it should be mentioned that production rates of labor andequipment used for estimating purposes should be average figures taken over a period of time. Daily jobproduction tends to be variable, and this is a hazard when using spot checks. Job cost accountingrecords produce good time average values while a spot check may unknowingly catch production at ahigh or low point.Several equipment production rates are needed for pricing the highway bridge. One such instance is thetime rate at which the steel pilings can be driven. Reference to Bid Item No. 4 of Appendix A shows thatpast company experience indicates a probable driving rate of 70 lineal feet per hour. The hourlyequipment expense for the crane, air compressor, pile hammer, and leads totals $179.00 per hour.Using a total project pile footage of 2,240 lineal feet, the production rate and hourly equipment expenseis used to compute a total equipment cost of $5,728. Equipment unit costs are computed used just likethose of labor. Using pile driving as an example, dividing the hourly equipment rate of $179.00 by theproduction rate of 70 lineal feet per hour yields an equipment unit cost of $2.56, which is the equipmentcharge per lineal foot of pile driven. 3.20 Bids from SubcontractorIf the prime contractor intends to subcontract portions of the project to specialty contractors, thecompilation and analysis of subcontractor bids is an important aspect of making up the final projectestimate. Bids from subcontractors sometimes contain qualifications or stipulate that the generalcontractor is to be responsible for providing the subcontractor with certain job-site services, such ashoisting, electricity and water, storage facilities for materials, and many others. Before estimators canidentify the low subcontractor bid (subbid) for any particular item of work, they must analyze each bidreceived to determine exactly what each such proposal includes and does not include. The checking ofsubbids can be a considerable chore when substantial portions of the project are to be sublet.On the highway bridge, the general contractor has made an advance decision that the painting will besubcontracted. Painting is a specialty area for which the general contractor is ill equipped and has hadno past field experience. When such a decision is made, the contractor does not compile the cost ofdoing the work with its own forces. Rather, the lowest subcontract bid received from a responsiblesubcontractor will be included with the contractor’s other expenses. The lowest acceptable paintingsubcontract bid received was $8,550 and will cover all such services as required by the project drawingsand specifications. This is shown by Bid Item No. 12 of Appendices A and B.The advance decision to subcontract the painting does not necessarily mean that the general contractorwill perform all of the other work with its own forces. Other specialty areas of the bridge also may besubcontracted, depending on a number of circumstances. In this regard, the contractor may specificallyrequest subbids from selected subcontractors, or it may merely await receipt of such bids thatsubcontractors voluntarily submit. In any event, the contractor must compile its own cost of doing thework involved and normally will be interested only in those subbids whose amounts are less than itsown estimated direct cost.When the general contractor receives a subbid whose amount is less than its own estimated directoutlay for doing the same work, it cannot accept such a subbid until consideration is given to severalfactors. Has the contractor had past experience with that subcontractor, and can it be expected to carryout its work properly? Does the subcontractor have a history of reliability and financial stability? Is thesubcontractor experienced and equipped to do the type of work involved? Does the company have agood safety record? The general contractor must remember that it is completely responsible by contractwith the owner for all subcontracted work as well as that performed by its own forces.In compiling its bid for the bridge, the prime contractor received a subbid for Bid Item No. 8, Steel,reinforcing. Subcontract bids for reinforcing steel often include only the cost of labor. However, in thiscase the subbid includes the prices of all materials and labor. The general contractor estimated its owndirect expense of providing and placing reinforcing steel for the bridge to be $81,045, as shown in BidItem No. 8a of Appendices A and B. The subbid received for the same items was for $66,240, lowenough to merit serious consideration. The general contractor has worked with this subcontractor
  • 44. before and found the company to be honest, reliable, safe, and of good reputation. It is a complete bidand does not require the general contractor to provide the subcontractor with specific job-site services.The use of this subbid by the general contractor rather than its own estimated direct cost will reduce thecontractor’s bid by a significant amount. Consequently, the prime contractor decides to use thereinforcing steel subbid in the final compilation of its proposal to the owner, as illustrated by Bid Item 8bof Appendices A and B. At this point, it should be noted that the bid item summary sheets have nowbeen completed. From the price information contained in these summary sheets, the contractor willprepare its working project budget (see Section 3.26) if it becomes the successful bidder. At the moment,however, the estimating process must continue in order to obtain the necessary 12 bid unit prices. 3.21 Project OverheadOverhead or indirect expenses are outlays that are incurred in achieving project completion but that donot apply directly to any specific work item. Two kinds of overhead pertain to a contractor’soperations: project overhead and office overhead, which is discussed in the next section. Projectoverhead, also referred to as job overhead or field overhead, pertains to indirect field expenses that arechargeable directly to the project. Some contractors figure their job overhead outlay as a percentage ofthe total direct job cost; common values for the job overhead allowance range from 5 to 15 percent ormore.The use of percentages when computing field overhead is not generally considered to be goodestimating practice because different projects can and do have widely varying job overheadrequirements. The only reliable way to arrive at an accurate estimate of project overhead is to make adetailed analysis of the particular demands of that project. It is standard estimating procedure to listand price each item of indirect expense on a separate overhead sheet. Figure 3.7 is the project overheadsheet for the bridge project cost estimate. The job overhead amount of $69,868.40 was compiled usingan estimated project duration of 15 weeks (from Section 3.9).Figure 3.7Highway bridge, overhead estimate
  • 45. 3.22 Home Office OverheadHome office overhead includes general company expenses such as office rent, office insurance, heat,electricity, office supplies, furniture, telephone, legal costs, donations, advertising, office travel,association dues, and office salaries. The total of this overhead expense usually ranges from 2 to 8percent of a contractor’s annual business volume. An allowance for such indirect expense must beincluded in the cost estimate of each new project.Home office overhead is made up of charges that are incurred in support of the overall companyconstruction program and that cannot be charged to any specific project. For this reason, home officeoverhead is normally included in the job estimate as a percentage of the total estimated projectexpense. The allowance for office overhead can be added as a separate line item in the cost estimate, ora suitable “markup†percentage can be applied, or a fee can be established that includes bothhome office overhead and profit. 3.23 MarkupOn competitively bid projects, markup or margin is added at the close of the estimating process and isan allowance for profit plus possibly other items, such as office overhead and contingency. Regardingcontingency as a separate component of markup is a matter of management philosophy. The profitincluded in a job bid represents the minimum acceptable return on the contractor’s investment.Return on investment is a function of risk, and greater risk calls for a greater profit allowance in theproposal. Whether recognition of risk is in the form of a higher profit percentage or the inclusion of acontingency allowance seems to be a matter of personal preference.Markup, which may vary from 5 percent to more than 20 percent of the estimated project cost,represents the contractor’s considered appraisal of a whole series of imponderables that may
  • 46. influence its chances of being the low bidder and of its making a reasonable profit if it is. Many factorsmust be considered in deciding a markup figure, and each can have an influence on the figure chosen.The size of the project and its complexity, its location, provisions of the contract documents, thecontractor’s evaluation of the risks and difficulties inherent in the work, the competition, thecontractor’s desire for the work, the identity of the owner and/or the architect-engineer, and otherintangibles can have a bearing on how a contractor marks up a particular job.The contractor is required to bid under a form of contract that has been specifically written to protectthe owner. In an attempt to afford the owner, and often the architect-engineer, protection againstliabilities and claims that may arise from the construction process, the drafters of contract documentsoften incorporate a great deal of boilerplate, including disclaimers of one sort or another. The writers ofcontract documents sometimes force the contractor to assume liability for all conceivable contingencies,some of which are not subject to its control and which are not rightfully its responsibility. For example,some contracts may include provisions that absolve the owner from all claims for damages arising fromproject delay, even those caused through its own fault or negligence. Contractors frequently are madeto assume full responsibility for any and all unknown physical conditions, including subterranean, thatmay be found at the construction site. It suffices to say that the markup figure selected must take intoaccount the risks created by such contract provisions.By adding the markup to the project cost, the estimator develops the project price or the bid price. Thisis the price that will be submitted to the owner in an effort to win the contract. When competitivelybidding for projects, often it is useful to calculate project cost and project price individually and thendetermine whether the difference is adequate to cover the markup considerations already discussed.Project price is frequently determined by looking at current market conditions, such as the state of thelocal economy, the workload and backlog of competing contractors, the value of similar contractsawarded in recent months, and the number of bidders on the bid list. Using this method, the estimatoris better able to determine the value of the service being provided, rather than the cost, and make theappropriate adjustments to the bid. 3.24 Contract BondsMany construction contracts, especially those involving public owners, require that the prime contractorprovide the owner with a specified form of financial protection against contractor default. Two forms ofsurety bonds, called contract bonds, are used for this purpose. A contract bond is an agreement, theterms of which provide that a surety company will carry out the contractor’s obligations to theowner if the contractor itself fails to do so. A surety is a party that assumes the legal liability for the debt,default, or failure in duty of another.By the terms of its contract with the owner, the contractor accepts two principal responsibilities: toperform the objective of the contract and to pay all expenses associated with the work. Where contractbonds are called for, the general contractor is required to provide the owner with a performance bondand a labor and material payment bond. By the terms of these two bonds, the surety guarantees theowner that the work will be completed in accordance with the contract and that all construction costswill be paid should the contractor not perform as promised.Figure 3.8Highway bridge, recap sheet
  • 47. When the bidding documents provide that the successful contractor shall furnish the owner withperformance and payment bonds, as is the case with the Example Project, the contractor must purchasethese bonds if it is awarded the contract. The contractor obtains these bonds from the surety companywith which it customarily does business. Sureties are large corporate firms that specialize in furnishingmany forms of surety bonds, including contract bonds for contractors. The premium charge for thesebonds is substantial and varies with the type of work involved and the contract amount. This cost is paidby the contractor and must be included in the price estimate of the project. Because the bond outlay isbased on the total contract amount, it is normally the last item of expense to be added into the projectestimates, as shown in Figure 3.8. 3.25 Recap SheetTo calculate the needed bid unit prices, all costs associated with the highway bridge are now broughttogether in summary form on a recapitulation or recap sheet. Figure 3.8 is the recap sheet for the
  • 48. highway bridge. The expenses of labor, equipment, material, and subcontracts have been entered onthe recap sheet from the summary sheets in Figure 3.6 and Appendix A.On the recap sheet, the direct cost of the entire quantity of each bid item is obtained as the sum of itslabor, equipment, material, and subcontract expenses. The sum of all such bid-item direct costs givesthe estimated total direct cost of the entire project ($398,975). To this are added the job overhead,small tools, tax, markup, and the premium charge for the performance and payment surety bonds,giving the total price of $566,516. In Figure 3.8, the 15 percent markup includes an allowance for officeoverhead. Dividing the total project bid by the total direct project cost gives a factor of 1.4199. Bymultiplying the total direct cost of each bid item by this factor, the total amount of that bid item isobtained. Dividing the total bid cost of each bid item by its quantity gives the bid unit price. Bid unitprices customarily are rounded off to even figures.The unit prices just computed have been obtained on the basis that each bid item includes its own directcost plus its pro rata share of the project overhead, small tools, tax, markup, and bond. If these unitprices are now entered without change onto the bid form, this is called a balanced bid. For severalreasons, a contractor may raise the prices on certain bid items and decrease the prices on othersproportionately so that the bid amount for the total job remains unaffected. This is called an unbalancedbid. It is assumed here that the contractor will submit a balanced bid. Likewise, the unit pricesdetermined in Figure 3.8 are now entered in column 5 of Figure 3.9, the unit-price schedule of the bidform. The total estimated amounts in column 6 of Figure 3.9 are obtained by multiplying the unit pricesjust entered (column 5) by the estimated quantities (column 4). Because of the rounding off of unitprices, the project bid total is slightly different on the unit-price schedule of the bid form ($566,483.90),Figure 3.9, from what it is on the recap sheet ($566,516), Figure 3.8.When unit-price proposals are submitted to the owner, the low bidder is determined on the basis of thetotal estimated amount. Consequently, for contract award purposes, the amount of $566,483.90 inFigure 3.9 is treated just as a lump-sum bid. In cases of error in multiplication or addition by thecontractor in obtaining the estimated amounts in column 6 of Figure 3.9, it is usual for the unit prices tocontrol and the corrected total sum to govern.Figure 3.9Highway bridge, completed bid form 3.26 Project BudgetAssuming that our contractor is the successful bidder, it must now restructure its estimate into a moresuitable format for subsequent cost control of the actual construction work. This involves thepreparation of the control budget or the project budget, which is the detailed schedule of expenses thatthe project manager will use for cost control purposes during the construction phase. Figure 3.10 is thecontrol budget for the highway bridge project. The work quantities and prices contained in this figurehave been extracted from the bid-item summary sheets previously discussed and presented. Whenproject cost accounting is discussed in Chapter 10, the actual construction expenses of the highwaybridge are compared with the programmed costs contained in the project budget, Figure 3.10. As is
  • 49. discussed in Chapter 10, unit prices are especially useful for making quick and meaningful comparisonsof actual and budgeted expense for both labor and equipment. Unit costs of materials are not especiallysignificant except for estimating purposes and are not shown in Figure 3.10.Figure 3.10Highway bridge, project budget
  • 50. 4 Project Planning 4.1 CPM ProcedureConstruction time control is a difficult, time-consuming, and arduous management function. Projectmanagers work within an extremely complex and shifting time frame, and they need a management toolthat will enable them to manipulate large numbers of job activities and complicated sequentialrelationships in a simple and understandable fashion. The Critical Path Method (CPM) is just such anexpedient and constitutes the basis for the ensuing treatment of project time control. This methodapplies equally well to all construction work, large and small, intricate and straightforward.The management techniques of CPM are based on a graphical project model called a network. Thisnetwork presents in diagrammatic form those job activities that must be carried out and their mutualtime dependencies. A diagram of this type is a simple and effective medium for communicating complexjob interdependencies. It serves as a basis for the calculation of work schedules and provides amechanism for controlling project time as the work progresses.CPM is a three-phase procedure consisting of planning, scheduling, and time monitoring or controlling.Planning construction operations involves the determination of what must be done, how it is to beperformed, and the sequential order in which it will be carried out. Scheduling determines calendardates for the start and completion of project components. Time monitoring is the process of comparingactual job progress with the programmed schedule. Planning is the subject of this chapter. Schedulingand time monitoring are discussed in Chapters 5 and 9, respectively. 4.2 Planning PhasePlanning is the process of devising of a workable scheme of operations that, when put into action, willaccomplish an established objective. The most time-consuming and difficult aspect of the jobmanagement system—planning—is also the most important. It requires an intimate knowledge ofconstruction methods combined with the ability to visualize discrete work elements and to establishtheir mutual interdependencies. If planning were to be the only job analysis made, the time would bewell spent. CPM planning involves a depth and thoroughness of study that gives the construction teaman invaluable understanding and appreciation of job requirements.Construction planning, as well as scheduling, must be done by people who are experienced in, andthoroughly familiar with, the type of field work involved. Significant learning takes place during theplanning phase of a project. Therefore, the people doing the planning are in the best position to managethe work. The project network and the management data obtained from it will be realistic and usefulonly if the job plan is produced and updated by those who understand the job to be done, the ways inwhich it can be accomplished, and the job site conditions.To construct the job network, information must be sought from many sources. Guidance from keypersonnel involved with the project, such as estimators, the project manager, the site superintendent,and the field engineer, can be obtained from a planning meeting or perhaps a series of meetings. Thenetwork serves as a medium whereby the job plan can be reviewed, criticized, modified, and improved.As problems arise, consultations with individuals can clear up specific questions. The important pointhere is the need for full group participation in the development of the network and collective viewsmust be solicited.Participation by key subcontractors and suppliers is also vital to the development of a workable plan.Normally the prime contractor sets the general timing reference for the overall project. Individualsubcontractors then review the portions of the plan relevant to their work and help develop additionaldetails pertaining to their operations. An important side effect is that this procedure bringssubcontractors and the prime contractor together to discuss the project. Problems are detected earlyand steps toward their solutions are started well in advance.It must be recognized that the project plan represents the best thinking available at the time it isconceived and implemented. However, no such scheme is ever perfect, and the need for change is
  • 51. inevitable as the work progresses. Insight and greater job knowledge are acquired as the project evolves.This increased cognizance necessarily results in corrections, refinements, and improvements to theoperational plan. The project program must be viewed as a dynamic device that is continuouslymodified to reflect the progressively more precise thinking of the field management team.Construction planning may be said to consist of five steps:1. A determination of the general approach to the project2. Breakdown of the project into job steps or “activities†that must be performed3. Ascertainment of the sequential relationships among these activities4. Graphic presentation of this planning information in the form of a network5. Endorsement by the project teamTwo different planning methodologies are presented in this chapter: beginning-to-end planning and top-down planning. Beginning-to-end planning breaks the job into steps or activities, starting withmobilization of the project, and proceeds step by step through the project to completion. This methodpresumes some level of detail from the beginning or starts with limited detail and adds detail asplanning proceeds.Top-down planning, sometimes referred to as work breakdown structure, starts with the overall project,breaking it into its major pieces, then breaking the major pieces into their component pieces. Thisprocess continues until the pieces are of sufficient detail to satisfy the complexity of the project. Bothmethods arrive at the same result: job activities that can be used to form a graphical logic diagram. 4.3 Job ActivitiesThe segments into which a project is subdivided for planning purposes are called activities. An activity isa single work step that has a recognizable beginning and end and requires time for its accomplishment.The extent to which a project is subdivided depends on a number of practical considerations, but theseeight are suggested as guidelines for use when activities are being identified:1. By area of responsibility, where work items done by the general contractor and each of itssubcontractors are separated2. By category of work as distinguished by craft or crew requirements3. By category of work as distinguished by equipment requirements4. By category of work as distinguished by materials such as concrete, timber, or steel5. By distinct structural elements such as footings, walls, beams, columns, or slabs6. By location on the project when different times or different crews will be involved7. With regard to owner’s breakdown of the work for bidding or payment purposes8. With regard to the contractor’s breakdown for estimating and cost accounting purposesThe activities used may represent relatively large segments of a project or may be limited to small steps.For example, a reinforced concrete wall may be only a single activity, or it may be broken down intoerect outside forms, tie reinforcing steel, erect inside forms and bulkheads, pour concrete, strip forms,and cure. Trial and error together with experience are the best guides regarding the level of detailneeded. What is suitable for one project may not be appropriate for another. Too little detail will limitplanning and control effectiveness. Too much will inundate the project manager with voluminous datathat tend to obscure the significant factors and needlessly increase the cost of the management system.As a rule of thumb, the project manager should schedule to the same level of detail as he plans toexercise in management control.
  • 52. Not only is network detail a function of the individual project; it is also highly variable depending on whowill be using the information. For example, the project general contractor might show the installation ofa containment vessel on a nuclear power plant as a single activity. However, the subcontractorresponsible for moving and installing this enormously heavy vessel may require a complete planningnetwork to accomplish the task. Planning detail also varies with the level of project managementinvolved. This matter is further discussed in Sections 4.15 and 4.16. 4.4 Job Logic“Job logic†.T u y .A u u u g . Y y u y. Mu j g - k qu u u . N , j y qu , y g , u qu u x .I ’ y k u .A , g y qu x u , u g k k. H j g CPM g :I u g g u u u u .S g j qu ( g ) u j k, g y j .I g ,j g y x k. R ,j g u j u k g g . 4.5 RestraintsT , j u y j . Su u . T j g g y . P g g g ug u g . Su y u y y y j g u y u .H , k g z .R g , x , u .S y, , g , , y j . C qu y, y g g y y y g , , y.P j u , u y , .A x j qu , g j y u u qu . O j y k , y - , j g u , u - .A y y , y qu g u u u y u g .T g j j g. F u u u qu j .S - u g .F x , g y qu j k. R .I qu y , qu y g y . T y y. S y k u y , u k g .T“ - g†k u g g g u u u u g u j u y y g u .I y u u g g u u u z qu y u yg u u g
  • 53. .T g g y u u u j g u qu y. 4.6 Beginning-to-End PlanningF y , j u z y u .T , g j , u z y ug j .T g g g y y qu u g k y qu .I g y g , j u y g , g “M †y “Ex u #1,†“P g u #1.†S u u u qu y u . “O & ,†“P & g g ,†u u .A ug u , g g- - g k .S j x u u z y qu u .T y g qu .T y u g g j g g z g .I , g y u g u u yu qu j .F , - g g g y u y. 4.7 Top-Down Planning and the Work Breakdown StructureT - g x j .I Ex P j , u j .T j u u j g : , g y g , .T u u g u g , u u , , .T - g u g j u W kB k S u u(WBS), u y u u u u g , , g g .R g z x y j , y k j .T jWBS. I g y g , x j :1. P u2. F z k3. P u4. C u g5. D k6. F gI u , j j g k u WBS. F x :4. C u g4.1 A u #14.2 A u #2S y, u u .4.1 A u #1
  • 54. 4.1.1 F & u #14.1.2 P u u #14.1.3 S & u u #14.1.4 B k u #14.1.5 Ru u #1A WBS j A x C. T WBS u g g .I C 9, WBS u y , C 10, u g. I u u , g g y g j , j u u k k u . I , u u u WBS g y g k g .T u u u ky k u u k k.T j k u WBS u u .B g k y , WBS g y. A x ju , WBS qu u y j ug u y- z g j .W WBS y , g g u x .H g , j g y y .I u g y g g j g g u z j u g .O y ugg u k kg u g u k u y .A g u k k g u k g k. T u u y u k .T g k, yu g u j , ugg .I u , g u y k g g j u .I g g g , j gg u g k . 4.8 Precedence NotationT y u u k .T u y .T k y (AOA) A x D. A g y y y x k g .T k y (AON) .P g g g , y g y . O g g u S 4.11 D.19. B u g , z x.I g k, - u g y y y gu x. T y y qu g g y .T y y u g gu x. T u u g . 4.9 Precedence DiagramT g qu , , x y u .T g x k g .T g k y .W k g , u j g .T y g u u y .R
  • 55. g z u u .T u u u g g g .A y, u qu y u . W g u , u u u .M y u u g j u g.T u k g g, j , u u -u g. T qu : x , u g g , u g . T g g y y .A x , g .F g g g , u u u . T g u g g, g, u .C u , g qu .I y , k g gg u yz j .T g g qu F gu 4.1.E y k u y j y u y. E ug k u u u g , u , g g( - ) .C qu y, u y , x y j .I , g qu u g , g g g y u g g y. I g , “S †“F †g ug u x. T z gu , , u gu uu - u g .T u g k , F gu 4.1, - k u g y qu u g u .A y u u x u y y . W k u , y u u qu u g u g gg y j j .L gg y u u u qu .I x, kg y g u y u 5 10.Figure 4.1C g, g
  • 56. 4.10 Network FormatA z g u u y. T g y k , j g g j g .T qu y g y y .I uu g , g g u y y y y . A y y u u - - g .H , g y.Du g g , k k z g y y g .C u. T ug - - y g ; u y .T g y u y .T y , g u y u g y . F , “PR†g u “P †“PC†“P u .†E u k g ffi u , u g u u u g y g y .N k u g u u y y g .I y y g, , u k ,y , y, y u x y .W k g g g , g . I g y , u g k k y g u g .Y y k u g u .W x k , ju u u g x y j .I u g k y y ,u u y y .E g g u g , g , x k .D y g k y u u u g . “B k ,†, g g g g , g . B k qu u g u g g u k. A g qu y A y y B, y B g y A. L g y y u g x k k y qu . C u y u yj g .C u y u z u , u uu y .C g g yu u .V u u , k , j j g , k u .P x u x u y u g y g y , , y. 4.11 Lag RelationshipsF gu 4.1 u y g y u all of thoseactivities immediately preceding it have been completed. Also inherent in the notation used in thefigure is that an activity can start once all of its immediately preceding activities have been finished. Inthe figure, activity 60, “Fine grade,†cannot start un l activity 50, “Drive piles,†has beenfinished, and the start of activity 90, “Pour concrete,†must a ait comple on of ac vity 0,“Place rebar.†In addi on, by ay of e ample, ac vity 0, “Place rebar,†can startimmediately once activity 60, “Fine grade,†ac vity 0, “Place forms,†and ac vity 0,“Order and deliver rebar,†have all been nished. nder these condi ons, it is not possible to havethe finish of one activity overlap the start of a follo ing activity. Where such a condition potentiallye ists, the activity must be further subdivided.
  • 57. There are cases, ho ever, here there may be a delay bet een the completion of one activity and thestart of a follo ing activity, or there is a need to sho that one activity ill overlap another in somefashion. Precedence diagrams can be made to sho a variety of such conditions using lag relationships.The concept of lags is developed more completely in Section 5.21. 4.12 Precedence Diagram for Highway BridgeGetting started on a large project can be overwhelming, and a general job plan of limited size can beuseful as a means of getting started. Once a general job plan has been put together, it is an excellentframework on which to amplify the network to the level of detail desired. Some practitioners favorstarting job planning by compiling a relatively short list of major project operations arranged inchronological order. On the highway bridge, described in Section 3.4, this initial list could be:a. Procurementb. Field mobilization and site workc. Pile foundationsFigure 4.2Highway bridge, general job pland. Abutments and wingwallse. Deckf. Finishing operationsThis list can be used to prepare a preliminary job plan, such as the one shown in Figure 4.2. The majoroperations in the preceding list are much the same as, and could be identical to, those previouslyidentified by the bar chart in Figure 3.5, when a preliminary time analysis of the project was madeduring the estimating period. A general job plan like that shown in Figure 4.2 is useful in the sense that itplaces the entire project in perspective. It is profitable for the planner to establish a general frame ofreference before beginning to struggle with the intricacies of detailed job planning.All of the steps in job planning have now been reviewed. Providing that the simple rules of precedencediagramming are followed, it should be possible to develop a working diagram for the highway bridge. Acompany prebid conference has established the general ground rules of procedure for this project. Oneabutment at a time will be constructed for reasons of equipment limitations and the economy of formreuse. Abutment #1 will be constructed first with its footing being poured initially, followed by thebreast and wing walls. As excavation, pile driving, forming, and pouring are completed on abutment #1,these operations move over to abutment #2. Only one set of footing forms and abutment wall forms willbe made, these being used first on abutment #1 and then moved over to abutment #2.As soon as the steel girders have been delivered, the concrete abutments stripped, and abutment #1backfilled, the steel girders will be placed. Forms and reinforcing steel for the deck slab can follow.Abutment #2 must be backfilled before the deck can be poured. Concrete patching and rubbing can bestarted as the abutments are stripped and must be finished before painting can start. Job cleanup andfinal inspection complete the project.
  • 58. Figure 4.3 (see insert between pages 88 and 89) is the precedence diagram that results from thehighway bridge logic just established. Most of the dependencies on the diagram are normaldependencies in that they are the natural result of the physical nature of the activities themselves.However, the figure also includes some resource restraints. When such restraints have been firmlyestablished, it is advisable to include them in the first draft of the network because they can besignificant planning factors that have a major effect on the project plan and schedule. By way ofexplanation, refer to activities 10, 20, and 50 in Figure 4.3, using activity 20 as a typical example.Activity 20, “Prepare & approve S/D footing rebar,†is a consequence of a construc on contractrequirement that the prime contractor and its subcontractors submit shop drawings (S/D) and otherdescriptive information concerning project materials and machinery to the owner or project designprofessional for their approval. This must be done before these materials can be fabricated andprovided to the job site. Shop drawing approval and material fabrication and delivery are shownseparately on Figure 4.3. This is because the delivery of reinforcing steel and other materials to theproject typically is quoted by the vendor as requiring a stipulated period of time after the generalcontractor returns approved shop drawings to the vendor.With regard to material restraints such as activity 30, an additional matter may have to be considered.For example, if the piles are sold to the contractor “FOB trucks, job site†—and this istypical—the contractor is responsible for unloading the vendor’s trucks when they arrive on the jobsite. (FOB is an abbreviation for “freight on board†and refers to the delivery point covered by thevendor’s quote.) In such an instance, the planner may wish to emphasize this fact by includinganother activity, “Unload piles,†at the end of ac vity 30. This simply serves as a reminder to allconcerned that the contractor must make advance arrangements to have suitable unloading equipmentand workmen available when delivery is made. Unloading activities have not been included in Figure 4.3,however, so that the discussion can concentrate on basics.An equipment restraint has also been included in Figure 4.3. The driving of steel pilings for the twoabutments requires an assembly of equipment units, including a large crane, which must be mobilizedbefore pile driving can start. This is illustrated by activity 100, “Mobilize pile-driving rig,†whichprecedes activity 110, “Drive piles abutment #1.†A er the piles are driven for both abutments,the pile-driving rig is demobilized. As shown, this disassembly process must occur before activity 180,“Forms & rebar abutment #1,†can start because the crane used for pile driving is required tohandle the forms and rebar for this abutment. Abutment #2 follows at a later date. Another resourceconstraint in Figure 4.3 arises because the same concrete forms are going to be used for bothabutments. As a result of this decision, activity 240, “Forms & rebar abutment #2,†cannot startuntil activity 220, “Strip & cure abutment #1,†has been completed. In a similar manner, the sameforms will be used for both footings. 4.13 Value of Precedence NetworkFigure 4.3 is not only a lucid job model, it is also an effective tool useful for day-to-day direction andcontrol of the work. Figure 4.3is the job plan for the highway bridge project. Preparing the network hasforced the job planners to think the job through completely from start to finish. Decisions have beenmade about equipment, construction methods, and sequence of operations. The field supervisory teamnow possesses a depth of knowledge about the project that can only be obtained through such adisciplined process of detailed job analysis.The job plan, in the form of a precedence diagram, is comprehensive, detailed, and in a form that is easyto communicate to others. The network diagram is an expedient medium for communication betweenfield and office forces. If for some reason the project manager or field superintendent must be changedduring construction, the diagram can assist appreciably in effecting a smooth transition. The diagrammakes job coordination with material dealers, subcontractors, owners, and architect-engineers a mucheasier matter. The orderly approach and analytical thinking that have gone into the network diagramhave produced a job plan far superior to any form of bar chart or narrative analysis. Invariably, synthesisof the network results in improvements to original ideas and a sharpening of the entire approach to theproject. 4.14 Repetitive Operations
  • 59. Some kinds of construction projects involve long series of repetitive operations. Pole lines, highways,pipelines, multistory buildings, and tract housing are familiar examples of construction jobs that entailseveral parallel strings of continuing operations. One segment of the Example Project described inSection 2.17 is the relocation of five miles of natural gas pipeline. This is a good example of aconstruction operation that will involve repetitive operations that proceed simultaneously.For purposes of discussing the planning of such a project, the major repetitive segments of the pipelinerelocation have been identified as:Locate & clear Lay pipeExcavate TestString pipe BackfillFigure 4.4Pipeline relocation, basic planThe basic plan for this job is shown in Figure 4.4 with all the operations being sequential except forexcavate and string pipe, which are done concurrently. However, no pipeline contractor would proceedin such a single-file manner unless the pipeline was very short in length or some special circumstanceapplied. Rather, location and clearing work would get well under way. Excavation, together with pipestringing, would then start, and pipe laying would proceed fairly closely behind. Pressure testing of thepipe and backfilling complete the sequence. After the project gets “strung out†along the right-of-way, all these operations will move ahead sequentially, one stage following the next.All this makes it clear that more detail than is included in Figure 4.4 will be necessary if the job plan is tobe useful. The way to accomplish this is to divide the pipeline into arbitrary but typical repeatingsections. The length of the repeating section chosen can be quite variable, depending on the length ofthe pipeline, terrain, contract provisions, and other job conditions. For discussion purposes, suppose thecontractor decides that a mile-long section of pipeline represents a fairly typical unit of work. This wouldbe exclusive of river, railroad, and highway crossings, which are frequently done in advance of the mainpipeline and which may require their own planning and scheduling studies as separate operations.Figure 4.5 indicates how the basic plan can be broken down into mile-long units.The notation used in Figure 4.5 is one where the individual activity box indicates only the section of thepipeline involved. The work categories listed at the left margin of the figure apply to the horizontalstring of activities at each successive level. The logic of the figure shows that after a mile of the pipelineright-of-way has been located and cleared, both excavation and pipe stringing start. These latter twoactivities proceed simultaneously, since one does not depend on the progress of the other. Afterexcavation and pipe stringing have proceeded one mile, pipe-laying starts. Testing and backfill begin inthe order shown. Once a work phase is started, it will proceed more or less continuously until itscompletion.Figure 4.5
  • 60. Pipeline relocation, precedence diagram planning 4.15 Network InterfacesOften different portions of the same project are planned separately from one another. However, asfrequently happens, the individual construction plans are not truly independent of one another, and thetwo networks are actually related in some way. Thus, the two networks must interface with each otherso that mutual dependencies are transmitted properly from one plan to the other. The term“interface†refers to the dependency between ac vi es of two di erent networks. Thisdependency can be indicated on the networks by dashed sequence lines between the affected activities.The pipeline relocation will be used to illustrate the workings of an interface. Assume that his jobincludes a stream crossing at the end of the third mile of pipeline. The construction of the crossingstructure will be separate from that of the pipeline, but the two must be correlated so the crossingstructure is ready for pipe by the time the pipeline construction has progressed to the crossing location.In this instance, planning of the pipeline itself and of the crossing structure proceed independently ofone another. Figure 4.5 is the planning network for the pipeline work. The crossing is to be effected by asuspension-type structure, and Figure 4.6 is its construction plan.The required job logic of having the crossing structure ready to accept pipe by the time the pipeline hasreached the crossing site can be imposed by having activity 110 of Figure 4.6 immediately follow activity170 of Figure 4.5. This is shown in both figures by the dashed dependency line. Ensuring that thecrossing structure is started soon enough for the desired meshing of the two networks is now a matterof scheduling and will be treated in Chapter 5. 4.16 Master NetworkAs illustrated by Figure 2.1, the total Example Project consists of several major subprojects, each beingrelatively self-contained and independent of the others. The planning networks of two of thesesegments of the Example Project, the highway bridge and the pipeline relocation, have been developed.It is now easy to visualize that similar planning diagrams must be developed for the river diversion, haul
  • 61. roads, borrow development, earth dam, and other major project elements. These separate networkswould be used for the detailed time scheduling and daily field management of the several componentsof the Example Project. In a general sense, each of the major project segments is constructed andmanaged separately.Figure 4.6Pipeline crossing structure, precedence diagram planningThe planning for each subproject is done in considerable detail. This fact is obvious from the nature ofthe networks developed for the highway bridge and the pipeline relocation. Although this level of detailis necessary for the day-to-day field control of construction operations, it is overwhelming for an owneror project manager who wants to keep abreast of overall site operations in a more general way. Theamount of detail required by managers decreases with their increased span of authority. A fieldmanager requires information and data that are tailored to the level of his responsibilities.
  • 62. On the Example Project, a master planning network would be prepared that encompasses and includesevery subproject. The level of detail of this diagram would be relatively gross, with each activityrepresenting substantial segments of the field work. The highway bridge and the pipeline relocationwould each appear as a small cluster of associated activities. It is likely that the highway bridge wouldappear in the master diagram as the activities shown in Figure 4.2, and the pipeline relocation would beas presented in Figure 4.4. The master job plan concerns itself essentially with the big picture, the broadaspects of the major job segments and how they relate to each other. Keeping the master network freeof excessive detail is necessary to the production of an overall plan that can be comprehended andimplemented by those who must apply it. 4.17 SubnetworksThe detailed planning diagrams of the highway bridge, Figure 4.3, and of the pipeline relocation, Figure4.5, are spoken of as subnetworks of the master network. As has been discussed, lower-level fieldmanagement uses them for everyday direction and control of the work. It would be possible, of course,to draw an overall project network that would combine the detailed planning networks of all thesubprojects into one enormous diagram. However, such an all-inclusive network would be so large andcumbersome as to be virtually useless to anyone concerned with the Example Project. The detailedplanning of an extensive construction contract such as the Example Project is accomplished primarilythrough the medium of many subnetworks, with their interdependencies indicated by appropriateinterfaces. In this way, management personnel can concentrate on their own localized operations. Eachmanager can monitor his work according to his own plan without the distraction of having to wadethrough masses of information irrelevant to him and his responsibilities. It is also entirely possible thatcertain activities of the highway bridge network (Figure 4.3) or of the pipeline relocation network (Figure4.5) might require further expansion into more detailed subnetworks. To ensure their timelyaccomplishment, it is sometimes desirable to subject certain critical activities to further detailedplanning study. To illustrate, activity 100, “Mobilize pile-driving rig,†of Figure 4.3 might beexpanded into its own planning subnetwork, as shown by Figure 4.7.Figure 4.7Mobilize pile-driving rig, precedence diagram planning 4.18 Computer Applications for PlanningComputers have a major impact on the way construction professionals plan, schedule, and controlprojects. In the succeeding chapters, computer applications for each phase of construction managementwill be discussed. Because of the rapid changes in computer technology and software sophistication,only the fundamentals of computer applications are appropriate for discussion.Earlier in this chapter, it was stated that planning is the most important phase of project management,and it is also the most difficult and time consuming. This is because the knowledge, experience, andinsight of the project team must be brought together to identify a plan that is both complex and
  • 63. uncertain. For years, the process was one of holding a planning meeting, drawing the network on paper,holding another planning meeting, revising the network drawing again and again until the team wassatisfied or ran out of time.Computers with graphics capabilities have had a major impact on the planning process becausenetworks are drawn on the computer screen. With a projector, the network is displayed on a screen asthe project team is developing it. One person, using the computer, records each idea as the plan is beingdeveloped. Each addition to the plan can be seen, understood, and if necessary criticized by the otherteam members. In this way, the skills of the team are combined and a dynamic plan is developed inmuch less time than was previously required. Developing networks using software offers significantadded flexibility over manual drafting. Individual activities or whole groups of activities can be movedaround on the screen. Individual parts of the network can be created independently and then combinedwith the main network. Multiple approaches to a particular planning problem can be created, evaluated,and compared, with the best solution used in the final plan.Perhaps the best part of this type of planning is that it involves each member of the project team in ahighly collaborative planning process. The resulting plan is perceived to be the team’s plan ratherthan one provided by the planning department. Everyone on the team now has a stake in making thisplan work. This perception alone causes each phase of the project management system described in thesucceeding chapters to contribute to a successful project.
  • 64. 5 Project Scheduling 5.1 Scheduling ProcedureChapter 4 dealt with the procedures followed in developing a project plan and describing that plan as aCritical Path Method (CPM) network diagram. Once this network diagram has been developed, the timemanagement system enters the next phase, that of work scheduling. Thus far, all planning effort hasbeen directed at defining the work to be accomplished and the order in which that work must be carriedout. Time relating to overall project construction duration or the time required to complete individualactivities has not been factored into the plan. This chapter is concerned with the time scheduling ofconstruction projects.As has been stated previously, the CPM was developed especially for the planning and scheduling ofconstruction operations and is the procedure used throughout this text. However, it is of interest tonote that a somewhat different procedure, Program Evaluation and Review Technique (PERT), has beendevised for application to the scheduling of research and development projects. Because research isgenerally highly exploratory in nature, historical experience and background are rarely good measuresfor future time estimates, and make reasonably accurate time estimates difficult to establish. As a result,researchers have developed PERT as a method of statistically evaluating project duration over a time-sensitive domain. Although basically similar, CPM and PERT differ in several important respectsconcerning the estimation of activity time durations. PERT provides some important lessons regardingprobability and project duration, which will broaden a construction manager’s prospective. This topicis covered in Appendix E. In this chapter, only the CPM scheduling method is developed and applied.A project schedule is a projected timetable of construction operations that will serve as the principalguideline for project execution. Several steps are involved in devising an efficient and workable jobschedule. The next list of eight steps is offered as a procedural guide.1. Estimate the time required to carry out each network activity.2. Compute the time period required for overall project completion using these time estimates.3. Establish time intervals within which each activity must start and finish to satisfy the completion daterequirement.4. Identify those activities whose expedient execution is crucial to timely project completion.5. Shorten the project duration at the least possible cost if the project completion date will not meet thecontract or other requirements.6. Adjust the start and finish times of selected activities to minimize resource conflicts and smooth outdemands for manpower and equipment using surplus or float times that most activities possess.7. Make a working project schedule that shows anticipated calendar dates for the start and finish ofeach network activity.8. Record the assumptions made and the plan’s vital boundary conditions. These will become anintegral aspect of the completed baseline project schedule.This chapter discusses the first four steps just described. The remainder are presented in subsequentchapters. The highway bridge and pipeline relocation will be used to present the several facets ofconstruction scheduling. 5.2 Activity TimesCPM customarily uses a single time estimate for each network activity. In construction, each activity is“deterministic†y .Su x u y qu
  • 65. y u j .S g v u x u v y y .I u u y, v y u u y x g y, ug u , u u , , , u . T u u j g u gu .O u , u u y ug u .M u . W g y u u v y u u g u . 5.3 Rules for Estimating Activity DurationsT u j u y j g g u y v u v y .A g u , y v g x .I , y gu u g j g. N v , u y u u u gv v y, u u v v y .Sx u y v y u :1. Evaluate activities one at a time, independently of all others. For a given activity, assume thatmaterials, labor, equipment, and other needs will be available when required. If there is a fundamentalreason to believe that this will not be true, then the use of a preceding restraint may be in order.2. For each activity, assume a normal level of manpower and/or equipment. Exactly what “normalâ€is in this context is difficult to define. Most activities require only a single crew of workers or a standardspread of equipment. Based on experience, conventional crew sizes and equipment spreads haveemerged as being efficient and economical. In short, a normal level is about optimum insofar asexpedient completion and minimum costs are concerned. A normal level may be dictated by theavailability of labor and equipment. If shortages are anticipated, this factor must be taken into account.However, conflicting demands among concurrent activities for workers or equipment will be temporarilyignored. At this stage, such conflicts are only matters of conjecture, and they will be investigated indetail during a later stage of scheduling.3. If time units of working days are being used, assume a normal workday. Do not consider overtime ormultiple shifts unless this typical or a part of the standard workday. Around-the-clock operations arenormal in most tunnel work, for example, and overtime is extensively used on highway jobs during thesummer months to beat the approaching cold weather. Some labor contracts guarantee overtime workas a part of the usual workday or workweek. In these cases, the extra hours are normal and should beconsidered.4. Concentrate on estimating the duration of the individual activity and ignore all other timeconsiderations. In particular, the completion date of the project must be put entirely out of mind.Otherwise, there is apt to be an effort made, consciously or unconsciously, to fit the activities within thetotal time available. This is one of the serious drawbacks of the bar chart as a planning and schedulingdevice. Most contractors will admit that the average bar chart is made up primarily by adjusting theindividual work items to fit within an overall time requirement. The only consideration pertinent toestimating an activity duration is how much time is required to accomplish that activity, and that activityalone.5. Use consistent time units throughout. When using the working day as a time unit, it must beremembered that weekends and holidays are not included. Certain job activities, such as concretecuring or systems testing, continue during nonworking days. To some extent, allowances can be madefor this. For example, curing periods of seven days will involve only five working days. In most cases,however, such corrections and conversions cannot be exact and must be based on the scheduler’sbest judgment. When using a computer program to facilitate schedule calculations, check to seewhether the program supports multiple calendars and use the method suggested by the softwaredeveloper. Associated with the use of consistent time units is the matter of conversion of time periodsfrom one base to another. For example, vendors invariably express delivery times in terms of calendar
  • 66. days. If the delivery of a pump is given as 30 days by the vendor, this will translate into approximately 21working days. Again, most computer programs handle these problems with multiple calendars. Manualcalculations require the scheduler to make these adjustments to the durations by hand.6. Assume normal weather conditions in estimating the duration needed to accomplish each activity.Some operations are sensitive to the effects of weather and may not be performed at all or will takelonger to complete if necessary climatic conditions are absent. In general, such activities should beestimated assuming the existence of conducive weather. Using historical weather data for the sitelocation, operation-specific calendars can be developed to account for the seasonal variations thatweather will have on these activities. This process is discussed further in Section 5.19. 5.4 Estimating Activity DurationsIt is important that someone experienced in, and familiar with, the type of work involved be responsiblewhen the activity durations are being estimated. With respect to work done by subcontractors, it isgood practice to solicit input from them concerning the times required for those activities for which theyare responsible. Subcontractors usually are in the best position to render judgments concerning thetimes required for the accomplishment their work.One effective way of estimating an activity duration is to compute it by applying a crew or equipmentproduction rate to the total number of units of work to be done. For illustrative purposes, thedetermination of time estimates for two of the activities on the highway bridge will be discussed. First,consider activity 110, “Drive piles, abutment #1,†as it appears in Figure 4.3. The summary sheetfor Bid Item No. 4 in Appendix A shows that a pile-driving production rate of 70 linear feet per hour wasused when the cost of the highway bridge was estimated. Each abutment involves the driving of twenty-eight 40-foot-long piles. Dividing the total lineal footage of 1120 feet by 70 gives 16 hours, or twoworking days. 28 piles × 40 ft/pile = 1.140 ft 1,140 ft ÷ 70 ft/hr = 16.3 hrsIn addition to the actual pile driving, most of one day will be required to prepare the templates, cut offpile heads, and move the equipment. Thus, the time estimate for this particular activity will be threedays. In a similar manner for activity 200, “Pour abutment #1,†Figure 3.6 shows that the concretefor this abutment will be poured at the rate of 8.75 cubic yards per hour. This production rate can beused to compute the time required to pour the abutment. Each abutment contains 140 cubic yards ofconcrete, and dividing this by 10 cubic yards per hour gives 14 hours, or about two working days. 140 cy ÷ 8.75 cy/hr = 16 hrsAnother approach in determining activity times is to assume a crew size and use the estimated laborunit cost rather than a production rate. To illustrate this procedure, Bid Item No. 3 in Appendix A showsthe unit labor cost for compacted backfill to be $8.45 per cubic yard. Activities 280 and 310 each include170 cubic yards of compacted backfill. Thus, each of these activities has a direct labor cost of: 170 cy × $8.45/cy = $1,436.50Assume a crew of three laborers with a daily labor cost of: 3 laborers × 8 hrs/day × $22.00/hr = $528/dayDividing $1,436.50 by $528/day gives 2.7 days, or approximately three days. Hence, the estimatedduration of activities 280 and 310 will each be three working days.When estimating activity times, one special circumstance must be kept in mind: the case where thesame work item is repeated several times during the construction period. For example, successive jobactivities may involve repetitions of essentially identical concrete forming. The time performance onsuch work will improve considerably during the first few cycles. This learning-curve effect causes thelater items to be accomplished in less time than the first ones. The basic proposition of the learning-
  • 67. curve phenomenon is that skill and productivity in performing the same work improve with experienceand practice and therefore should be reflected in the network durations.Time estimates of surprising accuracy often can be made informally. Experienced constructionsupervisors have an almost uncanny ability to give off-the-cuff time estimates that usually prove to bereasonably close. This may seem to be an almost casual approach to such an important matter, butexperience shows that it has its place, especially when checking against time values obtained bypresumably more exact means. Input from field superintendents is valuable and desirable, but it wouldbe a mistake to allow them to make all the duration estimates in such an informal fashion. If for noother reason, they are human and their time estimates are apt to be generous so their chances ofstaying on schedule later on are commensurately improved.Activity durations customarily are expressed in terms of full working days because, in most cases, to dootherwise is to assume a fictitious degree of accuracy. If an activity time is less than one working day,the activity concerned may be too small for practical job scheduling and control. Figure 5.1 (see insertbetween pages 88 and 89), the logic for which has been presented in Figure 4.3, shows the estimateddurations for each activity of the highway bridge. Each activity duration, in terms of working days, isshown in the lower, central part of the activity box in Figure 5.1. Each activity is also given an identifyingnumber, located in the upper, central part of the activity box. The other numerical values shown withthe activities and the contingency activity at the right end of the figure will be discussed later. 5.5 Time ContingencyWhen applying the CPM procedure to a construction project, it is assumed that individual activitydurations are deterministic in the sense that they can be estimated relatively accurately and that theiractual durations will have only relatively minor variances from the estimated values. An estimatedactivity duration is the time required for its usual accomplishment and does not include any allowancefor random or unusual happenings. An estimated or likely completion time for the entire project can becomputed by using such estimates of individual activity times. The actual project completion timeprobably will vary from this estimated value for a number of reasons that cannot be entirely predictedor quantified by the planning team. When the time estimate is made for an activity, it is based on theassumption that “normal†conditions will prevail during its accomplishment. Although normalconditions are difficult to define, the concept is accurate enough to recognize that many possibilities of“abnormal†occurrences can substan ally increase the actual construc on me. oncessions forabnormal or random delays are accounted for in a number of ways, the simplest being a contingencyallowance. Where these occurrences can be recognized as activity specific, the contingency may beadded in the form of an uncertainty variance to the activity duration. This concept is fundamental to thePERT method (see the PERT procedure in Appendix E for a better understanding of probabilistic timeanalysis and its effect on project duration).In most cases, though, a contingency allowance cannot be applied to individual activities to account forgeneral project delays, such as those caused by fires, accidents, equipment breakdowns, labor problems,late material deliveries, damage to material shipments, unanticipated site difficulties, and the like. Oftenit is impossible to predict which activities may be affected and by how much. As a result, a generalallowance for such time contingencies normally is added to the overall project duration or at the end ofspecific construction sequences. 5.6 Project Weather DelaysProbably the most common example of project delay is that caused by inclement weather. It isimportant that the probable effect of adverse weather be reflected in the final project time schedule.The usual basis for making time estimates is on the assumption that construction operations willproceed on every working day. However, it is obvious that there can be a profound difference in thetime required for excavation, depending on whether the work is to be accomplished during dry or wetweather. Similarly, snow, cold temperatures, and high winds can substantially affect the times requiredto do certain types of construction work.How allowances for time lost because of inclement weather are handled depends to a great extent onthe type of work involved. When most highway, heavy, and utility work are affected by the weather,normally the entire project is shut down. On buildings and other work that can be protected from theweather, allowances for time lost are commonly applied to those groups of activities susceptible to
  • 68. weather delay. Seldom is a job of this type completely shut down by bad weather after it is enclosed.Some parts of the job may be at a standstill while others can proceed. Although one or more weathercontingencies can be used in a network, a preferred solution is to account for weather using activitycalendars, a subject that is be covered in Section 5.19. 5.7 Network Time ComputationsThe scheduling of detailed activities in a network generally is done by computer, with times expressed interms of calendar dates or expired working days. However, the optimum use of this information forproject time control purposes requires the user to have a thorough understanding of the computationsand the true significance of the data generated. Time values generated by a “black box†with noinsight into the process cannot be used in optimal fashion to achieve time management purposes. Forthis reason, the manual computation of activity times is discussed in detail in the sections that follow.When these calculations are made by hand, they normally are performed directly on the network itself.When making the initial study with manual computations, activity times usually are expressed in termsof expired working days. Likewise, the start of the work being planned customarily is taken to be at timezero.After a time duration has been estimated for each activity, some simple step-by-step computations areperformed. The purpose of these calculations is to determine (1) the overall project completion timeand (2) the time brackets within which each activity must be accomplished to meet the completion date.The network calculations involve only additions and subtractions and can be made in different ways,although the data produced are comparable in all cases. The usual procedure is to calculate what arereferred to as activity times. When arrow notation is being used, so-called event times can also be usedas a basis for network computations (see Section D.10). Activity times play a fundamental role in projectscheduling, and their determination is treated in this chapter. Event time computations are discussed inAppendix D.The calculation of activity times involves the determination of four limiting times for each networkactivity. The “early start†(ES) or “earliest start†of an ac vity is the earliest me that theactivity can possibly start, allowing for the times required to complete the preceding activities. The“early finish†(EF) or “earliest finish†of an ac vity is the earliest possible me that it can becompleted, and is determined by adding that activity’s duration to its early start time. The “latefinish†(LF) or “latest finish†of an ac vity is the very latest that it can be nished and allow theentire project to be completed by a designated time or date. The “late start†(LS) or “lateststart†of an ac vity is the latest possible me that it can be started if the project target completiondate is to be met and is obtained by subtracting the activity’s duration from its latest finish time.The computation of activity times can be performed manually or by computer. When calculations aremade by hand, they normally are performed directly on the network itself. When the computer is used,activity times are shown on the computer-generated network or in tabular form. When making manualcomputations, it is normal to use project days, working in terms of expired working days. ommensurately, the start of the project is customarily taken to be time zero (the end of project dayzero). When computations are done by computer, calendar dates often are used so that early and latestarts are in the morning of the calendar day and early and late finishes are in the afternoon of thecalendar day. 5.8 Early Activity TimesThe highway bridge network shown in Figure 5.1 is used here to discuss the manual calculation ofactivity times directly on a precedence diagram. Precedence diagrams are exceptionally convenient forthe manual calculation of activity times and afford an excellent basis for describing how suchcalculations are done. This section discusses the computation of the early-start and early-finish times.The determination of late activity times is described subsequently. The early time computations proceedfrom project start to project finish and from left to right in Figure 5.1, this process being termed theforward pass. The basic assumption for the computation of early activity times is that every activity willstart as early as possible. That is to say, each activity will start just as soon as the last of its predecessorsis finished.The ES value of each activity is determined first, with the EF time then being obtained by adding theactivity duration to the ES time. To assist the reader in understanding how the calculations proceed,
  • 69. small sections of Figure 5.1 are used in Figure 5.2 to illustrate the numerical procedures. Reference toFigure 5.1 shows that activity 0 is the initial activity. Its earliest possible start is, therefore, zero elapsedtime. As explained by the sample activity shown in Figure 5.1, the ES of each activity is entered in theupper left of its activity box. The value of zero is entered at the upper left of activity 0 in Figure 5.2a. TheEF of an activity is obtained by adding the activity duration to its ES value. Activity 0 has a duration ofzero. Hence the EF of activity 0 is its ES of zero added to its duration of zero, or a value of zero. EF valuesare entered into the upper right of activity boxes, and Figure 5.2a shows the EF value of activity 0 to bezero. Activity 0 calculations are trivial, but the use of a single opening activity is customary withprecedence diagrams.Figure 5.2Highway bridge forward-pass calculations
  • 70. Figure 5.1 shows that activities 10, 20, 30, 40, and 50 can all start after activity 0 has been completed. Ingoing forward through the network, the earliest these five activities can start is obviously controlled bythe EF of the preceding activity. Since activity 0 has an EF equal to zero, then each of the five activitiesthat follow can start as early as time zero. Figure 5.2b shows that activities 30 and 40 have ES values ofzero. Zeros have been entered, therefore, in the upper left of activities 30 and 40. This is typical foractivities 10, 20, and 50 as well. The EF of activity 30 is its ES of zero plus its duration of 15 or a value of15. Likewise, the EF value of activity 40 is zero plus 3 or a value of 3.Continuing into the network, Figure 5.1 and Figure 5.2c show that activities 80, 90, or 100 cannot startuntil activity 40 has been completed. Activity 40 is referred to as a burst activity, which is an activity thatis followed by two or more activities. The earliest that activity 40 can finish is at the end of the third day.Using activities 80 and 90 as examples, it is seen that the earliest these two activities can be started isday 3. The EF of activity 80 will be its ES value of 3 plus its duration of 3, or a value of 6. In like fashion,activity 90 will also have an EF value of 6. These values have been entered into the activity boxes inFigure 5.2c.Figures 5.1 and 5.2d show that activity 130 cannot start until both activities 70 and 110 are finished. TheEF values of activities 70 and 110 are 12 and 18, respectively. Because the ES of activity 130 depends onthe completion of both activities, it follows that the finish of activity 110, not that of activity 70, actuallycontrols the start of activity 130 and that activity 130 will have an early start of 18. Activity 130 is anexample of a merge activity—an activity whose start depends on the completion of two or morepreceding activities. The rule for this and other merge activities is that the earliest possible start time ofsuch an activity is equal to the latest (or largest) of the EF values of the immediately preceding activities.The forward-pass calculations consist only of repeated applications of the few simple rules justdiscussed. Working methodically in step-by-step fashion, the computations in Figure 5.1 proceed fromactivity to activity until the end of the network is reached. The reader is reminded that the figures andcalculations shown in Figure 5.2 were for explanatory purposes only. The actual forward-passcalculations would have commenced with activity 0 in Figure 5.1, with the ES and EF values beingentered onto the activity boxes as the calculations progressed. As is now obvious, the calculations areelementary and, with practice, can be performed rapidly. Even so, when several hundred activities areinvolved, the manual development of activity times can be tedious, time consuming, and subject toerror. 5.9 Project DurationReference to Figure 5.1 will disclose that the early-finish time for the last work activity (400) is 64elapsed working days. For the job logic established and the activity durations estimated, it will require64 working days to reach the end of the project, provided that each activity is started as soon aspossible (or at its ES time). Thus, if a competent job of planning has been done, if activity durations havebeen accurately estimated, and if everything goes well in the field, project completion can beanticipated in 64 working days or about 7/5 × 64 ≈ 90 calendar days. In this regard, any laborholidays that occur on regular workdays must be added to the 90 calendar days just obtained. As will beseen in Section 5.16, the construction period for the highway bridge will be during the months of Juneinto September. During this time, the holidays of Independence Day and Labor Day will occur. Therefore,the construction period will require approximately 92 calendar days.The matter of contingency must again be considered at this point. Some provision must be made forgeneral project delays caused by a variety of troubles, oversights, difficulties, and job casualties. At thisstage of project scheduling, many contractors will plan on a time overrun of 5 to 10 percent and add thisto the overall projected time requirement for the entire work. The percentage actually added must bebased on a contractor’s judgment and experience. In Figure 5.1, a contingency of six working dayshas been added to the diagram in the form of the final contingency activity 410. Adding an overallcontingency of six working days gives a probable job duration of 70 working days. To the contractor’sway of thinking, 70 working days represents a more realistic estimate of actual project duration thandoes the value of 64. If everything goes as planned, the job probably will be finished in about 64 workingdays. However, if the usual difficulties arise, the contractor has allowed for a 70-working-dayconstruction period.
  • 71. Whether the contractor chooses to add in a contingency allowance or not, now is the time to comparethe computed project duration with any established project time requirement. Again, the highwaybridge will be used as an example. Assuming a contingency of six working days, the estimated projectduration is: 7/5 × (64 + 6) + 2 labor holidays ≈ 100 calendar daysThis project duration is compared with the completion date established by the Example Project masterschedule or by the time provision in the construction contract. If the highway bridge must be completedin 90 calendar days, then the contractor will have to consider ways in which to shorten its time duration.If a construction period of 100 calendar days is permissible, the contractor will feel reasonably confidentthat it will be able to meet this requirement and no action to shorten the work is required. How to goabout decreasing a project’s duration is the subject of Chapter 7.The probable project duration of 100 calendar days or approximately 14 weeks is a valuable piece ofinformation. For the first time the contractor has an estimate of overall project duration that it can relyon with considerable trust. The difference in confidence level between the value of the 14 weeks thathas just been obtained and the 15 weeks derived earlier from the bar chart in Figure 3.5 should beapparent. 5.10 Late Activity TimesFor purposes of discussion in the remainder of this chapter, it is assumed that a project duration of 100calendar days, or 70 working days, for the highway bridge is acceptable. Unless there is some mitigatingcircumstance, there is no point in the contractor’s attempting to rush the job and certainly there isnothing to be gained by deliberately allowing the work to drag along. The normal activity durations usedas a scheduling basis represent efficient and economical operation. Shorter activity times usually willrequire expensive expediting actions. Longer activity times suggest a relaxed attitude and increasedcosts of production. Certainly job overhead expense increases with the duration of the constructionperiod.Having established that 70 working days is satisfactory, job calculations now turn around on this value,and a second series of calculations is performed to find the late-start and the late-finish times for eachactivity. These calculations, called the backward pass, start at the project end and proceed backwardthrough the network, going from right to left in Figure 5.1. The late activity times to be computed arethe latest times at which the several activities on the highway bridge can be started and finished withproject completion still achievable in 70 working days. The supposition during the backward pass is thateach activity finishes as late as possible without delaying project completion. The LF value of eachactivity is obtained first and is entered into the lower right portion of the activity box. The LS, in eachcase, is obtained by subtracting the activity duration from the LF value. The late-start time is then shownat the lower left. Small sections of Figure 5.1 are used in Figure 5.3 to help illustrate the numericalprocedures.The backward pass through Figure 5.1 is begun by giving activity 420 an LF time of 70. Figure 5.3a showsthe value of 70 entered in the lower right of activity 420. The LS of an activity is obtained by subtractingthe activity duration from its LF value. Activity 420 has a duration of zero. Hence, the LS of activity 420 isits LF of 70 minus its duration of zero, or a value of 70. This value of 70 has been entered at the lowerleft of activity 420 in Figure 5.3a. Again, this is a trivial calculation, but it is customary to end precedencediagrams with a single closing activity. Continuing with Figure 5.3a, activity 410 immediately precedesactivity 420. In working backward through the network as shown in Figure 5.3a, the latest that activity410 can finish obviously is controlled by the LS of its succeeding activity, 420. If activity 420 must startno later than day 70, then activity 410 must finish no later than that same day. Consequently, activity410 has an LF time equal to the LS of the activity following (420), or a value of 70. With a duration of 6, ithas an LS value of 70-6, or 64. These values are shown on activity 410 in Figure 5.3a.Figure 5.3Highway bridge, backward-pass calculations
  • 72. Figures 5.1 and 5.3b show that activity 400 immediately precedes activity 410. The latest that activity400 can finish is controlled by the LS of its succeeding activity, 410. If activity 410 must start no laterthan day 64, then activity 400 must finish no later than that same day. Consequently, activity 400 has anLF time equal to the LS of the activity following (410), or a value of 64. With a duration of 1, it has an LSvalue of 64-1, or 63. These values are shown on activity 400 in Figure 5.3b.Figures 5.1 and 5.3c disclose that activity 390 is preceded by three activities: 360, 370, and 380. The LFof each of these activities is set equal to the LS of activity 390, or day 60. Subtracting the activitydurations from their LF values yields the LS times. The LS times for activities 360, 370, and 380 are,correspondingly, equal to 57, 55, and 59. These values have been entered in Figure 5.3c.Some explanation is needed when the backward pass reaches a burst activity (one that has more thanone activity immediately following it). In Figure 5.1, activity 350 would be the first such activity reachedduring the backward pass, and this activity is followed immediately by activities 360 and 370. To obtain
  • 73. the late finish of activity 350, the late starts of the immediately succeeding activities are noted. Theseare obtained from Figure 5.1 as 57 for activity 360 and 55 for activity 370 and are entered into Figure5.3d . Keeping in mind that activity 350 must be finished before either activity 360 or 370 can begin, it islogical that activity 350 must be finished no later than day 55. If it is finished any later than this, theentire project will be delayed by the same amount. The rule for this and other burst activities is that theLF value for such an activity is equal to the earliest (or smallest) of the LS times of the activities thatfollow.The backward-pass computations proceed from activity to activity until the start of the project isreached. All that is involved is repetition of the rules just discussed. In making actual networkcalculations, of course, the LF and LS values would be calculated directly on Figure 5.1, with the timesbeing entered into the activity boxes as they are obtained. The reader is encouraged to verify all of theearly and late activity times shown in Figure 5.1 as a test of how well the rules of computationalprocedure have been mastered. 5.11 Total FloatExamination of the activity times appearing in Figure 5.1 discloses that the early and late-start times(also early- and late-finish times) are the same for certain activities and not for others. The significanceof this fact is that there is leeway in the scheduling of some activities and none at all in the scheduling ofothers. This leeway is a measure of the time available for a given activity above and beyond itsestimated duration. This extra time is called float, two classifications of which are in general usage: totalfloat and free float.The total float of an activity is obtained by subtracting its ES time from its LS time. Subtracting the EFfrom the LF gives the same result. Once the activity times have been computed on a precedencediagram, values of total float are easily computed and may be noted on the network if desired. This hasnot been done on Figure 5.1, however, in an attempt to keep the figure as simple as possible. Referringto Figure 5.1, the total float for a given activity is found as the difference between the two times at theleft of the activity box or between the two at the right. The same value is obtained in either case. Anactivity with zero total float has no spare time and is, therefore, one of the operations that controlsproject completion time. For this reason, activities with zero total float are called critical activities. Thesecond of the common float types, free float, is discussed in Section 5.13. 5.12 Critical PathIn a precedence diagram, a critical activity is quickly identified as one whose two start times (ES and LS)at the left of the activity box are equal. Also equal are the two finish times (EF and LF) at the right of theactivity box. Inspection of the activities in Figure 5.1 discloses that 18 activities have total float values ofzero. Plotting these on the figure discloses that these 18 activities form a continuous path from projectbeginning to project end; this chain of critical activities is called the critical path. The critical path usuallyis indicated on the diagram in some distinctive way, such as with red or bold lines, which are used inFigure 5.1.Inspection of the network diagram in Figure 5.1 shows that numerous paths exist between the start andend of the diagram. These paths do not represent alternate choices through the network. Rather, eachof these paths must be traversed during the actual construction process. If the time durations of theactivities forming a continuous path were to be added for each of the many possible routes through thenetwork, a number of different totals would be obtained. The largest of these totals is the critical orminimum time for overall project completion. Each path must be traveled, so the longest of these pathsdetermines the length of time necessary to complete all of the activities in accordance with theestablished project logic.If the total times for all of the network paths in Figure 5.1 were to be obtained, it would be found thatthe longest path is the critical path already identified using zero total floats and that its total timeduration is 70 days. Consequently, it is possible to locate the critical path of any network by merelydetermining the longest path. However, usually this procedure is not practical. The critical path normallyis found by means of zero total float values. It needs to be pointed out that the scheduler can be badlyfooled by attempting to prejudge which activities will be critical or to locate the critical path byinspection. Critical activities are not necessarily the most difficult or those that seem to be the mostimportant job elements. Although there is only one critical path in Figure 5.1, more than one such path
  • 74. is always a possibility in network diagrams. One path can branch out into a number of paths, or severalpaths can combine into one. In any event, the critical path or paths must consist of an unbroken chain ofactivities from start to finish of the diagram. There must be at least one such critical path, and it cannotbe intermittent. A break in the path indicates an error in the computations. On the highway bridge, 15of the 40 activities (exclusive of start, contingency, and finish), or about 38 percent, are critical. This isconsiderably higher than is the case for most construction networks because of the small size of thehighway bridge. In larger diagrams, critical activities generally constitute 20 percent or less of the total.Any delay in a critical activity automatically lengthens the critical path. Because the length of the criticalpath determines project duration, any delay in the finish date of a critical activity, for whatever reason,automatically prolongs project completion by the same amount. Thus, identification of the criticalactivities is an important aspect of job scheduling because it pinpoints those job areas that must beclosely monitored at all times if the project is to be kept on schedule. 5.13 Free FloatFree float is another category of spare time. The free float of an activity is found by subtracting its EFtime from the earliest of the ES times of the activities directly following. To illustrate how free floats arecomputed, consider activity 260 in Figure 5.1, which shows the EF time of activity 260 to be 35. Activity320 is the only following activity. In this simple case, the free float of activity 260 is the differencebetween the ES of activity 320 and the EF of activity 260, 43-35 = 8 days. When an activity has morethan one following activity, the following activity with the earliest ES time controls. An example isactivity 90 with an EF time of 6. It is followed by activities 110 and 120 with ES times of 15 and 6,respectively. The free float of activity 90 is therefore 6-6 = 0 days. Another example could be activity 270,which has an EF time of 37. The earliest ES date of the following activities, 360 and 370, is 55. Thus,activity 270 has a free float value of 55-37 = 18 days. As an alternate statement of procedure, the freefloat of a given activity can be obtained by subtracting its EF (upper right) from the smallest of the ESvalues (upper left) of those activities immediately following.The free float of an activity is the amount by which the completion of that activity can be deferredwithout delaying the early start of the following activities or affecting any other activity in the network.To illustrate, activity 270, which has a free float of 18 days, can have its completion delayed by up to 18days because of late start, extended duration, or any combination thereof, without affecting any othernetwork activity. 5.14 Activity Time InformationInformation concerning activity times and float values can be presented in three ways: on the networkdiagram itself, in tabular format, and in the form of bar charts. Using the precedence diagram of thehighway bridge as a basis, the preceding sections presented the manual computation of activity timesand floats. When such computations are made, they are almost always performed directly on thenetwork. This procedure is faster, more convenient, and conducive to greater accuracy.To serve a variety of purposes, activity times and floats can be presented in table form, as has beendone in Figure 5.4. Such a table of values serves to collect pertinent time information of the project intoa form that is useful and convenient. In the figure, column 2 lists the activity numbers as they appear inthe precedence diagram of Figure 5.1, with the critical activities appearing in boldface type. The activitynumbers listed in column 3 are used in conjunction with Appendix D, where arrow notation is discussed.Activity time data presented in bar chart form are widely used for project time control purposes duringthe construction process. Project time information in the form of bar charts is discussed in Section 5.29. 5.15 Float PathsAll paths through the diagram in Figure 5.1, except the critical path, have summations of activity timesless than 70 working days and are called float paths. The longest float path, or the one with the leastfloat, can be determined by referring to the total float values of Figure 5.4 and noting that one activity(360) has a total float value of only two days. This indicates that the next longest path through thenetwork is 70−2 = 68 working days. Reference to Figure 5.1 will show that this path is the same as thecritical path except that activity 360 is substituted for activity 370. This path is said to have a float valueof 2. The total float values of 3 in Figure 5.4 indicate that the next longest path through the networktotals 67 days. As a matter of fact, there are two different paths through the network, each with a
  • 75. cumulative time total of 67 days or with float times of 3. Float paths can be located by linking activitieswith the same total floats together with critical activities as needed to form a continuous chain throughthe entire diagram.Figure 5.4Highway bridge, activity timesWhen beginning a backward pass through a construction network, an established target duration for theproject may be used for the “turn around†rather than the EF of the terminal activity. In such acase, it is possible for all paths through the network to be float paths. To illustrate, suppose that thebackward pass through the highway bridge, Figure 5.1, had started with the LF of terminal activity 420equal to 74 rather than 70. The effect of this on the values shown in Figure 5.4 would be to increase allof the late activity times (columns 7 and 8) and all of the total float values by the constant amount of 4.In this case, there would be no activities with zero total floats. Nevertheless, there is still a critical path:the float path with a minimum and constant total float value of 4. This path would be the same as theoriginal critical path. The only difference is that each critical activity would now have a total float of 4rather than zero. In a similar manner, if 67 had been used as the LF of terminal activity 420, all lateactivity times and total floats would be reduced by 3. In this case, the critical path would have aconstant total float of -3 and would be the same critical path as that originally found.
  • 76. The concept of shared float is of importance. The notion of float on construction projects is oftenmisunderstood and, if not monitored and controlled, can become a source of conflict. Although thedelay of an activity from its early-start position by a duration equal to less than its total float will notimpact the overall project duration, it consumes float from each of the paths of which it is a member.Therefore, the use of float by one activity reduces the amount of float available to other activities.Activity total float is shared by every activity on its corresponding paths. Consequently, no single activityhas unilateral ownership of available float. Rather, it must be shared, managed, and distributed as afundamental project resource. 5.16 Early-Start ScheduleAfter the network calculations have been completed, the resulting activity times are used to preparevarious forms of calendar date schedules that are used for project time management. One of these is aschedule of activities based on their early-start and finish times. This time schedule is called an early-start schedule or a normal schedule. The subject of preparing field operation schedules is discussed inChapter 9. The treatment of early-start schedules in this chapter is limited to introducing the generalconcept of project schedules and explaining how expired working days are converted to calendar dates.Activity times obtained by manual calculations are expressed in terms of expired working days. Forpurposes of project monitoring and control, it is necessary to convert these times to calendar dates onwhich each activity is expected to start and finish. This is done easily with the aid of a calendar on whichthe working days are numbered consecutively, starting with number one on the anticipated start dateand skipping weekends and holidays (July 5 and September 6 in our case). Figure 5.5 is the conversioncalendar for the highway bridge, assuming that the starting date is to be Monday, June 14. Calendardates appear in the upper left-hand corner of each box, and working days are circled.The reader is reminded at this point that each major portion of the Example Project is described andscheduled using its own unique planning network. When making manual time computations, each of thenetworks begins at zero expired working days. It is at this stage of conversion of expired working days tocalendar dates that the time relationships among the various networks are established. There is adifferent calendar similar to Figure 5.5 for each network; from this calendar, its unique calendar datetime schedule is obtained.Figure 5.5Highway bridge, conversion calendar
  • 77. When making up a job calendar, the true meaning of elapsed working days must be kept in mind. Toillustrate, the early start of activity 180 in Figure 5.4 is 25. This means this activity can start after theexpiration of 25 working days, so the starting date of activity 180 will be the morning of calendar datenumbered 26. From Figure 5.5, working day 26 equates to the calendar date of July 20. There is no suchadjustment for early-finish dates. In the case of activity 180, its early-finish time is 29, which indicatesthat it is finished by the end of the twenty-ninth working day. Hence, from Figure 5.5, the early-finishdate of that activity will be the afternoon of July 23.It has been mentioned previously that calendar date information concerning network activities can bepresented in different ways, depending on how the data will be used. Figure 5.6 (see insert betweenpages 88 and 89) shows one way in which computers can enter the early-start and finish dates of theindividual activities on the precedence diagram for the highway bridge. 5.17 Tabular Time SchedulesWhen the computed activity times are converted to calendar dates, this schedule information often ispresented in a tabular format. The table in Figure 5.7 is the early-start schedule for the highway bridge,with the activities listed in the order of their starting dates. These calendar dates often are referred to asscheduled or expected dates. Not only is this sort of operational schedule useful to the contractor; italso can be used to satisfy the usual contract requirement of providing the owner and architect-engineer with a projected timetable of construction operations.Whether the contractor prepares activity schedule data in the form of network diagram information oractivity timetables depends on the use for which the information is intended. It is important to note thatalthough tabular reports provide activity numbers, descriptions, schedule dates, and float information,they do not reflect project logic. Tabular reports, such as bar charts, communicate only basicinformation concerning individual activities. They do not communicate the sequence of activities and,therefore, are not diagnostic tools. Only network diagrams have this capability. This fact means that theform of time control information provided to a member of the project management team must beselected to meet the demands and responsibilities of that position.Figure 5.7
  • 78. Highway bridge, early-start schedule 5.18 Activities and Calendar DatesUntil elapsed working days have been converted to calendar dates, there is no accurate way to associateactivities with calendar times. In the case of short-duration work, such as the highway bridge, this hasnot been a problem because it was recognized from the beginning that the work would be done duringthe summer months. However, on projects requiring many months or years, it is important to associategeneral classes of work with the seasons of the year during which the work will be performed. Thegeneral time schedule developed during project cost estimating has provided guidance in this regard.Nevertheless, this preliminary construction schedule is at best approximate and may be altered duringproject planning. Consequently, the first version of the working job calendar must be examined with theobjective of comparing activities with the weather expected during their accomplishment. This perusalmight well disclose some activities that should be expedited or delayed to avoid cold or wet weather,spring runoff, or other seasonal hazards. It may reveal a need for cold-weather operations hithertounanticipated. It can be a good guide for the final inclusion of weather contingency allowances. 5.19 Calendars for WeatherEstimating and presenting the effect of weather on construction processes is a difficult task and requiresboth knowledge of the geographic location in which the work is to be performed and specific experience
  • 79. with the kind of construction operations considered. Several methods are currently in use for estimatingthese effects and adding them to the project plan. As discussed, a contingency may be added to theschedule to account for probable weather delays. This contingency can be either added to specificactivities or combined generally and placed at the closure of a string of operations.A preferred method for presenting weather effects is through the use of weather calendars. Bydetermining the expected number of days lost to weather per calendar month and then removing thosedays randomly from the work calendar, the scheduler may indirectly extend the duration of the affectedactivities by the number of days removed from the calendar. Using this same technique, the schedulermay prepare various levels of weather-affected calendars and assign the individual activities to thembased on the operation’s sensitivity to the environment. As an example, consider two activities onthe highway bridge project that have differing sensitivities to weather: activity 90, “Excavateabutment #1,†and ac vity 370, “Paint.†While abutment excava on may con nue un l 2inches of rain has fallen within a 24-hour period, the more sensitive painting operation must besuspended if more than 1 inch of rain falls. Historical weather records for this project location indicatethat five days in January receive more than 1 inch of rainfall and three days receive more than 2 inches.In response, the scheduler can prepare two separate weather calendars: one for highly sensitiveoperations such as painting and another for less sensitive operations such as abutment excavation.Activity 90 then would be assigned to the first calendar while activity 370 would be assigned to thesecond. Consequently, each of these operations will be halted during the days removed from theirrespective weather calendars. This causes the activity to take a commensurately longer period tocomplete.This method of accounting for weather effects is particularly powerful as it automatically adjusts forlarge changes in the schedule. If an activity is originally scheduled for performance during the winterand later is rescheduled for summer, the seasonal effect of weather is accounted for andcommensurately adjusted without the scheduler’s intervention. Additionally, this method withstandsthe close scrutiny of owners and public authorities that frequently are concerned with the amount ofcontingency added to construction schedules and the computational methods supporting them. A moredetailed handling of weather delays is included in Chapter 12. 5.20 SortsTo serve a variety of different purposes, network activities can be listed in several different manners.The ways that activities are grouped together, or the order in which they are listed, are called sorts orfilters. Sorting provides emphasis on different criteria and makes different forms of information easierand quicker to find. Computers have the capability of sorting large numbers of activities quickly andaccurately. By sorting activities on different bases, different forms of useful information becomeavailable to project management personnel. Various types of sorts are described next.• Activity number sort. In this case, the activities are listed in ascending order of their assignednumbers, as was the case in Figure 5.4. This sort eases going back and forth from the network diagramto the activity data. With the activity number from the diagram, the schedule dates and float values arequickly found from the corresponding activity number in this sort listing.• Early-start sort. Listing activities in the calendar sequence of their earliest possible start times is anoptimistic schedule and is commonly used by project field personnel. Figure 5.7 is an example of thistype of sort. Although it is unlikely that all activities will be started by their early-start dates, such alisting does serve as a daily reminder. It focuses attention on the necessity of meeting these dates in thecase of critical activities and on the fact that little time slippage can be tolerated with low-float activities.It also keeps field supervisors aware that float is being consumed by those activities whose beginningsare delayed beyond their early-start dates. Such schedules are also desirable for vendors andsubcontractors who are responsible for providing shop drawings, samples, and other submittalinformation. Design professionals should also work from an early-start schedule so that such submittalswill receive their timely attention.• Late-start sort. The late start of an activity is the time by which it must be started if the project isnot to be delayed. Failure of an activity to start by its late-start date is the first indication that theproject may be in time trouble.
  • 80. • Late-finish sort. A late-finish sort—one in which the activities are listed in the order of their latestallowable finish dates—is a convenient monitoring device. If an activity has not been finished by itslate-finish date, the project is automatically behind schedule, according to the established action plan.• Total float sort. A listing of activities in the order of their criticality—that is, in ascending order oftotal float values—can be very helpful to job management in pinpointing those areas where timelycompletion is of top priority. Figure 5.8, which is a partial listing of the activities of the highway bridge,brings into sharp focus the identity of those activities that require the closest attention insofar as timelycompletion is concerned. Those activities appearing at the top of such a list can be given the specialattention they deserve. If the timing of an activity begins to slip as the project progresses, its float willdecrease and it will move up the list on this type of report.• Project responsibility. Each network activity can be assigned the name of the organization or personresponsible for its timely completion. Some activities will be assigned to the general contractor, whileothers are the responsibility of a named subcontractor, the owner, or the design professional.• Combined sorts. A valuable aspect of sorting lies in combining sorting criteria. For example, sorts canbe produced that will provide a specific job supervisor of a named contractor with a listing of thoseactivities for which he is responsible. These activities can be ordered by early start and be limited tothose activities that are scheduled to begin within the next 30 days. With this kind of sorting capability,it is possible to provide specific information to each of the people and organizations that share theresponsibility for timely project completion.The preceding discussion is intended to give the reader insight into the types of sorts commonly usedand the project management uses to which they are put. It is possible to list many types of projectinformation for use by different members of the management team.Figure 5.8Highway bridge, total float sort 5.21 Lags between ActivitiesAll previous discussions of project planning and scheduling have been on the basis of two importantassumptions. One is that an activity cannot start until all the immediately preceding activities have been
  • 81. completed. The other is that once all preceding activities have been finished, the following activity canimmediately start. Although these assumptions are more or less true for most network relationships,there are instances where they are not. Consequently, a more flexible notation convention has beendeveloped that can be used to show these more complex activity relationships. Such a system involvesthe use of lags between activities.Figure 5.9 presents several examples of the use of lags. Unfortunately, nomenclature in this area is notstandardized, and “lead times†.T fw v k f .A “ g †, “ †.I , g .L g g w v , g v , z v . If g , z . I ff , g v g .Figure 5.9L g ,
  • 82. I v v w Fg 5.9 g w g .T j g g .T v w fg , g 1 g 8, w f w - kw - f w w ff v .Diagram 1. This figure shows that the succeeding activity 190 can start no earlier than the completion ofactivity 180. Here, no value of lag time is indicated, which means a value of zero, or that there is no lagbetween the finish of activity 180 and the beginning of activity 190. This figure indicates that the wallconcrete can be poured immediately after the wall forms have been completed with no delay inbetween. This is the usual form of activity dependency and is the only one that has been used in thenetwork diagrams presented thus far in this text.
  • 83. Diagram 2. This figure indicates that activity 200 cannot start until three days after activity 190 has beencompleted. This condition is reflected in the time calculations by making the early start of activity 200equal to the early finish of activity 190, plus the time delay of three days, or a value of 46.Diagram 3. The dependency arrow in this figure shows that activity 120 can start no earlier than thestart of activity 110. Since there is no lag value shown (hence a value of zero), activity 120 can startimmediately after the start of activity 110. In this case, the ES of activity 120 is equal to the ES of activity110.Diagram 4. This figure shows that after one day of stripping wall forms, the cement masons can startpatching and rubbing the wall surfaces. The ES of activity 210 is made equal to the ES value of activity200, plus one day of lag, for a value of 47.Diagram 5. Here the finish of activity 270 occurs immediately after, but only after, the completion ofactivity 260. In this case, the EF of activity 270 is made the same as the EF of activity 260.Diagram 6. This diagram shows that the finish of activity 180 follows the completion of activity 170 bythree days. In the time calculations, activity 180 will have an EF equal to the EF value of activity 170, plusthe three days lag, for a value of 41.Diagram 7. The start-to-finish dependency shown here indicates that the finish of activity 90 is achievedtwo days after the start of activity 50. Two days following the start of activity 50 will be its ES (10 expiredworking days) plus the delay of two days, or a value of 12 for the EF of activity 90.Diagram 8. The combination of lags shown indicates these conditions: The start-to-start lag of one dayindicates that tying reinforcing steel can start one day after the wall forming has begun. The finish-to- nish dependency of 1 (note that this lag is minus and could be described as a lead me of +1)indicates that the placing of wall forms cannot finish until one day after completion of the reinforcingsteel placement.Any construction network involves many simplifications and approximations of reality. Certainly amongthese is the usual assumption that an instantaneous transition occurs between a completed activity andthose that immediately follow it. It is undoubtedly true that most sequential transitions betweensuccessive activities on actual construction jobs involve either some overlapping or some delay betweenthe finish of one and the start of the next. Absolute precision in making up project networks wouldnecessitate the widespread usage of lag relationships, which would complicate the planning andscheduling process substantially with little gain in management efficacy. For this reason, lag times arenot used extensively except where the time effects are substantial or for special construction types. Theuse of lags is especially convenient when working with long strings of simultaneous and repetitiveoperations, which is demonstrated with a pipeline relocation example. 5.22 Pipeline Scheduling ComputationsNetwork computations for projects that involve repetitive operations proceed in precisely the samemanner as for any other project. Figure 5.10, which depicts the same job logic as Figure 4.5, illustratesthe determination of activity times for the pipeline relocation discussed in Section 4.14. In actualpractice, the contractor undoubtedly would have the crews and equipment in better balance thanindicated by the activity times used in Figure 5.10. In other words, the times to accomplish a mile oflocation and clearing, a mile of excavation, and a mile of the other operations would be about the same.This fact obviously would help to prevent the undesirable situation of having one operation unduly limitanother with attendant wasted time and loss of operational efficiency. The activity times used in thefigure were selected for purposes of illustrating the generality of the procedure. The bold lines in thefigure constitute the critical path, located by those activities with zero total float.Figure 5.10Pipeline relocation, precedence diagram time compulations
  • 84. 5.23 Pipeline Summary DiagramSummary diagrams for repetitive operation projects are of particular importance. For example, supposethe pipeline in Figure 5.10 were 20 miles in length rather than 5. A detailed figure like Figure 5.10 for theentire project length would be impossibly large. Figure 5.11 is a condensation of Figure 5.10 obtained byusing lag notation. Figure 5.11 shows all 5 miles of each individual operation as a single activity box andis of a type that lends itself well to long strings of repeated operations. For example, activity 10 in thisfigure represents the locating and clearing of the entire 5 miles of right-of-way and has a duration of 5days. In a similar manner, activity 20 represents all the excavation and has a total time duration of 20days. The other four job operations are shown in a similar manner. As explained previously, excavationand string pipe can proceed simultaneously with one another following location and clearing.Figure 5.11
  • 85. Pipeline relocation, summary precedence diagramTo discuss the activity time computations with regard to Figure 5.11, reference is made to activity 40,which may be considered typical.1. Computation of ES. The ES of activity 40 is computed twice. One possible value is the ES of activity 20added to the delay of 4, giving a value of 5. The other is the ES of activity 30 added to the delay of 2, or avalue of 3. Since activity 40 cannot start until four days after activity 20 has started and two days afteractivity 30 has started, it is most severely restrained by activity 20 and, therefore, has an ES of 5.2. Computation of EF. The EF of activity 40 is computed three times. First, the addition of the EF ofactivity 20 to the delay of 5 gives a value of 26. Second, adding the delay of 5 to the EF of activity 30yields 16. Third, adding the ES of activity 40 to its duration of 25 gives 30. The largest value (30) is the EFvalue.3. Computation of LF. The LF of activity 40 has only one possible value. This is computed by subtractingthe lag of one day from the LF of activity 50, giving a value of 30.4. Computation of LS. The LS of activity 40 has two possible values. First, the duration of activity 40 is 25.Subtracting this from its EF value of 30 yields 5. Second, the LS of activity 50 is 22. Subtracting the five-day lag from this gives 17. The LS of activity 40 is the smaller of 5 and 17, or a value of 5.The use of such a summary diagram can sacrifice much of the internal logic. Reference is made to thelocation of the critical path in Figure 5.11, which does not reveal the same level of detail as does Figure5.10. To illustrate this point, it should be noted in Figure 5.11 that summary activities 10 and 20 haveequal values of ES and LS. However, there are different values of EF and late LF. These values indicatethat part, but not all, of the €œLocate & clear sequence € €œEx €s qu 2 r r l. I ms l s, s summ r s w mu
  • 86. s qu s r l. T b l l F gur 5. m r l s ws p rs s w w rks qu s r r l. Fur r s u w ll s l s l rs rs ur s 2 r r l. T mpu rl l m s r 4 r €œL p p € s qu s r l, w s b b l l r u r b x. 5.24 Interface ComputationsI S 4. 5, p p l r ss g s ru ur w rk r s w pp l r l w rk w s s uss . T w rk r pp l r ss g s ru ur , w slml 3 pp l r l r g - -w , s s w F gur 5. 2. T r g sb w s w w rks r F gur 5. 2 7 F gur 5. . I sb r ss g s ru ur mus b r p pp b m p p -l g p r mpp l r s .T rr l s pb w w r g s s s bl s sm r. R r F gur 5. s ws 7 s EF = LF = 2 , w m s r ml pp l w ll b l pl b l ps w rk g 2 . T s s mpl s s r ss g s ru ur mus b bl p pp F gur 5. 2 b l r 2 l psw rk g s. T us, LS r F gur 5. 2 s s qu l 2 . W s s , ms ul s r b pp l r ss g s ru ur r m s g r r s m b s s.T LS lu 2 sb r r F gur 5. 2 rw r p ss mpl r m p . A b kw r p ss r ug r ss g w rk s w p r rm ,s w g LS lu rs s 3. T s lu s g s s ru r ss g s ru ur mus bs r l r b g g ur m =3 r ss g s b r r ppw s . T s ll ws r m s m m s l sb g us rb pp lr l r ss g s ru ur , s, z r m s s m rb .M k g rw r p ss up , us g ES F gur 5. 2 qu l z r , l s ES EF m s s w .T l l lu s r ls b rm r s w F gur 5. 2. Asb s , r s u us p r ug w rk r m w s l l 3. T s l p s r lp r pr j . T s g l lu 3 s , r ss g s ru ur s s r s m m s m pp l m = , l g sp r ug w rk s 3 s sp r m ss w .I r gg sr s blsm l , r ss g s ru ur s ul b r r pp 7 w rk g s, r 3 s rr l pp l s l . I r ubl s l p r ss g s ru ur , g r l m g3 s sb pr .I EF 7 F gur 5. lu 6r r 2 , ll LS LF lu s F gur5. 2 w ul b 4 s l ss s s w .T LS w ul b 2 , g r ss g s ru ur w ul b s r b r m pp l r ss g s br m .Figure 5.12Pp l r ss g s ru ur , pr gr m m mpul s
  • 87. 5.25 Hammock ActivityA us ul p w r g r r w g pr j gr ms s mm k , x s r m r bu s s m m ur s w .I susu l s s b us s m sum g r qu r s r s ur s, bu s ur s r ll b s w ur bu b w sb w w sp s. I s ES LS m s r rm bpr ss r , s EF LF m s r b su ss r . C mm x mpl s mm k s r w r g ul r m , s ru p r sw s msp s r s l - mp s bu r b rj b rs.As sp llus r , supp s s ru g w br g w r l rss r m ur g s ru b k ll g bu m s. R r F gur 5. s wss r m mus b r pr r s r 9 , €œEx bu m # , € b
  • 88. r m l r mpl 3 , €œB k ll bu m #2. € F gur 5. 3 llus r s w mm k 35, €œM sr m rs , € w ul sp m r lb w 25, €œD r s r m, € 275, €œR m sr m rs . € A 35 s r s m r qu r m s w ; s rm r l b s 25 s r 275. A r g urr pl s ul , ur 35 r w r r m 34 43 w rk g s lu s b r m s r s m s s F gur5. 3 .Figure 5.13Hg w br g , mm kJ b r s g x mpl mm k .T s j b r sr l r l ur pr j .I C p r , pr j s s r ss g w rk s mm k u rj b r s s b m s mp r . 5.26 MilestonesMl s s r p s m b s b g mp r rm r rp s ur g mpl s m w rk. M l s s lu s mp s b w r r s g r sks s w ll s rg ss b r r r mpl g rs gm s w rk. A m l s s usu ll s ul r r s r r mpls m ul r mp r sp pr j . O l rg pr j s, r rs r qu l s bl ss r s ml s s x g r ug u pr j us s sr r p s r pr jm r g.E s, r p s m , pp r s su us m r pr gr m. N r l ss,ml s s b s w pr j w rk, s ul pr j m g m sr s. T usu l s s w s z r m ur b x ppr pr l w gr m. I s m s g m r gur s pr rr , r l s, ls, r gl s, r rs p s bus . A rm p r g ml s s r b us ul m b r . Tllus r w ml s b pr w rk, supp s rg r g w br g j b s w bu m s b mpl b k ll s w r l w w r b g sp b br g s l g r p l pr bl m. F gur 5. s ws s p m sr w mpl 3 . A s mb l mm l us r p gml s s pr gr ms s s w F gur s 5. 5.6 s s r s s. 5.27 Time-Scaled NetworksT r g l pr j w rk s rr g s w s s g r l r r r mpl s m bu s pl m s l . A m -s l w rk s s m s g s r r gul r gr m r r ppl s b us pr s gr p lp rr l mr l s ps m g s s w ll s r s qu l r r. Su pl bl s rm mm l w s r s ul b pr ss p m qu klw r pr bl m r s x s .
  • 89. W r w g m -s l gr m, w m s l s b us : w rk g s l r s.O s l s, urs , mm l r bl r. F gur 5. 4 s s r b w p g s 88 89 s rl -s r s ul g w br g pl w rk g- s l w l rm s ls .T s s s m w rk gr m s F gur 5. , w p rrs m l g s m s ul g rm .F gur 5. 4 s b b pl g ES EF lu s r .A r sl b s ES m , s su l z sb gs r rg s s rz l l g s qu l s s m m ur . E s s w s - m s l l r r s w - m s l b x. V r ls l l s s qu l p r. W s rl - s m pr s rl s s r s ll w g, m r l b w w s, b , r l . Fr l s r s w s rz l s l s F gur 5. 4, m -s l pl s p u m ll l s s l r l .W s r l , s x s rg pp rs. T rz l s l s ls r pr s l l r gr ups r s r gs s, p s s uss S 5.28.T r l ss w F gur 5. 4 r r l r w r s rb g s sw ll s s qu l p s. T um r l lu s r us r l s r ES EF m s rms xp r w rk g s r r sp s.T m -s l gr ms r r s r k g l pr j s l b r qu pm r l g m s m g s r s mr s ur . C p r 8 s uss s s subj l. A w rk pl m s l s ls us ul rpr j lm g m ppl s r m r g l pr gr ss. Summ r gr ms r m g m , w rs, r - g rs r qu l r r w m s l gr m €™s s mpr s r ppl j b k g lu .Ml s s b m -s l w rks us g sr s s mb l. F r x mpl , r gl F gur 5. 4 s 3 s pr usl s uss p m w bu m s b mpl b k ll . 5.28 Nature and Significance of FloatsA pr j w rk pl m s l llus r s l r s ur r l l s. IF gur 5. 4, r lp b su l z s rg u l g r m x g r ug gr m. T rz l s l s l b r g r s l s sb w s b s r r l g .T r l s l l s r pr s p s m g s.U r r ums s b s uss l r p rs, s b r s ul , pr rr p r l s ps r m r s su l pr s mm g .T llus r ur r l , s r 3 F gur 5. 4. T s s ur r rs l r s. F gur 5. 4 l rl s ws l s x w rk g s r l bl mpl s s .W s w m b u r s 43 49 , sb l s r g, s ur r s , r mb w ,w u s urb g r . F r ll pr l purp s s, 3 b r s b us b r u sl g b m b k r wr sxu s l g. T r r , r l s x r m ss w b us r sum w u g rl -s r m su g .T ur l l ls b u rs r m su F gur 5. 4. F r x mpl , 3 ls s l l r s. I mpl s w r b l b r s,w ul b m r l w l p w ul m r l z r lp .I ll ws r m s m sr w r l s us r g , l l s ls us s m m u .I m s s s, w r, ur l l s s r bl m r l x mpl jusg . T pr bl m w l l s s r gs r ggr g s s usu ll s r . Tm ss r l g p sw us g l l , mus m w l gr ups
  • 90. s s u .T m -s l pl s b ss r g s, bu pr ss b m l m s.T llus r m r mpl x s , r r sm F gur 5. 4 s3 , , 3 , 5 , 7 , w s l l r s. T s s, s gr up, mb l xbl r s. I r s r l s g mpl s s s r g, r s l xbl r g , r s l l r all five activities are consumed, anda new branch on the critical path is formed through activities 30-110-130-150-170. Figure 5.1 shows thatactivity 190 must follow activity 170. Consequently, when activity 170 moves three days to the right,Figure 5.14 reveals that activities 190, 210, and 230 do likewise. Thus, all floats of these three activitiesare reduced from 8 to 5 and the free float of activity 140 is increased by 3 to a value of 4.This discussion shows that the total float of an activity is the length of time that the early finish of theactivity can be delayed and not adversely affect project completion. If all of the total float of a givenactivity is consumed, accidentally or by design, the activity becomes critical and a new critical path, orbranch thereon, is created in the network. In this new critical path, all the activities prior to the givenactivity must be completed by their EF times and all activities following will begin at their LS times. 5.29 Bar ChartsBar or Gantt charts, briefly discussed in Section 3.9, present the project schedule plotted to a horizontaltime scale. The bar chart has been a traditional management device for planning and schedulingconstruction projects. However, bar charts have serious and well-recognized shortcomings when usedfor the original development of project management information. For one thing, the interdependenciesamong activities are difficult to show and often are not reflected in the data generated. Additionally, thebar chart in itself does not provide a basis for ascertaining which activities are critical and which arefloaters. Consequently, each activity receives the same consideration with no indication of wheremanagement attention should be focused. The bar chart is not an adequate planning and schedulingtool because it does not portray a detailed, integrated, and complete plan of operations. Bar charts arecompletely ineffective for project shortening, resource management, and most of the other projectmanagement methods yet to be discussed.However, the unsurpassed visual clarity of the bar chart makes it a very valuable medium for displayingjob schedule information. It is immediately intelligible to people who have no knowledge of CPM ornetwork diagrams. It affords an easy and convenient way to monitor job progress and record projectadvancement. For these reasons, bar charts continue to be widely used in the construction industry. Theuse of bar charts as project time management devices is discussed in Chapter 9. While CPM networksare planning and diagnostic tools, bar charts are visual display devices.Fortunately, it is possible to prepare bar charts on a more rational basis, avoiding their intrinsicweaknesses and incorporating the strengths and advantages of network analysis. This is possible simplyby recognizing that a time-scaled diagram is an elaborate form of bar chart. Most computer programswill create a variety of bar charts based on the logic of the CPM network. Figure 5.15 is an early-start barchart for the highway bridge presenting the programmed schedule for the entire project. For eachactivity, the shaded ovals extend from its ES to EF times (bolded ovals represent critical activities andshaded ovals, noncritical activities). The white ovals that extend to the right of the noncritical activitiesrepresent the total float. Notice that no work is scheduled for weekends or holidays. Milestones can beindicated on bar charts and frequently play an important role in the monitoring of job progress. Themilestone discussed in Section 5.26 associated with the completion of activity 310 is shown as a trianglein Figure 5.15.Figure 5.15Highway bridge, bar chart schedule
  • 91. Single activities may not always be the most desirable basis for the preparation of bar charts. Simplerdiagrams with fewer bars and less detail may be more suitable for high-level management. In such cases,a bar chart can be prepared using larger segments of the project as a basis. In this regard, the concept ofproject outlines involving different degrees of work breakdown can be valuable. This matter wasdiscussed in Section 4.7. Bar charts may or may not include job restraints, such as the time required forthe preparation of shop drawings and for the fabrication and delivery of job materials. In general, suchrestraints are a function of job expediting (see Section 8.18), which is handled more or less separatelyfrom the field construction operations. Because of this fact, restraints that appear on the highwaybridge network are not shown on the bar chart in Figure 5.15. 5.30 Bar Chart for Repetitive OperationsFor repetitive operations, such as the pipeline relocation, a somewhat altered form of bar chart betterrepresents the field schedule information and is in common usage. This type of bar chart is oftenreferred to as a line-of-balance chart. Figure 5.16 illustrates such a chart for the pipeline project. In thisfigure, the horizontal scale is one of distance along the right-of-way while the vertical scale represents
  • 92. calendar time. Figure 5.16 has been prepared on the basis that the pipeline construction will be initiatedon Monday, July 12. Each of the sloping lines represents the work category indicated and is plotted onan early-start basis. Figure 5.10 provides the necessary ES and EF values. A conversion calendar such asthat in Figure 5.5, with the numbering of working days starting on July 12, serves for the translation ofthese early times to calendar dates. The vertical line at Mile 3 in Figure 5.16 represents the constructionof the pipeline crossing structure whose beginning will also be on Monday, July 12. The crossingstructure is scheduled to be ready for pipe by the afternoon of August 3 and to be completed on August11. The scheduled interface between the pipeline and the crossing structure is shown as August 6.Figure 5.16Pipeline relocation, bar chart schedule 5.31 Computer Applications for SchedulingChapter 5 has presented a comprehensive discussion of project scheduling, a process of establishing acalendar-date schedule for the field construction process. For reasons already explained, the schedulingprocedure discussed herein has emphasized manual methods with the objective of developing athorough understanding of the procedures involved and the significance of the project time datagenerated.Realistic job logic and accurate activity duration estimates should result from the project managementteam’s knowledge, experience, intuition, and discerning judgment. It is important to note that thenetwork logic and activity durations so developed provide a graphic and mathematical job model. Thismodel is very powerful in that it allows a manager to look into the future and make project decisionsbased on information from the model. Like all models, the quality of the information obtained is directlyproportional to the accuracy of the model itself. No amount of computing power can change this basicfact.With regard to the mechanical process of project scheduling, however, computers enjoy a distinctadvantage in their ability to make time computations accurately, with great rapidity, and to present thisinformation in a variety of useful forms. As a result, computers are used universally for projectscheduling purposes. Computers can provide the project team with an almost unlimited array of projectdata and graphic representations of network scheduling information. In addition to forward- andbackward-pass calculations, the computer can convert expired working days into calendar dates.Different activities can be assigned to different calendars. For example, maintenance and supportactivities can be assigned to a weekend calendar while construction activities are assigned to a weekdayschedule. Activity lags (Section 5.21) and hammock activities (Section 5.25) are easily incorporated intothe project schedule and a variety of activity sorts are available.
  • 93. Calculations performed by computer can be displayed graphically in the form of project networks (orportions thereof) or in the form of tabular reports. These can be made to cover varying portions of theoverall project and differing periods of time. Computers have the capacity to sort information in termsof specific activities, spans of time, physical location on the site, areas of responsibility, or other desiredcriteria. This capability eases the burden of getting the right information to the right person at the righttime. Computer programs typically have the capability of reducing the network time schedule to barchart form. These work well for reporting job progress to owners, design professionals, and othersconcerned with the construction schedule.Computer programs used for project scheduling can differ substantially from one another in manyimportant respects, and a wide variety of scheduling programs are available. For this reason, care mustbe exercised to select a program best suited to the specific management needs of a given project. Mostof these programs will allow a scheduled time to be assigned for the completion of construction and willmake the backward pass using this designated finish date rather than the value obtained during theforward pass. Scheduled dates also can be assigned to network milestones.Chapter 6 moves from viewing at the project as a whole to planning the details that often areoverlooked and can cause serious job delays.
  • 94. 6 Production Planning 6.1 IntroductionThis chapter revisits the planning process. Chapter 4 considered planning from a project point of view.Project planning of the highway bridge consisted of dividing the project into activities and establishingthe logical relationships between them. This process, along with the project scheduling techniques ofChapter 5, established what was going to be done on the project and when each activity was to beaccomplished.Production planning, however, is concerned with how these activities are going to be accomplished. Ifproject planning is macroplanning, then production planning is microplanning. Production planningestablishes the methods to be used, the assignment of personnel, the movement of material to theworkface, and the process of assembling the pieces. The effort required to plan for production isequivalent to that required for project planning in Chapter 4.Before addressing the fundamentals of production planning, two additional topics of project planningmust be discussed: the planning team and reengineering the project. 6.2 Planning TeamOnce the contract is signed, there is very real pressure on the project team to get on with the work;success often is defined as making the dirt fly. Yet studies show conclusively that complete, thorough,and detailed planning at the beginning of a project is the key to a successful completion.Often the people assigned to a new project have never worked together. The planning process is thefirst opportunity to begin the team-building process. Getting the team together in a planning sessiongives the members an opportunity to work together in an unstructured environment in which every ideais welcome and where an individual’s expertise can identify future problems and solutions.Many constructors find planning to be the hardest part of the construction process. Construction peopleare often more at ease when working with physical objects rather than with abstractions, and planningis an abstract process. There is a great deal of uncertainty at the beginning of a project. This causesfrustration. There is the perception that starting work right away is the best way to come to grips withthe uncertainties. In order to overcome these planning objections, several things can be done to makeplanning less abstract and more satisfying.Working with computers lends structure to the development of ideas, but computers are onlymarginally applicable to the planning process. As discussed previously, the outliner in schedulingsoftware or in word processing software can be used to break a project down into successive layers offiner detail. Using a computer, video projector, and outlining software, the project team quickly beginsto contribute, improve, and agree on how the project is to be organized. Once the outline issubstantially complete, and using the same equipment, the team starts the process of moving theresulting breakdown to the network diagram and establishing the constructive logic between activities.With this process, each idea is placed on the screen, evaluated, and added to the project plan. Althoughnot as physically permanent as concrete and steel, the computer images can be seen and provide avisual record of the planning process.There are a number of important elements in successful planning. First and foremost, the team mustunderstand the project thoroughly. Everyone must be familiar with the type of work being planned andmust fully understand the contract documents. They must bring appropriate skills and experience to theteam, and their abilities must complement each other. Sufficient time must be allotted for the planningprocess. Many successful project teams find it advisable to meet away from the office and constructionsite, thus avoiding interruptions. Sequestering the team for two or three days in a hotel allows theplanning process to go uninterrupted through mealtimes and into the evening. If field work must bestarted immediately, a temporary or mobilization team can be assigned to do the immediate tasks whilethe permanent team completes the planning function.
  • 95. As the project plan develops, the team should bring others into the process. Vital suppliers andsubcontractors should be included in meetings. When appropriate, the suppliers and subcontractorsprepare specialty subschedules to cover their part of the work. These subschedules are presented to theproject team and defended before they are added to the master plan. In this way, suppliers andsubcontractors are made aware of the important part they play in the success of the project.Before the plan is finalized, an analysis of possible risks should be made. This involves an evaluation ofparts of the plan where things are most likely to go wrong. Questions such as “Where are we mostvulnerable to weather damage?†or “Which material is most apt to have delivery or approvalproblems?†are sed to ide y problem areas ce the areas o ris have bee ide ed pla s eed to be made to mitigate a d ma age these ris sHavi g the project team wor together to prepare a complete job pla stre gthe s b y-i a d mea sthat each team member will have developed a stro g se se o dedicatio to the project’s o tcomeS ccess i the pla i g process stre gthe s the project team alig s their objectives a d sets theproject o co rse or a s ccess l co cl sio 6.3 Reengineering the ProjectThere is o te a better way to do thi gs Ree gi eeri g is the process o exami i g a project a d itscompo e t parts i a e ort to i d improved or alter ate ways to accomplish a operatio Thisree gi eeri g process ca be applied to a y part o the project rom the way a piece o eq ipme t isi stalled to the way cha ge orders are ha dled The ey to s ccess l ree gi eeri g is to ide ti yalter ative ways o doi g thi gs A really great idea ca ot be eval ated a d impleme ted i it has everbee s ggestedUsi g the highway bridge as a example ma y o the major ree gi eeri g processes are beyo d therespo sibility o the co tractor For i sta ce a c lvert might have bee proposed i place o the bridgewith co siderable cost savi gs The locatio o the road may have bee rero ted so that a bridge was ecessary b t these cha ges were the respo sibility o the ow er The highway bridge co tractor hasthe respo sibility or the mea s a d methods to be sed i the co str ctio o the bridgeImproveme ts here rest with the project team I order to ide ti y as ma y ew ideas as possible abrai stormi g sessio is the best approachBrai stormi g or co cept al bloc b sti g tech iq es i volves a ree ormat meeti g o the projectteam where a y idea is acceptable This is a meeti g where othi g is sacred a d o o e is right trageo s s ggestio s o te trigger ew a d more practical ideas a d ew ideas are whatree gi eeri g is all abo t The leader o the meeti g sho ld e co rage co ve tio al sol tio s aspeople to q estio the bo dary co ditio s betwee operatio s a d processes a d loo at sol tio s sed i other i d stries Free i hibited thi i g at this stage ca provide ew sol tio s to oldproblems a d provide s bsta tial savi gs i terms o time a d mo ey 6.4 Planning for ProductionProd ctio pla i g i volves site layo t arra geme t o tilities a d preparatio o storage a dpre abricatio areas It i cl des establishi g tra ic patter s or vehicles a d material low patter s romstorage to pre abricatio to i al i stallatio This is a detailed st dy o exactly how the wor is goi g tobe accomplished It is complicated time co s mi g a d extremely importa t I the remai der o thischapter prod ctio pla i g is bro e dow i to its compo e ts a d disc ssed 6.5 Support Planning e o the irst thi gs to co sider is how eq ipme t a d materials will get to the site Typically thero te will i volve p blic roads a d bridges both o which m st be exami ed or alig me t a d capacityWeight a d dime sio limits o roads a d bridges are extremely importa t Heavy or oversize loads mayhave to be ro ted ar o t o the way i order to get them to the site Where bridges will ot withsta dthe loads a d alter ate ro tes are available ords may have to be b ilt aro d the bridge Heavyloads may have to be divided at their so rce i order to get them to the site There may be low tilityli es a d other height or width restrictio s Narrow roads or tight t r s may ca se problems Ide ti yi gthese restrictio s or critical material deliveries i adva ce may save m ch- eeded project time
  • 96. A thoro gh i vestigatio o o -site a d o -site tilities is ecessary S ch eeds as the closest rail sidi ga d doc acility may play a importa t part i getti g materials to the site The eed or water sewergas high-voltage electricity a d three-phase electricity m st be ide ti ied a d so rces o d be orestarti g wor Newer tility req ireme ts may also i cl de hazardo s waste disposal acilitiesgro dwater testi g acilities silt rete tio basi s a d wideba d comm icatio plat orms or voicevideo a d data tra smissio sA detailed drawi g is req ired or e icie t site layo t The mber size a d locatio o job-siteb ildi gs m st be determi ed It is importa t that the job o ice b ildi g be located i s ch a way as toprovide a sec re e try to the site a d have a good view o the wor area ther b ildi gs i cl de o icespace or i spectors a d s bco tractors tool storage b ildi gs cha gi g acilities or employees a dstorage b ildi gs or hazardo s a d lammable materials A tra ic patter or vehicles eeds to beestablished Par i g m st be provided or employees s bco tractors a d visitors Heavy tr c s m sthave clear access to the storage a d wor areasSpeci ic provisio s m st be pla ed or eq ipme t mai te a ce a d eli g material laydow materialstorage a d pre abricatio F el storage a d waste storage also are importa t co sideratio s Fig re6 1 shows the res lti g site pla or the highway bridgeFigure 6.1Highway bridge site layo t 6.6 Technical ProblemsMa y projects i volve tech ical problems req iri g sig i ica t adva ce pla i g Problems o thehighway bridge i cl de dewateri g o the o datio a d placeme t o the cra e or setti g the decgirders Most projects i volve li ti g o heavy materials so cra e capacities a d coverage m st bechec ed Cra e co licts with power li es str ct res a d other cra es o te req ire preparatio odetailed drawi gs Getti g materials a d eq ipme t i to the str ct re o te req ires detailed“path i di g†st dies Re eries power pla ts a d other projects may req ire complex comp terst dies i order to ass re that eq ipme t a d pipi g will it i the locatio speci ied
  • 97. Co str ctio o b ildi gs i dow tow areas req ires detailed pla i g or loadi g a d storage omaterials tra ic patter s a d accommodatio s or pedestria s Deep excavatio s may req ire braci gsheet pili g or other soil stabilizatio tech iq esSome projects have complex wor seq e ces that req ire a detailed st dy to determi e the exactseq e ce o steps to ollow te lo g lead eq ipme t deliveries req ire that certai parts o a projectbe le t accessible til late i the project More a d more projects i volve the se o or disposal ohazardo s materials Wor with these materials req ires oti yi g employees o the hazard a d trai i gwor ers i proper ha dli g tech iq es a d i the se o speci ic tools a d sa ety eq ipme tEarly a d complete ide ti icatio o these tech ical problems allows or proper pla i g Altho gh theproblems remai tech ically di ic lt proper pla i g gives project ma ageme t time to co sideralter ative methods a d bri g i tech ical specialists whe ecessary 6.7 Personnel PlanningThe s ccess o a project is largely depe de t o the q ality a d morale o its cra tspeople Goodpla i g at the begi i g o the job helps ass re s ccess i several ways Cra tspeople i proper mbera d with appropriate s ill levels m st be hired It is importa t that co siste t policies be established a dapplied to all sta Job-site morale ca be devastated whe labor shortages req ire that ew employeesbe give i ce tives ot o ered to earlier employees Co siste t wage rates a d be e it pac ages areesse tialWhere there is a shortage o s illed people trai i g programs have to be impleme ted Wor i g withlocal tech ical-vocatio al schools may help the sit atio -the-job trai i g programs may req iresig i ica t pla i g early i the project Whe the shortage is severe cra tspeople may have to bebro ght i rom other locatio s I this case tra sportatio a d ho si g may be req iredProjects i remote locatio s req ire camp acilities Morale is greatly a ected by the orga izatio o thecamp a d the q ality o the ood Poor camp acilities o te res lt i low morale poor prod ctio a dhigh perso el t r over A highly q ali ied camp ma ager ca be the most importa t perso o theproject ma ageme t team 6.8 Safety PlanningCo str ctio wor is i here tly da gero s Sharp objects heavy loads high places a d emphasis oprod ctio all provide opport ities or accide ts Good pla i g a d the impleme tatio o acomprehe sive sa ety program are ecessary or a sa e project St dies have show that employeei volveme t i a sa ety program is esse tial Establishme t o a sa ety committee d ri g the irst weeo the project is a good way to start a sa ety programThe sa ety committee is ma dated to impleme t a d mo itor the sa ety program Some irms assigthis d ty to all the oreme o the project They meet wee ly review the sa ety program a d co d ct asa ety i spectio I some co str ctio compa ies a di ere t orema is assig ed as the sa etyi spector each wee This orema i spects the project daily correcti g a y sa ety problems observeda d posti g violatio s o the b lleti board Typically a orema will strive harder or sa ety withi hiscrew i a other orema is goi g to i spect his wor area a d report sa ety problems to his peersco rse a Mo day mor i g toolbox sa ety program a d i ce tives or per ect sa ety records are i tegralparts o sa ety pla i gSa ety pla i g i cl des speci ic co sideratio regardi g what to do i case o a accide t Sta with irst aid certi icatio sho ld be ide ti ied I case o a serio s accide t a pla sho ld be i place orma i g 911 calls meeti g the emerge cy medical people a d leadi g them to the victim Emerge cyevac atio rom high i a b ildi g or deep withi a co str ctio project req ires oretho ght Sa etypla i g sho ld co sider a ire a d a evac atio pla te a ire is accompa ied by a power ail reso li ts a d electric cra es are ot available Similarly i a project is s bject to a lood heavy rai or ats ami pla s sho ld irst co sider evac atio o wor ers Seco dary pla s sho ld co sider ways tomi imize damage to the project I all o these cases waiti g til the time o the disaster to assigpeople a d decide what m st be do e will almost certai ly red ce the s ccess o the recovery e ort
  • 98. Wor i high places a d activities i volvi g heavy li ts eed to be ide ti ied i adva ce a d sa ety pla smade Pla s or attachi g barricades a d li eli es a d coveri g ope i gs sho ld be made i adva ceCo crete orms eed to be desig ed or sa ety i cl di g sa e wor s r aces raili gs a d ladders Theseco crete- orm sa ety co sideratio s sho ld apply to placi g movi g strippi g a d clea i g operatio sas well as or placi g co crete Moveme t o large eq ipme t or li ti g heavy loads sho ld be pla ed or a ter ho rs i order to mi imize the mber o people i volvedPla i g sho ld i cl de a process or ha dli g hazardo s materials Material Sa ety Data Sheets (MSDSs) eed to be req ested with all material orders These sheets are to be placed i a oteboo a d madeavailable to employees Wor ers are e titled to ow whe they are ha dli g hazardo s materials a dto be aware o the da gers i volved a d the s ggested ha dli g proced res Special atte tio sho ld begive to wor i e closed spaces where chemicals may orm toxic mes All chemical age ts sho ld beclearly mar ed a d i spected reg larly or co ditioSa ety eq ipme t eeds to be stored i co ve ie t locatio s where it is q ic ly accessible wheoperatio s call or its se A reg lar i spectio sho ld be sched led to ma e s re the sa ety eq ipme ti ve tory is complete a d i good co ditio The availability o sa ety eq ipme t eeds to be advertiseda d its se made ma datoryBeca se o the i here t da gers i volved i co str ctio a y comprehe sive sa ety pla sho ld i cl demethods o e s ri g employees are alert a d dr g- ree This is best accomplished thro gh a well-pla ed dr g-testi g policy a d program Dr g-testi g programs sho ld always be pla ed well iadva ce o co str ctio a d i corporated i to compa y or project hiri g a d employme t policy Thise s res that all employees joi i g the project do so lly aware o the compa y’s dr g policy testi gmethods a d actio able pe alties The policy sho ld state the compa y’s i te tio to operate adr g- ree wor place detail the testi g methods to be applied speci y the i d o s bsta ces to beba ed (s ch as alcohol) a d explai a y pe alties a d assista ce programs The dr g-testi g programsho ld address comp lsory testi g prior to hiri g co ti o s ra dom testi g a d testi g or ca se Theemployme t applicatio process sho ld i cl de ma datory dr g testi g I eed be employees may behired o a probatio ary co tract pe di g the res lts o the test This e s res that all employees joi theproject dr g- ree Ra dom dr g testi g e s res that employees do ot begi si g dr gs d ri g theproject Beca se some projects employ a large mber o wor ers ra dom testi g may o ly cyclethro gh the job every six to eight mo ths red ci g this type o testi g to a deterre t There ore a moreactive testi g method is eeded to ide ti y employee dr g se at its o set To meet this eed a testi gpolicy sho ld allow or immediate dr g testi g with j st ca se a d comp lsory testi g ollowi g a yaccide ts Adva ced pla i g a d p blicatio o the dr g-testi g policy will help deter pote tial sers rom applyi g or wor a d mai tai a dr g- ree a d sa e wor place 6.9 Planning for QualityI today’s co str ctio mar et every project eeds to have a ormalized q ality co trol system iorder to be competitive The co sta t co lict betwee prod ctio a d q ality m st be resolved or as ccess l project Perhaps the most importa t part o a q ality co trol program is the creatio o a job-site c lt re where q ality is as ed or a d expected Cra tspeople eed to ta e pride i their wor a dexpect their peers to do li ewise There are a mber o ways to b ild this visibility a d dedicatio toq ality Part eri g is a good way to start While part eri g is ge erally associated with the co tract ala d orga izatio al aspects o a project it also assists i developi g a better dersta di g o the acilitya d the associated eed or q ality wor ma ship te the architect-e gi eer ca be called o todesig a i spiri g project logo or se o hardhats a d sa ety awards to help b ild pride i the projectve t re A model o the project ca be ept o display i the job o ice a d show to all ew wor ers sothey may better appreciate the co str ctio process a d the team e ort goi g i to the project Someco tractors pla a Sat rday ope ho se rom time to time so that employees’ amilies ca visit thesite a d see the q ality wor bei g do eIt m st be remembered that q ality occ rs at the wor ace ly wor ers have the power to prod ceq ality Ma ageme t m st appreciate that pla i g or co str ctio q ality res lts i t r i g theorga izatio al chart pside dow I a q ality-drive orga izatio al chart each level o separatio romthe wor ace comes with a red ctio i the ma ager’s ability to directly a ect q ality a d ai crease i his wor ace s pport respo sibilities There ore wor ers m st be empowered thro gh
  • 99. programs s ch as Total Q ality Ma ageme t (TQM) a d q ality circles to search o t better ways to get aq ality job do e the ormal side the project team eeds to determi e the req ired tests a d sta dards or the jobRejectio proced res m st be established Every job-site i spectio or whatever p rpose eeds tohave a q ality a d sa ety compo e t i cl ded Special atte tio is req ired to i corporate q alityprograms with s bco tractors The s bco tractor selectio process eeds to be based o q alitypreq ali icatio iss es be ore price is co sidered e last poi t: Q ality does ot apply o ly to the i ished prod ct TQM iss es i cl de the way projectsare pla ed ide ti icatio o problems well i adva ce o co str ctio the rate at which cha ge ordersare ha dled a d the q ality o employee trai i g Every phase o a co str ctio operatio is s bject toco ti o s improveme t 6.10 Material Ordering and ExpeditingMajor materials s ally are ordered withi days o sig i g a co str ctio co tract The material deliverylead time determi es the order i which p rchase orders are prepared There ore special atte tiom st be give to determi i g which materials will req ire the lo gest lead time Preparatio op rchase orders m st be coordi ated with the project sched le s ch that timely delivery dates arespeci ied o the order Q a tity a d q ality req ireme ts m st also be spelled o t i the p rchaseorder The p rchase order sho ld state that the job site is to be give at least 48 ho rs otice o adelivery so that adeq ate preparatio ca be made at the site or o -loadi g i specti g stori g ordirectly i stalli g the materialSimply placi g a p rchase order or materials provides little ass ra ce that the materials will arrive otime Proper pla i g or a material-expediti g system is the best i s ra ce or o -time deliveries Allp rchase orders eed to i cl de a delivery date based o the project sched le Early deliveries caca se problems with storage a d have a adverse e ect o project cash low Late deliveries are worseSpecial atte tio is eeded to e s re that shop drawi gs are prepared chec ed s bmitted or approvala d ret r ed to the ve dor Similarly samples tests mill certi icates a d other doc me ts m st beapproved The co trol system or these s bmittals m st e s re prompt ha dli g at every level ce allapprovals are i place ma act ri g ca begi Fabricatio sched les m st be s ch that i ishedmaterials are ready to be shipped allowi g s icie t time to get to the job site Some materials a deq ipme t req ire i spectio d ri g the abricatio process or testi g prior to shipme t These itemsm st be ide ti ied a d a system m st be i place to oti y the proper i specti g or approvi gorga izatio sWhile ey materials a d eq ipme t are bei g abricated the expeditor sho ld co tact the s pplier orass ra ce that shippi g arra geme ts have bee made te space m st be reserved i adva ce ocommo carriers Bills o ladi g a d i s ra ce also have to be obtai ed i adva ce Some co tractorsreq ire all s bco tractors to s bmit priced p rchase orders to the expeditor This allows theco tractor to co irm that the material has bee ordered a d to assist with the shippi g sched le whetra sportatio disr ptio s occ r As little as possible is le t to cha ceAt the job site the expeditor a d project e gi eer meet reg larly to determi e the c rre t stat s omaterials a d to ide ti y problem areas A y pote tial delay i ma act ri g or shippi g req iresprompt actio i order to avoid delayi g the project The lo ger the adva ce war i g o a material delaythe more optio s there are to wor aro d the problem 6.11 Material Handling, Storage, and ProtectionThe arrival o material at the job site sho ld ever be a s rprise; the exact time o a delivery sho ld beestablished i adva ce U expected deliveries are a disr ptio to wor at the site a d o te the o lyperso available at the time to accept the delivery is q ali ied or the job At the job site a speci icwor er sho ld be assig ed to accept the delivery a d to oversee loadi g This perso eeds to have acopy o the p rchase order i ha d whe the material arrives U loadi g eq ipme t sho ld be availablea d a speci ic place assig ed or storage As the shipme t is loaded it sho ld be i spected orcomplete ess a d or damage A y deviatio s rom the p rchase order eed to be oted o the deliverytic et a d that i ormatio m st be passed o to project ma ageme t
  • 100. Whe wareho si g is req ired a i ve tory co trol system has to be established Care m st be ta ethat materials a d eq ipme t are iss ed to the speci ic i stallatio or which they were orderedExceptio s eed to be approved a d doc me ted so that o e co str ctio operatio does ot sematerials ordered a d eeded by a other operatioWhe ever possible the material or eq ipme t sho ld be moved directly rom the carrier to the i ali stalled locatio I this is impossible or impractical the material sho ld be stored i a locatio that willmi imize ha dli g a d ha dwor It is estimated that ha dli g movi g a d ha dwor acco t or asm ch as 30 perce t o the cost o i stallatio With i adeq ate pla i g material orders are too o tei complete or damaged a d the problem is ot oted til the day o i stallatio I properarra geme ts are ot made waterproo materials may be stored i b ildi gs while weather-se sitivematerials wi d p i the rai or it is determi ed too late that a tre ch m st go directly thro gh theplace where topsoil is stoc piled Detailed pla i g regardi g material ha dli g a d storage savesmo ey a d preve ts ecessary a d r strati g delaysAt times materials m st be stored o -site I this case iss es o title i s ra ce a d payme t arei volved It m st be determi ed whe title cha ges rom the s pplier to the co tractor a d rom theco tractor to the ow er Whoever has title also has i s ra ce respo sibilities a d these m st becoordi ated It m st also be determi ed whe payme t will be d e irst rom the co tractor to theve dor a d the rom the ow er to the co tractor 6.12 Equipment Planning some projects co str ctio eq ipme t co stit tes a major portio o project cost For that reasopla i g the spread o co str ctio eq ipme t the ha l roads where the eq ipme t will operate a dthe mai te a ce acilities that will eep the eq ipme t r i g are o tmost importa ceSelectio o the most appropriate eq ipme t o te m st be modi ied accordi g to the eq ipme tavailable A cost a alysis m st be made o the impact o less appropriate eq ipme t Where additio aleq ipme t is req ired a b y lease or re t a alysis is ecessaryA e icie t eq ipme t mai te a ce pla m st be p t i to place with reg larly sched led preve tivemai te a ce Layo t or the eli g a d mai te a ce yard m st be coordi ated with the other yardareas This area m st provide easy access or eq ipme t a d sho ld be laid o t with sa ety i mi dPla i g m st be do e or e icie t ha l roads matchi g grades to the capabilities o the eq ipme tavailable a d a ha l road mai te a ce pla m st be devised 6.13 Production MethodsAltho gh co str ctio projects are typically o e o a i d it is importa t to pla e icie t assemblyprocesses te s bassemblies ca be pre abricated Ma y co str ctio operatio s le d themselves toassembly-li e tech iq es the highway bridge it is pla ed that the ab tme t orms bepre abricated a d bro ght to the site ready or i stallatioF dame tal to pla i g prod ctio methods is simpli yi g each step o the process This starts withsimpli yi g the drawi gs Co str ctio pla s o te te d to be terse a d diagrammatic Dime sio s aregive o ce Typical details are draw with exceptio s show i a sched le or table High rates oprod ctio req ire that the details be spelled o t or each step o the wor Rather tha havecra tspeople search thro gh the pla s or the locatio o i serts weld plates a d dime sio s thisi ormatio sho ld be show o a shop drawi gWhe co crete col m s are bei g ormed a d po red a letter-size s etch o typical col m s with the ecessary dime sio s a d details sho ld be provided For every o typical col m a separate s etch isreq ired Additio ally a layo t drawi g showi g which col m goes i each locatio with appropriatemar mbers eyi g detailed s etches to the layo t locatio is req ired Not o ly does this simpli y thewor it also simpli ies a q ality co trol chec be ore co crete is placedI str ctio s sho ld be simpli ied to mi imize mis dersta di gs I str ctio s to oreme sho ld beclear co cise a d complete Where appropriate the i str ctio s sho ld be i writi g Ha dwrittei str ctio s are s icie t a d these might be do e o the bac o the s etch described earlier
  • 101. Processes sho ld be simpli ied Brea a process dow i to i divid al steps Exami e each step to see i itca be simpli ied e o the a thors wit essed a press re test o a sewer o t all req iri g 10 eet ohead mai tai ed or 24 ho rs a d losses ot exceedi g 10 gallo s per ho r This test was bei g do ewith a 10- oot sta dpipe sca oldi g a d a gallo b c et sed to ill the sta dpipe This processreq ired co ti o s mo itori g or three shi ts With pla i g the process was cha ged to a watermeter press re ga ge press re red ci g valve a d a hose to the city water s pply The press rereg lator was set to the proper press re a d the water meter was read at the begi i g a d e d o thetestPla i g the co str ctio method will ide ti y processes where assembly-li e tech iq es ca be appliedThis pla i g will i cl de the se o jigs layo t devices power aste i g systems a d mecha icalmethods or movi g materials It will determi e how materials will low thro gh the assembly area Theclassic example is c tti g st ds a d wales or co crete wall orms: The act al time spe t c tti g isi sig i ica t compared with the time spe t movi g material to the saw a d rom the saw to theassembly area The prod ctive sawma has a prepared c tti g list to wor rom a d c t material ismoved to the saw by or li t C t material moves away rom the saw i a similar ma er -site a d o -site pre abricatio ca simpli y the wor i several ways Pre abricatio le ds itsel toassembly li e tech iq es With pre abricated assemblies i stallatio goes aster a d the wor site isless cl ttered Pre abricatio speeds p the process a d acilitates q ality co trol S bco tractorssho ld be e co raged to r ish pre abricated assemblies rather tha doi g all the wor o -site Aadditio al be e it is that shop wor ers o te receive lower wages tha ield employees 6.14 Activity PlanningI order to ass re timely completio o sched led project activities a orema sho ld be assig ed therespo sibility o pla i g or that activity’s s ccess Approximately a wee be ore a activity issched led a mber o details have to be chec ed Are the drawi gs related to this wor complete? Area y cha ges expected? Are the shop drawi gs approved? I the shop drawi gs are bei g preparedseq e tially are they seq e ced to the order i which the wor m st be do e i the ield?I this activity req ires a y special tools or eq ipme t ow is the time to see that they will be availableI tools a d eq ipme t are to be shared with parallel activities a dersta di g is req ired regardi gwho will get them a d whe I the case o eq ipme t ail re available optio s sho ld be ide ti iedAre the req ired materials o -site? Do yo ow where they are stored a d whether they are accessible?I ot o -site how reliable is a timely delivery? Are the materials s bject to bei g o a wro g q alityq a tity or dime sio ? Are all the s pport materials o ha d? Remember “ or wa t o a ailthe shoe was lost â€I spect the wor space Chec o access or eq ipme t a d materials Chec that the area is cl tteredI other wor will be occ rri g co c rre tly wor o t a pla to share the space Chec to see that thelayo t is correct a d that s pport tilities s ch as compressed air electric power a d ve tilatio areavailable Ma e s re there is s icie t light to ass re q ality wor Chec or sa ety hazards a d provide or waste disposal 6.15 Production ChecklistsEach co str ctio operatio i volves a large mber o importa t details With the atte da t co sio oise a d i terr ptio s o a typical project it is easy to overloo importa t details These omissio slead to rewor or which there is either time or mo ey i the b dget Well-tho ght-o t chec lists caprovide a excelle t way to eep trac o the myriad o details that accompa y each co str ctiooperatioChec lists are val able or ma y phases o co str ctio wor Some examples are:ÂPermitti g processPreco str ctio site i spectio
  • 102. Layo t a d excavatioUtility locatioCo crete orm worCo crete lat worPipi gÂFig re 6 2 is a example o a co crete wall a d col m chec listGood chec lists are the res lt o years o experie ce a d are developed by co tractors over a lo gperiod o time Mista es a d omissio s occ r ar too o te b t good co str ctio practice b ilds othese mista es by addi g them o e by o e to the releva t chec list th s decreasi g the cha ce o amista e bei g repeatedIt is easy to ratio alize that co str ctio s pervisors do the same jobs over a d over a d there ore have o eed or a writte chec list It is air to poi t o t however that airli e pilots also do repetitiveoperatio s b t ever start a e gi e witho t re erri g to a writte chec list Mista es o a co str ctioproject ca e da ger ma y lives The co crete chec list show i Fig re 6 2 provides the experie cedco crete orema with a comprehe sive list o items to be chec ed o as wor progresses For thei experie ced orema the chec list provides the i sight s ill owledge j dgme t a d bac gro dthat wo ld otherwise be provided by more experie ced peopleWell-tho ght-o t chec lists help preve t mista es a d omissio s They are also a val able a d time-savi g aid to the q ality co trol perso chec i g the worFigure 6.2Co crete wall a d col m chec list
  • 103. 6.16 Look-Ahead SchedulesThere are two types o loo -ahead sched les First rom a project sched li g perspective the sched leis detailed i a o r- to six-wee rolli g sched le This type o short-term sched le is disc ssed rther iChapter 12Seco d prod ctio short-term or loo -ahead sched les are created by oreme a d show exactly howthe wor will be accomplished Each orema is assig ed a speci ic tas rom the project sched leTypically a loo -ahead sched le is a rolli g sched le a d will cover the ext 7 to 10 days The extexample rom the highway bridge ill strates a typical loo -ahead sched leA carpe ter orema is assig ed the tas o ormi g ab tme t #1 The pdated project sched le showsthis wor to begi A g st 2 which is a Mo day This is a critical activity a d it appears that the ormswill be ready as sched led This orema is also respo sible or strippi g the ab tme t orms romab tme t #1 so the start o wor will ot have to be coordi ated with a y other orema The irst stepis to chec the b dget or the ma -ho rs available a d the sched le to see the time allowedFigure 6.3Highway bridge seve -day loo -ahead sched le
  • 104. The b dget Fig re 3 10 shows that there are 1810 sq are eet o orms to place a d 3 656 labor dollarsto do the wor Si ce the average ho rly labor cost or each member o the crew is $29 00 the oremacalc lates that he has abo t 126 ma -ho rs to get the wor do e Accordi g to the sched le the worm st be completed i three daysPla i g this operatio ca be do e with a simple precede ce diagram or with a bar chart Fig re 6 3 isa bar chart showi g each step o the process a d assig i g crew members to each tas The irst item ithe bar chart clea repair a d oil orms is charged to the previo s acco t strippi g ab tme t ormsThe bala ce o the items i the bar chart shows a total o 136 ma -ho rs j st slightly above the b dgetThe wor is sched led to ta e three days eepi g the project o sched le 6.17 Planning the PaperworkThere is a staggeri g amo t o paperwor associated with a co str ctio project B ildi g a c stomhome ge erates o e or two ile boxes o doc me ts Whe the highway bridge is complete thedoc me ts will ill a o r-drawer ili g cabi et The paperwor or a high-rise b ildi g will ill a o iceKeepi g trac o all these doc me ts req ires pla i g a d dilige ce The Co str ctio Speci icatio sI stit te provides a mberi g system to assist i orga izi g correspo de ce req ests or i ormatiocha ge orders project meeti g mi tes progress payme ts a d claims Several comp ter programsare available that will trac s bmittals cha ge orders a d other time-se sitive doc me ts Whateversystem is adopted to bri g order to the doc me ts serio s pla i g at the begi i g o the project willsave co tless ho rs laterThe begi i g o the project is the time to pla or as-b ilt drawi gs a d warra ty co sideratio sMa i g s re that each a d every deviatio rom the origi al pla s is doc me ted o the as-b iltdrawi gs is di ic lt Leavi g these cha ges to the e d o the job is time co s mi g a d leads toi acc racies Warra ties o te req ire that a age t o the ma act rer be prese t d ri g i stallatioEach o these req ireme ts eeds to be ide ti ied a d a remi der placed i the project sched le orchec listA s ccess l tech iq e sed by some co tractors to ha dle wee ly project meeti gs is based oco sec tively mberi g each meeti g I the irst project meeti g all the items disc ssed are classi iedas ew b si ess a d mbered 1 1 1 2 a d so o At the ext project meeti g old b si ess is covered irst a d i volves resol tio o items 1 1 1 2 a d so o As items are resolved they are dropped romthe list New b si ess items i the seco d project meeti g are mbered 2 1 2 2 a d so o I this way
  • 105. every project meeti g problem is mbered Each mber remai s as old b si ess til resolved Noto ly does this system eep trac o each problem b t the le gth o time the problem remai s resolved is i dicated by its mber 6.18 Putting the Plans on PaperJ st as project pla i g res lts i a doc me ted project etwor complete with reso rces a d job costsprod ctio pla i g has to be red ced to paper as well S etches lists a d arratives record theprod ctio pla s This i ormatio eeds to be orga ized i s ch a way that the pla s ca be o d atthe proper time Whe a delivery o tra s ormers is d e the s etch showi g where they are to bestored m st be readily available I yo ca ot i d the record o a care lly orm lated pla whe it is eeded all o the pla i g e ort spe t i developi g it is wasted P tti g the pla i g to paper a dcomm icati g it to the ow er a d the project team is disc ssed rther i Chapter 12
  • 106. 7 Project Time Acceleration 7.1 Time Schedule AdjustmentsFreq e tly project wor sched les m st be adj sted to accommodate adverse job circ msta ces Theserevisio s are o te esse tial so that co tract time req ireme ts ca be met Ma y times establishedtime goals dictate that ey stages o the wor be achieved earlier tha origi ally pla ed The start or i ish dates o major job eleme ts o te m st be improved to satis y established time co strai ts orcommitme ts Milesto es etwor i ter aces a d i al completio are commo examples o eyeve ts that sometimes m st be resched led to earlier dates S ch sched le adva ces are accomplishedi practice by per ormi g certai portio s o the wor i shorter times tha had origi ally beeallocated to themThis chapter disc sses why ma ageme t actio to red ce project time occasio ally is eeded a d howthe associated time red ctio st dies are co d cted The highway bridge is sed or p rposes odisc ssio a d ill stratio 7.2 Need for Time ReductionThere are ma y practical examples or which shorte i g the time o selected job eleme ts ca bedesirable as a mea s o meeti g importa t project target dates For example by terms o theco str ctio co tract the ow er may impose a job completio date that the c rre t project pla will ot meet Fail re to meet this co tract al time req ireme t will p t the co tractor i breach o co tracta d ma e it liable or a y damages s ered by the ow er beca se o late project completio a jobi progress the ow er may desire a earlier completio date tha origi ally called or by the co tracta d may req est that the co tractor q ote a price or expediti g the wor It is e tirely possible that theprogrammed project d ratio time may ot s it the co tractor’s ow eeds The co tractor maywish to achieve job completio by a certai date to avoid adverse weather to beat the a al spri gr o to ree wor ers a d eq ipme t or other wor or or other reaso s Fi a cial arra geme ts maybe s ch that it is ecessary to i ish certai wor withi a prescribed iscal period The prime co tractormay wish to co s mmate the project ahead o time to receive a early completio bo s rom theow er A commo motivatio or time acceleratio occ rs whe the wor is well der way a d delayshave res lted i a s bsta tial loss o time that m st be recovered by the e d o the projectAltho gh ot i volvi g the e tire project a similar sit atio ca arise whe attempti g to meet aestablished milesto e It is ot s al or the comp ted early times o milesto e eve ts to occ r latertha desired A a alogo s sit atio ca arise with respect to etwor i ter ace eve tsThese examples clearly disclose o e o the great adva tages o bei g able to establish adva ceco str ctio sched les with reaso able acc racy S ch i ormatio ma es it possible or the projectma ager to detect speci ic time problems well i adva ce a d to i itiate appropriate remedial actioCertai ly this is pre erable to havi g o orewar i g o s ch problems til it is too late to do m ch ia ythi g abo t them irst impressio it may appear i co gr o s to co sider shorte i g the d ratio o a project whe aco ti ge cy allowa ce has bee added to the comp ted ormal time I the case o the highway bridgea co ti ge cy o six days was added to the calc lated time o 64 days to establish a probable completiotime o 70 wor i g days This project time is the best adva ce estimate available o the act al word ratio req ired As a co seq e ce o this act 70 wor i g days is the most li ely d ratio o thehighway bridge a d a y eed to shorte the project sho ld depe d o how this time compares withthe prescribed co tract period or other established time limitatio Removi g the co ti ge cy rom theproject is ot a reliable mea s o accelerati g the completio date 7.3 General Time-Reduction ProcedurePerhaps it is appropriate ow to me tio that a variety o terms are applied to the process o shorte i gproject time d ratio s “Least-cost expediti g †“project compressio †a d “time-costtrade-o †are all sed i re ere ce to the proced res disc ssed i this chapter The exact ome clat re is ot especially importa t as lo g as the method a d its applicatio are thoro ghly
  • 107. derstood The se o the term “expediti g†i co ec o with shorte i g project timereq ireme ts is ort ate beca se the same term is sed with regard to actio s ta e to e s retimely reso rce s pport or co str ctio operatio s However the do ble mea i g o“expediti g†is commo place i the co str ctio i d stry a d is so applied hereiTo shorte the time period req ired to reach a milesto e or i ter ace eve t or to achieve projectcompletio o e eed be co cer ed with red ci g the time d ratio s o o ly a certai gro p oactivities As has already bee show the time req ired to reach a y t re etwor eve t termi al orotherwise is determi ed by the lo gest time path rom the c rre t stage o project adva ceme t tothat eve t Co seq e tly i the time req ired to reach a certai eve t is to be red ced this ca beaccomplished o ly by shorte i g the lo gest path leadi g to that eve t This observatio is veryreveali g a d importa t I the abse ce o s ch ma ageme t i ormatio the s al reactio whe aproject is alli g behi d sched le is to haphazardly expedite all the o goi g activities i a attempt toma e p the lost time The i ability to discrimi ate betwee those activities that tr ly co trol a d thoseactivities o little or o time co seq e ce ca ma e s ch expediti g actio s ar more expe sive tha is ecessaryWhe the date o project completio is to be adva ced it is the etwor critical path that m st beshorte ed Whe red ci g the time to achieve a milesto e or i ter ace eve t the diagram critical pathitsel may ot be i volved i a y way The lo gest time path leadi g to the milesto e or i ter ace eve tm st be shorte ed This path may be e tirely separate rom the critical path that applies to the e tire etwor For p rposes o disc ssi g the red ctio o project time the lo gest time path leadi g to theeve t i q estio will be re erred to as its critical pathAt this poi t it m st be recog ized that whe a lo gest path is shorte ed the loats o other activitypaths leadi g to the same eve t are red ced comme s rately It is i evitable there ore that co ti edshorte i g o the origi al critical path will lead soo er or later to the ormatio o ew critical pathsa d ew critical activities Whe m ltiple critical paths are i volved all s ch paths m st be shorte edsim lta eo sly i the desired time adva ceme t o the eve t is to be achieved Shorte i g o e criticalpath b t ot a other accomplishes othi g except to provide the shorte ed path with eededadditio al loatWhe time red ctio is do e ma ally the e ect o each shorte i g actio m st be chec ed toascertai whether it has prod ced ew critical activities The s al way to do so is to per orm a etworrecalc latio ollowi g each step i the time-red ctio process S ch recalc latio s ca be do ema ally or by comp ter I the etwor is ot large ma al calc latio s ca be ast a d co ve ie tFor a large etwor ma y s ccessive recalc latio s ca become a s bsta tial chore Eve tho gh time-scaled diagrams are o limited val e i ma i g act al time-red ctio st dies s ch plots are especially se l or explai i g the total e ect o a give time red ctio A etwor cha ge ca be vis alized iterms o moveme ts o rigid- rame portio s o the diagram a d the e ect o these moveme ts o itselastic ( loat) co ectio s Whe ever a y shorte i g actio elimi ates a dashed loat li e i a time-scaled etwor a ew critical path is ormed a tomatically Portio s o Fig re 5 14 are sed i thischapter to give the reader a better appreciatio o what etwor time red ctio act ally i volves 7.4 Shortening the Longest Time PathIt has ow bee established that i the date o a speci ied project eve t is to be adva ced the le gth othe lo gest time path leadi g to the eve t m st be shorte ed Basically there are o ly two ways toaccomplish this e is to modi y the job logic i some way s ch that the lo gest ro te is dimi ished ile gth Doi g this i volves a localized rewor i g o the origi al job pla with time bei g gai ed byrearra gi g the order i which job activities will be accomplished or i creasi g lead a d lag times tomaximize activity co c rre cy This time-red ctio proced re does ot red ce the d ratio s oactivities themselves; it gai s time by the more avorable seq e ci g o selected job operatio sThe other possible way to red ce the le gth o a critical path is to red ce the d ratio o o e or more oits co stit e t activities Each critical activity irst m st be exami ed to see i a y shorte i g is possibleThe compressio o a activity ca be achieved i a variety o ways depe di g o its at re Additio alcrews overtime or m ltiple shi ts might be sed It may be possible to s bco tract it More eq ipme tmight be bro ght i temporarily a d assig ed to that activity Earlier material deliveries may beachieved by a thorizi g the abricator to wor overtime by si g air reight or special ha dli g or by
  • 108. se di g o e o the co tractor’s ow tr c s to pic p a d deliver the material There s ally are oco rse some activities whose d ratio s ca ot be red ced easibly 7.5 Project Direct CostsBe ore the disc ssio o project time red ctio ca proceed rther it is ecessary to disc ss the at reo project direct costs a d i direct costs Costs are ecessarily i volved with time red ctio beca seco str ctio expe se is a ctio o time Altho gh ma ageme t discretio occasio ally may dictateotherwise a e ort s ally is made to achieve gai s i time with the least possible i crease i projectcost I project ma ageme t is to ma e sched le adj stme ts at the least additio al cost it is ecessaryto dersta d how the costs o co str ctio operatio s vary with timeThe direct cost o a activity is made p o the expe se o labor eq ipme t materials a d s bco tractsEach activity has its ormal cost a d ormal d ratio The “ ormal cost†is the least direct costreq ired to accomplish that activity a d is the cost c stomarily ascribed to the wor whe the job isbei g estimated “Normal d ratio †is the ac vity d ra o determi ed d ri g the sched li gphase Altho gh there is othi g precise abo t a ormal time it still co stit tes a reaso ably disti ctdat m or re ere ce poi t or accomplishi g a activity at its least direct cost It is obvio s that the directcost o the total project is eq al to the s m o the direct costs o the i divid al activities a d that the ormal project d ratio is derived rom the activities’ ormal d ratio s It ollows there ore thatthe least total direct cost o the e tire job is the cost associated with the ormal project d ratioI the estimated activity times ca be accepted as goi g ha d i ha d with mi im m direct cost thea y variatio i a activity time rom that estimated either more or less m st res lt i a comme s ratei crease i its direct cost The degree to which this r le act ally applies i practice is co siderably morecertai with respect to i creased costs ca sed by red ci g the activity d ratio tha by exte di g itHowever co tractors are seldom co cer ed with stretchi g o t or deliberately exte di g the d ratioo a job activityThe practical act that shorte i g a activity time ormally will i crease its direct cost is easilydemo strated The se o m ltiple shi ts or overtime wor obvio sly e tails extra labor expe seCrowdi g i more wor crews or pieces o eq ipme t ma es job s pervisio di ic lt red cesoperatio al e icie cy a d i creases costs o prod ctio Early material delivery req ires payme t opremi ms to the ve dor or i creased tra sportatio a d ha dli g costs All this leads to the co cl siothat i the project time req ireme t is to be red ced the direct costs o the activities act allyshorte ed s ally will be i creased 7.6 Variation of Activity Direct Cost with TimeThe direct costs o activities ca vary with time i ma y ways altho gh here it is co sidered that thesecosts always vary i i verse proportio with time A co ti o s li ear or straight-li e variatio o directcost with time is a commo example This is the res lt o a expediti g actio s ch as overtime orm ltiple shi ts where the extra cost or each day gai ed is j st abo t co sta t Fig re 7 1a is such a case,where the normal activity time of 15 days can be reduced by as much as 3 days. The increase in directcost of this activity is a constant $100 per day, this being termed the cost slope of the activity. Thecontractor may elect to expedite the activity by one, two, or three days, for which the extra cost will be$100, $200, or $300, respectively.Figure 7.1Activity time-cost variation
  • 109. The “normal points†in Figure 7.1 represent the activity normal times and normal direct costsdiscussed before. The expediting of an activity is often called crashing. As indicated in the figure, theminimum time to which an activity can be realistically reduced is called its crash time, and thecorresponding direct cost is called its crash cost. The plotted intersection of these two values is called itscrash point.Figure 7.1b shows a continuous, piecewise linear, time-cost variation. The figure indicates that a timereduction of one, two, or three days is possible, but the cost slope increases for each additional daygained. An example of a piecewise linear variation is when crew overtime is involved and the use of aprogressively larger crew is possible as the work advances. Figure 7.1c is a discontinuous or gapvariation where the expediting action reduces the activity duration from 15 to 12 working days, with notime possibilities in between. The activity is reduced either by three days or not at all, and the extra costof the reduction is a fixed sum of $300. This type of time-cost variation is common in construction.Paying a premium for an early material delivery and shipping by air rather than motor freight areexamples.
  • 110. Obviously, other forms of time-cost variation are possible. However, great accuracy in determining theextra costs resulting from expediting actions is seldom achievable, and the time-cost variations used,along with the expediting of construction activities, are generally limited to the three contained inFigure 7.1. 7.7 Project Indirect CostsAs described in Section 3.21, project overhead consists of indirect costs incurred in support of the fieldwork but that cannot be associated with any particular physical portion of the job. Figure 3.7 disclosesthat, on the highway bridge, the time-variable job overhead expense was estimated to be $43,690.Time-constant overhead expenses are not variable with project duration and need not be consideredhere. The probable duration of the highway bridge has been determined to be 70 working days. Thismeans that the time-variable indirect expense on this job amounts to $43,690 ÷ 70 days = $624 perworking day.The preceding discussion discloses that crashing an activity, while increasing direct costs, will generallyreduce indirect costs. If a specific activity is shortened, its direct expense increases, but if it leads to acorresponding decrease in overall project duration, the indirect cost is reduced. 7.8 Time-Cost Trade-off by ComputerA number of computer programs are available that will accept activity time-cost data such as that inFigure 7.1 and produce an optimum schedule of project cost and time. The project duration is decreasedfrom its normal length, one day at a time. For each incremental reduction in duration, the computersearches out the combination of activity crashes for the one that will accomplish this time reduction atthe least added cost. To the increased direct cost is added the time-constant overhead expense and thetime-variable overhead cost at the established per-diem rate. This provides the total project cost for thereduced duration. The basic objective of these computer programs is to determine the project durationfor which the total project cost is minimized.Because of major failings, however, such computerized time-cost trade-offs have found limitedacceptance in the construction industry. The job models used in such analyses are grossly oversimplifiedand provide only theoretical solutions that bear little relationship to the realities of a constructionproject. The only time-cost data that the computer can handle are time-cost slopes for individualactivities. It has no capability of optimizing time shortening when changes of network logic are involvedas possible alternatives. Stated another way, the computer can only perform a time-cost trade-offanalysis by compressing individual activities in a network with a set system of logic. This is a significantlimitation when it is recognized that revisions in the programmed job plan frequently account for themost significant time reductions.The conventional computer analysis goes through a step-by-step process of expediting activities in theascending order of their cost slopes. This unthinking and invariable insistence of least additional costoften is not in the best interests of good job management. For various practical reasons, some activitiesare more attractive choices for expediting than others. For example, the computer may select an activityfor expediting on the basis of its least additional cost, even though it may be scheduled several monthshence. A project manager probably would be better advised to expedite a critical activity near at hand,even at a somewhat higher incremental cost, because the future activity contains yet-unknown risks.Future uncertainty is such that the distant activity may subsequently become noncritical or mayultimately be unable to provide the time reduction required. The reduction of project time must, ofnecessity, involve considerations other than merely minimizing extra cost. These considerations,although possibly subtle or indirect, often can be of overriding importance to project management.At this point, it suffices to say that the computer does not normally serve as an adequate stand-alonedevice for project shortening. Manual methods, relying on human insight and judgment, continue toplay a commanding role in the process. The project time acceleration procedures discussed hereindescribe and emphasize such an approach. This does not mean that the computer plays a trivialsupporting role, since management and computer can work together to achieve the best solutionpossible. The manager can originate and pass on matters of judgment and the computer can process thedecisions made by project management. 7.9 Practical Aspects of Time Reduction
  • 111. The process of least-cost shortening of actual construction networks can become enormously complex.Multiple critical paths can appear and make the shortening process a very complicated procedure. Thenumber of possible expediting combinations to be tested, if an optimal solution is to be achieved, canbecome very large. It must be recognized, therefore, that the usual manual time reduction will certainlynot always provide project management with truly optimal expediting combinations. However,mathematical precision with imprecise data is neither the only nor necessarily the most importantconsideration involved in such a process. Of necessity, the actual accomplishment of time reduction inpractice must be concerned with a number of practical considerations beyond the matter of buying themost time for the least money.Manual solutions for project time reductions, while perhaps not optimal, do provide invaluable guidanceto the project manager in making decisions about whether expediting is practical and, if so, how toproceed. In most cases, guidance on how to make intelligent choices of time-reduction actions is asvaluable as a theoretically optimal solution. Input data are uncertain, conditions change from day to day,and construction is simply not an exact or a completely predictable process. Even the critical path of agiven network may change its routing occasionally as the work progresses. Project managers strive tofind practical, reasonable answers rather than seek to achieve perfection. Expediting a project manuallymakes it possible to inject value judgments into the process and affords the project manager an intuitivefeel for the effect of expediting actions on other aspects of the project. In addition, a project time-reduction study can easily include the critical evaluation of time gained by revisions in job logic as wellas that gained by shortening individual activities.The manual accomplishment of project time reduction is directed entirely toward reducing the length ofthe applicable critical path or paths. This is a step-by-step process using time-reduction measures thatare considered feasible and best suited to the job context. These may be changes in the job plan or theshortening of individual activities, or both. The usual procedure is to gain each increment of time withthe least possible increase in direct cost. Where other job factors are of greater importance thanincremental cost, shortening steps are taken in whatever order project management believes is in theoverall best interest of the work. 7.10 Reduction of the Highway Bridge DurationFor purposes of illustration, suppose the contractor on the highway bridge determines that the probableduration of 70 working days or 98 calendar days is unsatisfactory. Work on this job has not yet begun,and a study is to be conducted to investigate the feasibility and attendant cost of reducing the overallproject duration by perhaps as much as 10 percent.The essential question is, of course, how the project critical path can be reduced from its current timeduration. Initially, common sense suggests that a second look be given to the present operational plan,the objective being possibly to gain time at no increase in direct cost. Although knowledgeable andexperienced people carefully devised the job plan, the original planning effort cannot be expected to beperfect. It seems likely that a restudy of the operational sequence could sharpen the planning approachand perhaps indicate opportunities for greater time efficiency.If reexamination of the original job logic does not produce the desired time gain at no additional cost,then the contractor has no option but to sacrifice project cost for time. Almost any constructionoperation can be performed in less time if someone is willing to pay for the additional expense. Thereare undoubtedly a number of opportunities for shortening the duration of the highway bridge byeffecting changes in job logic or by reducing the times needed to accomplish individual critical activities.When extra cost is involved, project shortening is achieved by evaluating the feasible alternatives and,normally, adopting the least-cost combination of those that will produce the desired time adjustment.It is the intent of the next five sections to present specific discussions of how the overall duration of thehighway bridge might be reduced at little or no additional direct cost to the contractor. Such areexamination of the programmed plan will not always result in a time gain, but the possibility is thereand should be investigated. A word of caution is in order, however. When such restudies are being madeto pick up some badly needed time, there is always a tendency to become optimistic. Those who makedecisions concerning project time reduction must be sensible and pragmatic in their judgments. A. Restudy of Critical Activity Durations
  • 112. There is one obvious initial check to be made when reexamining the critical path of a project to beshortened: review the time estimates of the individual critical activities. Errors can be made, and it isworthwhile to verify the reasonableness of the time durations originally estimated.Another possibility also can be reviewed. When the time estimates were first made, it was not knownwhich of the activities would prove to be critical. The original time estimates of some activities may havebeen made in contemplation of the limited future availability of labor crews or construction equipment.As a result, some of the activity duration estimates for what later turned out to be critical work itemswere based on smaller than optimum-size crews or equipment spreads. Now that the identities ofcritical activities have been established, it may be feasible to defer action on some noncritical activities,using their floats for this purpose, and to reassign resources temporarily to the critical activities, withthe objective of accomplishing them in less time.A project restudy aimed at gaining time at no additional direct cost is essentially a critical second look atthe established operational plan. The objective, of course, is to rework or refine the logic of a limitedarea of the network that will result in a shortened critical path. Here, innovative thinking and a freshapproach may result in important improvements of work methods. Too often, traditional andestablished field procedures are accepted as the only way of solving a problem. At times they should bechallenged by inquiring minds seeking a better solution. A good old-fashioned brainstorming sessionoccasionally will produce some ingenious ideas concerning new approaches.In some cases, the contractor has the authority to make changes in project materials or design orperhaps is able to do so with owner approval. For example, in a design-construct contract, the projectmanager may decide to redesign a segment of the project to take advantage of a faster constructionmethod, thereby reducing the overall duration of the project. Although the design phase of a projectprovides most of the opportunities to reduce construction duration and costs, the ordinary design-bid-build contract rarely makes this possible. B. Restudy of Project PlanAs an example of a change in project plan to shorten the critical path, it may be possible to performcertain critical activities concurrently or in parallel rather than in series. To show how this might work,reference is made to the time-scaled diagram of the highway bridge in Figure 5.14. Study of the criticalactivities will disclose the possibility that painting can be done concurrently with, rather than after,stripping the deck forms. Figure 7.2, which is excerpted from Figure 5.14, illustrates this change in theproject schedule, showing that activity 370, “Paint,†could start at the same me as ac vity 350,“Strip deck,†thus shortening the cri cal path by two days. If this were done, pain ng would nolonger be critical; rather, the guardrail installation would take over the painting activity’s position onthe critical path, as indicated by Figure 7.2. C. Critical Activities in ParallelFigure 7.2Highway bridge, critical activities in parallel
  • 113. The possibility of accomplishing activities 350 and 370 in parallel with one another might generate anunsafe working condition. This would have to be resolved before this means of shortening the criticalpath could be approved for implementation in the field. D. Subdivision of Critical ActivitiesIn shortening a critical path, a check can be made to determine if each critical activity must necessarilybe completed before the next one can start. The judicious subdividing of one critical activity may enableit to overlap another. In other words, it may be possible to subdivide a critical activity and perform aportion of it in parallel with another critical activity. There appear to be two or three such opportunitiesin Figure 5.14, only one of which will be discussed here because of the similarity between them.Referring to activity 180, “Forms & rebar, abutment #1,†one side of these forms must be erectedbefore the steel can be tied. Consequently, the finish of activity 60, “Fabricate & deliver abutment &deck rebar,†could overlap the start of ac vity 180 by one day, assuming that the me necessary toerect one side of these prefabricated forms is one day. Figure 7.3 shows how the original time-scaleddiagram (Figure 5.14) would have to be modified to reflect this change. As can be seen, this alterationwould shorten the critical path, and hence the time to any succeeding critical activity, including theterminal activity, by one day.As stated previously, the possibility of other critical paths being formed must be investigated each timethe critical path is shortened. For the time reduction discussed in the previous paragraph, reference toFigure 5.14 shows that all activities in the network to the right of activity 180 have moved as a unit oneday to the left. In so doing, the floats shown at the ends of activities 230 and 260 have been reduced byone day. In addition, the creation of the new activity 175, “Outside forms, abutment #1,†reducesby one day the float following activity 80 and that following activity 170. This action does not, however,result in the formation of any new critical activities.Figure 7.3Highway bridge, subdivision of critical activity
  • 114. E. SubcontractingAnother possibility for shortening a project critical path might be to subcontract certain work that thegeneral contractor originally intended to do with its own forces. The project plan may show certaincritical activities to be in series with one another, not because of the physical order in which the workmust be done but because they require the same limited resource. Subcontracting all or a portion of thework involved to a specialty contractor that has adequate equipment and manpower might enable theactivities to be performed concurrently rather than in series, thus saving considerable time.It is not unusual for an equipment or labor restraint together with a dependent activity to be a part ofthe critical path. This situation usually represents a limitation on the availability of a general contractorresource. The prime contractor might consider subcontracting that part of the work to a firm whoselabor crews or equipment would be available at an earlier date than its own. Determining whether thework could be subcontracted for the same cost that the prime contractor estimated would require study.If extra cost is involved, this becomes an expediting action that will have to be considered on acomparative cost basis along with the other additional expense possibilities. 7.11 Time Reduction of Highway Bridge by ExpeditingThe preceding five sections discussed how a critical reexamination of the original job plan might result inshortening a project critical path at no increase in direct cost. If such a network study does not producethe desired time reduction, then project management must literally buy time by resorting to expeditingactions that will increase direct costs. Expediting actions are thus distinguished herein from time gainedat no extra expense.The sections that follow consider the expediting process as it is applied to the highway bridge. For clarity,the discussion assumes that none of the possible time-reduction measures discussed previously hasbeen adopted; therefore, the original plan and schedule of the highway bridge remain unaltered.Shortening this project by subcontracting is not considered either feasible or desirable, so the ensuingtime-reduction measures are limited to those the prime contractor can achieve with its own forces.The first step in expediting the highway bridge probably should be to determine if there are any changesin job plan that would shorten the critical path. As has already been stated, modifications of networklogic are often more fruitful than shortening individual activities. An obvious change that could be madein the logic of the highway bridge, and which involves the critical path, would be to prefabricate and usetwo sets of abutment forms. It will be recalled that the job plan for this project, as presented in Figure5.1, calls for only one set of forms to be built, these forms being used first for abutment #1 and then
  • 115. reused for abutment #2. Consequently, according to the original plan, the start of the second abutmentwill have to wait the stripping of forms from the first abutment. A second set of abutment forms wouldeliminate the dependency line from activity 220, “Strip and cure, abutment #1,†to ac vity 240,“Forms and rebar, abutment #2.†This would enable the forming of abutment #2 to start just assoon as footing #2 is finished (activity 230). The effect of this change can be checked by a recalculationof the altered network or by reference to the time-scaled plot in Figure 5.14. In either case, if thischange is made, the entire project will be shortened by six working days, from 70 to 64. The abutment#2 string of three activities will no longer be critical, as the critical path now is routed through activity280.Figure 7.4Highway bridge, direct costs of expediting actions
  • 116. A preliminary examination of the critical activities of the highway bridge discloses that there might beseveral possibilities for expediting individual activities. Suppose careful study, however, reveals thatthere are actually only four activities for which some expediting is considered to be practicable in theview of project management. Figure 7.4 lists the time reduction and additional direct cost for each ofthe ways in which the highway bridge may feasibly be expedited. Assuming that all of these alternativesare equally acceptable to project management, the process is now one of shortening the project, onestep at a time, each increment of time being gained at minimum additional direct cost. Projectmanagement now can decide how much time reduction it is willing to purchase. 7.12 Least-Cost Expediting of the Highway BridgeUsing the information summarized in Figure 7.4, the highway bridge is now to be reduced in duration,with each successive increment of time compression being realized at a minimum increase in projectdirect cost. As each step is taken, a check must be made to determine whether that expediting actionresults in the formation of any new critical activities. This check is made by means of a networkrecalculation after each time-reduction step. Figure 7.5 summarizes the results of the successiveexpediting actions.Examination of Figure 7.4 discloses that the cheapest first step in the shortening process is theexpediting by one day of critical activity 350, “Strip deck forms,†at an addi onal direct cost of$202. In a network with a single critical path, as is the case with the highway bridge, the amount of anystep decrease in the duration of a critical activity is subject to two limitations, one internal to the activityand the other external. The first of these is how much internal shortening of the activity is physicallypossible. In the case of activity 350, the physical limit has been established as one day. The secondlimitation is based on how much the activity can be shortened before a new parallel critical path isformed. Often this limitation is referred to as the external or logical limit of an activity shortening. Thelogical limit of a given critical activity is equal to the total float of the shortest alternative path aroundthat activity. Reference to Figure 5.1 shows that the path through activity 380 (TF = 7) is the shortestway around activity 350. Hence, the logical limit of activity 350 is 7, which just says that activity 350could be shortened by as much as seven days before a new critical path is formed. Obviously, the firststep in expediting the highway bridge using activity 350 is limited to the lesser of its physical limit (oneday) or its logical limit (seven days), or a shortening of one working day. This information is summarizedin step 1 of Figure 7.5a. Activities 200 and 250 are expedited in a similar manner and are shown as steps2 and 3 in Figure 7.5a. In this figure, the creation of a new critical path as a result of crashing theduration is indicated by a “yes†or “no†entry in the column en tled “New CriticalPath.â€Figure 7.5Highway bridge, least-cost expediting
  • 117. It is necessary to conduct three separate sequences of shortening actions in order to shorten thehighway bridge to its full potential at the least additional cost. Figure 7.5a is the first of these sequences.The successive shortening by actions E, C, and D, as described in the figure, shortens the project bythree days at a total extra direct cost of $1,248. If the project is to be shortened by only three days, thisis the least expensive course of action. To shorten the project additionally, an entirely new and differentsequence of shortenings must be used. In other words, the time-reduction process must be startedanew. Step 1 of Figure 7.5b shows that shortening activity 60 can reduce the project by three days, from70 to 67 working days, at an additional cost of $2,376. Actually, the expenditure of $2,376 shortensactivity 60 by four days, which is its internal or physical limit. However, when activity 60 is shortened bythree days, a new branch on the critical path is formed, so the logical limit of this shortening action isthree days and shortening activity 60 results in shortening the project only by three days. If the fourthday of the shortening of activity 60 is to become usable, some activity on the new critical branch alsowill have to be shortened by one day. Study of these newly critical activities discloses that it is notpossible or feasible to shorten any of them. Therefore, the total effect of step 1 in Figure 7.5b is areduction of three days. Steps 2, 3, and 4, shown in Figure 7.5b, reduce the highway bridge constructionto a duration of 64 working days at a total additional cost of $3,422. The sum of $3,422 is the leastadditional cost for which the project can be shortened by six days.To reduce the highway bridge duration below 64 days, a third new series of shortenings is needed. Step1 of Figure 7.5c shows that prefabricating and using two sets of abutment forms (a logic change, not anactivity shortening) reduces the highway bridge duration from 70 to 64 working days, a gain of six days.The time reduction achieved by a logic change is the difference between the lengths of the critical paths
  • 118. before and after the logic revision is made. A change in network logic, therefore, has no physical limit,only a logical limit. Steps 2 and 3 in Figure 7.5c reduce the duration of the highway bridge to 62 days atan additional cost of $6,199. It might be noted here that if activity 250 is now expedited, no furthershortening of the project results. This is because, when the logic change in step 1 of Figure 7.5c is made,there is a change in critical path location, and activity 250 is no longer critical. Expediting it will onlyincrease its float, not reduce the length of the critical path.The project duration has now been reduced by a little more than 10 percent, which was the originalobjective. Hence, the time-reduction study is now complete and project management must decide howmuch expediting it wishes to pay for. Figure 7.6 summarizes the expediting costs involved in shorteningthe highway bridge. This information tells the contractor how to reduce the project duration by anygiven number of working days at the least cost, up to a maximum shortening of eight days.Figure 7.6Highway bridge, direct cost of expediting 7.13 Limitations on Time-Reduction StepsAs has been shown, a number of limitations apply to how much time reduction can be accomplished inany one step. These five limitations are summarized next.1. Physical limit of a critical activity. This is the maximum shortening of a given activity considered to bepractical. Although most activities can be shortened to some extent, some are considered to beintractable on practical grounds.2. Logical limit of a critical activity. The reduction in duration of a critical activity reduces the total floatsof other activities, which sometimes causes another chain of activities to become critical. This can, attimes, prevent expediting an activity to its full potential. Step 1 in Figure 7.5b is an example of this.
  • 119. 3. Logical limit of a network logic change. A network logic change results in a set number of days beinggained with no time change possibilities in between. Step 1 in Figure 7.5c is a logic change that reducesthe highway bridge duration by six days. The six days is an irreducible time reduction—it is either thator nothing.4. Shortening limited by a parallel critical path. Parallel critical paths, or subpaths, are common. If onebranch of parallel critical paths is to be decreased in length, a commensurate decrease must also bemade in the other branch. If only one branch is reduced, it simply becomes a floater, and neither theremaining critical path nor the project is reduced in duration. This situation was encountered inconjunction with the inability to shorten activity 60 completely in Section 7.17.5. Shortening limited by an irreducible critical path. When any given critical path has been shortened toits full capability, no further reduction in project duration is possible. A critical path that cannot becompressed makes fruitless the shortening of noncritical portions of the network. 7.14 Variation of Total Project Cost with TimePrior discussions have shown that a general characteristic of construction projects is for their directcosts to increase and their field overhead costs to decrease as the construction period is reduced belowthe normal time. Figure 7.6 is a plot of the increase in direct cost required to expedite the highwaybridge. It was determined in Section 7.7 that the time-variable field overhead expense for this projectamounted to approximately $624 per working day. Figure 3.7 disclosed that the project constantoverhead expenses totaled $26,178.40. Figure 7.7 shows how total project overhead, direct cost, andthe sum of the two vary with time. The field overhead expense shown in Figure 7.7a is obtained bymultiplying the number of working days by $624 and adding the sum of $26,178.40. The normal directcost of the project is established from Figure 3.8 as $398,975. Adding the expediting costs from Figure7.6 to this project normal cost gives the direct costs shown in Figure 7.7b. Combining the direct costwith the overhead expense for each project duration gives the costs shown in Figure 7.7c . Total projectcost for any duration may be obtained by adding small tools ($4,649), tax ($14,205), markup ($73,155),and the cost of the contract bonds ($5,665) to the values shown in Figure 7.7c. The four values just citedare obtained form the original project estimate given in Figure 3.8.Figure 7.7Highway bridge, variation of costs with duration
  • 120. To illustrate how the plot in Figure 7.7c can be used, suppose that the construction period prescribed bycontract for the highway bridge is 62 working days and that liquidated damages in the amount of $400per calendar day will be imposed for late completion. The best evidence now available indicates that 70working days actually will be required unless the job is expedited. If a management decision is made notto expedite, the contractor is apt to be assessed $4,000 in liquidated damages (8 working days = 10calendar days @ $400 per day). If the job is expedited to a duration of 62 working days, Figure 7.7cindicates that the total additional expense to the contractor will be $470,050 - $468,843 = $1,207. Verylikely the decision of project management will be to expedite the project.Besides project shortening, there are other reasons the contractor must be able to associate costs withproject durations. One such situation occurs when the contractor bids on a project in which the ownerrequires a range of price quotes for a variety of specified construction periods. Although this usuallyrequires the contractor to submit a bid before a complete time study is available, the contractor stillmust make some judgments regarding the variation of direct and overhead costs with time. 7.15 Expedited Highway Bridge ScheduleAssume that the contractor has decided to expedite the highway bridge by eight working days to ananticipated duration of 62 days. This expediting information must now be reflected in the construction
  • 121. schedule. The results of the network recalculation made after step 3 in Figure 7.5c will provide thisinformation.Reference to Figure 7.5c shows that four changes must be made to the original precedence diagram,Figure 5.1, when the recalculations are made:1. The logic change accomplished by building two sets of abutment forms and starting activity 240immediately after activity 230 is accomplished by eliminating the dependency line from activity 220 toactivity 240 (step 1 of Figure 7.5c).Figure 7.8Highway bridge, expedited schedule2. Because two sets of abutment forms are now going to be used, the duration of activity 80, “Makeabutment forms,†is increased from three to six days (step 1 of Figure 7.5c).3. The duration of activity 350 is reduced from three days to two days (step 2 of Figure 7.5c).4. The duration of activity 200 is reduced from two days to one day (step 3 of Figure 7.5c).
  • 122. These four network changes are made to the precedence diagram of the highway bridge and therecalculations are performed. Figure 7.8 summarizes the activity times and float values that areobtained. 7.16 Milestone and Interface EventsThe principal point of the preceding discussions has been the reduction of overall project duration. Thisreduction includes expediting an ongoing project that has suffered previous delays. It has already beenpointed out, however, that sometimes it is necessary to advance the expected dates of milestone andinterface events. If the scheduled time of such an event does not satisfy an established timerequirement, then some action by the contractor is in order. The procedure is very much the same asthat for shortening project duration, except that the project critical path may or may not be involved.The longest path from project start to that event determines the early time for any event, and efforts toadvance the event time must be concerned with shortening this longest path. The longest path wouldfirst be restudied to see whether the desired shortening could be achieved at no increase in direct cost.If not, then the contractor must resort to expediting at additional direct expense. 7.17 Project ExtensionThe entire emphasis of this chapter has been directed toward the shortening of a project. At times,though, it may be desirable to lengthen certain activities or even the project itself. An example of thiswould be a project whose costs were originally estimated assuming that expediting actions would beneeded if the owner’s time requirements were to be met. It is typical for a contractor to anticipatetime difficulties and to build into the original cost estimate the extra expense of overtime, multipleshifts, and other means of expediting the work. Unfortunately, at the time the project is being bid, thecontractor usually will not have made an accurate forecast of project duration nor have identified thecritical activities. About the only ways in which the contractor can figure in the extra costs of expeditingactions are either to expedite most or all of the job operations or to make some educated guesses aboutwhich work items may turn out to be critical.As sometimes happens, a subsequent detailed network analysis reveals that all or some of the plannedexpediting procedures will be unnecessary. This case is the inverse of that previously treated in thischapter. The contractor now finds it desirable to relax the job plan and realize the attendant savings.Obviously, the contractor wants to do this in a manner that will maximize its gain.Even if the overall project duration must remain as planned, the contractor usually can rescind theexpediting actions for at least some of the noncritical activities. The maximum duration increase grantedto any given activity would be limited to the length of its total float. Further relaxation would result inthe formation of a new critical path or subpath. For this reason, a record must again be maintainedconcerning the effect of each activity’s time change on the floats of other activities. If all expeditingactions of noncritical activities cannot be rescinded, then the most expensive of these actions should beeliminated first.If the overall project duration can be extended from the original plan, then certain of the criticalactivities also can be relaxed. The only effect of this relaxation is to lengthen the critical path and, hence,to increase the floats of all noncritical activities. In this case, the critical activities should be relaxed first,beginning with those most expensive to expedite. After this, the noncritical activities can be treated asbefore.
  • 123. 8 Resource Management 8.1 ObjectiveThe completion of a construction project at maximum efficiency of time and cost requires the judiciousscheduling and allocation of available resources. Manpower, equipment, and materials are importantproject resources that require close management attention. The supply and availability of theseresources seldom can be taken for granted because of seasonal shortages, labor disputes, equipmentbreakdowns, competing demands, delayed deliveries, and a host of associated uncertainties.Nevertheless, if time schedules and cost budgets are to be met, the work must be supplied with thenecessary workers, equipment, and materials as they are needed on the job site. This chapter discussesmethods and procedures involved with the management of these three resources. Money, anotherproject resource that requires close management control during the construction process, is discussedin Chapter 11.The basic objective of resource management is to supply and support the field operations so thatestablished time objectives can be met and costs can be kept within the construction budget. Fieldsupervisors can achieve favorable production rates and get the most from their workers and equipmentonly when the requisite ways and means are optimally available. It is the responsibility of the projectmanager to identify and schedule future job needs so that the most efficient use is made of theresources available. The project manager must determine long-range resource requirements for generalplanning and short-term resources for detailed planning. He must establish which resources will beneeded, when they must be on-site, and the quantities required. Arrangements must be made for theirtimely arrival with regular follow-up actions taken to ensure that promised delivery dates are kept.Where shortages, conflicting demands, or delays occur, the project manager must devise appropriateremedial measures. The project plan and schedule may have to be modified to accommodate or workaround supply problems. The scheduling and allocation of workers, equipment, and materials areinterrelated. An action affecting one often affects the others in some manner. 8.2 Project Resource ManagementWith respect to resource management on construction projects, a few general observations at this stagecan serve as valuable guidelines for the practitioner. The long-term leveling of resources provides a goodindicator of future resource needs, but only from a general planning point of view. Detailed planningmonths into the future is unnecessary and is usually a waste of time. Detailed resource leveling has itsmajor advantage when applied to the near future (i.e., a maximum of 30 calendar days). Ample floatmakes efficient resource management possible, while low float values almost inevitably mean scheduledelays or the need for large variations in applied resources. The concept of float providing resourceefficiency becomes important in cases of dispute with the owner regarding the ownership of float.Disputes often occur when the owner orders extra work to be done but declines to grant additional timeto the contractor because the added work is not on the critical path.The highway bridge is used to illustrate resource management procedures throughout this chapter. Inactuality, the resource planning and scheduling for the highway bridge would almost never be doneindependently of the several other parts of the Example Project or even of other company projects. Theobvious reason for this is that there are usually conflicting demands for the same limited resources fromother job sites. There will surely be instances where workers, equipment, and materials will have to betraded back and forth among the various Example Project segments to achieve maximum use of theresources available.Resources often must be allocated on a project-wide or company-wide basis, with some system ofpriority being established among the separate sources of demand. This is a complex and difficultproblem for which only partially satisfactory solutions are possible. Management action in this regardcannot be stereotyped but must be based on judgment and economic factors intrinsic and unique to theparticular situation. To develop the basic principles of resource management, the ensuing discussiontreats the highway bridge job as if it were a totally separate and autonomous unit. These sameprinciples will provide management guidance where multiple construction sites are involved.
  • 124. 8.3 Aspects of Resource ManagementA prerequisite to manpower management is a detailed analysis of the labor requirements necessary tomeet the project schedule. Previous chapters have provided detailed information regarding the specificmanpower demands of each operation and the time frame within which these operations are to becompleted. Using this information, the project manager may then compare these needs with anestimate of available manpower to determine whether the project schedule is generally achievable.Once this calculation has been performed and no adjustment to the overall job completion date appearsnecessary, the project manager may then turn his attention to leveling out the peaks and valleys in labordemand.If the labor requirement take-off discloses that the demand will exceed the supply, the managementsituation can become considerably more complex. In such instances, time or cost overruns are almostinevitable. Remedial measures to combat an inadequate labor supply can include diverting labor fromnoncritical to critical activities, or resorting to some method of expediting the critical activities. Thestretching out of noncritical activities, or the use of overtime or subcontracting on critical activities, maymake it possible to maintain the originally established schedule, but often at an additional cost.Otherwise, the project manager faces the difficult task of allocating the available labor in a way thatoffers the greatest advantage while minimizing the duration of project time overruns.With respect to equipment management, most of the major decisions concerning how the job is to beequipped were made at the time the job cost was estimated. Nevertheless, it is the responsibility of theproject manager to see that the job is properly and adequately equipped. In a manner analogous to thechecking of labor needs, a compilation is made of the total equipment demand on a daily basis. If thereare conflicts among project activities for the same equipment items, rescheduling of noncritical activitiesoften will solve this problem. If this is not possible, working overtime, on weekends, or multiple shiftsmight circumvent the difficulty. Another solution might be to arrange for additional items of equipmentto be supplied from some outside source. If excessive equipment demands cannot be ameliorated inone of these ways, alternative equipment types or construction methods may need to be explored. Suchchanges from those used to estimate and price the operation may have substantial cost and timeimplications for the project and must be analyzed carefully. Should no other acceptable alternativesexist, the conflict must be removed by rescheduling activities with the least possible increase in projectduration and cost.Material management on a construction project is essentially a matter of logistical support. Jobmaterials in the proper quantity and specified quality must be available at the right place and time. Allaspects of material procurement, from ordering to delivery, are directed toward this objective, and apositive system of checks and controls must be established to assure its realization.Subcontractors can and often do play an important role in achieving project time and cost goals.Although there is much variation in actual practice, subcontractors typically provide their own workers,equipment, and materials. The project manager will seldom have any direct voice in the management ofsubcontractor resources. Rather, the manager’s responsibility usually will be one of ensuring thateach subcontractor commences work at the proper time and processes the work in accordance with theestablished time schedule. 8.4 Tabulation of Labor RequirementsThe management of construction workers begins with a tabulation of labor needs, by craft, for eachproject activity. Figure 8.1 is a take-off of the general contractor’s labor requirements for thehighway bridge. This figure does not include the manpower needed by subcontractors, such as thoseundertaking the reinforcing steel and painting. Much of the information contained in the figure is readilyavailable from the original estimate in those instances where labor cost was estimated using crew sizeand production rate and the activity involved only one cost account. For instance, Figure 3.6 shows oneforeman, one cement mason, six laborers, one equipment operator, one oiler, and one carpenter as thecrew to pour the abutment concrete (activities 200 and 250). These labor requirements are entereddirectly into Figure 8.1. In doing so, it is assumed that the crew foreman will be a carpenter;consequently, a requirement for two carpenters is entered for activities 200 and 250. Similarassumptions regarding craft foremen are used throughout Figure 8.1. Where the labor cost wasestimated initially by using a unit cost, crew sizes assumed when activity durations were beingestimated can be used (see Section 5.4).
  • 125. If activities involve more than one cost account and, correspondingly, more than one crew, thedetermination of their labor requirements is less direct. To illustrate this point, activities 90 and 120both involve abutment excavation. As indicated by Bid Item No. 1 and Bid Item No. 2 of Appendix A,each of these activities involves two different cost accounts: excavation, unclassified and excavation,structural. It was assumed in the planning stage of the highway bridge that the unclassified excavationwould be performed with a tractor-dozer and would be done for both abutments in a single operation.Once this work is completed, the structural excavation will be done first for abutment #1 and then forabutment #2. Thus, activity 90 is really the unclassified excavation for both abutments as well as thestructural excavation for abutment #1. This is reflected in the original plan with a three-day duration foractivity 90 and two days for activity 120. This is the rationale for the workers listed for these twoactivities in Figure 8.1.Figure 8.1Highway bridge, activity manpower needsFigure 8.2Highway bridge, daily manpower compilation
  • 126. 8.5 Project Labor SummaryWith the information given in Figure 8.1 and the time-scaled network shown in Figure 5.14, it is an easymatter to determine the projected daily labor needs for the highway bridge based on an early startschedule of operations. Figure 8.2 is the labor summary for this project. Using the available floats ofnoncritical activities, it is possible to smooth or level the peak demands for manpower revealed by thefigure. (Methods for doing this are discussed later in this chapter.) The early-start labor requirementsusually serve as the best starting point for any adjustment that may be required of the daily labordemands. However, it must be noted at this point that an early start schedule often turns out to beinefficient in terms of cost and resources.An important characteristic of the highway bridge is revealed by the labor compilation in Figure 8.2. Ifthe early start schedule is followed, there will be a period of time during which no work can proceedbecause of the lack of materials. After the abutment forms are built and the excavation is completed,the job will be at a standstill for seven working days awaiting delivery of piles and reinforcing steel. Thisis clearly disclosed in Figure 8.2 by the seven-day gap in the project labor requirement after the first fewjob operations have been finished. Often enough, the early start of field operations only results in asubsequent delay while awaiting the receipt of key resources. This matter is discussed further in Section9.4 with regard to preparing field schedules.The labor summary of Figure 8.2 provides information concerning the local labor market and whether itcan be expected to provide the numbers of tradesmen required. However, contractors seldom makesuch a labor take-off purely to ascertain the adequacy of the labor supply. They usually assume that theywill be able to hire sufficient workmen, but this matter often deserves more attention than it gets. Thecontractor’s experience and knowledge of local conditions are valuable guides in this regard. Severeshortages of certain labor skills occur in many areas of the country during peak construction periods.Arrangements to bring in workers with the requisite trade skills from outside areas must be made well inadvance. Contractors will find that advance knowledge of the labor demands of their projects can be ofconsiderable value in the overall planning and scheduling of their field operations. 8.6 Variation in Labor DemandFor purposes of discussion, we will assume that there will be an adequate labor supply for the highwaybridge, or at least that the peak demands can be smoothed sufficiently for supply to meet demand.Figure 8.2 reveals that the requirements for different crafts vary widely and are at times discontinuous.Some variation in time demand for a given craft is normal because labor crews typically build up tostrength at the start of the job and decline toward the end. However, the pronounced grouping of laborneeds at different points during the construction period is decidedly undesirable and impractical. The
  • 127. recurrent hiring and laying off of personnel on a short-term basis is troublesome, inefficient, expensive,and scarcely conducive to attracting and keeping top workers. New tradesmen on the job are not asefficient as they are after they become familiar with the work involved. This is a learning curvephenomenon, where a crew’s production goes up and its unit labor costs go down with taskrepetition. Then, too, there is the practical consideration; when workers are laid off for a few days, theymay no longer be available and they may be difficult to replace. 8.7 Manpower Leveling“Manpower leveling†is the process of smoothing out daily labor demands. Perfection in thisregard can never be attained, but often the worst of the inequities can be removed through a process ofselective rescheduling of noncritical activities. On the highway bridge, crews are largely comprised ofcarpenters and laborers. For purposes of discussion, the process of manpower leveling on the highwaybridge will address only these two crafts. Because of the discontinuous nature of their work on thisproject, no amount of smoothing can level the daily job requirements for equipment operators,ironworkers, cement masons, and pile-drivermen. On the highway bridge, these workers will have to beprovided when, and as, they are needed. It is for this reason that specialty crews often are shifted backand forth among company jobs. This kind of irregular labor demand often prompts general contractorsto subcontract portions of their work.The peak demands and discontinuities for carpenters and laborers on the highway bridge can be leveledto some extent by using the floats of noncritical activities. To illustrate the basic mechanism by whichresource smoothing is accomplished through rescheduling, a simple example will be discussed. Figure8.3 (see insert between pages 184 and 185) shows the daily requirements of the highway bridge forcarpenters and laborers. These data are summarized in the form of two histograms to illustrate thepeaks and valleys of labor demand required by an early start schedule.Figure 8.3 has been prepared by plotting, for each activity, its daily demand for the designated crafts.Each activity is assumed to begin at its early start time. Opposite each activity, and under the workingdays during which it will proceed, is entered its daily labor demand. The symbol “C†is used forcarpenters and “L†for laborers. The labor totals indicated by the histograms are obtained byadding vertically the labor demand for each day. The information contained in Figure 8.3 assumes thatthe same size crew will be used throughout the duration of any given activity. For activities that havelong durations, this assumption is probably not justified. Generally, the crew for such an activity willstart small, build up to full force, and taper off at the end. The assumption of constant crew size isreasonably accurate, however, for short-duration activities such as those used on the highway bridge.Figure 8.3 discloses that there is a peak requirement for 10 laborers on project working day 6. This peakis caused by the fact that activity 80, requiring three laborers, and activity 90, requiring seven laborers,are both scheduled to be under way on the same day. A usual way to remove or minimize such a conflictin an early start schedule such as Figure 8.3 is to move one of the conflicting activities to a later date.When a noncritical activity with no free float is moved to a later time to level a resource, any succeedingactivities must be adjusted forward by a like amount. If free float is available, the finish of therescheduled activity can be postponed by an amount of time that is less than, or equal to, the amount offree float without affecting any of the following activities. Hence, when adequate free float is available,schedule changes to accomplish resource leveling are easily made. However, when a scheduleadjustment bumps a whole chain of succeeding activities forward, all the resource needs of succeedingdays can be affected substantially, thus complicating the calculation. These changes may serve toimprove the overall situation or may only further complicate it. In the case of the 10 laborers needed onworking day 6, Figure 5.4 shows that activity 80 has 19 days of total float and 19 days of free float.Activity 90 has 12 days of total float and zero days of free float. This labor conflict can be remediedeasily by moving either activity 80 or 90 to a later date; movement of activity 80 is preferable. 8.8 Heuristic Manpower LevelingA number of operations research techniques are available for obtaining optimal solutions to manpowerleveling problems. Numerous algorithms are available to accomplish such a time-critical analysis, butmany of these require a computer to handle as few as two resources. Even on relatively small projects,these procedures can require large amounts of computing power. For this reason, heuristic methodsoften are used. Heuristic methods involve the application of approximations to solve very complexproblems. As the resource information developed in these models is based on estimates, and subject to
  • 128. many external and unpredictable factors, a heuristic solution to manpower leveling offers sufficientaccuracy for construction operations and provides a good basis for understanding manual methods ofresource leveling.In the absence of a resource-leveled schedule, field supervisors intuitively prioritize the commitment ofresources to operations. On any given workday, prior to the start of shift, the field supervisor reviewsthe resources available for the day and lists the critical activities to be accomplished. If after coveringthese critical operations, additional resources remain, the field supervisor will initiate other operationsusing any remaining resources. The decision as to which other operations receive resources is based onhow close they are to becoming critical.A simple manual heuristic method is used in Figure 8.4 (see insert between pages 184 and 185) to levelthe demand for carpenters and laborers on the highway bridge. The method presented is based onpriority rules that give reasonable results when used with a modest number of labor resources. (In thecase presented here, the number of resources is two: carpenters and laborers.)The priority rules mentioned pertain to the order in which project activities will be rescheduled fromtheir early-start condition. In essence, the entire project is rescheduled. The critical activities are givenhighest priority and are therefore scheduled first. The noncritical activities are then scheduled withpriority given to those activities with the earliest late-start dates. When more than one activity has thesame late-start date, preference is given to the one with the least total float. The algorithm progressesthrough Figure 8.4 one day at a time, with activities being scheduled according to the priority rules justdescribed. In this example, maximum limits on the daily labor demand have been set at three carpentersand seven laborers. These limits have been set equal to the maximum labor demands of individualcritical activities, as shown in Figure 8.1. 8.9 Numerical ExampleIn Figure 8.4, the basic information given in the left-hand columns is a list of activities on the highwaybridge, together with the resources needed, duration, and late start value for each activity. The first stepin the leveling process is to schedule the critical activities by listing the manpower required for eachunder the appropriate working days. Because critical activities 10 and 60 do not require labor, activity180 is the first critical activity to be scheduled. It starts on day 26, finishes on day 29, and requires threecarpenters and three laborers for each of its four days. Labor demand limitations are based on themaximum demands of the critical activities. Therefore, all critical activities can be scheduled for thesame dates required in the original early-start schedule. If the labor demand of a critical activity were toexceed the supply, it will not be possible to keep the project within its originally planned duration unlessspecial measures are taken. This case is discussed in Section 8.11.After all the critical activities in Figure 8.4 have been scheduled, noncritical activities are scheduled inthe order of their late-start dates. The first of these is activity 40, which must start no later than day 12.This activity, along with all the other noncritical activities, is scheduled to start as early as possible,subject to previously established resource limitations. Commensurately, it is scheduled to begin on day1 and end on day 3. The activity with the next earliest late start is activity 90, with a late start of day 15.Because activity 90 follows activity 40 (see project network in Figure 5.1), activity 90 cannot bescheduled to start until day 4. When activity 90 is scheduled from day 4 through day 6, the projectmanpower limits are not exceeded, and its scheduling is acceptable. In a similar manner, activities 100,110, 120, 130, and 140 are scheduled in the order of their late-start dates. Each activity is scheduled asclose to its early start as possible while allowing the start date to slip as necessary to remain within theresource limits. It should be noted that activity 80, which can start as early as day 4 based on thenetwork logic, has been allowed to slip to day 14 in order to maintain resource levels. Once all of theactivities preceding critical activity 180 have been scheduled, it is noted that there is a six-day gap duringwhich no resources are required. This is the same network characteristic that was noted in Section 8.5,where an early start of work on the site serves no purpose because of the delivery times required forpilings and reinforcing steel. As a result of this gap, all of the noncritical activities scheduled up to thispoint can be moved to the right in Figure 8.4 by at least six working days.An important point must be made here. The logic of the network diagram shows that the start of fieldoperations need not occur until day 12. The resource histograms in Figure 8.4 show that the start can bedelayed six days without impacting resources. What this emphasizes is that float is necessary to allow
  • 129. for the shifting of activities to use resources efficiently. Both the time consideration and the resourceconsiderations are important. A decision regarding “move in†is discussed in more detail in Sec on9.4.A comparison of the labor demand histograms in Figures 8.3 and 8.4 shows that the leveling efforts haveresulted in considerable improvement. For example, the peak requirement for laborers has droppedfrom 10 to 7, and the number of days during which there is no need for laborers has been reduced from15 to 12. However, if the opening activities were to be delayed by 6 working days, as describedpreviously, the number of days when there will be no need for laborers will be further reduced from 12to 6 working days. The leveled labor demands shown in Figure 8.4 are far from being uniform. In thisregard, it must be mentioned that resource smoothing can be especially difficult on a project of limitedextent with a large proportion of critical activities, as is the case with the highway bridge. The totalExample Project would provide a much more flexible basis for making significant and meaningfulleveling studies. The process just described is referred to as resource allocation, with time as the criticalelement. When the number of available resources is critical, a slightly different process is required, andis described in Sections 8.11 and 8.12. 8.10 Labor Leveling in PracticeThe smoothing of labor demands from those shown in Figure 8.3 to those in Figure 8.4 is performedevery day by field supervisors all over the country. However, field supervisors usually perform thisfunction in an intuitive and informal way. Through extensive experience, good site supervisors havedeveloped a talent and instinct for manning a construction job efficiently, if not optimally. Manpowerleveling, as a formal management procedure, is not standard practice in the construction industry.Rather, field supervisors generally are left to their own devices with regard to the field management oflabor crews. While developing the ability to make these manpower decisions informally on a daily basisis sufficient for relatively simple projects with fairly constant resource demands, more complex projectswill benefit substantially from formally completing the calculations. In addition to developing a betterindication of overall project manpower requirements, these computations provide the project managerwith a more realistic picture of the true criticality of project operations.Figures 8.3 and 8.4 are attempts to resolve a complex matter with a simplified job model and heuristicrules. In reality, the starts and finishes of activities will never be defined as acutely as they are in thenetwork diagram. There is almost certainly a degree of activity overlap that is not represented in theCPM diagram. Nor is the job logic truly as rigid as it is made out to be. Tradesmen are shifted about fromone activity to another as they are needed. The daily fluctuations shown in Figure 8.4 for laborers willnot really occur during the construction period. A relatively stable labor crew of five or six workers willbe on hand throughout the job. A form of Parkinson’s Law takes effect, and every worker is keptbusy, even when more laborers are present on a given day than Figure 8.4 indicates actually would beneeded.Manpower leveling, using present-day algorithms, is a trial-and-error process and is made difficult bythe fact that most activities use more than one labor classification as well as different types ofequipment. A shift that improves one resource often complicates one or more other resources, eitheron that day or on succeeding days. Despite its limitations, manpower leveling does provide valuableinformation relative to the efficient use of job-site labor. Even if formal leveling studies are notattempted, the adopted rules of thumb pertaining to the priority of activity rescheduling can provideconsistent and useful guidance. For example, it can be emphasized to field supervisors that critical andlow-float activities have manpower priority and only those activities with large float values are to beused as fill-ins. Another guide for field supervisors could be to save the available float on activities forpossible later use in resource leveling. Where people and equipment are not needed elsewhere,activities, even those with large float values, should be started as early as possible. On large andcomplex projects, or on jobs where the supply of labor is known to be limited, formal leveling effortssuch as those previously discussed can provide valuable advance information for project management. 8.11 Restricted Labor SupplyThe preceding example of labor leveling involved a case where only the rescheduling of noncriticalactivities was required to keep the job labor demands within established limits. Now assume that thiscondition is no longer true: There is a labor shortage situation that presents project management with aconsiderably more difficult rescheduling problem than that previously encountered. The basic
  • 130. implication of a labor shortage is that the durations of certain activities must be extended beyond theirnormal values if the manpower deficiency cannot be overcome by expediting actions such assubcontracting the work or working overtime. Subcontracting may well be the best answer, but suchaction depends on circumstances and will not be discussed further here. In any event, a restrictedsupply of manpower may or may not affect the overall project duration. Yet whatever the circumstance,if overtime or subcontracting cannot alleviate the situation, the contractor then has the problem ofallocating, to best advantage, the available labor among the activities.The first item to check when a craft shortage is expected is the requirement for this particular laborresource by the critical activities. Consider critical activity 330 on the highway bridge. This activityrequires three carpenters per day for four days. Based on an 8-hour day, this would amount to 96 man-hours of carpentry work. If there are only two carpenters available, the contractor has a decision tomake. If the activity is staffed by only two carpenters and if the usual 8-hour day is worked, the durationof the activity will be increased to six days. Because this is a critical activity, the project iscommensurately delayed by two days. However, the project duration will be unaffected if the twocarpenters work 12-hour days (4 hours of overtime) while engaged in this activity. Some carpentertenders (laborers), and perhaps other trades, would probably also have to work overtime with thecarpenters to keep the work in phase. Therefore, the project manager must analyze the situation anddetermine whether a two-day delay to the schedule would be more costly overall than the associatedovertime needed to alleviate the labor shortage.With regard to labor deficiencies on noncritical activities, the first action is to stretch out the duration ofeach activity concerned sufficiently to keep the labor requirement within the supply. However, whenthe extensions of noncritical activities equal or exceed the available floats, the contractor must againseriously consider the use of overtime. Otherwise, new critical paths and subpaths will materialize,possibly superseding the original critical path and delaying the entire project. These activities are oftenreferred to as resource-critical activities. 8.12 Complex Labor SchedulingWhen labor shortages of several crafts are involved, and overtime is not a satisfactory solution, thematter of scheduling the available labor to minimize the project delay takes on an even greater degreeof complexity. This situation mandates the use of a resource-critical analysis. This is a trial-and-errorprocess that involves allocating the available labor to the activities while maintaining the necessary joblogic to achieve project completion in the shortest possible time. In such cases, the complexity of thesituation normally will preclude obtaining an optimal solution. The heuristic method described inSections 8.8 and 8.9 also works well for resource-critical analysis. The durations of some critical activitiesprobably will need to be extended or decisions made to expedite them. Critical activities requiring moreof a limited resource than is available will have to be reexamined and probably will result in longerdurations. The major difference in resource-critical scheduling is that both critical and noncriticalactivities are scheduled together, with priority given to those with the earliest late-start date. With a capplaced on specific resources, inevitably some activities will be delayed beyond their late-start date. Theresult is, of course, delay to the project completion date. At this point a decision must be made:expedite the delayed activities or delay the project. The best solution the project manager can hope foris to arrive at a practical compromise that appears feasible and reasonably efficient.When deemed desirable and feasible, activities can be scheduled discontinuously at irregular timeintervals. License to do this is, of course, dependent on the nature of the activity. Some job operations,such as a concrete pour, must be continuous (each day following the previous without intermittentpauses). Activities such as rubbing concrete or prefabricating concrete forms, however, can beperformed intermittently and serve well as fillers. In fact, this is probably how activity 270, “Rubconcrete, abutment #1,†and ac vity 300, “Rub concrete, abutment #2,†of the highway bridgewill be accomplished. This would be especially true for activity 300 because, as shown in Figure 5.14, if itis started at its early-start time, it will parallel the setting of the steel girders. Performing both of theseactivities simultaneously could be unsafe, and activity 300 can afford to be delayed. Deck forming,pouring, and stripping are also possible safety conflicts with activity 300. Undoubtedly the jobsuperintendent will put the cement masons to work rubbing abutment #2 whenever an opportunitypresents itself.
  • 131. Much attention has been given elsewhere to the matter of complex resource scheduling. At present,such resource scheduling gives a good approximation of the total resource quantities needed and theirapproximate timing. It illustrates graphically that network float is often an illusion, being in fact theleeway necessary to schedule resources efficiently. When complex labor shortages occur that cannot beavoided by overtime or subcontracting, skilled and experienced field supervisors are probably betterable to work out an acceptable daily schedule as the work progresses. It is the project manager’sduty to identify labor shortage problems well in advance, make the decisions necessary to minimize theproblem, and allow sufficient time for the field superintendent to complete the job while allocating theavailable labor on a daily basis. 8.13 Equipment ManagementOn projects that require extensive spreads of construction equipment, the project schedule andproduction costs are largely determined by the level of equipment management exercised on-site.Therefore, the next considerations are important to the proper selection, use, and maintenance ofequipment on the job.• To the maximum extent possible, equipment sent to the job should be of the type that will bestperform the work under actual job conditions. Knowledgeable company personnel, such as the projectsuperintendent, equipment supervisor, and master mechanic, should be consulted before finalequipment selections are made. Equipment sizes should be matched to the production schedules, andequipment spreads should be balanced so that each unit delivers maximum production. Standardizing ofbrands helps to simplify maintenance and repairs.• Work should be planned and scheduled to achieve the fullest use of every equipment item. Idleequipment costs money; thus, it is wise to make advance arrangements for replacement equipmentwhen a unit is scheduled for repairs or overhaul. Standby units of key equipment items, such as pumps,may save many times their cost.• Field maintenance should be a part of the pre-job planning. It is difficult to overemphasize theimportance of day-to-day maintenance to proper equipment operation. A systematic program ofpreventive maintenance is a vital part of field equipment management, and compliance with establishedprocedures should be checked. It is advantageous to keep on hand a supply of routine maintenanceparts, such as hoses, belts, filters, and so forth. The occasional cleaning of engines and cooling systems isan important aspect of machine care. Routine fueling and lubricating should be scheduled to minimizeequipment downtime. A skilled and dependable person in charge of the equipment service truck is oneof the most valuable people on the equipment team. Planned equipment downtime should be aconsideration in the schedule, as one hour of preventive maintenance is generally worth five hours ofunplanned maintenance in the event of a critical component failure. Planned downtime removes onlyone machine from service; an equipment failure often takes an entire spread of equipment out ofproduction.• Repair services may be provided by the contractor’s central equipment shop or by a nearbyequipment dealer. What is important is that the facilities be capable of getting the machines back intoproduction as quickly as possible. Attempting major repairs in the open and under primitive conditionsis poor practice. A good and conscientious mechanical supervisor in charge of repairs plays a key role inkeeping equipment operating properly. Poor repairs mean breakdowns and lost production. Repairs andmaintenance often can be scheduled for nights or weekends to minimize lost production time. Keepinga minimum inventory of commonly used repair parts and tire sizes can pay big dividends. When majorrepairs are scheduled, the necessary parts should be on hand before bringing the machine into the shop.It is good practice to clean and thoroughly check equipment before moving it from one job to another.• The production rate of an equipment unit depends on the operator and his field supervisors. Popularfield supervisors normally have a following of top equipment operators. Close supervision of operatorsand their equipment is as important as it is for a labor crew. A poorly performing operator, besidesbeing ineffective, also impedes the production of an entire equipment spread and endangers theirsafety. In an attempt to get the fullest production, some operators abuse their machines, causingbreakdowns and repair costs. Constant supervision is required to achieve consistently good productionrates. Often the replacement cost of a large piece of equipment is nearly equal to the profit on theproject. Clearly, equipment abuse is never worth extra production.
  • 132. • The temptation to overload equipment in an effort to get more production is common true withearth-hauling units. However, equipment is designed to do its best in the long run when loaded only toits rated capacity. The production gained by overloading normally will be more than offset by theadditional costs of repairs and tires and the shortened life of the machine.• Actual production rates and costs should be checked on the site for each major piece of equipment.High repair costs may be indicative of worn-out machinery, inadequate equipment maintenance, oroperator abuse. High unit costs of production may signal improper equipment selection for the job, poorfield supervision, improper functioning of the equipment, spread imbalance, or operator inefficiency.• In order to achieve the greatest efficiency with an equipment spread, project managers regularlyanalyze operations to determine whether another unit of equipment is needed or should be removed.Changes in hauling patterns, material consistency, weather, and surface gradients occur on a daily basis.The optimal equipment crew is an ever-changing target, and the project manager who maintains thisefficiency makes money. 8.14 Equipment SchedulingMaintaining a daily resume of project equipment needs serves a variety of purposes. Figure 8.5 is acompilation of the daily equipment requirements for the highway bridge, based on early-start dates. Atime-scaled project network, such as Figure 5.14, is very useful when information of this kind is beingobtained. On larger and more extensive projects, it might be desirable first to make a tabulation ofequipment needs by activity, as was done for labor in Figure 8.1. Figure 8.5 will quickly disclose anyconflicting demands among activities for the same equipment items. Actually, many of the duplicatedemands for equipment are eliminated when the project logic is being developed. The plannerinstinctively detects and eliminates obvious overlapping needs for equipment as the job planningproceeds. Nevertheless, until Figure 8.5 or its equivalent has been developed, there is no formal way ofchecking for equipment conflicts.When an equipment conflict does occur at this stage, it can be removed by rescheduling one of theactivities involved by using its float or by adding a precedence restraint to the project network. Adding aprecedence restraint means using a dependency line to show that one of the activities involved mustfollow the other rather than parallel it. The precedence arrow between activities 110 and 140 in Figure5.1 is actually a resource restraint used to avoid conflicting demands for the crane and pile-driving crewon the highway bridge. Figure 8.5 does reveal a conflicting requirement for the 50-ton crane on workingdays 21 and 31. The conflict of demand on day 21 will be used here to illustrate how this situation canbe resolved. Figure 5.14 shows that activity 150, “Pour footing #1,†€œDr ep les bu me #2 € b re u re e r e e s me r r me b e el m e s u l em r e r e T s s ree s l l ble Apre e e e rr r m ul ls rem e e l b re u r p le r bu me #2 be mple e be re p ur # A pre e e e rr e pp s e re ul rem e e e u pme l bu ul re u re e p le- r re el ree s be ee bu me s # #2 s ell s re-r e r e r p le rA r r mus be expresse sp re r e use pre e e e res r s leres ur e em s T e pre e e e res r s perm e s lu m be emp r rpr blem F r s e e pre e e e rr r m ul em srl l rel s p be ee em e e ere el e r eek r m re Res ur ele el pr es rm s l ul le e s me Us res ur eres r s r res spe res ur e s e e rk m use e s e ulebe me m sle ese res ur e s s ul e u rresp jus me sbe m e e pre e e e s ru ureFigure 8.5H br e l e u pme mp l
  • 133. I su e l s l ble perm res e ul e r r ll be e e ex e s e pr je ur r e ee r pr je expe W e e res ur e res r er s e u pme r er l b r e r r s e l l er es s e ulmul ple s s r br l e u pme s r - erm b s s O pr je s ere e u pme s m j r res ur e s s ble r u e u pme -le el pr e ure s s es r bepre usl s p er r l b rO e e re l lues e u pme s e ule s s l ses ps e ee r ere u pme ems F r ex mple e e rl -s r s e ule rms e b s s r F ure 8 s sl er ll be re u re e br e j b s e ere mes b r b k llpurp ses L r e e u pme s expe s e m e j b s es r ble m m ze sum es F ure re e ls 28 €œB k ll bu me # € s sx rk s ree l us be e erre up sx s u e er W e s s eb bu me s be b k lle mme e su ess el er ee be m e r m ej b l eT e e u pme s e ule F ure 8 be er e b r r s s e le r es ur r us ems e u pme ll be re u re e j b Su s e ule s use ul l r e br e j b bu ls s u e r e er ll ll mp e u pme ep pel e rel ee r m er p r s e ex mple pr je O er mp pr je s re ereb se e u pme ee s s ell s e u pme l bl I e u pme mus be br u r m er s ur es e e u pme s e ule e bles e pr je m er e mple e e pr je ee s I sk p e e e u pme ll be le r ppre ble per me ll be ee e er p r e Ex mple Pr je e r rm e e re u r per ps s e ule e u r rep rs m e e r er ul A ppr x m e le r s e ule pr je e u pme ee s s use ul re s 8.15 Software ApplicationPer ps m re er p se s ru pr je m eme e mpu er s me up lm s spe s ble r le mpl s e e e res ur e le el T e s e ul umer us es e re u r s mb res ur es be mes ex remel mplexm u l pr e ures u kl be me pr l mp ss b l es T p l mpu er s e ul ppl s
  • 134. ll e user ss sm s sep r e res ur es e T e s r bu eres ur e er e ur e be es bl s e es u T llus r e u s res ur e A be ss e e rs u s 2 ree u s el s T s rms res ur e re u reme s r m r res ur e A r e e rk T eres ur es s r bu e er e rk es e s res ur e re u reme s r m es e e e mplex res ur e le elC mpu er pr r ms ls m ll e e res ur e l bl s r m re pr jeres ur e I s r ex mple r e be s e ule be l ble e pr je r m Ju e 2 r u Au us 3 e mpu er ll s su lz ur per I e per me ur e r e ll be su e ll be e r l e urs e ul S me es re e e be errup ble; s e be emp r r l s ppe e r res ur es use er s less lAll ese mpu er pr r ms re eur s ep e l r ms be ex remel mplexE e s e s ll pr u e l ppr x m e resul s be use e re m r bles use u elb exper e e s ru super e e T e el super s r ll subs u e l r er umbersem sk lle l b rers r sk lle rkm T e super s r m ls s e ule sele e er me e e pre br e ssembl e rl er r use l er e e res ur es re s r suppl rsubs u e l r er l ble p e e e u pme pl e sm ller eru l ze e T ere re m p s l ble e el be e e e pr r mme s e uls reS e ul s re e prese s e p le el res ur es e umber res ur es xe r e mple e es bl s e W res ur es el pre e erm e le els e pr je ur sex e e s e res ur e l m W e me s el s e pr r m pre s em mum umbers res ur es re u re T e pre s e er e b e mpu er ll e ess r l rem u e s e pr je es E e m r es ur s rl ll use e s re ree lu e e pr je mple el m es b k r e e e se le ele res ur esA res ur e-le el pr r m s use ul r e lu ee e rk es e e pr je me s e ule C es e rk b e er s me mes e e e e r lpresul l m r ex r me T s p s s usse Se 2 A sp s su e s es e pr je re u e l lues p ll lue e res ur e re u reme s T ese mp s be e e b l e urre umber res ur es s ru e res ur e-le el eur s e res ur e- r lm e bser e m u me e pr je s bee el eA mp r e ure res ur e le el b mpu er s e b l e er e re s bl ur eres ur e pre s r e ex rk s T s rm e bles e el super s rs e e pr blems r e u e u ure pe em A e s me me e me r me ss r e u ur l es ll em m le e res ur e le els 8.16 Material Scheduling eme r l er m er ls s er e e sur e m er ls re ej b s ee e e re u re u es u l es T e r r €™s pur se r er us m r lpres r bes e u u l pr e el er e m e r sp r r e m er ls ere T e u u l ll m er l el er es re er e b spe u es ( e ess r ) s e rr e Ap r r m ese s r pr e ures m eme r l j b m er ls s re e pr m r l r e e r mel el er s e s r e C s er ble mee r e bee expe e e el p rk s e ule ll s s me res ur e l m sI s ul be b us e er s s e ule s me less u less s supp r e b e r ble el er m er lsLe mes r m er l el er es e lre bee lu e e pr je s e ule T s s mpl s e b rp r ppr pr e m er l sr s e r l pr je e rk T ese sr s ere b se e el er erms lu e e m er l u s re e e r m e rs e ej b s s be es m e T e represe e mes re u re rs p r ppr l
  • 135. m er l br el er ej bs e T e m x mum ex e p ss ble ese le mes ebee bu l e per l s e uleImme el er e s ru r s bee s e s e ess r x e e l e es b pur se r ers r e r us pr je m er ls mus be ssue e suppl ers I e se e br e e r lp lu es e prep r s p r s e el er e bu me e k re r s eel Imme el ssu s pur se r er b e e ess rs p r ppr ls br el er s m er l re e s eps m j r mp r eN e e rk s e ule re u res e m er l be ej bs e ll r e el er er l e erm es e l es p ss ble r er e r p r ul r em m er l T e el erper lu es e mes e ess r r pur se r er prep r r sm l s p rprep r ppr l br e m er l s pp er l us ms le rper s ppl ble O e b ss s rm e pr je m er prep re pur se r er s e ule r e use s mp €™s pr ureme ep r me T s s e ule ll ll e e ess r pur s rm s ell s e e l e e b e r er mus bepr esse r sm e e e rEs bl s me e r er le me s mp r spe m er l r l Ample pr s musbe m e r e el er er l s e r prese ll r u resee el s su s e re u re resubm l rre e s p r s e r e -e eer s el super s rs e pr u e e e e ur e e e rl r er m er ls be use e re r s s sur e e m er ls ll be l ble e e re ee e S er e r s bees e pur s pers el re pr e bu u e j b mple el T s s e p l s epr e es l s m be pr blem I s e ess r e er r e m er l el er es l sel e pr ress e rk I s e u es r ble e ex ess el e rl el er ej bs eP les u ee e m er ls le ser us pr blems e m e e er pr e er ere e j b per s re l T ere s s pr l r : E rl m er l el er b e e r re u res e r r expe u s per ps be er ppl e else ere e meI e se er res r e urb j b s es e re ul s e ul m er l el er es s espe ll mp r E rl el er es be r u e emp r r s r e l es e r re e b e r r e ere s su ble l er e T s es e er l e e l expe sess r e l sur e r e W e -s e m er l s r e s use el er ej bs emus be p e su e me m ke e e ess r rr eme s T s ppl es p r ul rl es e re s ere perm s p l e es r s - ur el er es m be l e Ire e e rs e es m e s ss e e rl pur se s r e m er ls s bee u u e e be e s e rl el er m s ru pr je s s le e p jus - - me e r m eme p l s p use e u m b le us r W e er r u ssr e r er s usu ll se rr e r e el er m er ls ej bs es rlbe re e re ee e 8.17 Subcontractor Scheduling eme r l sub r rs e ers r u em ej b e e re ee e e sur e mpl s e r rk r e e es bl s e j b s e ule T ere re ree m s er s l e rr u s resp s b l F rs e pr je m er s ul sul e e m j r sub r rs ur e pl s e ul e pr je I esub r r p r p es prep r e j b s e ule e m ell e be er ppre r er le e pl s ur s ru e be er u ers s rk s e pr jepl s le O e s sm ll m er s e ere e be ee sub r r l espr je per rm e e ers T e se s er s e rm e esub r reeme A re ull r e ume spe re u reme s erms subm ls ppr ls s e ule e s re e e pr je m er €™s b sub r r mpl e T e m e ssu e sub r s s ssue ere be use pr me r r rm ll ll pr ee sub r prep r mme el er e s ru r sbee s e
  • 136. T e r s er s ssur e sub r rs r er e r m j r m er ls mple memee e s ru s e ule S me e er l r rs s ble m r ersub r rs €™ m er l pur ses T s s s me mes mpl s e b lu sub rre u reme e sub r r subm u pr e p es s pur se r ers e e er l r r s er re e p e sub r I s e e er l r r ersee e expe e sub r rs €™ m er ls l sI m er s m l r r m er l r er e pr je m er mus es bl s le - mes e ule r sub r rs e e mus rep r e pr je T ese es rees bl s e eb ss e pr je rk s e ule le me m r r m e eekm r m re Sub r rs mus be e e u e me pl e r rk m e es eN es be l s e r l l r er e r ppe r e As e e e rr es e pr je m er ses e sub r r r s rep r e ll s s up elep e ll I s e u ll mp r r e pr je m er ssure e j b s mple el re r e sub r r m e pr ee s rk e e l 8.18 Resource ExpeditingAs me e e rl er s ru ex e erm €œexpe € e ffereme s Expe s ppl es pr je s re s s usse C p er 7 As use ere €œexpe € re ers e s ke ssure mel m er l el er sub r rsupp r r e pr jeI su ru e e s pul re u re el er e pur se r er s u r ee e e r ll el er s e ule Ne er es le er u m ll e suresub r r ll m e e pres r be T e pr je m er s expe resp s b l m ke sure m er l sub r mm me s re me He m rr u e expe s msel r s mp m e expe ep r me A ull- me expe r s s me mesre u re l r e pr je O rk ere e er s espe ll er e j b mple r ere m er l el er s p r ul rl r l e er s me mes ll p r p e e r r per e expe e rsA e ess r ju e expe u sm e e e k- s s em r l ere em s eps e m er l el er pr ess re re r e S r e ssu e e pur se r er e re r ee s be kep e re e p s p r s e r subm l e r e -e eer e re e p ppr e p es e re ur e ppr e r s e e r e el er m er ls Be use s p r s r m sub r rs re subm e r ppr l r u e e er l r r e e k- s s em ll lu e m er ls be pr e b e sub r rsT s s es r ble be use pr je el s e b l e m er l el er s lue e bpr es e m er l T s s me ume pr e ure s ll e r s mples m ll er es re e-m x es s er subm l rm re u re Ge er l r rs s me mes e ess r r l m er l ems e erm e e m u urer €™s pr u le r ess e ule re u re me r sp r es e er e rr er s pmer u T sk rm s espe ll elp ul r u pr u r sp r r us r kes er el sE s ep e ppr l m u ure el er pr ess s re r e e s us ll m er lss e ke l A re ue er ls m er l s us rep r s r r e e pr je m er r s rm T s s s em e bles j b m eme s urre m er l suppl ser es s e rl - r e e e sl pp es el er es seem l kel urT e e s e el er s us m er ls e pr ress sub r rs reexpe e epe s e l e es er e Cr l es r b us re s s musbe e m s l sel e I el s ppe r r m r su es s r ppr pr es e ess r Le ers xes elep e lls pers l s s r er m be re u re keeppr ress s e ule L - l es be s m l rl e r ze be use l m r sl pp e ese be ler e be re e be me r l I pr r m es be mes e ess r b usl ul be es bl s e eb ss s e l lues
  • 137. Weekl j b mee s ll m j r suppl ers sub r rs be er elp ul T e pr je e rk up e s e ule l es m er l s us rep r be me e b s s r e r ese mee s T e e re mpe r uble sp s e bles e rl rre ebe ke
  • 138. 9 Project Time Management 9.1 Time Management SystemU l e pr je me m eme s s em s e r e rk pl s e ul A per l pl e le le r s e ule e bee prep re mee pr je bje es T s lu es e ess r pr je s r e res ur e le el e ble pr r e s r s ru T e rk pr ee ssur e e e re j b s bee r u l su e l ze T e m x mum ex e p ss ble r uble sp s e bee e e rre e s bee ke el m e em A pl s e ule e bee e se ll pr e spe u e r ee e expe us mpl s me e rk Pr je m eme s s s e mpleme e pl e el es bl s pr ress m r rm ee b k pr e ure T e me m eme s s em s e ere e exe u p seI s x m pl e er be ll ble r e pl er p ss bl p e e er u ure j b r ums e e Pr blems r se e er ul e bee resee A erse e er m er l el er el s l b r spu es e u pme bre k s j b e s e r ers umer us er s srup e r l pl s e ule T us er s ru per s mme e ere mus be u l e lu el per rm e s mp re e es bl s e s e ule C s er ble me e r re re u re e k l ze e me pr ress ej b ke e er m be re u re e er br e rk b k s e ule r m e s e ule re le e j b s T ese s s ue e m r res e ul p ses e me m eme s s em re esubje s s uss s p er 9.2 Aspects of Time ManagementI e r me s e e es bl s e me ls s ru pr je mus be meT e e me m eme se ue e s F ure 9 s repe e re ul rl er e l e e pr je T e urre per l pl s e ule s es bl s e pr je me sr s u erp e me m eme s s em F r r - b k r -p ss l ul s b se e l es ers ej b e rk pr u e rk s e ule le r es e r es r s e pr je T s s e ule s use r e - - me r l e pr jeSu s s em s u es e e e e rl - r e e r ee e ere e pr jem be ll be s e uleT e rk pl e er mus resp s pr je bje es re be mpl s e su ess ull I e er ll me s e ule s ru per s be me eremus be ee me sl pp es pr mp l r u es bl s e s s em pr ress ee b k r m e el T e m r p se me m eme l es e per me sureme u lj b pr ress e el s mp r s e pl e bje es Pr je m r ere re l es e e erm rk u es pu pl e e rep r s rm rm su ble r s mp r s e pr r mme j b s e ule Ne rk es s ueuse ul e e b s s r pr ress me sureme rep rFigure 9.1T me m eme le
  • 139. A re ul r er ls e s e pr je eme s bser e rep r e As e u e e s m e se es e bee mple e e e ree mple se es re pr ress Re e s rm b pr je m eme s l ses ere epr je urre l s e r be s e ule b mu Cr l es se l l lues re m re er l sel be use ers r e mp r e keep e pr jes e ule C rre e expe e l rk ems s ke er l ss e rep r epr ress re e ls p s re l bleN pr je pl r s e ule e er be per e e s ll e bl e el p s e pr jepr resses As resul e b sel e ers e s e ule ll be me re s l ur eu re l s s es sl pp es er l s e ule berr s ur C se ue l e e rk mus be rre e s ee e l ul s mus be up e s ll s e urre j b s e ule re le s u l j b exper e e e T ese up es e re e l s s r lp s subs l es e l s es T e l es up e s e ule re le s e u l urre j b s u es e urre b s s r pr je me r l 9.3 Key-Date SchedulesI rmul me s e ules be use r pr je r l s er mus be e lluse e rm O l r e j b su s e Ex mple Pr je er r s e ules m be ee e T e e l use e e prep r e j b s e ule be l r ble e le el m eme r s e e C se ue l ere s e ules reprep re re es e mee e p r ul r ee s e re p e Cr super s rs re er e l se es r e re resp s ble e r s e ul rm ee s be spe subs l e l S e ule rm e el pe r ers r e -e eers p-le el el m eme e er ll ll be erms m les es r ke es m j r se me s e pr je re pr r mme s r r sO e me es bl s er r s e ules s r u e use e pr je u l e es r be Se 6 s Appe x C T e ere le els u l e pr e e e W rkBre k S ru ure ss r us r ups e rk esT e pr je m er e Ex mple Pr je l kel ll be pr e ls ke es r e e se er l subpr je s l e I l s ll s u e m s er s e ule me ls ll bem re b pm eme ur e s ru pr ess F ure 9 2 prese s l ke - es e ule s bee prep re r e br e T s ke - e s e ule s b se le el e pr je ul e T e r l j b pl 7 - rk - ur s u e e b ss r eprese ere F r re s s l r e me-s r e s re e C p er 7 eres ur e le el C p er 8 re rr e r r s s uss
  • 140. E rl l e mes s usse C p er s u e e b s s r m s el s e ulesC r rs s e ul s re e use er mes r ese mes F r ex mple e rls rs s es re mm l e s €œs e ule € s rs fi s es S m l rl l e s r s s es re re ue l s s €œre u re € s r s fi s es T s e me l ure suse re r e br e s e ules s usse s p erI F ure 9 2 e s e ule es re e e rl -s r s mes r e s ru per sl s e Oper s 2 re ex ep s s be use j b r ums e ll be s usse e ex se T e es l s e F ure 9 2 e bee b e us e mes l s eF ure T ese ere e er e le r es us e le r F ure F ure 9 2represe s e rs rk ers ke - e s e ule r e br e s prep rebe re el per s u ll be C se ue l s me e es e F ure 9 2 pr b bl ll e s e rk pr ressesFigure 9.2H br e l ke - e s e ule 9.4 Adjustment of Move-in DateI m k up e ke - e s e ule s e F ure €œ e € s l l 2 rk s As ep e F ure 8 €œPre br e bu me rms € 9 €œEx e bu me # € €œ b l ze p le- r r € ll ll F ure s s ese es e l l s 9 2 3 s respe elW ll s me s s ese l es re s e ule mpl s e e r e rl mes el per s ll be s s ll r se er l s r e el er s eel p lesre r s eel C se ue l ere s be e b s r up el per s mme el Fr m me s p €œ e € e subse ue ree es ul be el e b s mu s 2 rk s u e e mple e T s el ul resul u us r l es r m €œ e € €œCle up € Fr m es p res ur es e er F ure 8 s s €œ e € ul be el e r sx rk s u erse e e res ur e emB se b me res ur e r er e pr je m er s e e e er €œ e € e ree ll es b e rk s ll le e ree s l l ble r u p e pr blems T s p s p eme ll e e pr je mple e ll el m e e e u e ess r us el per sU r u el su r m e e s e b e r r e use e er s er ble u less e m er s expl e be re T e r er re r s eel r ers s eel p l s s ll mus be e e e rl es p ss ble m me e er 9.5 Detailed SchedulesC s er bl m re e l s ee e b e mme e rk super s rs s lu e F ure 9 2T e s e super e e e br e ll re u re subs ll exp e me s e ule ll pr e - - re s el per s De le pr je s e ules re us m r lprep re us es s b s s D ere me rm be pr e re ere e e es su s e ules bu e rl s r s es re usu l Su s e ule s p ms
  • 141. e ere re usu ll m s es ere s s e ule ll be me be use lm eres ur es e ble el s me sl pp es Ne er eless pr je s e ule b se e rls r s s e e e er ll use es bl s pr je me bje es T e e le j b s e ule s ul ls e es re r l e lues ree l T s rm s s er bles e se re e rk e el L bel s r l s resses s mp r e l er-le el m ers K le e ree l s ls lu ble ers elsuper s rs e p ss b l us su ex r me mee u expe e j b sT e rele se l l lues el super s rs s l s s ere be pr e T l l u l ke ree l usu ll s s re b s r s r r ups es T e use l l ju e rm ll s e e l lues er es T l l be m sle se re l e l res r e p r s pr je O l epers resp s ble r e er ll s e ul e lu e r l e us e ll l l Free l s re l us ble mm le l l mus be re ull pp r e bk le e ble pl ersO l r e pr je s e le s e ules re prep re re r super s r sub r r E ese s e ules s e pr je e me pr r m e rk r p r ul r super s r sresp s ble T e me sp s ese s e ules re l m e p ll er l e ex eeks3 s T e m u me epe s s er bl e ure e rk l e I s sel m r le pr u e e le j b s e ules r m re m e T ere s ee rl er per s mu su s e ule m be re ere bs le e b subse ue esup es Re se up e s e ules re ssue s e rk es l T bul r l s s mpu er-pr e b r r s re e m s mm rms s r - erm rk s e ules T e e rk r m s er l e ess r ju e j b s e ules C p es e e rk be pr e e r us super s rs r m be kep e el eT e br e s su e l sm ll l e e le rk s e ule s re u re s r ej b super e e T e me s e ule r e rs m s ru per s ebr e s s F ure 9 3 €œ e € e ree ll es e bee el e b e rk s s s expl e Se 9 As e rk pr ee s e el e j bsuper e e ll e er e es e es u ll s r s e s e ules F ure 9 3 W rk s e ules l ke e e e ure re prep re r el super s rsm r m lu e rm er e el er j b m er ls Pr e r es sre r es me su rm s u mp r e super s r be use spers s ll er e m er ls re r ere e e ll rr e H e er es e ul m er l el er es s rm ll le sep r el r m e el per s T e pr jeexpe r pr es e pr je m er s e super e e per rep r s er es us j b m er ls s rm s rp r e e pr je eekl pr ress rep r s(see Se 9 ) C se ue l rk s e ules prep re r el super s rs e lu e l se es re p s l p r s e rk m m er l el er rm s pr esep r el As s s e pr e ure ll e ere m er l el er rm s lu eF ure 9 3Figure 9.3H br e l e le s e ule
  • 142. 9.6 Progress MeasurementT m ke per me sureme s pr ress e el e rk es ser e s ex ep ll e e p k es rk T e eme pr ress be expresse ere s T ree mm l use me s re: Estimated number of working days remaining to complete the activity2. Estimated percentage completion of the activity in terms of time3. Quantities of work units put into placeHow a contractor chooses to express activity completion depends on the type of work involved andwhether these same data are also used to check field costs. However, the number of working daysremaining to finish an activity is fundamental to the workings of project time management. Progressdata in the other forms are readily converted into days to complete by using these relationships: Working days to complete= d (1 − P/100) Working days to complete= d (1 − W/T)whered = total activity duration in working daysP = estimated percentage of completionW = number of work units put into placeT = total number of work units associated with the activityMost scheduling software allows the user to input progress in any of these formats and makes theconversion automatically. Inherent in the relationships is the assumption of a straight-line variationbetween time and work accomplishment. If an activity requires a total of four days for its performance,it is assumed that one-quarter of the work quantities to be installed will be completed each day. This isnormally an acceptable assumption if an activity is limited in scope. A more realistic relationshipbetween time and work accomplishment may have to be used where activities are of substantial extent.It is obvious that a time management system is no better than the quality of the input information. Ifprogress reports from the field are inaccurate, then management decisions will be made on the basis of
  • 143. fictitious situations. It is very important that progress measurements be done conscientiously and withreasonable accuracy. Management action must be based on what actually happened rather than onwhat should have happened. The person responsible for progress reporting must recognize theimportance of factual and correct determinations. Project progress records often are important insettling later disputes regarding project delays. In fact, progress reports can form the basis for claimsand litigation.The conclusion of a given activity must be viewed in terms of its substantial completion rather than itsabsolute finalization. As work progresses in the field, there are many items that, at least temporarily, arenot completely finished, as, for example, small deficiencies that are remedied subsequently when theopportunity presents itself. Progress reporting must make allowances for such minor shortcomings.Therefore, finish dates generally are recorded for substantial completion rather than the technicalcompletion of activities. 9.7 Progress ReportingHow often field progress should be measured and evaluated depends on the degree of time controlperceived to be desirable and feasible for the particular work involved. Within limits, the greater thefrequency of feedback and response, the more likely it is that the project time objectives will be met.However, this rule must be tempered with other considerations. For example, some kind of balancemust be struck between the cost and effort involved and the management benefit gained. Anotherconsideration is that the same field progress report often serves for field cost management (Chapter 10)as well as time management. Consequently, the cycle times for both management applicationsfrequently are matched.Fast-paced projects, using multiple shifts, may demand daily progress reports. Large-scale jobs such asearth dams, which involve a limited range of work items, may use a reporting frequency of a monthlybasis or even longer. It is difficult to generalize because management control must be consonant withproject characteristics and peculiarities. On projects of the size, duration, and type of the highwaybridge, progress reporting probably would be done on a weekly basis. This is the premise here. It shouldbe noted that although formal progress reporting may be made on a weekly or monthly basis, criticaloperations may need to be tracked with a quicker and less formal form of cost and production controland on a more frequent basis.The project manager must see that progress measurement and reporting are done properly and that theprogress information receives prompt management review and analysis. A standard procedure forcollecting and transmitting the weekly progress data must be established. Progress measurementrequires direct visual observation in the field by someone familiar with the type of work involved. Thismay include a physical count of work units in place or may be reduced to evaluating quantities of workaccomplished from the project drawings. At times, suitable measurement can come from deliverytickets for materials like concrete or load slips for earth moving. On many projects, the project managerpersonally carries out the measurement and reporting functions. Otherwise, a staff member, such as thefield engineer, will perform these duties. In any event, an independent review of work accomplishmentis preferred. Field supervisors are not usually best suited for progress reporting, because they are verybusy people who are not normally inclined toward handling paperwork of this kind. In addition, a fieldsupervisor may fail to report unfavorable progress in the hopes of working problems out later or maywithhold quantities for future use on a less fortunate day. 9.8 Bar ChartsOn receipt of progress measurements from the field, management must compare the information withthe latest project schedule. This can be done in different ways, depending on management preferencesand procedures. For example, a tabular listing can be prepared that shows the scheduled start and finishdates and the actual start and finish dates for each activity. Although progress data in this format maybe useful for some purposes, it is not usually the best medium for making a comprehensive evaluationof the current time status of construction operations.For the day-to-day time management of a project, some form of graphic display is effective andconvenient. A widely used method for recording job progress is the bar chart, the general characteristicsof which were discussed in Sections 5.29 and 5.30. Several different styles and conventions are used indrafting project bar charts. Two of the most common are described in Sections 9.9 and 9.12, and both
  • 144. are widely used by the construction industry. One procedure is used to depict progress on the highwaybridge as of July 14, and the other method is the basis for the July 21 progress report. For obviousreasons, the contractor would use the same bar-charting procedure throughout the construction periodof the highway bridge. The two styles are mixed here so the workings of each can be observed.The bar chart is an excellent medium for recording progress information and portraying the current timestatus of individual activities or other project segments. However, it is not a proper tool for evaluatingthe overall time status of the project or for planning corrective measures when the work falls behindschedule. Only the project network can perform this function adequately.The manual preparation and updating of project bar charts can involve considerable time and expense.Software is widely used to print out updated bar chart schedules. When project outlines are used for aWork Breakdown Structure, bar charts of differing levels of detail can be produced with ease. 9.9 Highway Bridge as of July 14Figure 9.4 has been prepared to show progress on the highway bridge up through the week endingWednesday, July 14 (working day 22). This bar chart shows the scheduled and actual beginning andcompletion dates for each activity up through July 14. Plotted progress data have come from past fieldmeasurements that were made and reported at weekly intervals. Thus, this bar chart is updated once aweek and shows the current status of each activity and how its accomplishment compares with theschedule. Practice varies concerning the entry of material deliveries and other resource information onbar charts. In this book, the bar charts portray the advancement of the physical aspects of the work onlyand do not include dates for material deliveries or the availability of other resources.In Figure 9.4, the upper row of shaded ovals for each activity extends between its scheduled start andfinish dates. As has been discussed, bar charts customarily are made up on an early-start basis; however,exceptions to this general rule on the highway bridge are the first four activities listed in the figure. Asexplained in Section 9.1, the scheduled beginnings of these four activities have been delayed by nineworking days beyond their early-start times. The white ovals that extend to the right of the noncriticalactivities represent the total float.Figure 9.4Highway bridge, bar chart as of July 14
  • 145. The lower row of black ovals opposite certain activities shows the time period during which workactually progressed on these activities. The start of each of these rows is plotted at the date on whichwork commenced. The line is then plotted to the right at weekly intervals, either to the current date orterminating at the day of completion. For each activity, the cumulative percentage completion isentered at the right end of the lower line until it is completed. The numbers 0 and 100 on the lower linesshow the actual time periods required to progress from zero to 100 percent completion. If an activity isin process at the time of a progress measurement, but not yet completed, the actual percentage ofcompletion is marked. An example of this is activity 140, which was only 30 percent completed on July14, the date of the last progress report. Comparison of the actual and planned percentage completionsas of a given date reveals the time status of an activity then in progress. One advantage of the form of
  • 146. progress recording used in Figure 9.4 is that it provides an exact historical record of calendar times whenjob activities were actually in process.An examination of the figure will provide a quick and informative review of how the job progressed as ofJuly 14. Activity 40, “Move in,â€â€œPr f r f r †k rk g g r fi H r fr f r r r T r 12 “E #2 †Pr gr 1“Dr #2 †f r TJ 13 I 3 r f fJ 1 Fg r 9 1617 J 1 ff r r 9.10 Weekly Progress ReportsT r r g f rk f g rf r r r gr r g kj g r g f ff r r r rf r g r r g r T f r r r f f Fg r 93 rk r gr T r r r r Fg r 95 k r gr r r fW f r J 21 ( rk g 27) g r g B r r r r f r r g g k r gr r r g r k g r q rf r r r r r f f k r gr r r r j r rFigure 9.5Hg r g k r gr r rT r r r r j g k r gr r r r r r f r r f r gr E f r gr r k r r( S 1 ) r r r f r r r r q D r gr r r r k r gr r r Fg r 95S r q r r g fr r fg r T r r f g f r f r g r f r r g k T f r r r r rr r r f r f kr r r r T r r( 6 ) r J 15 ( r g r J 19) 65 “F r r k r r †r r g 9 ( rk g ) r 13 rk g fr f k r gr r r Fg r 95Pr gr r r g k r r r r g r f r r T f k ff T f k k r gr r rf r g r g r (C r1 ) T W r r r gr r P r r f Fr r r r r g r W r
  • 147. r r r k g Fr f r r r g r W T g r r r r r rj r r r r fr q W ff f r k r f r r r g M r g f r gr W f r g k r f f r gr r f r g r I r r r r r r g r gW f r r gr r r T g r r f k f r ff r 9.11 Field Progress NarrativeT k f r gr r r r f rr f r jf r F r g r f j f r r -f ff r r f r f r j r r g g g f r f Fg r 9 r gf r #2 r T k r gr r r f r ff r f r g k gr f r g g f r f 9.12 July 21 Status of Highway BridgeT r gr f r Fg r 95 r j r r Fg r 96T r r r g J 21 R r r ff r r g r r gr r r O r r j Fg r 9 Fg r 96 r gr ff r fI Fg r 96 r - r f r rz f r T rf r r rr rz g fr r- -f T f r r ’ f W g fr r g rk r gr r r r gr f r r r gr r r R r r gr f r f r T r r g f r r r r f rk F r 1 r r Fg r95 r f f r f J 21 I F g r 9 6 r f g f rf r 1 T r f r r f r If r gr r r r g f rT f f r gr r r g k r g r f r f ff rFg r 96 fJ 21 r r r f f J 21 f 1 16 19 21 23 r g r rrg f J 21 f 1 f T f r f r grr r g Fg r 96 r r r r f r r r f r j r r rk r grFigure 9.6Hg r g r r fJ 21
  • 148. R f r Fg r 96 1 “Dr #2 †r fJ 21 r rk g T r rk fr r g f g #2 F g r 5 1 19 21 23 g ff W r ff r r g rk ( S 9 15) Fg r 96 1“F r r r #1 †fi f T r f r r ( 6 ) rk g r r rg 9.13 Progress AnalysisT fj r gr r r r r g ff f f r r j r g T f f j f r r f g C r g f g f r r r q r r g rk Pr f r gr r r g r g f rW r gr r r r fr f f rr f r r fr T q k k If r r f r r r j g f r rr r r If r r k r j k If r f rT k r f r T j g r r f ff r k O f k g r - r r r -f r - r r g r r r g r g (LS) -f r r g r f f (LF) T r r r If LS r j r g rr If f LF r r j r LF
  • 149. r k k f f (TF) If f r -f (EF) TF r If q TF r f r If r TF r r g r f rg r r j k f rr T f rO g r g fJ 21 1 “Dr #2 †r r ff g rj r R f r Fg r 5 1 LF f2 Fg r 95 r r f rk g 27 f rk g r f 29 C q 1 r r r r g rkN g Fg r 5 1 rg f f r r gf g EF f 21 r f r T r f g r r (6 rk g ) r j f k g r r ( g g ) f 69 rk g S rg r j r 7 g f g r r f g r g ff f 1 r f g r g T r f r jk g f f r gr r r(J 21) T S 9 16 9.14 Corrective Action f r r gr r r z r g rr f r q r S r r q r r r rr r g r j r W g f rk g g r g r r g f f r #2 r r W r g f r g f rk g r j g g r r k g f r f rr I g r r r k r :• g f r r r r f• S fr r r• T r ff r r r r• L g g rk rf r rW r f r f rr r r r j r j r C r 7 rr r f r g r f r T r r r r g r z r rk g f rk g f r f g r r f If r r g f rk f k r gr r r g g g r f f jC q ff f g rr r k r r r g rkT r r f r j g r g rj r gr g H k k r f r r r j g f r r j r r r r r rr r r r r r g g r f r f r r fj f r r j r r F - -f r r g g r fr j rr k g rk
  • 150. j r gr g g r g f r f rr r j ff 1 Dr r r r k g rk g g g r q T g r g 16 “D z r gr g †r r 1 “F r &r r #1 †D C r5r q r q r f r g f f r r r f r #1 T q r g r r r f r f r g g f r r #1 T r 16 r r r q f r 1 F r 16 r r qf r 2 “F r & r r #2 †T g g T ff f j g g r S 9 16 9.15 Network Updating r r r fr rU f r j r r g r g r j g R r r g g r r ff r r j rg f r r f r r fr r gr r r f r r r r g rk g r r gr f r r g g T r r rk gT j f r rk g rr r j r g U g r rr r f j r g r r r r g r g k j r g ff f r -r r rU g k g r rk rr r g f I r r r g ff f g r f r j I r r r r fr r gr rr r f r gr r r rFr f g ff f k r grr r g I k j g - - f rk r r f r r H r r ff r N f r r g g f rk T f r r r r f r r T r f g r r r g g k r j f r gr rf r r r g T r ff rr rr j W r f rk r f f rkU g r r g f r g r S 9 16 r r g f rB f r rk rr r f f r r g g r f rk rf r T r T r r r T r f r g r fr rr r j f g ff rT k rk f r f ff r q r r g rk f r:• N rk• E g r• C g j g
  • 151. • C g rg r r r rr r• E r r• C g r• C g f rkW r g r f r f r r j j fr f r rj r F r r j r r f r r f r f r r gr r j r T f r r r r f r g g T r f rr g r g r r r r f r r g r r r f I r f r j f r r — r f r rg f r r fFg r 97 rz f r f r g g r g f f r fJ 21 T f r f r r j k r grr r Fg r 95 I 5 r r r f f r I 6 S 91Figure 9.7Hg r g rk f r 9.16 Manual Updating CalculationsT rf r g r g fJ 21 ( rk g 27) f r Fg r 97 fr r r r j rk F g r 9 ( r g 232 233) rr r gr f r r f f I fg r f 27 r f f f rk r r r gr r“J 21 D 27 †F r r g r f rk g r T rr g f f rk f 27 f r f rr r r r f gr r Fg r 9 r g r k g g F r r f q z r rf r gr q T r r “E †r q (27 ) C r r g g f rk g r r f q z r r r f r r r rT Fg r 9 r g EF f 27 f r r ES f 27 f r r
  • 152. T r Fg r 9 r r f r r f k r Tf r r f 27 r j 71 rk g T j rg T q g g S 91 g j r r r g #2 ( 1 ) r ff T j r fr f rk g T - k k r Fg r 9 r g r j r f 71 T r r - r C r gFg r 9Fg r 51r r f r fr rg S g f f r r rr rk r grf If r j r f 7 1 “C g â€r f r f r T r r r r r f r T r r r ff r g g rU rk Fg r 9 r r r f f N g r r r r f j r gr T r q r r j r r r r r g f r g f r r f f rk k r r f j r gr r g r r 9.17 Scheduling SoftwareS g f f r r r r j g S f g r r g f r r f r S r f r r g r r f r r T f r gr f r r g f r r q r g ff r S g f r g f rj f r r r j g r R r r r f r f g r r Fr r g r f r g g r r f rf r r f r r - f r f r r fj g f r r g f r r r f f r r f r T f r g r g :• E r r f• S r r f r r gr• S f f f• T f r gr g f r f r• r r j f r j rr r rr• Or g r r f f r g• I f f r• F fT f r g r g r