The document discusses project network development and analysis. It defines a project network as a diagram that depicts the sequence, dependencies, and timing of project activities. It then: 1. Explains how networks are developed from work breakdown structures and used for scheduling, budgeting, and identifying critical paths. 2. Describes the activity-on-node approach and basic network terminology like activities, paths, and critical path. 3. Provides examples of network development, computation of early and late start/finish times using forward and backward passes, and determining slack.

1. Developing a
Project Network
CHAPTER 6

2. WHERE WE ARE NOW..

3. Project Network
–A diagram that graphically depicts the
sequence, interdependencies, and start and
finish times of the project activities
 The network is developed from the information
collected in the work breakdown structure
 Provides the basis for scheduling labor and equipment.
 Provides an estimate of the project’s duration
 Provides a basis for budgeting cash flow
 Tool that highlights activities that are “critical” and
should not be delayed
 Help managers get and stay on plan

4. From Work Package…
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
FIGURE 6.1
WBS/Work Package- Sample
McGraw-Hill/Irwin 6–4

5. …to Network
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
FIGURE 6.1 (cont’d)
Network based on prior WBS Sample
McGraw-Hill/Irwin 6–5

6. Terminology
Activity: an element of the
project that requires time. It
represented as a “node” (box)
Merge activity: This is an
activity that has more than
one activity immediately
preceding it.
Burst Activity- This
activity has more than one
activity immediately
following it.
McGraw-Hill/Irwin 6–6

7. McGraw-Hill/Irwin 6–6
Terminology
Path: a sequence of connected, dependent activities.
Critical path: is the longest path through the activity
network from the beginning to the end that allows for the
completion of all project-related activities.

8. BASIC GUIDELINES TO FOLLOW IN DEVELOPING
PROJECT NETWORKS
McGraw-Hill/Irwin 6–8
1. Networks typically flow from left to
right.
2. An activity will be performed in
sequence.
3. Unique, sequential ID.
4. Arrows can cross over .
5. No Conditional statements.
6. Looping is not allowed.
7. With multiple starts, use a common
start node and similarly, use a
common end node.

9. Activity-on-Node (AON) Fundamentals
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–9
Two Approaches represent a Project Networks
–Activity-on-Node (AON)
Uses a node to depict an activity
–Activity-on-Arrow (AOA)
Uses an arrow to depict an activity

10. Activity-on-Node Fundamentals
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–10
FIGURE 6.2

11. Activity-on-Node Fundamentals (cont’d)
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–11
FIGURE 6.2 (cont’d)

12. Network Information: Example
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–12
TABLE 6.1

13. Automated Warehouse Partial to Completed Network
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–13
FIGURE 6.4

14. Network Computation Process
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
McGraw-
Hill/Irwin 6–14
• Forward Pass—Earliest Times
–How soon can the activity start? (early start—ES)
–How soon can the activity finish? (early finish—EF)
–How soon can the project be finished? (expected time—ET)
• Backward Pass—Latest Times
–How late can the activity start? (late start—LS)
–How late can the activity finish? (late finish—LF)
–Which activities represent the critical path?
–How long can it be delayed? (slack or float—SL)

15. Activity-on-Node Network
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–15
FIGURE 6.5

16. Activity-on-Node Network Forward Pass
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–16
FIGURE 6.6

17. Forward Pass Computation
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–17
1. Add activity times along each path in the
network (ES + Duration = EF).
2. Carry the early finish (EF) to the next
activity where it becomes its early start
(ES) or
3. The next succeeding activity is a merge
activity, you select the largest early finish
number (EF) of all its immediate
predecessor activities

18. Activity-on-Node Network Backward Pass
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
FIGURE 6.7
McGraw-Hill/Irwin 6–21

19. Backward Pass Computation
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–19
1. You subtract activity times along each path
starting with the project end activity
(LF − DUR = LS).
2. You carry the LS to the preceding activity to
establish its LF, or
3. If the next preceding activity is a burst
activity; in this case you select the smallest
LS of all its immediate successor activities to
establish its LF.

20. Determining Slack
(or Float)
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–20
• Total Slack
– The amount of time an activity can be delayed without delaying
the entire project
• Free Slack (or Float)
– The amount of time an activity can be delayed without delaying
connected successor activities
– Tends to happen as the last activity in a path before a merge activity
(when another path is the critical one).
• The critical path is the network path(s) that has (have)
the least slack in common.
– This class will avoid the confusion of negative slack! … thus all
projects will have their end activity have LF=EF
– So all critical path activities will have a total slack of 0.

21. Forward and Backward Passes
Completed with Slack Times
Copyright © 2006 The McGraw-Hill Companies. All rights reserved.
FIGURE 6.8
McGraw-Hill/Irwin 6–22

22. Extended Network Techniques
to Come Close to Reality
• Laddering
-under the standard finish-to-start relationship, the activity must be
100% completed before advancing to the next activity. If that activity
has a long duration and if that activity has a delay, that activity can be
broken down into segments using laddering so that the following
activity can begin sooner without delaying work.

23. Extended Network Techniques to Come
Close to Reality
• Lags
• The minimum amount of time a dependent activity must be
delayed to begin or end
• Lengthy activities are broken down to reduce the delay in the
start of successor activities.
• Lags can be used to constrain finish-to-start, start-to-start,
finish-to-finish, start-to-finish, or combination relationships.
Use of Lags:
1. Finish-to-Start Relationship
-The finish-to-start relationship
represents the typical, generic network
style used in the early part of the
chapter.
2. Start-to-Start Relationship
-An alternative to segmenting the
activities as we did earlier is to use a
start-to-start relationship.

24. Use of Lags:
3. Finish-to-Finish Relationship
-The finish of one activity depends on
the finish of another activity.
4. Start-to-Finish Relationship
-This relationship represents
situations in which the finish of an
activity depends on the start of
another activity.
5. Combinations of Lag Relationships
-More than one lag relationship can
be attached to an activity. These
relationships are usually start-to-start
and finish-to-finish combinations tied
to two activities.
Copyright © 2006 The McGraw-Hill Companies. All rights reserved. McGraw-Hill/Irwin 6–24

25. Example Using Lag Relationships—The Forward and Backward Pass

26. Hammock Activities
• Another of the extended techniques uses a hammock
activity.
• This type of activity derives its name because it spans over a
segment of a project.
• The hammock activity duration is determined after the
network plan is drawn.
• Are frequently used to identify the use of fixed resources or
costs over a segment of the project.
• Typical examples of hammock activities are inspection
services, consultants, or construction management services.
• Derives its duration from the time span between other
activities.

27. Hammock Activity Example

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