DetaileDetailed Structural Assessment
Southern Nevada Health District Main Building Las Vegas, NV
Prepared for
PGAL, Inc.
Prepared by
Walter P. Moore and Associates, Inc.
3883 Howard Hughes Parkway, Suite 190 Las Vegas, NV 89169
ETABS is structural analysis software used to analyze and design buildings. It was developed in 1975 by students and later released commercially in 1985 by Computers and Structures Inc. The Burj Khalifa in Dubai was one of the first major projects analyzed using ETABS.
To model a structure in ETABS, materials like concrete and steel must first be defined along with their properties. Frame sections for beams, columns, walls and slabs are then created. The grid is drawn representing the building plan. Beams, columns, walls and slabs can then be drawn by connecting nodes on the grid. Modeling tools allow modifying the structural model by merging joints, aligning elements, and editing frames.
Shear walls are rigid vertical structures in buildings that transfer lateral forces from other structural elements to the foundation. They resist forces from wind, earthquakes, and uneven settling that can tear a building apart. Shear walls maintain the shape of the building frame and prevent rotation at joints. They are especially important in high-rise buildings subject to lateral forces. Shear wall behavior depends on the materials used, thickness, length, and position in the building frame. They resist lateral, seismic, and vertical forces by acting as a rigid diaphragm that transfers loads to the foundations.
The document provides step-by-step instructions for modeling, analyzing, and designing a 10-story reinforced concrete building using ETABS. It defines the material properties, section properties, load cases, and equivalent lateral force parameters. The steps include starting a new model, defining section properties for beams, columns, slabs, and walls, assigning the sections, defining load cases, and specifying the analysis and design procedures.
This document discusses the analysis and design of reinforced concrete footings. It describes different types of footings including isolated, combined, continuous, and raft foundations. It also covers design considerations such as minimum thickness, concrete cover, reinforcement sizes and spacing, and critical sections. An example is provided to demonstrate the step-by-step design of an isolated square footing, calculating loads, sizing the footing, checking effective depth, determining steel requirements, and verifying hook and dowel bar needs.
This document provides an overview of different seismic analysis methods for reinforced concrete buildings according to Indian code IS 1893-2002, including linear static, nonlinear static, linear dynamic, and nonlinear dynamic analysis. It describes the basic procedures for each analysis type and provides examples of how to calculate design seismic base shear, distribute seismic forces vertically and horizontally, and determine drift and overturning effects. Case studies are presented comparing the results of static and dynamic analysis for regular and irregular multi-storey buildings modeled in SAP2000.
The document provides a 7 step process for modeling a structure in ETABS according to Eurocodes, including:
1) Specifying material properties for concrete.
2) Adding frame sections for columns and beams.
3) Defining slab and wall properties.
4) Specifying the response spectrum function.
5) Adding load cases.
6) Defining equivalent static analysis and load combinations.
7) Specifying the modal response spectrum analysis.
Earthquake resistant analysis and design of multistoried buildingAnup Adhikari
The document describes the seismic analysis and design of a multistoried reinforced concrete building. It discusses the objectives, background, literature review, methodology, and concepts for reducing earthquake effects. The methodology section explains the functional and structural planning, load assessment including gravity and lateral loads, preliminary design of structural elements like slabs, beams and columns. It also discusses drift calculation and load path. The design and detailing section provides details on the design of structural components like slab, beam, column, staircase, footing and basement wall based on Indian codes.
This document is a project report for the structural design of a residential apartment building in Lughaya, Somalia using the ETABS software. It includes the names of the 5 students in the group, the building design with plans and 3D views, load calculations, and the modeling and analysis in ETABS. The building has three main structures, and the report provides the dimensions and materials used for beams, columns, slabs, and walls. It also includes output from ETABS like moment and shear diagrams, load transfer, and rebar tables.
ETABS is structural analysis software used to analyze and design buildings. It was developed in 1975 by students and later released commercially in 1985 by Computers and Structures Inc. The Burj Khalifa in Dubai was one of the first major projects analyzed using ETABS.
To model a structure in ETABS, materials like concrete and steel must first be defined along with their properties. Frame sections for beams, columns, walls and slabs are then created. The grid is drawn representing the building plan. Beams, columns, walls and slabs can then be drawn by connecting nodes on the grid. Modeling tools allow modifying the structural model by merging joints, aligning elements, and editing frames.
Shear walls are rigid vertical structures in buildings that transfer lateral forces from other structural elements to the foundation. They resist forces from wind, earthquakes, and uneven settling that can tear a building apart. Shear walls maintain the shape of the building frame and prevent rotation at joints. They are especially important in high-rise buildings subject to lateral forces. Shear wall behavior depends on the materials used, thickness, length, and position in the building frame. They resist lateral, seismic, and vertical forces by acting as a rigid diaphragm that transfers loads to the foundations.
The document provides step-by-step instructions for modeling, analyzing, and designing a 10-story reinforced concrete building using ETABS. It defines the material properties, section properties, load cases, and equivalent lateral force parameters. The steps include starting a new model, defining section properties for beams, columns, slabs, and walls, assigning the sections, defining load cases, and specifying the analysis and design procedures.
This document discusses the analysis and design of reinforced concrete footings. It describes different types of footings including isolated, combined, continuous, and raft foundations. It also covers design considerations such as minimum thickness, concrete cover, reinforcement sizes and spacing, and critical sections. An example is provided to demonstrate the step-by-step design of an isolated square footing, calculating loads, sizing the footing, checking effective depth, determining steel requirements, and verifying hook and dowel bar needs.
This document provides an overview of different seismic analysis methods for reinforced concrete buildings according to Indian code IS 1893-2002, including linear static, nonlinear static, linear dynamic, and nonlinear dynamic analysis. It describes the basic procedures for each analysis type and provides examples of how to calculate design seismic base shear, distribute seismic forces vertically and horizontally, and determine drift and overturning effects. Case studies are presented comparing the results of static and dynamic analysis for regular and irregular multi-storey buildings modeled in SAP2000.
The document provides a 7 step process for modeling a structure in ETABS according to Eurocodes, including:
1) Specifying material properties for concrete.
2) Adding frame sections for columns and beams.
3) Defining slab and wall properties.
4) Specifying the response spectrum function.
5) Adding load cases.
6) Defining equivalent static analysis and load combinations.
7) Specifying the modal response spectrum analysis.
Earthquake resistant analysis and design of multistoried buildingAnup Adhikari
The document describes the seismic analysis and design of a multistoried reinforced concrete building. It discusses the objectives, background, literature review, methodology, and concepts for reducing earthquake effects. The methodology section explains the functional and structural planning, load assessment including gravity and lateral loads, preliminary design of structural elements like slabs, beams and columns. It also discusses drift calculation and load path. The design and detailing section provides details on the design of structural components like slab, beam, column, staircase, footing and basement wall based on Indian codes.
This document is a project report for the structural design of a residential apartment building in Lughaya, Somalia using the ETABS software. It includes the names of the 5 students in the group, the building design with plans and 3D views, load calculations, and the modeling and analysis in ETABS. The building has three main structures, and the report provides the dimensions and materials used for beams, columns, slabs, and walls. It also includes output from ETABS like moment and shear diagrams, load transfer, and rebar tables.
The document discusses the design of beams subjected to combined bending, shear, and torsional moments according to Indian code IS 456. It defines the two types of torsional moments, provides examples of structural elements that experience torsion, and explains the code's approach which involves determining equivalent shear and bending moments. The design procedure involves selecting a critical section and determining longitudinal and transverse reinforcement based on the equivalent internal forces. Numerical examples are also provided to illustrate the design process.
This document provides a tutorial for modeling and analyzing a G+10 reinforced concrete building using the structural analysis software ETABS. It outlines the step-by-step process for creating an ETABS model, including defining materials, sections, geometry, loads, supports, and running the analysis. It also describes how to display and interpret the results tabularly and graphically. The tutorial uses the architectural plans and specifications of the example G+10 building to demonstrate modeling the building, assigning properties, meshing, applying loads, and checking the model before running the analysis in ETABS.
The document describes a project report for the design and analysis of a G+22 building using the software ETABS. It includes an introduction to ETABS, the objectives of analyzing the high rise building to calculate loads and seismic behavior. It provides details on the codes used, plan and structural elements, material properties, load cases including dead, live, wind and earthquake loads. The procedure outlines the steps to model the structure, define properties, draw the frame, apply supports and loads, and check for errors.
The document discusses ductility and ductile detailing in reinforced concrete structures. It states that structures should be designed to have lateral strength, deformability, and ductility to resist earthquakes with limited damage and no collapse. Ductility allows structures to develop their full strength through internal force redistribution. Detailing of reinforcement is important to avoid brittle failure and induce ductile behavior by allowing steel to yield in a controlled manner. Shear walls are also discussed as vertical reinforced concrete elements that help structures resist earthquake loads in a ductile manner.
This document presents an example of analysis design of slab using ETABS. This example examines a simple single story building, which is regular in plan and elevation. It is examining and compares the calculated ultimate moment from CSI ETABS & SAFE with hand calculation. Moment coefficients were used to calculate the ultimate moment. However it is good practice that such hand analysis methods are used to verify the output of more sophisticated methods.
Also, this document contains simple procedure (step-by-step) of how to design solid slab according to Eurocode 2.The process of designing elements will not be revolutionised as a result of using Eurocode 2. Due to time constraints and knowledge, I may not be able to address the whole issues.
Staad.Pro Training Report or Summer Internship Ravi Kant Sahu
This repot is the brief discussion about staad pro and its results .How can we work on staad.pro, what are the step which are used to desin building structure in staad.pra .it is very advance software.
Analysis and Design of Structural Components of a Ten Storied RCC Residential...Shariful Haque Robin
This report has been prepared as an integral part of the internship program for the Bachelor of Science in Civil Engineering (BSCE) under the Department of Civil Engineering in IUBAT−International University of Business Agriculture and Technology. The Dynamic Design and Development (DDD) Ltd. nominated as the organization for the practicum while honorable Prof. Dr. Md. Monirul Islam, Chair of the Department of Civil Engineering rendered his kind consent to academically supervise the internship program.
A continuous beam has more than one span carried by multiple supports. It is commonly used in bridge construction since simple beams cannot support large spans without requiring greater strength and stiffness. Continuous prestressed concrete beams provide adequate strength and stiffness while allowing for redistribution of moments, resulting in higher load capacity, reduced deflections, and more evenly distributed bending moments compared to equivalent simple beams. Analysis of continuous beams requires determining primary moments from prestressing, secondary moments induced by support reactions, and the combined resultant moments.
This document provides information about a software module for designing reinforced concrete beams and slabs. It describes the module's capabilities for analyzing continuous beams and slabs under pattern loading and moment redistribution. It also summarizes the module's design approach, code compliance, analysis methods, and output capabilities like bending schedules.
This document outlines a seminar on modeling, designing, and optimizing a multi-story steel structure using ETABS. It describes a 10-story steel braced building model with elevator cores and shear walls. The model is subjected to vertical, seismic, and wind loads. The document discusses importing the architectural grid and 3D model from DXF files, creating beams, columns, and braces using the GUI tools, and applying static and dynamic loads. It also covers steel frame design, concrete foundation detailing, and creating output reports.
Ch7 Box Girder Bridges (Steel Bridges تصميم الكباري المعدنية & Prof. Dr. Metw...Hossam Shafiq II
1. Box girder bridges have two key advantages over plate girder bridges: they possess torsional stiffness and can have much wider flanges.
2. For medium span bridges between 45-100 meters, box girder bridges offer an attractive form of construction as they maintain simplicity while allowing larger span-to-depth ratios compared to plate girders.
3. Advances in welding and cutting techniques have expanded the structural possibilities for box girders, allowing for more economical designs of large welded units.
The document discusses proper detailing of reinforced concrete structures, which is essential for safety and structural performance. It provides guidelines and examples of good and bad detailing practices for common reinforced concrete elements like slabs, beams, columns, and foundations. Proper detailing is important to avoid construction errors and ensure the structural design works as intended under gravity and seismic loads.
This document provides a summary of the structural design considerations for a proposed 15,000 capacity cricket stadium in Providence, Guyana. It outlines the design philosophy, loads, materials and standards used. The main structures include stands, pavilions, service buildings on pile foundations. Beams, slabs and columns will be concrete or structural steel. Loads accounted for include dead loads, occupancy live loads, and wind loads per relevant British standards. Concrete grade and reinforcement sizes are specified.
This document summarizes the key aspects of box culvert design and analysis. Box culverts consist of horizontal and vertical slabs built monolithically, and are used for bridges with limited stream flows and high embankments up to spans of 4 meters. They are economical due to their rigidity and do not require separate foundations. Design loads include concentrated wheel loads, uniform loads from embankments and decks, sidewall weights, water pressure when full, earth pressures, and lateral loads. The culvert is analyzed for moments, shears, and thrusts using classical methods to determine force effects from these various loading conditions.
This document provides an introduction to prestressed concrete, including:
1. The basic principles of prestressing concrete by applying compressive stresses that counteract tensile stresses from loads. This allows for smaller member sizes.
2. The main advantages are smaller sections, reduced deflections, increased spans, and improved durability due to reduced cracking.
3. The two main methods are pre-tensioning, where strands are stressed before casting, and post-tensioning, where strands are tensioned after casting through ducts.
4. Uses include precast beams, slabs, piles, tanks, and bridges constructed with either precast or post-tensioned segments.
This document provides a summary of a book on concrete bridge design according to BS 5400. The book aims to provide guidance on applying the limit state design code for concrete bridges by explaining its clauses and comparing them to previous design standards. It discusses analysis methods, loadings, material properties, design criteria, and worked examples to illustrate the code's application to bridge elements like beams, slabs, foundations and composite construction.
Design of column base plates anchor boltKhaled Eid
This document discusses the design of column base plates and steel anchorage to concrete. It covers base plate materials and design for different load cases including axial, moment, and shear loads. It also discusses anchor rod types, materials, and design for tension and shear loading based on calculations of the steel and concrete breakout strengths according to building codes.
Earthquake Load Calculation (base shear method)
The 3-story standard office building is located in Los Angeles situated on stiff soil. The
structure of the building is steel special moment frame. All moment-resisting frames are
located at the perimeter of the building. Determine the earthquake force on each story in
North-South direction.
This document section describes design considerations for precast pretensioned concrete girders. It discusses typical girder sections and common span ranges. The key stages in precast girder design are described as transfer (when prestressing force is transferred to the concrete), service (when self-weight and permanent loads are considered), and ultimate (to resist factored loads). Three stages of stress development are discussed: transfer when prestressing occurs, stage IIA when the girder is erected and before the composite deck is cured, and stage IIB when the composite section develops. Standard precast girder types used in California include I-girders, bulb-tees, bath-tubs, and wide-flange sections,
Descriptive study of pushover analysis in rcc structures of rigid jointYousuf Dinar
ABSTRACT: Structures in mega cities, are under serious threat because of faulty and unskilled design and construction of structures. Sometimes structure designers are more concerned in constructing different load resistant members without knowing its necessity and its performance in the structure. Different configuration of construction may also lead to significant variation in capacity of the same structure. Nonlinear static pushover analysis provides a better view on the performance of the structures during seismic events. This comprehensive research evaluates as well as compares the performances of bare, different infill percentage level, different configuration of soft storey and Shear wall consisting building structures with each other and later depending upon the findings, suggests from which level of performance shear wall should be preferred over the infill structure and will eventually help engineers to decide where generally the soft storey could be constructed in the structures. Above all a better of effects of pushover analysis could be summarized from the findings. Masonry walls are represented by equivalent strut according to pushover concerned codes. For different loading conditions, the performances of structures are evaluated with the help of performance point, base shear, top displacement, storey drift and stages of number of hinges form.
Session 5 design of rcc structural elements PROF YADUNANDANAjit Sabnis
This document provides an overview of designing reinforced concrete (RCC) elements such as slabs, beams, columns, footings, staircases, and water tanks. It begins with defining design as sizing the structure to have a low probability of limit states like failure or excessive deformation being exceeded. Probability and real-world parameters like strain are considered rather than deterministic calculations. The general design process is outlined as preliminary sizing based on codes, defining loads and combinations, analyzing to get member forces, and designing reinforcement. Guidelines for preliminary slab, beam, and column sizing are provided based on span-to-depth ratios. Different slab types like one-way and two-way systems are also introduced.
The document discusses the design of beams subjected to combined bending, shear, and torsional moments according to Indian code IS 456. It defines the two types of torsional moments, provides examples of structural elements that experience torsion, and explains the code's approach which involves determining equivalent shear and bending moments. The design procedure involves selecting a critical section and determining longitudinal and transverse reinforcement based on the equivalent internal forces. Numerical examples are also provided to illustrate the design process.
This document provides a tutorial for modeling and analyzing a G+10 reinforced concrete building using the structural analysis software ETABS. It outlines the step-by-step process for creating an ETABS model, including defining materials, sections, geometry, loads, supports, and running the analysis. It also describes how to display and interpret the results tabularly and graphically. The tutorial uses the architectural plans and specifications of the example G+10 building to demonstrate modeling the building, assigning properties, meshing, applying loads, and checking the model before running the analysis in ETABS.
The document describes a project report for the design and analysis of a G+22 building using the software ETABS. It includes an introduction to ETABS, the objectives of analyzing the high rise building to calculate loads and seismic behavior. It provides details on the codes used, plan and structural elements, material properties, load cases including dead, live, wind and earthquake loads. The procedure outlines the steps to model the structure, define properties, draw the frame, apply supports and loads, and check for errors.
The document discusses ductility and ductile detailing in reinforced concrete structures. It states that structures should be designed to have lateral strength, deformability, and ductility to resist earthquakes with limited damage and no collapse. Ductility allows structures to develop their full strength through internal force redistribution. Detailing of reinforcement is important to avoid brittle failure and induce ductile behavior by allowing steel to yield in a controlled manner. Shear walls are also discussed as vertical reinforced concrete elements that help structures resist earthquake loads in a ductile manner.
This document presents an example of analysis design of slab using ETABS. This example examines a simple single story building, which is regular in plan and elevation. It is examining and compares the calculated ultimate moment from CSI ETABS & SAFE with hand calculation. Moment coefficients were used to calculate the ultimate moment. However it is good practice that such hand analysis methods are used to verify the output of more sophisticated methods.
Also, this document contains simple procedure (step-by-step) of how to design solid slab according to Eurocode 2.The process of designing elements will not be revolutionised as a result of using Eurocode 2. Due to time constraints and knowledge, I may not be able to address the whole issues.
Staad.Pro Training Report or Summer Internship Ravi Kant Sahu
This repot is the brief discussion about staad pro and its results .How can we work on staad.pro, what are the step which are used to desin building structure in staad.pra .it is very advance software.
Analysis and Design of Structural Components of a Ten Storied RCC Residential...Shariful Haque Robin
This report has been prepared as an integral part of the internship program for the Bachelor of Science in Civil Engineering (BSCE) under the Department of Civil Engineering in IUBAT−International University of Business Agriculture and Technology. The Dynamic Design and Development (DDD) Ltd. nominated as the organization for the practicum while honorable Prof. Dr. Md. Monirul Islam, Chair of the Department of Civil Engineering rendered his kind consent to academically supervise the internship program.
A continuous beam has more than one span carried by multiple supports. It is commonly used in bridge construction since simple beams cannot support large spans without requiring greater strength and stiffness. Continuous prestressed concrete beams provide adequate strength and stiffness while allowing for redistribution of moments, resulting in higher load capacity, reduced deflections, and more evenly distributed bending moments compared to equivalent simple beams. Analysis of continuous beams requires determining primary moments from prestressing, secondary moments induced by support reactions, and the combined resultant moments.
This document provides information about a software module for designing reinforced concrete beams and slabs. It describes the module's capabilities for analyzing continuous beams and slabs under pattern loading and moment redistribution. It also summarizes the module's design approach, code compliance, analysis methods, and output capabilities like bending schedules.
This document outlines a seminar on modeling, designing, and optimizing a multi-story steel structure using ETABS. It describes a 10-story steel braced building model with elevator cores and shear walls. The model is subjected to vertical, seismic, and wind loads. The document discusses importing the architectural grid and 3D model from DXF files, creating beams, columns, and braces using the GUI tools, and applying static and dynamic loads. It also covers steel frame design, concrete foundation detailing, and creating output reports.
Ch7 Box Girder Bridges (Steel Bridges تصميم الكباري المعدنية & Prof. Dr. Metw...Hossam Shafiq II
1. Box girder bridges have two key advantages over plate girder bridges: they possess torsional stiffness and can have much wider flanges.
2. For medium span bridges between 45-100 meters, box girder bridges offer an attractive form of construction as they maintain simplicity while allowing larger span-to-depth ratios compared to plate girders.
3. Advances in welding and cutting techniques have expanded the structural possibilities for box girders, allowing for more economical designs of large welded units.
The document discusses proper detailing of reinforced concrete structures, which is essential for safety and structural performance. It provides guidelines and examples of good and bad detailing practices for common reinforced concrete elements like slabs, beams, columns, and foundations. Proper detailing is important to avoid construction errors and ensure the structural design works as intended under gravity and seismic loads.
This document provides a summary of the structural design considerations for a proposed 15,000 capacity cricket stadium in Providence, Guyana. It outlines the design philosophy, loads, materials and standards used. The main structures include stands, pavilions, service buildings on pile foundations. Beams, slabs and columns will be concrete or structural steel. Loads accounted for include dead loads, occupancy live loads, and wind loads per relevant British standards. Concrete grade and reinforcement sizes are specified.
This document summarizes the key aspects of box culvert design and analysis. Box culverts consist of horizontal and vertical slabs built monolithically, and are used for bridges with limited stream flows and high embankments up to spans of 4 meters. They are economical due to their rigidity and do not require separate foundations. Design loads include concentrated wheel loads, uniform loads from embankments and decks, sidewall weights, water pressure when full, earth pressures, and lateral loads. The culvert is analyzed for moments, shears, and thrusts using classical methods to determine force effects from these various loading conditions.
This document provides an introduction to prestressed concrete, including:
1. The basic principles of prestressing concrete by applying compressive stresses that counteract tensile stresses from loads. This allows for smaller member sizes.
2. The main advantages are smaller sections, reduced deflections, increased spans, and improved durability due to reduced cracking.
3. The two main methods are pre-tensioning, where strands are stressed before casting, and post-tensioning, where strands are tensioned after casting through ducts.
4. Uses include precast beams, slabs, piles, tanks, and bridges constructed with either precast or post-tensioned segments.
This document provides a summary of a book on concrete bridge design according to BS 5400. The book aims to provide guidance on applying the limit state design code for concrete bridges by explaining its clauses and comparing them to previous design standards. It discusses analysis methods, loadings, material properties, design criteria, and worked examples to illustrate the code's application to bridge elements like beams, slabs, foundations and composite construction.
Design of column base plates anchor boltKhaled Eid
This document discusses the design of column base plates and steel anchorage to concrete. It covers base plate materials and design for different load cases including axial, moment, and shear loads. It also discusses anchor rod types, materials, and design for tension and shear loading based on calculations of the steel and concrete breakout strengths according to building codes.
Earthquake Load Calculation (base shear method)
The 3-story standard office building is located in Los Angeles situated on stiff soil. The
structure of the building is steel special moment frame. All moment-resisting frames are
located at the perimeter of the building. Determine the earthquake force on each story in
North-South direction.
This document section describes design considerations for precast pretensioned concrete girders. It discusses typical girder sections and common span ranges. The key stages in precast girder design are described as transfer (when prestressing force is transferred to the concrete), service (when self-weight and permanent loads are considered), and ultimate (to resist factored loads). Three stages of stress development are discussed: transfer when prestressing occurs, stage IIA when the girder is erected and before the composite deck is cured, and stage IIB when the composite section develops. Standard precast girder types used in California include I-girders, bulb-tees, bath-tubs, and wide-flange sections,
Descriptive study of pushover analysis in rcc structures of rigid jointYousuf Dinar
ABSTRACT: Structures in mega cities, are under serious threat because of faulty and unskilled design and construction of structures. Sometimes structure designers are more concerned in constructing different load resistant members without knowing its necessity and its performance in the structure. Different configuration of construction may also lead to significant variation in capacity of the same structure. Nonlinear static pushover analysis provides a better view on the performance of the structures during seismic events. This comprehensive research evaluates as well as compares the performances of bare, different infill percentage level, different configuration of soft storey and Shear wall consisting building structures with each other and later depending upon the findings, suggests from which level of performance shear wall should be preferred over the infill structure and will eventually help engineers to decide where generally the soft storey could be constructed in the structures. Above all a better of effects of pushover analysis could be summarized from the findings. Masonry walls are represented by equivalent strut according to pushover concerned codes. For different loading conditions, the performances of structures are evaluated with the help of performance point, base shear, top displacement, storey drift and stages of number of hinges form.
Session 5 design of rcc structural elements PROF YADUNANDANAjit Sabnis
This document provides an overview of designing reinforced concrete (RCC) elements such as slabs, beams, columns, footings, staircases, and water tanks. It begins with defining design as sizing the structure to have a low probability of limit states like failure or excessive deformation being exceeded. Probability and real-world parameters like strain are considered rather than deterministic calculations. The general design process is outlined as preliminary sizing based on codes, defining loads and combinations, analyzing to get member forces, and designing reinforcement. Guidelines for preliminary slab, beam, and column sizing are provided based on span-to-depth ratios. Different slab types like one-way and two-way systems are also introduced.
DESIGN OF RCC ELEMENTS SESSION 5 PROF. YADUNANDANAjit Sabnis
This document provides an overview of the design of reinforced concrete (RCC) elements such as slabs, beams, columns, footings, staircases, and water tanks. It begins with introducing the concept of design in RCC, which has evolved from a deterministic to a probabilistic approach based on limit states. The general design procedure is then outlined, involving modeling the structure, specifying loads and load combinations, analyzing to obtain member forces, and designing individual elements. Guidelines for preliminary sizing of slab thickness, beam depth, and column dimensions are provided. Finally, the document discusses the different types of slabs and provides equations for calculating design moments in one-way and two-way slabs.
PERFORMANCE BASED ANALYSIS OF VERTICALLY IRREGULAR STRUCTURE UNDER VARIOUS SE...Ijripublishers Ijri
In the recent years a lot of attention has been given to the earthquake analysis of structure it is one of the most devastating
natural calamity and which causes severe damage not only to the properties but also to the lives. This is the
reason there has been a lot of focus on the structures to be earthquake resistant. Buildings get damaged mostly due
to the earthquake ground motions. In an earthquake, the building base experiences high frequency movements, which
results in the inertial force on the building and its components and this problem gets worse when a structure is irregular
in shape, size etc,. Therefore, there is a lot to work on the seismic behavior of the irregular building which might not
respond the way regular building does. It makes the irregular building quite more complex and unpredictable during
the course of an earthquake.
General & geotechnical considerations for pile designRizwan Khurram
This document provides an overview of key considerations for pile foundation design, including general design factors, subsurface investigations, pile types, load types, failure definitions, and construction and long-term performance monitoring. It emphasizes the importance of coordination between structural and geotechnical engineers, and of establishing an appropriate factor of safety based on the significance and function of the structure. Subsurface conditions like soil and groundwater properties must be well characterized to properly model load transfer mechanisms.
This document discusses the history and technical background of design drift requirements in building codes. It explains that code provisions for calculating seismic drift have changed substantially over the past 40 years, though the reasons for these changes are not well documented. The document focuses on minimum base shear requirements for determining drift in long-period structures, and discusses the reasoning behind current code equations. It also explores the effects of drift on structural elements, nonstructural components, and adjacent buildings.
PRESENTATION ON SEISMIC ANALYSIS AND DESIGN OF COLLEGE BUILDINGMohammedHashim81
This document presents the seismic analysis and retrofitting design of Bearys Pharmacy College Building conducted by civil engineering students from Bearys Institute of Technology under the guidance of their professor. The objectives are to analyze the existing building for earthquake loads using STAAD Pro, design columns, compare results with existing design, and suggest retrofitting methods. The document covers an introduction to earthquakes and seismic analysis of buildings, literature review on previous related studies, and outlines different retrofitting methods that could be used.
Performance based analysis of rc building consisting shear wall and varying i...Yousuf Dinar
Abstract:
Metropolitan cities are under severe threat because of inappropriate design and construction of structures. Faulty building designed without considering seismic consideration could be vulnerable to damage even under low levels of ground shaking from distant earthquake. So, structural engineers often are more concerned about the constructing Shear wall without knowing its performance with respect to infill percentage which may lead it to an over design state without knowing the demand. Nonlinear inelastic pushover analysis provides a better view about the behavior of the structures during seismic events. This study investigates as well as compares the performances of bare, different infill percentage level and two types of Shear wall consisting building structures and suggests from which level of performance shear wall should be preferred over the infill structure. To perform the finite element simulation ETABS 9.7.2 is used to get the output using pushover analysis. For different loading conditions, the performances of structures are evaluated with the help of base shear, deflection, storey drift, storey drift ratio and stages of number of hinges form and represented with discussion.
IRJET- Performance of Framed Building with Soft Storey at Different LevelsIRJET Journal
This document summarizes a study on the performance of framed buildings with soft storeys at different levels. A soft storey is defined as one with lower lateral stiffness than the floor above. Soft storeys are prone to damage during earthquakes as lateral forces concentrate in the soft storey. The study analyzes a G+20 building model with soft storeys placed at different heights using response spectrum analysis. Response spectrum analysis allows studying the effect of soft storey placement by providing the response to applied loads and ground motion conditions. The objectives are to analyze displacement, stiffness, inter-storey drift, and base shear for the different soft storey configurations and identify the arrangement with minimum damage.
Ground improvement technic and repair procedures.pdfKumarS250747
Foundation Design requires the knowledge of the behavior of the structure supported by the foundation as well as that of soil or rock that furnishes the ultimate support.
The super structure, foundation and soil or rock must act together and each must posses its unique serviceability and safety in the interactive system
The soil or rock may provide adequate safety of the foundation against failure, detrimental settlement may occur prior to any collapse. Which may be analogous to beam or truss in super structure but does not meet the serviceability(Deflection) criteria
The super structure designs are controlled by the strength of material such as shear strength ,compressive strength and tensile strength but deformations governs the design of foundation.
IRJET- Analytical Study of Punching Shear in Flat Slab - Review PaperIRJET Journal
This document provides a literature review on analytical studies of punching shear in flat slab structures. It discusses how flat slab construction is becoming more popular due to advantages like reduced building height and construction time. However, punching shear failure at column-slab connections is a major design challenge. The literature review summarizes several papers that analyzed different flat slab configurations under seismic loading, investigated strengthening methods for punching shear, and compared the seismic behavior of flat slab and conventionally reinforced structures. The conclusion is that providing drop panels at exterior column corners reduces the need for shear reinforcement, and including cut-outs near drops further improves the punching shear capacity of the slab.
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Basic designn criteria for highrise buildingsysuranga
Design criteria for high-rise buildings include:
1. Considering limit states design philosophy to ensure structures can withstand worst case loads during construction and usage.
2. Accounting for sequential loading during construction to avoid excessive stresses from differing rates of loading over the building's height.
3. Evaluating strength and stability to resist worst probable loads over the building's lifetime, including second-order effects, and ensuring the building does not topple.
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IRJET- Design of Earthquake Resistant Structure of Multi-Story RCC BuildingIRJET Journal
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Analysis and Capacity Based Earthquake Resistance Design of Multy Bay Multy S...IJERA Editor
This document summarizes the analysis and capacity based earthquake resistant design of a multi-bay, multi-story residential building. A nonlinear static pushover analysis was performed on the building model in ETABS2015 to estimate the structure's ultimate capacity and failure mechanisms. The analysis found plastic hinge formation and indicated damage levels at different load steps. Capacity curves and capacity spectrum curves were generated from the pushover analysis in both horizontal directions. Story displacements from the pushover analysis and response spectrum analysis are also reported. The results provide estimates of the building's strength, deformation capacities, and expected performance under seismic loads.
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This document summarizes the analysis and capacity based earthquake resistant design of a multi-storey reinforced concrete building. It begins with an introduction describing the need for earthquake resistant design of multi-storey buildings. It then describes the experimental program and methodology for capacity based design. This includes designing beams to act as ductile weak links and columns to remain elastic. The document then provides details of analyzing a G+6 building model in STAAD Pro, including load calculations and modeling the 3D reinforced concrete frame. It concludes with sections on capacity based design basics and analyzing the frame for gravity and seismic loads.
This document discusses revisions made to the Indian code of practice for steel structures (IS 800) between its 1984 and 2007 versions. Some key changes include shifting the design approach from working stress to limit states design, and incorporating provisions for structural analysis methods, earthquake design, fatigue, durability, and fire resistance. The Bureau of Indian Standards publishes and revises these codes of practice every 20-25 years in India, unlike international codes that are revised more frequently. The 2007 version of IS 800 reflects current knowledge and limits states design philosophy.
Comparison of Seismic Analysis of Multistorey Building Resting on Sloped Grou...IRJET Journal
This document presents a comparison of seismic analysis of multistory buildings resting on sloped ground with different slope angles and shear walls using ETABS software. It models and analyzes reinforced concrete structures with slopes of 0, 10, 20, and 30 degrees considering factors like story drift, displacements, and shear forces. The study aims to understand how slope influences building behavior. It loads the structures, performs response spectrum analysis, and compares parameters. Results show the 0 degree slope structure has minimum displacement, drift, and shear values, indicating it performs best under earthquake loads. This research helps evaluate building performance on sloped sites.
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Detailed-structural-assessment-report
1. DetailedDetailedDetailedDetailed StructuralStructuralStructuralStructural AssessmentAssessmentAssessmentAssessment
Southern Nevada Health District Main BuildingSouthern Nevada Health District Main BuildingSouthern Nevada Health District Main BuildingSouthern Nevada Health District Main Building
Las Vegas, NVLas Vegas, NVLas Vegas, NVLas Vegas, NV
Prepared for
PGAL, Inc.
Prepared by
Walter P. Moore and Associates, Inc.
3883 Howard Hughes Parkway, Suite 190
Las Vegas, NV 89169
S10.12004.00
April 16, 2012
2. i
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
TABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTSTABLE OF CONTENTS
EXECUTIVE SUMMARYEXECUTIVE SUMMARYEXECUTIVE SUMMARYEXECUTIVE SUMMARY........................................................................................................................................................................................................................................................................................................ 1111
INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION ................................................................................................................................................................................................................................................................................................................................................ 4444
Scope of Work.......................................................................... 4
BACKGROUNDBACKGROUNDBACKGROUNDBACKGROUND .................................................................................................................................................................................................................................................................................................................................................... 6666
SITE VISITSSITE VISITSSITE VISITSSITE VISITS ............................................................................................................................................................................................................................................................................................................................................................................ 9999
DISCUSSIONDISCUSSIONDISCUSSIONDISCUSSION............................................................................................................................................................................................................................................................................................................................................................ 11111111
LIMITATIONSLIMITATIONSLIMITATIONSLIMITATIONS............................................................................................................................................................................................................................................................................................................................................................ 19191919
APPENDIX AAPPENDIX AAPPENDIX AAPPENDIX A –––– FIGURES AND PHOTOGRAFIGURES AND PHOTOGRAFIGURES AND PHOTOGRAFIGURES AND PHOTOGRAPHSPHSPHSPHS ............................................................................................................................................AAAA1111
APPENDIX BAPPENDIX BAPPENDIX BAPPENDIX B........................................................................................................................................................................................................................................................................................................................................................ AAAA19191919
3. 1
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April 16, 2012 S10.12004.00
EXECUTIVE SUMMARYEXECUTIVE SUMMARYEXECUTIVE SUMMARYEXECUTIVE SUMMARY
Walter P Moore was engaged to perform a detailed structural engineering
assessment of the Southern Nevada Health District (SNHD) Public Health
Center (PHC) Main Building. This detailed assessment is supplemental to
our limited report titled “Visual Assessment of Southern Nevada Health
District Public Health Center” dated August 11, 2011. Our detailed
assessment identified serious deficiencies which we recommend be
addressed. In our visual assessment, we believed the PHC building had a
compromised lateral system due to observable deterioration of the building
elements. Upon further consideration as a result of our detailed
assessment, we have concluded the building does not have a complete
lateral system. The structural deterioration which has occurred is a direct
result of the lack of the building being able to transfer the lateral loads
appropriately and this deterioration of the structure will continue to
progress.
The building does not have an engineered diaphragm. A lateral diaphragm
is an essential element in providing support for structural elements subject
to wind or seismic elements and distributing those loads to the lateral force
resisting elements. A diaphragm is typically created by floor or roof decks,
floor slabs or engineered bracing. In the case of the PHC building, it has
relied on a gypsum panel system as its lateral diaphragm. This system was
apparently not engineered as, nor was it intended to be constructed as, a
suitable diaphragm. It was never adequate for and is increasingly failing in
that role for the structure.
The attachments of roof joists to the bearing and non@bearing masonry
walls are also inadequate. The current building code, as well as the original
1961 UBC under which the building was designed, requires concrete or
masonry walls to be anchored at all floors and roofs which provide lateral
support using connections capable of resisting a minimum force of 200
pounds per linear foot. Such anchorage is critical to the stability of these
walls.
As a result of these two deficiencies, the building does not have an
adequate lateral load resisting system. The PHC building exhibits
numerous signs of structural distress and in our view it appears to be
4. 2
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
unsafe and should not be occupied further until these inadequacies are
addressed.
These structural deficiencies could can be repaired. The repairs required
to correct these existing conditions are extensive and it may not be
financially feasible to implement. There is also strong evidence of sulfate
deterioration of the masonry walls and foundations. This has been
reported by the third party testing described in our August 2011 report and
in the retrofit design by R2H engineers in 2008. Any major new
reconstruction may also require replacement of these walls and
foundations.
To understand how the PHC building has been operating without a
diaphragm, we performed assessment calculations of the latent stability
and lateral capacity of the structure considering non@traditional and non@
engineered load paths. This analysis of what level of lateral resistance
could be provided by these elements found:
1. The masonry walls could only resist a wind load of
approximately 35 MPH to 50 MPH without support from a roof
diaphragm. This is considerably less than the code
requirement for Clark County of 90 MPH as specified in
American Society of Civil Engineers (ASCE) 7@10. The original
1961 Uniform Building Code (UBC) required the structure to
be designed for 15 PSF which equates to slightly more than
90 MPH.
2. The foundations were not designed to support the masonry
walls for the behavior listed in item 1, but they could be
providing a degree of latent strength that has helped the
building survive the loads subjected to the building during its
life. This latent strength could be provided through stressing
the soils beyond the original design capacities and through
assistance of resisting elements such as the slab on grade.
3. The building’s non@structural components such as interior
walls and ceilings may have also likely contributed to the
stiffness and stability of the structure, but these items are not
recognized to provide support for lateral forces by the building
5. 3
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
code. However, these secondary elements are only
unintentional load paths that have not been designed nor
detailed for resisting the building lateral loads and likely lack
the required capacity to provide reliable structural
performance. As these elements are not intended to act as
structural elements, their capacity to do so can deteriorate
over time and they cannot be relied upon.
4. The ongoing deterioration throughout the building makes it
clear that this building is not performing under its current
service loads. The ongoing deterioration is also likely further
compromising the structural strength and stability. We
conclude that it is unsafe and unwise to base future decisions
about the PHC building on the fact that it has survived for
nearly 50 years.
Finally, we recommend that the occupancy of the building should cease
until the structural deficiencies can be addressed. The City of Las Vegas
Department of Building and Safety should be advised and consulted in this
matter. If desired, we or another structural engineering firm can be
consulted to develop conceptual solutions to repair these deficiencies. It
may be, however, that these repairs are not economically viable.
6. 4
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION
Walter P Moore was retained to provide a detailed lateral assessment of
the Southern Nevada Health District (SNHD) Public Health Center (PHC)
main building located at 625 Shadow Lane in Las Vegas, Nevada. This
detailed assessment was supplemental to our earlier visual assessment
performed in the summer of 2011. Our previous observations and
recommendations are contained in the Walter P Moore report “Visual
Assessment of Southern Nevada Health District Public Health Center”
dated August 10, 2011.
Scope of WorkScope of WorkScope of WorkScope of Work
Walter P Moore’s scope of services was to provide detailed structural
assessment of the PHC main building to identify deficiencies with the
structure and better understand the deficiencies outlined in our report on
the visual assessment. Our scope of work was as follows:
1. Survey the existing diaphragm to identify the extent, location and
level of deterioration.
2. Perform a comparative analysis of the calculated existing
diaphragm performance against the original design and original
code requirements.
3. Define an updated risk assessment of the wind and seismic
resistance of the building diaphragm limited to the diaphragm
capacity only.
Walter P Moore fulfilled these scope items by performing the following:
1. We outlined limited destructive investigations to be performed by a
third party contractor. These investigations locations were
targeted to obtain information that was not provided on the original
construction documents provided to us by the owner.
2. We performed a thorough review of the provided construction
document. This detailed review was limited to the lateral structural
systems and load paths.
3. We performed a Tier 1 and Tier 2 evaluation of the PHC main
building was performed per the ASCE “Seismic Evaluation of
Existing Buildings” standard 31@03.
7. 5
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
4. We performed structural modeling and calculations of the lateral
load carrying elements to determine their as constructed load
carrying capacity.
5. We contacted the manufacturer of the 2” gypsum board roof
panels, USG, USG field personnel and other sources to obtain
load capacity information regarding the roof panels.
8. 6
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
BACKGROUNDBACKGROUNDBACKGROUNDBACKGROUND
The information below was obtained from visual observations, discussions
with SNHD personnel, partial construction documents, limited destructive
investigations and discussions with sources familiar with the gypsum roof
system. Some of this information is duplicated from our August 10, 2011
report.
The PHC main building is located at 625 Shadow Lane in Las Vegas,
Nevada. The building property, per the Clark County Seismic Maps, is
located in Seismic Site Class C. This results in a Seismic Design Category
of C per the ASCE Standard 7@05. The basic wind speed required per
ASCE 7@05 is 90 MPH and the Exposure Category is B.
The original PHC building was constructed in 1964 (Figure 1 and Photo 1).
It is mostly one story with a small mezzanine currently used as a
maintenance workshop. The total building area was approximately 46,000
SF at the time of construction. The structural system was concrete
masonry unit (CMU) walls and shear walls, which are noted to be solid
grouted “typical” on the partial set of plans provided to us. Roof members
consisted of steel joists at 4 feet on center supported directly on the CMU
walls. The roof deck consists of a “2” USG metal edge roof deck” (Photo 2
and Photo 3. USG was determined to refer to United States Gypsum
Corporation, a major manufacturer of gypsum board products which is still
in existence. Foundations were indicated as concrete spread foundations
although none of these were visible. The slab on grade is indicated to be
4” of reinforced concrete on a base course.
In 1973 the building was expanded to the west with the addition of
approximately 12,500 SF of new office space and a new vestibule at the
main entrance. This addition was constructed from precast concrete
panels for the exterior walls. The construction documents note the roof
framing to be steel decking on steel joists supported by wide flange
girders. However, visual observations clearly identify the roof system to be
TJL type wood joists with plywood roof sheathing supported on glulam
girders. It is unknown why the as@built condition does not match the
existing documents. It may be that the construction documents were
revised and the revised sheets no longer exist or it may be that the
Figure 1 @ Overall PHC Main Building
Roof Plan
.
Photo 2 – Joint between Roof Panels
Photo 3 – Gypsum Panel Roof
Photo 1 – PHC Main Building Aerial View
9. 7
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
construction documents were never revised. It is also not known which
systems were part of the final permit. The slab on grade is noted to be 4”
reinforced concrete. Neither the 1964 documents or the 1973 addition
were sealed by a registered engineer of record. The 1964 documents,
which bear a City of Las Vegas Building Department stamp, are not sealed.
The 1973 documents are sealed, but by a registrered architect. It is
assumed that this conformed to the state regulations for sealing of
documents at that time.
In 1991 two of the triangular courtyards were enclosed, one for an
administration area and one for a nurses area (Figure 1). The framing of the
roof enclosure was steel deck on steel joists supported on steel angle
ledgers. The supporting masonry walls were all original walls from the
1964 construction. The slab on grade construction is 4” reinforced
concrete. These drawings are also not sealed but are labeled “as@built”.
No reference was found to a structural engineer.
The final addition was constructed in 1997. The title of these
documents was “Clark County Health District Remodel”. No major
structural changes to the building foot print appeared to have been made
in this remodel. There was a major addition of an over@framed roof and
mechanical, electrical and plumbing upgrades (Photo 4). The extent of the
over@framed roof cover the “spokes” of the building. The over@framed roof
was constructed of standing seam steel deck over structural steel deck on
steel trusses. The steel trusses were directly supported on the existing
masonry walls. The documents for this addition did include separate
sheets for each consultant and the structural documents do list the name
of a designated structural engineer. There were no improvements to the
existing foundations or lateral system made to accommodate the over@
framed roof. Additionally, the over@framed roof was not detailed to allow it
to supplement the capacity of the original building’s lateral system,
including the roof diaphragm.
It is understood by us that a structural engineer was consulted within the
past four years to perform an assessment of the cracking observed on the
exterior masonry walls. That engineer, R2H, found the masonry
deterioration was likely due to sulfate deterioration at the base of the
Photo 4 – Underneath over@framed roof
Photo 5 – Concrete buttress wall
10. 8
SNHD Detailed Structural Assessment
April 16, 2012 S10.12004.00
masonry walls and recommended the addition of concrete buttress wall
along certain areas of the exterior of the building (Photo 5). Their
recommendations provided a short term and long term option. Only the
short term option was constructed. The short term option included only
partial installation of the concrete buttress walls along the worst of the
damaged walls. The constructed option was predicted to extend the life of
the damaged walls three years by the engineer. It is our understanding the
existing foundations were utilized where the buttress walls were added and
that the foundations were not widened.
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SITE VISITSSITE VISITSSITE VISITSSITE VISITS
Walter P Moore conducted site visits on March 20, March 22 and March
31, 2011. We were met on all dates by representatives of the SNHD who
provided access to both the public and non@public areas. Access was
provided to the exposed roof and the interior of the over@framed roof. On
March 22 and March 31 we were also met by representatives of a
construction company, which performed the destructive investigations.
Walter P Moore made several visits to the PHC site to investigate the
components of the assumed lateral system. On March 20 we performed a
general investigation of the roof panels and masonry wall attachments. The
roof connection to the masonry walls could only be observed from below
as the membrane roofing covered the joint from above. Our investigation
found no visible connection between the masonry non@bearing walls and
the roof system. In some areas, a steel bar through the seat of the steel
joist appeared to be connecting the steel joists to the bearing walls, but it
was determined closer examination would be necessary for the nature of
this connection. No other strap ties, screws, anchors, ledgers, etc could
be observed between the steel joist seat bearings, which are spaced at 4
foot on center, and the masonry walls. Voids were observed beneath
some joist seats where grout had pulled away from the seat bearings. No
other seat support was visible other than the portion supported on the
masonry face shells. It is assumed this condition has existing since the
original construction.
As a result of our observations on March 20, we recommended some
limited destructive investigation be performed to find out more regarding
the joist seat connection, masonry wall attachment and gypsum panel
attachment. A general contractor was engaged to perform the limited
destructive investigation and Walter P Moore provided a plan of the areas
to be investigated. As we only possessed incomplete construction
documents, and since access and obstructions could not be well
determined prior to the site work, a member of Walter P Moore’s staff was
on hand during the destructive investigation work to provide guidance.
The destructive investigation took place in the early morning hours of
March 22 and on the morning of March 31.
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Our field investigation and the destructive investigations have determined
the following:
1. No connection was provided between the top of the non@bearing
masonry exterior walls and the roof system. This was consistent
with the 1964 construction documents, which do not provide a
connection detail. The only mechanical connections observed at
all were anchor points between the joist bridging and the masonry.
These appear to be failing and are not intended to brace the
masonry walls.
2. The only connection between the roof framing and the masonry
bearing walls was via 1 foot long steel bars inserted through holes
drilled in the joist seats (Photo 6 and Photo 7). The pockets for the
joist seats were measured to be 8 inches wide, leaving
approximately 1.5 to 2 inches of bar embedment into the grouted
masonry on either side of the joist pocket. Additionally, no joist
bearing plate or attachment bolts were found.
3. We directed the contractor to remove a section of gypsum roof
panels. No screw or bolted attachment was observed between
the panels and the joists or from the panels to each other. This
finding made surveying and testing of the gypsum panels
unnecessary as transfer of lateral loads between these elements is
not possible. Our research, as described in the Discussion section
below, indicated that this was representative of the whole gypsum
panel system.
4. There is no connection between the top of the non@bearing
masonry interior walls and the other elements of the structure
sufficient to brace the top of the wall. These walls were observed
to be bracing other elements such as joist bridging and hallway
ceilings.
Photo 6 – Steel joist seat.
Photo 7 – Close up of the joist seat.
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DISCUSSIONDISCUSSIONDISCUSSIONDISCUSSION
The PHC main building is being used as a public health clinic. A thorough
discussion of our visual assessment and of notable features of the PHC
main building can be found in the Walter P Moore report dated August 10,
2011. This detailed structural assessment was limited to analysis of the
lateral system and the lateral load carrying members pursuant to our
previous recommendations. A discussion of our findings and conclusions
follows below.
We reviewed the partial original construction documents provided last
summer to Walter P Moore by the SNHD. We determined these drawings
are a partial set as the sheets are listed as XX of 50. Only 36 sheets of the
50 have apparently survived to date. However, some sheets have no title
block and may be duplicates or parts of other sets. Based on the sheets
which do have title blocks it appears that approximately half of the 50 sheet
set can be accounted for. The last 13 pages in particular are missing, but
these are often mechanical, electrical and plumbing drawings which have
no relevance to the current analysis.
Our review of the surviving drawings found no mechanical connection was
detailed between the masonry bearing walls and non@bearing walls and the
roof system. Our field investigations performed during March confirmed
that this was, in fact, the case (Photo 8). From below a clear gap could be
seen between the edge of the gypsum panels and the masonry walls. We
confirmed this in several areas by removing a section of the roofing
membrane to observe the condition from the topside as well (Photo 9). It
appears that the gap between the masonry walls and the gypsum panels is
recent as the joist bridging anchors also shows signs of having separated
from the wall (Photo 10).
We found the only roof system used on the original 1964 building was
comprised of gypsum metal edged gypsum wall planks. The existing
drawings do not show information regarding the attachment of the gypsum
planks to the steel joists, the attachment of the gypsum planks to each
other or of the lateral or gravity load carrying capacity of the gypsum
planks. A section of the roof panels was removed by the contractor during
the destructive investigation at our direction (Photo 11).
Photo 8 – Gap between the roof panels
and the masonry wall.
Photo 9 – Roof panels viewed from
above with membrane removed.
Photo 10 – Joist bridging anchor has
separated from the masonry wall.
Photo 11 – Metal edged USG gypsum
roof panel.
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The roof panels consist of poured gypsum enclosed by a light gauge steel
channel around the perimeter (Photo 12). The metal channel appeared to
be connected to the steel joists using small clips, but these were only
intermittent (Photo 13). These panels were easily removed as there was
not much holding them to the other panels or to the joists (Photo 15). The
mechanical attachment of the panels to the joists was minimal or absent
(Photo 14).
As we already documented in our August 10 report, many of the gypsum
panels were observed to be cracked or broken. The degree to which
these panels were broken varied from minor to major fractures (Photo 16
and Photo 17) to complete failure (Photo 18, Photo 19, Photo 20 and
Photo 21). Our survey found more than half of the accessible panels were
fractured. Some panels were not accessible due to solid gypboard ceilings
or other access restrictions. Our August 10 report identified these
fractures as a hazard to maintenance personnel needing to access the
numerous and heavy rooftop mechanical units (Photo 22), piping or
multiple other items located on the roof. Plywood has since been placed
over many of the most frequently accessed areas in order to provide a
degree of safety for the maintenance personnel.
We contacted USG last year to see if more technical information could be
found regarding the roof panels. At that time we were told by their
technical support that USG had never manufactured such a product. No
information could be found either on the USG website or in a limited search
of technical journals or of the various standard writing organizations. We
suspected no one with direct technical knowledge of the product was still
employed by USG if indeed they did manufacture the panels.
In view of our discoveries during the field investigations, we made another
effort with USG. Our findings were beginning to indicate this may be a
system without any diaphragm capacity at all, instead of only a reduced
capacity, due to the numerous field deficiencies found and loose
attachment to the joists. Once again a technical support representative
stated that USG had never manufactured a product similar to what was
described. However, they were able to refer us to a field representative,
who referred us to a second representative, Jennifer Link@Raschko. Once
Photo 15 – Roof level with a panel
section removed.
Photo 13 – Panel tabs located
intermittently connecting the roof panels
to the steel joists.
Photo 12 – A section of metal edged roof
panel with attachment clip.
Photo 14 – Panel tab connection seen
from below the joist top chord.
Photo 16 – Fractured gypsum roof panel.
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contacted, Ms Link@Raschko provided some information on a poured
gypsum system. When we discussed with the field representative that this
was not the system on the PHC, she stated it was the only gypsum system
USG manufactured. She did provide the contact of an architect, Bruce
Poteet, located in Charlotte, SC who she said may be able to provide more
assistance. We contacted Mr. Poteet and he was very familiar with the
gypsum plank system. He is retired from USG but has an arrangement
with USG to continue to answer technical questions for them.
Mr. Poteet said USG has not manufactured these panels for over thirty
years. However, they are still produced by another manufacturer, mainly
as replacement panels for systems such as the one on the PHC structure.
This outside manufacturer had bought the rights to the system from USG
many years ago. Mr. Poteet also stated that the panels were often only
placed on top of the supporting members or connected by small gauge
metal clips nailed attached to the panels via nails. He said these clips were
easily knocked off during construction and in many cases never installed.
Most importantly, Mr. Poteet, stated that the gypsum panels have no
diaphragm capacity and cannot be considered to be part of a lateral
system. They are also only minimally connected to the supporting
members and should not be considered to provide compression flange
bracing or other support. We requested Mr. Poteet provide a letter
regarding this information. His letter is attached in Appendix B below.
The discussion with Mr. Poteet confirmed many of the items we suspected
based on observations made during our March site visits and the results of
the destructive investigations. The panels were only minimally attached to
the steel joists at best and certainly not sufficiently to transfer diaphragm
loads or brace the joist top chord. The panel clips were often not regularly
installed and many times left out entirely. There was no connection
between the panels or to the exterior walls. In short the panels were laid
over the joists and held in place through friction or through confinement of
the perimeter walls.
In our August 2011 Visual Observation Report we were suspect of the
gypsum panel system due to the numerous fractures, age and apparent
poor performance of the system. We recommended at that time the
Photo 17 – Gypsum roof panels showing
major fractures.
Photo 18 – Failed roof panel.
Photo 19 – Failed roof panel.
Photo 20 – Failed roof panel.
Photo 21 – Failed roof panel.
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replacement of the diaphragm system due to these defects but we still
expected to find the panels were minimally connected together sufficient to
provide some level of diaphragm capacity and support for the walls. In our
opinion it is alarming that this building has no functioning diaphragm
system and it apparently has never had one.
A diaphragm is an essential part of the lateral system of most buildings. In
a typical one story shear wall structure such as this one, lateral loads acting
perpendicular to the structure are transferred to both the foundations and
the diaphragm by the exterior walls facing the lateral load (Diagram 1).
Diagram 1 – Elements of a lateral force resisting system
The diaphragm resists the lateral load and provides support to the exterior
wall by acting as a horizontal “deep beam”. The diaphragm then transfers
the lateral load to the resisting shear walls. Diaphragms can consist of
many materials including plywood, steel deck, concrete, concrete on steel
deck and cross bracing. The absence of a roof diaphragm means that the
exterior walls have no support at the top and must cantileverl from their
foundations. The lack of attachment between the walls and the roof are
particularly troubling at the PHC as the original design seems to assume
the presence of a roof diaphragm. With the lack of a diaphragm system a
substantial collapse of portions of the building could occur.
Photo 22 – Typical rooftop mechanical
unit.
Photo 25 – Wall fracture.
Photo 24 – Interior wall with no
attachment at the top of the wall.
Photo 23 – Interior wall without
attachment at the top of the wall.
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We observed other items which could contribute to such a collapse.
Interior walls were not supported at the top of wall (Photo 23 and Photo
24). This is a function normally performed by a roof diaphragm. Interior
walls often extend to the deck level or are braced to roof or floor levels.
We observed the interior walls at the PHC were serving as anchor points
for the roof joist bridging, a function they would not be able to perform well
without being braced themselves. The current building code, as well as the
original 1961 UBC under which the building was designed, requires a
positive mechanical attachment of masonry walls at floor and roof levels.
Additionally, as previously mentioned, the gypsum panel system does not
provide adequate bracing of the top flange of the joists. Joists ability to
carry gravity loads is dependent on the top flange being braced. Further
deterioration of the minimal bracing the gypsum panel system is providing
could lead to failure of joists under gravity loads.
As we noted in our August report, the exterior walls show evidence of
deterioration, particularly at the base. These cracks are particularly evident
at approximately 8” above the exterior sidewalk slab (Photo 25 to Photo
28), but fractures were observed throughout the exterior walls (Photo 29).
We observed the exterior walls to have separated at intersecting corners
(Photo 30 and Photo 31).
Based on our findings, we performed a structural analysis to determine the
capacity of the existing to carry wind loads. Our findings are as follows:
For exterior non@bearing, structural walls, based on the design information
in the original construction drawings, without being braced at the top of the
wall by an adequate connection to a diaphragm, we have calculated the
masonry wall to have a capacity of 4 PSF acting as a cantilever. Based on
ASCE 7, this would be equivalent to an approximately 50 MPH. This is
considerably less than the 90 MPH wind loads required by the current
building code or the 15 PSF required by the original building code (1961
UBC). The 2' wide strip foundations under these walls, however, are only
adequate for approximately 2 PSF wind pressure (35 MPH) against
overturning. The soil bearing pressures produced are over 3500 PSF which
approach the likely ultimate capacity of the soils, but likely exceed their
Photo 27 – Fracture at wall base.
Photo 26 – Fracture at wall base.
Photo 28 – Fracture at wall base.
Photo 29 – Fracture on the interior side of
an exterior wall.
Photo 30 – Cracked formed at
intersecting walls.
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allowable bearing capacity. Soils stressed to their ultimate capacity could
result in sudden, extreme failure.
For exterior load@bearing structural walls, without being braced at the top
by a connection to a roof diaphragm or even an adequate joist connection,
the capacity of the masonry wall is also approximately 4 PSF acting as a
cantilever. The strip foundations under these walls, however, are only
adequate for approximately 3 PSF wind pressure (45 MPH) against
overturning. The soil bearing pressures produced, however, are over 5000
PSF which likely exceeds the ultimate capacity of the soils.
The steel joists of the original 1964 building are attached to the supporting
masonry walls by means of a 12” bar which extends only a couple of
inches beyond the seat pocket. Some of these connections are spalled or
damaged and some joists had no positive attachment to the walls at all.
We observed the steel joists of the original 1964 building in several
locations to have grout pockets or inadequately grouted cells beneath the
joist bearing condition. These joists are supported only by the face shells
of the masonry bearing walls. These wall attachments are inadequate and
should be repaired. This is especially important due to the lack of a lateral
system.
Our calculations found the building foundations are not capable of carrying
more than minimal lateral load. The typical spread foundation for the
masonry walls is two foot wide and ten inches thick. Load bearing wall
foundations are loaded to full capacity with gravity loads alone. Several
additions have been constructed without any increase in foundation size.
We also have found evidence of sulfate deterioration in the masonry walls
and possibly in the foundations. This was also noted by the consultant
engineer, R2H, hired four years ago. Little was known about sulfate
deterioration of concrete, a common issue in the valley, when the building
was constructed.
Finally, we noted in our previous report corrosion was observed in the
expansion bolts and plates of the lateral anchorage for the over framed roof
constructed in 1997 (Photo 32 and Photo 33). Given the exposure of
these elements to the effects of weather, stainless steel should have been
Photo 33 – Corroded lateral attachment.
Photo 32 – Corroded lateral attachment.
Photo 31 – Cracked at joint of
intersecting walls.
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used. As we also noted, several of the bolts were observed to have failed.
Some of the worst of these conditions were repaired in December 2011.
That the structure has been able to stand fifty years in this condition is likely
due to several factors. The building is only one story and the story height is
not extremely high and the masonry walls are reinforced and fully grouted
giving them some limited cantilevered wall capacity as previously noted.
The building has an unusual shape in which intersecting exterior walls may
prevent others from overturning. The building has a large number of non@
structural interior walls, which in addition to the ceiling, provide some level
of bracing to the structural walls. However, having not been specifically
designed or detailed to function as structural elements, these elements are
not reliable as structural elements and are not permitted by code to be
considered in the structural capacity of the building. In addition, while it
does not appear that it was intended to do so, the over@framed may be
acting to nominally tie some of the walls together. Even considering these
factors, this does not represent a complete structural system and the
performance of such elements for lateral load resistance is not predictable.
Finally, and perhaps most importantly, these elements were not designed
to carry loads of the necessary magnitude and loading them in this manner,
the capacity of these secondary members will deteriorate over time,
reducing the real capacity of the structural elements to carry loads.
The masonry walls show deterioration at the base, exactly as would be
expected for walls performing as cantilevers. The opening of the joints
observed at intersecting corners is also consistent with this behavior as the
opening would be expected to be wider at the top than at the base.
However, the deterioration increases the likelihood of a critical failure and
our concern is that a small localized failure will quickly progress. We
recommend the building be provided with a functioning lateral system and
the masonry walls be provided with positive structural connection to the
lateral diaphragm. Until such time as these repairs are made we
recommend that occupancy of the facility cease. Without correction the
structure does not even meet the requirements of Tier 1 minimum
requirements per ASCE 31@03. ASCE 31@03 is the standard for reviewing
existing structures for seismic loads.
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The design of the three additions to the building did not address the issue
of the missing lateral system. We recommend discussions with the
building department in order to determine under what conditions the
building could or should be occupied. It is our opinion the building
department would not likely allow the building to be occupied in its current
state. Building repairs, including those to the lateral system will likely
require the entire building to be compliant with current code.
While the structural deficiencies observed can be repaired, the repairs will
be extensive and it may not be financially feasible to do so. In addition to
addition of an adequate structural diaphragm and repair of cracked
structural walls, there is also strong evidence of sulfate deterioration of the
masonry walls and foundations. This has been reported by the third party
testing described in our August 2011 report and in the retrofit design by
R2H engineers in 2008. Any major new reconstruction may require
replacement of these walls and foundations. These extensive repairs are
likely to impact other non@structural items such as roof waterproofing and
roof top mechanical equipment which could further increase repair costs.
The development of these repairs is beyond the scope of this report.
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LIMITATIONSLIMITATIONSLIMITATIONSLIMITATIONS
This report has been prepared at the request of PGAL, LLC to perform a
detailed structural assessment of the SNHD PHC.
Walter P Moore offers no warranty regarding the condition of concealed
construction or subsurface conditions beyond what was revealed in our
review. Any comments regarding concealed construction or subsurface
conditions are our professional opinion, based on engineering experience
and judgment, and derived in accordance with current standard of care
and professional practice.
Various other non@structural, cosmetic and structural damage unrelated to
this assessment may have been observed throughout the structure, some
of which are discussed in general in this report. However, a detailed
inventory of all cosmetic, nonstructural and structural damage was beyond
the scope of our assessment. Comments in this report are not intended to
be comprehensive but are representative of observed conditions. A peer
review or administrative review for code conformance was beyond the
scope of this report. Repair recommendations discussed herein are
conceptual and will require additional engineering design for
implementation.
We have made every effort to reasonably present the various areas of
concern identified during our site visits. If there are perceived omissions or
misstatements in this report regarding the observations made, we ask that
they be brought to our attention as soon as possible so that we have the
opportunity to fully address them in a timely manner.
This report has been prepared on behalf of and for the exclusive use of
PGAL, LLC and the Southern Nevada Health District. This report and the
discussion contained herein shall not, in whole or in part, be disseminated
or conveyed to any other party or used or relied upon by any other party, in
whole or in part, without prior written consent.
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APPENDIXAPPENDIXAPPENDIXAPPENDIX AAAA –––– FIGURES AND PHOTOGRAFIGURES AND PHOTOGRAFIGURES AND PHOTOGRAFIGURES AND PHOTOGRAPHSPHSPHSPHS
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Photo 8 – Gap between the roof panels and the masonry wall.
Photo 9 – Roof panels viewed from above with membrane removed.
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Photo 10 – Joist bridging anchor has separated from the masonry wall.
Photo 11 – Metal edged USG gypsum roof panel.
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Photo 12 – A section of metal edged roof panel with attachment clip.
Photo 13 – Panel tabs located intermittently connecting the roof panels to the steel joists.
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Photo 14 – Panel tab connection seen from below the joist top chord.
Photo 15 – Roof level with a panel section removed.
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Photo 22 – Typical rooftop mechanical unit.
Photo 23 – Interior wall with no attachment at the top of the wall.
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Photo 24 – Interior wall without attachment at the top of the wall.
Photo 25 – Wall fracture.
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Photo 28 – Fracture at wall base.
Photo 29 – Fracture on the interior side of an exterior wall.
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Photo 30 – Cracked formed at intersecting walls.
Photo 31 – Cracked at joint of intersecting walls.