H A I L E D B Y P R O F E S S I O N A L S A R O U N D T H E W O R L D as the definitive text on the subject, Cold-Formed Steel Design is an indispensable resource for all who design for and work with cold-formed steel. No other book provides such exhaustive coverage of both the theory and practice of cold-formed steel construction. Updated and expanded to reflect all the important developments that have occurred in the field over the past decade, this Fourth Edition of the classic text provides you with more of the detailed, up-to-the-minute technical information and expert guidance you need to make optimum use of this incredibly versatile material for building construction.

Wei-Wen Yu and Roger LaBoube, respected authorities in the field, draw upon decades of experience in cold-formed steel design, research, teaching, and development of design specifications to provide guidance on all practical aspects of cold-formed steel design for manufacturing, civil engineering, and building applications. Throughout the book, they describe the structural behavior of cold-formed steel members and connections from both the theoretical and experimental perspectives, and discuss the rationale behind the AISI and North American design provisions. Cold-Formed Steel Design, Fourth Edition features:

• Thoroughly up-to-date 2007 North American (AISI S100) design specifications • Both ASD and LRFD methods for USA and Mexico • LSD (Limit States Design) method for Canada • A new chapter on the Direct Strength Method • Updates and revisions of all 14 existing chapters • In-depth design examples and explanation of design provisions

Cold-Formed Steel Design, Fourth Edition is a necessary tool-of-the-trade for structural engineers, manufacturers, construction managers, and architects. It is also an excellent advanced text for college students and researchers in structural engineering, architectural engineering, construction engineering, and related disciplines.

the definitive text in the field, thoroughly updated and expanded

WEI-WEN YU, PHD, PE, is Curators’ Professor Emeritus of Civil Engineering at Missouri University of Science and Technology (formerly, University of Missouri–Rolla) and Founding Director of Wei-Wen Yu Center for Cold-Formed Steel Structures. He was awarded the 2001 Shortridge Hardesty Award from the ASCE and the 2009 Lynn Beedle Award from the Structural Stability Research Council.

ROGER A. LABOUBE, PHD, PE, is Curators’ Distinguished Teaching Professor of Civil Engineering at Missouri University of Science and Technology (formerly, University of Missouri–Rolla) and Director of Wei-Wen Yu Center for Cold-Formed Steel Structures. Dr. LaBoube is an active member of AISI Committee on Specification and Committee on Framing Standards, and has an extensive industry and academic background related to the design and behavior of cold-formed steel structures.

F O U R T H E D I T I O N

Cold-FormedSteel Design

Wei-Wen Yu and Roger A. LaBoube

Yu LaBoubeC

old-Formed S

teel Design

F O U R T H E D I T I O NCover design: Holly Wittenberg

Cover photographs: Steel Deck Institute, Fox River Grove, IL

Technology/Engineering/Civil

Cold-Formed Steel Design

Cold-Formed Steel Design

Fourth Edition

Wei-Wen YuRoger A. LaBoube

Missouri University of Science and Technology(Formerly University of Missouri-Rolla)

Rolla, Missouri

John Wiley & Sons, Inc.

This book is printed on acid-free paper.

Copyright © 2010 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New JerseyPublished simultaneously in Canada

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical,photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without eitherthe prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center,222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at www.copyright.com. Requests to the Publisher forpermission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011,fax (201) 748-6008, or online at www.wiley.com/go/permissions.

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Library of Congress Cataloging-in-Publication Data:Yu, Wei-wen, 1924-

Cold-formed steel design / Wei-Wen Yu, Roger A. LaBoube. – 4th ed.p. cm.

Includes bibliographical references and index.ISBN 978-0-470-46245-4 (cloth); ISBN 978-0-47074-3 (ebk); ISBN 978-0-47075-0 (ebk); ISBN 978-0-47076-7 (ebk)

1. Building, Iron and steel. 2. Sheet-steel. 3. Thin-walled structures. 4. Steel–Cold working. I. LaBoube, Roger A. II. Title.TA684.Y787 2010624.1′821–dc22

2010005153

Printed in the United States of America10 9 8 7 6 5 4 3 2 1

CONTENTS

Preface ix

CHAPTER 1 INTRODUCTION 1

1.1 General Remarks 11.2 Types of Cold-Formed Steel Sections and Their Applications 21.3 Standardized Metal Buildings and Industrialized Housing 81.4 Methods of Forming 121.5 Research and Design Specifications 171.6 General Design Considerations of Cold-Formed Steel Construction 201.7 Economic Design and Optimum Properties 26

CHAPTER 2 MATERIALS USED IN COLD-FORMED STEEL CONSTRUCTION 27

2.1 General Remarks 272.2 Yield Stress, Tensile Strength, and Stress–Strain Curve 332.3 Modulus of Elasticity, Tangent Modulus, and Shear Modulus 342.4 Ductility 342.5 Weldability 362.6 Fatigue Strength and Toughness 372.7 Influence of Cold Work on Mechanical Properties of Steel 372.8 Utilization of Cold Work of Forming 402.9 Effect of Temperature on Mechanical Properties of Steel 422.10 Testing of Full Sections and Flat Elements 432.11 Residual Stresses Due to Cold Forming 442.12 Effect of Strain Rate on Mechanical Properties 46

CHAPTER 3 STRENGTH OF THIN ELEMENTS AND DESIGN CRITERIA 47

3.1 General Remarks 473.2 Definitions of Terms 473.3 Design Basis 503.4 Serviceability 59

v

vi CONTENTS

3.5 Structural Behavior of Compression Elements and Design Criteria 593.6 Perforated Elements and Members 913.7 Plate Buckling of Structural Shapes 953.8 Additional Information 95

CHAPTER 4 FLEXURAL MEMBERS 97

4.1 General Remarks 974.2 Bending Strength and Deflection 974.3 Design of Beam Webs 1564.4 Bracing Requirements of Beams 1824.5 Torsional Analysis of Beams and Combined Bending and

Torsional Loading 1904.6 Additional Information on Beams 190

CHAPTER 5 COMPRESSION MEMBERS 191

5.1 General Remarks 1915.2 Yielding 1915.3 Flexural Column Buckling 1925.4 Torsional Buckling and Flexural–Torsional Buckling 1945.5 Effect of Local Buckling on Column Strength 2005.6 Distortional Buckling Strength of Compression Members 2015.7 Effect of Cold Work on Column Buckling 2025.8 North American Design Formulas for Concentrically Loaded

Compression Members 2035.9 Effective Length Factor K 2075.10 Built-Up Compression Members 2095.11 Bracing of Axially Loaded Compression Members 2095.12 Design Examples 2105.13 Compression Members Having One Flange Fastened to Decks or Panels 2185.14 Wall Studs 2205.15 Additional Information on Compression Members 221

CHAPTER 6 COMBINED AXIAL LOAD AND BENDING 223

6.1 General Remarks 2236.2 Combined Tensile Axial Load and Bending 2246.3 Combined Compressive Axial Load and Bending (Beam–Columns) 2256.4 North American Design Criteria 2326.5 Design Examples 2356.6 Second-Order Analysis 2486.7 Additional Information on Beam–Columns 249

CHAPTER 7 CLOSED CYLINDRICAL TUBULAR MEMBERS 251

7.1 General Remarks 2517.2 Types of Closed Cylindrical Tubes 2517.3 Flexural Column Buckling 2517.4 Local Buckling 2527.5 North American Design Criteria 2557.6 Design Examples 259

CONTENTS vii

CHAPTER 8 CONNECTIONS 263

8.1 General Remarks 2638.2 Types of Connectors 2638.3 Welded Connections 2638.4 Bolted Connections 2818.5 Screw Connections 2928.6 Other Fasteners 2968.7 Rupture Failure of Connections 2998.8 I- or Box-Shaped Compression Members Made by Connecting

Two C-Sections 2998.9 I-Beams Made by Connecting Two C-Sections 3018.10 Spacing of Connections in Compression Elements 304

CHAPTER 9 SHEAR DIAPHRAGMS AND ROOF STRUCTURES 307

9.1 General Remarks 3079.2 Steel Shear Diaphragms 3079.3 Structural Members Braced by Diaphragms 3199.4 Shell Roof Structures 3299.5 Metal Roof Systems 340

CHAPTER 10 CORRUGATED SHEETS 343

10.1 General Remarks 34310.2 Applications 34310.3 Sectional Properties and Design of Arc- and Tangent-Type

Corrugated Sheets 34310.4 Sectional Properties and Design of Trapezoidal-Type Corrugated Sheets 348

CHAPTER 11 COMPOSITE DESIGN 349

11.1 General Remarks 34911.2 Steel-Deck-Reinforced Composite Slabs 34911.3 Composite Beams or Girders with Cold-Formed Steel Deck 350

CHAPTER 12 INTRODUCTION TO STAINLESS STEEL DESIGN 353

12.1 General Remarks 35312.2 Differences between Specifications for Carbon Steels and Stainless Steels 355

CHAPTER 13 LIGHT-FRAME CONSTRUCTION 359

13.1 General Remarks 35913.2 Framing Standards 35913.3 Design Guides 367

CHAPTER 14 COMPUTER-AIDED DESIGN 369

14.1 General Remarks 36914.2 Computer Programs for Design of Cold-Formed Steel Structures 369

viii CONTENTS

CHAPTER 15 DIRECT-STRENGTH METHOD 371

15.1 General Remarks 37115.2 North American DSM Provisions 37115.3 Commentary on Appendix 1 (DSM) 37315.4 Direct-Strength Method Design Guide 37615.5 Design Examples 376

APPENDIX A THICKNESS OF BASE METAL 381

APPENDIX B TORSION 383

B.1 Introduction 383B.2 Shear Center 383B.3 Torsional Stresses 384B.4 Design Criteria for Combined Bending and Torsional Loading 393

APPENDIX C FORMULAS FOR COMPUTING CROSS-SECTIONAL PROPERTY βy 395

APPENDIX D DEFINITIONS OF TERMS 397

NOMENCLATURE 401

ACRONYMS AND ABBREVIATIONS 413

CONVERSION TABLE 415

REFERENCES 417

INDEX 483

PREFACE

This fourth edition of the book has been prepared to providereaders with a better understanding of the analysis anddesign of the thin-walled, cold-formed steel structures thathave been so widely used in building construction and otherareas in recent years. It is a revised version of the firstauthor’s book, Cold-Formed Steel Design, third edition,published by John Wiley & Sons, Inc. in 2000. All the revi-sions are based on the 2007 edition of the North AmericanSpecification with Supplement No.1, which combines theallowable strength design (ASD), the load and resistancefactor design (LRFD), and the limit states design (LSD)methods.

The material was originally developed for graduatecourses and short courses in the analysis and design ofcold-formed steel structures and is based on experiencein design, research, and development of the AmericanIron and Steel Institute (AISI) and North American designcriteria.

Throughout the book, descriptions of the structuralbehavior of cold-formed steel members and connectionsare given from both theoretical and experimental pointsof view. The reasons and justification for the variousdesign provisions of the North American specification arediscussed at length. Consequently the text not only will beinstructive for students but also can serve as a major sourceof reference for structural engineers and researchers.

Of the published book’s 15 chapters, Chapters 1–9and 13 have been completely revised according to thecombined ASD/LRFD/LSD North American specificationand framing standards. Other chapters have been updatedon the basis of available information. Chapter 15 is a newchapter on the direct-strength method.

Chapter 1 includes a general discussion of the applicationof cold-formed steel structures and a review of previous andrecent research. It also discusses the development of designspecifications and the major differences between the design

of cold-formed and hot-rolled steel structural members.Because of the many research projects in the field thathave been conducted worldwide during the past 35 years,numerous papers have been presented at various confer-ences and published in a number of conference proceedingsand engineering journals. At the same time, new designcriteria have been developed in various countries. Thesenew developments are reviewed in this chapter.

Since material properties play an important role in theperformance of structural members, the types of steels andtheir most important mechanical properties are describedin Chapter 2. In addition to the revision of Table 2.1, newinformation on the use of low-ductility steel for concen-trically loaded compression members has been included inSection 2.4. Section 2.6 includes additional information onfatigue strength.

In Chapter 3, the strength of thin elements and designcriteria are discussed to acquaint the reader with the funda-mentals of local buckling and postbuckling strength of thinplates and with the basic concepts used in design. Thischapter has been completely revised to include detailedinformation on design bases for ASD, LRFD, and LSDwith a revised Table 3.1, the unstiffened elements withstress gradient, the uniformly compressed elements withintermediate stiffeners, and noncircular holes.

Chapter 4 deals with the design of flexural members.Because the design provisions were revised extensivelyduring 2001–2007, this chapter has been completelyrewritten to cover the design of beams using ASD, LRFD,and LSD methods. It includes new and revised designinformation on inelastic reserve capacity of beams withunstiffened elements, distortional buckling strength, shearstrength of webs, web crippling strength and combinationwith bending, bearing stiffeners in C-section beams,bracing requirements, and beams having one flangefastened to a standing seam roof system.

ix

x PREFACE

The design procedures for compression members arediscussed in Chapter 5. This chapter has been brought upto date by including new design information on distortionalbuckling strength, built-up members, bracing requirements,and Z-section members having one flange fastened to astanding seam roof.

In 2007, the North American specification introduced thesecond-order analysis approach as an optional method forstability analysis. A new Section 6.6 has been added inChapter 6 to deal with this alternative method. In addi-tion, revisions have also been made on the design ofbeam–columns using ASD, LRFD, and LSD methods.

Chapter 7 covers the design of closed cylindrical tubes.This revised chapter reflects the rearrangement of designprovisions in the North American specification and minorchanges made in the 2007 edition of the specification.

Like the member design, the design of connections hasbeen updated in Chapter 8 using the ASD, LRFD, andLSD methods with additional and revised design provi-sions for bearing strength between bolts and connectedparts, combined shear and tension in bolts, block shearstrength, revised design information on screw connections,and power-actuated fasteners.

Because various types of structural systems, such asshear diaphragms and shell roof structures, have becomeincreasingly popular in building construction, Chapter 9contains design information on these types of structuralsystems. It includes the new standard for the cantilevertest method for shear diaphragms and the revised designprocedure for wall studs. A new Section 9.5 has been addedfor metal roof systems.

The sectional properties of standard corrugated sheetsare discussed in Chapter 10 because they have long beenused in buildings for roofing, siding, and other applications.Minor revisions have been made in Section 10.4.

Steel decks are widely used in building construction.Consequently the updated information in Chapter 11 ontheir use in steel-deck-reinforced composite slabs andcomposite beams is timely.

Chapter 12 contains an introduction to the design of cold-formed stainless steel structural members supplementing theinformation on cold-formed carbon steel structural membersin other chapters. This chapter has been updated on the basisof the revised Structural Engineering Institute/AmericanSociety of Civil Engineers (SEI/ASCE) Standard 8-02 andrecent research findings for the design of cold-formedstainless steel structural members.

During recent years, cold-formed steel members havebeen used increasingly for residential and commercialconstruction. The previous Chapter 14 has been completelyrewritten based on new and revised framing standards. This

chapter has been changed to Chapter 13 using the new titleof Light-Frame Construction.

The increasing use of computers for design workwarrants the brief introduction that is given in the revisedChapter 14 for the computer-aided design of cold-formedsteel structures.

In 2004, a new Appendix 1 was added in the North Amer-ican specification for the use of the direct-strength methodto determine the nominal axial strength for columns andflexural strength for beams. These alternative design proce-dures are discussed in the new Chapter 15. Also discussedin this chapter are the Commentary on Appendix 1,the Direct Strength Method Design Guide, and designexamples.

It is obvious that a book of this nature would not havebeen possible without the cooperation and assistance ofmany individuals, organizations, and institutions. It is basedprimarily on the results of continuing research programs oncold-formed steel structures that have been sponsored bythe American Iron and Steel Institute (AISI), the ASCE,the Canadian Sheet Steel Building Institute (CSSBI), theCold-Formed Steel Engineers Institute (CFSEI) of the SteelFraming Alliance (SFA), the Metal Building ManufacturersAssociation (MBMA), the Metal Construction Association(MCA), the National Science Foundation (NSF), the RackManufacturers Institute (RMI), the Steel Deck Institute(SDI), the Steel Stud Manufacturers Association (SSMA),and other organizations located in the United States andabroad. The publications related to cold-formed steel struc-tures issued by AISI and other institutions have been veryhelpful for the preparation of this book.

The first author is especially indebted to his teacher,the late Professor George Winter of Cornell University,who made contributions of pronounced significance to thebuilding profession in his outstanding research on cold-formed steel structures and in the development of AISIdesign criteria. A considerable amount of material used inthis book is based on Dr. Winter’s publications.

Our sincere thanks go to Mr. Robert J. Wills, VicePresident, Construction Market Development, Steel MarketDevelopment Institute (a business unit of the American Ironand Steel Institute), for permission to quote freely fromthe North American Specification, Commentary, DesignManual, Framing Standards, Design Guides, and other AISIpublications. An expression of appreciation is also due tothe many organizations and individuals that granted permis-sion for the reproduction of quotations, graphs, tables, andphotographs. Credits for the use of such materials are givenin the text.

We wish to express our sincere thanks to Mr. Don Allen,Mr. Roger L. Brockenbrough, Dr. Helen Chen, Mr. Jay W.Larson, Professor Teoman B. Pekoz, Professor Benjamin

PREFACE xi

W. Schafer, Professor Reinhold M. Schuster and ProfessorCheng Yu for their individual reviews of various parts ofthe manuscript. Their suggestions and encouragement havebeen of great value to the improvement of this book.

We are very grateful to Mrs. Christina Stratman for herkind assistance in the preparation of this book. Thanks arealso due to Miss Domenica Cambio and Miss MingyanDeng for their careful typing and preparation of draw-ings. The financial assistance provided by the MissouriUniversity of Science and Technology through the firstauthor’s Curators’ Professorship and the sponsors for the

Wei-Wen Yu Center for Cold-Formed Steel Structures isappreciated.

This book could not have been completed without thehelp and encouragement of the authors’ wives, Yuh-HsinYu and Karen LaBoube, as well as for their patience,understanding, and assistance.

Wei-Wen YuRoger A. LaBoube

Rolla, MissouriMarch 2010

Cold-Formed Steel Design

CHAPTER 1

Introduction

1.1 GENERAL REMARKS

In steel construction, there are two main families ofstructural members. One is the familiar group of hot-rolledshapes and members built up of plates. The other, lessfamiliar but of growing importance, is composed of sectionscold formed from steel sheet, strip, plate, or flat bar inroll-forming machines or by press brake or bending brakeoperations.1.1,1.2,1.3∗ These are cold-formed steel structuralmembers. The thickness of steel sheet or strip generallyused in cold-formed steel structural members ranges from0.0149 in. (0.378 mm) to about 1

4 in. (6.35 mm). Steel platesand bars as thick as 1 in. (25.4 mm) can be cold formedsuccessfully into structural shapes.1.1,1.4,1.314,1.336,1.345

Although cold-formed steel sections are used in carbodies, railway coaches, various types of equipment,storage racks, grain bins, highway products, transmissiontowers, transmission poles, drainage facilities, and bridgeconstruction, the discussions included herein are primarilylimited to applications in building construction. For struc-tures other than buildings, allowances for dynamic effects,fatigue, and corrosion may be necessary.1.314,1.336,1.345

The use of cold-formed steel members in buildingconstruction began in about the 1850s in both the UnitedStates and Great Britain. However, such steel memberswere not widely used in buildings until around 1940. Theearly development of steel buildings has been reviewed byWinter.1.5–1.7

Since 1946 the use and the development of thin-walledcold-formed steel construction in the United States havebeen accelerated by the issuance of various editions of the“Specification for the Design of Cold-Formed Steel Struc-tural Members” of the American Iron and Steel Institute

∗The references are listed at the back of the book.

(AISI).1.267,1.345 The earlier editions of the specificationwere based largely on the research sponsored by AISI atCornell University under the direction of George Wintersince 1939. It has been revised subsequently to reflectthe technical developments and the results of continuingresearch.1.267,1.336,1.346

In general, cold-formed steel structural members providethe following advantages in building construction:

1. As compared with thicker hot-rolled shapes, cold-formed light members can be manufactured for rela-tively light loads and/or short spans.

2. Unusual sectional configurations can be producedeconomically by cold-forming operations (Fig. 1.1),and consequently favorable strength-to-weight ratioscan be obtained.

3. Nestable sections can be produced, allowing forcompact packaging and shipping.

4. Load-carrying panels and decks can provide usefulsurfaces for floor, roof, and wall construction, and inother cases they can also provide enclosed cells forelectrical and other conduits.

5. Load-carrying panels and decks not only withstandloads normal to their surfaces, but they can also actas shear diaphragms to resist force in their own planesif they are adequately interconnected to each other andto supporting members.

Figure 1.1 Various shapes of cold-formed sections.1.1

1

2 1 INTRODUCTION

Compared with other materials such as timber andconcrete, the following qualities can be realized for cold-formed steel structural members1.8,1.9:

1. Lightness2. High strength and stiffness3. Ease of prefabrication and mass production4. Fast and easy erection and installation5. Substantial elimination of delays due to weather6. More accurate detailing7. Nonshrinking and noncreeping at ambient tempera-

tures8. Formwork unneeded9. Termite proof and rot proof

10. Uniform quality11. Economy in transportation and handling12. Noncombustibility13. Recyclable material

The combination of the above-mentioned advantages canresult in cost saving in construction.

1.2 TYPES OF COLD-FORMED STEELSECTIONS AND THEIR APPLICATIONS

Cold-formed steel structural members can be classified intotwo major types:

1. Individual structural framing members2. Panels and decks

The design and the usage of each type of structuralmembers have been reviewed and discussed in a numberof publications.1.5–1.75,1.267–1.285,1.349,1.358

1.2.1 Individual Structural Framing Members

Figure 1.2 shows some of the cold-formed sectionsgenerally used in structural framing. The usual shapesare channels (C-sections), Z-sections, angles, hatsections, I-sections, T-sections, and tubular members.Previous studies have indicated that the sigma section(Fig. 1.2d ) possesses several advantages such as highload-carrying capacity, smaller blank size, less weight,

Figure 1.2 Cold-formed sections used in structural framing.1.6

Figure 1.3 Building composed entirely of cold-formed steel sections. (Courtesy of Penn MetalCompany.)1.7

TYPES OF COLD-FORMED STEEL SECTIONS AND THEIR APPLICATIONS 3

and larger torsional rigidity as compared with standardchannels.1.76

In general, the depth of cold-formed individual framingmembers ranges from 2 to 12 in. (50.8 to 305 mm), andthe thickness of material ranges from 0.048 to about 1

4 in.(1.22 to about 6.35 mm). In some cases, the depth ofindividual members may be up to 18 in. (457 mm), and thethickness of the member may be 1

2 in. (12.7 mm) or thickerin transportation and building construction. Cold-formedsteel plate sections in thicknesses of up to about 3

4 or 1 in.(19.1 or 25.4 mm) have been used in steel plate structures,transmission poles, and highway sign support structures.

In view of the fact that the major function of this typeof individual framing member is to carry load, structuralstrength and stiffness are the main considerations in design.

Such sections can be used as primary framing membersin buildings up to six stories in height.1.278 In 2000,the 165-unit Holiday Inn in Federal Way, Washington,utilized eight stories of axial load bearing cold-formed steelstuds as the primary load-bearing system.1.357 Figure 1.3shows a two-story building. In tall multistory buildingsthe main framing is typically of heavy hot-rolled shapesand the secondary elements may be of cold-formed steelmembers such as steel joists, studs, decks, or panels(Figs. 1.4 and 1.5). In this case the heavy hot-rolled steelshapes and the cold-formed steel sections supplement eachother.1.264

As shown in Figs. 1.2 and 1.6–1.10, cold-formed sectionsare also used as chord and web members of open web steeljoists, space frames, arches, and storage racks.

Figure 1.4 Composite truss–panel system prefabricated by Laclede Steel Company.

Figure 1.5 Cold-formed steel joists used together with hot-rolled shapes. (Courtesy of Stran-SteelCorporation.)

4 1 INTRODUCTION

Figure 1.6 Cold-formed steel sections used in space frames. (Courtesy of Unistrut Corporation.)

Figure 1.7 Cold-formed steel members used in space grid system. (Courtesy of Butler Manufac-turing Company.)

TYPES OF COLD-FORMED STEEL SECTIONS AND THEIR APPLICATIONS 5

Figure 1.8 Cold-formed steel members used in a 100 × 220 × 30-ft (30.5 × 67.1 × 9.2-m)triodetic arch. (Courtesy of Butler Manufacturing Company.)

( )

( )

b

a

Figure 1.9 Hangar-type arch structures using cold-formed steelsections. (Courtesy of Armco Steel Corporation.)1.6

1.2.2 Panels and Decks

Another category of cold-formed sections is shown inFig. 1.11. These sections are generally used for roof decks,

floor decks, wall panels, siding material, and bridge forms.Some deeper panels and decks are cold formed with webstiffeners.

The depth of panels generally ranges from 1 12 to 7 1

2 in.(38.1 to 191 mm), and the thickness of materials rangesfrom 0.018 to 0.075 in. (0.457 to 1.91 mm). This is not tosuggest that in some cases the use of 0.012-in. (0.305-mm)steel ribbed sections as load-carrying elements in roof andwall construction would be inappropriate.

Steel panels and decks not only provide structuralstrength to carry loads, but they also provide a surface onwhich flooring, roofing, or concrete fill can be applied, asshown in Fig. 1.12. They can also provide space for elec-trical conduits, or they can be perforated and combined withsound absorption material to form an acoustically condi-tioned ceiling. The cells of cellular panels are also used asducts for heating and air conditioning.

In the past, steel roof decks were successfullyused in folded-plate and hyperbolic paraboloid roofconstruction,1.13,1.22,1.26,1.30,1.34,1.35,1.72,1.77–1.84 as shownin Figs. 1.13 and 1.14. The world’s largest cold-formedsteel primary structure using steel decking for hyperbolicparaboloids, designed by Lev Zetlin Associates, is shownin Fig. 1.15.1.82 In many cases, roof decks are curved tofit the shape of an arched roof without difficulty. Someroof decks are shipped to the field in straight sectionsand curved to the radius of an arched roof at the jobsite (Fig. 1.16). In other buildings, roof decks have beendesigned as the top chord of prefabricated open web steeljoists or roof trusses (Fig. 1.17).1.85,1.86 In Europe, TRP200 decking (206 mm deep by 750 mm pitch) has beenused widely. In the United States, the standing seam metalroof has an established track record in new constructionand replacement for built-up and single-ply systems inmany low-rise buildings.

6 1 INTRODUCTION

Figure 1.10 Rack structures. (Courtesy of Unarco Materials Storage.)

Figure 1.11 Decks, panels, and corrugated sheets.

Figure 1.11 also shows corrugated sheets which are oftenused as roof or wall panels and in drainage structures. Theuse of corrugated sheets as exterior curtain wall panelsis illustrated in Fig. 1.18a . It has been demonstrated thatcorrugated sheets can be used effectively in the arched roofsof underground shelters and drainage structures.1.87–1.89

The pitch of corrugations usually ranges from 1 14 to 3 in.

(31.8 to 76.2 mm), and the corrugation depth varies from

14 to 1 in. (6.35 to 25.4 mm). The thickness of corrugatedsteel sheets usually ranges from 0.0135 to 0.164 in. (0.343to 4.17 mm). However, corrugations with a pitch of up to6 in. (152 mm) and a depth of up to 2 in. (50.8 mm) arealso available. See Chapter 10 for the design of corrugatedsteel sheets based on the AISI publications.1.87,1.88 Unusu-ally deep corrugated panels have been used in framelessstressed-skin construction, as shown in Fig. 1.18b. The

TYPES OF COLD-FORMED STEEL SECTIONS AND THEIR APPLICATIONS 7

Figure 1.12 Cellular floor panels. (Courtesy of H. H. Robertson Company.)

Figure 1.13 Cold-formed steel panels used in folded-plate roof. (Courtesy of H. H. RobertsonCompany.)

Figure 1.14 Hyperbolic paraboloid roof of welded laminated steel deck. (Reprinted fromArchitectural Record, March 1962. Copyright by McGraw-Hill Book Co., Inc.)1.79

8 1 INTRODUCTION

Figure 1.15 Superbay hangar for American Airlines Boeing 747s in Los Angeles. (Courtesy ofLev Zetlin Associates, Inc.)1.82

Figure 1.16 Arched roof curved at job site. (Courtesy of DonnProducts Company.)

self-framing corrugated steel panel building proved to bean effective blast-resistant structure in the Nevada testsconducted in 1955.1.90

Figure 1.19 shows the application of standing seam roofsystems. The design of beams having one flange fastenedto a standing seam roof system and the strength of standingseam roof panel systems are discussed in Chapter 4.

In the past four decades, cold-formed steel deck hasbeen successfully used not only as formwork but alsoas reinforcement of composite concrete floor and roofslabs.1.55,1.91–1.103 The floor systems of this type ofcomposite steel deck-reinforced concrete slab are discussedin Chapter 11.

1.3 STANDARDIZED METAL BUILDINGSAND INDUSTRIALIZED HOUSING

Standardized single-story metal buildings have been widelyused in industrial, commercial, and agricultural applica-tions. Metal building systems have also been used forcommunity facilities such as recreation buildings, schools,and churches1.104,1.105 because standardized metal buildingprovides the following major advantages:

1. Attractive appearance2. Fast construction3. Low maintenance4. Easy extension5. Lower long-term cost

STANDARDIZED METAL BUILDINGS AND INDUSTRIALIZED HOUSING 9

Figure 1.17 Steel deck is designed as the top chord of prefabricated open web steel joists.(Courtesy of Inland-Ryerson Construction Products Company.)

In general, small buildings can be made entirely of cold-formed sections (Fig. 1.20), and relatively large buildingsare often made of welded steel plate rigid frames with cold-formed sections used for girts, purlins, roofs, and walls(Fig. 1.21).

The design of preengineered standardized metal build-ings is often based on the Metal Building Systems Manualissued by the Metal Building Manufacturers Association(MBMA).1.360 The 2006 edition of the MBMA manual isa revised version of the 2002 manual. The new manualincludes (a) load application data [International BuildingCode (IBC) 2006 loads], (b) crane loads, (c) serviceability,(d) common industry practices, (e) guide specifications,(f) AISC-MB certification, (g) wind load commentary,(h) fire protection, (i) wind, snow, and rain data byU.S. county, (j) a glossary, (k) an appendix, and (l) abibliography. In addition, MBMA also published the MetalRoof Systems Design Manual .1.361 It includes systemscomponents, substrates, specifications and standards,retrofit, common industry practices, design, installation,energy, and fire protection.

The design of single-story rigid frames is treated exten-sively by Lee et al.1.107 In Canada the design, fabrica-tion, and erection of steel building systems are based ona standard of the Canadian Sheet Steel Building Institute(CSSBI).1.108

Industrialized housing can be subdivided conve-niently into (1) panelized systems and (2) modularsystems.1.109,1.278 In panelized systems, flat wall, floor,

and roof sections are prefabricated in a production system,transported to the site, and assembled in place. In modularsystems, three-dimensional housing unit segments arefactory built, transported to the site, lifted into place, andfastened together.

In the 1960s, under the School Construction SystemsDevelopment Project of California, four modular systems ofschool construction were developed by Inland Steel Prod-ucts Company (modular system as shown in Fig. 1.17),Macomber Incorporated (V-Lok modular componentsystem as shown in Fig. 1.22), and Rheem/Dudley Build-ings (flexible space system).1.110 These systems have beenproven to be efficient structures at reduced cost. They aresuccessful not only for schools but also for industrial andcommercial buildings throughout the United States.

In 1970 Republic Steel Corporation was selected by theDepartment of Housing and Urban Development under theOperation Breakthrough Program to develop a modularsystem for housing.1.111 Panels consisting of steel facingswith an insulated core were used in this system.

Building innovation also includes the construction ofunitized boxes. These boxes are planned to be prefabricatedof room size, fully furnished, and stacked in some mannerto be a hotel, hospital, apartment, or office building. 1.25,1.112

For multistory buildings these boxes can be supported by amain framing made of heavy steel shapes.

In the past, cold-formed steel structural componentshave been used increasingly in low-rise buildingsand residential steel framing. Considerable research

10 1 INTRODUCTION

Figure 1.18 (a) Exterior curtain wall panels employing corrugated steel sheets.1.87 (b) Framelessstressed-skin construction. (Courtesy of Behlen Manufacturing Company.)

Figure 1.19 Application of standing seam roof systems.(Courtesy of Butler Manufacturing Company.)

and development activities have been conductedcontinuously by numerous organizations and steelcompanies.1.21,1.25,1.27,1.28,1.113–116,1.280–1.301 In addition tothe study of the load-carrying capacity of various structuralcomponents, recent research work has concentrated on(1) joining methods, (2) thermal and acoustical perfor-mance of wall panels and floor and roof systems, (3)vibrational response of steel decks and floor joists, (4)foundation wall panels, (5) trusses, and (6) energy consid-erations. Chapter 13 provides some information on recentdevelopments, design standards, and design guide forcold-formed steel light-frame construction.

In Europe and other countries many design conceptsand building systems have been developed. For details,

STANDARDIZED METAL BUILDINGS AND INDUSTRIALIZED HOUSING 11

Figure 1.20 Small building made entirely of cold-formed sections. (Courtesy of Stran-SteelCorporation.)1.6

Figure 1.21 Standardized building made of fabricated rigid frame with cold-formed sections forgirts, purlins, roofs, and walls. (Courtesy of Armco Steel Corporation.)

12 1 INTRODUCTION

Figure 1.22 V-Lok modular component system. (Courtesy of Macomber Incorporated.)

see Refs. 1.25, 1.40–1.43, 1.117, 118, 1.268, 1.270, 1.271,1.273, 1.275, 1.290, 1.293, and 1.297.

1.4 METHODS OF FORMING

Three methods are generally used in the manufacture ofcold-formed sections such as illustrated in Fig. 1.1:

1. Cold roll forming2. Press brake operation3. Bending brake operation

1.4.1 Cold Roll Forming1.1,1.119

The method of cold roll forming has been widely used forthe production of building components such as individualstructural members, as shown in Fig. 1.2, and some roof,floor, and wall panels and corrugated sheets, as shown inFig. 1.11. It is also employed in the fabrication of partitions,frames of windows and doors, gutters, downspouts, pipes,agricultural equipment, trucks, trailers, containers, railwaypassenger and freight cars, household appliances, and otherproducts. Sections made from strips up to 36 in. (915 mm)

wide and from coils more than 3000 ft (915 m) long can beproduced most economically by cold roll forming.

The machine used in cold roll forming consists of pairsof rolls (Fig. 1.23) which progressively form strips into thefinal required shape. A simple section may be produced byas few as six pairs of rolls. However, a complex sectionmay require as many as 15 sets of rolls. Roll setup timemay be several days.

The speed of the rolling process ranges from 20 to300 ft/min (6 to 92 m/min). The usual speed is in therange of 75–150 ft/min (23–46 m/min). At the finish end,the completed section is usually cut to required lengthsby an automatic cutoff tool without stopping the machine.Maximum cut lengths are usually between 20 and 40 ft(6 and 12 m).

As far as the limitations for thickness of material areconcerned, carbon steel plate as thick as 3

4 in. (19 mm) canbe roll formed successfully, and stainless steels have beenroll formed in thicknesses of 0.006–0.30 in. (0.2–7.6 mm).The size ranges of structural shapes that can be roll formedon standard mill-type cold-roll-forming machines are shownin Fig. 1.24.

The tolerances in roll forming are usually affected by thesection size, the product type, and the material thickness.

METHODS OF FORMING 13

Figure 1.23 Cold-roll-forming machine.

14 1 INTRODUCTION

Figure 1.24 Size ranges of typical roll-formed structural shapes.1.1

The following limits are given by Kirkland1.1 as represen-tative of commercial practice, but they are not necessarilyuniversal:

Piece length, usingautomatic cutoff ± 1

64 – 18 in. (0.4–3.2 mm)

Straightness and twist 164 – 1

4 in. (0.4–6.4 mm) in10 ft (3 m)

Cross-sectional dimensionsFractional ± 1

64 – 116 in. (0.4–1.6 mm)

Decimal ±0.005–0.015 in.(0.1–0.4 mm)

Angles ±1◦–2◦

Table 1.1 gives the fabrication tolerances as specified bythe MBMA for cold-formed steel channels and Z-sectionsto be used in metal building systems.1.360 All symbols usedin the table are defined in Fig. 1.25. The same tolerances arespecified in the standard of the CSSBI.1.108 For light steelframing members, the AISI framing standard S200-07 ongeneral provisions1.400 includes manufacturing tolerancesfor structural members. These tolerances for studs andtracks are based on the American Society for Testing andMaterials (ASTM) standard C955-03. See Table 1.2 andFig. 1.26. For additional information on roll forming, seeRef. 1.119.

Table 1.1 MBMA Table on FabricationTolerances1.341

Tolerances, in.

Dimension + −Geometry

D 316

316

B 316

316

D 38

18

θ1 3◦ 3◦

θ2 5◦ 5◦

Hole location

E 118

18

E 218

18

E 318

18

S 1116

116

S 2116

116

F 18

18

P 18

18

L 18

18

Chamber, C 14

(L ft10

), in.

Minimum thickness t 0.95 × design t

Note: 1 in. = 25.4 mm.