Aluminum structures

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  1. 1. ALUMINUM STRUCTURES A Guide to Their Specications and Design Second Edition J. Randolph Kissell Robert L. Ferry The TGB Partnership JOHN WILEY & SONS, INC.
  2. 2. This book is printed on acid-free paper. Copyright 2002 by John Wiley & Sons, Inc., New York. All rights reserved. Published 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 Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per- copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4744. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 605 Third Avenue, New York, NY 10158-0012, (212) 850-6011, fax (212) 850-6008, E-Mail: PERMREQ@WILEY.COM. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold with the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional person should be sought. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging-in-Publication Data: ISBN: 0-471-01965-8 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1
  3. 3. iii CONTENTS Preface to the First Edition ix Preface to the Second Edition xi PART I INTRODUCTION 1 1 Whats in This Book? 3 2 What Is Aluminum? 5 2.1 Metal in Construction 5 2.2 Many Metals from Which to Choose 7 2.3 When to Choose Aluminum 8 2.3.1 Introduction 8 2.3.2 Factors to Consider 11 2.4 Aluminum Alloys and Tempers 13 2.4.1 Introduction 13 2.4.2 Wrought Alloys 13 2.4.3 Tempers 17 2.5 Structural Applications of Aluminum 23 2.5.1 Background 23 2.5.2 Building and Construction Applications 24 3 Working with Aluminum 31 3.1 Product Forms 31 3.1.1 Extrusions 31 3.1.2 Sheet and Plate 56 3.1.3 Forgings 67 3.1.4 Castings 69 3.1.5 Prefabricated Products 74
  4. 4. iv CONTENTS 3.2 Coatings and Finishes 86 3.2.1 Mill Finish 87 3.2.2 Anodized Finishes 87 3.2.3 Painted Finishes 91 3.2.4 Mechanical Finishes 93 3.2.5 Cladding 93 3.2.6 Roong and Siding Finishes 94 3.3 Erection 94 PART II STRUCTURAL BEHAVIOR OF ALUMINUM 97 4 Material Properties for Design 99 4.1 Minimum and Typical Properties 99 4.2 Strengths 100 4.3 Modulus of Elasticity (E), Shear Modulus (G), and Poissons Ratio () 101 4.4 Fracture Properties 103 4.5 The Effect of Welding on Mechanical Properties 105 4.6 The Effect of Temperature on Aluminum Properties 106 4.7 Fire Resistance 108 4.8 Hardness 109 4.9 Physical Properties 109 4.10 Aluminum Material Specications 110 4.11 Alloy Identication 113 4.12 Certication Documentation 113 5 Explanation of the Aluminum Specication 115 5.1 Tension Members 115 5.1.1 Tensile Strength 116 5.1.2 Net Area 122 5.1.3 Effective Net Area 124 5.1.4 Maximum Slenderness Ratios for Tension Members 125 5.2 Compression Members 126 5.2.1 Overall Buckling (Columns) 129 5.2.2 Local Buckling (Components of Columns) 145 5.3 Members in Bending 171 5.3.1 Bending Yielding and Fracture 172
  5. 5. CONTENTS v 5.3.2 Bending Buckling 175 5.3.3 Bending Shear 199 5.4 Torsion 204 5.4.1 St. Venant Torsion 206 5.4.2 Warping Torsion 208 5.4.3 A Final Note 210 5.5 Combined Stresses 210 5.5.1 Combined Axial Compression and Bending 210 5.5.2 Combined Tension and Bending 213 5.5.3 Combined Shear, Compression, and Bending 213 5.5.4 Biaxial and Triaxial Stresses 214 6 Orientation to the Aluminum Specication 217 6.1 Background 217 6.2 The Aluminum Design Manual 219 6.3 Types of Structures Addressed by the Aluminum Specication 223 6.4 Signicant Figures and the Aluminum Specication 224 PART III DESIGN CHECKS FOR STRUCTURAL COMPONENTS 227 7 Structural Members 229 7.1 Tension Member Design Procedure 229 7.1.1 Net Effective Area 230 7.1.2 Allowable Stress 230 7.1.3 Tensile Capacity 231 7.2 Compression Member Design Procedure 231 7.2.1 Overall Column Slenderness Ratio 232 7.2.2 Slenderness Ratio of Cross-Sectional Elements 233 7.2.3 Allowable Column Stress of Typical Shapes 233 7.2.4 Summary of Allowable Column Stress 239 7.3 Bending Member Design Procedure 239 7.3.1 Bending Tension 241 7.3.2 Bending Compression 241
  6. 6. vi CONTENTS 7.3.3 Shear 247 7.4 Combined Stresses Design Procedure 247 7.4.1 Combined Axial Compression and Bending 247 7.4.2 Combined Tension and Bending 248 7.4.3 Combined Shear, Compression, and Bending 249 8 Connections 251 8.1 Mechanical Connections 251 8.1.1 Introduction 251 8.1.2 Types of Fasteners 253 8.1.3 Fastener Material Selection 259 8.1.4 Fastener Mechanical Properties 261 8.1.5 Types of Loads on Fasteners 264 8.1.6 Types of Bolted Connections 265 8.1.7 Holes 267 8.1.8 Failure Modes for Mechanically Fastened Joints 268 8.1.9 Tensile Loads on Fasteners 270 8.1.10 Shear Loads on Fasteners 272 8.1.11 Combined Shear and Tension on Bolts 276 8.1.12 Bearing Strength and Edge Distance 277 8.1.13 Tension Strength of Connected Parts 278 8.1.14 Shear Rupture 278 8.1.15 Minimum Spacing and Edge Distance 281 8.1.16 Maximum Edge Distance and Spacing 281 8.1.17 Screw Connections 284 8.1.18 Minimum Requirements for Connections 288 8.2 Welded Connections 289 8.2.1 Aluminum Welding Processes 289 8.2.2 Selecting a Filler Alloy 291 8.2.3 Types of Welds 292 8.2.4 Comparing Aluminum and Steel Fillet Weld Safety Factors 300 8.2.5 Weld Fabrication 300 8.2.6 Weld Quality Assurance 304
  7. 7. CONTENTS vii 9 Special Topics 307 9.1 Welded Members 307 9.1.1 What Welding Does to Aluminum 307 9.1.2 Types of Welded Members 310 9.1.3 Welded Tension Members 311 9.1.4 Welded Compression Members 315 9.1.5 Post-Weld Heat Treatment 318 9.2 Fatigue 319 9.2.1 FatigueWhat Is It Again? 320 9.2.2 Fatigue Design: The Ground Rules 322 9.2.3 Variable Amplitude Fatigue Design 326 9.2.4 Aluminum Versus Steel in Fatigue 327 9.2.5 Other Factors in Fatigue 328 9.2.6 A Final Word 329 9.3 Recent Developments in Aluminum Structures 329 9.3.1 Friction Stir Welding 329 9.3.2 Alloy 6082 330 9.3.3 Aluminum-Lithium Alloys 330 9.3.4 The New Aluminum Automotive Alloys 332 9.3.5 Aluminum Metal Matrix Composites 333 PART IV DESIGN OF STRUCTURAL SYSTEMS 335 10 Structural Systems Built with Aluminum 337 10.1 Cold-Formed Aluminum Construction 337 10.1.1 Building Sheathing 337 10.1.2 Cold-Formed Aluminum Design 343 10.1.3 Elastically Supported Flanges 350 10.2 Aluminum Frames 351 10.2.1 System Description 351 10.2.2 Model for Analysis 353 10.2.3 Getting Started 354 10.2.4 Analyzing the Dome 358 10.2.5 Design Checks 362 10.3 Aluminum Composite Members 373 10.3.1 Composite Beams 374 10.3.2 Thermal Stresses 375 10.3.3 Dissimilar Material Contact 378 10.4 Aluminum Pressure Piping 379
  8. 8. viii CONTENTS 10.5 Aluminum Plate Structures 383 10.5.1 Stiffeners 383 10.5.2 Compressive Strengths 385 10.5.3 Fabrication 386 PART V LOAD AND RESISTANCE FACTOR DESIGN 387 11 Load and Resistance Factor Design 389 11.1 New Tricks for Old Dogs 389 11.2 LRFDThe Concept 390 11.3 Whats New: Load Factors 391 11.4 Whats the Same 392 11.5 When Do I Use LRFD? 393 11.6 Which Way Lets Me Use Less Metal? 394 11.7 The General Expression for Comparing LRFD to ASD 397 11.8 How They Came Up with the LRFD Specication 399 11.9 How Do I Actually Start Using LRFD? 405 11.10 The Future of the ASD and LRFD Aluminum Specications 406 Appendixes A. Pre-1954 Wrought Alloy Designations 407 B. Section Properties of Common Aluminum Shapes 409 C. Minimum Mechanical Properties of Aluminum Alloys 413 D. Allowable Stresses for Elements of Common Aluminum Shapes 425 E. LRFD Design Stresses for Elements of Common Aluminum Shapes 429 F. Column Buckling Allowable Stress 433 G. Summary of the Aluminum Specication Design Provisions for Columns and Beams 435 H. Cross Reference to the Aluminum Specication 437 I. LRFD Design Stresses for Various Alloys 441 J. Other Aluminum Structural Design Specications 463 K. Buckling Constants 469 L. Metric Conversions 475 M. Statistics 477 N. Technical Organizations 495 Glossary 503 References 519 Index 527
  9. 9. ix PREFACE TO THE FIRST EDITION The purpose of this book is to enlighten humanity and contribute to the gen- eral betterment of this orb that we call home. Failing that, we will settle for giving engineers enough guidance in the use of aluminum that they will feel condent designing with it. The Aluminum Association, an industry associ- ation of aluminum producers, publishes the Specications for Aluminum Structures (hereafter called the Aluminum Specications), which are the gen- erally accepted criteria for the design of aluminum structures. Our book is keyed to the sixth edition of the Aluminum Specications, and readers should have access to it. Structural engineering may be regarded as the practice of analyzing and designing structures. The analysis process resolves the loads applied to the structure into the resulting forces and moments in the components of the structure. Structural design is, then, the sizing of the structures components to safely sustain these forces and moments. Academic curricula typically train students in structural analysis, as well as in the design methods appropriate to common materials of construction (i.e., steel, concrete, and perhaps timber), and many excellent texts on these subjects are available. We assume that the reader is already well versed in structural analysis and acquainted with steel design. Our objective is to expand readers design