Load and Resistance Factor Design Specification for Structural Steel Buildi

  LOAD AND RESISTANCE FACTOR DESIGN SPECIFICATION For Structural Steel Buildings

  December 27, 1999

  Load and Resistance Factor Design Specification

for Structural Steel Buildings

  December 27, 1999

  

Supersedes the Load and Resistance Factor Design Specification

for Structural Steel Buildings dated December 1, 1993 and all previous versions.

  Prepared by the American Institute of Steel Construction, Inc. Under the Direction of the

  AISC Committee on Specifications and approved by the AISC Board of Directors.

AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC.

  One East Wacker Drive, Suite 3100 Chicago, Illinois 60601-2001 with errata incorporated as of September 4, 2001 ii

  Copyright © 2000 by American Institute of Steel Construction, Inc.

  

All rights reserved. This book or any part thereof must not be reproduced in any

form without the written permission of the publisher.

  

The information presented in this publication has been prepared in accordance with

recognized engineering principles and is for general information only. While it is

believed to be accurate, this information should not be used or relied upon for any

specific application without competent professional examination and verification of

its accuracy, suitability, and applicability by a licensed engineer, architect or other

professional. The publication of the material contained herein is not intended as a

representation or warranty on the part of the American Institute of Steel Construc-

tion, Inc. or of any other person named herein, that this information is suitable for

any general or particular use or of freedom from infringement of any patent or pat-

ents. Anyone making use of this information assumes all liability arising from such

use.

Caution must be exercised when relying upon other specifications and codes devel-

oped by other bodies and incorporated by reference herein since such material may

be modified or amended from time to time subsequent to the printing of this edition.

The American Institute of Steel Construction, Inc. bears no responsibility for such

material other than to refer to it and incorporate it by reference at the time of the

initial publication of this edition.

  

Printed in the United States of America

, December 27, 1999

  LRFD Specification for Structural Steel Buildings iii

PREFACE

  The AISC Load and Resistance Factor Design (LRFD) Specification for Structural Steel

  

Buildings is based on reliability theory. As have all AISC Specifications, this Specifica-

  tion has been based upon past successful usage, advances in the state of knowledge, and changes in design practice. This Specification has been developed as a consensus docu- ment to provide a uniform practice in the design of steel-framed buildings. The intention is to provide design criteria for routine use and not to provide specific criteria for infre- quently encountered problems, which occur in the full range of structural design. This Specification is the result of the consensus deliberations of a committee of structural engineers with wide experience and high professional standing, representing a wide geo- graphical distribution throughout the U.S. The committee includes approximately equal numbers of engineers in private practice and code agencies, engineers involved in research and teaching, and engineers employed by steel fabricating and producing com- panies. The contributions and assistance of more than 50 additional professional volun- teers working in 15 task committees are also hereby acknowledged. The Symbols, Glossary, and Appendices to this Specification are an integral part of the Specification. A non-mandatory Commentary has been prepared to provide background for the Specification provisions and the user is encouraged to consult it.

  The principal changes incorporated in this edition of the Specification include:

• • Dual units format. Values and equations are given in both U.S. customary

  and metric units. The metric conversions (given in parentheses following the U.S. units) are based on ASTM E380, Standard Practice for Use of the

  

International System of Units (SI) . The equations are non-dimensionalized

where possible by factoring out material constants, such as E and G.

• Inclusion of new structural steels ASTM A913 and A992.
• Additional notch toughness requirements for complete-joint-penetration groove welds with tension applied normal to the effective area.
• New provisions for stability bracing of beams, columns, and frames.
• New Chapter N for evaluation of existing structures.
• Revised provisions for member design under fatigue loading in Appendix K.

  , December 27, 1999 LRFD Specification for Structural Steel Buildings

• Reorganization of material on pin-connected members and eyebars.
• Revised provisions for concrete-encased beams.
• New limitation on the stud reduction factor when a single stud is used in a rib.
• Revised bolt bearing strength criteria.

  The reader is cautioned that professional judgment must be exercised when data or recom- mendations in the Specification are applied, as described more fully in the disclaimer notice preceding this Preface. By the Committee, Stanley D. Lindsey, Chairman Nestor R. Iwankiw Roger E. Ferch, Vice Chairman Lawrence A. Kloiber Hansraj G. Ashar Roberto T. Leon William F. Baker H.S. Lew John M. Barsom James O. Malley Reidar Bjorhovde Richard W. Marshall Roger L. Brockenbrough Harry W. Martin Wai-Fah Chen William A. Milek Gregory G. Deierlein Duane K. Miller Robert O. Disque Thomas M. Murray Duane S. Ellifritt R. Shankar Nair Bruce R. Ellingwood Clarkson W. Pinkham Shu-Jin Fang Douglas D. Rees-Evans Steven J. Fenves Thomas Z. Scarangello James M. Fisher Donald R. Sherman John W. Fisher W. Lee Shoemaker Theodore V. Galambos Frank F. Sowokinos Lawrence G. Griffis William A. Thornton James R. Harris Raymond H. R. Tide Tony C. Hazel Ivan M. Viest Mark V. Holland Joseph A. Yura

  Cynthia J. Lanz, Secretary

  iv PREFACE LRFD Specification for Structural Steel Buildings

  , December 27, 1999 v

TABLE OF CONTENTS

  

SYMBOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii

SPECIFICATION

  

A. GENERAL PROVISIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

  A1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 A2. Types of Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 A3. Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

  1. Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

  2. Steel Castings and Forgings . . . . . . . . . . . . . . . . . . . . . . 4

  3. Bolts, Washers, and Nuts . . . . . . . . . . . . . . . . . . . . . . . . 4

  4. Anchor Rods and Threaded Rods . . . . . . . . . . . . . . . . . . . 5

  5. Filler Metal and Flux for Welding . . . . . . . . . . . . . . . . . . . 5

  6. Stud Shear Connectors . . . . . . . . . . . . . . . . . . . . . . . . . 6 A4. Loads and Load Combinations . . . . . . . . . . . . . . . . . . . . . . . 6 A5. Design Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

  1. Required Strength at Factored Loads . . . . . . . . . . . . . . . . . . 6

  2. Limit States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

  3. Design for Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

  4. Design for Serviceability and Other Considerations . . . . . . . . . . 7 A6. Referenced Codes and Standards . . . . . . . . . . . . . . . . . . . . . . 7 A7. Design Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

  

B. DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . 10

  B1. Gross Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 B2. Net Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 B3. Effective Area of Tension Members . . . . . . . . . . . . . . . . . . . . 10 B4. Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 B5. Local Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

  1. Classification of Steel Sections . . . . . . . . . . . . . . . . . . . . 12

  2. Design by Plastic Analysis . . . . . . . . . . . . . . . . . . . . . . 13

  3. Slender-Element Compression Sections . . . . . . . . . . . . . . . 13 B6. Bracing at Supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 B7. Limiting Slenderness Ratios . . . . . . . . . . . . . . . . . . . . . . . . 13 B8. Simple Spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 B9. End Restraint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 B10. Proportions of Beams and Girders . . . . . . . . . . . . . . . . . . . . . 13

  

C. FRAMES AND OTHER STRUCTURES . . . . . . . . . . . . . . . . . . . 17

  C1. Second Order Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

  1. Design by Plastic Analysis . . . . . . . . . . . . . . . . . . . . . . 17

  2. Design by Elastic Analysis . . . . . . . . . . . . . . . . . . . . . . 17 C2. Frame Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

  1. Braced Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

  2. Unbraced Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

  , December 27, 1999 LRFD Specification for Structural Steel Buildings vi TABLE OF CONTENTS SPECIFICATION (Cont’d)

  C3. Stability Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

  1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

  2. Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

  3. Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

  4. Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

  

D. TENSION MEMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

  D1. Design Tensile Strength . . . . . . . . . . . . . . . . . . . . . . . . . . 24 D2. Built-Up Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 D3. Pin-Connected Members and Eyebars . . . . . . . . . . . . . . . . . . . 25

  1. Pin-Connected Members . . . . . . . . . . . . . . . . . . . . . . . 25

  2. Eyebars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

  

E. COLUMNS AND OTHER COMPRESSION MEMBERS. . . . . . . . . . 27

  E1. Effective Length and Slenderness Limitations. . . . . . . . . . . . . . . 27

  1. Effective Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

  2. Design by Plastic Analysis . . . . . . . . . . . . . . . . . . . . . . 27 E2. Design Compressive Strength for Flexural Buckling . . . . . . . . . . . 27 E3. Design Compressive Strength for Flexural-Torsional Buckling . . . . . . 28 E4. Built-Up Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

  1. Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

  2. Detailing Requirements . . . . . . . . . . . . . . . . . . . . . . . . 29 E5. Connections for Pin-Connected Compression Members . . . . . . . . . . 30

  

F. BEAMS AND OTHER FLEXURAL MEMBERS . . . . . . . . . . . . . . 31

  F1. Design for Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

  1. Yielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

  2. Lateral-Torsional Buckling . . . . . . . . . . . . . . . . . . . . . . 32

  3. Design by Plastic Analysis . . . . . . . . . . . . . . . . . . . . . . 34 F2. Design for Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

  1. Web Area Determination . . . . . . . . . . . . . . . . . . . . . . . 35

  2. Design Shear Strength. . . . . . . . . . . . . . . . . . . . . . . . . 35

  3. Transverse Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . 36 F3. Web-Tapered Members . . . . . . . . . . . . . . . . . . . . . . . . . . 36 F4. Beams and Girders with Web Openings . . . . . . . . . . . . . . . . . . 36

  

G. PLATE GIRDERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

  

H. MEMBERS UNDER COMBINED FORCES AND TORSION . . . . . . . 38

  H1. Symmetric Members Subject to Bending and Axial Force . . . . . . . . 38

  1. Doubly and Singly Symmetric Members in Flexure and Tension . . 38

  2. Doubly and Singly Symmetric Members in Flexure and Compression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

  H2. Unsymmetric Members and Members Under Torsion and Combined Torsion, Flexure, Shear, and/or Axial Force . . . . . . . . . . 39

  H3. Alternative Interaction Equations for Members Under Combined Stress (see Appendix H3) . . . . . . . . . . . . . . . . . . . . . . . . . 39

I. COMPOSITE MEMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

  I1. Design Assumptions and Definitions . . . . . . . . . . . . . . . . . . . 40

  I2. Compression Members. . . . . . . . . . . . . . . . . . . . . . . . . . . 41

  1. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

  LRFD Specification for Structural Steel Buildings , December 27, 1999

  SPECIFICATION (Cont’d)

  56

  6. Beam Copes and Weld Access Holes. . . . . . . . . . . . . . . . . 50

  7. Minimum Strength of Connections . . . . . . . . . . . . . . . . . . 50

  8. Placement of Welds and Bolts . . . . . . . . . . . . . . . . . . . . 51

  9. Bolts in Combination with Welds . . . . . . . . . . . . . . . . . . 51

  10. High-Strength Bolts in Combination with Rivets . . . . . . . . . . . 51

  11. Limitations on Bolted and Welded Connections . . . . . . . . . . . 51 J2. Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

  1. Groove Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

  2. Fillet Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

  3. Plug and Slot Welds . . . . . . . . . . . . . . . . . . . . . . . . . 56 4. Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . .

  5. Combination of Welds. . . . . . . . . . . . . . . . . . . . . . . . . 58

  4. Compression Members with Bearing Joints . . . . . . . . . . . . . 49

  6. Weld Metal Requirements . . . . . . . . . . . . . . . . . . . . . . 58

  7. Mixed Weld Metal. . . . . . . . . . . . . . . . . . . . . . . . . . . 58

  8. Preheat for Heavy Shapes . . . . . . . . . . . . . . . . . . . . . . . 58 J3. Bolts and Threaded Parts. . . . . . . . . . . . . . . . . . . . . . . . . . 58

  1. High-Strength Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . 58

  2. Size and Use of Holes . . . . . . . . . . . . . . . . . . . . . . . . 59

  3. Minimum Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . 60

  4. Minimum Edge Distance . . . . . . . . . . . . . . . . . . . . . . . 60

  5. Maximum Spacing and Edge Distance . . . . . . . . . . . . . . . . 60

  6. Design Tension or Shear Strength . . . . . . . . . . . . . . . . . . 62

  5. Splices in Heavy Sections . . . . . . . . . . . . . . . . . . . . . . 49

  3. Moment Connections . . . . . . . . . . . . . . . . . . . . . . . . . 49

  2. Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

  I4. Combined Compression and Flexure . . . . . . . . . . . . . . . . . . . 46

  3. Columns with Multiple Steel Shapes . . . . . . . . . . . . . . . . . 42

  4. Load Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

  I3. Flexural Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

  1. Effective Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

  2. Design Strength of Beams with Shear Connectors . . . . . . . . . . 43

  3. Design Strength of Concrete-Encased Beams . . . . . . . . . . . . 44

  4. Strength During Construction . . . . . . . . . . . . . . . . . . . . . 44

  5. Formed Steel Deck . . . . . . . . . . . . . . . . . . . . . . . . . . 44

  6. Design Shear Strength. . . . . . . . . . . . . . . . . . . . . . . . . 46

  I5. Shear Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

  2. Simple Connections . . . . . . . . . . . . . . . . . . . . . . . . . 49

  1. Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

  2. Horizontal Shear Force . . . . . . . . . . . . . . . . . . . . . . . . 46

  3. Strength of Stud Shear Connectors . . . . . . . . . . . . . . . . . . 47

  4. Strength of Channel Shear Connectors . . . . . . . . . . . . . . . . 47

  5. Required Number of Shear Connectors . . . . . . . . . . . . . . . . 47

  6. Shear Connector Placement and Spacing . . . . . . . . . . . . . . . 48

  I6. Special Cases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

  

J. CONNECTIONS, JOINTS, AND FASTENERS . . . . . . . . . . . . . . . 49

  J1. General Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

  1. Design Basis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

  LRFD Specification for Structural Steel Buildings , December 27, 1999 TABLE OF CONTENTS vii

  SPECIFICATION (Cont’d)

  1. Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

  7. Web Panel-Zone Shear . . . . . . . . . . . . . . . . . . . . . . . . 75

  8. Unframed Ends of Beams and Girders . . . . . . . . . . . . . . . . 76

  9. Additional Stiffener Requirements for Concentrated Forces . . . . . 76

  10. Additional Doubler Plate Requirements for Concentrated Forces . . 76 K2. Ponding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 K3. Design for Cyclic Loading (Fatigue). . . . . . . . . . . . . . . . . . . . 77

  

L. SERVICEABILITY DESIGN CONSIDERATIONS . . . . . . . . . . . . . 79

  L1. Camber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 L2. Expansion and Contraction . . . . . . . . . . . . . . . . . . . . . . . . 79 L3. Deflections, Vibration, and Drift . . . . . . . . . . . . . . . . . . . . . 79

  2. Floor Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

  5. Web Sidesway Buckling. . . . . . . . . . . . . . . . . . . . . . . . 73

  3. Drift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 L4. Connection Slip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 L5. Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

  

M. FABRICATION, ERECTION, AND QUALITY CONTROL . . . . . . . . 81

  M1. Shop Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 M2. Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

  1. Cambering, Curving, and Straightening . . . . . . . . . . . . . . . 81

  2. Thermal Cutting . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

  3. Planing of Edges . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

  6. Web Compression Buckling . . . . . . . . . . . . . . . . . . . . . 74

  4. Web Crippling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

  7. Combined Tension and Shear in Bearing-Type Connections . . . . . 63

  3. Block Shear Rupture Strength. . . . . . . . . . . . . . . . . . . . . 67 J5. Connecting Elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

  8. High-Strength Bolts in Slip-Critical Connections . . . . . . . . . . 64

  9. Combined Tension and Shear in Slip-Critical Connections . . . . . 66

  10. Bearing Strength at Bolt Holes . . . . . . . . . . . . . . . . . . . . 66

  11. Long Grips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 J4. Design Rupture Strength . . . . . . . . . . . . . . . . . . . . . . . . . . 67

  1. Shear Rupture Strength . . . . . . . . . . . . . . . . . . . . . . . . 67

  2. Tension Rupture Strength. . . . . . . . . . . . . . . . . . . . . . . 67

  1. Eccentric Connections. . . . . . . . . . . . . . . . . . . . . . . . . 68

  3. Web Local Yielding . . . . . . . . . . . . . . . . . . . . . . . . . . 72

  2. Design Strength of Connecting Elements in Tension . . . . . . . . . 68

  3. Other Connecting Elements . . . . . . . . . . . . . . . . . . . . . . 68 J6. Fillers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 J7. Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 J8. Bearing Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 J9. Column Bases and Bearing on Concrete. . . . . . . . . . . . . . . . . . 70 J10. Anchor Rods and Embedments . . . . . . . . . . . . . . . . . . . . . . 70

  

K. CONCENTRATED FORCES, PONDING, AND FATIGUE. . . . . . . . . 71

  K1. Flanges and Webs with Concentrated Forces . . . . . . . . . . . . . . . 71

  1. Design Basis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

  2. Flange Local Bending . . . . . . . . . . . . . . . . . . . . . . . . 71

  viii TABLE OF CONTENTS LRFD Specification for Structural Steel Buildings , December 27, 1999

  SPECIFICATION (Cont’d)

  1. Dimensional Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

  N1. General Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 N2. Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

  1. Determination of Required Tests . . . . . . . . . . . . . . . . . . . 86

  2. Tensile Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

  3. Chemical Composition . . . . . . . . . . . . . . . . . . . . . . . . 86

  4. Base Metal Notch Toughness . . . . . . . . . . . . . . . . . . . . . 87

  5. Weld Metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

  6. Bolts and Rivets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 N3. Evaluation by Structural Analysis . . . . . . . . . . . . . . . . . . . . . 87

  2. Strength Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 87

  5. Identification of Steel . . . . . . . . . . . . . . . . . . . . . . . . . 85

  3. Serviceability Evaluation . . . . . . . . . . . . . . . . . . . . . . . 87 N4. Evaluation by Load Tests . . . . . . . . . . . . . . . . . . . . . . . . . 88

  1. Determination of Live Load Rating by Testing . . . . . . . . . . . . 88

  2. Serviceability Evaluation . . . . . . . . . . . . . . . . . . . . . . . 88 N5. Evaluation Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

  

APPENDIX B. DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . 89

  B5. Local Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

  1. Classification of Steel Sections . . . . . . . . . . . . . . . . . . . . 89

  3. Slender-Element Compression Sections . . . . . . . . . . . . . . . 89

  

APPENDIX E. COLUMNS AND OTHER COMPRESSION MEMBERS . . . 94

LRFD Specification for Structural Steel Buildings , December 27, 1999

  

N. EVALUATION OF EXISTING STRUCTURES . . . . . . . . . . . . . . . 86

  4. Inspection of Slip-Critical High-Strength Bolted Connections . . . . 85

  4. Welded Construction . . . . . . . . . . . . . . . . . . . . . . . . . 82

  5. Surfaces Adjacent to Field Welds . . . . . . . . . . . . . . . . . . 83 M4. Erection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

  5. Bolted Construction . . . . . . . . . . . . . . . . . . . . . . . . . 82

  6. Compression Joints . . . . . . . . . . . . . . . . . . . . . . . . . . 82

  7. Dimensional Tolerances . . . . . . . . . . . . . . . . . . . . . . . . 82

  8. Finish of Column Bases . . . . . . . . . . . . . . . . . . . . . . . . 82 M3. Shop Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

  1. General Requirements . . . . . . . . . . . . . . . . . . . . . . . . 83

  2. Inaccessible Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . 83

  3. Contact Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

  4. Finished Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

  1. Alignment of Column Bases . . . . . . . . . . . . . . . . . . . . . 83

  3. Inspection of Welding . . . . . . . . . . . . . . . . . . . . . . . . 85

  2. Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

  3. Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

  4. Fit of Column Compression Joints and Base Plates . . . . . . . . . 84

  5. Field Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

  6. Field Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

  7. Field Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 M5. Quality Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

  1. Cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

  2. Rejections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

  TABLE OF CONTENTS ix x TABLE OF CONTENTS SPECIFICATION (Cont’d)

  E3. Design Compressive Strength for Flexural-Torsional Buckling . . . . . . 94

  

APPENDIX F. BEAMS AND OTHER FLEXURAL MEMBERS . . . . . . . . 96

  F1. Design for Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 F2. Design for Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

  2. Design Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . 102

  3. Transverse Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . 102 F3. Web-Tapered Members . . . . . . . . . . . . . . . . . . . . . . . . . . 103

  1. General Requirements . . . . . . . . . . . . . . . . . . . . . . . . 103

  2. Design Tensile Strength . . . . . . . . . . . . . . . . . . . . . . . 103

  3. Design Compressive Strength . . . . . . . . . . . . . . . . . . . . 103

  4. Design Flexural Strength. . . . . . . . . . . . . . . . . . . . . . . 104

  5. Design Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . 106

  6. Combined Flexure and Axial Force . . . . . . . . . . . . . . . . . 106

  

APPENDIX G. PLATE GIRDERS . . . . . . . . . . . . . . . . . . . . . . . . 107

  G1. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 G2. Design Flexural Strength. . . . . . . . . . . . . . . . . . . . . . . . . 107 G3. Design Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . 109 G4. Transverse Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 G5. Flexure-Shear Interaction . . . . . . . . . . . . . . . . . . . . . . . . . 111

APPENDIX H. MEMBERS UNDER COMBINED FORCES AND

  TORSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

  H3. Alternative Interaction Equations for Members Under Combined Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

  

APPENDIX J. CONNECTIONS, JOINTS, AND FASTENERS . . . . . . . . 115

  J2. Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

  4. Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 J3. Bolts and Threaded Parts . . . . . . . . . . . . . . . . . . . . . . . . . 117

  7. Combined Tension and Shear in Bearing-Type Connections . . . . 117

  8. High-Strength Bolts in Slip-Critical Connections . . . . . . . . . . 117

  9. Combined Tension and Shear in Slip-Critical Connections . . . . . 117

  

APPENDIX K. CONCENTRATED FORCES, PONDING, AND FATIGUE . 118

  K2. Ponding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 K3. Design for Cyclic Loading (Fatigue) . . . . . . . . . . . . . . . . . . . 121

  1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

  2. Calculation of Maximum Stresses and Stress Ranges . . . . . . . . 121

  3. Design Stress Range . . . . . . . . . . . . . . . . . . . . . . . . . 122

  4. Bolts and Threaded Parts . . . . . . . . . . . . . . . . . . . . . . 124

  5. Special Fabrication and Erection Requirements . . . . . . . . . . . 124

  

NUMERICAL VALUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

COMMENTARY

  

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

A. GENERAL PROVISIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 164

  A1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 A2. Types of Construction . . . . . . . . . . . . . . . . . . . . . . . . . . 164

  , December 27, 1999 LRFD Specification for Structural Steel Buildings

  COMMENTARY (Cont’d)

  

D. TENSION MEMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

  TABLE OF CONTENTS xi LRFD Specification for Structural Steel Buildings

  Combined Torsion, Flexure, Shear, and/or Axial Force . . . . . . . . . 213

  H1. Symmetric Members Subject to Bending and Axial Force . . . . . . . . 212 H2. Unsymmetric Members and Members Under Torsion and

  

H. MEMBERS UNDER COMBINED FORCES AND TORSION . . . . . . 212

  3. Design by Plastic Analysis. . . . . . . . . . . . . . . . . . . . . . 209 F2. Design for Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210 F4. Beams and Girders with Web Openings . . . . . . . . . . . . . . . . . 210

  2. Lateral-Torsional Buckling . . . . . . . . . . . . . . . . . . . . . 206

  1. Yielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

  F1. Design for Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

  

F. BEAMS AND OTHER FLEXURAL MEMBERS. . . . . . . . . . . . . . 206

  2. Design by Plastic Analysis . . . . . . . . . . . . . . . . . . . . . 203 E2. Design Compressive Strength for Flexural Buckling. . . . . . . . . . . 203 E3. Design Compressive Strength for Flexural-Torsional Buckling . . . . . 204 E4. Built-Up Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

  1. Effective Length . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

  E1. Effective Length and Slenderness Limitations. . . . . . . . . . . . . . 203

  

E. COLUMNS AND OTHER COMPRESSION MEMBERS. . . . . . . . . 203

  D1. Design Tensile Strength. . . . . . . . . . . . . . . . . . . . . . . . . . 202 D2. Built-Up Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202 D3. Pin-Connected Members and Eyebars . . . . . . . . . . . . . . . . . . 202

  4. Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

  A3. Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

  3. Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

  1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

  C1. Second Order Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 C2. Frame Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 C3. Stability Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

  

C. FRAMES AND OTHER STRUCTURES . . . . . . . . . . . . . . . . . . 184

  B2. Net Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 B3. Effective Area of Tension Members . . . . . . . . . . . . . . . . . . . 177 B5. Local Buckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 B7. Limiting Slenderness Ratios . . . . . . . . . . . . . . . . . . . . . . . 182

  

B. DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . 177

  4. Design for Serviceability and Other Considerations . . . . . . . . 176

  3. Design for Strength . . . . . . . . . . . . . . . . . . . . . . . . . 172

  2. Limit States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

  1. Required Strength at Factored Loads . . . . . . . . . . . . . . . . 172

  5. Filler Metal and Flux for Welding . . . . . . . . . . . . . . . . . . 170 A4. Loads and Load Combinations . . . . . . . . . . . . . . . . . . . . . . 171 A5. Design Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

  4. Anchor Rods and Threaded Rods . . . . . . . . . . . . . . . . . . 170

  3. Bolts, Washers, and Nuts . . . . . . . . . . . . . . . . . . . . . . 169

  1. Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

  , December 27, 1999

  COMMENTARY (Cont’d)

  xii TABLE OF CONTENTS LRFD Specification for Structural Steel Buildings , December 27, 1999

I. COMPOSITE MEMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . 214

  1. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

  2. Size and Use of Holes . . . . . . . . . . . . . . . . . . . . . . . . 241

  10. High-Strength Bolts in Combination with Rivets . . . . . . . . . . 232 J2. Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

  1. Groove Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

  2. Fillet Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

  4. Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . 238

  5. Combination of Welds . . . . . . . . . . . . . . . . . . . . . . . 239

  6. Weld Metal Requirements . . . . . . . . . . . . . . . . . . . . . . 239

  7. Mixed Weld Metal . . . . . . . . . . . . . . . . . . . . . . . . . . 240 J3. Bolts and Threaded Parts . . . . . . . . . . . . . . . . . . . . . . . . . 240

  1. High-Strength Bolts . . . . . . . . . . . . . . . . . . . . . . . . . 240

  3. Minimum Spacing . . . . . . . . . . . . . . . . . . . . . . . . . 241

  8. Placement of Welds and Bolts . . . . . . . . . . . . . . . . . . . . 231

  4. Minimum Edge Distance . . . . . . . . . . . . . . . . . . . . . . 241

  5. Maximum Spacing and Edge Distance . . . . . . . . . . . . . . . 242

  6. Design Tension or Shear Strength . . . . . . . . . . . . . . . . . . 242

  7. Combined Tension and Shear in Bearing-Type Connections . . . . 243

  8. High-Strength Bolts in Slip-Critical Connections . . . . . . . . . 243

  10. Bearing Strength at Bolt Holes . . . . . . . . . . . . . . . . . . . 246

  11. Long Grips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 J4. Design Rupture Strength . . . . . . . . . . . . . . . . . . . . . . . . . 246 J5. Connecting Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . 248

  I2. Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . 215

  9. Bolts in Combination with Welds . . . . . . . . . . . . . . . . . . 231

  5. Splices in Heavy Sections . . . . . . . . . . . . . . . . . . . . . . 229

  2. Design Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

  6. Design Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . 225

  3. Columns with Multiple Steel Shapes . . . . . . . . . . . . . . . . 216

  4. Load Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

  I3. Flexural Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

  1. Effective Width . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

  2. Design Strength of Beams with Shear Connectors . . . . . . . . . 217

  3. Design Strength of Concrete-Encased Beams . . . . . . . . . . . 221