ANSI/AISC 341-05 ANSI/AISC 341s1-05 An American National Standard Seismic Provisions for Structural Steel Buildings Including Supplement No. 1 Seismic Provisions for Structural Steel Buildings dated March 9, 2005 and Supplement No. 1 dated November 16, 2005 Supersedes the Seismic Provisions for Structural Steel Buildings dated May 21, 2002 and all previous versions Approved by the AISC Committee on Specifications and issued by the AISC Board of Directors AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. One East Wacker Drive, Suite 700 Chicago, Illinois 60601-1802 SSeeiissmmiiccPPrroovv11..iinndddd ii 99//88//0066 33::5599::0000 PPMM PPrroocceessss BBllaacckk 6.1–ii Copyright © 2005 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 AISC logo is a registered trademark of AISC and is used under license. 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 Construction, 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 patents. Anyone making use of this information assumes all liability arising from such use. Caution must be exercised when relying upon other specifications and codes developed 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. Second Printing October 2006 Third Printing March 2008 Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd iiii 22//66//0088 1100::1111::1144 AAMM 6.1–iii PREFACE This Preface is not a part of ANSI/AISC 341-05, Seismic Provisions for Structural Steel Buildings, but is included for informational purposes only. The AISC Specification for Structural Steel Buildings (ANSI/AISC 360-05) is intended to cover common design criteria. Accordingly, it is not feasible for it to also cover all of the special and unique problems encountered within the full range of structural design practice. This document, the AISC Seismic Provisions for Structural Steel Buildings (ANSI/AISC 341- 05) with Supplement No. 1 (ANSI/AISC 341s1-05) (hereafter referred to as the Provisions) is a separate consensus standard that addresses one such topic: the design and construction of structural steel and composite structural steel/reinforced concrete building systems for high- seismic applications. Supplement No. 1 consists of modifications made to Part I, Section 14 of the Provisions after the initial approval had been completed. These Provisions are presented in two parts: Part I is intended for the design and construction of structural steel buildings, and is written in a unified format that addresses both LRFD and ASD; Part II is intended for the design and construction of composite structural steel/ reinforced concrete buildings, and is written to address LRFD only. In addition, seven mandatory appendices, a list of Symbols, and Glossary are part of this document. Terms that appear in the Glossary are generally italicized where they first appear in a sub-section, throughout these Provisions. A nonmandatory Commentary with background information is also provided. The previous edition of the AISC Seismic Provisions for Structural Steel Buildings, approved on May 21, 2002, incorporated many of the advances achieved as part of the FEMA/SAC program and other investigations and developments related to the seismic design of steel buildings. Recognizing that rapid and significant changes in the knowledge base were occurring for the seismic design of steel buildings, especially moment frames, the AISC Committee on Specifications committed to generating frequent supplements to the Provisions. This commitment was intended to keep the provisions as current as possible. These Provisions were modified to be consistent with SEI/ASCE 7-05, Minimum Design Loads for Buildings and Other Structures. Although this standard adopts SEI/ASCE 7-02, it was being developed in parallel with SEI/ASCE 7-05. It is anticipated that ASCE will publish a supplement to SEI/ASCE 7-05 in 2006 that will adopt ANSI/AISC 341 and 360 by reference. We encourage anyone who is using these AISC standards to use them in conjunction with SEI/ASCE 7-05 including Supplement No. 1, when it becomes available. This allows these Provisions to be incorporated by reference into both the 2006 IBC and 2006 NFPA 5000 building codes, each of which uses SEI/ASCE 7-05 as its basis for design loadings. Because the extent of changes that have been made to these Provisions, as a result of incorporating both technical changes and the unified format is so large, they are being republished in their entirety. The most significant modification is that two systems initially developed and incorporated into the 2003 NEHRP Provisions, the buckling-restrained braced frame (BRBF) and the special plate shear wall (SPSW) have been added to the Provisions. A major update to the commentary is also provided. A number of other significant technical modifications are included, as follows: Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd iiiiii 99//88//0066 33::5599::0011 PPMM PPrroocceessss BBllaacckk 6.1–iv PREFACE (cid:129) Clarifying that the scope of structures covered includes “building-like nonbuilding structures.” (cid:129) Clarifying that all steel buildings designed with an R factor greater than 3 must comply with the Provisions. (cid:129) Adding new requirements to delineate the expectations for structural design drawings and specifications, shop drawings and erection drawings. (cid:129) Adding new ASTM material specifications that are commonly used in the metal building industry. (cid:129) Adding R values for all materials to be used in determining susceptibility of connections t to fracture limit states. (cid:129) Relaxing the limitations on use of oversized holes in bolted joints. (cid:129) Defining a new term, “demand critical welds,” which have additional quality and toughness requirements. For each system, welds considered to be demand critical are defined. (cid:129) Defining a new term, “protected zone,” to ensure that areas subject to significant inelastic deformations are not disturbed by other building construction operations. For each system, what areas are considered to be protected zones are defined. (cid:129) Expanding the applicability of requirements on splices in columns that are part of the seismic load resisting system in moment frames to all systems. (cid:129) Improving the provisions related to the design of column bases. (cid:129) Making the stability bracing requirements more consistent throughout the document. (cid:129) Added references to the new AISC Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications (ANSI/AISC 358-05) as one means for SMF, IMF and EBF (link-to-column) connection acceptance. (cid:129) Decreasing the column splice shear capacity requirements for SMF systems. (cid:129) Increasing the stability bracing requirements for IMF systems. (cid:129) Clarifying that connections meeting the requirements for SMF or IMF systems are also acceptable for OMF applications. (cid:129) Increasing the requirements on SCBF systems that employ braces with high Kl/r ratios. (cid:129) Reducing the connection force demand on OCBF bracing to allow the use of the amplified seismic load. (cid:129) Eliminating the requirement to design all members in OCBF systems for the amplified seismic load, done for consistency with a corresponding reduction in the R factor for this system in SEI/ASCE 7-05 including Supplement 1. (cid:129) Adding specific requirements for OCBF above seismic isolation systems. (cid:129) Significantly improving the provisions related to quality assurance and quality control to address many of the issues identified in FEMA 353. (cid:129) Making changes to Part II to be consistent with the modifications to Part I and changes to ACI 318. Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd iivv 99//88//0066 33::5599::0011 PPMM PPrroocceessss BBllaacckk PREFACE 6.1–v The AISC Committee on Specifications, Task Committee 9—Seismic Provisions is responsible for the ongoing development of these Provisions. The AISC Committee on Specifications gives final approval of the document through an ANSI-accredited balloting process, and has enhanced these Provisions through careful scrutiny, discussion, and suggestions for improvement. AISC further acknowledges the significant contributions of several groups to the completion of this document: the Building Seismic Safety Council (BSSC), the SAC Joint Venture, the Federal Emergency Management Agency (FEMA), the National Science Foundation (NSF), and the Structural Engineers Association of California (SEAOC). The reader is cautioned that professional judgment must be exercised when data or recommendations in these provisions are applied, as described more fully in the disclaimer notice preceding the Preface. This specification was approved by the AISC Committee on Specifications: James M. Fisher, Chairman Tony C. Hazel Roger E. Ferch, Vice Chairman Mark V. Holland Hansraj G. Ashar Lawrence A. Kloiber William F. Baker Roberto T. Leon John M. Barsom Stanley D. Lindsey William D. Bast James O. Malley Reidar Bjorhovde Richard W. Marshall (deceased) Roger L. Brockenbrough Harry W. Martin Gregory G. Deierlein David L. McKenzie Duane S. Ellifritt Duane K. Miller Bruce R. Ellingwood Thomas M. Murray Michael Engelhardt R. Shankar Nair Shu-Jin Fang Jack E. Petersen Steven J. Fenves Douglas A. Rees-Evans John W. Fisher Robert E. Shaw, Jr. Timothy P. Fraser Donald R. Sherman Theodore V. Galambos Lee Shoemaker Louis F. Geschwindner William A. Thornton Lawrence G. Griffis Raymond H. R. Tide John L. Gross Cynthia J. Duncan, Secretary The Committee gratefully acknowledges the following task committee (TC 9—Seismic Design) for their development of this document. James O. Malley, Chairman Roberto T. Leon Mark C. Saunders, Vice Chairman Robert T. Lyons Roy Becker Sanjeev R. Malushte Gregory G. Deierlein Harry W. Martin Richard M. Drake Clarkson W. Pinkham Michael D. Engelhardt Rafael Sabelli Roger E. Ferch Thomas A. Sabol Timothy P. Fraser Robert E. Shaw, Jr. Subhash C. Goel Kurt D. Swensson James R. Harris Cynthia J. Duncan, Secretary Patrick M. Hassett Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd vv 99//88//0066 33::5599::0011 PPMM PPrroocceessss BBllaacckk 6.1–vi Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd vvii 99//88//0066 33::5599::0011 PPMM PPrroocceessss BBllaacckk 6.1–vii TABLE OF CONTENTS SYMBOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 PART I STRUCTURAL STEEL BUILDINGS — PROVISIONS GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 1. SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 2. REFERENCED SPECIFICATIONS, CODES, AND STANDARDS . . . . . . . . 15 3. GENERAL SEISMIC DESIGN REQUIREMENTS . . . . . . . . . . . . . . . . . . . . 16 4. LOADS, LOAD COMBINATIONS, AND NOMINAL STRENGTHS . . . . . . 16 4.1. Loads and Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2. Nominal Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5. STRUCTURAL DESIGN DRAWINGS AND SPECIFICATIONS, SHOP DRAWINGS, AND ERECTION DRAWINGS . . . . . . . . . . . . . . . . . . . 16 5.1. Structural Design Drawings and Specifications . . . . . . . . . . . . . . . . . . . . 17 5.2. Shop Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.3. Erection Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6. MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.1. Material Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.2. Material Properties for Determination of Required Strength of Members and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.3. Heavy Section CVN Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 7. CONNECTIONS, JOINTS, AND FASTENERS . . . . . . . . . . . . . . . . . . . . . . . . 21 7.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.2. Bolted Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7.3. Welded Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7.3a. General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7.3b. Demand Critical Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7.4. Protected Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.5. Continuity Plates and Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8. MEMBERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8.2. Classification of Sections for Local Buckling . . . . . . . . . . . . . . . . . . . . . 24 8.2a. Compact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 8.2b. Seismically Compact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd vviiii 99//88//0066 33::5599::0011 PPMM PPrroocceessss BBllaacckk 6.1–viii TABLE OF CONTENTS 8.3. Column Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 8.4. Column Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.4a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.4b. Columns Not Part of the Seismic Load Resisting System . . . . . . . . . . . . 27 8.5. Column Bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.5a. Required Axial Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.5b. Required Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 8.5c. Required Flexural Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.6. H-Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.6a. Design of H-Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.6b. Battered H-Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.6c. Tension in H-Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9. SPECIAL MOMENT FRAMES (SMF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.2. Beam-to-Column Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.2a. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.2b. Conformance Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 9.2c. Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.2d. Protected Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.3. Panel Zone of Beam-to-Column Connections (beam web parallel to column web) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.3a. Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 9.3b. Panel Zone Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.3c. Panel Zone Doubler Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.4. Beam and Column Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.4a. Width-Thickness Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.4b. Beam Flanges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.5. Continuity Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.6. Column-Beam Moment Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 9.7. Lateral Bracing at Beam-to-Column Connections . . . . . . . . . . . . . . . . . 34 9.7a. Braced Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 9.7b. Unbraced Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 9.8. Lateral Bracing of Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 9.9. Column Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 10. INTERMEDIATE MOMENT FRAMES (IMF) . . . . . . . . . . . . . . . . . . . . . . . . 36 10.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 10.2. Beam-to-Column Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 10.2a. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 10.2b. Conformance Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 10.2c. Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.2d. Protected Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.3. Panel Zone of Beam-to-Column Connections (beam web parallel to column web) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.4. Beam and Column Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd vviiiiii 99//88//0066 33::5599::0022 PPMM PPrroocceessss BBllaacckk TABLE OF CONTENTS 6.1–ix 10.4a. Width-Thickness Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.4b. Beam Flanges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.5. Continuity Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.6. Column-Beam Moment Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.7. Lateral Bracing at Beam-to-Column Connections . . . . . . . . . . . . . . . . . 38 10.8. Lateral Bracing of Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.9. Column Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 11. ORDINARY MOMENT FRAMES (OMF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 11.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 11.2. Beam-to-Column Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 11.2a. Requirements for FR Moment Connections . . . . . . . . . . . . . . . . . . . . . . . 39 11.2b. Requirements for PR Moment Connections . . . . . . . . . . . . . . . . . . . . . . . 41 11.2c. Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 11.3. Panel Zone of Beam-to-Column Connections (beam web parallel to column web) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 11.4. Beam and Column Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 11.5. Continuity Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 11.6. Column-Beam Moment Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 11.7. Lateral Bracing at Beam-to-Column Connections . . . . . . . . . . . . . . . . . . 42 11.8. Lateral Bracing of Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 11.9. Column Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 12. SPECIAL TRUSS MOMENT FRAMES (STMF) . . . . . . . . . . . . . . . . . . . . . . 42 12.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 12.2. Special Segment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 12.3. Strength of Special Segment Members . . . . . . . . . . . . . . . . . . . . . . . . . . 43 12.4. Strength of Non-Special Segment Members . . . . . . . . . . . . . . . . . . . . . . 43 12.5. Width-Thickness Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 12.6. Lateral Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 13. SPECIAL CONCENTRICALLY BRACED FRAMES (SCBF) . . . . . . . . . . . 44 13.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 13.2. Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 13.2a. Slenderness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 13.2b. Required Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 13.2c. Lateral Force Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 13.2d. Width-Thickness Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 13.2e. Built-up Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 13.3. Required Strength of Bracing Connections . . . . . . . . . . . . . . . . . . . . . . . 46 13.3a. Required Tensile Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 13.3b. Required Flexural Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 13.3c. Required Compressive Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 13.4. Special Bracing Configuration Requirements . . . . . . . . . . . . . . . . . . . . . 47 13.4a. V-Type and Inverted V-Type Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 13.4b. K-Type Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd iixx 99//88//0066 33::5599::0022 PPMM PPrroocceessss BBllaacckk 6.1–x TABLE OF CONTENTS 13.5. Column Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 13.6. Protected Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 14. ORDINARY CONCENTRICALLY BRACED FRAMES (OCBF) . . . . . . . . . 48 14.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 14.2. Bracing Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 14.3. Special Bracing Configuration Requirements . . . . . . . . . . . . . . . . . . . . . 48 14.4. Bracing Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 14.5. OCBF above Seismic Isolation Systems . . . . . . . . . . . . . . . . . . . . . . . . . 49 14.5a. Bracing Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 14.5b. K-Type Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 14.5c. V-Type and Inverted-V-Type Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 15. ECCENTRICALLY BRACED FRAMES (EBF) . . . . . . . . . . . . . . . . . . . . . . . 50 15.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 15.2. Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 15.2a. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 15.2b. Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 15.2c. Link Rotation Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 15.3. Link Stiffeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 15.4. Link-to-Column Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 15.5. Lateral Bracing of Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 15.6. Diagonal Brace and Beam Outside of Link . . . . . . . . . . . . . . . . . . . . . . . 53 15.6a. Diagonal Brace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 15.6b. Beam Outside Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 15.6c. Bracing Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 15.7. Beam-to-Column Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 15.8. Required Strength of Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 15.9. Protected Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 15.10. Demand Critical Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 16. BUCKLING-RESTRAINED BRACED FRAMES (BRBF) . . . . . . . . . . . . . . . 55 16.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 16.2. Bracing Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 16.2a. Steel Core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 16.2b. Buckling-Restraining System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 16.2c. Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 16.2d. Adjusted Brace Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 16.3. Bracing Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 16.3a. Required Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 16.3b. Gusset Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 16.4. Special Requirements Related to Bracing Configuration . . . . . . . . . . . . . 57 16.5. Beams and Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 16.5a. Width-Thickness Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 16.5b. Required Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 16.5c. Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 16.6. Protected Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1 AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC. SSeeiissmmiiccPPrroovv11..iinndddd xx 99//88//0066 33::5599::0033 PPMM PPrroocceessss BBllaacckk