1. 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
3. 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.
4. 6.1–iv PREFACE
• Clarifying that the scope of structures covered includes “building-like nonbuilding
structures.”
• Clarifying that all steel buildings designed with an R factor greater than 3 must comply
with the Provisions.
• Adding new requirements to delineate the expectations for structural design drawings
and specifications, shop drawings and erection drawings.
• Adding new ASTM material specifications that are commonly used in the metal building
industry.
• Adding Rt values for all materials to be used in determining susceptibility of connections
to fracture limit states.
• Relaxing the limitations on use of oversized holes in bolted joints.
• 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.
• 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.
• Expanding the applicability of requirements on splices in columns that are part of the
seismic load resisting system in moment frames to all systems.
• Improving the provisions related to the design of column bases.
• Making the stability bracing requirements more consistent throughout the document.
• 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.
• Decreasing the column splice shear capacity requirements for SMF systems.
• Increasing the stability bracing requirements for IMF systems.
• Clarifying that connections meeting the requirements for SMF or IMF systems are also
acceptable for OMF applications.
• Increasing the requirements on SCBF systems that employ braces with high Kl/r ratios.
• Reducing the connection force demand on OCBF bracing to allow the use of the
amplified seismic load.
• 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.
• Adding specific requirements for OCBF above seismic isolation systems.
• Significantly improving the provisions related to quality assurance and quality control
to address many of the issues identified in FEMA 353.
• 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.
5. 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.
6. 6.1–vi
Seismic Provisions for Structural Steel Buildings, March 9, 2005, incl. Supplement No. 1
AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC.