Preface
This is the ninth edition of CSA S136, North American specification for the design of cold-formed steel structural members (NASPEC). It supersedes the previous editions published in 2012, 2007, 2001, 1994, 1989, 1984, 1974, and 1963. This edition is a harmonized Standard intended for use in Canada, the United States, and Mexico.
The NASPEC was developed jointly by CSA's Technical Committee on Cold-Formed Steel Structural Members and the American Iron and Steel Institute's Committee on Specifications. This effort was coordinated through the North American Specification Committee, which consisted of six members, three from the CSA Technical Committee and three from the AISI Committee. A detailed summary of the development of the Standard can be found in the joint preface to the North American Specification.
The North American Specification for the Design of Cold-Formed Steel Structural Members, as its name implies, is intended for use throughout Canada, Mexico, and the United States. This Specification supersedes the 2012 and previous editions of the North American Cold-Formed Steel Specification, the previous editions of the Specification for the Design of Cold-Formed Steel Structural Members published by the American Iron and Steel Institute (AISI), and the previous editions of CSA Group S136, Cold Formed Steel Structural Members, published by CSA Group.
The Specification was developed by a joint effort of the American Iron and Steel Institute Committee on Specifications, CSA Group Technical Committee on cold Formed Steel Structural Members (S136), and Camara Nacional de la Industria del Hierro y del Acero (CANACERO) in Mexico. This effort was coordinated through the North American Specification Committee, which was made up of members from the AISI Committee on Specifications and the CSA Group S136 Committee.
Since the Specification is intended for use in Canada, Mexico, and the United States, it was necessary to develop a format that would allow for requirements particular to each country. This resulted in a main document, Chapters A through M and Appendices 1 and 2, that is intended for use in all three countries, and two country-specific appendices (A and B). Appendix A is for use in both the United States and Mexico, and Appendix B is for use in Canada.
This Specification provides an integrated treatment of Allowable Strength Design (ASD), Load and Resistance Factor Design (LRFD), and Limit States Design (LSD). This is accomplished by including the appropriate resistance factors for use with LRFD and LSD and the appropriate safety factors for use with ASD. It should be noted that the use of LSD is limited to Canada and the use of ASD and LRFD is limited to the United States and Mexico.
The Specification also contains some terminology that is defined differently in Canada, the United States, and Mexico. These differences are set out in Section A1.3, Definitions. In the Specification, the terms that are specifically applicable to LSD are included in square brackets. The Specification provides well-defined procedures for the design of load-carrying cold-formed steel members in buildings, as well as other applications, provided that proper allowances are made for dynamic effects. The provisions reflect the results of continuing research to develop new and improved information on the structural behavior of cold-formed steel members. The success of these efforts is evident in the wide acceptance of the previous editions of the Specification.
The AISI and CSA Group consensus committees responsible for developing these provisions provide a balanced forum, with representatives of steel producers, fabricators, users, educators, researchers, and building code regulators. They are composed of engineers with a wide range of experience and high professional standing from throughout Canada and the United States. AISI, CSA Group, and CANACERO acknowledge the continuing dedication of the members of the specifications committees and their subcommittees. The membership of these committees follows this Preface.
The 2016 Edition of the Specification has been reorganized by incorporating the Direct Strength Method design provisions into Chapters A through M. Also, the chapters are laid out to be more in line with ANSI/AISC 360-2010. A section reference table of the 2012 Edition of the Specification and this edition is provided.
In addition to content reorganization, the following changes and additions are made in this edition:
Section A2, Referenced Specifications, Codes and Standards. All the references, including those specific to U.S. and Mexico or Canada, are listed in the main body of the Specification. All the referenced standards are updated.
Section A3.2, Other Steels. The country-specific provisions are consolidated by bringing the provisions into the main body of the Specification.
Section B2, Loads and Load Combinations. The applicable building codes for determining the loads and load combinations are introduced for the U.S., Mexico, and Canada.
Section B3, Design Basis. This section introduces three design methods: ASD and LRFD are applicable to the U.S. and Mexico, and LSD is applicable to Canada. It references Specification chapters or sections that provide design provisions for required strength [effect due to factored loads] and available strengths [factored resistances], structural members, connections, stability, structural assemblies and systems, serviceability, ponding, fatigue, and corrosion effects.
Section B4, Dimensional Limits and Considerations. The limitations for applying the Effective Width Method and the Direct Strength Method are streamlined.
Section C1, Design for System Stability. The provisions consider Appendix 2, Second-Order Analysis, included in the 2012 Edition of the Specification, and incorporate system stability analysis approaches provided in ANSI/AISC 360.
Chapters E, F and G. The provisions of the Direct Strength Method included in Appendix 1 of the 2012 Edition of the Specification are incorporated into these chapters.
Section F2.1.1, Singly- or Doubly-Symmetric Sections Bending About Symmetric Axis. Simplified Equation F2.1.1-6 to determine elastic buckling stress, Fcre, is no longer applicable to singly-symmetric C-Sections.
Section H1, Combined Axial Load and Bending. The interaction check equations for ASD, LRFD, and LSD are combined into one format, as applicable.
Section H1.2, Combined Compressive Axial Load and Bending. The interaction check equations are revised with the moment magnification effect taken into consideration through the system stability effect in accordance with Section C1.
Section I2, Floor, Roof, or Wall Steel Diaphragm Construction. AISI S310, AISI S240, and AISI S400 are introduced for diaphragm design, and the table of Safety and Resistance Factors for Diaphragms is moved to AISI S310.
Section I4, Cold-Formed Steel Light-Frame Construction. The cold-formed steel framing standards are updated.
Section I5, Special Bolted Moment Frame Systems. Special bolted moment frame systems should be designed in accordance with AISI S400.
Section I6.1, Members Strength: General Cross-Sections and System Connectivity. This section permits the bending and compression strengths of purlins and girts to be determined analytically provided the lateral, rotational, and composite stiffness provided by the deck or sheathing, bridging and bracing, and span continuity are included.
Section I7, Rack Systems. Rack system design should be in accordance with ANSI MH16.1.
Section J2, Welded Connections. The country-specific standards are brought into the main body of the Specification.
Section J3, Bolted Connections. The table of Nominal Tensile and Shear Strengths for Bolts in Appendix A has been updated to be consistent with those in ANSI/AISC 360, and values for bolt diameters less than 0.5 in. (12 mm) have been revised.
Section J7.2, Power-Actuated Fasteners (PAFs) in Concrete. The PAF pull-out strength in shear in cold-formed steel framing track-to-concrete connections is added.
Section K1, Test Standards. The AISI S900 series of test standards are introduced, and the standards are also referenced in Section A2.
Section K2, Test for Special Cases. The sentence that the provisions shall not apply to coldformed steel diaphragms was deleted.
Section K2.1.1, Load and Resistance Factor Design and Limit States Design. The table of Statistical Data for the Determination of Resistance Factor is simplified. The sentence that Section K2.1.1(b) is not applicable to floor, roof or wall steel diaphragm was deleted.
Appendix 1, Effective Width of Elements. This appendix provides provisions for determining the effective width of elements as needed for the Effective Width Method.
Appendix 2, Elastic Buckling Analysis of Members. This new appendix provides analytical and numerical approaches to determine the local, distortional, and global buckling strengths.
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S136.1-16 - Commentary on North American Specification for the Design of Cold-Formed Steel Structural Members
Preface
This document provides a commentary on the 2016 edition of the North American Specification for the Design of Cold-Formed Steel Structural Members.
The purpose of the Commentary is: (a) to provide a record of the reasoning behind, and justification for, the various provisions of the North American Specification by cross-referencing the published supporting research data, and to discuss the changes made in the current Specification; (b) to offer a brief but coherent presentation of the characteristics and performance of cold-formed steel structures to structural engineers and other interested individuals; (c) to furnish the background material for a study of cold-formed steel design methods to educators and students; and (d) to provide the needed information to those who will be responsible for future revisions of the Specification. The readers who wish to have more complete information, or who may have questions which are not answered by the abbreviated presentation of this Commentary, should refer to the original research publications.
Consistent with the Specification, the Commentary contains a main document, Chapters A through M, Appendices 1 and 2, and the country-specific provisions Appendices A and B.
AISI appreciates the tremendous efforts of the committee members in reorganizing the whole Specification and the Commentary. Special thanks go to Mr. Richard Kaehler, who developed the outline; and Dr. Benjamin Schafer, who provided leadership in reorganizing the Specification and Commentary. Appreciation is extended to Chairman Roger Brockenbrough and Vice Chairman Richard Haws for their lasting contributions to the AISI Committee of Specifications.
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