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Cold Formed Steel
Cold-formed steel members have been used in buildings, bridges, storage racks, grain bins, car bodies, railway coaches, highway products, transmission towers, transmission poles, drainage facilities, various types of equipment and others (Yu, 2000). These types of sections are cold-formed from steel sheet, strip, plate, or flat bar in roll-forming machines or by press brake or bending operations. The material thicknesses for such thin-walled steel members usually range from 0.0147 in. (0.373 mm) to about ¼ in. (6.35 mm). Steel plates and bars as thick as 1 in. (25.4 mm) can also be cold-formed successfully into structural shapes (AISI, 2007b).

History of AISI Specifications
The use of cold-formed steel members in building construction began in the 1850s. In the United States, the first edition of the Specification for the Design of Light Gage Steel Structural Members was published by the American Iron and Steel Institute (AISI) in 1946 (AISI, 1946). This first Allowable Stress Design (ASD) Specification was based on the research work sponsored by AISI at Cornell University under the direction of late Professor George Winter since 1939 (Winter, 1959). It was revised subsequently in 1956, 1960, 1962, 1968, 1980, and 1986 to reflect the technical developments and the results of continued research at Cornell and other universities (Yu et al., 1996). In 1991, AISI published the first edition of the Load and Resistance Factor Design Specification developed at University of Missouri of Rolla and Washington University under the directions of Wei-Wen Yu and Theodore V. Galambos (AISI, 1991). Both ASD and LRFD Specifications were combined into a single specification in 1996 (AISI, 1996).

In 2001, the first edition of the North American Specification for the Design of Cold-Formed Steel Structural Members was developed by a joint effort of the AISI Committee on Specifications, the Canadian Standards Association (CSA) Technical Committee on Cold-Formed Steel Structural Members, and Camara Nacional de la Industria del Hierro y del Acero (CANACERO) in Mexico (AISI, 2001). It included the ASD and LRFD methods for the United States and Mexico together with the Limit States Design (LSD) method for Canada. This North American Specification has been accredited by the American National Standard Institute (ANSI) as an ANSI Standard to supersede the 1996 AISI Specification and the 1994 CSA Standard. Following the successfully use of the 2001 edition of the North American Specification for six years, it was revised and expanded in 2007 (2007a). This updated specification includes new and revised design provisions with the additions of the Direct Strength Method in Appendix 1 and the Second-Order Analysis of structural systems in Appendix 2.

In addition to the AISI specifications, the American Iron and Steel Institute has also published commentaries on various editions of the specifications, design manuals, framing design standards, various design guides, and design aids for using cold-formed steel. For details, see AISI website at www.steel.org.

REFERENCES

American Iron and Steel Institute (1946), Specification for the Design of Light Gage Steel Structural Members, New York, NY, 1946.

American Iron and Steel Institute (1991), Load and Resistance Factor Design Specification for Cold-Formed Steel Structural Members, Washington, DC, 1991.

American Iron and Steel Institute (1996), Specification for the Design of Cold-Formed Steel Structural Members, Washington, DC, 1996.

American Iron and Steel Institute (2001), North American Specification for the Design of Cold-Formed Steel Structural Members, Washington, DC, 2001.

American Iron and Steel Institute (2007a), North American Specification for the Design of Cold-Formed Steel Structural Members, Washington, DC, 2007.

American Iron and Steel Institute (2007b), Commentary on North American Specification for the Design of Cold-Formed Steel Structural Members, Washington, DC, 2007.

Winter, G. (1959), “Cold-Formed, Light Gage Steel Construction,” Journal of the Structural Division, ASCE, Vol. 85, No. ST9, November 1959.

Yu, W.W., D.S. Wolford, and A.L. Johnson (1996), “Golden Anniversary of the AISI Specification,” Proceedings of the 13th International Specialty Conference on Cold-Formed Steel Structures, St. Louis, MO, 1996.

Yu, W.W. (2000), Cold-Formed Steel Design, 3rd Edition, John Wiley & Sons, New York, NY, 2000.