North American Specification for the Design of Cold-Formed Steel Members

by Jose Antonio Gomez Urquiza

The First Edition of the general specification for the design of cold-formed steel members, an American National Standards Institute-approved American National Standard, will soon be published through the collaboration of the American Iron and Steel Institute (AISI), the Canadian Standards Association (CSA), and the Camara Nacional de la Industria del Hierro y del Acero (CANACERO).

Benefits

This new standard will help remove regulatory barriers so steel products manufacturers can increase productivity and will no longer have to re-engineer their products and systems to meet the different standards of each country. At the same time, new technologies will be introduced more quickly, which will contribute to the opening of attractive markets and the development of opportunities for cold-formed steel framing in North America.

The type of steel members specified in this standard has a wide range of applications in construction such as ceilings, walls, floors, and decks. Cold-formed steel members have application in electric towers and as lateral protections in highways and rigid supports in bridges. They are also used in residential construction and in the industrial and agricultural sectors.

Background

The manufacturing of cold-formed steel members began in the United States in the 1930s, and in early 1942 the American Iron and Steel Institute published its Light Gage Cold-Formed Steel Design Manual, which was introduced in Mexico when Fundidora Monterrey opened this market in the '60s. A translated version of this book was published in March of 1965, and in 1969 the Engineering Institute of the National University of Mexico published an experimental and theoretical study on the structural behavior of cold-formed steel members. And although there were some technical standards and regulations available at that time, expert information was not enough.

Mexico did not make much progress on this matter until 1995 when, within the framework of the North American Free Trade Agreement, the first technical meetings and cooperative efforts took place between the three countries toward the great goal of developing a common standard for the design of cold-formed steel members. Participants were the AISI Committee on Specifications for the Design of Cold-Formed Steel Structural Members, the CSA Technical Committee on Cold-Formed Steel Structural Members, and CANACERO in Mexico.

The tri-national standard proposes the design and technical criteria that will help engineers and builders in the three countries better and more easily use cold-formed steel members. It provides an integrated treatment of load and resistance factor design (LRFD), limit states design (LSD), and allowable strength design (ASD). This is accomplished by including the appropriate resistance factors for use with LRFD and LSD and the appropriate factors of safety for use with ASD. Equivalent LSD terminology is shown in brackets throughout the specification.

Three systems of units are used — U.S. customary (inch-pound), SI (Newton, mm), and MKS (kg, cm), which is used in Mexico.

The specification consists of a basic document, Chapters A through G, which is intended for use in all three countries. Three country-specific appendices, A through C, are included. The appendices cover broad topics, such as provisions for the design method to be used and the reference source for loads and load combinations.

The appendices also include country-specific technical provisions, where full agreement between the three countries could not be reached, since each one has its own safety, load and resistance requirements with regard to particular conditions such as low temperatures, snow and hail in Canada; earthquakes in Mexico; and winds, storms and tornados in the United States.

Once the final specification has been agreed upon and written in English it will then be published in French and Spanish.

Copyright 2003, ASTM