Cold-formed members for most application are designed in accordance with the Specification for the Design of Cold-Formed Steel Structural Members, American Iron and Steel Institute, Washington, DC. Generally referred to as the AISI Specification, it applies to members coldformed to shape from carbon or low-alloy steel sheet, strip, plate, or bar, not more than 1- in thick, used for load carrying purposes in buildings. With appropriate allowances, it can be used for other applications as well. The vast majority of applications are in a thickness range from about 0.014 to 0.25 in.
The design information presented in this section is based on the AISI Specification and its Commentary, including revisions being processed. The design equations are written in dimensionless form, except as noted, so that any consistent system of units can be used. A synopsis of key design provisions is given in this section, but reference should be made to the complete specification and commentary for a more complete understanding.
The AISI Specification lists all of the sheet and strip materials included in Table 1.6 (Art. 1.4) as applicable steels, as well several of the plate steels included in Table 1 (A36, A242, A588, and A572). A283 and A529 plate steels are also included, as well as A500 structural tubing (Table 1.7). Other steels can be used for structural members if they meet the ductility requirements. The basic requirement is a ratio of tensile strength to yield stress not less than 1.08 and a total elongation of at least 10% in 2 in. If these requirements cannot be met, alternative criteria related to local elongation may be applicable. In addition, certain steels that do not meet the criteria, such as Grade 80 of A653 or Grade E of A611, can be used for multiple-web configurations (roofing, siding, decking, etc.) provided the yield stress is taken as 75% of the specified minimum (or 60 ksi or 414 MPa, if less) and the tensile stress is taken as 75% of the specified minimum (or 62 ksi or 428 MPa if less). Some exceptions apply. Suitability can also be established by structural tests.