Load and resistance factor design of cold-formed steel: Calibration of the AISI design provisions

In the design of steel buildings, the "Allowable Stress Criteria" have long been used for the design of cold-formed steel structural members in the United States and other countries.' In view of the fact that the mathematical theory of probability, which has been so successfully applied in other fields of engineering, would seem to be equally applicable to cold-formed steel design by providing a more uniform degree of structural safety, the "Limit State Design" method based on the probabilistic concept has been used in Canada and Europe for the design of cold-formed steel structural members.' In the United States, a research project on "Load and Resistance Factor Design of Gold-Formed Steel Members" was condudted by Rang, Supornsilaphachai, Snyder, Pan, Galambos, and Yu during the period from 1979 through 1985. The tentative load and resistance factor design (LRFD) criteria for cold-formed structural members were proposed in the Seventh Progress Report' on the basis of the 1980 Edition of the AISI allowable stress design specification." In 1986, a major revision was made in the AISI Specification to reflect the results of recent research projects and improvements in design techniques." Consequently, the tentative LRFD criteria proposed in the Seventh Progress Report were revised in 1987. This progress report contains the calibrations of the AISI design provisions included in the 1986 Specification. The procedures used for calibration are summarized in Article II. Articles Ill through XI deal with (a) bending strength, (b) web crippling of beams, (c) combined bending and web crippling, (d) concentrically loaded compression members, (e) combined axial load and bending, (f) welded connections, (g) bolted connections, (h) stiffeners, and (i) wall studs and wall stud assemblies. The results of these calibrations will be used in the revision of the proposed LRFD Specification for cold-formed steel structural members.