Design of general cold-formed steel shapes

M.E. University of Kansas, Civil Engineering 1988The structural design or cold-formed steel members is a complex process. In addition to limiting the stresses to those allowed by the material, other modes or failure must be considered. Typically, cold-formed steel shapes are made from relatively thin material, and therefore are subject to local buckling. Also, since these shapes normally have an open cross-section, torsional buckling may control. The American Iron and Steel Institute recently released the 1986 Edition or the Cold-Formed Steel Design Manual. This latest edition presented some changes to the design procedure requiring a large amount or mathematical computations. First, the cross-sectional properties must be determined, including shear center and torsional warping constant. Then, the capacity or the member is computed using a new "unified" design approach. Since parts or a cross-section are subject to local buckling under compressive load, a portion of each element may be deemed ineffective, thereby reducing the effective cross-section. The design procedure is therefore iterative. This report presents the development of a software package for the design or general cold-formed steel shapes. The program, called CFS, is an efficient interactive system to assist the design engineer. Any general cold-formed steel shape may be defined, including composites of more than one shape. Concurrent graphical representation assists the user in verifying correct input. Extensive flexibility is provided for modifying the shape definition. Properties of the cross-section are computed. Allowable capacities are determined based on input boundary conditions. Load combinations are analyzed and the resulting effective properties are determined