Minimum Weight Design of Light Gage Steel Members

Light gage steel is used extensively in light construction components. Large tonnages of a standard design are commonly produced, thus the minimum material requirements are of utmost importance to the product designer. A technique is presented for designing a minimum weight member to support a given loading condition. The problem is treated as a numerical optimization problem in which the variables are the dimensions and thickness of a given type of cross-sectional shape. Design requirements are based on the American Iron and Steel Institute Specification for the Design of Cold-Formed Steel Structural Members, 1968 Edition. These requirements are used to calculate a minimum acceptable thickness for a section whose other dimensions are considered temporarily fixed. This establishes the minimum weight design for the particular set of dimensions. Search methods are then employed to systematically establish sets of dimensions yielding reduced weight sections. Both a direct search and gradient search were examined and the latter found to be more efficient.