Simple Weight-Optimization Scheme for Steel Frames

Weight-optimization studies of steel frames are executed as iterative fully stressed designs of models consisting of axial force bars and quadrilateral shear panels. The bars represent the flanges and the shear panels the web of the actual structural steel member. The stiffness characteristics of the shear panels are derived from the principle of minimum complementary energy, assuming constant shearing stress in the interior and linear boundary displacements. Minimum and maximum cross-sectional properties, in addition to allowable stresses, are used as constraints. Elastic-plastic shear buckling of the web is controlled by checking against the provisions of the steel design code and overall stability by an iterative consideration of equilibrium on the deformed structure. A four-bay two-story framework with a crane rail is optimized to demonstrate the utility in a typical industrial structural design problem.