Optimum plastic design of unbraced frames of irregular configuration (Q1081399)

An efficient algorithm is developed for optimum plastic design of low- rise unbraced frames of general configuration. The algorithm is based on the static approach of limit analysis without generating the independent mechanisms. Three equations of equilibrium are written at each joint of the frame to form the equality constraints. To increase the efficiency of the linear programming formulation, a revised simplex method is employed in which the inverse of the basis is represented as a product of elementary matrices. The elementary matrices are actually saved as column matrices to save storage in the microcomputer. Therefore, this approach is more efficient in terms of speed and storage. Based on the algorithm presented, a microcomputer program is developed for optimum plastic design of low-rise frames of arbitrary configuration on an IBM personal computer. The objective of such an optimal design is to find plastic moment capacities of the frame elements that minimize the weight of the structure. Three examples are presented in order to show the practicality of the optimum plastic design of frames on available microcomputers.