A TWO-PHASE OPTIMIZATION METHOD FOR MINIMUM-WEIGHT DESIGN OF TRUSSES

In this paper, a new twp-stage procedure for the minimum weight design of trusses is proposed. In the first stage (behavior phase) of optimization the behavior variables (joint displacements) are chosen as basic unknowns and the optimum displacement state of the truss or its searched region is found by using a maximum total strain energy criterion with linear programming. In the second stage (structural phase) the design variables (cross-section areas) are chosen as basic unknowns and the minimum weight design of the truss is obtained by using another linear program or a direct search technique. This method is effective for the minimum weight design of truss type structures with stress, displacement and geometric constraints. In most cases it can avoid the need for repeated iterations and structural reanalyses. Moreover, a minimum-maximum total strain energy criterion to select the optimal layout of structures is presented in this paper.