Abstract
This paper presents a unified and efficient new optimum design method for nonlinear plane frame structures with box sections. The material nonlinear structural analysis problem is formulated as the total complementary energy minimization problem, and the necessary conditions for analysis problem are derived. Then the primary optimum design problem is reformulated considering both the primary design constraints and the necessary conditions for the analysis problem. In the reformulated optimum design problem the structural behaviors are also dealt with as the design variables. The reformulated optimum design problem is solved efficiently by using the gradient projection method. In the optimization process, the complementary energy sensitivities with respect to primary design variables at each member element is used, however the calculation of behavior sensitivity with respect to primary design variables is not necessary. The rigorousness, efficiency and reliability of the proposed method are demonstrated by comparing the results obtained by the dual method in which the behavior sensitivities are used.
