Optimum designs are found for elastoplastic trusses subjected to multiple loading conditions including cyclic loads. A new formulation is presented for the optimization problem under stress and strain constraints, and the optimal solutions are found by using a gradient-based optimization algorithm. The sensitivity coefficients of the responses with respect to the design varibles are found by using the author's incremental method of design sensitivity analysis. It is shown for the case of simultaneous yielding that the yield condition of only one yielded member may be used for updating the sensitivity coefficients. Optimum designs are found for symmetric trusses under constraints on strains and stresses, and the effects of loading conditions and the admissible strain levels on the optimum design are discussed.
