Optimum design of nonlinear semi-rigid steel frame based on performance-price ratio via genetic algorithm

Abstract

In this study, a two-stage structural optimization method is presented for multistory steel frames with semi-rigid connections. Based on the traditional optimization result in the first stage, the performance-price ratio (PPR) is introduced in the second stage to provide an idea to modify the unreasonable structural design that might occur in the price (or weight) only oriented optimization of first stage. The efficient advanced analysis (EAA) method accounting for the flexibility of beam-to-column connections, second-order effect, initial imperfection and plasticity development in members is applied in structural calculation, which is also used to acquire the ultimate capacity of structures. All schemes satisfying traditional optimization constraints in a simple design problem were obtained by exhaustive search. The price-performance relation of schemes showed that the structural ultimate capacity depends only on the rationality of members’ combination and has low correlation with the total cost. Design examples showed that the two-stage optimization considering PPR enables much more robust structural design at a slightly higher cost than the traditional optimum one.