Optimum design of nonlinear steel frames with semi-rigid connections using a genetic algorithm

Abstract The realistic modeling of beam-to-column connections plays an important role in the analysis and design of steel frames. A genetic algorithm based optimum design method is presented for nonlinear multistorey steel frames with semi-rigid connections. The design algorithm obtains a frame with the least weight by selecting appropriate sections from a standard set of steel sections such as wide flange sections of AISC or universal sections of British standard. The algorithm accounts for the serviceability and strength constraints as specified in BS5950. A nonlinear empirical model is used to include the moment–rotation relation of beam-to-column connections. Furthermore, the P – Δ effect is also accounted for in the analysis and design of the multistorey frame. The effective length factors for columns which are flexibly connected to beams are obtained from the solution of the nonlinear interaction equation. A number of frames with end plate without column stiffeners are designed to demonstrate the efficiency of the algorithm.

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