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

The realistic modeling of beam-to-column connections plays an important rol e in the analysis and design of steel frames, A genetic algorithm based opt imum design method is presented for nonlinear multistorey steel frames with semi-rigid connections. The design algorithm obtains a frame with the leas t weight by selecting appropriate sections from a standard set of steel sec tions such as wide flange sections of AISC or universal sections of British standard. The algorithm accounts for the serviceability and strength const raints as specified in BS5950. A nonlinear empirical model is used to inclu de the moment-rotation relation of beam-to-column connections. Furthermore, the P-Delta effect is also accounted for in the analysis and design of the multistorey frame. The effective length factors for columns which are flex ibly connected to beams are obtained from the solution of the nonlinear int eraction equation. A number of frames with end plate without column stiffen ers are designed to demonstrate the efficiency of the algorithm. (C) 2001 C ivil-Comp Ltd. and Elsevier Science Ltd. All rights reserved.