Optimum design of geometrically non-linear elastic–plastic steel frames via genetic algorithm

In this article, a genetic algorithm (GA) is presented for the optimum design of geometrically non-linear elastic–plastic steel frames with discrete design variables. Design variables are selected from practically available sets of standard steel sections. Relatively large displacement restrictions are considered in the optimum designs. The simple GA used here utilizes reproduction, crossover and mutation operators. The algorithm requires a large number of non-linear analyses of frames. The analyses cover geometric non-linearities and, elastic–plastic effects of the material as well. An incremental load approach with a Newton–Raphson type of iteration is used in the analyses of the frames. The application of the algorithm is shown by a number of design examples. The designs obtained for non-linear elastic–plastic frames are compared to those where linear–elastic behaviour is assumed.