Shape optimisation of cold-formed steel profiles with manufacturing constraints – Part I: Algorithm

Abstract

This paper presents a Genetic Algorithm optimisation method with manufacturing constraints for shape optimisation of cold-formed steel (CFS) profiles. Previous studies on unconstrained shape optimisation of CFS crosssections, where the sole aim was to optimise the weight-to-capacity ratio of the profiles, yielded cross-sections that cannot be manufactured. Current coldforming processes, such as roll-forming and brake-pressing, have limited ability to form continuously curved surfaces without discrete bends. This paper defines simple manufacturing rules and introduces them into the evolutionary algorithm. Augmented Lagrangian constraint-handling technique, with equality and inequality constrained violations, is used to avoid ill-conditioned problems. The ability and accuracy of the algorithm to handle the defined manufacturing constraints are verified by implementing it to optimise the section capacity of bisymmetric closed thin-walled profiles, for which an analytical solution is known.