Optimal design of cold-formed steel lipped channel beams: Combined bending, shear, and web crippling

The load carrying capacity of cold-formed steel (CFS) beams can be enhanced by employing optimisation techniques. Recent research studies have mainly focused on optimising the bending capacity of the CFS beams for a given amount of material. However, to the best of authors’ knowledge, very limited research has been performed to optimise the CFS beams subject to shear and web crippling actions for a given amount of material. This paper presents the optimisation of CFS lipped channel beams for maximum bending, shear, and web crippling actions combined, leading to a novel conceptual development. The bending, shear and web crippling strengths of the sections were determined based on the provisions in Eurocode 3, while the optimisation process was performed by the means of Particle Swarm Optimisation (PSO) method. Combined theoretical and manufacturing constraints were imposed during the optimisation to ensure the practicality of optimised CFS beams. Non-linear Finite Element (FE) analysis with imperfections was employed to simulate the structural behaviour of optimised CFS lipped channel beams after successful validation against previous experimental results. The results demonstrated that, the optimised CFS sections are more effective (bending, shear, and web crippling actions resulted in 30%, 6%, and 13% of capacity increase, respectively) compared to the conventional CFS sections with same amount of material (weight). The proposed optimisation framework can be used to enhance the structural efficiency of CFS lipped channel beams under combined bending, shear, and web crippling actions.