Experimental and numerical study of cold-formed steel channels with edge-stiffened web openings, unstiffened web openings and plain webs under combined bending and shear

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This paper presents an experimental and numerical investigation into the behaviour of cold-formed steel (CFS) lipped channel sections with plain webs, unstiffened circular web openings, and edge-stiffened circular web openings subjected to combined bending and shear. A total of 24 laboratory tests and 378 validated nonlinear finite element (FE) models were used to quantify the effects of shear-span ratio, opening ratio, web slenderness, and stiffener geometry on strength and failure modes. The results show that the shear-span ratio governs the global response, controlling the transition from shear-dominated behaviour to bending-shear interaction, while web openings significantly reduce capacity under shear-dominated conditions by disrupting the diagonal load path and promoting local buckling. Edge stiffeners enhance local stability and partially restore strength, particularly for large openings and short shear spans, although their influence diminishes as global behaviour becomes dominant. Comparisons with AISI S100 indicate that the current interaction equation is conservative for plain-web sections, underestimating capacity by approximately 16%, and that it does not account for web openings. New design equations based on reduction factors are proposed for sections with unstiffened and edge-stiffened openings, with the functional form reflecting the interaction between opening-induced local instability and global bending-shear behaviour. The proposed equations are shown to satisfy target reliability requirements and provide a practical basis for the design of perforated CFS members under combined bending and shear.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.