On the distortional post-buckling behaviour of cold-formed lipped channel steel beams

This paper presents and discusses the results of an investigation on the elastic distortional post-buckling behaviour of cold-formed lipped channel steel beams (members subjected to pure bending). Such results, obtained from spline finite strip analyses accounting for initial geometrical imperfections (critical buckling mode shape), consist of (i) equilibrium paths and (ii) curves describing the post-buckling evolution of the relevant (ii(1)) displacement and stress longitudinal profiles and (ii(2)) cross-section stress distributions. In particular, a non negligible post-buckling asymmetry, with respect to the cross-section distortion sign, is revealed and shown to stem from differences in the flange-stiffener warping behaviour. The results presented also concern the influence of the local end support conditions on the beam distortional post-buckling behaviour (stiffness and strength). Such end conditions involve the restraint to (i) the end section warping and/or to (ii) the flexural rotation of the wall element transverse edges.