Local–distortional–global interaction in lipped channel columns: Experimental results, numerical simulations and design considerations

This work aims at contributing towards understanding the structural response and predicting the ultimate strength of cold-formed steel lipped channel columns affected by local–distortional–global (LDG) interaction. Initially, the most relevant aspects concerning the buckling and elastic–plastic post-buckling behaviours of fixed-ended lipped channel columns with nearly coincident local, distortional and global (flexural–torsional) buckling loads are briefly addressed. Then, the paper (i) summarises the most important test results obtained in a recently reported experimental investigation carried out at the Federal University of Rio de Janeiro, (ii) addresses their numerical simulation by means of Abaqus shell finite element analyses (SFEA) and (iii) presents the outcome of a fairly extensive numerical parametric study performed to obtain ultimate strength data concerning fixed-ended lipped channel columns experiencing LDG interaction. Finally, the ultimate strength “data bank” gathered, consisting of 12 experimental and 134 values, are used as the starting point to assess the performance (accuracy and safety) of design approaches, based on the currently available Direct Strength Method (DSM) strength curves and intended to estimate the failure loads of cold-formed steel lipped channel columns affected by the triple mode interaction under consideration.

► Behaviour/strength of lipped channel columns affected by local–distortional–global interaction.
► Experimental results, numerical simulations and Direct Strength Method design considerations.
► Experimental/numerical evidence of distortional–global interaction and strength erosion.
► Fairly extensive experimental and numerical column ultimate strength data bank gathered.
► Performance assessment of available DSM design approaches, some accounting for mode interaction.