Local-distortional interaction in cold-formed steel beams: Behaviour, strength and DSM design

This work presents and discusses numerical results concerning cold-formed steel simply supported beams subjected to uniform bending and exhibiting (i) three cross-section shapes (lipped channels, zed-sections and hat-sections), and (ii) two end support conditions (differing in the warping and local displacement/rotation restraints, which are either free or fully prevented). A systematic numerical investigation is carried out, in order to characterise the post-buckling behaviour and ultimate strength of beams experiencing more or less severe L-D interaction effects. 43 geometries and 11 yield stresses are considered for each combination of cross-section shape and support conditions, thus ensuring distinct (i) ratios between the local (McrL) and distortional (McrD) critical buckling moments (0.50 ≤ McrD /McrL ≤ 2.00), and (ii) local or distortional slenderness values, ranging from 0.50 to 3.50. The numerical results are obtained through Abaqus shell finite element analyses and concern the (i) post-buckling behaviour (elastic and elastic-plastic), ultimate strength and failure mechanisms of beams previously selected to undergo considerable L-D interaction. Based on the acquired information, a first contribution towards the Direct Strength Method (DSM) design of cold-formed steel beams undergoing different “levels” of L-D interaction is presented and discussed.