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 restraint). 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 (i) the local (McrL) and distortional (McrD) critical buckling moment (0.50 <= M-crD/M-crL <= 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), (ii) ultimate strength and (iii) failure modes 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.