A NUMERICAL INVESTIGATION OF LOCAL _ DISTORTIONA _ LATERAL _ TORSIONAL BUCKLING INTERACTION OF COLD _ FORMED STEEL LIPPED CHANNEL BEAMS

This work aims at investigating the buckling behaviour of cold-formed steel (CFS) lipped channel (LC) beams undergoing local(L)-distortional(D)-lateral-torsional (LT) buckling mode interaction for the sake of developing an analytical model to calculate the ultimate resistance to bending moment. The section geometries are identified to have nearly equal elastic local, distortional and lateral-torsional buckling moment values by performing elastic buckling analysis. The identified sections satisfy the condition for prequalified sections in AISI-S100-2007. A finite-element model has been developed and verified against the available test data for cold-formed steel lipped channel sections subjected to the major axis bending. Parametric studies were carried out to investigate the influence of geometries and yield stress values. The numerical results are compared with design predictions from the Direct Strength Method (DSM) in North American specifications for cold-formed steel structures. Based on the comparisons, design recommendations are introduced for coldformed steel lipped channel beams which experiencing local/distortional/lateral-torsional buckling mode interaction.