This paper reports the results of an ongoing investigation on the use of the Direct Strength Method (DSM) to estimate the ultimate strength of lipped channel cold-formed steel columns and beams affected by interaction phenomena involving local-plate and distortion buckling modes. Initially, one briefly presents the DSM approaches to perform the safety checking of columns and beams against local-plate and distortion failures, and some attention is also paid to a recently proposed extension aimed at taking into account the above buckling mode interaction. Next, one describes the results of a parametric study, carried out by means of the code Abaqus, to determine the "exact" ultimate strengths of 108 columns and 90 beams displaying various geoemetries (cross-section dimensions and lengths), all selected to ensure the occurrence of relevant mode interaction effects. Then, this ultimate strength data is compared with the estimates provided by the existing DSM equations and, on the basis of the conclusions drawn from this comparison, one identifies some features that must necessarily be included in a novel DSM approach aimed at taking adequately into account the influence of the local-plate/distortion buckling mode interaction phenomena.
Cold-formed steel profiles; Lipped channel columns; Lipped channel beams; Local-plate; Shell finite element analysis; Direct Strength Method
