L-D-G Interaction in CFS Lipped Channel Columns – Part II: Numerical Simulations and Design Considerations

Abstract

This paper deals with the structural behaviour, ultimate strength and design of fixed-ended cold-formed steel (CFS) lipped channel columns experiencing various levels of local-distortional-global buckling mode interaction (more or less close critical local, distortional and global loads). First, a comparison between experimental results, obtained from two tests carried out at The University of Hong Kong (UHK), and the corresponding shell numerical simulations are presented and discussed - the UHK test campaign is reported in Part I of this two-part paper. The comparison (i) involves equilibrium paths, deformed configurations, failure loads and collapse mechanisms, and (ii) provides enough evidence to ensure that the numerical model developed may be deemed validated. Then, this numerical model is employed to perform a parametric study, aimed at obtaining numerical failure load data concerning lipped channel columns experiencing different levels of local-distortional-global interaction - 68 fixed-ended columns, exhibiting the same geometries of the specimens tested at UHK and various yield stresses, thus covering a wider slenderness range. Finally, this Part II paper uses the experimental failure loads reported in Part I and the numerical failure load data obtained in this work and collected from the literature to assess the quality of the ultimate strength estimates provided by various design approaches, based on the direct strength method (DSM), for cold-formed steel columns affected by the triple coupling phenomenon under consideration.