Post-buckling behavior and DSM design of cold-formed steel lipped channel columns experiencing local-distortional-global interaction

Abstract

This paper describes experimental research investigating the structural behaviors, failure modes, and ultimate load-carrying capacities of fixed-ended cold-formed steel lipped channel columns eroded by local-distortional-global (L-D-G) buckling interaction under axial compression. Initially, a brief introduction on the selection of column geometry, which was based on the closeness between three elastic critical buckling stresses named elastic local, distortional, and global critical buckling stresses, was reported. In addition, detailed works involving measuring member geometries and initial geometrical imperfections, test set-up, and the arrangements of strain gauges and displacement transducers are described. Moreover, experimental investigation results of 33 cold-formed steel columns are discussed including deformed configurations, applied load vs. strains curves, applied load vs. displacement curves, failure modes, and ultimate load-carrying capacities. The tests demonstrated D-G interaction with no obvious local deformation observed even though the elastic critical loads of L, D, and G for the selected specimens are close. The results clearly demonstrate that the occurrence of D-G buckling interaction eroded the ultimate strengths of columns. Current DSM predictions are evaluated using experimental data of cold-formed steel columns related to the D-G buckling interaction. Furthermore, a design criterion based on DSM is proposed to identify cold-formed steel columns eroded by D-G buckling interaction and predict the ultimate strength, which is evaluated by all available experimental data collected from related literature.