Experimental investigation of cold-formed thin-walled lipped channel steel columns experiencing local-distortional interactive buckling under axial compression

This paper describes a series of compression tests conducted on lipped channels with stiffened-web fabricated from mild steel plate of thickness 1.5 mm with nominal strength Grade Q345. A total of 18 channel specimens including two cross-section dimensions with three different column lengths were tested to failure with both ends of the column fixed, in order to determine the structural behavior and ultimate strength of cold-formed thin-walled steel columns experiencing post-buckling mode interaction between local and distortional buckling, due to the closeness of the critical buckling stresses. Test results consist of the column geometries, material properties, initial geometrical imperfections, non-linear equilibrium paths, deformed configuration, collapse modes and ultimate strength values. The results indicate that the column specimens undergoing interaction between local buckling and distortional displayed a significant post-buckling strength reserve. Moreover, the adverse interaction of local and distortional buckling reduced significantly the ultimate strength of the column specimen. Most of all, the post-local buckling interaction with distortional buckling (L+D) and the post-distortional buckling interaction with local buckling (D+L) have different effects on structural behavior, collapse mechanism, and failure load. Besides, the tested specimens were simulated by means of finite element program ABAQUS. Results from the analysis agree well with the experimental data.