Local and Distortional Interaction Buckling of Cold-formed Thin-Walled High Strength Lipped Channel Columns

In this paper, a series of axial compression tests were conducted on lipped channel columns constructed from cold-formed high strength Grade G550 steel sheet of thickness of 1 mm in order to investigate the local and distortional interaction buckling performance. The failure modes, ultimate loads and load–displacement curves of the specimens were reported and analyzed. The experiment revealed the deformation mechanism of specimens failing in local-distortional interaction or distortional mode. Besides, a finite element model was developed to predict the buckling performance of the specimens. The effect of different imperfection shapes and material models on numerical results was investigated so that the reasonable finite element analysis can be carried out. It was found that the local buckling mode with an odd number of waves as the initial imperfection can produce practical deformation process. Meanwhile, the material model of Ramberg–Osgood can be applied for the nonlinear finite element analysis of the specimens. The parametric analysis was also performed to study the relationship between the sensitivity of specimens to local and distortional imperfections as well as the variation of bearing capacity with the geometric size. It was found that the lip width has great influence on the bearing capacity of specimens because of the significant restriction of lip on distortional deformation.