High-strength cold-formed thin-walled steel sections have been widely used in the recent several years. However, distortional buckling or interaction between it and local buckling can occur for high strength cold-formed thin-walled steel members. This paper describes a series of compression tests performed on lipped channel section columns with V-shape intermediate stiffener in the web and flanges fabricated from cold-formed high strength steel of thickness 0.48 and 0.6mm with nominal yield stress 550MPa. The lipped channel sections were tested to failure with both ends of the columns fixed. The test results of 16 specimens show that the local buckling usually appears before distortional buckling of the specimens and it makes the distortional buckling occur in advance. This interaction of local and distortional buckling may have the effect of reducing the stiffness and bearing capacity of the columns. The comparison on ultimate strength and buckling mode between test results and results of finite element analysis considering geometric and material nonlinear show that finite element method (FEM) can simulate the distortional buckling of cold-formed steel channel columns effectively. The calculative results using Direct Strength Method (DSM) of the Norm American Specification show that this design method couldn't consider the reverse effect of interaction between local and distortional buckling on ultimate strength. Direct Strength Method (DSM) considering interaction between local and distortional buckling should be developed.
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