DISTORTIONAL BUCKLING BEHAVIOR OF HIGH STRENGTH COLD-FORMED STEEL COLUMNS SUBJECTED TO AXIAL COMPRESSION

550 MPa high strength cold-formed steel lipped channel column under axial compression loading has three modes(O-O,O-I,I-I) when distortional buckling occur.The distortional buckling behavior of three different modes has been analyzed by finite element method(FEM) which consider geometric and material non-linear,including load carrying capacity,deformation,stress of distortional buckling,stress distribution of cross-section.Analysis results show that behavior of different distortional buckling modes has a greater different in many respects.At the same time distortional buckling is different from local buckling and overall buckling in some behaviors.The direct strength method(DSM) has been used to predict the ultimate load capacity of distortional buckling.The comparison between test results and analysis results shows that result calculated by the direct strength method is close and conservative to test results.So the direct strength method has been suggested to calculate distortional buckling ultimate load capacity of channel columns under axial compression.