Investigation on the Stability Behaviour of Cold-Formed Steel Beam-Column Members under Biaxial Bending

This paper presents the experimental and numerical investigation on the cold-formed steel beam-column member under bi-axial loading. In this study, the lipped channel cross section of member height 1600 mm and 750 mm are considered to study the cross-sectional and global buckling effects on the strength of the member. The experiments are conducted by applying an eccentric compression to create axial load and moment gradient. Carefully designed experiments are carried out so that member will be subjected to uniform and non-uniform moments throughout the member. The influence of the varying moment on the various buckling behavior is examined. The use of moment correction factor (Cb) in the case of FTB and distortional buckling is analyzed. The study reveals the influence of axial force in the calculation of moment amplification factor (Cm). The study is extended to the finite element analysis using ABAQUS, which are validated with the experimental results. The numerical model is extended to study the behavior of a spectrum of axial and bending combinations. The results from the experiment and numerical model are compared with the code specification AISI S100-16, Linear interaction (LI) framework and the non-linear interaction (NLI) framework based on direct strength method (DSM). The results show that LI framework predicts strength conservatively by 30 to 50% for biaxial bending. The study shows the need for the modification in the DSM NLI framework prediction for beam-column member subjected to non-uniform moment.

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