Lateral Buckling Strengths of Cold-Formed Channel Section Beams

Abstract

This paper is concerned with the inelastic lateral buckling strengths of cold-formed channel section (CFC) beams. Code rules for designing steel beams against lateral buckling that are based on data for hot-rolled I-section beams may be unsuitable for CFC beams, because they have different stress-strain curves, residual stresses, and initial imperfections. Distortion may reduce the resistance of a CFC beam to lateral buckling. In addition, because of the monosymmetry of the cross section, the effective shear center moves toward the web and the effective section becomes asymmetrical after yielding, so that a CFC beam under major axis bending is subjected to minor axis bending and twisting. Also, the minor axis bending and warping strain distributions, and therefore the strengths of CFC beams, are related to the twist rotation and minor axis deflection directions. This paper deals with these problems by developing an advanced finite element model to investigate the elastic lateral-distortional buckling, inelastic behavior, and strengths of CFC beams with residual stresses and initial imperfections. The results are used to develop improved design rules for CFC beams. The effects of moment distribution and load height on the strengths are also studied.