Lateral Buckling Tests on Cold-Formed Channel Beams

Abstract

This paper is concerned with the lateral buckling capacities of cold-formed lipped channel-section beams (CFCs). It is argued that design code formulations based on those for hot-rolled I-beams may be inappropriate for CFCs, because of the very different cross-sectional shapes and methods of manufacture, and that there is a need for test data on the lateral buckling capacities of CFCs. The paper describes a series of 10 lateral buckling tests on simply supported unbraced CFCs of two different cross sections, and a series of subsidiary tests, including tension tests, a stub-column test, section moment capacity tests, torsion tests, residual stress measurements, and measurements of initial crookedness and twist. The lateral buckling test results showed that the CFCs failed catastrophically by local or distortional buckling of the most compressed element of the cross section after quite large deformations. The failure moments were lower when a beam lateral deflection increased the compression in the compression lip, and higher when they increased the compression in the flange-web junction. The lateral buckling results showed good agreement with theoretical predictions. The lateral buckling results were also compared with design codes AS 4100 for hot-rolled sections and AS/NZS 4600 for cold-formed sections. It was found that the predictions by AS 4100 were generally closer to the test results while the predictions by AS 4600 were too high for beams with thinner wall thickness, but too low for beams with thicker wall thickness. It is suggested that the formulations of AS 4100 be used for the lateral buckling capacity design of CFCs, instead of those of AS 4600.