Distortional buckling behaviour and strength of cold-rolled aluminium alloy beams

Abstract

Thin-wall structural sections and members are susceptible to three fundamental instabilities: local, distortional and lateral-torsional buckling. For cold-formed purlins or girts commonly used in roof and wall systems, distortional buckling may govern the predominant failure mode when the compression flange is not attached to sheathing or panels. The paper presents an experimental and numerical investigation on the behaviour and strength of cold-rolled aluminium beams subjected to distortional buckling. A total of eighteen specimens were tested in a four-point bending configuration with six various types of cross-sections and two different thicknesses. In the pure bending region between the two loading points, the upper compression flanges were kept free to allow distortional buckling to form. Subsequently, detailed finite element (FE) models of cold-rolled aluminium beams using the software ABAQUS were developed with the incorporation of measured material inelasticity and initial geometric imperfections. Good agreement between the experimental results and the FE models was achieved. The reliable and verified FE models along with the test data in this paper will be used in a separate publication to undertake a detailed parametric study and calibration of new proposed design rules for cold-rolled aluminium beams subjected to distortional buckling.