Predicting the rotation capacity of cold-formed RHS beams using finite element analysis

This paper describes finite element analysis of cold-formed rectangular hollow section (RHS) beams to predict the rotation capacity of Class 1 (Plastic) and Class 2 (Compact) beams. Introducing geometric imperfections into the model was essential to obtain rotation capacities that were close to the experimental results of bending tests on cold-formed RHS beams. A perfect specimen without imperfections achieved rotation capacities much higher than those observed experimentally. Introducing a bow-out imperfection, constant along the length of the beam, as was measured experimentally before fabrication, did not affect the numerical results significantly. To simulate the effect of the imperfections induced by welding the loading plates to the beams in the experiments, the amplitude of the bow-out imperfection was varied sinusoidally along the length of the beam, and restricted to a specific region within each beam. The magnitude of the geometric imperfections had an unexpectedly large influence on the rotation capacity of the specimens. Larger imperfections were required on the more slender sections to simulate the experimental results. (C) 2002 Elsevier Science Ltd. All rights reserved.