Bending Performance of Cold-Formed Thick-Walled Rectangular Steel Beams

An increasing number of cold-formed thick-walled members are being employed in engineering structures. However, research on their bending performance is still lacking, and existing codes are primarily suitable for thin-walled steel members. Therefore, bending tests were conducted on 10 cold-formed thick-walled rectangular beams. The primary test parameters were the width, height, and thickness of the cross section. The material properties, initial geometric imperfections, failure modes, load-deflection curves, ultimate loads, rotation capacities, and load-strain curves of these beams were analyzed. Subsequently, a nonlinear finite-element (FE) model of cold-formed thick-walled rectangular beams was developed. After validating the numerical model with the test results, a parametric study was conducted. The results revealed that the height-to-width, radius-to-thickness, and width-to-thickness ratios significantly affected the plastic development ability of the cross section. With the increase in height-to-width and radius-to-thickness ratios, an existing Chinese design code yielded unsafe limits for the width-to-thickness ratio. Based on the parametric study results, width-to-thickness ratio limits suitable for cold-formed thick-walled cross sections were recommended. Finally, a simplified design method for the bending resistance of cold-formed thick-walled rectangular beams was proposed and validated using experimental and FE model results.