The effects of residual stresses and strains on lateral-torsional buckling behavior of cold-formed steel channel and built-up I-sections beams

Abstract

Purpose The purpose of this paper is to focus on the influences of residual stresses which were induced during roll-forming sections on lateral-torsional buckling of thin-walled cold-formed steel channel and built-up I-sections beams. Built-up I section is made up of two back-to-back cold-formed channel beams. In this direction, at the primary stage, the roll-forming process of a channel section was simulated in ABAQUS environment and the accuracy of the result was verified with those existing experiments. Residual stresses and strains in both longitudinal and circumferential transverse directions were extracted and considered in the lateral-torsional buckling analysis under uniform end moments. The contribution of the current research is devoted to the numerical simulation of the rolling process in ABAQUS software enabling to restore the remaining stresses and strains for the buckling analysis in the identical software. The results showed that the residual stresses decrease considerably the lateral-torsional buckling strength as they have a major impact on short-span beams for channel sections and larger span for built-up I sections. The obtained moment capacity from the buckling analysis was compared to the predictions by American Iron and Steel Institute design code and it is found to be conservative. Design/methodology/approach This paper has explained a numerical study on the roll-forming process of a channel section and member moment capacities related to the lateral-torsional buckling of the rolled form channel and built-up I-sections beams under uniform bending about its major axis. It has also investigated the effects of residual stresses and strains on the behaviour of this buckling mode. Findings The residuals decrease the moment capacities of the channel beams and have major effect on shorter spans and also increase the local buckling strength of compression flange. But the residuals have major effect on larger spans for built-up I sections. It could be seen that the ratio of moment (with residuals and without residuals) for singly symmetric sections is more pronounced than doubly symmetric sections. So it is recommended to use doubly symmetric section of cold-formed section beams. Originality/value The incorporation of residual stresses and strains in the process of numerical simulation of rolled forming of cold-formed steel sections under end moments is the main contribution of the current work. The effect of residual stresses and strains on the lateral-torsional buckling is, for the first time, addressed in the paper.

Investigations of the through‐thickness residual stress distribution during the partial heating roll forming process of square and rectangular hollow steel sections

“…Similar to square hollow steel sections, the through‐thickness residual stress variations for RHS showed nonlinear distributions. According to previous studies, the magnitude of tensile residual stress decreases as the width to radius ratio decreases 4,23,25,36,37 . Therefore, the RHS presented in this study possessed a relatively lower magnitude of longitudinal residual stresses than the SHS.…”

“…Heinilä et al 22,24 studied the impacts of the residual stresses on fatigue of circular and rectangular cross-sections by conducting experiments and numerical modeling of the cold forming process. In the same way, the study conducted by Kabir and Parvizi 25 showed that residual stress effect on lateral-torsional buckling behavior is very significant. Experimental fatigue tests of Heinilä 22,24 further showed that square hollow section's corner areas are more susceptible to fracture than the flat areas.…”

“…According to previous studies, the magnitude of tensile residual stress decreases as the width to radius ratio decreases. 4,23,25,36,37 Therefore, the RHS presented in this study possessed a relatively lower magnitude of longitudinal residual stresses than the SHS. The maximum residual compressive and tensile stress in the longitudinal direction for reference elements taken from the flat area of RHS1 reaches peak values of 0.45σ y and 0.48σ y , respectively.…”

“…Another factor that might influence the residual stress distributions is the specimen's width‐to‐thickness ratio. Previous studies 4,23,25,36,37 showed that the residual stress decreases as the material's width‐to‐thickness ratio increases. Since SHS1 has a width‐to‐thickness ratio of 31.25 and SHS 2 has 20.…”