Post-buckling behavior of cold-formed thin-walled stainless steel beams

Abstract

A numerical approach for predicting the post-buckling responses of cold-formed thin-walled stainless steel beams is presented. In the analysis, the nonlinear and unsymmetrical stress-strain relations in tension and compression for both flat and corner materials are considered. The effective width concept is used to account for the post-buckling strength of the thin compression flange of the beam. Using this concept, the value of the effective width varies with the stress borne by the flange edge. In view of the nonlinearities introduced by considering the material characteristics and the post-buckling behavior of the individual elements, an iterative procedure is employed to establish the nonlinear moment-curvature relation of a section. In a beam subjected to bending, the effective moment of inertia of the section varies from point to point along the length of the beam depending upon the magnitude of the moment at the point considered. In this analysis, the continuously flexible beam is replaced with a finite number of discrete rigid elements connected by flexible joints at which the continuously varied curvature is lumped through numerical integration. In the case of a continuous beam, it is further complicated by the fact that the bending moment distribution along the beam is not known a priori and its determination is part of the solution to the problem. An iterative algorithm is developed to obtain the approximate true moment distribution considering the compatibility conditions at the support. A computer program following th e above solution scheine has been developed and is capable of predicting the nonlinear responses of most of the common thin-walled sections encountered in light-gage steel design. Comparisons with some available experimental data are provided.