ANALYSIS OF COLD-FORMED OPEN STEEL SECTIONS UNDER SIMPLE BENDING

Resumo

Cold-formed open steel sections under flexural loading are subjected to the combined
phenomena of bending, local (L), distortional (D), global (G) buckling and flange curling. Some of the
main challenges in evaluating the results obtained by numerical and experimental analysis are (i)
defining the displacement portion due to each one of these phenomena, as some of them occur in the
same plane of loading; (ii) the presence of intermediate stiffeners in these members makes the
buckling modes classification imprecise. Additionally, it is known that small changes in the section
geometry may imply large variations in the structural performance. This paper analyzes stiffened CFS
beams through Finite Strip Method (elastic stability analysis) and Finite Element Method (non-linear
analysis with arc-length control for strength prediction). The careful records of the displacements by
numerical analysis, combined with linear regression techniques, allowed evaluating the evolution of
the different mechanical phenomena during loading. The contribution of the stiffener height variation
on the critical bending moments was investigated. Particular interest is addressed to the strength
erosion due to the modal LD interaction, since the tendency of McrL/McrD = 1 ratio is obtained by
optimization methods where the objective function is directed towards the maximization of critical
moments. In this work, the geometric parameters were defined in order to generate variations of the
commercial self-supporting roofing tile RT-260/620 (Regional Telhas), with steel plate thickness of
0.95 mm.