Colapso por flexo-torção de colunas de aço formadas a frio sob temperaturas elevadas :resistência última e dimensionamento via MRD

Abstract

An extensive numerical investigation has been reported with evidence that the current Direct Strenght Method (DSM) global strength curve overestimates the ultimate strength of Cold-Formed Steel (CFS) when submitted to uniform compression under fire situation. This study used ultimate strength of elevated temperatures gathered to propose a new set of flexural torsional curves in each temperature, based on DSM, which are clearly different when the slenderness is below than 1,5. This research, that can be read as a continuation of previously studies, investigate the flexural torsional post-buckling equilibrium paths and the DSM for steel columns that exhibit flexural torsional buckling when submitted to uniform compression under elevated temperatures. The results consist of post-buckling equilibrium paths and ultimate strength, obtained through nonlinear shell finite element analyses. To ensure covering wide slenderness ranges, several room/moderate temperatures (20/100 °C) yield stresses and different columns lengths and variety of transversal sections were considerate. The steel is simulated by models prescribed in Eurocode 3: part 1.2. The numerical failure loads obtained in this research and collected in the international literature were used to validated the efficiency of DSM and to propose a modification, making it capable of handling flexural torsional failures under elevated temperatures.