A new proposal for the design of laterally unrestrained cellular steel beams under moment gradient at elevated temperatures

Abstract

The laterally unrestrained cellular steel beams (CB) are more susceptible to buckling failure and collapse early due to the material degradation that occurs in a fire situation. The lateral-torsional buckling (LTB) resistance design proposed by Eurocode 3 pt. 1–2 is relatively conservative for both uniform and non-uniform bending cases and hence needs to be improved. This paper aims to investigate the influence of single and double curvature bending on the LTB resistance of cellular steel beams subjected to elevated temperatures. To carry out the present numerical study, the finite element (FE) models are first validated with a set of numerical and experimental data available from the existing literature. Extensive parametric FE analyses are performed by considering different sizes and spacing of the opening, and various beam slenderness for hinge and roller boundary conditions. Based on parametric research, a new design proposal for LTB buckling resistance of CB at elevated temperatures for various moment gradients is presented. Compared with the analytical results provided by Eurocode 3 pt. 1–2, the proposed design method is safer and conservative. The proposed approach provides better agreements than existing procedures. Moreover, a statistical analysis of the results is performed, and the accuracy of a new proposal is presented in this paper.