Critical load for shear-induced lateral-distortional buckling in I-section steel beams considering flexural stiffness ratio

Abstract

In prefabricated buildings, lateral-distortional buckling (LDB) of I-section steel beams is a common failure mode that has garnered considerable attention. However, existing studies and design methods for lateral-distortional buckling primarily focus on members subjected to in-plane flexure and do not take into account the influence of shear forces. In this paper, a study on the elastic lateral-distortional buckling behavior of I-section steel beams under in-plane shear loads was conducted. Firstly, refined finite element (FE) models of beam webs under shear loads were established and validated against theoretical formulas for different boundary conditions. Subsequently, by combining with analytical solutions and numerical results, an accurate buckling load formula for the beam web with a free bottom edge was obtained, which can be used for further study. Based on the parametric analysis results, a formula was obtained to determine the critical flexural stiffness ratio of flange to web. When the flexural stiffness ratio exceeds the critical value, the lateral-distortional buckling of I-section steel beams can be effectively avoided. Finally, a formula that incorporates both the critical flexural stiffness ratio and the span to height ratio was proposed to calculate the elastic critical lateral-distortional buckling loads of I-section steel beams solely under in-plane shear loads.