A refined approach for determining local buckling coefficients of box sections with flanges thicker than webs under axial compression

Purpose The purpose of this study was to establish an analytical framework for accurately determining the local elastic buckling coefficients and, consequently, the critical local elastic buckling stresses of simply supported box sections with flanges thicker than webs under axial compression. Design/methodology/approach An analytical approach was developed for determining the local buckling coefficients of box sections, based on the assumption that they consist of isolated web and flange plates and accounting for the interactions arising between these plates due to differences in critical local buckling stresses. The interaction factor was defined by treating the local buckling coefficient of a simply supported isolated web plate as the lower bound and that of a fixed-fixed isolated web plate as the upper bound, given that the web segment governs the critical behavior of the box sections. The derived analytical expressions were validated against linear elastic eigenvalue buckling analyses performed in Abaqus. Findings The critical local buckling stresses calculated using the local buckling coefficients derived from the proposed analytical approach showed significantly improved agreement with the finite element results compared to existing methods. These findings confirmed that the developed approach offers superior predictive accuracy relative to established models in the literature. Furthermore, the findings revealed that the proposed approach effectively overcomes the limitations of existing methods in predicting critical local buckling stresses for box sections with flange-to-web thickness ratios exceeding 2. The results also demonstrated that, regardless of the mid-line height-to-width ratio, when the flange-to-web thickness ratio is greater than 4, the local buckling behavior of box sections closely approximates that of an isolated web segment with fixed-fixed boundary conditions under axial compression. Originality/value This study introduces a novel analytical framework for predicting critical local buckling stresses of simply supported box sections under axial compression, specifically for flange-to-web thickness ratios greater than 2, filling a significant gap in the literature and validating the model through finite element simulations.