Reference section model for buckling coefficients of web-dominant rectangular hollow section under compression

This study develops refined closed-form analytical solutions for accurately determining local buckling coefficients and corresponding critical local buckling stresses of rectangular hollow sections (RHSs) with web-dominant thickness under axial compression. A novel local buckling model is proposed using a reference-section analytical framework that establishes geometric and mechanical equivalence between an original unequal-thickness RHS and two reference RHSs with equal wall thickness. The first reference section adopts the flange thickness, while the second represents the web thickness, enabling systematic characterisation of local buckling behaviour. Explicit analytical expressions are derived by introducing corner-size factors to capture coupled plate interaction effects and by enforcing compatibility between the buckling responses of the reference and original sections. The proposed solutions are validated against linear elastic local buckling simulations conducted in the Abaqus software program, showing minimal deviations. Results demonstrate that the model accurately predicts local buckling coefficients and stresses, providing slightly conservative yet reliable estimates. Comparisons with previous energy-based studies show close agreement, whereas methods relying on indirectly derived coefficients tend to overestimate stresses. The originality of this work lies in presenting explicit closed-form solutions for unequal-thickness RHSs with web-dominant thickness, addressing a significant gap in the existing literature.