Torsional behaviour of high strength steel (S700) rectangular hollow section stub column

This study aims to investigate the torsional behavior of high strength steel (S700) rectangular hollow section stub columns through comprehensive finite element analysis using ABAQUS. The influence of key geometric parameters, including cross-section aspect ratio and wall thickness, on torsional performance is evaluated. The numerical models were validated in two stages: first, the torsional loading scheme was benchmarked against carbon steel rectangular hollow section tests, achieving a strength prediction accuracy of within 3.0%; secondly, the adopted high strength steel material model was verified against axial compression tests with strength predictions within 4.0% of experimental results. The parametric results demonstrate that members with higher aspect ratios (1:1) exhibit superior torsional resistance, with increases up to 32% compared to lower aspect ratio Sect. (1:5), while increasing wall thickness consistently enhances torsional capacity by approximately 9-10 kNm per millimeter increase in thickness across all configurations. Benchmarking against current design specifications, including Eurocode EN 1993-1-5, American code AISC 360 - 10 and the AISI S100 standard with its Direct Strength Method, reveals that existing codes tend to underestimate torsional capacity for high strength steel rectangular hollow section members. These findings emphasize the potential for improved accuracy through FE-based analysis and support calibrated modifications to current design provisions. The study provides critical insights for structural optimization and the refinement of torsion design guidelines for high strength steel rectangular hollow section under pure torsional loading.