Experimental and Numerical Investigation of Buckling Behaviour in Q690 High-Strength Steel Tubes Under Combined Axial Compression and Bending Loads

This paper investigates the buckling behavior of Q690 high-strength steel tubes under combined axial compression and bending loads through experimental testing and finite element analysis (FEA). A total of 27 full-scale specimens with varying slenderness ratios (λ) and diameter-to-thickness (D/t) ratios were tested to evaluate their load-bearing capacity, deformation characteristics, and failure modes. The experimental setup replicated real-world conditions, with constant axial loads applied alongside incremental bending moments until failure occurred. FEA models, developed using ABAQUS, incorporated geometric imperfections and material nonlinearities to simulate realistic structural behavior and predict critical buckling moments. The comparison between experimental and numerical results showed strong agreement, with deviations ranging from 5.6% to 7.9%, confirming the reliability of the simulations. The findings indicate that tubes with higher D/t ratios are more sensitive to imperfections, experiencing significant reductions in post-buckling moment capacity, while those with lower D/t ratios demonstrated greater resistance to buckling and maintained higher structural integrity. The transition between global and local buckling modes was effectively captured by both experimental and numerical approaches, validating the robustness of the models. This study emphasizes the importance of accounting for geometric imperfections and residual stresses in design practices to ensure the safety and reliability of high-strength steel structures under combined loading conditions. Additionally, the results underscore the effectiveness of advanced FEA tools in predicting structural behavior, providing valuable insights for improving design codes and practices. Future research is recommended to explore dynamic loading scenarios, such as wind or seismic effects, to further enhance the applicability of Q690 steel tubes in critical infrastructure projects.