Flexural-torsional performance of web-embedded U-shaped steel-concrete composite beams

Web-embedded U-shaped steel-concrete composite beam (WUSCB) was designed and seven specimens were tested under combined flexure and torsion to study the damage process and failure modes considering bending moment-torque ratio (M/T). Two typical failure modes, combined with torque-torsion ratio curves and stress distribution, were observed: the torsional failure caused by the crushing of concrete between critical cracks close to the beam fixed end (M/T ≤ 3) and the flexural failure caused by the crushing of concrete flange close to the beam fixed end (M/T > 3). A finite element model was established to further study distribution of stress and to enrich experimental analysis. It was studied that appropriate bending moments can enhance torsional capacity WUSCB, while excessive bending moments will have opposite effects. Based on the study results, correlation curves of WUSCBs’ flexural-torsional capacity were proposed.