Effect of headed stud spacing on flexural behavior of steel plate-UHPC composite beams: Experimental and numerical investigation

The steel plate-ultra-high performance concrete (UHPC) composite beam (SUCB) is developed to achieve a higher strength-to-weight ratio. This beam combines the tensile strength of steel plates with the compressive strength of UHPC. In this study, five SUCBs with different spacings of headed studs (165, 135, 110, 100, and 80 mm) were investigated through bending tests. The impact of headed stud spacing on the flexural behavior of SUCBs was examined, including failure modes, crack distribution, load-bearing capacity, slip, and strain distribution. Experimental results revealed two distinct failure modes: flexural-slippage failure for spacings ≥ 110 mm and flexural failure for spacings ≤ 100 mm. Although reducing the headed stud spacing effectively minimized slip between the steel plate and UHPC, it had a negligible effect on load-bearing capacity. To more efficiently and adaptably simulate the interface behavior between the steel plate and UHPC, a novel finite element (FE) modeling strategy was developed, integrating the load-slip behavior of headed studs into the interface elements. This approach demonstrated high accuracy in predicting both failure modes and load-deflection responses. Finally, a modified analytical formula for calculating deflection in SUCBs was proposed, accounting for slip characteristics resulting from the headed studs. The accuracy of the formula was validated through comparison with experimental data and FE results. These findings provide critical insights for optimizing shear connector design in SUCBs, balancing structural efficiency and economic feasibility.