Numerical and theoretical studies on the shear behavior of composite beams with a steel-UHPC composite web

To reduce self-weight, accelerate bridge construction, and lower construction costs of steel-concrete composite beams, hot-rolled steel (HRS)-ultrahigh performance concrete (UHPC) composite beam (SUCB) was proposed to utilize HRS products and excellent mechanical properties of UHPC. The flexural performance of SUCBs has been studied recently while the shear behavior of SUCBs is still limited. This paper aims to address the gap in the shear behavior of SUCBs with a composite web. Based on the experimental investigation of four SUCBs, a threedimensional finite element model (FEM) was developed and verified by comparing with shear tests, demonstrating a good simulation accuracy with experimental results. Furthermore, a parametric study was conducted to investigate the effects of the shear span-to-depth ratio, HRS and UHPC strengths, stirrup ratio, and dimensions of the composite section on the shear behavior of composite beams in terms of load-deflection curves, shear capacity, shear strength provided by HRS, and HRS shear contribution. The numerical results indicated that improvements of HRS yield strength, UHPC compressive strength, thicknesses of HRS and UHPC webs, stirrup ratio, and overall depth obviously increased shear capacity. The shear capacity improved by more than 50 % as the shear span-to-depth ratio decreased from 2.5 to 0.7. Compared to cases with a shear span-to-depth ratio of 1.3, the shear strength devoted by the HRS beam of cases with a shear span-to-depth ratio of 2.0 decreased by 32.5-35.5 %, while the HRS shear contribution decreased by 12.9-18.0 %. Moreover, an increase in the overall depth of composite beams and parameters related to HRS beams resulted in a decrease in the yielding shear span- to-depth ratio, while an increase in the parameters related to UHPC T-beams expect for UHPC tensile strength resulted in an increase in the yielding shear span-to-depth. Finally, based on the numerical analysis results, an analytical method was proposed for evaluating the shear strength contributed by the HRS beam and the total shear capacity of HRS-UHPC composite beams, with a mean absolute calculation error of blow 10%.