The punching shear capacity of reinforced ultra-high-performance concrete (UHPC) two-way slabs in applications such as floor slabs and bridge decks has attracted increasing attention. However, due to the insufficient consideration of the internal force transmission path and failure mechanism, existing empirical formulas exhibit limited accuracy for predicting the punching shear capacity of reinforced UHPC slabs. Therefore, based on the critical shear crack theory (CSCT), this study proposes a specific theoretical model where the tensile strain-hardening behavior and tensile strength of UHPC, the punching shear-span ratio, and the reinforcement ratio are comprehensively considered. In the proposed model, the steel fiber bridging contribution is derived via the variable engagement method (VEM), for which an equation describing the bond strength between steel fibers and UHPC matrix was developed. The feasibility of the proposed model was validated through an established experimental database. Furthermore, the effects of several key parameters on the punching shear behavior of reinforced UHPC slabs were analyzed. The results show that the proposed models can accurately predict the punching shear capacity and ultimate rotation angle of reinforced UHPC slabs. With increasing slab thickness, UHPC strength, and reinforcement ratio, the punching shear capacity increases, whereas the corresponding ultimate rotation angle and steel fiber contribution ratio decrease. Increasing the fiber volume fraction enhances both the fiber contribution and the punching shear capacity. For slabs with higher UHPC strength, the reinforcing effect of a higher reinforcement ratio is more pronounced.
Chen et al. (Thu,) studied this question.