Punching Shear Behavior of Slab-Column Structures with Hybrid Reinforcements: Experiment, Simulation, and Theoretical Analysis

Rebar corrosion is a potential cause of punching shear failure in slab–column structures. One economical and effective solution is partially replacing traditional steel rebars with corrosion-resistant materials such as basalt fiber reinforced polymer (BFRP) bars. This study investigates the punching shear performance of slab–column connections with hybrid bars through an experimental program involving two reinforced concrete (RC) slab–column connection specimens and four specimens reinforced by hybrid steel and BFRP bars. The BFRP bars used were equivalent in either area or stiffness to the replaced steel bars. The experimental results showed that partial replacement with BFRP bars of equivalent area led to decreased initial stiffness and reduction in punching shear strength by 7.9% to 14.6%, respectively. Replacement based on equivalent stiffness slightly increased the initial stiffness and load capacity but decreased the energy dissipation capacity. The numerical study was conducted to investigate the influential parameters and to obtain the optimal replacement area. Finally, a method was developed to compute the punching shear strength of slab–column connections adopting the equal-area replacement scheme through modifying the critical shear crack theory (CSCT). The predicted results by the modified CSCT agree well with both experimental and numerical results.