Punching Shear Behavior of Synthetic Fiber-Reinforced Self-Consolidating Concrete Flat Slabs with GFRP Bars

Glass fiber-reinforced polymer (GFRP)-reinforced flat slabs offer a convenient construction option that is both simple to build and highly resistant to corrosion. The relatively low thickness of the floor plates and absence of beams results in increased susceptibility to punching shear failure, which may become the governing design factor. This paper presents an experimental investigation on the use of synthetic fiber-reinforced self-consolidating concrete (SNFRSCC) to improve punching shear capacity of GFRP-reinforced flat slabs. Synthetic fiber was used because it is inert and corrosion resistant, and SCC facilitates use of fibers in relatively high dosages without adverse effects on concrete placing quality. Six large-scale interior slabs were experimentally tested for punching shear behavior assessment. Three SNFRSCC specimens with varying longitudinal reinforcement ratios were compared with their SCC control counterparts. It was confirmed experimentally that the punching shear capacity did not display high dependency on the longitudinal reinforcement spacing. However, the punching shear capacities of the SNFRSCC specimens were marginally improved in comparison with the control specimens. In addition, the SNFRSCC specimens exhibited substantial toughness improvements (2.34 times on average). Moreover, analytical expressions were developed to estimate the punching shear capacity as well as load-rotation relationships for the GFRP-reinforced SCC and SNFRSCC slabs. The analytical expressions were based on the critical shear crack theory (CSCT). The modified CSCT predictions showed a considerable agreement with the experimentally observed load-rotation behavior and punching shear capacity for SCC and SNFRSCC specimens alike.