Investigation of punching shear performance in concrete slabs reinforced with GFRP and synthetic fibers: an experimental study

The punching shear resistance mechanism of reinforced concrete slabs with glass fiber-reinforced polymers (GFRP-RC) is weaker than that of steel-RC slabs. The reduced shear strength and modulus of elasticity of GFRP reinforcement which led to greater tensile strains of the reinforcement and shallower compressive zone reduce the contribution of concrete in compression, aggregate interlocking, and dowel action to the punching shear mechanism. This condition results in reduced capacity and a higher likelihood of catastrophic failure compared to their steel-RC counterparts. To address this weakness of GFRP-RC, this paper aims to examine the punching shear performance of GFRP-RC slabs and explore the potential improvements through the incorporation of synthetic fibers. A total of 11 two-way slabs having a dimension of 1000 × 1000 mm with a thickness of 80 mm were tested under punching shear load and the effect of several types of fiber (polypropylene (PP) and (polyvinyl alcohol (PVA)), fiber content (0, 0.5%), reinforcement ratio, and reinforcement type (steel and GFRP) was investigated. The slabs’ behavior was assessed by considering crack width, deflection performance, the mode of failure, and the overall load-bearing capacity. The findings indicated that the influence of fibers was more noticeable in GFRP-RC slabs compared with steel-RC counterparts. Moreover, the fibers were found to effectively reduce deflections and crack widths. The results particularly showed the superior performance of PVA fibers in improving the capacity of the two-way slabs, whereby the addition of 0.5% PVA fibers led to the punching shear capacity increase of 44–51%. The findings of this study offer a better understanding of the punching shear behavior of slabs reinforced with GFRP reinforcement and synthetic fibers.