Punching shear strength and deformation for FRP-reinforced concrete slabs without shear reinforcements

Abstract

While very little is known about the punching shear behavior of Fiber Reinforced Polymer (FRP)-reinforced concrete slabs; thus, very few design codes for this case are available. Most available design codes and guidelines are missing the physical meaning of various aspects. In addition, the critical shear crack theory (CSCT), developed in the '90s for shear and punching shear of concrete elements, has covered a wide range of shear and punching shear problems but did not tackle punching shear of FRP-reinforced concrete slabs. The strength of FRP-reinforced concrete slabs is different from the conventional steel-reinforced concrete slabs in several ways, including but not limited to: (1) having a variable young’s modulus depending on the type of FRP; (2) the flexure strength of FRP-reinforced concrete slabs is different, while the failure occurs due to concrete crushing; and (3) FRP is linear up to failure with no yield plateau. This study aims to develop a mechanical model based on FRP-reinforced concrete slabs' physical punching shear behavior. An extensive experimental database was collected with 189 FRP-reinforced concrete slabs from 37 different studies. A new mechanical model was developed and proposed based on the critical shear crack theory (CSCT). The proposed model captured the behavior accurately and was based on a physical model. The proposed model included the effect of young’s modulus and the different failure modes. It can predict both the strength and rotation of FRP-reinforced concrete slabs under punching shear.