Experimental and numerical investigations on shear behavior of RC beams strengthened with U-wrapped PET FRP

This paper reports the investigations of experimental and numerical programs on the shear performance of U-shaped Polyethylene Terephthalate (PET) FRP-retrofitted RC beams. Twelve RC beams were fabricated and tested under monotonic three-point loading with the test parameters being FRP strip width and shear span-to-effective depth ratio. A comprehensive analysis and investigation were conducted in terms of the failure modes, shear load–deflection responses, shear capacities, the strain evolution of FRP and stirrups, and the interaction of shear contributions among FRP, stirrups and concrete. Larger debonding strains were observed for PET FRP. Five design guidelines and two models available in the literature were assessed against the measured PET FRP shear contribution. A modified model of the shear contribution for PET FRP was developed and verified by the test results. Finally, a finite element model was established to further understand the shear performance of retrofitted beams, in which the bond-slip relationship between concrete and FRP was considered. The FE model was validated by comparing the test and FE results. The proposed FE model could accurately capture the propagation of shear critical cracks and FRP debonding failure for the specimens with medium and large shear spans. © 2024 Elsevier Ltd.