Behavior of GFRP reinforced concrete slabs with openings strengthened by CFRP strips

The utilization of fiber-reinforced polymer (FRP), can be an efficient, and long-lasting solution for increasing the durability of reinforced concrete (RC) structures in hostile environments. FRP can be used as a reinforcement or as a strengthening technique that may recover the load capacity of a structure. This paper aims to investigate the flexural behavior of one-way concrete slabs with openings reinforced by glass fiber-reinforced polymers (GFRP) bars and strengthening using carbon fiber-reinforced polymer (CFRP) sheets. The experimental work consists of five one-way concrete slabs that were tested up to failure. All slabs had the same dimension, 750*2650 mm, with a thickness of 150 mm, and were reinforced with the same reinforcement ratio. The experimental work included one specimen without openings and without strengthening as a solid slab. While, the remaining slabs were fabricated with two different openings, rectangular and square 250*500 mm, and 250*250 mm respectively, and strengthened by CFRP sheets. The test results show that the failure load of existing slabs with mid-span openings is decreased by around 41% and 43%, for one and two openings respectively, compared to the solid slab. The utilization of CFRP sheets enhances the flexural load-carrying capacities by about 52% and 44% and improves the stiffness at the ultimate load by about 101%, and 95%, and decreases the deflection at a service load by about 56% and 54%, respectively compared with the un-strengthened slabs. Furthermore, the experimental data were used to validate a finite element (FE) model along with an additional parametric study.