Flexural behavior of RC continuous beams having hybrid reinforcement of steel and GFRP bars

Fiber reinforced polymers (FRP) have been considered to be the alternative material to steel in reinforced concrete structures (RC) with the advantages of corrosion resistance, non-conductivity, and high strength-to-weight ratio. FRP-RC beam is featured with higher deformability and larger crack width. However, there is no recognizable ductility in FRP-RC members. Due to the lack of the ductility of FRP-RC beam, it was suggested using hybrid reinforcement of steel and FRP to achieve a preferable strength and ductility. The flexural behavior of the concrete beams reinforced with hybrid reinforcement was investigated through series of six continuous beams. The positive moment GFRP reinforcement ratios of 0.75% and 1.25% were used and the steel reinforcement ratios were ranged to determine the optimum percentage to work efficiently with GFRP. The experimental results showed that increasing GFRP positive moment reinforcement ratio to be more than 1.4 ρ f b increased the flexural capacity of the section but with less ductile behavior. However, increasing the steel positive moment reinforcement ratio leaded to the increase of both the flexural capacity and the ductile behavior in a condition that the steel positive moment reinforcement ratio was ≤ 3 4 ρ f . It was shown that the flexural capacity predication of the hybrid section using the semi brittle elastic material method to present the de-bonding of moment that occurred at the failure stage had a good accuracy with the experimental results.