Non-linear behaviour of concrete beams reinforced with GFRP and CFRP bars grouted in sleeves

The low-quality bond between fibre reinforced polymer (FRP) bars and surrounding concrete has drawn the attention of many researchers. The use of high-strength materials such as the grout in the intersection of FRP bars and surrounding concrete can effectively prevent any slippage once they are in contact and subsequently increase the bond quality. Therefore, this study was numerically focused on the flexural behaviour of concrete beams reinforced with glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP) bars, grouted only in the pure bending zone and along the whole beam length. The numerical outputs revealed that the grouted GFRP bars propagated the maximum principal stress in high-strength concrete beams, but not as much as that in normal-strength concrete specimens. In addition, the stress distribution in the grout, created only in the pure bending zone, was nearly constant at the ultimate moment. For the grout, developed along the whole beam length, this stress increased by approaching the mid-span of the concrete beam. Furthermore, at the ultimate moment, the tensile stress of 12-mm diameter CFRP bars was about 3.5 times more than that of the 16-mm diameter CFRP bars, leading to the generation of difference between failure modes of concrete specimens reinforced with various diameters of CFRP bars

Effects of the Concrete Strength and FRP Reinforcement Type on the Non-Linear Behavior of Concrete Deep Beams

To provide sustainable reinforced concrete deep beams, the replacement of steel rebars by FRP rebars with high-chemical resistance is proposed by researchers. However, the effects of the concrete strength, top and web longitudinal reinforcements, and types of FRP flexural rebars on the non-linear performance of concrete deep beams have rarely been evaluated. This study numerically assessed the effects of the top and web longitudinal reinforcements and concrete strength on the non-linear behaviour of GFRP- and CFRP-strengthened concrete deep beams with various shear span-to-overall depth (a/h) ratios. As per the results, the highest tensile stress was obtained for the steel reinforcement, and the tensile stress in the CFRP reinforcement was more than that of the GFRP reinforcement under the failure load. Meanwhile, the results of high- and normal-strength concrete deep beams with the web reinforcement (16.4%) were lower than those without the web reinforcement (22.3%). Therefore, the web reinforcement moderately compensated for the low strength of normal concrete and the absence of the top longitudinal rebar to reinforce concrete deep beams in carrying the ultimate load. Furthermore, the participation of the GFRP reinforcement with the high-strength concrete was more than that with the normal-strength concrete in carrying a higher amount of loading