Numerical and Analytical Study of Concrete Beams Reinforced with Hybrid Fiber-Reinforced Polymer and Steel Bars

Abstract

This study presents a numerical model to evaluate the flexural behavior of concrete beams reinforced with hybrid fiber-reinforced polymer (FRP) and steel bars. The bond–slip action between the reinforcing bars and the surrounding concrete was considered. The cracking load, yielding load, ultimate flexural capacity, strain development, moment–curvature relationship, and midspan deflection were predicted using the proposed numerical model. The model was compared with the experimental results available in the literature and the theoretical results from the design codes. The equations from the design codes underestimated the cracking load by 7%–9%. The averages of numerical yielding moments without and with a bond were 0.96 and 0.97, respectively. The predicted yielding moment considering the bond behavior was approximate to that of neglecting bond. The predicted ultimate flexural capacity without a bond was 3% higher than the test result, whereas the predicted result with the bond was 1% lower than the experimental result. Both design codes underestimated the mid-span deflection under service loads for hybrid-RC beams. The postyielding deflection and deflection behaviors at the service load level were captured well by the proposed model. A parametric study investigated the effects of the reinforcement arrangement. Beams [with a glass FRP (GFRP) reinforcement ratio of 2.06%] with reinforcements placed in one layer presented the highest ultimate capacity, 19.6% and 14.0% higher than those of GFRP bars placed at the outer and inner layers, respectively. Beams with GFRP bars placed in the outer layer showed the highest deformability index when the GFRP reinforcement ratio was less than 1.75%.