Flexural Behavior of ECC–Concrete Hybrid Composite Beams Reinforced with FRP and Steel Bars

AbstractThis paper investigates the flexural behavior of engineered cementitious composite (ECC)–concrete hybrid composite beams reinforced with fiber-reinforced polymer (FRP) bars and steel bars. Thirty-two hybrid reinforced composite beams with various ECC height replacement ratios and combinations of FRP and steel reinforcements are experimentally tested to failure in flexure. Test results show that cracking, yield, ultimate moments, and the stiffness of hybrid and ECC beams are improved compared with traditional concrete beams with the same reinforcement, due to the excellent tensile properties of ECC materials. The average crack spacing and width decrease with the increase of ECC height replacement ratio. The ductility of hybrid reinforced composite beams is higher than that of traditional RC beams, whereas their practical reinforcement ratios are similar. Reinforced ECC beams show considerable energy dissipation capacity due to the ECC’s excellent deformation ability. Considering the constitutive models of materials, compatibility and equilibrium conditions and formulas for the prediction of cracking, yield, and ultimate moments as well as deflections of hybrid reinforced ECC–concrete composite beams are developed. The proposed formulas are in good agreement with the experimental results. A comprehensive parametric analysis is conducted to illustrate the effect of reinforcement and ECC and concrete properties on the moment capacity, curvature, ductility, and energy dissipation of composite beams.