Numerical analysis on the shear performance of hybrid (BFRP/steel) reinforced concrete beams without shear reinforcement

Abstract

Using fiber-reinforced polymer (FRP) bars as an alternative to steel reinforcement has emerged as a pioneering solution to the issue of corrosion in reinforced concrete (RC) structures. However, FRP-RC beams without shear reinforcement exhibit lower shear capacity due to the limited transverse strength of FRP bars. Hybrid reinforcement using a combination of FRP and steel bars offers a promising solution by balancing the strain-hardening benefits of steel with the corrosion resistance of FRP. In this study, a 3D finite element model (FEM) was developed through Abaqus software to investigate the shear behavior of hybrid-RC beams without shear reinforcement. The analysis considered key parameters, including reinforcement type and ratio, FRP-to-steel area ratio, $A_f/A_s$ , shear span-to-depth ratio, $a/d$ , reinforcement arrangement and compressive strength, $f_c^{\prime }$ . The numerical results revealed that hybrid-reinforced beams exhibited a 21%–54% increase in stiffness and 35%–89% enhancement in ductility compared to beams reinforced solely with steel or basalt FRP (BFRP) bars. Moreover, shear capacity significantly improved as the effective reinforcement ratio, ${\rho }_{eff}$ and $A_f/A_s$ ratio increased. A reduction in the $a/d$ ratio from 2.27 to 1.7 led to a notable increase in shear capacity of 55%. In addition, increasing the compressive strength from 41 to 50 MPa resulted in 31% improvement in the shearing capacity. The numerical results were conservative compared to predictions from available shear equations in design codes, demonstrating the reliability of the FEM approach.