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

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, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>A</mml:mi> <mml:mi>f</mml:mi> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mi>A</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:mrow> </mml:math> , shear span-to-depth ratio, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>a</mml:mi> <mml:mo>/</mml:mo> <mml:mi>d</mml:mi> </mml:mrow> </mml:math> , reinforcement arrangement and compressive strength, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>f</mml:mi> <mml:mi>c</mml:mi> <mml:mo>′</mml:mo> </mml:msubsup> </mml:mrow> </mml:math> . 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, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>ρ</mml:mi> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>f</mml:mi> <mml:mi>f</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>A</mml:mi> <mml:mi>f</mml:mi> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mi>A</mml:mi> <mml:mi>s</mml:mi> </mml:msub> </mml:mrow> </mml:math> ratio increased. A reduction in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>a</mml:mi> <mml:mo>/</mml:mo> <mml:mi>d</mml:mi> </mml:mrow> </mml:math> 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.