Finite Element Analysis of the Flexural Performance of Hybrid (Steel-BFRP) RC Beams under Repeated Loading: Verification and Parametric Investigation

Abstract

The corrosion of steel bars in reinforced concrete structures subjected to harsh environments remains a significant challenge. Fiber-reinforced polymer (FRP) composites have been investigated as potential alternatives to conventional steel reinforcement. While basalt fiber-reinforced polymer (BFRP) bars exhibit high tensile strength, durability, and sustainability, they are characterized by linear elastic behavior and a brittle failure mode. Hybrid reinforcements of steel and BFRP bars combine the ductility of steel with the corrosion resistance of BFRP. This study presents the development and validation of a three-dimensional nonlinear finite element (FE) model in ABAQUS to simulate the flexural behavior of high-strength concrete (HSC) beams reinforced with a hybrid (steel/BFRP) system under repeated loading. Six beam specimens with a compressive strength of 86.5 MPa were modeled and validated against experimental results. The FE model predicted ultimate load capacity with an average error of 4.97%, while deflection predictions showed an average error of 17.44%. The beams failed when the concrete cracked before the BFRP bars reached their full tensile capacity. A parametric study investigated the effects of increasing the concrete compressive strength from 86.5 MPa to 120 MPa on BFRP stress utilization, ultimate load capacity, and failure mode. Numerical results predict that increasing the concrete strength to 120 MPa significantly enhances structural performance, suggesting a shift in failure mode as indicated by the model. These findings provide valuable insights into optimizing hybrid reinforcement systems for improved structural efficiency and durability.