Effect of concrete strength and tensile steel reinforcement on RC beams externally bonded with fiber reinforced polymer composites: A finite element study

Due to the continual deterioration of concrete infrastructures, the construction industry faces challenges in terms of their serviceability, structural strength, and durability. Therefore, efficient rehabilitation strategies are required to enhance their performance. Externally bonding fiber reinforced polymers (FRP) have evolved as a simple and convenient retrofit technique when compared to conventional techniques of strengthening. FRPs can be powerful tools for strengthening concrete structural members in shear and flexure because of their exceptional mechanical characteristics. Flexural strengthening is generally achieved by externally bonding FRP strips or laminates in the soffit side of beams, resulting in improved ultimate strength and bending capacity. This study aims to conduct a numerical parametric investigation on reinforced concrete (RC) beam specimens flexurally strengthened by externally bonding FRP. Three-dimensional finite element models of four RC beams strengthened with FRP and with different concrete compressive strength and flexural steel reinforcement were developed to predict their load capacity. Models were developed and simulated using finite element software called ABAQUS. The beam behavior was evaluated with the help of different material models available in the ABAQUS library. Study considerations included concrete damage plasticity, Hashin's damage in CFRP, and perfect bonding between CFRP and concrete interfaces. The parametric study included two groups of beams: one with varying concrete compressive strength (i.e., 25 MPa and 50 MPa) and the other with varying tensile steel reinforcement (5#14 mm diameter bars and 2# 22 mm diameter bars). The ABAQUS results were verified using experimental data from the previous literatures. The computed numerical results and experimental results demonstrated reasonable accuracy for load–displacement curves and ultimate load capacity. It was found that the ultimate load increased significantly in high-strength (M50) beams with a higher number and smaller diameter (5#14 mm) tensile bars. In conclusion, RC beams with more compressive strength and tensile steel reinforcement boost the effectiveness of the external bonding technique.