Ultimate behavior of RC beams strengthened in flexure using FRP material

The present paper investigates the ultimate flexural behavior of strengthened reinforced concrete (RC) beams with Externally Bonded (EB) or Near-Surface Mounted (NSM) Fiber-Reinforced Polymers (FRP) reinforcement. For the purpose of predicting the ultimate loads and deflections of strengthened RC beams, numerical and analytical models were developed. Both models were developed for strengthened RC beams that fail in flexure by FRP rupture. First, an analytical model was developed based on the moment-area theorem and the equilibrium of internal forces. Second, based on the finite element (FE) method, an 3D numerical model was developed using Cast3M software, version 21. The reliability of the numerical model was tested against the analytical and experimental results collected from previous research. The selected RC beams were made with Normal-Strength (NS) and High-Strength Concrete (HSC). The comparison showed that the numerical model has an excellent performance in predicting the load-deflection response until failure. Moreover, the beam damage obtained from the numerical modeling agreed with the experimental results. Finally, a numerical comparative study between EB and NSM systems was conducted. The comparison showed the effectiveness of the NSM system in terms of strength and ductility. Further, the analysis of stress and strain showed that NSM system reduces the stresses and strains in concrete and steel reinforcement and prevents cracks propagation.