Analytical and Numerical Study of FRP Retrofitted RC Beams Under Low Velocity Impact

An analytical along with numerical analysis has been carried out to investigate the behavior of concrete simply supported beams strengthened with Fiber-Reinforced Polymer (FRP) unidirectional laminates under impact loading. Concrete beams are reinforced with a minimum ratio of flexural and shear steel rebars and finally retrofitted with epoxy-bonded high strength carbon FRP laminates in their flexure surfaces. The impact force was applied with a solid steel cylinder drop weight. Analytical results showed that composite laminates externally bonded to reinforced concrete beam substrate can significantly enhance the performance of theses structural members to resist impact loadings. Also, based on the obtained results, in retrofitted beams the crack propagation happens in a desirable mode; an increasing of yielded rebar zones and residual beam stiffness. Retrofitted beams were stiffer than unretrofitted ones in their first impact response. The residual stiffness of impacted concrete beams depends on their initial stiffness and the impact energy level. The analytical method uses an idealized elastic spring-mass model and flexural wave propagation theory to calculate the dynamic response of assumed beams. Analytical responses are adjusted due to an inelastic response, and finally are used for the simplified designation of impact resisting reinforced concrete beams retrofitting laminates.