SRG/SRP–concrete bond–slip laws for externally strengthened RC beams

The goal of the paper is to assess the effectiveness of some Fiber Reinforced Polymer (FRP)–concrete bond–slip laws, widely used in the numerical analyses, to model Steel Reinforced Grout (SRG)–concrete and/or Steel Reinforced Polymer (SRP)–concrete interfaces. The assessment was carried out through a suitable Finite Element (FE) study developed on a set of externally strengthened Reinforced Concrete (RC) beams. For this purpose a database of experimental results, available in literature, was collected.A two-dimensional FE model was defined for each tested beam. The linear and nonlinear behavior of all materials was adequately modeled, whereas the connection between concrete surface and external reinforcing layer was simulated by a cohesive element with a suitable damage model.The numerical and experimental comparisons were used to evaluate the reliability and adaptability of the FRP–concrete bond–slip laws to predict the structural behavior of RC beams externally strengthened to flexure with SRG and SRP innovative systems.The study showed that among a set of bi-linear FRP–concrete bond–slip laws one was also suitable to simulate the behavior of SRG–concrete interface. For the SRP–concrete interface a modification of the same bond–slip law was proposed, calibrated and validated against the available experimental data.