An X–FEM Technique for Modeling the FRP Strengthening of Concrete Arches with a Plastic–Damage Model; Numerical and Experimental Investigations

In this paper, an enriched–FEM method is presented based on the X-FEM technique by applying a damage–plasticity model to investigate the effect of FRP strengthening on the concrete arch. In this manner, the damage strain is lumped into the crack interface while the elastic and plastic strains are employed within the bulk volume of element. The damage stress–strain relation is converted to the traction separation law using an acoustic tensor. The interface between the FRP and concrete is modeled using a cohesive fracture model. The X-FEM technique is applied where the FE mesh is not necessary to be conformed to the fracture geometry, so the regular mesh is utilized independent of the position of the fracture. The accuracy of the proposed plastic-damage model is investigated under the monotonic tension, compression, and cyclic tension loading. Furthermore, the accuracy of the cohesive fracture model is investigated using the experimental data reported for the debonding test. In order to verify the accuracy of the proposed computational algorithm, the numerical results are compared with those of experimental data obtained from two tests conducted on reinforced concrete arches strengthened with FRP. Finally, a parametric study is performed by evaluating the effects of high to span ratio, longitudinal reinforcement ratio, and strengthening method.