Nonlinear finite element analysis of fiber-reinforced polymer wrapped reinforced concrete beams

Abstract

Fibre reinforced polymers provide a feasible solution for the repair and strengthening of deteriorated structures by using externally bonded sheets or prefabricated laminates. In spite of the significant research being reported on their structural mechanism and performance, there are still great deals of concerns regarding possible premature failure due to debonding. To this end, a nonlinear 3D finite element model has been developed in current study for FRP wrapped reinforced concrete beams to simulate the flexural behaviour accompanied by the debonding phenomena between concrete and FRP layer. The numerical simulation of FRP strengthened RC beams is performed using ABAQUS/Standard (HKS 2008) finite element code. The finite element model incorporates the nonlinear material behavior of concrete, bilinear stress-strain curve of steel and linear elastic behavior of FRP material. The concrete was modelled using a plastic damage model and two models, friction model and a cohesive model, were evaluated for the concrete-CFRP interface. The former one is relatively simple and easy to handle as compared to the later one. Cohesion model is not only sophisticated but also computationally expensive as compared to the friction model which assumes perfect bond between FRP and concrete. However, the cohesion model is more appropriate for simulating the debonding of FRP from concrete. The performance of the numerical model was studied by simulating several experimental beams from the literature. The load-displacement curves and failure mode obtained numerically were compared to the corresponding experimental results. The FEM results agreed well with the experiments when using the cohesive model regarding failure mode and load carrying capacity while the friction model was not able to represent the debonding failure mode. A parametric study was carried out to investigate the influence of geometric properties such as bonded length, width and thickness of the CFRP sheets on the flexural behavior of the reinforced concrete beams. The results showed that with the increase of the length of CFRP increases the load carrying capacity of the beam increases. The stiffness of the beam also increases with the increase of FRP length Moreover, a beam with larger width of the FRP wrap results in higher strength gain of the rehabilitated beam as the FRP length increases in comparison to a beam with smaller FRP width.