Modelling of interfacial debonding between FRP and concrete using the scaled boundary finite element method

Abstract

Interfacial debonding between fibre-reinforced polymer (FRP) and concrete is one of the most common failure modes in externally bonded FRP (EB-FRP) strengthened concrete structures, typically occurring within a thin layer of concrete near the interface. This study uses the scaled boundary finite element method (SBFEM), a semi-analytical numerical approach, to model the interfacial debonding process between FRP and concrete. The quadtree meshing scheme is used to smooth the mesh transition near the interface, and high computational efficiency is achieved by exploiting the advantages of SBFEM. The Mazars damage model, which considers the tensile and compressive damage separately, is integrated with a nonlocal model to eliminate mesh sensitivity, thereby enabling the accurate prediction of damage evolution in the concrete substrate. Several benchmarks, including three-point bending notched beams (TPBNB), a double notched tension beam (DNTB) and single shear FRP-concrete specimens, are simulated to confirm the effectiveness and reliability of the proposed method. The numerical results align closely with both the experimental data and finite element modelling. Furthermore, the effects of internal length, bond length, FRP stiffness, and concrete strength on the interfacial bonding performance are investigated. The existence of the effective bond length and its relation to the bond length are confirmed. The results also reveal that the failure mode of the interface is sensitive to the internal length and that the ultimate debonding load depends critically on both FRP stiffness and concrete strength.