Meso-scale modelling of FRP-to-concrete bond interfaces

The bond behaviour between fiber-reinforced polymer (FRP) and concrete plays a critical role in the performance of FRP-strengthened reinforced concrete (RC) structures. While extensive research has been conducted on debonding failures, existing studies predominantly treat concrete as homogeneous, neglecting its inherent heterogeneity. This paper proposes an effective meso-scale finite element (FE) model incorporating random aggregate distributions to explicitly account for the heterogeneous nature of concrete. As only the compressive strength of concrete is usually reported in bond tests, a set of equations are identified as a guideline for calculating the material properties of mortar and coarse aggregates, as required by the damage plasticity constitutive relations of materials which are employed to model both coarse aggregates and mortar. The proposed model is validated through simulations of uniaxial tensile and compressive tests of concrete and FRP-to-concrete bonded joint experiments. Results demonstrate that the model’s capability to predict the mesoscopic damage and fracture evolution, as well as the macroscopic load-displacement curves and failure patterns. A parametric study reveals that increasing the coarse aggregate fraction from 30% to 50% enhances bond strength and displacement by 7–8%. This meso-scale approach provides a robust tool for developing bond strength and bond-slip models, incorporating concrete’s meso-structural characteristics.