Finite element study of bond-slip behaviour of CFRP and GFRP laminates on brick masonry

Rehabilitation and preservation of historic monuments and ancient structures is attracting more and more interest in the world. There are a certain amount of historic monuments which were built by using brick masonry. As the development of fiber reinforced polymer (FRP) is getting more popular now, applying bonded FRP to strengthen historic brick masonry monuments becomes one of the alternative strengthening method. In the past decade, many researches have been carried out to investigate the behaviour of bonded FRP to reinforced concrete structures. However, still a few contributions are available concerning debonding problem on masonry. In this report, the experimental study which was carried out by Panizza et al. (2009) about the bond-slip behaviour of CFRP and GFRP laminates on brick masonry were briefly summarized. Based on the experimental results and the proposed bond-slip equations, finite element analysis of the test specimens were carried out. Comparison of the results obtained from different finite element models were made, they are: (1) coarse mesh versus fine mesh, (2) exponential bond-slip versus bilinear bond-slip and (3) FRP with concentrated fibre property versus FRP with distributed fibre property. The finite element results were also compared with the results obtained from the analytical solution proposed by Yuan et al. (2004). With the stiffness of FRP assigned as the average value of stiffness obtained from the test, the results obtained from both finite element method and analytical solution compared well with the test results in term of both maximum load and deflection. Parametric studies were carried out based on the analytical solution for different bond length and width ratio of FRP to brick. It is found that the minimum required bond length for the current CFRP and GFRP specimens studied are about 70 mm and 59 mm, respectively. When the bond length is longer than the minimum required bond length, increasing the bond length does not increase the maximum load capacity significant, however, the maximum deflection increases with increasing bond length. For the current specimens studied, the width ratio of FRP to brick does not have significant affect to the maximum load capacity and deflection, especially for specimen with lower stiffness ratio of FRP to brick