The study of the bond stress-slip relationship of FRP (fibre reinforced polymer) adhered to concrete has been a key point to understand the bond behaviour of externally bonded reinforcement (EBR) and near surface mounted (NSM) systems. Researchers have made an effort to determine bond-slip relationships through experimental and analytical/numerical methods, although they have not obtained univocal results.
The area under the bond stress-slip relationship, representing the fracture energy, is one of the main parameters to make bond strength predictions. The fracture energy may be divided in two parts: elastic and softening contribution. These parts act both in a different way in predicting the failure load and the effective transfer length.
In this paper the influence of the shape of the bond stress-slip relationship on the prediction of the bond strength and transfer length is investigated. Hereby, a comparison is made between the bilinear bond stress-slip relationship (linear elastic ascending branch-linear softening branch) and the elastic-exponential bond stress-slip relationship (linear elastic ascending branch-exponential softening branch)
