Bond Strength Model for CFRP Strips Near-Surface Mounted to Concrete

Abstract

This paper is concerned with the development of an accurate bond strength model for carbon-fiber-reinforced polymer (CFRP) strips near-surface mounted (NSM) to concrete where debonding occurs as a result of cohesion failure in the adjacent concrete. Based on an existing analytical solution and the fracture energy equation recently developed by the authors, a bond strength equation is first proposed for NSM CFRP strip-to-concrete bonded joints with a sufficient bond length (i.e., the bond length exceeds a threshold value referred to as the effective bond length). The influence of an insufficient bond length on the bond strength is next examined through a parametric study conducted using a beam-spring numerical model in which a bond-slip model recently proposed by the authors is incorporated. Based on the numerical results, expressions are formulated for the effective bond length and the bond-strength reduction factor for insufficient bond lengths. The combination of these equations leads to a new bond strength model for NSM CFRP strip-to-concrete bonded joints. The predictions of the proposed bond strength model are compared with the results of 51 test specimens collected from seven existing studies and the predictions of the only existing bond strength model for such joints. These comparisons indicate that the proposed model is accurate and superior to the existing bond strength model, particularly for joints with insufficient bond lengths. The proposed bond strength model, because of its accuracy and simplicity, can be readily incorporated in design codes and guidelines.