Modeling of debonding and fracture process of FRP-strengthened concrete beams via fracture mechanics approach

Fiber-reinforced polymer (FRP) composite materials have been widely used in the field of retrofitting. To estimate their service reliability, it is necessary to conduct a theoretical analysis of FRP-strengthened concrete beams. In this paper, a fracture mechanics approach is presented to model the cracking behavior of and interfacial debonding process in FRP-strengthened concrete beams. The K-superposition method is adopted to calculate the net stress intensity factor at the crack tip. After the validity of the proposed approach is verified with experimental results obtained from the literature, the effects of various factors on the load-bearing capacity and crack growth resistance of FRP-reinforced concrete beams are quantitatively evaluated. It is found that the first peak load increases as the beam height and compressive strength of concrete increase or the ratio of the initial crack length to beam height decreases, whereas the second peak load is an increasing function of the FRP sheet thickness and width. It is also found that the crack growth resistance increases with an increase in ratio of the initial crack length to beam height and FRP sheet thickness and width but is seldom influenced by the beam height and compressive strength of concrete.