Effective Bond Length Evaluation of Fiber Implantation Methods in EBR Applications Using Particle Image Velocimetry

The bond strength between fiber reinforced polymer (FRP) laminates and concrete is the main factor affecting the behavior of concrete members strengthened by externally bonded reinforcement (EBR) method. The bond strength depends on several factors, such as surface preparation, concrete strength, FRP stiffness and thickness and effective bond length. According to previous studies, using a bond length longer than the effective bond length, will not increase the connection load carrying capacity. Most existing theoretical models estimate bond strength based on the effective bond length. So, in order to achieve a satisfactory connection, it is important to determine the accurate value for the effective bond length of the lap joint. In this study, in order to evaluate and compare the effective bond length of fiber implantation method and the conventional EBR method, 12 concrete specimens were prepared and tested. Then, the effective bond length and the bond strength of the specimens were obtained by using single-shear pull test and using particle image velocimetry (PIV) method and compared with the existing specifications such as ACI and fib. The results showed that, using fiber implantation method instead of the conventional EBR method, would reduce the effective bond length by 20% and increase the bond strength between FRP and concrete substrate by 34%.