Characterization of mechanically enhanced FRP bonding system

Despite extensive research on externally bonded fiber-reinforced polymer (EB-FRP) for rehabilitation of concrete structures in the past two decades, the industry has been slow to embrace the technology owing to some difficult problems that are yet to be resolved fully. Among these, premature debonding is one of the critical problems. Since the tensile strength of concrete is inherently low and unreliable (in the long term), EB-FRP by surface adhesion might not be the final solution; augmentation of the interfacial bond by mechanical fastening may be unavoidable. To this end, the first author proposed a bond augmentation system, hybrid-bonded FRP (HB-FRP), where a special type of mechanical fasteners are used to enhance the interfacial bond. Although the HB-FRP system has been experimentally shown to increase bond strength several fold, effectively overcoming the debonding problem, there has been no systematic theoretical study of the system. In this paper, HB-FRP joints are characterized through experimental testing and analytical modeling, leading to a theory for design and construction of the HB-FRP system.