Strengthening Effects of RC Flexural Members with FRP Sheets Affected by Adhesive Layers

Fiber reinforced polymers (FRP) can be bonded to the tension face of concrete structures to enhance the structural performance via a thin layer of adhesive and this has been confirmed to be a very promising rehabilitation method worldwide. Proper understanding of effects of the adhesive properties on strengthening of RC members with FRP sheets is very essential and urgent to the FRP bonding technique. Recently, some interesting experiments have been conducted and it is found that the FRP strengthening effects can be improved by adding flexible layer or rubber modifier to the epoxy adhesive for some cases. To clarify these experimental phenomena, in this study, a finite element analysis based on nonlinear fracture mechanics is performed to investigate effects of the interfacial mechanical properties such as stiffness, local bond strength and fracture energy on the structural performance of FRP-strengthened RC beams. Through conducting parametric study on the strengthened RC beam with two possible crack patterns accompanied bydebonding failure, it is concluded that the structural load-carrying capacity is only governed by the interfacial fracture energy. This study provides a good implication for future practical application.