Project Title: Predicting Fatigue Service Life Extension of RC Bridges with Externally Bonded CFRP Repairs

Externally bonded CFRP (carbon fiber reinforced polymer) is being applied as a repair technique to extend the useful life and enhance the safety of existing reinforced concrete bridges. The nature of bridge loading means that fatigue loading as well as static strength is an important design consideration. Numerous studies have considered the fatigue performance of RC beams with internal steel reinforcement strengthened with externally bonded FRP (typically carbon fibers, but in some cases glass). The review by Kim and Heffernan (2008) summarizes many of these studies. Concrete beams with externally bonded FRP subject to fatigue loads will most often fail due to fracture of the steel reinforcing bars followed quickly by debonding of the FRP from the concrete (Kim and Heffernan, 2008). When FRP is applied as an external strengthening mechanism, tensile loads are shared between the steel and FRP, and the stresses in the reinforcing steel are lower for a beam with externally bonded FRP than one without. Thus the application of FRP would be expected to extend the fatigue life of the strengthened structure by reducing the level of stress in the reinforcing steel. In their analysis of existing work Kim and Heffernan found that most studies reached this conclusion. The amount of increase can vary widely depending on the specific loading conditions and quantities such as the amount of stee