Fatigue life-based design of RC beams strengthened with NSM FRP

A comprehensive prediction and design model is presented in this paper for the fatigue life of reinforced concrete beams strengthened with near-surface mounted (NSM) fiber reinforced polymer (FRP) composites. A previously developed cohesive model is adopted and validated followed by an investigation of effects on the fatigue performance due to various important design parameters. The bond strength, reinforcement ratio of NSM reinforcement and steel rebar are found to affect the most in improving the fatigue crack behavior and fatigue life of strengthened beams, while the improvement by yielding stress of rebar, concrete compressive strength and Young's modulus of NSM reinforcement are less significant. Finally, a fatigue life-based design method is proposed for NSM-strengthened reinforced concrete beams, where fatigue life coefficients are incorporated in the proposed fatigue life design equations along with recommendations such as limiting the fatigue-related strain of the NSM reinforcement to avoid debonding failure under fatigue. The proposed design equations show satisfactory precision in comparison with several existing experimental studies.