Long-Term Deflections of Reinforced Concrete Beams Externally Bonded with FRP System

External bonding of fiber-reinforced polymer (FRP) composite laminates to the tension soffit of reinforced concrete beams has become a popular method for flexural strengthening. However, the long-term performance of FRP-bonded beams under service loads is still a concern. This study was therefore aimed at investigating, both analytically and experimentally, the long-term deflection characteristics of FRP-bonded beams under sustained loads. Nine reinforced concrete beams, six of which were externally bonded with glass FRP composite laminates, were subjected to sustained loads for 2 years. The test parameters were the FRP ratio and sustained load level. The long-term deflections of the beams were reduced 23 and 33% with a FRP ratio of 0.64 and 1.92%, respectively. The total beam deflections were accurately predicted by the adjusted effective modulus method, and overestimated by about 20% by the effective modulus method.