Prestressed FRP sheets for poststrengthening reinforced concrete beams

Four large-scale reinforced concrete beams were constructed and tested to investigate the effectiveness of external poststrengthening with prestressed fiber reinforced polymer (FRP) sheets. One of the beams served as a control specimen, another was strengthened with nonprestressed carbon FRP sheets, and the remaining two were strengthened with prestressed carbon FRP sheets. Presented is a method of prestressing multiple layers of the carbon fiber sheets during the application process and the experimental and analytical behavior of the beams under quasi-static loading. Comparisons are made between the control beam, the beam reinforced with nonprestressed carbon FRP sheets, and the beams strengthened with prestressed sheets. Serviceability and ultimate conditions are considered in the theoretical prediction of beam behavior, including the effects of multiple layer prestressing and external loading. The bonding of prestressed FRP sheets to the tensile face of concrete beams improved both the serviceability and the ultimate behavior of the reinforced concrete beams.