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Strengthening Prestressed-Concrete Girders with Externally Prestressed PBO Fiber Reinforced Polymer Sheets

This study aims at developing an innovative strengthening system with externally bonded prestressed PBO (short for Polypara-phenylene-Benzo-bis-Oxazole) fiber reinforced polymer (PFRP) sheets, which present equal or higher strength and stiffness in comparison with high strength type of carbon fiber reinforced polymer (CFRP) sheets and great performance in energy absorption superior than other fiber reinforced polymer (FRP) sheets such as aramid and carbon FRP sheets. An experimental program was carried out to confirm the strengthening effects on load-carrying capacity, stiffness characteristics, ductility, and resistance of crack opening of prestressed concrete girders. The main parameters studied are the prestress level, the number of PFRP sheet layers, and resin impregnation of PBO fibers before or after sheet prestressing. An analytical study is also performed in order to investigate the flexural behavior of PC girders strengthened with prestressed PFRP sheets.