This paper presents a model for predicting the cyclic response of Prestressed Concrete (PC) beams with Fiber-Reinforced Plastic (FRP) tendons bonded to concrete. The model considers the main phenomena that an earlier part of the study emphasized as important for PC beams with FRP tendons and untensioned reinforcing bars and stirrups made of either steel or FRP. The ductility displayed by a set of doubly flanged "T" beams prestressed with FRP tendons and reinforced with untensioned longitudinal bars and stirrups made of either FRP or steel, is then estimated using load-displacement as well as moment-curvature responses obtained by the model. By means of their comparison with equivalent frameworks differing in 1) either FRP in lieu of steel, but not in the other characteristics, 2) or height, but not in the load bearing capacity, considerations on the ductility displayed by FRP prestressing systems can be developed. Ductility was evaluated according to an index μ applicable to beams with steel (μ~S) as well as FRP reinforcement (μ~F). The results systematically and convincingly demonstrated that prestressing with FRP instead of steel has negative effect on ductility (i.e., μ~F < μ~S). Nevertheless, if the ratio of μ~F to μ~S is evaluated for the whole beam -although it remains lower than 1-a greater value results as for the section. In addition, ductility was evaluated according to special criteria which accounts for inelastic energy, thus, providing a better basis of comparison than μ. The model enabled the correlation of the ductility performances with the modes of failure and mechanical and geometric parameters of the framework. As a result, improved methods were derived to enhance ductility. It is proved that, with FRP reinforcement, height has opposite influence on ductility than with steel reinforcement. In addition, it is demonstrated that to drive the mode of failure consists of an effective tool for improving ductility without producing negative effects in the load bearing capacity and ultimate deflection.
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