Flexural behavior and deformability of fiber reinforced polymer prestressed concrete beams: Fid-Bau Portal

Flexural behavior and deformability of fiber reinforced polymer prestressed concrete beams

Zou, P.X.W.

After a brief review of the ductility and deformability indices currently used in the design of concrete beams reinforced or prestressed with steel or fiber reinforced polymer (FRP) tendons, a new definition of a deformability index (factor) for prestressed concrete beams is proposed. The new factor is defined in terms of both a deflection factor and a strength factor. The deflection factor is the ratio of the deflection at failure to the deflection at first cracking, while the strength factor is the ratio of the ultimate moment (or load) to the cracking moment (or load). The proposed deformability factor appears to be a suitable measurement of the deformability of concretew beams prestressed with either FRP tendons or steel tendons. From the results the following conclusions can be drawn. The conventional ductility index for concrete beams with steel reinforcement is not suitable for beams with FRP reinforcement since FRP does not have a yield point. The energy stored in the concrete beams prestressed by FRP is mainly elastic (60 % or more) up to failure and the inelastic energy absorption is relatively low. Hence the use of the ratio of total energy to elastic energy as the ductility index for beams prestressed by aramid fibre reinforced polymer (AFRP) or carbon fibre reinforced polymer (CFRP) is almost a constant and does not distinguish between beams of different deflection and deformability. Using the deformability factor as the ratio of the deflection at the ultimate limit state to the deflection of the equivalent uncracked section gives a reasonable indication of deformability for beams prestressed with FRP.