Study On Ductility Of Prestressed CFRP Tendons Concrete Beams

Experimental and theoretical studies are conducted to investigate ductility and deformation behavior of concrete beams prestressed with CFRP tendons. The following two parts are mainly stated: static behavior of partially boned CFRP concrete beams under monotonic loads; seismic behavior of bonded CFRP concrete beams under low reversed cyclic loading. Note that the seismic behavior of bonded CFRP concrete beams is firstly studied in the world.The paper is inclusive of the following five parts:Firstly, six partial bonded concrete beams prestressed with CFRP tendons are tested under monotonic loads. The failure modes, ultimate stresses of prestressing tendons, ultimate load-carrying capacity, ductility, deformation and crack width of this kind of beams with varying unbonded length are systematically investigated. Studies show that ultimate load-carrying capacity of these beams increase with decreasing unbonded length of prestressing tendons. Tests show that the relationship between the two is basically linear. Given that the other conditions are the same, the ultimate load-carrying capacity of partial bonded CFRP beams is about 20% lower than that of the fully bonded prestressed beams. Tests also show that ductility of the partial bonded CFRP beams increase about 20-40% in comparison to the fully bonded prestressed CFRP beams.Secondly, full range analysis of partially bonded CFRP prestressed beams are simulated by using ANSYS. The analytical results of the prestressed beam specimens, such as ultimate load-carrying capacity, deflection as well as stresses of prestressing tendons and steel rebars are in good agreement with the experimental results. The parameter analysis of this kind of beams is then carried out, providing principles for the theoretical analysis.Thirdly, low reversed cyclic loading tests are conducted to investigate failure modes, characteristic loads, hysteretic model, deformation restoring capacity, displacement ductility, stiffness degradation and energy dissipation capacity of six bonded CFRP prestressed concrete beams. Influences of differential jacking stresses, reinforcement ratios and partial prestress ratios (PPR) are on loading capacities of members are analyzed. Studies show that hysteresis curves of bonded prestressed CFRP beams are far less full than theses of the beams prestressed with steel strands.