Study On Flexural Behavior For Partially Prestressed Concrete Beams With FRP Tendons

Fiber Reinforced Polymer(FRP) tendon, a new advanced composite material, is formed through pultrusion of epoxy-impregnated reinforced fibers. FRP tendons have many advantages such as lightweight, high strength, corrosive resistance, fatigue resistance, and so on. However, since its stress-strain relationship is linear elastic without the yield point like steel bars, the mechanical performances and energy dissipation capacity of the beams reinforced with FRP tendons are unfavorable under the ultimate state. To eliminate the above mentioned shortcomings, the partially prestressed concrete, which combines the prestressing FRP tendons with ordinary steel bars, is adopted. In order to enhance the corrosion resistance of steel bars, the epoxy coated ones are used as non-prestressing reinforcement.In this paper, 18 partially prestressed concrete beams were tested, including 10 post-tensioned bonded beams with Aramid Fiber Reinforced Polymer(AFRP) tendons and 8 post-tensioned unbonded beams with Carbon Fiber Reinforced Polymer(CFRP) tendons. And the epoxy coated steel bars were used as non-prestressing reinforcement in all 18 beams. The full-range experiment was conducted through concrete cracking and cracks development till the failure of beams under the action of one-third loading. The items measured during the experiment included loads, deflections, top and side strains of beams, stress increments of unbonded CFRP tendons, crack widths, and so on. As a result, the cracking load, section strains distribution, cracks growth and distribution, deflection growing, as well as ultimate load-carrying capacity were abtained. On the basis of analysis of the experimental data, the main research and achievements are as follows:1. In order to improve the performance of crack, deflection and flexural load-carrying capacity of concrete beams prestressed with FRP tendons, the design plan of the combined reinforcement of prestressing FRP tendons and ordinary epoxy coated steel bars is carried on in this paper. The experimental results show that the ductility and energy dissipation capacity of such beams are nearly as good as the post-tensioned partially prestressed concrete beams with steel strands.2. The relaxation loss of φ 8 CFRP tendons made in China was measured, and the formula of linear relationship between CFRP relaxation losses and logarithms of time was...