Behavioral research of concrete beam prestressed with unbonded CFRP tendon

To study stress increment of CFRP tendons, deflection of members and distribution of cracks in concrete beams partially prestressed with unbonded CFRP tendon, four test simple beams were designed and fabricated. In the beams, CFRP tendons were taken as unbonded prestressed tendon, reinforcement were taken as unprestressed tendon. Loaded on two points. Study was carried out based on test data. The following conclusion was obtained: cracks were centered on bended region, increment stress of CFRP tendon was little influenced after concrete crazed. But when unprestressed tendon yielded, deflection of beam and increment stress in CFRP tendon increased obviously, and increment stress of CFRP tendon was influenced by the global reinforcement index. At the same time the computation formula of increment stress at limit state in CFRP tendon were put forward. So we can infer that concrete beam partially prestressed with unbonded CFRP tendon possess good mechanical property, and the test conclusion provides theory foundation for designing and study in these beams.