Experimental Evaluation of Bent FRP Tendons for Strengthening by External Prestressing

This paper presents an experimental study conducted on the static performance of bent fiber-reinforced polymer (FRP) tendons for external prestressed strengthening. First, the tension strain and compression strain at the surface of FRP tendons attributable to pure bending were experimentally tested and compared with the theoretical calculated values. Then, the load capacities of bent FRP tendons, under different bending angles and bending radiuses, were tested using a customized testing device. To improve the utilization of FRP tendons, the effectiveness of the hybrid FRP tendon, as a replacement for a pure FRP tendon, was also tested. In addition, a rolling friction deviator was developed to reduce the friction loss and lessen the damage on the FRP surface. The effectiveness of the device was also tested and verified. The test results indicated that when the ratio of the FRP tendons and bending radiuses (r/R) reached 0.01 during the pure bending test, the generated tension strain at the tendon surface was greater than 30% of the ultimate tension strain. The hybrid FRP tendons showed higher load capacity retentions than did the pure FRP tendons under the same conditions. The friction loss was significantly reduced when the rolling friction deviator was used.