Damage Assessment and Ductility Evaluation of Post Tensioned Beams with Hybrid FRP Tendons

The study presented in this article concentrated on investigating the ductility and characterization of damage in concrete beams post tensioned with hybrid carbon-glass fiber-reinforced polymer (HFRP) composites. The investigation included an approach for design of flexural members with HFRP tendons and characterization of damage, load deformation response, ultimate strength, and failure modes. Direct tensile tests of hybrid FRP rods in a previous study had indicated elastoplastic response, enhanced ductility, and increased strain capacity. In this context, the current study focused on design and fabrication of post tensioned beams using glass or steel rebars for partial prestressing. All the beams were tested in flexure under four-point bending configuration. Results of the study are presented in terms of ductility index and enhanced load-deflection response in comparison with the conventional FRP materials. Damage characterization involved evaluating the specific features of the acoustic emissions for detecting the elastoplastic transition in the hybrid tendons. The method involved use of a high-resolution fiber-optic interferometer for detection and separation of acoustic emissions. By using the time domain response, it was possible to spatially localize the damage at various stages of the loading. Spectral energy of the acoustic emissions facilitated separation of carbon and glass fiber fractures.