Seismic behavior of CFRP-steel hybrid prestressing prefabricated bridge piers with thermoplastic GFRP bar reinforced concrete segments

This paper aims to investigate the effects of a hybrid prestressing system composed of CFRP bars and steel bars on the seismic resilience of a prefabricated bridge pier with GFRP-reinforced concrete segments in detail. Combining the experimental results, a series of parametric numerical analyses was conducted to further investigate the effects of various factors on the hysteresis behavior of prefabricated segmental piers. The analysis results indicated that 1) for the prestressing steel bars, the increasing reinforcement ratio had a more significant influence on enhancing the stiffness and ultimate bearing capacities of piers compared to the increase of prestressing degree; 2) for the prestressing CFRP bars, the increasing reinforcement ratio and prestressing degree were positive for enhancing the stiffness and ultimate bearing capacities of piers, but a critical value for the prestressing degree should be set to avoid the sudden failure of piers in a strong earthquake due to the fracture of CFRP bars; 3) the limited total axial compression ratio (less than 0.3) and the higher-grade concrete were beneficial to ensure the seismic resistance of novel segmental piers; 4) the application of bonded prestressing steel bars could significantly affect the reloading and unloading curves' stiffness, increasing the energy dissipation capacity but reducing the self-centering capacity of piers. Furthermore, the four force stages of prefabricated segmental piers under horizontal force on the pier top were analyzed based on the above results, and the bearing capacity and rotational angle calculation formulas of the bottom segment at different stages were established, respectively. Thereby, a design method of piers considering the seismic requirements was proposed.