Seismic behavior of precast segmental bridge columns reinforced with hybrid FRP-steel bars

Abstract

Precast segmental bridge columns (PSBCs) are a key component in accelerated bridge construction. In order to advance the technology and improve their seismic resistance, this paper presents research on an innovative PSBC system that incorporates both fiber-reinforced polymer (FRP) bars and steel bars as longitudinal reinforcement. The system, which is referred to as an FRP-steel reinforced PSBC (FSR-PSBC), utilizes hybrid FRP-steel bars to increase the post-yield stiffness and to decrease the post-earthquake residual drift. The first part of the paper presents the results of cyclic loading tests of large-scale PSBC systems. Several important trends were observed. (1) Compared to traditional steel-reinforced PSBCs, the post-yield stiffness ratio of the FSR-PSBC system increased by up to 93%, while the residual drift ratio reduced by 68% at a large drift of 4%. (2) The FSR-PSBC specimens exhibited energy dissipation capacities comparable to their steel-reinforced counterparts. (3) Carbon FRP bars of the hybrid reinforcement significantly contributed to the increase of the post-yield stiffness and self-centering ability of the FSR-PSBC system. The second part of the paper presents a design-oriented analysis of the test results. Three possible compression-bending failure modes of the FSR-PSBC system are proposed and a desired ductile failure mode was established. Then, three damage limit states within the ductile failure process were defined in terms of the responses of materials, displacement and residual drift. The analysis presented paves the way for the development of a performance-based seismic design method for an FSR-PSBC system.