SEISMIC PERFORMANCE AND CORRESPONDING DESIGN METHOD OF ROCKING SELF-CENTERING BRIDGE BENTS EQUIPPED WITH LEAD-EXTRUSION DAMPERS

To develop the self-centering two-column bents and achieve the seismic damage control, lead-extrusion dampers (LEDs) were selected as the external energy dissipaters, and a rocking self-centering bridge bent system equipped with LEDs was proposed. The seismic performance of this system was studied, and a corresponding design method which was based on the equivalent energy-based design procedure (EEDP) was developed. Initially, the numerical analysis model of RSC-LEDs bridge bent was established, and the simulation method was validated by an existing cyclic test of a RSC bridge bent specimen. Then the effect of LED output force, gravity load of superstructure, prestressing force, areas of unbonded tendon and cap beam-to-column stiffness ratio on the seismic performance of RSC-LEDs bridge bents was studied. 32 RSC bridge bents with different parameters were designed to conduct regressive analysis, and semi-empirical formulas were given to calculate the effective stiffness and yield strength of RSC-LEDs bridge bents. Combining the Chinese seismic code and EEDP, a two-stage seismic design method was proposed for RSC-LEDs bridge bents, and the results show that the obtained semi-empirical formulas can estimate the effective stiffness and yield strength accurately. The RSC-LEDs bridge bents designed by the proposed method can achieve the target capacity curve, and is able to remain elastic under E1 level earthquake. The LEDs start to dissipate energy under E2 level earthquake and the seismic displacement demand can be controlled within a design range.