CALCULATION METHOD ON SELF-CENTERING AND ENERGY DISSIPATION CAPACITIES OF POSTTENSIONED PRECAST SEGMENTAL CIRCULAR CFDST PIERS

The new posttensioned precast segmental circular concrete-filled double skin steel tubular (CFDST) bridge pier combines the advantages of posttensioned precast segmental pier and composite CFDST member, in such a way to improve bridge resilience and accelerate bridge construction. It aligns with the development trend of seismic resilient bridge. However, balancing the self-centering and energy dissipation capacities of this new bridge pier to ensure its seismic resilience is a critical issue that needs to be addressed in engineering design. Based on the rocking mechanism of the new bridge pier, an energy dissipation factor \lambda _\textED is adopted to represent the influence of the amount of ED bars, the axial load ratio due to dead load and the initial prestressing force on the self-centering and energy dissipation capacities. A finite element model is developed to simulate the seismic performance and is verified by the results of cyclic loading test. Finally, a parametric analysis is conducted to investigate the influence of this factor on the self-centering and energy dissipation capacities. Simplified formulas for the residual drift ratio \theta _\textR and the equivalent viscous damping \xi _\texteq with the variation of the factor \lambda _\textED are proposed through regression analysis and verified by existing cyclic lateral loading test data. The study results show that the proposed formulas provide a design method for optimizing the self-centering and energy dissipation capacities and can be used to guide the design of posttensioned precast segmental CFDST piers.