Research on Seismic Performance of The Pre-stressed Rocking Bridge Pier with Variable Friction Self-centering Damper System

Objectives: In order to enhance the hysteretic energy dissipation capacity of the unbonded prestressed concrete swing abutment bridge under seismic action, a study on the reliability of a variable friction self-resetting damper to improve the energy dissipation capacity of the unbonded prestressed concrete swing abutment bridge is proposed. Methods: The force-displacement relationship of the enhanced rocking bridge pier with variable friction self-resetting dampers was calculated by using theory and finite element method. The consistency of the results obtained by the two methods was evaluated. Three parameters, namely the initial tension stress of the prestressed tendons, the stiffness of the lateral compression spring of the dampers, and the friction coefficient of the dampers, were analyzed. The influence of these parameters on the seismic performance of the enhanced rocking bridge pier system with variable friction self-resetting dampers was studied. Results: When only the initial tensioning stress of the prestressed steel strands is changed to increase it from 800 MPa to 900 MPa, the maximum restoring force increases by 3.5%, the equivalent damping ratio at the maximum displacement of the structure decreases by 5.4%, and the energy consumption increases by 4.3%. When the initial tensioning stress is changed from 900 MPa to 1000 MPa, the maximum restoring force increases by 5.4%, the equivalent damping ratio at the maximum displacement of the structure decreases by 79%, and the energy consumption decreases by 70%. When only the lateral compression spring stiffness of the damper is changed to increase it from 80 kN/mm to 100 kN/mm, the maximum restoring force increases by 3.2%, the equivalent damping ratio at the maximum displacement of the structure increases by 2.7%, the stiffness after yielding increases by 1.7%, and the energy consumption increases by 0.51%. When the spring stiffness of the damper is changed from 100 kN/mm to 120 kN/mm, the maximum restoring force increases by 2.2%, the equivalent damping ratio at the maximum displacement of the structure increases by 0.27%, the stiffness after yielding increases by 1.8%, and the energy consumption increases by 2.5%. When only the friction coefficient of the damper is changed to increase it from 0.2 to 0.23, the maximum restoring force increases by 0.23%, the equivalent damping ratio at the maximum displacement of the structure decreases by 0.6%, the energy consumption value increases by 3.6%, and the residual displacement increases by 9.9%. When the friction coefficient of the damper is changed from 0.23 to 0.25, the maximum restoring force increases by 0.87%, the equivalent damping ratio at the maximum displacement of the structure decreases by 0.2%, the energy consumption value increases by 0.67%, and the residual displacement increases by 5.5%. Conclusions: When the initial tension stress applied to the prestressed tendons is 0.45 times their own yield strength, the spring stiffness of the damper is 120 kN/mm, and the friction coefficient is 0.25, the system has good energy dissipation and self-centering performance. The research results are relatively reliable.