Oil damper with variable stiffness for the seismic mitigation of cable-stayed bridge in transverse direction

Abstract

Stiffness in the transverse direction is a key issue for cable-stayed bridges. Moreover, the stiffness requirements for wind resistance and seismic isolation are in opposition. To solve this problem, a novel oil damper with variable stiffness (ODVS) is developed in this study. The damper consists of a hydraulic cylinder and overflow valves, and can be installed between deck–tower and deck–pier connections in the transverse direction. The ODVS exhibits high stiffness to resist wind load in service conditions, and low stiffness to isolate the deck under earthquake conditions. The ODVS can be designed as a low-stiffness, high-damping damper, and its mechanism is explained. A hysteretic model of the ODVS is developed and validated through sinusoidal excitation tests. The seismic performance of the ODVS is compared with that of triangular-plate added damping and stiffness (TADAS). The numerical results show that the ODVS has better performance in decreasing the transverse displacements at the end of the deck because of its low stiffness.