Seismic Design of a Long-Span Cable-Stayed Bridge with Fluid Viscous Dampers

Abstract

As a passive energy dissipation device, the fluid viscous damper (FVD) is effective for mitigating wind or seismic load-induced vibrations. In this paper, the effects of FVDs for a cable-stayed bridge under randomly generated earthquake excitation are investigated. The FVD is modeled as a simplified Maxwell model, which consists of a linear spring in series with a nonlinear dashpot. The pile is modeled as a beam on the nonlinear Winkler foundation, and the soil–pile interactions are simulated by using continuously distributed hysteretic springs and viscous dashpots placed in parallel. Three random ground motions are generated from the earthquake risk assessment based on the seismotectonics and seismicity analysis of the bridge location. The seismic response of the cable-stayed bridge with FVD considering soil–structure interactions (SSIs) is obtained by solving the equations of motion in the time domain using a direct integration method. Parametric studies are conducted for the two key parameters in the simplified Maxwell model, namely, the damping coefficient C and the damping exponent α. The results indicate that the FVD is very efficient in reducing the displacement response of the cable-stayed bridge and the bending moment of the tower while simultaneously limiting the shear force in the tower. Compared with the linear FVD, the nonlinear FVD has a better performance in reducing the seismic response of the cable-stayed bridge. The maximum displacement response of the deck and the tower, when implementing the nonlinear FVD, could be reduced up to 79 and 77%, respectively, whereas the maximum reduction of the corresponding displacement response with the linear FVD drops to 51 and 50%, respectively. The reduction of the bending moment of the tower using nonlinear FVD could be up to 56%, whereas the maximum reduction of the corresponding response using linear FVD is 40%. After the parametric study, an optimal design of the FVD is chosen and implemented in the final bridge design.