Seismic Energy Dissipation Of Bridges Using Fluid Viscous Dampers

Fluid viscous dampers are commonly used as passive energy dissipation device for seismic protection of structures. The mechanical parameters of the damper include the damping coefficient and velocity exponent. If the velocity exponent is other than unity, the damper will demonstrate nonlinear behavior. For a specific bridge, the response reduction efficiency of the damper relies on the selection of the damper's parameters. According to the complexity degree of the bridge, different analytical schemes were adopted in this paper.For the long span bridges, such as the cable-stayed bridge and suspension bridges, a fully developed finite element model of the bridge is suggested for the passive control analysis, because of the complexity of the dynamic properties of such bridges. Thus, a detailed finite element model with SSI effect and nonlinear dampers were developed, and the suitable values of the soil spring were proposed. From the view of time, a detailel dynamic analysis is usually allowed for such bridges because of the need of long duration both in design and in construction. A practical cable-stayed bridge was taken as an example, and the influence of dampers'parameters on the key response of the bridge was analyzed, and the reasonable parameters of the dampers were obtained via the parametric analysis. The control efficiency of the dampers was discussed for various earthquake excitation levels.For the girder bridges, the dynamic behavior can be characterized as finite mass-spring system. For instance, the current highway girder bridges are commonly continous girder bridges with the laminated rubber bearings, and such bridges can be treated as a two-DOF simplified system. Moreover, the owners of such bridges often want to get the cost of the dampers in the early stage so that they can be incorporated into the engineering budget as early as possible. Thus, in this paper, the state equation of the simplified dynamic system was first derived, and core code to solve the equation was developed by using Matlab, and then a GUI was designed by using GUIDE—a GUI development tool. A visualized computer program, named VDSPHB (Viscous dampers for seismic protection of highway bridges), was finally developed, which has the function of the optimal selection of dampers'parameters and shows higher analytical efficiency than the common FE software. A practical highway girder bridge was taken as a demo, and the usage instructions were discussed. The control efficiency of the damper was discussed for varouis earthquake excitation levels.