Study On The Damped Energy-dissipated Earthquake-reduction Technique Of Long-span Cable-stayed Bridges

It is well known, in general, that the long-span bridge is the hinge of transportation, which is heavily invested in, used frequently and has important influence on national economy. Once destroyed, it will lead to huge economic lose and heavily influence earthquake disaster reduction and repair of disaster area. So it is very important to adopt the effective seismic fortification measures to insure the safety of the structure in earthquake. The installation of viscous dampers in the long-span bridge can't increase the stiffness of the structure and the deck of the bridge can deform freely because of temperature fluctuation. At the same time, it can reduce the vibration response of the long-span bridge, because viscous dampers can consume a lot of energy created by earthquake and wind. So it is an ideal earthquake-reduction technique for the long-span bridge. Combining with the damped energy-dissipated earthquake-reduction design of the engineering of the South Channel Bridge of HangZhou gulf, This paper has studied some relative research work as following.1 According to the engineering of the South Channel Bridge of HangZhou gulf, this paper has considered two types of transverse boundary conditions, that is, the transverse boundary condition between the girder and the transition piers is free or fixed. The comparison is made in terms of the seismic response of this bridge of two types of boundary conditions. It is shown that the boundary condition has great effect on the seismic response of the cable-stayed bridge. It is also shown that these two types of boundary conditions can't make the displacements and forces in the structure meet requirements economically.2 This paper proposes that transverse viscous dampers are set between the piers and the girder. Effectiveness of viscous dampers on the cable-stayed bridge is studied by the computer program SAP2000N. It's concluded that the use of viscous dampers can drastically reduce transverse displacements, velocities and accelerations on the deck of the long-span cable-stayed bridge. It's also concluded that forces in piers can be coordinated and forces induced in piers, the tower and the girder are reduced, too.3 In this paper, the main design parameters are described. The effect of damping coefficient and velocity exponents on the seismic response of the structure , maximum displacements and forces in the devices and earthquake-reduction effectiveness of viscous dampers are studied. Conclusions obtained can be referenced when having the earthquake-reduction design of long-span cable-stayed bredgs. At last, based on the results obtained, some suggestions about the design of viscous dampers in the long-span cable-stayed bridge are presented.