Seismic Analysis And Optimization Design Of Cable-Stayed Bridge Based On Viscous Dampers

With the national economy development and the continuing progresses of transportation projects, bridges, especially long-span bridge projects, as pivotal projects in social transportation system, are the lifeline of national economy, earthquake disaster relieving, and post-disaster reconstruction. Therefore, ensuring the security and normal use of bridge projects in earthquake is of great social and economic significance.As a typical bridge type in long-span bridge projects, long-span cable-stayed bridge has attracted attention of many scholars both home and abroad in terms of researches on its aseismic performance and seismic isolation in times of earthquakes, especially for rare earthquakes. When fluid viscous damper is applid on a long-span cable-stayed bridge as a passive power dissipation device, it wouldn't contribute to the overall rigidity of the structure, and the primary beam could then be flexible with the live loads including temperature. In times of earthquake it could effectively dissipate the power which is exerted by the earthquake to bring vibration of long-span cable-stayed bridge under contro. Thus viscous damper is a comparatively ideal absorption apparatus for long-span cable-stayed bridges. Songhuajiang Bridge in Lanqi of Jilin is a double tower double cable plane cable stayed semi-floating bridge with a main span of 240m. The bridge is positioned in the area with a maximum seismic intensity of 7 on the Richter Scale, thus it was designed to stand earthquakes of 8 on the Richter scale. This paper adopts it as the practical background to study the aseismic performance and seismic isolation. Main contents are as follows:1) The paper establishes a dynamic finite model for the above-mentioned bridge with finite element analysis software, and analyzed the dynamic features of the bridge to get its vibration features;2) The paper conducts longitudinal dynamic time history analysis over the above-mentioned bridge in E2 rare earthquakes to get the dynamic response in longitudinal earthquake. On such basis the paper applies viscous damper on the bridge and discussed the parameters of the damper, and analyzs the influence of damper coefficient and velocity index to the parts of the structure, the optimal damper coefficient is calculated based on the above measures. With the chosen damper coefficient, the paper analyzes the seismic isolation performance of the damper, and it shows that the viscous damper effectively decreased the displacement of the stiffening beam and the main tower as well as the internal force response. 3) Using the Songhuajiang Bridge as the prototype of the system, the paper analyzed the influence of the structure, main pier height, type of main beam, and settings of auxilliary piers on the seismic isolation of the long-span cable-stayed bridge with progressive transformation study of the structure. It also studies on the rules on the influence on the damper parameter optimization and seismic isolation. Then the paper gets the general rules in viscous damper seismic islation design of the long-span cable-stayed bridge. It would serve for the seismic isolation design of long-span cable-stayed bridges.