High-speed Railway, Large Span Steel Truss Cable-stayed Bridge Seismic Response And Shock Absorption Analysis

In recent years, large-span cable-stayed railway bridges have been greatly developed and widely applied in China. Although much research on dynamic performance of large-span cable-stayed bridges has been done, there is little analysis on the seismic performance of railway special cable-stayed bridges by far. And many difficult problems haven't been solved, such as the train running performance when the earthquake occurs, the reasonable seismic isolation measures, etc. On this level, it is very necessary to study the seismic response and explore effective isolation measures of this kind of bridge, according to its structural features.Based on the Yujiang Double-line Cable-stayed Bridge on the Nanning-Guangzhou Railway, a double-line cable-stayed bridge specially used for railways, response spectrum analysis and nonlinear time-history analysis are both carried out to obtain the dynamic characteristics and seismic response of this bridge. Meanwhile, by comparison on the damping parameters of the viscous damper, the damping performance of this bridge is researched in this paper. The main works are as follows:1. Through reading and aggregating the existing files and datum, the development history, the structural characteristics and the significance of dynamic research was expounded. Combined with the violent earthquake examples at home and abroad, it is summarized about the earthquake characteristics, the research status, and the existing problems of the long-span railway cable-stayed bridges. Besides, on the basis of the thought of earthquake-reduction design, the bridge damping system and viscous dampers applied in bridges at home and abroad are introduced in this paper.2. Spatial finite element model of the whole bridge for Yujiang Double-line Cable-stayed Bridge is established by ANSYS software, based on the finite element method of the vibration analysis of cable-stayed bridges. By analyzing and comparing the vibration characteristics of the two FE models, considering the cable's geometrical non-linearity or not, the vibration characteristics of long-span steel-truss cable-stayed bridge are summarized, so that the further study of seismic response and seismic-isolation method could be carried on.3. The minimum number of modes for the response spectrum analysis is obtained by calculating the mode participation mass of this bridge. According to the condition of the bridge site, appropriate response spectrum is selected. Then the consistent excitation response spectrum analysis was completed under five different load combinations, and the seismic responses under two probability levels (PI and P2) is checked respectively.4. The modified E1-Centro wave is choosed to stimulate this bridge according to the real condition of bridge site. The time-history responses of Yujiang Double-line Cable-stayed Bridge under design earthquake are calculated considering the factors such as vertical excitation, phase difference effect (different velocity of travelling wave) as well as cable's geometrical non-linearity, and the influence law of these factors are discussed.5. The vibration reduction analysis of this bridge was carried out by setting viscous dampers between the pylon and the main girder. Besides, the influence on the seismic reduction effect of some parameters of viscous dampers was discussed, including the damping coefficient and speed index, which could provide some useful reference for the seismic-isolation design of the railway cable-stayed bridges in the future.