Seismic Response Analysis Of Cable-Stayed Bridge Considering Deep Water Action

With the rapid development of technology and economy, long-span bridges have been applied more and more widely, because of the irreplaceable role in traffic, The deep-water bridges also appear more and more frequently. As a result, the inter-action of the bridge and water under seismic affect has to be considered in the design.The bridge and water appear coupled vibration under seismic action, the vibration of the pier will affect the vibration of the surrounding water bodies, and water bodies vibration can adversely affect the dynamic characteristics of the pier and response. According to the existed literatures, a few articles are related to study on the seismic response of the deep water pier. In this thesis, the following research is conducted:For the seismic response of the deep-water pier, the Morison equation added mass method, Westergarrd equation added mass method and fluid-structure interaction have been discussed and compared. Research found that the presence of water body will not only reduce the natural frequency of the structure also increase the seismic response. Compared the three methods, Morison added mass method gets the results a bit more in general, judging from the curve trend, fluid-structure interaction relative to the other two methods are more accurate, but also more regularity. The impaction on bottom shear generats by water depth is greater than the impaction on bottom bending moment.On this basis, using Fengjie Yangtze River Bridge as an example, Morison added mass is selected. Anhydrous,33%of full water level,67%of full water level, and full water level of four finite element model are modeled with the finite element software ADINA. Earthquake time history from the transverse direction and longitudinal directions is calculated, conclusion of seismic response of cross-bridge is similar with the single pier’s. Pier displacement, moment and shear of the end of the pier increases when water affected. And seismic response increases as the water depth increases. But because of cable-stayed, increasing margin is less than single pier’s. Water has the greatest impaction on shear at the end of the pier. Earthquake time history of every index is almost the same in different conditions. The cross-sectional shear gets greater when closer to abutment. Cross-sections of the two different main piers, shear of water condition is greater than the shear of anhydrous condition. The gap gets greater when closer to abutment. Bridge vibration is more complex with the longitudinal bridge seismic waves. But overall, displacement of the main beam and main tower decreases while shear and moment of the bottom of piers increase with increasing water depth. Difference of earthquake time history curve of every index appears after8second, but the trend is broadly consistent. The moment gets greater when closer to abutment, and moment of water condition is greater than the moment of anhydrous condition, and The gap gets greater when closer to abutment. Shear from the tower towards the pier decreases firstly and then increases. Cross-sections of the two different main piers, shear of water condition is greater than the shear of anhydrous condition.