Contrastive Analysis Of Seimic Responses Of Cable-stayed Bridge In Deep Water

Now along with the high-speed development of our country's economy.China's transportation industry is also booming,and bridge as an integral part of transportation chain is in fast development,too.Under the action of earthquake,the bridge located in the deep water will vibrate under seismic excitation,and then drive the water surrounded pier vibrate,and the vibration of the water will affect the dynamic characteristics of bridge pier,also is the coupled vibration between bridge and water.According to the existing literatures,the methods of dynamic water pressure under the action of earthquake are similar.The study of large deepwater bridge is less,only few of literatures study for deep water piers under the action of earthquake dynamic response.So this article do the study for the seismic response of deep water piers and the large cable-stayed bridge.As follows:Discuss the equation calculation method of Fluid Acoustic Element Method,the Added Mass Ratio Method and Morison about dynamic water pressure of bridge pier under earthquake excitation.Compared different methods calculated the first-order frequency and reducing rate of the first-order frequency in bridge piers of different section size of square cross section and circular cross section.Analyzing the displacement of pier top,force reaction and reaction moment of pier base under dynamic water pressure.Contrast the results,natural frequency of piers increase with the increase of section size.The reducing rate of the first-order frequency reduce gradually and and the amplitude of reducing also gradually narrowed.In the presence of dynamic water pressure,displacement of pier top,force reaction and reaction moment of pier base are both increased,and Increasing amplitude decreases gradually with the increase of pier cross-section size.The influence of dynamic water pressure on reaction force is much bigger than reaction moment.The result calculated by Morison equation is more conservative,with the increase of section size,the methods of Added Mass Ratio and Fluid Acoustic Element are more practical.To start,based on the Fengjie Yangtze river bridge as the engineering example,using these three methods and with the help of ANSYS to establish element model and entity element model of a cable-stayed bridge.Using the seismic waves vibrated along the longitudinal direction of bridge to do time history analysis under anhydrous conditions and water condition.According to the calculation,in the condition of deep water,water has a little influence on the dynamic characteristics of large bridges.Because the added mass compared to the quality of the whole bridge is minimal.Water has a greater influence on the bridge dynamic response under the action of the earthquake.The longitudinal displacement of girder and top of tower are increased.The shear force and bending moment of Bottom of tower are significantly increased,and the increment of shear force is greater than bending moment.The shear force and bending moment of pier body change vary with pier height,and compare with the extreme value under no water is increased.Three methods,by contrast,the results of dynamic response calculated by Added Mass Ratio Method are smallest and relatively close with Fluid Acoustic Element Method.Morison's results are biggest and be safe.The results of Fluid Acoustic Element Method are moderate.