Researching On The Vibration Characteristics Of Bridge Pier-water Fluid-structure Interaction Caused By The Effect Of High-speed Train

With the rapid development of China’s high-speed rail system, more and moreconstructions of wading railway bridge is inevitable. And the depth of these wading railwaybridge continue to creat new record. In the current wading railway bridge, the deepest depthof the bridge pier submerged has reached168m wich equivalents to the height of56storeys.The bridge pier in deep water will produce vibration and deformation in the case of complexexcitation force generated by high speed train, and it will cause the vibration of the wateraround. The vibration of the water will react on the bridge pier, this action and reaction isalways accompanied by the passing of train, and changes the vibration and deformation of thebridge pier. As the key support of the bridge upper structure, it will lead to disastrousconsequences once the damage occuring of the bridge pier. So, it is beneficial to the safety,stability and usability of the bridge structure’s design, construction and maintenance underthe analysis of the effect by water on the bridge pier’s static characteristic and dynamicvibration caused by high speed train. In this paper, analyzed the static characteristics of theindependent bridge pier structure (mainly the high bridge pier) in the water, and focused onthe analyzing of the effect by water on it’s vibration characteristics of the independent bridgepier structure under high speed train, based on consulting a large number of calculationmethods and principles of domestic and foreign about the fluid-structure interation, and thedocuments related to the vibration characteristics of fluid-structure interaction. Mainly donethe following analysis and research:⑴Used ANSYS finite element software to build the bridge pier model and water-bridgepier coupled finite element model. Then analyzed the static and dynamic characteristics ofbridge pier.⑵W hen analyzing the static characteristics of bridge pier, with creating a bridge piermodel wich in different depth water by ANSYS. Then calculating the variation of bridgepier’s natural vibration frequency under the different depth of water. There is no obvious changes of bridge pier’s natural frequency when the water depth is shallow(less than50%height of bridge pier). The bridge pier’s natural frequency is reducing significantly with thewater depth increasing when the water depth is large(more than50%height of bridge pier).And analyzing the influence on the bridge pier’s natural frequency by the geometric size ofbridge pier in the case of anhydrous and full-water.⑶W hen analyzing the dynamic characteristics of bridge pier, creating a bridge piermodel by ANSYS, and loading at the bridge pier top with the excitation force caused by trainwith the speed of60m/s,70m/s,80m/s,90m/s. And then calculating the variation of thebridge pier top’s displacement and acceleration in x, y and z direction. The maximumdisplacement of bridge pier top in x, y and z direction is decreasing with the increasing of thetrain’s speed, and the maximum acceleration is increasing with the increasing of the train’sspeed.⑷A nalyzed thevariation of bridge pier top’s displacement and acceleration in x, y and zdirection(horizontal, longitudinal and vertical) under different depth water by building thebridge pier-water fluid-soild coupling finite element model with ANSYS, and loading theexcitation force caused by train at the bridge pier top. In the case of different speed of train,when the water depth is less than80%of the bridge pier’s height, the maximum displacementof bridge pier top has a decreasing trend with the increasing depth of water, especially whenthe speed is low. The maximum displacement of bridge pier top is increasing with theincreasing depth of water when the water depth is more than80%of bridge pier’s height.There is no obviously change of the top of bridge pier’s maximum acceleration in x and ydirection with the increasing of the water depth when the water depth is less than90%ofbridge pier’s height. But, when the water depth is more than90%of bridge pier’s height, it isobviously decreased on the top of bridge pier’s maximum acceleration in x and y direction.The maximum displacement and acceleration of bridge pier top in z direction has no changewith the changing of water depth.⑸Analyzed the variation of the full-water bridge pier top’s maximum displacement andacceleration by changing the slenderness ratio of bridge pier at different speeds. Themaximum displacement of bridge pier top in x and y direction is increasing dramatically withthe increasing of slenderness ratio. There is a small increase in z direction. But, the maximumacceleration of bridge pier top in three directions is reducing with the increasing ofslenderness ratio. And all of the variations have nothing to do with the train speed.