Study On Seismic Isolation Mechanism And Technology Of Elevated Aqueduct Considering FSI Effect In High Seismicity Region

The aqueduct is a key overhead structure for trans-basin water transfer and water conveyance projects,and it plays an important role in water conservancy projects.With the implementation of the water diversion project in central Yunnan in southwest of China,a number of large aqueducts will be built in high-intensity regions.Therefore,it is particularly important to improve the seismic performance of the aqueduct structure and ensure the normal operation of water diversion projects in high-intensity regions.Since the concept of engineering vibration control was put forward,the passive,active and intelligent control of engineering structures under earthquake action has become a powerful measure for modern engineering structures to prevent earthquake disasters.However,in the seismic practice of large-scale aqueduct engineering,there are few reports on the research results of using the concept of structural control to improve the seismic performance of aqueduct structures,and there are not many studies on related seismic isolation theories.At the same time,how to accurately consider the dynamic relationship between the water body in the aqueduct and the wall of the aqueduct under the action of an earthquake is also one of the research hotspots.Therefore,the dynamic interaction between the water body in the aqueduct and the aqueduct structure system,and based on the basic principles of engineering structure isolation,carried out research on the mechanism and technical measures of large-scale aqueduct structures in high-intensity regions have been considered.The main contents are:(1)The various models of fluid-solid interaction(FSI: Fluid Solid Interaction)of the aqueduct structure are sorten out,the advantages and disadvantages of each theoretical model are given,and an appropriate theoretical model based on actual engineering is selected.Deal with the dynamic interaction between the water body and the structure of the aqueduct;at the same time,it briefly describes the seismic reduction and isolation control mechanism of the engineering structure,and theoretically explains the feasibility of adopting seismic reduction and isolation measures for the large-scale aqueduct structure.On this basis,the dynamic analysis of the aqueduct structure is carried out.(2)The seismic response analysis of the aqueduct structure must first solve the problem of seismic waves.This article briefly reviews the importance of seismic waves in the seismic response analysis of engineering structures,the classification of seismic waves,and the synthesis method of seismic waves.Two sets of natural materials that meet the site conditions of the project are selected.Seismic waves(El-Centro wave,Kobe wave),and at the same time,synthesize an artificial seismic wave(Artificial wave)that meets the site conditions,and a total of three sets of seismic waves are used as the calculation conditions for this study.(3)Taking into account the difference in water depth in the aqueduct,the dynamic characteristics of the aqueduct structure with two different support methods,ordinary basin rubber bearings and high-damping shock-absorbing and isolating bearings are used to analyze the dynamic characteristics of the aqueduct.The calculation results show that with the continuous increase of water in the aqueduct,the natural frequency of the aqueduct structure gradually decreases;in addition,compared to the case of using ordinary basin-type rubber bearings,the natural frequency of the aqueduct structure after adopting shock-absorbing and isolating bearings The drastically reduced drop can effectively reduce the seismic response of the aqueduct structure.(4)In this paper,the dynamic response analysis of large-scale aqueduct structure system is carried out,taking into account two support modes,namely,common basin rubber bearing and high damping seismic isolation bearing,four water depths in the aqueduct,three seismic wave inputs and different peak accelerations(PGA),and the dynamic characteristics of aqueduct structure.The analysis shows that: compared with the use of ordinary basin rubber bearings,the response value of the aqueduct structure is greatly reduced after the high-damping shock-absorbing and isolating bearings are adopted,so that the aqueduct structure has more safety reserves and can ensure its safe operation;With the continuous increase of internal water level,the seismic response of the aqueduct structure continues to increase.When the aqueduct runs at full water level,the response value is the largest;when the seismic waves of different peak ground acceleration(PGA)are input,the seismic response of the aqueduct structure increases with the peak acceleration(PGA)increases.When the ordinary basin rubber bearings are used,the aqueduct structure will be destroyed when the PGA of the seismic wave is 0.3g.The seismic response of the aqueduct structure after the use of high-damping seismic isolation bearings,it is greatly reduced and controlled within the safe range.At the same time,the deformation of the high-damping shock-absorbing and isolating support is greatly increased,and the maximum value reaches 11 cm.At this time,the collision between the aqueduct and the trough pier block should be considered,and flexible materials can be arranged.