Aqueduct Structure Considering Fluid-structure Interaction, Seismic Response Analysis

The South-to-North Water Transfer Project is built to relieve the serious water shortage in northern region of our country.The main function of the project is to change natural distribution of water resource,and it is an important basal establishment for optimizing water resource.As a building for transporting water spanning rivers . roads or valleys,there are over 10 aqueducts in the middle route of the south-to-north water transfer project,most of which are located in the region where the earthquake intensity is VII degree or over W degree. So it's significative to study seismic response of large-scale aqueduct.At present, the response spectrum method and the time-history analysis method are widely used to analyze seismic response of large-scale aqueduct. The response spectrum method is adopted universally to estimate seismic action in civil engineering.and is fit for small-scale aqueduct when the variability of ground motion input is tiny.As spacial model of large-scale aqueduct is coupled, there will be considerable errors when using the response spectrum method to estimate seismic action,and the method can not reflect time-history effect.The time-history analysis method can describe an aqueduct's seismic response.With the increase of powerful earthquake record and the development of the computer technique,the time-history analysis method is applied more widely .In the past,because of the limit of computer capacity,simple dynamic analysis models are usually used to calculate aqueduct's seismic response.For example, the body of aqueduct is abstracted as a centralized mass,thereby only the brace of aqueduct need to be investigated,or some scholars use thin-walled beam elements to analyze aqueduct by ignoring fluid-structure interaction.In order to assure aqueduct aseismic security,a practical mechanical model should apply to calculate aqueduct's seismic response.This paper is a part of Henan Innovation Project For University Prominent Research Talents(2003KYCX011).Based on the existing production, considering aqueduct running with water and the body of aqueduct which is open section thin-walled member,author have discussed a dynamic analysis model of large-scale aqueduct. In virtue of a simple calculating method,the strength of the water acted on the body of aqueduct is computed .As the body of aqueduct is open section thin-walled member, transverse displacement - lengthways displacement >bending-twisting vibration > restraint twisting deformation and lengthways curl are considered in discussing aqueduct dynamic model. Finite element method are applied to disperse aqueduct.The body of aqueduct adopts thin-walled beam element,each node has 8 DOFs and each element has 16 DOFs.The brace of aqueduct is dispersed with beam elements. The Minimum Potential Energy Principles is applied to infer stiffness matrix of aqueduct body.The Principle of Total Potential Energy with stationary Value in Elastic System Dynamics is used to infer mass matrix.Damping matrix of aqueduct body is assembled by using the existing production. So a dynamic model for calculating aqueduct seismic response is established. Compared with existing models,this model not only includes fluid-structure interaction but also do with lengthways curl of the aqueduct body,so it is a practical model.Dynamic characteristics of aqueduct include the natural frequencies and modes of vibration. According to the aqueduct dynamic analysis model in this paper, dynamic characteristics of a certain large-scale aqueduct is analyzed under five cases. The results indicates: the effect of fluid-structure interaction influences on the natural frequencies, so fluid-structure interaction must be considered in the process of analyzing the dynamic characteristics of aqueduct structure. Natural frequencies decrease orderly with the rising of the aqueduct water level. Mode of vibration is affected noticeably by fluid-structure interaction.Each vertical mode has to be independent and transverse mode couples with twisting mode. Transverse modes of vibration of the aqueduc...