Research And Application Of Seismic And Isolation Of Large Scale Aqueduct

The Central Yunnan Water Diversion Project is a large scale water conservancy project being constructed to alleviate water shortages in Kunming,Yuxi,Chuxiong,Qujing,Dali and other regions.It is also the first of the 10 iconic projects among the 172 major water conservancy projects started by the country before 2020.As a water conveyance structure that crosses rivers,valleys,roads,etc.,the aqueduct occupies an important position in the water diversion project in central Yunnan.Central Yunnan is located in the seismic belt of central and western Yunnan,which is one of the earthquake-prone areas in China.Therefore,it is of great significance to ensure the seismic safety of large-scale aqueduct structures under earthquakes.In order to study the dynamic characteristics and seismic dynamic response of large scale aqueduct structures,this paper takes Dongjia village aqueduct in the central Yunnan water diversion project as the research object,analyzes and calculates it.In the calculation of the dynamic characteristics of the large aqueduct structure,five different water depths in the aqueduct(no water in the aqueduct,1/4 design water depth's water in the aqueduct,1/2 design water depth's water in the aqueduct,3/4 design water depth's water in the aqueduct,design water depth's water in the aqueduct)are considered.Modal analysis of the aqueduct was performed by the Block Lanczos method,and the influence of different water depths on the dynamic characteristics of large scale aqueduct structures was obtained.In the analysis of seismic dynamic response,three lateral seismic waves(artificially simulated seismic waves,EL-Centro seismic waves,and Tangshan seismic waves)and two different bearings(isolated and non-isolated bearings)were considered.The time history responses of the vertical stress and the longitudinal stress of aqueduct structure under three kinds of transverse seismic waves are obtained;and the results of dynamic response of isolated bearing and non-isolated bearing are compared.From the calculation results,the following conclusions can be drawn:(1)Water level has a greater impact on the dynamic characteristics of the aqueduct structure.As the water level in the aqueduct increases,the mass of the water body in the aqueduct gradually increases,which reduces the natural frequency of the structure,but does not affect the main mode shape of the structure;Compared with the same type of aqueduct,the natural frequency of Dongjia village aqueduct is relatively high;The change of the water depth in the aqueduct has a greater impact on the dynamic characteristics of the aqueduct structure.Therefore,when the dynamic analysis of the large aqueduct structure,the change of the water level in the aqueduct cannot be ignored.(2)Seismic waves have a greater impact on the dynamic response of the aqueduct structure.The seismic response of the aqueduct structure is different under the effects of three artificial transverse seismic waves,the EL-Centro seismic wave and the Tangshan wave.Now take the peak stress as an example to analyze: Dongjia village aqueduct structure is more sensitive to Tangshan seismic wave,the vertical stress peak and the longitudinal stress peak of the typical node 31922 at the bottom of the side wall of the mid-span section are the largest,followed by the stress peak under El-Centro seismic wave,and the stress peak of the artificial simulation seismic wave is the smallest.Therefore,it is suggested to select some seismic waves that are consistent with the engineering site category as much as possible in time history analysis.Under the action of transverse seismic waves,the vertical stress of the aqueduct vertical wall(side wall and middle wall)is most obviously affected,which is greater than the longitudinal stress.(3)The seismic isolation support has greatly improved the seismic performance of the aqueduct structure.After the isolation bearing is set,the peak value of vertical stress and the peak value of longitudinal stress of the bottom node 31922 of the side wall in the mid span section are significantly smaller than that of the corresponding node in the non-isolation bearing model(the peak value of vertical stress is reduced by more than 20%).But the shape of the time history curve of the vertical stress and the longitudinal stress of the corresponding joints in the isolation bearing model and the non-isolation bearing model is basically the same.In the isolation bearing model,the lateral displacement of the top node 66700 of the side wall of the mid span section is more than 98% larger than that of the non-isolation bearing model.It can be seen that the seismic dynamic response of the structure has been greatly improved after the isolation support is set,and the seismic response of the structure can be significantly reduced by the isolation support,so that the seismic performance of the structure can be improved.