Seismic Response Analysis Of Large Inverted Siphon Structure

The diversion project in Central Yunnan is the basic project of the national sustainable development strategy in Yunnan Province.The water diversion project can solve the water resource shortage problems in Central Yunnan,and has obvious benefits for people’s livelihood,social,economic development and ecological environment protection.The construction task of water diversion project in Central Yunnan is to mainly supply water for urban life and industry,taking into account agriculture and ecology.Inverted siphon structure is widely used in the diversion project of central Yunnan Province as an important three-dimensional crossing hydraulic structure.With the implementation of water diversion project in China,inverted siphon project tends to be large and huge,and Yunnan is in the earthquake prone area.Therefore,it is important to ensure the safety of inverted siphon structure under various load factors and earthquake action is related to the safety of people’s livelihood It is also an important research topic for the development of the country.Based on the research background of the diversion Dali section II project in Central Yunnan Province,combined with the site conditions,terrain characteristics and operation conditions,the following Zhuang inverted siphon is the research object,and the finite element model of soil structure water interaction is established.The inverted siphon structure under the action of multiple factors is analyzed as follows:(1)The 7-span model has been established to analyze the inverted siphon structure in the lower part of the middle of the river.Under the static action,the stress is too large on the left and right sides of the middle water passage hole,the side of the two sides of the water passage hole and the bottom plate position.The maximum tensile stress is 1.51 MPa and the maximum pressure stress is 1.35 MPa,therefore,reinforcement shall be properly strengthened for the middle wall,side wall and bottom plate of inverted siphon structure to avoid cracking of pipe concrete.(2)The dynamic model of single span has been established,and the dynamic characteristics of the structure are analyzed considering the water and water.The results of modal analysis show that the natural vibration frequency of inverted siphon structure system will decrease when the pipe is filled with water,but the reduction is not large,with an average of 0.032%-0.501%.According to the structure vibration pattern diagram,the vibration mode of inverted siphon structure is basically the same under water free and water conditions.At the base frequency of 0.18032 hz,the structure system mainly oscillates along the tube body in longitudinal direction.(3)Through the application of viscoelastic artificial boundary conditions to the single span dynamic model and the seismic response analysis of the structure,it can be seen that the maximum tensile stress and maximum compressive stress of the pipe body under the water condition are larger than that under the water condition,and the extreme stress occurs at the structural corner and edge.Under the water condition,the maximum tensile stress on the inner wall of the pipe body is greater than that of the outer part of the pipe,In the case of no water,the opposite is true,which indicates that when there is a large mass water body passing through the pipe,the contact position between the inner wall of the pipe and water is easy to be damaged;the displacement response of inverted siphon structure is shown as follows: with the horizontal shaking of earthquake action,the deformation of the pipe body itself is more than the water square in the vertical direction,which is because the horizontal stiffness of the structure itself is greater than the vertical stiffness,so it is easy to damage the position of the pipe wall and water when there is a large mass water body passing through the pipe;the vertical deformation and failure occurred in the lower part.(4)Through the nonlinear damage analysis of inverted siphon structure under different peak acceleration,it can be seen that with the increase of PGA,the plastic deformation of the structure gradually expands,and the damage area develops rapidly.The tensile failure area of inverted siphon structure is generally larger than that of compression failure area.Under the water condition,the damage factor of the pipe body is obviously larger than that under the water condition,and the main distribution of the damage area is mainly distributed If the earthquake action increases continuously,the damage area of the pipe body will be in the trend of penetration if the earthquake action increases continuously.