Super-Large Cooling Tower Seismic Design And Analysis Of Collapse Reaction

Large cooling towers are widely used in industrial fields such as thermal power plants and nuclear power plants.The secondary disasters caused by the collapse of cooling towers in nuclear power plants are incalculable.With the increasing demand for nuclear power energy by mankind,the height of cooling towers is also increasing.The super large cooling tower structure is an important subsidiary structure of nuclear power plants.It collapsed after being destroyed in an earthquake.Due to its tall size,it is likely to directly affect adjacent buildings(structures).This collapse may also cause violent ground vibrations,which will affect the damage of adjacent nuclear facilities.Operation poses a serious threat.Therefore,the use of seismic isolation technology can improve the seismic performance of the cooling tower and avoid its collapse and damage under the action of strong earthquakes.The main research work of this paper is as follows:(1)This paper conducts a preliminary seismic isolation design for a super large cooling tower,and determines the diameter of the support based on the maximum vertical bearing capacity that the seismic isolation support may bear.Then the displacement of the seismic isolation layer of the seismic isolation cooling tower under the action of rare earthquakes is checked,and the results show that the ultimate displacement of the seismic isolation support meets the requirements of the code.Then,the seismic isolation cooling tower was checked for wind load under the larger wind pressure once in 50 years,and the check result met the requirements of the code.(2)Use ANSYS/LS-DYNA finite element software to establish the finite element model of the non-seismic and seismic isolation super large cooling tower structure,and mesh the finite element model of the cooling tower.The solid element isolation support is used for numerical simulation,and the mechanical performance of the isolation support is verified.Then it introduces the unit connection mode,material failure criterion,hourglass control,and load application in detail.(3)Modal analysis of the cooling tower.Both the unisolated cooling tower and the isolation cooling tower have many adjacent modes and appear in a symmetrical form.The modes that contribute a lot to the mass participation coefficient are separately studied.The vibration mode that contributes more to the mass participation coefficient in the horizontal direction is called the overall translational vibration mode,the vibration mode that contributes more to the mass participation coefficient in the Z direction is called the vertical compression mode,and the vibration mode that contributes the greater mass participation coefficient in the rotation direction is called the overall translational mode.It is the overall torsional mode and the lateral bending mode.After vibration isolation,the natural vibration period of the cooling tower is significantly prolonged.For the mode shape with a large mass participation coefficient,the order of the mode shape after isolation is significantly earlier than the order of the mode shape without isolation.(4)Select 3 sets of seismic waves and carry out bidirectional input,respectively,compare and analyze the seismic response of seismic isolation and unisolated cooling tower structure under the action of 8 degree earthquake fortification corresponding to frequent earthquakes,fortification intensity earthquakes and rare earthquakes.Calculations show that the base shear force,tower displacement,tower acceleration,pillar internal force,tower stress and strain of the cooling tower after seismic isolation are significantly reduced,and the greater the PGA,the more obvious the seismic isolation effect.The stress and strain in the middle and lower area of the cooling tower tube and the connection between the tower tube and the pillar are relatively large,which belongs to the weak position of the tower tube.(5)Three sets of seismic waves are used for three-way input,and the seismic response of the isolated and unisolated cooling towers under rare earthquakes or even super-large earthquakes is compared and analyzed.Analyze the collapse morphology of isolated and unisolated cooling towers under different seismic waves.The unisolated cooling tower probably began to collapse under the effect of a rare earthquake.However,the cooling tower after isolation can still not collapse under the effect of an extremely rare earthquake.This shows the safety of the cooling tower after the use of seismic isolation technology.Significantly improved.The shear deformation limit value of the seismic isolation support is different due to the different compressive stresses of the seismic isolation support under the action of different earthquakes,and the ultimate shear displacement of the isolation support under the action of the three seismic waves is also different.Comparing the energy time history curves of isolated and unisolated cooling towers,it can be seen that when the seismic wave acceleration is small,the cooling tower is in the elastic stage,and the kinetic energy and internal energy are small;as the earthquake action increases,the internal energy gradually As it increases,the kinetic energy also increases significantly;finally,the structure enters the collapse stage.