Analysis Of The Earthquake Damage Mechanism Of High Intake Tower

In recent years,with the vigorous development of water conservancy and hydropower engineering,high intake tower structure has also been rapid development,but the tower structure after a strong earthquake has tested especially in less in the established high intake tower,and according to the measured data and the test data of high intake tower under the strong earthquake are extremely rare,especially the reference literature which is related to the seismic damage of the high tower hardly query.Therefore,in this paper,for the first time analyze the seismic damage characteristics of high intake tower,respectively considering the mesh size,the input of seismic wave,the foundation radiation damping,concrete damage model,nonlinear material intake tower etc..And in the process of analysis,for the first time to consider the material nonlinearity of foundation rock mass,the intake tower foundation system of earthquake damage characteristics description is more close to the actual earthquake,so as to guide the water tower project has a certain reference value and scientific value.The main research contents and results include:1.On the basis of damage mechanics,theory of continuum mechanics,thermodynamics,and plastoelasticity,a basic idea of establishing the plastic damage model of concrete is put forward in this paper and the principles of choosing damage variable is proposed at the same time.According to the basic idea and the principles,the concerned expression of plastic free energy is derived.Based on the Weibull distribution hypothesis and the tensile and tensile properties of the material were also considered,so there is no need to determine the damage criterion and damage mechanism of concrete material subjected to uniaxial tensile and compressive stress,the relationship between the energy release rate and damage was determined.Then the evolution functions of concrete damage mechanism are established,which make it possible to put forward the functions of damage constitutive,damage evolution and plastic deformation.Through the comparative study of concrete loading test,the validity of the damage model proposed above is preliminarily verified,that is,the damage model can beused to express the seismic characteristics of concrete damage.2.In this paper,based on the secondary development function of the finite element ABAQUS,the finite element program of damage constitutive model is compiled by FORTRAN,and the seismic damage characteristics of Koyna gravity dam are studied.,and with a comparison of the research achievements of literature [109],the results shows that the damage model can better express the earthquake damage evolution characteristics of Koyna dam,and effectively simulate the cumulative seismic damage of Koyna dam,and record the damage cumulative process,therefore,the damage characteristics of Koyna dam under the action of the earthquake is truly demonstrated.3.This paper analyzes the intake tower material nonlinearity influence on earthquake damage,the results show that due to considering the nonlinear of the intake tower,when the intake tower concrete tensile stress peak value is greater than the standard tensile stress of concrete,concrete of the intake tower can cause damage.The damaged concrete is not subjected to tensile stresses,but can still withstand compressive stresses,so that the concrete tensile stress of the intake tower reaches a certain value,and then it will rapidly decrease to zero.This shows that the nonlinearity of the intake tower is more in line with the actual situation;it can be a true reflection of the distribution of stress after the damage of the water tower.4.The study of seismic damage of intake tower by model grid size shows that,in the stress concentration region,the maximum principal stress value of the large-grid model is larger than the maximum principal stress value of the corresponding position of the small-grid model.When the mesh size of the intake tower model is large,the damage expansion process of the model cell will be slow,and the relative strain of the damaged region will be small,which is consistent with the size effect theory of the element,that is,when the mesh size of the intake tower model is large,the accuracy of damage calculation of the intake tower model is reduced,therefore,when the mesh size of the intake tower model is small,the expansion process of seismic damage of the intake tower will be described more accurately and more accurately.Finally,the overall stability of the intake tower is analyzed.The intake tower will not slide or overturn during the whole earthquake;the overall stability of the intake tower meets the requirements.5.Comparing with the inlet tower without considering the steel reinforcement,when the reinforcement is considered,the relative displacement of the top of the intake tower is reduced,the strain on the back of the tower is also reduced,and the damage degree and the areaof the intake tower are reduced.Therefore,the stability of the intake tower is greatly increased by considering the reinforcement of the intake tower.6.On the basis of the small mesh model of the intake tower,the seismic damage analysis of the water tower foundation system is carried out.When the tower body and rock mass system is considered to be nonlinear,the damage area of the tower is reduced.The main reason is the junction of the tower foundation and the stress concentration at the release,at the junction of the tower body and the base of the large range of seismic damage is no longer there,which is more close to the actual situation.Finally,the stability of the intake tower-foundation system is analyzed.The intake tower has no tendency to slip and overturn during the whole seismic process.The safety factor of anti-sliding and the safety factor of anti-overturning are increased.This indicates that considering the non-linearity of the material of the foundation will make the intake tower safer when seismic damage analysis of the intake tower is carried out.7.In this paper,the effects of different boundary conditions on the seismic damage of the water tower are analyzed.With the gradual rise of the tower back ground,the tower body damage dissipation can reduce gradually,the less damage the tower body produces;the more stable the tower structure.And the higher the dorsal foundation,the later the damage time of the tower body,the smaller the peak acceleration of the intake tower.Therefore,the lower the height of the foundation is,the lower the stability of the intake tower is.It can be known that the tower back foundation has a significant impact on the tower body earthquake damage,and should be carefully considered in the design and construction of the intake tower.