Study On Hydrodynamic Pressure And Dynamic Response Of Intake Tower Structure Under Earthquake

Intake tower is an important part of water conservancy and hydropower project.With the growing scale of the hydropower project in recent years and as the engineering throat,the intake tower has more prominent impact on the seismic safety of the water control project.The influence of hydrodynamic pressure on the structural response of intake tower during earthquake is significant and the mechanism is complex,which needs to be studied systematically and deeply.In the dynamic response analysis of intake tower,reasonable ground motion input,foundation boundary treatment and material constitutive are the prerequisite to get the correct result,most studies only consider one of them,its hardly get the real earthquake response.To carry out a number of hitherto huge engineering projects,the intake tower-water coupling research and real 3D numerical model exploration is necessary.These researches can summarize the law and accumulate experience,provide the reference and basis for seismic design of intake tower.In this paper,the hydrodynamic pressure distribution and dynamic analysis model of the intake tower are discussed.Through numerical and analytical and semi analytical method summarized the hydrodynamic pressure distribution of intake tower under the effects of different factors.Considering the foundation radiation damping effect,the bank intake tower of artificial boundary were set,and the CDP model of concrete and rock were given in order to consider material nonlinearity.The main work and achievements are as follows:1.The intake tower and its foundation and water are a complete resisting system when suffer strong earthquake.Based on the ALE method,a fluid structure coupling analysis model of intake tower-foundation-water is established.The correctness of the numerical method is verified by an example.On this basis,the distribution law of hydrodynamic pressure of group tower and single tower on rigid foundation under different influence factors is studied,and the applicability of the added mass formula of intake tower in the hydraulic anti-seismic standard is discussed.2.The hydrodynamic pressure distribution of tower type intake and bank-tower intake isdiscussed.With the increase of water depth,the natural frequency of the tower type intake decreases gradually.With the increase of backfill height the frequency of bank-tower intake increases obviously.When the tower intake is excited by harmonic of different frequencies,excitation frequency closer to the first-order frequency of the tower the hydrodynamic pressure increases obviously.Under the action of different seismic waves,the distribution rule of hydrodynamic pressure curve is approximately the same.The hydrodynamic pressure of the bank-tower intake decreases with the increase of the backfill height,and there is a big difference between the hydrodynamic pressures under different ground motion records.3.Based on the potential fluid theory,the expressions of the vibration modes of the intake tower inside and outside are obtained,and the hydrodynamic pressure distribution equation is obtained.After comparing with the numerical method,the applicability of the method in the intake tower structure is verified,and the influence of the elastic modulus and water height on the hydrodynamic pressure distribution is analyzed.The Morison equation which is widely used to calculate the wave forces of deep-water piers of bridge is introduced into the intake structure.The Morison equation is extended so that it can be applied to the intake tower with inner rectangular cross section.The results show that both the internal and external hydrodynamic pressure are converted into additional mass.The hydrodynamic pressure distribution is relate to the cross-section shape of the tower but not the height of water.4.Based on the propagate theory of elastic wave,the equivalent load time history of vertical incident wave on the truncated boundary of foundation was compiled by FORTRAN language.Based on the theory of viscoelastic artificial boundary,the boundary and the solution of dynamic response of intake tower are realized by APDL language.The method suitable for bank intake tower is put forward,and numerical experiments is carried out to verify the correctness.The structural response of intake tower under five different boundary conditions is compared.The results show that the proposed method with contact set can accurately reflect the response of intake tower.5.Based on the theory of wave propagation in elastic medium and infinite element method the expressions of equivalent load time histories on the nodes of artificial boundary are derived under the condition of S wave and P wave.The infinite element and finite element modeling method is given.Generation and accurate application of load amplitude on boundary nodes by using Python script.It is verified by a small example that the proposed infinite element artificial boundary can effectively solve the problem of ground radiation damping.Based on the stress-strain relationship in concrete design specification the CDP model of concrete and damage evolution curves of base rock are obtained.The nonlinear dynamic analysis of a bank-tower intake is carried out.The results show that the damage occurs at the interface ofrock and the geometric mutation of intake tower.Plastic strain occurred between tower and surrounding rock,the tower has permanent deformation after earthquake.