Study On Seismic Response Numerical Analysis And Applicational Method Of Liquid Container Structure

LCS (Liquid container structure) is a kind of very important structure which is closely linked with people's daily life. For different liquid, LCSs, such as water tower, water tank, storage tank, acid tank, digestion pool, cooling tank, and condenser, are widely used in lifeline engineering, energy and chemical industry fields. The structural forms of LCS are varied, including half-underground type, horizontal type, vertical type and supporting type, etc.For liquid-structure interaction, the seismic response of LCS is very complex. Especially under the strong earthquake action, the damage patterns are varied. Previous earthquakes have demonstrated that, in the high intensity zones, a number of LCSs were damaged such as floating support moving, support structure moving, foundation cracking, and wall fracturing, etc. Great economic loss would be caused by the directly damages of LCSs, and the production and life would be forced to be interrupted.In addition, the liquid of LCS sometimes is a kind of dangerous source. When the LCS is damaged during earthquake, the terrible secondary disasters such as fire, explosion and environment pollution could be caused by liquid leakage. On March11,2011, the M9.0East Coast Earthquake occurred in Japan, the LCS of Fukushima Nuclear Power Station was damaged by the earthquake and subsequent tsunami. For this reason, the cooling system was failure to be controlled which caused nuclear leakages.The related research on the seismic response for the LCS could be traced back to1930's, which consists of establishment of theoretical analysis model, liquid-structure coupling effect, simplification method for engineering application, seismic response analysis, method of seismic design and numerical analysis technique, and so on. However, in the view of engineering application, there are many subjects should be discussed deeply such as FE (finite element) analytical method, nonlinear algorithm, seismic response analysis, application method of seismic design for engineering and optimization design, etc.Based on the mentioned above, study on the seismic response analysis and application method for the LCS are mainly carried out in the thesis. The main work and achievements are listed as follows:1. It is concluded that the difficulty of analytical solution of LCS is to solve the Laplace equation with given boundary conditions and initial conditions. And the analytical solution about elastic wall theory and Housner simplified method are both established on base of the theory of impulse pressure and convenes pressure. To numerical solution about LCS, the Haroun-Housner analysis model is based upon the rigid wall theory and FE model upon velocity potential theory. In this thesis, an example is used to make comparison among the four methods, and the result shows that FE numerical model is reliable.2. Based on classical N-R nonlinear iteration principle algorithm, the advanced N-R algorithm is proposed to solve nonlinear numerical calculation about LCS. In this algorithm, both tangent stiffness and normal stiffness are considered that increases the single iteration step length and improved the calculation efficiency. Based on the advanced N-R algorithm, the super N-R algorithm is proposed by establishing the relation between numerical iteration theory and the constitutive relation of material. The super N-R algorithm works more efficient than the advanced N-R method. By a large number trial calculations, the stable proportional coefficient value η of steel is suggested to be around1.46. Plug-in mode and technique of birth-death element are combined to verify the effectiveness of the both improved nonlinear iteration algorithms in the simulation process of LCS by examples. The results provide the proof that the two algorithms improve calculation efficiency of nonlinear numerical seismic response analysis of LCS greatly.3. By using APDL language, the second developing method of establishing FE model is studied which make user subroutines programed and called successfully in ANSYS environment. Based on this method, it is simplified effectively to build FE model, calculate and analyze data for the complex structure form of LCS, which provides convenience for engineers to make seismic analysis about LCS. The main work about second development in this thesis includes several contents as follows:to provide gradient meshing technique for3D complex FE model which could improve the meshing quality; to provide the subroutines about save, read and batch process; to provide the method of stiffness matrix modification based on the technique of wave front. With these methods, the quantity of storage and calculation are decreased, and the efficiency and practicality of FE model are improved.4. Based on the technique of influence line by modal analysis to control meshing quality, ATOS subroutines realizing transformation of FE model from ANSYS to other general finite element software and sub-model approach of the Saint-Venant principle, the effectiveness of FE model during seismic analysis about LCS is improved. Hereby, the FE model of LCS is built and the seismic response is studied such as the influence of factors of basic frequency, earthquake load input, thickness, liquid storage and diameter-height ratio. Besides, the influence on the hydrodynamic pressure, the effective stress, base moment and base shear from elastic deforms of LCS are analyzed. These studies provide the basis for seismic analysis and design of LCS.5. Based on the analysis about seismic response of vertical LCS and interpolation theory, earthquake damage such as elephant-foot buckling is studied. According to the elephant-foot buckling damage, a new function form is proposed to help obtain the location of elephant-foot damage quickly by programming subroutines of spline interpolation and numerical fitting. Based on a lot of calculations, the value table of coefficients in the function is suggested. With this method, it shows that the fast determination of elephant-foot location has been realized, which could provide the base for more efficient seismic design to apply.6. Based on the shape topology theory, ESO (Evolutionary Strucure Optimization), the method of topological design about the outline of LCS during seismic design is studied. ESO methods such as based Misses stress, stiffness constraint and frequency control are introduced. The method, introducing non-continuous classification of elements into ESO topology theory, is developed. This method could solve the problem increasing the delete rate, BDRi which causes the irreversibility of stiffness matrix or elements discontinuity during the process of topology calculation. And in this method the stability of topology analysis on outline of LCS is improved.7. Based on the intelligent algorithms, parameter optimization design method of LCS is studied. The intelligent algorithms such as exhaustive algorithm, ACO algorithm, PSO algorithm and DE algorithm are introduced. The method of combination ACO algorithm with substructure technique is provided to decrease the computational cost about the parameter optimization calculation of LCS. And the PSO-DE algorithm is proposed to optimization calculation. Considered flight, mutation and cross in this method, the global searching scope could be expanded to avoid the optimization trapps in local optimum and the speed of convergence increased, and the optimization efficiency could be improved much.In this thesis, effective numerical analysis method and implementation technology are provided to study on seismic response of LCS. Based on it, by using the analysis results, great convenience is brought to the engineering application Besides, some efficient application methods is proposed to seismic design of LCS, the important theories and application base are provide for the work of disaster prevention and mitigation engineering of LCS.