Finite Element Numerical Computations Of Static Analysis And Seismic Response Analysis Of Cylindrical Liquid Storage Tanks

Along with rapid development of the petroleum chemistry industry, liquid storage tanks (including oil tanks) are extensively applied to various engineering projects, both the scale and number are considerably increasing. During last decade more and more thin-wall large metal liquid storage with storage volume of 100000 m3 have been constructed in our country. Our country is a nation with high activity and high-frequency of earthquakes. Moreover almost all of oil fields located in the seismic zone and neighborhood. Hence in order to guarantee the safety of such lifeline facilities and reduce the seismic-induce direct or secondary earthquake disasters, the earthquake behavior of liquid storage tanks must be investigated by performing seismic response analyses. In usual, the seismic response analyses of liquid storage tanks are based on some simplified analytical model which simplify the complex three-dimensional liquid-storage structures into one-dimensional model on the basis of some assumptions. Although some numerical analyses has been made in the past, because of the lack of a universal and general-purpose finite element analysis software and limitation of computational scale of accuracy, numerical analysis procedure have not been widely applied in engineering practice. In this thesis, an effort for applying the large-scale universal FE software in static analysis and seismic response analysis of liquid storage tanks.A simplified analysis of seismic response of liquid storage tanks is made at first. And then the large-scale universal finite element software for structural analyses "ANSYS" is employed to conduct both static and dynamic analyses of liquid storage tanks. Various computations has been made for the arch storage tanks on rigid or elastic foundations and floating-roof storage tanks on rigid base under different conditions including no storage and fluid storage. Through comparative studies, some conclusions have been gained which will be helpful for rational earthquake-resistant design of liquid storage tanks under earthquake, "elephant the foot transform" and "rhombus transform" can be reproduced by numerical analysis. Uplift region is moon type. Based on analyses of the natural vibration characteristics, it is shown that vibration mode of arch tanks is characterized by multi-waves, can be divided into two types including no-twist and twist. Arch tanks with fluid will have longer natural vibration period and compared with the condition of no-fluid. Accordingly the vibration modes will be different. Natural vibration characteristics in the condition of considering contact of tank base and footing will be different from those without considering contact behavior.