Study On The Isolation Of Large Vertical Storage Tank

The current world is the world of energy. With the development of the industry,the demand for oil is growing. Many times of oil crisis have occurred in nearly half a century,through which it is getting to be known that the rising oil prices and the reserve of oil are closely related to the national development and security. In order to realize the great ideas of Chinese Dream and actively respond to the impact of short-term oil supply, our country is speeding up the strategic petroleum reserve in order to meet the growing needs of energy reserves and delivery and ensure the constant supply of crude oil. For this purpose, the construction quantities of vertical cylindrical storage tanks are increasing, and becoming bigger sizes and more float-typed. Large vertical storage tank has become a strategic important structure. Vertical storage tank which is strategic oil reserve bases and petrochemical enterprises’ important industrial facilities is used to reserve flammable, explosive and other dangerous medium commonly. So how to guarantee the safe and reliable operation of tank in the earthquake disaster, and reduce the economic loss and the secondary disasters caused by the earthquake is the important research subject of civil engineering. Aiming at large vertical floating tank, stretching the thought of structure base isolation, and considering the influence of the floating roof to the liquid sloshing, the paper researches the earthquake response of large vertical storage tanks with the base isolation, and conducts the isolation design of large vertical storage tanks, by using the numerical analysis method. The main research contents are as follows:(1) Firstly, the paper analyzes research background of the topic and the important significance of topic selection, simply introduces the type and structure of storage tank and the commonly used foundation forms and selection principles of vertical storage tank. At the same time, it briefly summarizes the tank structure seismic and theoretical research of isolation field,the numerical simulation analysis and the main content, and progress of experimental study. And it mainly discusses the isolation tank numerical simulation analysis and research progress at home and abroad,and puts forward to the main contents of this study.(2) By using the knowledge of fluid mechanics and based on the theory of velocity potential, the reservoir is simplified to three particle simplified systems of rigidity pulse particle, liquid-solid coupling particle and sloshing particle. And considering floating roof vibration to the influence of reservoir sloshing, and taking the large vertical storage tank with base isolation as the research object, the simplified model which only considers three particle translations is established, and no swinging with base isolation motion equations is presented. At the same time, it puts forward to simplified model of vertical tank with base isolation which considers the effects of foundation swing on the basis, and deduces to provide motion equation of vertical tank with base isolation which considers the effects of foundation swing. And it also puts forward to storage tank with the isolation system which sets up isolation between pile foundation and pile cap, and considers the interaction between the pile and the soil. The lateral stiffness of pile foundation is derived, considering the motion equation of pile-soil interaction is established.(3) The paper researches the basic characteristics of large vertical floating roof tank with base isolation, and gives the characteristic period and vibration mode of tank.(4) Aiming at common ten kinds of storage tanks in engineering, and based on the specification method, the characteristic period of the storage tank, base shear, base bending moment and shaking wave height are calculated. According to the motion equation of storage tank and no considering the two kinds of working condition of swinging or not swinging, mode-superposition response spectrum method is used to calculate the seismic response of vertical storage tanks with the base isolation. The Matlab is used to write program, and the Wilson-θ method is used to conduct time history analysis. When conducting time history analysis, respectively input the golden gate seismic wave(type I site), foreign apartment seismic waves(type II site), El centro seismic waves(type III site) and Pasadena seismic waves(type IV site).Then the earthquake response of the tank is obtained under the action of the four different types seismic wave(or site). Finally, the effect of the cycle of base isolation and damping parameters to base isolation is discussed.(5) Summarize the characteristics of near-fault seismic, research under the action of near-fault ground motions, the dynamic response of vertical storage tank with base isolation. The results showed that: base isolation can effectively improve the seismic intensity of tanks, put off the occurrence of tank wall buckling failure, which play an effective controlling seismic response purposes.(6) The ground motion table test of vertical tank scale model is conducted in the paper. The results show that the rolling isolation system can effectively reduce the seismic response, and it is consistent with the theoretical analysis of isolation system and numerical analysis results, which also further validate that using base isolation device can reduce the intensity to design.