Seismic Performance Of Vertical Storage Tank With Initial Imperfection

With the development of Chinese social production,the demand for oil has continued to increase.Considering the cyclical nature of oil exploitation and the risk of the market,in order to prevent the adverse impact of insufficient oil supply,China is also constantly increasing investment and construction of oil reserve bases,so as to provide guarantee for Chinese oil reserves.As a liquid storage device,once the tank structure is damaged under the action of earthquake,the consequences are very serious.The typical vertical oil storage tank is mostly a thin-walled cylindrical shell structure with a large diameter to thickness ratio,so it is inevitable that there will be initial imperfection with different shapes,such as axial unstraightness,circumferential non-roundness,and initial imperfection in the process of processing,assembly and construction,which can affect the working performance of the tank structure under static and dynamic forces.But existing norms do not take this effect into account,so studying the mechanical properties of the tank structure with initial imperfection is of great significance to ensure the safety and stability of the tank during use.Based on a 150,000 vertical steel oil storage tank as the research object,this paper uses numerical analysis method to reasonably simplify the tank model,applies the most unfavorable initial imperfection to it through the improved consistent defect mode method,and performs numerical simulation analysis of static force and seismic time history.The main research contents are as follows:First,this paper summarizes the results of the research work of storage tanks by scholars at home and abroad,and summarizes the progress and achievements of tank research in model simplification,initial imperfection research,and seismic performance research.At the same time,this paper also points out the scientific research directions that still need to be worked on,and summarizes the fluid-structure interaction theory,elastic cylindrical shell theory and structural dynamics analysis methods.After that,A reasonable and simplified finite element analysis model of the storage tank is established by using the finite element analysis software ANSYS,and the modal analysis of the storage tank is carried out.The fluid-structure coupling frequency and liquid surface slosh frequency obtained by the modal analysis are compared with the relevant standard formulas to verify the correctness of the model..In addition,the improved consistent defect mode method is used to introduce the most unfavorable initial imperfection into the perfect model,and the static characteristics of the tank structure under the perfect model and the defect model are compared to explore the influence of the most unfavorable initial imperfection on the mechanical properties of the structure under axial pressure and hydrostatic pressure.Finally,this paper does an analysis of the perfect structure and the structure with initial imperfection in different seismic waves,whether the liquid is stored,whether the tank bottom is anchored and different seismic intensity.Based on the results of tank wall acceleration and equivalent force under seismic excitation,the influence of the most unfavorable initial imperfection on the seismic response of the tank is also analyzed,and the influence law of the seismic performance of the tank is summarized.