Elephant Foot Buckling Research Of Large Cylindrical Oil Storage Tanks

The large oil storage tanks are the key equipments of Strategic Oil Storage Base in China. The typical damage of the oil tanks under earthquake load is elephant buckling, which always appears at the bottom of the oil tank wall. The elephant foot buckling indicates inelastic behavior of the bottom of the tank wall. As a result, the actual axial compression stress in the tank wall should be less than the allowable value in the most oil storage tanks design standard. Therefore, it is very significant to make further research of the buckling phenomenon of the tank wall.The cylindrical shell buckling theory and numerical simulation method are adopted in the research to study the elephant foot buckling of the oil tank wall. The main works in the study are concluded as follows:1. The energy principle is adopted to study the buckling of cylindrical shell subject to axial compression and internal pressure. The incremental theory of plastic stress-strain relationships is considered. Finally, the buckling stress is obtained.2. The numerical simulation is carried on series of oil storage tanks with different physical dimension. The main influencing factors of buckling stress are analyzed, such as circumferential tension stress in the tank wall, structural parameters of the bottom annular plate, the tank wall height, radius and thickness.3. The constant strength design of the oil tank wall leads to varying thickness of the wall. This structure could be considered as a kind of geometry imperfection of tank wall, which affects the buckling stress of tank wall. The numerical simulation is adopted to obtain the buckling stress and deformation shape. Finally, The buckling stress of a large oil tank of 15×10~4 m~3 is obtained and used to compare with the oil storage tanks design standards of China, Japan and America.