Effect of material characteristics on the critical stress of elephant foot buckling on large-scale oil tanks

Elephant foot buckling is a typical damage form on large-scale oil storage tanks under the effect of earthquake loading. The anti-earthquake design formulas of oil storage tank stipulated in domestic and foreign specifications are all based on thin-walled elastic stability theory, but elephant foot buckling is in the category of elastic-plastic buckling. Therefore, it is necessary to study the effect of material characteristics on the critical stress of elephant foot buckling on large-scale oil tanks. In this paper, the formula for calculating the critical stress of elephant foot buckling on large-scale oil storage tanks was established on the basis of Ramberg-Osgood material model. Then, the effects of material parameters on the buckling critical stress of tank shell were analyzed, including yield-tensile ratio, yield strength and circumferential stress of tank shell. It is shown that the relationships between the power hardening exponent of material and the buckling critical stress of tank shell are affected by circumferential stress of tank shell at the occurrence of elephant foot buckling on the large-scale oil storage tank. The increase of circumferential stress can effectively reduce the buckling critical stress of the tank. The buckling critical stress decreases with the increase of yield-tensile ratio. When the ratio of circumferential stress to yield strength is constant, the buckling critical compressive stress of tank shell can be increased appropriately by increasing the yield strength of material, but the effect is not remarkable.