Abstract: Elephant foot buckling is a classical failure mode of large oil storage tank under vertical impact load. There are many restrictions and weaknesses in traditional ways to improve elephant foot buckling critical load. So a new method that sets a light ring stiffener in dangerous zone near the tank’s bottom is presented to enhance resistance of the tank wall against elephant foot buckling. According to the elastic shell theory, comprehensive mechanical analyses of deformations of oil tank wall with ring stiffener are carried out. The analytic solutions of circunferential internal forces and deformations of oil tank wall are obtained, and the relation between ring stiffener’s height, cross sectional area and radial displacement of shells is built. Meanwhile, analysis calculation for the shell of large oil storage tank is done. The effect that different cross sectional area and height of a ring stiffener have on both the circunferential internal force and radial displacement of tank wall dangerous zone has been investigated. Results show that reasonable height and cross sectional area of a ring stiffener can effectively decrease both the circunferential internal force and radial displacement of tank wall dangerous zone, and the tank’s resistance capacity against elephant foot buckling has been improved.

Key words: large oil storage tanks;elephant foot buckling;ring stiffener;elastic shell theory