Seismic Protection System to Prevent Elephant-Foot Buckling in Unanchored Storage Tanks

Steel tanks are widely used in various industrial sectors for storing liquids such as water, wine, and oil. However, their structural performance during seismic events has been a major concern, leading to significant losses in liquid containment, economic losses, and environmental contamination. One of the most critical and common failures in continuously-supported tanks is shell buckling in the shape of an elephant's foot, caused by large radial deformations near the shell-to-base connection. This study evaluates the seismic performance of unanchored continuously-supported liquid storage tanks equipped with an innovative seismic protection system by means of Nonlinear Static Pushover Analysis (NSPA). The proposed protection system is a ring-shaped elastomer incorporated into the tank foundation to mitigate excessive stress concentration and the consequent buckling failure. Nonlinear 3D finite element models were created to analyze a typical geometry for a stainless steel tank, and pseudo-acceleration required to induce buckling failure was estimated for the tank with and without the ring-shaped elastomer. A pushover-based seismic performance assessment was carried out for the tank with and without the elastomeric ring. The results showed that incorporating the elastomeric ring increased the pseudo-acceleration required for buckling failure by 18%, demonstrating an improvement in the seismic capacity of the structure.