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.