A Method for Seismic Protection of Liquid Storage Tanks by Disconnecting the Tank Wall from the Base and Using Energy Absorbing Circumferential Connection

Ground-supported cylindrical tanks are used to store a variety of liquids, e.g., water for drinking and fire-fighting, crude oil and liquefied natural gas. Tanks are critical components of modern industrial facilities and life-line systems, and must be designed to withstand safely the earthquakes to which they are subjected. The failure of such systems may lead to environmental hazard, loss of valuable contents, and disruption of fire-lighting elements following destructive earthquakes. Water storage tanks in particular, are important to the continued operation of water distribution systems in the event of earthquakes. Recent earthquakes have shown liquid storage tanks to be vulnerable to damage. Elasto-plastic shell buckling which is called “Elephant’s Foot” Buckling (EFB) has been the critical aspect in the earthquake resistant design or retrofit of steel, cylindrical tanks. In this paper, an innovative method based on using seismic energy absorbing connection at the base of tank wall is introduced to protect the liquid storage tank against seismic loads. In this method, the tank wall is fully disconnected from the base plate and the special connection is provided at the bottom of the tank. The connection is supported by a ring of rigid foundation and the base plate is supported directly on the ground. The seismic performance of the method is numerically examined for one broad and one slender steel tank. It is shown that this method can prevent the EFB of the tank wall by using the plastic deformation of the connection. Numerical results confirm the efficient performance of the proposed system to reducing seismic vulnerability of shell tanks.