Seismic isolation of cylindrical liquid storage tanks

Seismic excited liquid filled tanks are subjected to extreme loading due to hydrodynamic pressures, which can lead to nonlinear stability failure of the thin-walled cylindrical tanks, as it is known from past earthquakes. The overall seismic behavior of tanks is, however, quite complex, since the dynamic interaction effects between tank shell and liquid must be considered. A significant reduction of the seismically induced loads can be obtained by the application of base isolation systems, which have to be designed carefully with respect to the modified hydrodynamic behavior of the tank in interaction with the liquid. Firstly, this paper presents the state of the art of tank design for anchored tanks with a fix connection to a rigid foundation with special focus on the practicability of the available design rules. Then a highly sophisticated fluid-structure interaction model is introduced, which has to be applied for a realistic simulation of the overall dynamic behavior of an isolated tank.