Seismic response of slender storage tanks on tube feet or skirt support

Slender storage tanks on tube feet or skirt support are essential components of industrial facilities and often contain large amounts of hazardous liquid. As the geometry of such storage tanks with torispherical heads is somewhat standardised, seismically induced stresses and anchoring forces are often calculated by the equipment manufacturer in a simplified and conservative way. Thereby, the hydrodynamic effects of the stored liquid are usually not taken into account. This often leads to high resulting anchoring forces that may exceed the typical bearing resistance of the discrete anchoring at the tube feet or skirt support. In this paper, a procedure is suggested that lowers the overall stress resultants by determining the tank’s response in a more differentiated way. It is based on calculating the hydrodynamic pressure and load components as a function of the geometrical characteristics of the tank. The general concept was developed for flat bottom tanks but can be transferred—with certain adjustments—to the considered slender storage tanks on tube feet or skirts. Emphasis is set on the potential for energy dissipation and on the choice of appropriate response acceleration and response spectra, respectively, which is different for the individual load components. The suggested procedure is prepared for easy-to-use application by providing simple formulas and tabulated coefficients. Its capability for design load reduction in comparison to the simplified calculation method is shown on an exemplary case study.