Erdbebenbemessung von Tanks - Erfahrungen aus der Praxis

Seismic design of tanks - Practical experience.

When designing skeletal structures for plants in seismic hazard areas you consider the masses of the structure and the equipment, the stiffnesses of the bracing systems and thus model your structure into a spring-mass-oscillator. Depending on the desired degree of accuracy the actual masses are condensed in many or only a few mass lumps, the bracing systems are considered to have linear restoring forces or non-linear features are included. The response of this dynamic model is then calculated transiently by applying several different artificial ground acceleration time histories or steady state by using a given peak ground acceleration spectrum.
With tanks it is much more difficult to extract easy-to-handle calculation models: the liquid may perform a sloshing motion rather than a cantilever oscillation; accelerations can be transferred into the liquid by compression between the tank wall and the liquid only, while the tank wall itself is a thin-walled membrane which may undergo strainless deformation modes in the shape of Fourier-harmonics. In the present paper we well have a short look on the basics of seismic design and report on some tanks of different sizes, where we were involved in the seismic design.