DYNAMIC STABILITY OF NONLINEAR SHELLS OF REVOLUTION UNDER CONSIDERATION OF THE FLUID SOIL-STRUCTURE INTERACTION

The dynamic behaviour of liquid-filled shells of revolution is investi gated considering the soil-structure interaction and the fluid-structu re interaction, respectively. In the circumferential direction the loa ds and variables are approximated by Fourier series. The shell is mode lled through shell ring elements including non-linear behaviour, coupl ed with isoparametric continuum ring elements and special infinite ele ments for the soil and isoparametric pressure ring elements for the fl uid. Transient loadings like earthquake excitation and the non-lineari ties of the shell and the soil require an analysis in the time domain. To reduce the size of the problem, linear parts of the system are con densed by the substructure technique. The soil region is divided into two parts, a near field permitting non-linearities like plastification or uplifting of the shell, and a far field for the treatment of radia tion of energy. The boundary conditions for the shell footing have a s trong influence on the distribution of the axial membrane forces and, hence, on the stability limit, which is mostly governed by plastic col lapse and caused by the dynamically activated pressure acting on the t ank wall. It is shown how the soil properties influence the dynamic st ability of the shell under harmonic excitation and under realistic ear thquake motion.