SHELL-PLATE INTERACTION IN THE FREE-VIBRATIONS OF CIRCULAR CYLINDRICAL TANKS PARTIALLY FILLED WITH A LIQUID - THE ARTIFICIAL SPRING METHOD

The free vibrations of a circular cylindrical tank partially filled wi th an inviscid and incompressible liquid with a free surface orthogona l to the tank axis are analytically studied. The tank is modelled by a simply supported circular cylindrical shell connected to a simply sup ported circular plate by an artificial rotational distributed spring o f appropriate stiffness. The plate is considered to be resting on a Wi nkler elastic foundation. The effects of the free surface waves and th e hydrostatic liquid pressure are neglected. The bulging modes (where the tank walls oscillate with the liquid) of the structure are investi gated and the solution is obtained as an eigenvalue problem by using t he Rayleigh-Ritz expansion of the mode shapes and then minimizing the Rayleigh quotient for coupled vibrations. The effects of the liquid le vel inside the tank, of the stiffness of the Winkler foundation and of the spring stiffness at the shell-plate joint are investigated for sh allow and tall water-filled tanks. Comparison with available results i s also given. (C) 1997 Academic Press Limited.