STUDIES OF DYNAMIC AND STATIC RESPONSE OF CYLINDRICAL LIQUID-STORAGE TANKS
Doctor of Philosophy
This study deals with the following two aspects of the response of liquid-filled cylindrical elastic tanks: (a)Dynamic response to a vertical excitation of the base; (b)Statical analysis under antisymmetrical forces of the type obtained in analyses of the dynamic response of the tank to a lateral excitation. The dynamic response of a liquid-tank system is treated in a stepwise fashion by, first examining the free vibrational characteristics of the system and, then, investigating the harmonic and the transient behaviors through a modal superposition procedure. The free vibrational behavior is first investigated on the assumptions that the surface effects associated with the liquid sloshing, and the effect of liquid compressibility, can be neglected. Subsequently, the effects of these quantities are investigated and it is shown that they do not affect the response in any significant way. In the evaluation of the transient response, the effects of the surface sloshing of the liquid and of the liquid compressibility are ignored. The approach to the above analyses consists of satisfying concurrently the equations of motions of the tank and of the contained liquid, subject to the appropriate interface and boundary conditions. Based on the results of the free vibration analysis, approximate models are developed to predict, with acceptable accuracy, some of the modal characteristics of the liquid tank systems. Comprehensive numerical data are presented for analyzing and understanding the behavior of partially and fully filled tanks. The behavior of a partially filled tank is shown to be analogous to that of an equivalent liquid-tank system which is fully filled but has a reduced height corresponding to the depth of the liquid in the partially filled tank. The tank flexibility is found to be of significant importance. In an illustration considered, wherein a fully filled tank of practical dimensions is excited by a broad band vertical excitation, the flexibility of the tank is found to be responsible for effects over three times larger than those induced in a similarly excited rigid tank. Two physically attractive approaches, a displacement approach and a force approach, have been developed for statically analyzing a circular cylindrical tank subjected to the antisymmetrical loadings of the type mentioned in the opening paragraph. Influence coefficients have been furnished to facilitate implementation of the above analyses procedures, which involve application of end displacements or of end forces to correct the deformation/force state associated with membrane state.