HYDRODYNAMIC PRESSURE ON STRUCTURES SURROUNDED BY WATER

Abstract

In this thesis, a theoretical investigation has been made to evaluate the hydrodynamic pressure on a uniform circu-lar cylindrical cantilever structure surrounded by water and subjected to a simple harmonic ground motion. The effect of the flexibility of the structure as well as the. compressibility of water on the hydrodynamic pressure is studied. Expressions are also derived to evaluate the Virtual Mass Co-efficients and the response of the structure in water. The magnitude and distribution of hydrodynamic pressure along the height of the structure by treating the structure as rigid is compared with that given in IS: 1893(14). A comparative study is also made - to study the hydrodynamic force obtained by considering the structure as rigid, flexible and by the method suggested in IS: 1893(14). An experimental investigation is also carried out to study the dynamic characterisitcs of models of different shapes in water. By keeping the fundamental natural frequency of the models same, the effect of the shape and the slender-ness ratio on the virtual mass values is studied. Also the effect of the period on the virtual mass values for the models of the same cross-sectional dimensions is studied. A compara-tive study of the virtual mass values for the models in the first and second mode of vibration is made. Also the effect o of the submergence of structures in water on the value of dam: is studied. It is observed that the compressibility of water causes an increase in the hydrodynamic pressure in a certain range of the exciting frecfuencies.. Mso the flexibility of the structure causes a considerable increase in the hydrodyna-mic pressure. For structures with the same cross-sectional dimensions, an increase in the fundamental frequency causes a decrease in the virtual mass values. Slenderness ratio of the structure has an important influence on the value of the virtual mass. With an increase in the slenderness ratio, the virtual mass also increases. *