HYDRODYNAMIC FORCES ON STRUCTURES DURING EARTHQUAKES

The earthquake induced hydrodynamic forces on the structures of arbitrary geometries in three-dimensional cases have been formulated and analyzed by using the Boundary Integral Equation approach. This analysis consists of using the fundamental solution, instead of the Green's function, to formulate the integral equations. Since the hydrodynamic pressures can be computed directly from surface integrals, the dimensionality of the problem is reduced by one. Compressibility of water is included in the analysis through the choice of fundamental solutions. A transmitting boundary model is also developed to represent the effect of an infinite region. Techniques for approximate calculation of integrals and for automatic generation of the final equations in terms of nodal equations are borrowed from the finite element approach.;Computed results are compared with analytical solutions for a reservoir of rectangular shape with excitations specified in the longitudinal, transverse, and vertical directions respectively. The accuracy and the efficiency of this approach are found very good. The applications of this approach are extended to a circular cylinder case, and to study the effects of the surface slope on a gravity dam. One parameter, the element length/wavelength ratio, is found important in the analysis when the compressibility of water is considered. The errors produced at different frequencies for different element mesh sizes are studied for the rectangular reservoir case. And this leads to a conclusion that another benefit of using this approach is to have more relaxation on the element length/wavelength ratio.