This paper is concerned with a unified approach which predicts the stochastic responses of a flexible floating island subjected to wind-waves and seaquakes, taking into account the dynamic interaction effects among a floating island, anchor system and sea water. The floating island is modeled as an elastic circular plate and the anchor system is considered to be composed of distributed tension-legs. Based on a 1inear potential flow theory, the hydrodynamic pressure generated on the bottom surface of the island is obtained in closed form. The modal equations of motion of the island with or without anchor system is derived by energy method. In the formulation, the dynamic interaction effects are estimated as hydrodynamic added mass, hydrodynamic added damping and hydrodynamic added stiffness. The response quantities are evaluated as root-mean-squared values using a linear random vibration theory. Numerical examples are presented to discuss the effects of hydrodynamic radiation damping, anchor system, and wind-wave and seaquake characteristics on the stochastic responses of flexible floating islands.
With the recent trend toward the construction of largescaled offshore structures, a number of projects related to the artificial islands which serve as floating cities or floating airports have been proposed. The designs of these large-scaled floating structures demand a better understanding of the dynamic behaviors of structures in an ocean environment. Since the deformation of large-scaled floating structures would play an important roll in the overall responses under environmental forces, it is necessary to introduce the fluid-structure interaction effects induced by the deformation as well as rigid body motion of structures in the dynamic analyses. This study deals with circular floating islands which present the same resistance to incident ocean waves regardless of direction and are, therefore, considered preferable to rectangular floating structures.