In this study, in order to calculate wave-induced responses of an elastic pontoon type floating plate of arbitrary plan geometry in waves, a new method is proposed which uses "Modified Hamilton-Dirichlet's Principle 2" considering wave radiation condition and the eigenfunction expansion method for fluid motion. The velocity potentials in fluid regions with and without the plate are expanded by eigenfunctions in vertical mode which satisfy the governing equations and free-surface conditions, taking into account the presence of the plate in the same manner as Kim and Ertekin. In this method, "Modified Hamilton-Dirichlet's Principle 2" is finally reduced to a variational equation which corresponds to boundary conditions on the plate's edge. The formulation of the proposed method is applicable for the floating plate of arbitrary plan geometry. Calculated results of two types of rectangular and L-shaped floating plate in open sea are compared with experimental results. Good agreement is found between computed and experimental results.
Pontoon-type VLFS is one of the typical structural types of very large floating structures (VLFS). Various numerical methods have been proposed to predict the hydroelastic response of this structure in waves (Watanabe (2004); Chen (2006)). These methods are classified into the modal expansion method and the direct method. These analyses are carried out in the frequency domain or in the time domain. Most analysis so far dealt with VLFS of rectangular planform. There are also methods using the finite element method for the structure in order to analyze actual complicated floating structure (Seto et al. (1998); Utsunomiya et al. (2002)). In relation to the elastic response of Pontoon-type VLFS in waves, Isshiki and Nagata (2001) derived four kinds of variational principles related to elastic motions of such a floating plate and made clear the mutual relationship of them.
