ボンツーン型浮体の波浪中弾性応答解析へのHamilton-Dirichlet原理の適用（第2報：任意平面形状浮体への適用）

摘要

Many analytical methods have been proposed to calculate hydroelastic responses of a very large pontoon type structure in waves. In relation to the elastic response of such pontoon type structure in waves, Isshiki and Nagata proposed the "Modified Hamilton-Dirichlet's Principle 2", which is expressed only using the velocity potential. It is the variational principles related to motions of the elastic floating plate on a water surface.rnIn this study, in order to calculate the wave-induced responses of an elastic floating plate in waves, a new method was proposed which uses the "Modified Hamilton-Dirichlet's Principle 2" 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 proposed method is applicable for the floating plate of arbitrary plan geometry.rnCalculated results of two kinds of rectangular and L-shaped floating plate in an open sea are compared with experimental results. Good agreement is found between computed and experimental results.%ボンツーン型浮体は、超大型浮体式海洋構造物の代表的rnな構造形式の一つとされるが、その構造設計を行う際には、rn波浪中での浮体の弾性挙動の評価が必須となる。このため、rnモード展開法や直接法に基づいた周波数領域での計算法や、rn時間領域での計算法が多数提案されている1）。解析の対象とrnする浮体形状については、矩形平板に特化した手法から複雑rnな形状にも対応できるように構造部に有限要素法を用いるrn手法2）,3）もある。さらに、初期設計の段階においては、浮体rnの弾性応答が小さくなる浮体構造を選定するために、任意のrn平面形状をもつ浮体の波浪中弾性応答を簡便に評価できるrn解析法等も望まれる所である。