A time domain analysis on the hydroelastic deformation of a pontoon-type very large floating structure (VLFS) is investigated considering horizontal motion effect. In our previous study on time domain analysis, the only vertical motion of VLFS has been considered in the analysis of hydroelastic responses, which is appropriate for operational condition. But in the state of survival condition, the horizontal motion coupled with the hydroelastic response would be very important to design the mooring system of VLFS. In the present study, a three-dimensional free surface flow with the fully nonlinear free surface conditions is formulated in the scope of potential flow theory. A finite element method based on the variational principle is employed both for fluid motion and structural response. Elastic response of VLFS is analyzed by Mindlin plate model. The only surge motion is considered as the horizontal motion for numerical simplicity.

INTRODUCTION

Researches and technology developments of VLFS have been carried out for various applications such as floating airport, terminal and military utilities. For the operational safety and reliability, it is of great importance to investigate the dynamic response of VLFS due to harsh environments at the sea. Recently, global warming seems to cause the disastrous weather conditions such as typhoon and hurricane occur frequently in the coastal area. Therefore the survivability of VLFS in the extreme wave condition should be investigated as one of important considerations. Such an extreme condition requires time domain analysis to investigate the dynamic response of VLFS due to strong nonlinearity occurring under such an extreme condition. Reviews on the hydroelasticity of VLFS (Watanabe et al., 2004; Kashiwagi; 1998,1999) mentioned that more studies on hydroelastic response of VLFS under highly nonlinear waves. In those extremely nonlinear wave conditions, it is important to estimate the mooring force to ensure safe mooring system. In the past decade,

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