In order to predict the behavior of floating body under tsunami flood appropriately, it is significant to evaluate the drag force exerted on the float shape when reproducing the dynamics with drift. So, we prepared the drift simulation model based on the Distinct Element Method (DEM). In the simulation, every flotsam shape was expressed by an assembly of individual sphere elements and current velocity field generated by tsunami was given from the result of the tsunami propagation simulation computed in advance. This paper shows experimental results of car's drag force coefficient as a function of every current angle. And we report the application of the drift simulation method by comparing the drift motion from the experiment in a 2-dimensional plane water tank with that of the simulation result.

We conducted detailed hydraulic model experiments in order to sophisticate the performance-based design method of breakwater in consideration of the life cycle cost. The caisson type composite breakwater and covered with wavedissipating block were tested in the condition of large displacement of the caisson and the rubble mound foundation. The wave force acting on the moving caisson was investigated. The effect of deformation of wave dissipating blocks to the wave force on the caisson was also investigated.

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The coastal areas of Japan are estimated to have vast offshore wind energy potential. In order to use large quantities of offshore wind energy, developing a floating body for offshore wind power generation applicable to deep sea areas. Several researches have been made to meet the requirements. In this study, we proposed truss spar and semi-submersible bodies, they have a long track expand about deep water drilling rig operation results. And solved the response and stress characteristics of the floating bodies. And the optimum floating body size and the mooring facilities were determined by the analysis systems.

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