Research on Floating Body in Directional Spectrum Waves

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Stable platform by floating offshore structures are required in the fields of oil production or ocean utilization, for example floating airport. For this purpose, research on the behaviors of such structures in directional spectrum waves namely realistic short crested irregular waves is important.In this joint project, the behaviors of offshore structures in directional spectrum waves were investigated both by theoretical and experimental manner taking into account the situation of both Japan and Brasil in the field of ocean developement.In the first year, observation on the spot was carried out in Brasil, and the basic experiments of model structures were carried out in Yokohama National University (Japan).In the second year, a program code was developed for estimating hydrodynamic forces acting on semi-submersible offshore structures by the method of so called singularity distribution method. From the view point of safety, lrgely listed conditin was also considered in this code. Simple estimation method for slow oscillation was also developed.In the final year, developed code was confirmed by the comparison with experimental results. Experiments of largely listed condition (about twenty degrees) were conducted for this purpose.Furthermore, not only drilling rig but also long and huge floating airport was treated from the view point of its behaviores in directional spectrum waves and the necessity of considering elastisity was made clear.