Development of a Huge Ring-like Semisubmersible for Ocean Space Utilization

A conceptual design of a ring-like semisubmersible for ocean space utilization of middle water area is presented. The principal concept of this structure may be summarized by the following items; semisubmersible, ring-like shape, supporting structures and connection system. The structure is anchored by supporting structures at several points and a special connection system between a semisubmersible and supporting structures is adopted, which enables such a function that the structure is almost rigidly connected with supporting suructures in case of severe storm but almost loosely connected in case of severe earthquake. The Ise Bay was chosen for the installation site of the structure and a trial design and engineering feasibility study were carried out. To investigate its structural feasibility, wind tunnel tests and numerical calculations based on 3D SDM and FEM were carried out and the results of these analyses were evaluated by referring to design criteria. It was proved to be feasible from the view point of structural engineering referring to design of structural strenght and habitability. It was also proved that the supporting structure was stable referring to the geological feature of the soil at the site. Moreover, a numerical procedure combining 3D SDM, Kagemoto & Yue's interaction theory and dynamic structural response analysis method is outlined. This procedure is useful when more accurate evaluation of wave-induced responses of very large floating structures is needed, because hydrodynamic interaction among floating bodies and hydrodynamic-elastic interaction can be taken into account. The validity of this procedure was verified by comparing with wave tank tests and an example of application to system composed of a semisubmersible and breakwaters were presented to demonstrate the effectiveness of this numerical procedure.