TYPE OF CANDIDATE OFFSHORE RECEIVING STATIONS The candidate structures of the ORS are: 1) the floating type, 2) the leg type, 3) the reclamation type. Since the structure of the ORS is gigantic, it is reasonable to select a structure that has sufficient construction records in the past in deep water and is free from earthquake vulnerability. For these reasons, a floating type structure seems to be the best choice at present. Especially, the semi-submersible type possesses excellent seakeeping characteristics. In addition, stability of the semisubmersible type can be easily obtained by adjusting the ballast in the floats and by employing an adequate mooring system. Table 1 (1) shows the comparisons of pile and floating type structures. STRUCTURAL CONCEPT OF PROPOSED OFFSHORE RECEIVING STATION Among the various configurations of semi-submersibles, the one having bottle shape float was chosen as it is used for large floating structures such as Hawaii's Floating City by J.P. Craven, J.A. Hanson (2) and Kansai International Airport Plan (Japan Ship Building Industry, 1979). Figure 3 shows a typical cross section of Hawaii's Floating City in which the underwater and abovewater structures are 84 m and 70 m in height, respectively. The floats supporting the circular Floating City (max outer diam is 720 m) have 28 m in diam. As the proposed elliptical ORS is 13 km (in long axis) and 10 km (in short axis) in length at the 35 deg N lat, its construction has to be undertaken by the following sequences (for example): 1) a block of 50 m x 200 m in floor area is fabricated in a shipyard, 2) 16 blocks are towed to the construction site to form a unit of 400 m x 400 m in floor area and 3) 625 units are assembled to complete an ORS structure.
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