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Very large floating structures (VLFSs) or very large floating platforms (VLFPs) are manmade islands, which may be constructed to create floating airports, bridges, breakwaters, piers and docks, storage facilities (for oil & natural gas), wind and solar power plants, for military purposes, to create industrial space, emergency bases, entertainment facilities (such as casinos), recreation parks, mobile offshore structures and even for habitation. Currently, several different concepts have been proposed for building floating cities or huge living complexes.〔(【引用サイトリンク】title=DeltaSync floating city )〕 Some units have been constructed and are presently in operation.〔Japan constructed the Mega-Float (a floating runway in Tokyo bay); Japan also has floating fuel storage bases at Shirashima and Kamigoto Islands, and floating ferry piers at Ujina port (Hiroshima). Several very long floating bridges are currently in use; three are located near Seattle, Washington USA. The Floating Bridge, Dubai, over the Dubai Creek, is 300 meters long. Singapore built the world’s largest floating performance stage at the Marina Bay, and is currently installing a mega floating fuel storage facility off Pulau Sebarok. South Korea is currently installing three floating islands on the Han River, to be used for convention centers, and another project at Seoul will function as hotel/convention center/customs site/quay. (Science Direct, ''Very Large Floating Structures'', p. 63 )〕 Floating structures offer several advantages over more permanent structures which might extend from the shore into open water: *they do not damage the marine eco-system; *they do not cause silt deposition in deep harbors; *they do not disrupt the ocean currents; *they are easy to construct, since much of the construction is completed onshore; *installation is rapid; *they are immune to seismic shock.〔() p. 63〕 ==Overview== VLFS differ from watercraft in that the usable area is the top surface instead of the internal (hold) areas. Thus a useful VLFS will cover significant area. It can be constructed by joining the necessary number of floating units together. The design of the floating structure must comport with safety and strength requirements, operating conditions, etc. Steel, concrete (prestressed or reinforced hybrid) or steel-concrete composite materials may be used to build the floating structure. The motion of the floating structure due to wind or wave action must be substantially neutralized, to ensure the safety of people and facilities on a VLFS, and to allow useful activities. VLFS must be securely moored to the ocean bed.〔() "Drift forces for mooring system design - The design of a mooring system requires the determination of wave drift forces acting on the VLFS." p. 67〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「very large floating structure」の詳細全文を読む スポンサード リンク
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