| 摘要 |
A disc-shaped marine structure fabricated of steel and/or concrete, able to support useful loads as great as 125,000 tonnes, is tethered to float stably in very deep water, with only minor response motions to wave of large amplitude and long period. A planar base disc of diameter about 135 up to 200 meters carries a centered primary buoyancy tank of span 2.5 to 4.5 times the draft. The strongly braced sidewall of the tank is spaced about 10 meters inward of the disc edge, defining one wall of an upwardly open confinement chamber. A thin cylindric outer shell wall extending upwardly from the margin of the base has about 26% to 35% of its area comprised of tubular passages set radially, of length and diameter about one meter or more. Radial bracking frameworks of 50% aperturing interconnect the tank with the base disc and outer wall. A mass of seawater approximately equal to the structure's displacement is largely confined, its volume/aperture ratio being about 800 m3/m2. When waves impinge the structure this mass strongly opposes accelerations by D'Alembert forces which give rise to internal pressure fields generating massive lateral flows which effect high rates of damping. As the sea rises at the shell wall a massive radial flow fills part of the chamber to a higher level, therby countering heaving force. Surge motion leads to large-scale dissipation of kinetic energy by massive inflows and outflows. Access to seabed, e.g. for well-drilling and petroleum production, may be provided at least one vertical tube through the tank.
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