Patent ID: 6431107
Filing Date: 2002-08-13
Classification: B63B

Abstract:
A floating offshore structure, comprising:a buoyant hull adapted to be fully submerged below a water surface in substantially all operating conditions of the floating offshore structure, the buoyant hull having a sufficient amount of fixed ballast to place a center of gravity of the floating offshore structure below a center of buoyancy of the floating offshore structure; a support structure coupled to the hull, the support structure having a waterplane area which contributes a first vertical stiffness to the floating offshore structure; a superstructure mounted on the support structure; and at least one soft tendon which has a first end attached to the hull and a second end attached to a seafloor, the soft tendon contributing a second vertical stiffness which exceeds the first vertical stiffness, wherein a combination of the first vertical stiffness and the second vertical stiffness provides a heave natural period to the floating offshore structure of at least twenty seconds, the second vertical stiffness being between 100 and 1,000 tons per foot.