Floating structure

A floating structure comprising:

• a platform;
• columns extending downwardly from said platform;
• buoyancy footings provided under said columns;
• a plurality of tension wires, each said tension wire passing through a respective footing and having one end connected to a winch located on said platform and the other end connected to a respective anchor, said tension wires being disposed in a fan-like arrangement spreading out below said platform, said tension wires primarily suppressing rolling and pitching of said platform;
• a plurality of sinkers, at least one sinker being suspended from an intermediate portion of each said tension wire, said tension wires being substantially straight or stretched at portions above said sinkers and sagged at portions below said sinkers, said sinkers being positioned such that at least one sinker on each tension wire intermediate portion is normally not in contact with the sea bottom;
• a riser pipe means extending downwardly from the center of said platform and having a lower end connected to a sea-bottom base fixed to the sea bottom, said riser pipe means comprising a series of connecting pipes having wall thicknesses which decrease, as the riser pipe means gets closer to the sea surface, progressively or in a stepped manner, said riser pipe means preventing up and down movement of said platform;
• buoyancy body means comprised of a plurality of buoyancy bodies provided at intermediate portions of said riser pipe means, said buoyancy bodies reducing the submerged weight and preventing buckling of said riser pipe means and reducing the tensile force applied on the top end portion of said riser pipe means;
• said footings being moored in a submerged condition against their buoyancy by the action of said tension wires and said riser pipe means.