Abstract: A marine platform comprising a deck supported by a tower composed of a rigid fixed structure of the jacket type anchored to the sea floor, an oscillating structure supported by and connected to the fixed structure by flexible piles anchored in the lower part of the fixed structure and arranged on the periphery of the oscillating structure, and by a shear device, the oscillating structure being equipped with a floater. In one embodiment the connection between the fixed and oscillating structures is located in a zone between 30 and 60% of the water depth from the water level. The shear device consisting of at least one set of pairs of structural elements placed obliquely or perpendicularly with respect to the axis of the tower between a lower part of the upper structure and an upper part of the lower structure or of the base and allowing transmission of shear forces and torsional moments between the two parts.

Abstract: A platform comprising a deck supported by a tower composed of a rigid fixed structure of the jacket type anchored to the sea floor and of an oscillating structure supported by, and connected to, the fixed structure by flexible piles anchored in the lower part of the fixed structure and arranged on the periphery of the oscillating structure, and by a shear device, the oscillating structure being equipped with a floater. The connection between the fixed and oscillating structures is located in a zone between 30 and 60% of the water depth from the water level.

Abstract: Flexible piles (5) are arranged close to the center of the tower (1) and evenly spaced apart on a circumference the area of which is about 10% of the area of the tower. The product of the total buoyancy of the tower by the arm level between the buoyancy center and the center of the articulation is at least equal to 1.25 times the product of the weight of the platform by the arm level between the center of gravity and the center of the articulation.

Abstract: The platform comprises an annular truncated cone of concrete which constitutes the main resistant element of the platform and is designed to take the thrust of ice, and a cylindrical steel part housed inside the annular truncated cone. Watertight passages parallel to the generatrices of the cylindrical wall are provided to house piles in the peripheral ring, close to the wall. A watertight passage well is provided in the cylindrical steel part for the passage of the drill pipes. A circular running track is provided for gantry cranes used for piles handling. The platform has two drilling rigs placed on one half of the platform and able to work simultaneously.

Abstract: An oscillatable marine installation comprises a concrete and steel lattice shaft supported by means of a demountable pivot joint on a base fixed to the-sea-bed and including an anti-torque device. The pivot joint is made up of three parts: a casing fixed to the shaft, a part-spherical housing fixed to the base, and a pivot member. The pivot member has an upper part cooperating with the casing, a flange which can be fixed to the casing, and a lower part-spherical part housing which supports a resilient assembly and a bush fixed on the housing. The anti-torque device comprises a universal joint, concentric with the pivot joint. Two opposite pivots of the crosspiece of the universal joint are supported by the lower part of the shaft and the other two pivots by the base. At least two opposite pivots have damping devices and the pivots supported by the base are mounted on supports the height of which can be adjusted.

Abstract: The device comprises two concentric swivels, a first or mooring swivel being arranged on the outside of the second or bearing swivel, the second swivel being fixed to the end of a cartridge held in a movable manner in a tube forming a projection at the lower end of the shaft and an extension of an axial passage in the shaft. The cartridge is formed by a cage fitted with openings in which keys are housed. A ring is lowered between the keys and immobilizes them against the wall of the tube which forms an extension of the axial passage in the shaft. The method consists of lowering or raising the cartridge carrying the bearing swivel by means of a set of rods.

Abstract: A concrete structure for the transmission of loads from the steel lattice tower of a marine platform resting on the sea bed by means of concrete base plates, the lattice tower being made up of tubular members which form bracing joints with the legs of the platform. The structure comprises a cylindrical hollow body forming at least part of a platform leg, and having on the inside enclosed spaces defined by internal walls and by the hollow body wall, and concrete fixing plugs formed within the enclosed spaces and engaged by the ends of the lattice members, the enclosed spaces being in the form of hollow rings or vertical shafts within the hollow body.