Abstract: A flexible structure of controlled yieldability for use as a hydrocarbon drilling and production platform in deep seas, or as a mooring point for oil tankers, constituted by a foundation base assembly, a vertical cylindrical tubular element placed under tension by a buoyancy chamber disposed at its top in proximity to the water surface, and an overlying lattice which at its top supports the plant platform.The tubular element is connected at its lower end to the base and at its upper end to the buoyancy chamber by means of suitable profiled tapered terminal elements able to withstand the bending loads which are generated at said connections.The entire structure is constituted by four separate pieces, namely the foundation base assembly with the lower terminal element, the lower half of the cylindrical tubular element, the upper half thereof, and the upper buoyancy chamber which is connected at one end to the upper terminal connection element and at the other end to the top lattice.

Abstract: A monolithic structure for off-shore mooring composed of a broadened foundation (2) and an emerging vertical structure (1) having a very slender character and a flexural resistance modulus decreasing from the bottom towards the surface. This structure has a buoyancy chamber (15) placed in a submerged position and close to the top end.