Abstract: Described is a method of determining the relative risk of an outcome based on an analysis of multiple risk factors. A graphical method is used to take values corresponding to risk parameters and an event outcome to produce a smoothed surface map representing relative risk over an entire space defined by n risk factors. Applying a query data point to the surface map permits the determination of the estimated outcome probability for the query data point, based on its location on the surface map. The method then reports a relative risk or other probability measure associated with the query data point. Also described is a method of analysis in which subpopulations previously identified as high-risk can be further analyzed with respect to risk posed by additional factors.

Abstract: Process for optimizing the features of multilayered tubes made of fibrous composite materials, allowing to maintain within the specified limits the limit elongations and stresses which they withstand in response to the applied strains. The process comprises selecting at least two optimized features characteristic of each layer (its thickness and the winding angle of the fibers for example) by starting from an initial tube selected a priori. Through small deviations applied to the parameters, the relations between small deviations applied to the parameters and the variations of the resulting limit elongations and stresses are determined, as well as the inverse relations relating the variations of the limit elongations and stresses to the parameter deviations. Knowing these inverse relations allows, in one or several stages, to find out the deviations to be applied in order to make up the measurable differences between the limit elongations and stresses of the optimized tube and the tube selected a priori.

Abstract: A riser for great water depths includes a main tube, peripheral lines, and a base at the lower end of the main tube. The main tube has devices for holding the peripheral lines in position with respect to the main tube. The lower end of each of the peripheral lines is connected with another device placed on the base allowing axial relative movement of at least one of the peripheral lines with respect to the main tube. Also, the riser is provided with a damping device.

Abstract: A composite material tube, withstanding the internal pressure, and comprising at least two layers of pressure reinforcement fibers, or pressure resistant layers, wound at an angle at least equal in absolute value to 70.degree., with respect to the center axis of the tube. The two layers both undergo radial expansion under an effect of the pressure, with one of these two layers being inside the other. A circumferential modulus of elasticity of the external layer is greater than the circumferential modulus of elasticity of the internal layer.

Abstract: A process for manufacturing a line of variable stiffness over part of the length thereof and the associated element which allows the line to have the variable stiffness thereof is disclosed. The element is integrated during the manufacturing of the line or deposited thereafter around the line; the element consists of composite material underlayers in which the directions of the fibers have at least one component making a zero or a low-value angle with the axis of the pipe, and the layers end in a graded way. The process has application to the manufacturing of a riser base.

Abstract: A method of joining a tube of composite material and a tubular metal fitting includes, winding filaments of pre-impregnated fibers to produce a tube with a longitudinal axis. The fibers that provide tensile strength for the tube are at a tensile fiber angle relative to the longitudinal axis. A tubular metal fitting is introduced at least partially into an end of a tube section, with inner and outer parts of the fitting being located inside and outside of the tube section. The inner and outer parts are secured by inserting penetrating elements extending radially through the tube section and the parts of the fitting. The penetrating elements are arranged in uniform circumferential alignments which are equally spaced from each other along the longitudinal axis.

Abstract: A composite material tube, substantially insensitive to the variations of elongation under the effect of the internal pressure, comprising a number n of stable layers of reinforcement fibers, the fibers of each layer (i) being placed at the same winding angle in absolute value, referenced theta, with respect to the axis of the tube with an equal proportion of fibers wound at said angle in one direction (.vertline.theta.vertline.) as fibers wound in the opposite direction (-.vertline.theta.vertline.), the fibers of each layer being buried in a matrix which adheres to these fibers. The fibers of the same layer and the associated matrix have a volume referenced Y, the parallel fibers of the same layer and the associated matrix having overall a modulus of elasticity in the natural direction of the fibers, referenced E, wherein said n layers of fibers comply as a whole with the following relationship:0.35.ltoreq.A.ltoreq.0.

Abstract: Fibers, which are substantially longitudinally profiled, are wound both around a cylindrical mandrel and a metallic double cone-shaped tip which is engaged onto said mandrel. Said fibers are turned back about studs distributed on a ring which is mounted on a threaded portion extending from the tip, whereupon said longitudinal fibers are binded thereto by means of circumferential fibers before the polymerization process of the tube has been completed. The composite tubes thus produced may be used in off-shore oil prospecting.

Abstract: An improved platform comprising several columns at least partially submerged in service, wherein, over at least a submerged portion of at least one column, the section defined by the intersection of this portion with a horizontal plane decreases when the depth increases.

Abstract: A variable rigidity element is provided to surround and protect a riser or transfer column installed at a water bottom and extending usually to a platform associated with production of hydrocarbons. The element is composed of a number of shells which surround the riser and two or more concentric rings of shells may be provided. The shells, preferably made of metal, are shaped to avoid contact and have an ogive end remote from the bottom installation.

Abstract: This riser has a central pipe connected to an underwater installation through a flexible assembly, and a plurality of satellite pipes connected to corresponding tubes of the underwater installation through a plurality of hoses each arranged along an helical winding. Upper and lower fastening means secure these hoses to the upper and lower parts of the flexible assembly and maintain the ends of each connecting hose in the extension of the helical winding.