Abstract: A method of constructing a hollow column for resting on a base on a submarine bed, comprises the steps of simultaneously starting the construction of a number of elements that are to form the column, causing the partly constructed elements to float, finishing the construction of the elements afloat, bringing the elements into the horizontal position and connecting them together to form the column, said elements being provided with impervious closures at each end thereof and an impervious caisson adjacent each end thereof, and those of the closures and caissons not required when the column is placed in position are dismantled.

Abstract: A method and apparatus for fabricating an offshore structure intended to be installed at sea comprising a support structure and a platform mounted on the structure. The platform is made up of one or more pieces that are floatable in water. The support structure is immersed to a depth sufficient for the portion thereof intended for the reception of the platform to be situated near the level of the latter. The platform is then fixed to the support structure which is then made lighter and brought to the place where it has to be installed.

Abstract: The invention relates to an oscillating installation installed at a fixed site in a body of water, comprising a shaft which rests on a heavy base, which itself bears on a bed, and which supports a platform at its upper part, the shaft is connected to the base by a ball-joint consisting of two hemispherical caps. The shaft is loaded in such manner that the joint is always under compression. Examples of forms of joint comprising packings between the two caps are described. The invention also relates to a method of laying such an installation, the latter being conveyed by flotation to the site, and the correction of listing by the use of caissons disposed along the shaft.