Abstract: The invention relates to an open frame offshore foundation structure of concrete to be firmly but removably located on the sea floor. The structure comprises a lower set of hollow columns inclined towards each other in direction upwards, a ballastable intertie box structure rigidly receiving the tops of said inclined columns and an upper vertical column unit, the lower ends of which are rigidly connected to the intertie box structure and the upper end of which shall support a working platform in position above sea level.

Abstract: Apparatus for moulding inclined, free-standing hollow columns of concrete by means of sliding formwork is provided. Initially, there is formed a base structure, and a bottom section of the column to be formed is anchored thereto. In the bottom section of the column is positioned a combined support- and guiding means which is displaceably positioned firmly against the inside wall of the column and which furthermore is liftably arranged, in a known fashion such as by being biased to the moulded column section by means of lift-jacks or the like. The support- and guiding means may be forcibly adjustable in the lateral direction during the continuous moulding of the column to control and if necessary adjust the direction of the formwork and thereby the column wall during the moulding of the same.