Abstract: The method uses a construction and launch barge having a shallow draft hull with a construction deck supporting at its center a floatable offshore structure both during construction thereof and during the towing of the barge to the site where the offshore structure is to be installed. In order to maintain stability, a plurality of hollow column stabilizers are provided on the barge; these may be, e.g., four, one adjacent to each corner of the barge and extending up high thereabove. Large offshore structures of concrete are constructed on the barge in relatively shallow water and then towed across relatively shallow water to a desired location and then the barge is separated from the offshore structure by sinking the barge to a sufficient depth, releasing the then-floatable offshore structure from the barge, and then displacing the barge away from the offshore structure. Then the barge is raised again and returned to shore. The offshore structure may then be lowered into its operating location.

Abstract: A construction and launch barge having a shallow draft hull with a construction deck supporting at its center a floatable offshore structure both during construction thereof and during the towing of the barge to the site where the offshore structure is to be installed. In order to maintain stability, a plurality of hollow column stabilizers are provided on the barge; these may be, e.g., four, one adjacent to each corner of the barge and extending up high thereabove. A ballast compartment helps determine the desired waterline of the vessel, a mechanism being provided to displace the water therein by air or to displace the air by water. The column stabilizers are sufficiently high and occupy sufficient area for assuring the proper location of the metacenter of the fully loaded barge.

Abstract: A multi-component offshore platform having a floatable and ballastable central column with a base that is adapted to rest on the bottom of the sea. The column is towed to its site while floating and then upended and ballasted to sink the base to the proper site. A hitch collar is slidably arranged around the central column. At least three inclined legs, which may each be separately floatable for towing to the site and are ballastable for sinking, are hingedly secured to the hitch collar. The collar is then lowered on the central column to a desired height and secured there. The legs then are swung down by ballasting. Each leg has a foot which is hinged to one extremity of its leg for engagement with the ocean floor. The superstructure can then be placed on the top of the central column.