A Condeep type GBS under construction in Norway.

A gravity-based structure (GBS) is a support structure held in place by gravity. A common application for a GBS is an offshore oil platform. These structures are often constructed in fjords since their protected area and sufficient depth are very desirable for construction. A GBS intended for use as an offshore oil platform is constructed of steel reinforced concrete, often with tanks or cells which can be used to control the buoyancy of the finished GBS. When completed, a GBS is towed to its intended location and sunk. The platform structure which a GBS supports is called the topsides.

Gravity-based structures are also widely used for offshore wind power plants. By the end of 2010, 14 of the world's offshore wind farms were supported by Gravity-based structures. The GBS are suited for water depths up to 20 meters. The deepest registered offshore wind farm with Gravity-based structures is Thornton Bank 1, Belgium, with a depth up to 27.5 meters[1]. However, as offshore wind power plants are growing in size and moving towards deeper waters, the GBS is not considered competitive in comparison with other support structures[2].

References

nl:Gravity based foundation

no:GBS