A gravity-based structure (GBS) is a support structure held in place by gravity, most notably offshore oil platforms. These structures are often constructed in fjords due to their protected area and sufficient depth. Offshore oil platforms Prior to deployment, a study of the seabed must be done to ensure it can withstand the vertical load from the structure. It is then constructed with steel reinforced concrete into tanks or cells, some of which are used to control the buoyancy. When construction is complete, the structure is towed to its intended location. Wind turbines Early deployments of offshore wind power turbines used these structures. As of 2010, 14 of the world's offshore wind farms had some of their turbines supported by gravity-based structures. The deepest registered offshore wind farm with gravity-based structures is Thornton Bank 1, Belgium, with a depth up to 27.5 m. Newer generations of wind turbines are much larger, and deployed in deeper waters, gravity based structures are no longer considered competitive in comparison to support structures such as the floating moored. See also Offshore concrete structure List of tallest oil platforms Troll A platform Gullfaks C Hibernia (oil field) References Offshore engineering Structural engineering Oil platforms