Concrete Gravity Based Structures (GBS) have been used in the oil and gas industry since the early 1970-ties. Several structures have been installed worldwide at various water depths and soil conditions. Concrete Gravity Based Structures have proved to be well suited in harsh offshore environments. The structures have therefore been chosen as the preferred concept for several recent projects in arctic areas. GBS structures are robust and constitute a solid substructure for the topsides. The geotechnical design of the structures is based on proven principles. The concrete GBS are however relatively expensive, and in order to limit the costs it is important to optimize the design.
The first sections within this paper presents the state-of-the-art for GBS geotechnical design. Further, the paper assess a selection of design exercises which can be performed to optimize the foundation design. The examples are especially governing for structures on sands.