A Computer Routine for Sizing Gravity Based Structures in Ice Covered Waters : Model Results

Gravity based structures (GBS) resist the environmental forces from waves, ice and seismic events using the weight of the structure. A routine has been developed that can size an offshore hydrocarbon production structure based on the minimum cost of the construction materials. It calculates the stability conditions of sliding resistance and bearing capacity in both the empty and full storage conditions for each of the environmental forces, along with the floating stability during structure set down. The structure can be concrete, steel, caisson or a multi-legged geometry. In general the routine finds the lowest cost structure that meets the stability requirements over a wide range of structure sizes and solid ballast weights. The results of the comparison against existing structures or designs taken to the detailed engineering phase are described along with typical GBS results and trends. The routine is suitable for the preliminary or conceptual engineering stage of a project.