Design and weight optimisation of Offshore Topside platforms using High Strength Steel

Current offshore topside platforms are steel intensive structures, made of a variety of steel products such as plates, rolled beams, welded plate girders, and welded and seamless tubes. These structures are complex and generally designed using S355 steel grade mainly due to raw material availability, experience and knowledge when using this steel grade. In this study an optimisation of two offshore platforms is made by replacing the standard S355 steel with high strength steel in order to achieve a lightweight and optimised design with the same structural performance. The study has been carried out considering the full life cycle of an Oil&Gas topside platform and an Offshore substation topside, using as reference two topside structures built in the North Sea. Results indicate that for the same structural performance, by using high strength steel there is a reduction of the total weight which may reduce the overall life cost of the topside platforms, in particular fabrication and installation costs.