Offshore HLV sea-transport safety by direct strength and fatigue assessment

摘要

Several SPAR hull structures for deep water oil production have been manufactured in Pori, Finland and transported to the Gulf of Mexico with heavy lift vessels (HLV). A complete spectral based structural analysis procedure has been developed for guaranteeing structural integrity during the sea-transports. The procedure utilises 3D hydrodynamic and structural model results for strength and buckling analyses against extreme sea state conditions and fatigue analysis for voyage duration wave loads. In addition, slamming loads are studied on overhanging structures The completed analyses have resulted in improvements and optimisation of both the fatigue strength and buckling capacity of the spar and support structure details. A more even support load transfer between ship deck and cargo has been reached. The slamming analysis procedure has yielded to reasonable heading dependent sea state restrictions despite of its apparently large inherent conservatism.