Ultimate Limit State Assessment of the M.V. Derbyshire Hull Structure

The Capesize bulk carrier, M.V. Derbyshire, sank in the North West Pacific during typhoon Orchid in September 1980 when she was on a voyage from Canada to Japan carrying fine iron ore concentrates. Since then, extensive investigations of the vessel sinking have previously been made in the literature primarily by the formal safety assessment technique to explore the loss causes, but serious speculation on the failure of hull structures has been lacking in such investigations. The present paper investigates the possibility of the vessel sinking initiated by the failure of hull structures rather than by other loss scenarios, such as hatch cover failure subsequent to water ingress into the cargo holds. Ultimate limit state assessments of individual stiffened panels and hulls of the M.V. Derbyshire under extreme bending moments during the last voyage in storm are made using ALPS/ULSAP and ALPS/HULL computer programs. It is concluded that the M.V. Derbyshire could have sunk by hull girder collapse with or even without unintended water ingress into cargo holds. Important insights and findings developed from the present study are summarized.