As the total world transport of oil by tankers has grown, the potential risks to property damage and marine pollution have been increasing. Tanker collision is one of the most common causes of oil spills because collision damage has increased in recent years to an unprecedented level. This paper proposes an advanced procedure for the quantitative risk assessment of ships in collision. The procedure consists of several major tasks, namely, hazard identification associated with random variables and their probability density distributions, selection of credible collision scenarios by sampling technique, quantitative risk calculations including both the frequency and consequence associated with property damage and oil spills, the hull girder collapse risk in tow operations during salvage, and the exceedance frequency associated with risk acceptance criteria. The procedure is applied to a VLCC class double-hull tanker, where the types of striking ships include bulk carriers, containers, tankers, passenger ships, and general cargo ships, based on actual historical databases collated from the records of authorities. The nonlinear finite element method is used to simulate the structural crashworthiness of the struck ship associated with selected collision scenarios, characterizing the collision damage and oil spill. The risks of structural damage volumes and oil spill amounts are calculated as a product of frequency and consequence. A ship hull structure damaged by collision can collapse during rescue or salvage operations, and thus the risk to hull girder collapse is also evaluated. It is also interesting to examine the level of collision risks for existing VLCC class tankers, which is equivalent to be the ALARP (As Low As Reasonably Practicable) level to be applied as risk acceptance criteria that will be useful for the robust design and engineering of future ships. Important insights and conclusions are summarized, and detailed results of the collision risk assessments are reported.

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