Uncertainties in simulation model for ice loads prediction in level ice with respect to structural reliability

Arctic shipping is increasingly in focus due to the diminishing ice cover due to the effects of climate change. With new shipping routes opening up, navigation in ice-covered waters receives increasing attention in industry and academia. One of the key issues in the design of ice-going vessels is the required plate thickness to withstand the ice loads. Several regulations have been developed, containing formulae for determining the place thickness for different ice classes. On the other hand, various engineering tools have been developed for simulating the ship performance in ice, with several of these tools explicitly aiming to determine the ice loads on the hull. Such tools in principle provide alternative means to determine the safety level of the hull elements based on first-principle modeling. In this report, a risk-based design approach is taken as a starting point for contextualizing the determination of the required plate thickness based on a structural reliability analysis. The focus of the work is to analyze the importance of the uncertainties in the ice loads resulting from a ship performance in ice simulation model, in relation to the structural reliability as calculated based on the simulated ice load time series. The study centered on the influence of the applied empirical parameters in the model design on the predicted ice loads with respect to the long-term safety and reliability analysis of the ship. The various assumptions in the simulation model for ship performance in ice are systematically varied to quantify the uncertainty about the safety index and failure probability of a plate under ice loading. The results showed that the predicted loads from the simulation model lead to some about of uncertainties across the investigated parameters, indicating the limited usefulness of the simulation model in a risk-based design context. The estimated uncertainties were however based on the relative variations of the simulated ice loads and the estimated safety index corresponding to each case studied. With these results, the suspicion for inherent uncertainties in the ice prediction model’s performance associated with the applied parameters was justified. Hence, to obtain better or improved performance from the ice prediction model, the sources of uncertainties should be minimized or eliminated. Also, with the ultimate aim of developing models and tools for risk-based design of ships in Arctic and other ice-covered waters, areas of further research and development in context of the ship performance in ice simulation model are highlighted to reduce the uncertainties

Cargo and bunker tank information for oil outflow calculations - Designs of tankers, container ships and bulk carriers representative for the Northern Baltic Sea area

Oil spills from maritime activities can have detrimental effects to marine ecosystems and cause economic damages both to ship operators and to coastal communities. One widely used approach for reducing the adverse effects of possible oil spills is maritime oil spill risk assessment and response preparedness planning. It is widely acknowledged that especially ship collisions and groundings pose a high risk of oil spills, both in navigation in open water and in conditions characterized by sea ice. Correspondingly, comparatively much research has been dedicated to estimating the oil spill sizes in ship collision and grounding accidents in risk assessment and response preparedness planning contexts. Nevertheless, most of these methods provide rather crude estimates of the spill sizes, or have a limited scope of application when more detailed estimates are produced. Hence, comprehensive methods for determining the oil outflow consequences in ship collision and grounding accidents are still lacking. Such consequences models could however be useful for response authorities to determine the target spill size for a given sea area and plan the necessary resources for responding to such a spill. In order to increase the realism of consequence models of accidental oil outflow in ship collision and grounding accidents, it is necessary to combine different data sources and models of specific phenomena. For a given accidental impact scenario, the damage extent inflicted to the struck ship hull needs to be evaluated, and subsequently the oil outflow should be assessed in the specific environmental context. The hull damage extent and the oil outflow are conditional to the ship layout and the loading condition. Integrated modeling approaches combining these elements have been proposed. However, a comprehensive dataset of the required information about the ship main dimensions and cargo and bunker tank details for the accidental damage extent assessment and oil outflow in particular scenarios is still lacking. The aim of this report is to fill this gap by presenting information on vessel particulars of selected vessel types, with a focus on tankers, bulk carriers and container vessels. The scope is typical vessels navigating in the Northern Baltic Sea area. These vessels are selected based on an analysis of the vessel traffic in this area, based on data from the Automatic Identification System. To facilitate risk analyses based on the presented information, the report also contains a strength-of-evidence assessment