Analysis of accidental iceberg impacts with LNG tank carriers
摘要
The number of collisions between ships and icebergs are increasing in correlation with the increase of the number of ships sailing in Arctic areas. Due to the exploitation of gas fields in Arctic areas, the LNG shipping in these areas is expected to increase. The consequences of an iceberg impact can be critical for ship structure, the crew and the cargo, and it is important to be able to predict the result of such a scenario.Different relevant impact scenarios have been discussed, and it has been concluded that the most critical scenario for a spherical type LNG carrier is an impact at the bow shoulder where the distance between the outer hull and the cargo tanks is at its shortest. Based on this study, a bow shoulder impact has been chosen as the scenario investigated in the thesis.To investigate the influence of the surrounding water, an ALE-model representing this was therefore supposed to be modelled in LS-DYNA. After several unsuccessful tests this work was postponed to further work, but a detailed description of the ALE-modelling and the different options tested has been carried out.A detailed FE model of the bow shoulder section of an ice strengthened spherical type LNG carrier has been carried out. The mesh in this section has been modelled sufficiently fine to capture the governing deformation mechanisms and the total number of elements in the model are therefore large. This will lead to increased computation time, but this is acceptable based on the accuracy of the results obtained. In addition to the local bow shoulder model, a FE model of a global 125 000 dwt. LNG tanker has been established. The outer shell and coarse geometry has been provided by Ph.D. candidate Martin Storheim, and the detailed bow shoulder model has been included in this global model. The global model is meshed with large rectangular four-node elements, and transitions to the detailed model have been created. Properties have been added to the global model in terms of getting a model