Abstract

Analysis of loads from icebergs for an Arctic Floater has been performed. The determination of iceberg loads was guided by the ISO 19906 International Standard. Global and local loads on the hull, as well as mooring loads, were studied. To determine loads at the specified levels of exceedance, probabilistic methodology using Monte Carlo methods was used, taking into account the areal density of the ice features (for example the number of icebergs per 10,000 km2), and the probability distributions of the size and mass of the features, their added mass, their velocity, eccentricity of the collision, compliance of the structure, and the strength of the ice. The influence of surrounding sea ice on iceberg loads, as well as iceberg management including detection, towing and disconnection were analysed. Iceberg areal density was determined based on an analysis of available data, including information on the various forms, such as tabular or bergy bit. The strength of ice in collisions involving icebergs was modeled based on full scale crushing data from ship rams with multi-year ice. The pressure-area scale effects associated with ice-structure interaction were taken into account, considering also scatter in pressure measurements for a given contact area. Separate relationships for local and global loads were used. The analysis accounts for the Ekman current acting on an iceberg, together with wind and wave drift forces. Motions of the floating vessel and the icebergs in sea states were analyzed, accounting for the prevailing environmental conditions. Probabilities of collision along the length of the floater and in the vertical plane have been calculated using Monte Carlo methods. A variety of assumptions have been made: no ice management, management with and without disconnection, and the effect of sea ice on detectability and management is included.

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