SELECTION OF SUITABLE ICE CLASS FOR ANTARCTIC OPERATION BASED ON FULL SCALE MEASUREMENTS OF THE HULL STRUCTURE

摘要

Shipping in ice covered waters is increasing and new ice classed ships are built to replace older ice strengthened fleet. Selection of suitable ice class for ships operation is an important but not simple task. The ice classes assigned by the classification standards are providing limited guidance in characterizing the ships operational limits and corresponding structural strength for actual ice operational modes in ice. In addition, the actual structural redundancy and safety when operating in ice conditions which may be considered beyond what is assumed as basis for the ice class is generally unknown. The process of selecting an appropriate ice class is of high importance both from a safety as well as an economical perspective, but the selection process is still based on accumulated experience and traditions within the areas of existing operations. The increased exploitation of the Polar waters, both wrt. seasonal periods and geographical areas, as well as the introduction of new international design standards, reduces the relevancy of using existing experience as basis for the selection, and new methods and knowledge have to be developed. Based on full scale measurements of ice loads from two consecutive seasons in the Antarctica, the structural strength of the South African research vessel S.A. Agulhas 11 has been evaluated to assess the suitability of the chosen ice class of the vessel. The structural suitability of the chosen ice class will be evaluated based on non-linear analysis of the bow structure. The response of the recorded loads and forecasted lifetime loads which are assumed to be representative for the operational profile of the vessel is evaluated against the assumed design point and the subsequent residual capacity of the structure until failure. The impact of choosing a lower/higher ice class will also be considered.