Structural design considerations for ships operating in arctic regions

The safety of Arctic ships will be influenced by the interactions with ice ridges and icebergs. Generally, the structural design loads will be governed by these ice features. In order to design ship structures, the principles of risk-based design should be considered and followed. The following limit state design criteria are usually applied in structural design: 1) Serviceability Limit States (SLS); 2) Ultimate Limit States (ULS); 3) Fatigue Limit States (FLS); 4) Abnormal/Accidental Limit States (ALS). The ULS and ALS correspond to impact events with a very low probability to occur, and its intention is to ensure that a ship hull structure does not suffer from a complete loss of integrity. However, for analysis of the ice loads with low probability levels, the number of relevant load cases is significant and the computation amount is huge. In this work, the so-called environmental contour method is introduced in order to reduce the required number for ice loads analysis as well as to identify the most likely combinations of the relevant design parameters. Utilization of this approach is illustrated in connection with the ULS and ALS in the present paper. Application of the proposed method could be a valuable supplementary for structural design of Arctic ships.