Determining effective pressure in ice compressions based on full-scale measurements of ship motion parameters

Ice compressions are among navigation hazards that impede navigation in freezing waters and sometimes result in loss of ships. Recent advances in the investigation of this ice feature enable its prediction and make it possible to recommend safe navigation routes for ships, bypassing hazardous zones. The effect of ice compression on hull structures is less understood. First of all, this is because ice compression actions are difficult to determine accurately and are currently estimated by means of special visual scales (marks) drawn on the hull. This paper proposes using the parameter of effective pressure for ice compressions. Effective pressure is always present in the case of ice compression phenomena, so it could be used as an assessment criterion for the added resistance of the ship. A similar approach has been successfully applied to determine the global ice load on engineering structures. This paper suggests a method for determining the effective pressure of ice compression based on ship propulsion performance data (engine power, movement speed and propeller RPM), as well as on the measured speed of ice channel closing behind the ship. These measurements must be taken in similar ice conditions with and without ice compressions. The speed of ice channel closing behind the ship could be used to quantify ice compression intensity. Added resistance of ships is calculated using the special diagrams of ice propulsion performance made which are made for specific ships based on the results of standard model tests in hydrodynamic tanks. The paper discusses the prospects and possible limitations of this method. Effective ice compression data would be very interesting for the prediction of operational conditions of Arctic transportation systems and, possibly, for the investigation of ice sheet dynamics.