Statistical analysis of ice crushing pressures on a ship's hull during hull–ice interaction

Ice bound shipping is considerably more dangerous than shipping under more favourable water conditions. During winter the Baltic Sea can be covered with ice over an average of about 45% of its surface. The ice mostly reaches its maximum extent in late February or early March. The Bay of Bothnia located in the northern basin of the Gulf of Bothnia is prone to extreme frozen ice conditions. During winter the typical ice thickness in the northernmost areas of the Bay of Bothnia is about 70 cm for land-fast sea ice.In this paper the ice crushing pressure on a ship's hull is analysed statistically. A series of tests took place over four days in the Aalto ice tank and involved two different ship models. The peak pressures caused by ice were calculated from four sensor sheets located at different positions on the hull. In the statistical part, the sum of the forces acting on a section of a ship's hull was modelled as a Poisson random process. Analysis of the cumulative distribution function (CDF) was modelled for the total force. The full scale comparisons of pressure-area values and line loads as a function of the load width were analysed by comparing the model scale data with full scale measurements onboard MS Arcturus and IB Sisu. Finally a short comparison is also conducted with the load level obtained from damage statistics gathered in the Baltic Sea.