On the mechanics of ice load on ships in level ice in Baltic Sea:Dissertation

The mechanics of the ice load induced by level ice-ship interaction is analyzed and a mathematical model for the load developed.The ice pressure which loads the ice wedge originates from the contact process between the ice edge and the ship hull.The dynamic bending of the ice plate induced by the contact force determines the ice load.The mechanical constants of the ice form the basic data for the analysis.The mechanical constants of columnar-grained sea ice in the northern Baltic are evaluated partly by field tests and partly by data presented in the literature.The components for the macroscopic failure criterion of the columnar-grained ice are determined.The two cases: the three-dimensional and bending stress state are considered separately.A model for the average ice pressure is formulated.The ice pressure is assumed to consist of two nominal ice pressures.The effects of the stiffness of the shell structure and the crushing process are evaluated.The calculated ice pressures are compared with the measured ones on the full-scale.For this purpose a special ice pressure gauge was designed.A non-linear dynamic model for the bending of the ice wedge is presented.The solution is based on the finite element method.Both the ice wedge and the water under it are modelled.The mode superposition approach is applied.An ice wedge is analyzed and the results are compared with data from two different full-scale tests.The first one is a test with an artificial landing craft bow, the second being the ice load measurements on board I.B.Sisu.The effects of the speed of a ship and the ice thickness on the ice loads are investigated.The work on the mechanics of the ice load does not include all aspects needed for ship design.The aim is to analyze ice loads in detail and develop a model to determine ice loads based on ice characteristics and ship particulars.The model forms a basis for future ice load measurements with which values for ship design can be gathered