Ship hulls exposed to ice-induced loads and resistance
MetadataShow full item record
- Institutt for marin teknikk 
Marine activities in the Arctic have always been difficult. In recent year there have beena significant increase in activities in this region. This is a combined result of both globalwarming and a strong development in the design and the technology for ice-classifiedvessels. Arctic transportation routes, exploration of hydrocarbons and tourism are allexiting opportunities related this development. This master thesis contains a theoretical study sea ice. In addition to a introductionto ice covered areas, both different types of sea ice and their mechanical and physicalproperties are presented. In this master thesis, KV Svalbard will be used as a reference. This is a Norwegian coastguard vessel, specialized for operations in Arctic waters. To operate in ice-infested waters, the right classifications are necessary. In these areasthe vessels are exposed to conditions they would not experience in other regions, andspecial classifications for navigation in ice are therefore developed. This thesis containsa review of the classifications presented in DNV GL s "Ship for navigation in ice". Here,both Baltic, Arctic and Polar classes are described. Since the Arctic region has been infocus for this thesis, a particular emphasis has been placed on the Arctic rules by DNVGL and the Polar rules by IACS. An introduction to finite element analysis is presented. Linear and non-linear analysisare described and compared. In the event of ship-ice interaction, large displacementsand deformations may occur. Here, linear elastic theory may no longer be valid, andnon-linear theory must be applied. To estimate the ice resistance for a vessel, analytical formulations may be used. In thismaster thesis, three models are presented and compared. All of the formulations aremeant to give an early estimation of resistance for ice and power requirements. Byusing the main parameters from Norwegian coast guard vessel KV Svalbard, the threemodels are compared to each other. In addition, a parameter study for the models wasconducted to see how each of the parameters involved influenced the final results. Using the measured power from KV Svalbard, the total resistance was calculated utilizingNewton s second law and conservation of energy. This resistance was then comparedby calculating the ratios between estimated and empirical resistance. From theresults one can see a big variation in the ratios. The most stable results were found forhigher vessel speeds. To see how ice loads affect local parts of a hull, a plate model was created and analyzedusing Abaqus. As for the resistance, KV Svalbard was used as a reference. Thisvessel has ice classification Icebreaker Polar 10, and using this classification, values forstiffener dimensions, load height and ice pressure were obtained. In addition to theice pressure from DNV GL, an empirical ice pressure was used in the analysis. Not allparameters involved in the analyzes were defined according to regulations, but chosenarbitrary. As a consequence, there are some uncertainty connected to the results.To see how modifying different values would affect the final response of the panel, aparameter study was conduced. The parameters modified were contact area, stiffenerspacings and dimensions, and load angles. From the results, one can see a clear differencebetween the results for the different ice pressures. Using the DNV GL ice pressure,stresses above the yield strength of the material will occur, leading to plasticity.