engleski

Evaluation of ice induced loads on ships in compressive ice

Ice covered sea areas was given more attention during last decade due to increased nature resource exploitation and new transport routes. Merchant ships with a long parallel midbody section aren’t suitable for winter conditions. Compressive ice can cause pressure to the side of the ship and ship can get stuck in ice. Compressive ice is one of the greatest hazards for maritime traffic in winter conditions, yet little is known about the effects and forces involved. Within project called SAFEWIN ice model tests were conducted in the ice basin of Aalto University in compressive ice field. Tests included six test series with varying ice thickness and compression levels. The model adopted in the tests was a bulk carrier with a bulbous bow and a long parallel midship section. In this thesis the loads on model in compressive ice has been studied. Used measurement data are gathered from the load panels at the midship, bow shoulder and load sensors on the pusher plates for level ice tests and closing channel tests. Further, natural sea ice is highly heterogeneous and causes high scattering in any measured values. This study seeks to find the maximum line loads caused by compressive ice field and compare those with ones calculated by ISO code to verify ISO code reliability. As a limitation, loads due to ice ridges are not investigated within this thesis. An analysed results show that ice thickness has a major influence on the loads. Compression level has influence on loads, too, but significantly less than thickness. Further, line load curves for different ice thicknesses is presented and compared with ISO code. The calculate values represented the results of model tests fairly well. Moreover, measurements at midship load panel show that weak compression was occurred in 3 out of 6 compressive level ice tests (loads were significantly smaller than in other tests). Comparing compressive level ice and closing channel measurements, loads at the bow shoulder and midship were higher in closing channel tests.

compressive ice; ship structure

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