Fatigue Damage Estimation of a Sloped Offshore Structure in Level Ice

초록

Ice loads repetitively acting on a structure during continuous breaking may cause fatigue cracks potentially leading to catastrophic structural failure. This paper proposes a fatigue assessment procedure for a sloped offshore structure operating in drifting level ice. Fluctuation of local ice load acting on the external surface of structure was statistically modelled and used for fatigue life estimation of a critical hot spot point within the structure. Due to the complexity induced by ice rubble piling up during ice action, the situation was idealized in such a way that only breaking induced repetitive local ice load was considered. This also allows the method to be applied to both upward and downward ice actions. Breaking local ice load was calculated using ISO 19906 and other statistical parameters were derived using empirical formulas. To check the validity of the proposed analysis procedure, direct analysis using finite element method, with which ice continuous breaking phenomenon was successfully captured (in prior work), was carried out for all different combinations of ice thickness and speed. Then, the fatigue damage was calculated based on the obtained local ice loads and compared with the results obtained by the proposed simplified methodology. © 2021 Lulea University of Technology. All rights reserved.

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