Author(s): Erkki Pulkkinen
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Keywords: No Keywords
Abstract: A numerical model for the non-linear analysis of ice forces exerted against structures is obtained here principally by means of a systematic investigation of constitutive models for ice in creeping and cracking modes, a verification of the models under different loading conditions and a determination of numerical values for ice models. The most important characteristic of the numerical model is the inclusion of creep damage and cracking into the same scheme. The creep damage part makes it possible to analyse ice as a material with creep properties depending on stress and time, and implies that energy dissipation in the creep mode increases with the ice damage. The continuous crack model in turn relates the energy dissipation to the theories of fracture mechanics and makes it possible to analyse ice under tension and compression without modelling each discrete crack. The crack model used here is objective with respect to element size under both tension and compression. An exponential function of softening based on fracture mechanics can reflect different cracking assumptions, from entirely brittle cracking to plastic cracking. Both individual models, the rate-dependent creep damage model and the rate-dependent cracking model, are first verified against the known results of problems calculated by other researchers. Good agreement is observed in both cases. Secondly the model is verified against the available known ice data. Although the calculated and measured results cannot be compared directly, a comparison of the maximum ice strengths and the stress-strain curves shows that the ice model is capable of capturing the most important features of ice behaviour. The present model shows similar strain-softening phenomena in the creeping mode to those found in the measured stress-strain curves. In the cracking mode the present model behaves in a brittle manner, as ice does in reality.
Year: 1990