Ice Induced Vibrations of Flexible Offshore Structures: Comparison and Sensitivity Analysis of Existing Phenomenological Models

Abstract eng:
Occasionally vertically-sided offshore structures experience sustained vibration due to drifting ice sheets crushing against them. These vibrations, more commonly known as Ice Induced Vibrations (IIV), may lead to fatigue problems, safety issues and uncomfortable working conditions. To date only phenomenological models exist of ice failure in the course of IIV which are capable of predicting the onset and severity of these vibrations. This is a consequence of the complexity of the ice crushing process that takes place in the course of IIV. This process is not understood well enough yet to enable development of practically applicable models of this phenomenon based on the principles of fracture mechanics. In this study various existing phenomenological models of IIV, with a focus on the models presented in [1] and [2], are taken for comparison in an attempt to identify their main differences and similarities. The comparison is based on: (i) The adopted mechanism enabling the model to predict the occurrence of synchronization; (ii) The aspects of the ice-structure interaction taken into account; (iii) Accuracy of the model predictions when compared to real measurements. A sensitivity analysis is made with respect to the most critical model parameters for each of the models taken into consideration. Taking into account the available scientific knowledge about these critical parameters and the possible ways of quantifying them, an assessment is made of the general applicability of the compared models for the prediction of IIV. Results of the comparison and sensitivity analysis will lead to an overview of the state of the art considering phenomenological models for IIV. Also the potential of each model with respect to prediction of the occurrence of synchronization in the case of ice-structure interaction is reflected upon. Using the obtained results a recommendation is made for the future development of the investigated phenomenological models with the aim of working towards development of a more practically applicable fracture mechanics based model.

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