Modelling of continuous crushing of ice in front of offshore structures

Abstract

A one-dimensional finite element is developed to represent the continuous crushing and extrusion of ice in interactions with offshore structures. The element is developed with the objective of providing a model for the analysis of dynamic ice–structure interactions in which both nonsimultaneous and phase-locked behaviours occur. The element has two components: one to model the damage accumulation in intact ice and one to model the extrusion of pulverized ice between the intact ice and the structure. The intact but damaging ice behaviour is based on a rate theory approach to crack density and damaged material compliance which is a function of stress and damage. The extrusion component models a viscous-plastic material which is modelled using a Tresca failure criterion and viscous flow. The element is developed as part of an existing finite element package (Abaqus) through its user material and user element capabilities. The paper describes in detail the development and implementation of the element and presents sample results of its performance in continuous crushing interactions with a rigid structure. The results show that the element can be used as the interface between moving intact ice sheets and offshore structures modelled using the finite element method. Key words: ice, structures, dynamics, finite elements, rheology.