Level ice and rubble actions on offshore conical and sloping structures

Observations of interactions between level ice and conical structures were collected from the Confederation Bridge Monitoring Programme through which the mechanics of level ice interactions were defined. Some 4000 hours of video were analysed for event information and general observations. The predominant mode of failure for maximal loads observed during these events is pile-up and the shape of the ice rubble can be described as bi-linear. Ride-up associated with high load levels is not observed. Load panel data is analysed to determine simultaneity of the ice sheet failure round the cone. Non-simultaneous failure dominates and it is conclude that the probability of simultaneous failure for a maximal load event is low. A finite element model shows that ice rubble under the oncoming ice sheet affects the location of the maximum stress by affecting the foundation modulus. The observations are used as a basis for the derivation a new ice load algorithm which can be adapted to both conical and sloping structures. The method of slices is used to calculated actions due to ice rubble on a cone or slope. The results are combined with beam on elastic foundation equations to couple the ice rubble and level ice failure against a cone. Existing models for calculating level ice and rubble actions were analysed and compared to the observed mechanics of failure. Modifications to the Croasdale model are proposed based on observations. Validation of the model against full-scale events shows good agreement.; Key words. Ice, conical, sloping, flexural failure, pile-up, ride-up, full scale observations.