Ice forces on a multifaceted conical structure

To simplify fabrication and reduce costs of conical structures for arctic offshore development, a multifaceted conical shape was proposed to replace the conventional smooth cone. This raised a number of concerns about the mechanisms for ice interaction with this multifaceted conical structure (MCS) and the validity of analytical models which were developed for the smooth conical structure (SCS). A vertical neck at the top of the MCS was proposed for a prototype and industry has desired a large size for this neck, i.e., its diameter to be only slightly smaller than water-line diameter. This raised another concern: what was the effect of this vertical neck on ice loads?; To address these concerns, a university-industry joint program (NSERC file #661-119/88) was initiated to carry out a series of test programs. The data contained in these test reports have been used in this study to understand in depth the various interaction scenarios possible between a multi-year ice ridge and the MCS.; The direct analysis of the test data, presented in this study, covers answers to most of the concerns raised by the offshore industry but is not limited to them. Besides the ice failure mechanisms involved in the process of ice interaction with the MCS models, the parameters analyzed include neck size, structural orientation, ridge width, and the events that caused the maximum ridge loads. In the analysis of the ice failure mechanisms, three ridge failure patterns are identified. Both ridge cracking and ridge segment ride up processes are recognized to be events causing the maximum ridge loads. The influence of a number of factors on ice cracking pattern and ice loads exerted on the MCSs are considered in the data analysis.; To provide an insight into the interaction process and the ice failure mechanisms, a series of numerical simulations are carried out using a commercial discrete element code (DECICE). DECICE is capable of realistically simulating the ice breaking processes accompanied by broken ice pieces riding up on the structural surface. This overcomes the disadvantage of the conventional finite element analysis in which the ride-up forces are to be approximately computed under an unrealistic assumption that only one layer of ice rides up. The simulations using DECICE show the broken ice pieces to be actively involved in the breaking process of impinging ice. The effect of neck size on ridge and sheet ice loads is also studied using DECICE.; An analytical model is developed which takes the particular feature of the MCSs and ridge length into account; this model should provide designers with a simple estimation of ridge cracking loads. (Abstract shortened by UMI.)...