Three-dimensional non-linear finite element model for the Molikpaq, Gulf's mobile caisson

The paper describes the development and testing of a comprehensive finite element model of a mobile arctic caisson which has been used for offshore drilling in the Canadian Arctic, and which has been exposed to significant dynamic ice forces. The specific structure, the Molikpaq, is owned by Gulf Canada. The structure consists of an eight-sided annular steel caisson, whose overall width is 110 m. The caisson is set down on a berm such that the effective water depth is approximately 19 m. The central core is then filled with sand to provide the overall stability and to increase the resistance to lateral loads. The system is designed for year-round drilling, and therefore must be capable of resisting loads from impacts from thick multi-year ice flees. The model described in this paper consists of a finite element representation of the caisson which is developed using macro-elements to model the complex structural steel arrangement of bulkheads and stiffened steel plates in the caisson. These macro-elements are then combined with a brick element representation of the core, and various alternative models for the berm. The static and dynamic behaviour of the model are tested, and the results compared to the behaviour of the prototype. Copyright (C) 1996 Elsevier Science Ltd.