Steel/Concrete Composite Ice Walls for Arctic Offshore Structures

Abstract

The oil and gas industry is considering deploying large gravity-based structures (GBS) into the high Arctic seas for yearround production where they will be exposed to multiyear ice loads. Conceptual studies of such structures suggest that the design for the ice load and the low draft requirement during deployment to the Arctic become key design aspects, focusing the attention on efficient force-resisting strategies and ice wall design. An appropriately designed ice wall in combination with a well-thought-out ice resistance strategy can significantly reduce the cost and construction/installation schedule of a GBS. Ice walls made of steel/concrete/steel composite have the potential to provide significant robustness at a lower weight than typical all-concrete ice walls. Composite ice walls also provide the potential of more robust behavior than all-steel ice wall concepts. Composite walls, thus, promise great value as ice walls for Arctic structures. To validate the behavior of composite ice walls, a testing program was conducted that applied high-intensity loads to beam specimens 1.8 meters long and 0.3 meter thick with varying degrees of plate stiffening and concrete confinement. Strength, stiffness, ductility, load paths, and failure mechanisms were evaluated. Test variables included temperature, concrete density and strength, load paths, and type of composite load-carrying system. This paper demonstrates the viability of composite ice walls. It presents the results of the testing program, discusses the proposed ice wall configuration and appropriate design procedures, and proposes the steps that have to be taken to allow low risk application of composite ice walls for design and construction of an actual GBS.