The Earthquake Engineering Online Archive

Dynamic interactions between floating ice and offshore structures

Croteau, Paul

UCB/EERC-83/06, Earthquake Engineering Research Center, University of California, Berkeley, 1983-05, 335 pages (640/C76/1983)

The author examines a case in which ice fails due to crushing at the face of the structure. A formulation suitable for investigating the dynamic response of platform systems, including floating ice sheets or ice features, is developed and applied, based on Korzhavin's crushing formula. A unidirectional finite element for modeling dynamic ice-structure interactions is developed. This "ice" element is incorporated into a general nonlinear dynamic analysis formulation which is applied to three types of problems: the impact of large ice floes against fixed platforms, the response of slender structures subjected to continuous crushing by a uniform ice sheet, and the earthquake response of an offshore structure in the presence of floating ice. In the case of continuous crushing, the model is shown to be effective in describing the large-amplitude ice force variations observed during sustained slow velocity crushing against slender structures. The versatility of the finite element formulation is demonstrated by an application to a multi-legged Condeep type platform. Analysis of the earthquake response of the same Condeep gravity structure in 150 m of water, subjected to severe ground motion, with and without an ice cover at the surface of the sea, shows the ice to have a favorable effect.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-83-06.pdf (25 MB)