The application of centrifugal modeling to determine ice forces on isolated circular structures

ABSTRACT: A test system was developed and used to investigate ice/structure interaction with centrifugal modeling. The test system was designed to perform two main functions: (1) create a uniform ice sheet, and (2) drive a model structure through the ice sheet at a constant speed. Both of these functions were … See more

ABSTRACT: A test system was developed and used to investigate ice/structure interaction with centrifugal modeling. The test system was designed to perform two main functions: (1) create a uniform ice sheet, and (2) drive a model structure through the ice sheet at a constant speed. Both of these functions were required to be carried out while onboard a centrifuge. The ice sheets were created by applying vaporized liquid nitrogen to the water surface in a model test container. Freezing test results were used to establish a linear relationship between ice thickness and the square root of the product of time and temperature. The relationship was used to create ice sheets of predetermined thickness. An electric motor mounted in the model test container was able to withstand the large inertial stresses associated with accelerations up to 100 gravities. The motor drove the model structure through the ice sheet at a constant velocity. Two small-scale model test programs were conducted to determine ice forces on offshore structures and the usefulness of the centrifugal modeling technique to investigate ice/structure interaction problems. The first program was designed to investigate ice crushing forces against isolated vertical cylindrical piles. The model pile test results show good agreement with the results of other research programs. The second test program was designed to investigate ice bending forces against frictionless rigid conical structures. The test results indicate that centrifugal modeling may provide a means for scaling ice density for small-scale model tests. Further, a comparison of the test results with the results of a theoretical analysis using plasticity theory shows good agreement.

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