Model Testing of Structures in Ice: Consideration of Scale Effects,
NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO)
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The question posed of confidence and scale factor effects of ice model tests is complex. Modelling of the structure is not always straightforward, but in most cases a good representation of the prototype structure can be built. The properties of refrigerated model ice all scale very well, especially if care is taken in choosing the scale factor based on the crushing strength of the ice. Results of structure testing in model ice would seem to give very good estimates of the forces to be encountered in the prototype situation for scale factors up to the least lambda 30. The answer to the question of the most appropriate scale factor for model tests is not clear-cut. Performing tests at high scale factors has the advantages that the structures are smaller and therefore easier to build and handle, the carriage and load cells can be more easily made comparatively rigid, and the freezing time for an ice sheet is relatively shortened. On the other hand, performing tests at low scale factors has the advantage that warm-up time is decreased, the energy similarity involved in breaking the ice in flexure is more accurately scaled, the tests tend to appear more realistic and the inaccuracies involved in scaling up model test results by the scale factor are decreased. The confidence with which model tests can be extrapolated to full scale very much depends on these scale factor effects.