Author(s): R. Gagnon
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Abstract: Ice load and pressure data from the 1994 CCGS Louis St-Laurent trip through the Arctic were reanalyzed using a different method than was used for the original report. The impact events that were chosen for re-analysis spanned a variety of ship speeds, ice thicknesses and concentrations. For any given impact event all sub-panel segments (cells) of the strain-gauged hull panel for which a signal registered above the deemed noise level were considered to be subjected to ice load. Consequently all of the ice contact area, and associated ice load, was taken into account regardless of whether the ice contact consisted of a single area or multiple non-contiguous areason the impacted panel. The data from a total of 51 randomly selected events covering a range of ice contact areas from 1.4 m to 16.8 m were initially analyzed to yield load and pressuredistribution at the time of peak load for each event. Then further analysis was conducted to identify well-behaved events where the loaded areas were more contained on the panel and less concentrated at its edges. The effects of using this selection strategy are shown. For the data from the well-behaved events the pressure-area relationship was essentially flat with an average value 0.49 MPa over the stated range of contact area. Another set of 12 impact events were also analyzed, for which the full time-series of pressure on each of the 30 cells that comprise the panel were available from the original reduction of data. An analysis of load and contact area from these events demonstrated the effect of having oversized cells on ice impact panels, that leads to overestimates of ice contact area and underestimates of average pressure. The analysis suggested that the best estimates of actual ice contact area and average pressure, though still not fully accurate, are obtained when the contact area is the greatest, i. e. usually at peak load.
Year: 2014