ABSTRACT

Local pressure data from bergy bit impacts with the CCGS Terry Fox off the north east coast of Newfoundland in June 2001 have been compared with other data. These data sources include the USCGC Polar Sea from operations in the Beaufort Sea and Chukchi Sea, and bergy bit impacts at Grappling Island. They have been put on a common basis and compared with the CCGS Terry Fox data. When factors relating to area, exposure and probability of exceedance are taken into account, the difference between the three groups of local pressure data becomes smaller. At the 10-3 probability of exceedance and a single sub-panel of area about 0.3 m2, the local pressure varied from 5 MPa (CCGS Terry Fox), in the range 4.2 MPa to 2.7 MPa (USCGC Polar Sea), to 1.7 MPa (Grappling Island). Smaller ice mass and lower impact velocities explain the lower pressures for Grappling Island data.

INTRODUCTION

Local ice pressures that could be generated on ships impacting bergy bits are of concern for navigation in the ice affected waters of the Grand Banks. A field test program carried out with the CCGS Terry Fox off the north east coast of Newfoundland in the latter part of June 2001 (Gagnon et al., 2008) produced over 100 impact events on glacial ice from which local pressures and pressure distributions were obtained (Frederking and Johnston, 2005, Ritch, et. al., 2008) These data are the most directly applicable data in relation to ice impact loads and pressures on the shuttle tankers operating on the Grand Banks. The purpose of this paper is to compare the CCGS Terry Fox local ice pressure results with other data, and thereby extend the applicability of the data. The focus is on the relative pressures on a given area, rather than on the pressure-area relation.

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