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Summary of Working Paper No. 114-1998

I.1.7 Large Scale Hull Loading of First-year Sea Ice

By R. Gagnon, R. Frederking, S. Jones, National Research Council of Canada; St. Johns, Canada; P. Spencer, D. Masterson, Sandwell Engineering Inc., Canada

For Phase 2 of INSROP Project I.1.7, Large Scale Hull Loading of First-Year Sea Ice, a series of tests in first-year brackish sea ice were carried out in Tuktoyaktut in the Canadian Arctic to simulate ice loading on a ship hull. Loading was generated by hydraulic actuators impressing a rigid indentor against an ice edge.

A finite element analysis of the test geometry was carried out to assess the deformation and stress distribution in the ice edge for cases with both undamaged and varying degrees of damage. The calculated and measured stiffness of the ice edge agreed for a realistic selection of elastic modulus of the parent ice and damaged ice. The field results showed that, for higher loading rates, damaging the ice reduced the failure stress from 5.5 MPa to an average of 3.5 MPa, however this result was not conclusive.

Review of these results and those of other field tests, including our Phase 1 tests (see Working Paper No. 7), showed that the nature of the ice loading, depending on whether it was uniform pressure or uniform deformation, significantly affected the results. Failure stress for uniform pressure tests did not have any dependence on area or aspect ratio. The measured field results gave average ice pressures less than those recommended by the Arctic Pollution Prevention Regulations. Crack formation and movement were studied using high speed video, and the velocity of the cracks was found to be of the order of 10 m/s.