Estimates of ice loads and pressures on the Molikpaq structure during the 1986 deployment at the Amauligak I-65 location in the Beaufort Sea, have been based on Medof panels attached to the outer steel surface, strain gauges installed on the steel structure, extensometers measuring the deformation of the caisson, as well as inferences from the geotechnical design and performance of the structure. Geotechnical information and the extensometer readings suggest lower loads than those estimated from the Medof panels. Analysis of the decelerating floe interaction of May 12th also supports the lower loads. An extensive evaluation of the instrumentation on the Molikpaq was conducted. The extensometers and strain gauges have been calibrated to the Medof panel loads in the past. The behaviour of the polyurethane material used as part of the construction of the Medof panels was researched. Ice crushing involves highly localized pressures and will apply loadings akin to "panel beating" with repeated and randomly placed high-pressure zones across the face of the panel. It was found that the stress and strain, under plausible conditions for the Medof panels, reached levels that would result in softening associated with the nonlinearities and the Mullins effect. It is concluded that the extensometers provide the best load estimates, albeit with some uncertainty associated with the boundary conditions applied to the structure. It is a reasonable conclusion that the Medof panel calibrations changed with time, with a softening process, indicating higher loads than actually occurred. Design pressures based on the Medof panels for the 1985-86 deployment, likely overestimate the loads by about 50%. The geotechnical and other estimates fall into the same "ballpark".
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