ABSTRACT:

An upward breaking cone is a common shape proposed for arctic offshore structures. The conical shape will induce ice bending failure, and hence, reduce the horizontal ice forces on the structure. In order to save on fabrication costs, it may be desirable to approximate the smooth conical surface by a series of flat faces or facets. The present paper documents an experimental test program which studies the ice loading on a multifaceted conical structure. AI: 50 model scale of a six-sided or six-faceted cone is tested. The model is instrumented to measure separately the ice loads on different parts of the structure. The face ted cone is subjected to a range of ice conditions representing level ice sheets and ridges. The present paper describes the model construction, associated instrumentation, the experimental techniques and test conditions for the model test program. The test results are presented in tabular form. Comparison is made of the experimental results with the predictions of two theoretical models developed for computing the ice forces on smooth cones. The forces measured on the multifaceted cone show reasonable agreement with the Ralston (1980) theoretical model.

INTRODUCTION

A common shape proposed for arctic offshore exploration and production structures is that of an upward breaking cone (e.g., Wasilewski and Bruce, 1981; Della Greca, 1984). This type of structure is expected to be made of steel. The curved shape of the cone would make fabrication with steel very difficult and costly. Thus, for ease of fabrication and saving in construction costs, it would be desirable to approximate the smooth conical surface by a series of flat faces or facets. Hence it is necessary to investigate the effects of a multifaceted surface on the ice failure process and subsequently on the ice loading on the structure itself.

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