ABSTRACT:

Strength properties of ice fields in marine areas have high variability in space and time. That's why there appears an uncertainty in ice load analysis which may cause poor accuracy. Hence, it's necessary to consider parameters of both ice-structure interaction and ice structure inhomogeneity when assuming calculated ice strength. In the paper we show that it is necessary to take into consideration ice cover spatial inhomogeneity. A program of experimental investigation of ice cover spatial inhomogeneity is presented that allows taking this issue into account when considering ice strength distribution. Analysis of results is also presented.

INTRODUCTION

Ice loads on off-shore structures in the northern seas are often predominant and, as a rule, they affect main parameters of such structures. Oil and gas extracting platforms are very expensive and they need numerous maintenance staff. Failure of the structure may cause ecologic calamity and even human victims. Hence it's obvious how it is important to make proper distribution of ice loads calculated values. Ice loads on off-shore structures depend on numerous factors, such as geometric size of ice structures, ice structure, drift speed, ice weight, strength parameters of ice structures, combinations of various ice effects, weight of adjoining water, size of the off-shore structure, etc. Strength of sea ice varies in space and it varies with time. That's why proper estimation of ice strength is very important for more accurate analysis of ice loads. From this point of view the most effective way is to divide perennial process of ice-structure interaction into two processes made in different time scales, such as long-term and short-term periods (Bekker, 1990). Perennial field observations and defining of probable distribution of ice cover main parameters will allow explaining ice properties variations in space and time all-over the process of designed structure exploitation (long-term period).

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