The drifting ridges or ridge rows, as well as the large rare level ice sheets are the greatest hazard for offshore platforms. The factors influencing forming of extreme ice loads, are characterised by a high variability, therefore the purpose of this paper is to identify the probabilistic characteristics of extreme ice loads for the structure lifetime.
Reliability and durability of the chosen types of offshore structures depend on completeness and accuracy of extreme ice loads techniques recommended by design codes. Drifting ridges or ridge rows, as well as the large rare level ice fields are the greatest hazard for offshore platforms. The consideration of extreme ice features is one of the most complex tasks for the design of ice-resistant platforms. The factors influencing forming of extreme ice loads are characterised by a high variability and have a random nature. The purpose of this paper is to identity the probabilistic characteristics of extreme ice loads on ice-resistant platforms. The authors have amplified the determined model of drifting ice features acting the ice-resistant platforms. There has been developed a probabilistic model of extreme ice loads formation on offshore structure. The algorithm and the program of numerical modulating of the ice regime parameters taking into account the collision probability of drifting ridges and large rare ice fields with a structure are also presented. They are used to identify a distribution function of extreme ice loads.
The comparative analysis of the known models of the ice ridge acting on structures (Bekker et al. 1997; Frederking et al. 1999) shows, that all these models are mainly based on the hypothesis of the full ridge failure. However, in reality the full ridge failure can probably occur only in exceptional cases.
