This study considers a new method for the ice load consideration based on the ice load spectrum in the time domain. Recently, the interest on the Arctic offshore structures for exploring and exploitation of the Arctic region has been increased by the decreasing trend of sea ice covered area. The ice load consideration in the design of the Arctic offshore structures is essential. In the design and evaluation of the station-keeping system of the Arctic offshore structures, the consideration of the ice load acting on the offshore structures is one of the main vital components. There are several methods to consider the ice load in the time domain analysis. However, these numerical approaches require a significant amount of computation because the number of ice floes to be considered in the calculation is too big. In this study, a new approach to consider the ice load acting on the Arctic offshore structure is suggested. The proposed ice load calculation method in time domain is based on the ice load spectrum concept. From the experimental results, it is expected that the global ice load will have mean components and oscillatory components in the frequency domain. Thus, if the mean components and oscillatory components of the ice load by the angle of attack of the ice drifting with ice parameters are given, then the ice load acting on the offshore structure can be reconstructed. The feasibility of the proposed ice load consideration method is examined with experimentally gained data and numerically calculated data.
The coverage of the sea ice on the Arctic Ocean has been reduced for the last several decades. The trend of the sea ice decreasing is now commonly accepted as the effect of the global climate change which is regarded as one of the threats to humankind. In other hands, better accessibility to the deep Arctic Ocean will be opening as the sea ice reducing trend keeps its pace. Moreover, it had been established that the oil and gas deposits in the Arctic area are reaching up to 22% of the world's oil and gas deposit (Hearing, 2009). In line with these circumstances, developments of the Arctic offshore technology for exploring and exploitation of the Arctic region are being conducted in many countries.
In the development of the Arctic offshore technology, the development of station-keeping methodologies in Arctic condition is the essential and crucial component (see Fig.1). For floating offshore structures in general, the mooring system and dynamic positioning (DP) system are considered as the method for station-keeping. In the design of the mooring system and the DP system, the time domain analysis is frequently conducted to examine the performance and security of the station-keeping system. Consequently, the consideration of ice loads in the time domain becomes one of the essential components in the design of the station-keeping methodology for the Arctic condition.
