Abstract. Sea ice disasters seriously threaten the safety of oil platforms in the Bohai Sea. Therefore, it is necessary to carry out the risk assessment of sea ice disasters on oil platforms in the Bohai Sea. In the study, the risk assessment of sea ice disasters on fixed jacket platforms in the Liaodong Bay was performed. Firstly, the formation mechanisms of sea ice disasters were analyzed and the sources and modes of sea ice risks were clarified. Secondly, according to the calculation formulas of extreme ice force, dynamic ice force and accumulated force, several ice indices such as thickness, motion, strength, period, and concentration were proposed as the hazard indices and corresponding values were assigned to the proposed indices based on ice conditions in the Bohai Sea. Thirdly, based on four structural failure modes (structures overturned by the extreme ice force (Mode 1), structural fracture failure caused by dynamic ice force (Mode 2), facility damage caused by the dynamic ice force (Mode 3), and structural function failure caused by accumulated ice (Mode 4)), the structural vulnerability index, overturning index, dynamic index, ice-induced vibration index, and function index were proposed and corresponding values were assigned to the structural vulnerability index of fixed jacket platforms in the Liaodong Bay. Fourthly, the weight of each risk index was determined according to previous sea ice disasters and accidents and the sea ice risk was calculated with the weighted synthetic index method. Finally, with the above index system and risk assessment methods, the risk assessment of sea ice disasters on 10 jacket platforms in three sea areas in the Liaodong Bay was carried out. The analysis results showed that efficient sea ice prevention strategies could largely mitigate the sea ice-induced vibration-related risks of jacket platforms in the Liaodong Bay. If steady-state vibration occurred (usually in front of the vertical legged structure) or the structural fundamental frequency was high, the structural vulnerability was significantly increased and the calculated risk levels were high. The sea ice risk assessment method can be applied in the design, operation, and management of other engineering structures in sea ice areas.
Spatio-temporal characteristics of the sea-ice volume of the Bohai Sea, China, in winter 2009/10