Risk assessment of sea ice disasters on fixed jacket platforms in Liaodong Bay

摘要

Sea ice disasters seriously threaten the structural safety of oilplatforms in the Bohai Sea. Therefore, it is necessary to carry outa risk assessment of sea ice disasters on oil platforms in theBohai Sea. In this study, a?risk assessment of sea ice disasters onfixed jacket platforms in Liaodong Bay, in the Bohai Sea, was performedin five steps. Firstly, the formation mechanisms of sea icedisasters were analyzed and the sources and modes of sea ice riskswere summarized. Secondly, according to the calculation formulas ofextreme ice force, dynamic ice force, and accumulated force, severalice indices such as thickness, motion, strength, period, andconcentration were proposed as the hazard indices, and correspondingvalues were then assigned to the proposed indices based on iceconditions in the Bohai Sea. Thirdly, based on four structuralfailure modes – structural overturning by extreme ice force (Mode?1),structural fracture failure caused by dynamic ice force (Mode?2),the damage of facilities caused by dynamic ice force (Mode?3), andstructural function failure caused by accumulated ice (Mode?4) – thestructural vulnerability index, overturning index, dynamic index,ice-induced vibration index, and function index were proposed, andcorresponding values were assigned to the structural vulnerabilityindex of fixed jacket platforms in Liaodong Bay. Fourthly, theweight of each risk index was determined according to previouslyrecorded sea ice disasters and accidents, and the sea ice risk wasthen calculated with the weighted synthetic index method. Finally,with the above index system and risk assessment methods, the riskassessment of sea ice disasters on 10?jacket platforms in three seaareas in Liaodong Bay was carried out. The analysis resultsshowed that efficient sea ice prevention strategies could largelymitigate the sea ice-induced vibration-related risks of jacketplatforms in Liaodong Bay. If steady-state vibration occurs(usually in front of the vertical legged structure) or thestructural fundamental frequency is high, the structuralvulnerability is significantly increased and the calculated risklevels are high. The sea ice risk assessment method can be appliedin the design, operation, and management of other engineeringstructures in sea ice areas.