冰激直立腿海洋平台疲劳寿命分析

Fatigue life analysis of the vertical leg jacket platform induced by ice vibrations

由于渤海特殊环境条件与油藏分布决定了该海域导管架油气平台属于典型的柔性抗冰结构。多年现场观测发现,该类结构存在显著的冰激振动现象。冰振不仅能激起较大的甲板加速度响应,还会引起明显的导管架管节点交变应力。在结构设计与安全保障中进行疲劳分析及寿命估计是必要的。对于直立腿抗冰结构,精确的冰激疲劳寿命计算方法还不成熟。基于多年的现场监测,首先分析了冰与直立腿抗冰结构相互作用过程;其次,提出了冰激直立腿平台的疲劳寿命分析流程;最后,选取渤海某典型直立腿平台,利用ANSYS数值模拟,对比了稳态冰力和随机冰力下结构的疲劳损伤,进而计算出疲劳寿命。本研究为寒区柔性结构抗冰设计与安全保障提供了理论基础。

Because of the specific environmental condition and the oil reservoir,the jacket platforms in Bohai Sea are usually designed as compliant ice-resistant structures. Significant ice induced vibration has been found in the long term full-scale measurements. The vibration has caused large magnitude deck accelerations and significant cyclical stress of tubular joints. To ensure the safety of the structure,fatigue life induced by ice vibrations should be estimated in the design of the structure. Nowadays,the methodology for ice-induced fatigue life analysis is still not available for the vertical structures. Based on the field observation for many years,a fatigue life evaluation method is presented in this paper. A case study for a typical vertical-leg jacket platform in Bohai Bay is presented in ANSYS. Fatigue damages of the structure induced by steady state ice force and random ice force are evaluated and compared with each other. Then the fatigue life is calculated from the total damage. This research is helpful for ice-resistant design and safety assurance for the ice-resistant structures in ice zone.