海管悬跨段涡激振动疲劳寿命评估方法

Fatigue life assessment method for free span subsea pipeline under vortex induced vibration

涡激振动是导致海底输油管道悬跨段疲劳失效的主要原因,文中根据实际工程需要,提出了一套ABAQUS有限元分析方法,采用一条二维特征线和Pipe31H梁单元来模拟整条多跨段管线模型并赋予其截面属性。将求解过程分为静态阶段和动态阶段,分别采用"接触模式"和"弹簧模式"来模拟管道与海床表面的相互作用状态。结合仿真结果与各项疲劳评估准则计算疲劳寿命。此外,为了得到绝对安全的设计结果,针对混凝土层退化、检测数据精度和泥土刚度等添加相应的安全系数。最后给出了一个交互悬跨段的疲劳评估算例分析。

Vortex induced vibration is the main reason accounts for fatigue failure of subsea free span pipeline. In this paper, a ABAQUS finite element analysis method has been put forward. The new method uses a characteristic curve and Pipe31H beam element to replace the real model of multi-span pipeline with relevant section property. The solving procedure is divided into static and dynamic phase, modeling the surface interaction condition between pipeline and seabed under‘contact model＇ and ‘spring model＇ respectively. The fatigue life is calculated by combining the simulation results and fatigue criterion. In addition, in order to captured the comparatively safety results, certain sensitivity studies for concrete degradation, survey accuracy, and soil stiffness are also be considered for adding the relevant safety factors. In the end, an example of fatigue evaluation for an interacting free span is provided.