海底管道受坠物撞击时的弹塑性有限元分析

ELASTIC-PLASTIC FINITE ELEMENT ANALYSIS OF SUBMARINE PIPELINE IMPACTED BY DROPPED OBJECTS

采用非线性动态有限元法模拟了坠物撞击海底管道的过程。以Ramberg-Osgood模型模拟海床,同时考虑混凝土涂层拉、压不同的非线性特性,并利用罚函数法处理坠物、海床与管道之间的相互作用。分析了物体形状、撞击角度、摩擦、内压、混凝土厚度、埋深及悬空长度对管道撞击塑性变形的影响。结果表明:坠物以尖端撞击管道时,凹痕深度较大,但凹痕范围相对较小;90°撞击时对管道的塑性变形影响最大,摩擦系数影响较小;内压增加了管道的应力,但减小了凹痕深度;混凝土层对重量较大坠物的防护作用较弱;埋深超过1m能有效防止管道受撞击破坏;悬跨减小了管道凹痕深度,但使管道更容易产生整体破坏。与现行规范计算结果相比,该文方法更加符合实际。

The process of a submarine pipeline impacted by dropped objects is simulated by using a nonlinear dynamic finite element method.The Ramberg-Osgood model is adopted to model the seabed and the different tensile and compressive nonlinear characteristics of concrete coating are considered at the same time.The interactions between the dropped object and seabed and pipeline are solved with the penalty function method.The influence of various factors on the plastic impact deformations of the pipeline are analyzed,including the object shape,impact angle,friction,internal pressure,concrete thickness,burial depth and free spanning of the pipeline.The results show that： the dropped object impacting the pipeline with a tip makes a larger dent depth,but a relatively small deformation range;the maximum dent depth of the pipeline occurs at an impact angle of 90° and friction makes little influence on the impact;the internal pressure increases the stress of the pipeline,but decreases the dent depth;concrete coating has a weak protective effect when the weights of dropped objects are larger;the pipeline can be effectively protected,when the buried depth was more than one meter;the free spanning decreases the dent depth of the pipeline but makes the integral damage of the pipeline more easily.The method in the paper is more suitable to the actual situation,comparing with the results obtained by the current codes.