非线性管土作用下钢悬链式立管动力响应分析

The Influence of Nonlinear Riser-Soil Interaction on the Dynamic Response of Steel Catenary Riser

钢悬链线立管(SCR)在上部浮体运动和波流荷载激励下会与海床土相互作用,传统的线性海床模型假定荷载位移关系是线性的,没有考虑管土相互作用的非线性过程和海床土吸力的影响,本文基于大挠度柔性索理论的钢悬链式立管动力分析程序CABLE3D,将立管受到线性海床的弹性支撑力扩充为立管受到的海床垂向力,充分考虑管土非线性相互作用,并考虑海床土吸力对钢悬链式立管触地点区域的影响,开发出新的动力分析程序。程序采用非线性有限元方法对控制方程进行离散,时域内采用Newmark-β法,求解给定上部浮体运动条件下,SCR的动力响应,通过算例对线性刚度海床和非线性刚度海床进行对比,并分析了不同海床刚度对SCR触地点动力响应和疲劳损伤的影响。结果表明:非线性海床刚度模型比线性海床刚度模型更接近真实的管土作用过程;在非线性海床刚度模型下,海床土刚度越大,SCR触地点区域垂向位移响应越小,应力幅值越大,疲劳损伤越严重。

The Steel Catenary Riser（SCR）will interact with seabed under wave load and upper platform motion.Traditional linear riser-soil interaction model suppose that the relationship of seabed support load and displacement is linear,and not consider the influence of soil suction.The paper based on the Steel Catenary Riser dynamic analysis program-CABLE3 Dextending the linear elastic support on the seabed to nolinear riser-soil interaction with considering the influence of soil suction on SCR in the Touchdown Zone.The sag bend and the flowline segment of SCR is simulated with a slender beam model and an elastic foundation beam model with the assumption of a large deformation.Control equations is discreted by nonlinear finite element method,and Newmar-βmethod is used in the time domain numerical integration.The dynamic response of SCR is sovled by giving specific upper platform motion.By comparison of linear seabed stiffness model and nonlinear seabed stiffness model,and the influence of different seabed stiffness on dynamic responce and fatigue damage of SCR at TDZ.The result shows that nonlinear seabed stiffness model is more approximate riser-soil interaction process than linear seabed stiffness model.Under nonlinear seabed stiffness model,with the increasing of seabed stiffness,the vertical displacement response of SCR at TDZ will decrease,and the stress amplitude and fatigue damage will increase correspondingly.