深海系缆动张力的超谐动力响应

文章考虑深水系缆的拉伸和弯曲变形,取正交坐标和切向量描述任意结点的6个广义位移,考虑缆变形的几何非线性和水动力影响,基于细长杆理论推导缆索的单元刚度矩阵,引入单元内张力一致假设,推导出12×12的非线性刚度矩阵,并与有限元软件对接。针对1800m水深平台的系缆,考虑系缆端点垂荡运动,以及端点垂荡、横荡和海流作用两种状态下系泊系统的动力响应。计算结果表明,端点运动和海流作用,引起系缆系统的二倍超谐动力响应,并且随着流速增大,系缆超谐动力响应增大,系缆的超谐动张力分量对于缆索疲劳累积损伤具有重要影响,在系缆疲劳分析时应该予以考虑。

Analysis of dynamic tension nonlinear characteristics for mooring system in the deep water

By considering the extension and bending deformation of cable in the deep sea,the 6 generalized displacements of the nodes are described by rectangular coordinate and their tangent vector.The hypothesis that tension in the element will not be changed is adopted.The 12×12 nonlinear stiffness matrix is obtained based on the rod theory considering the geometric nonlinearity and the effect of water dynamic and the element can be called by general finite element software.The dynamic responses of mooring system under heave motion at the end of cable are calculated and the dynamic response under heave,sway and fluid-drag force is calculated,too.The results show that 2-times super-harmonic response of mooring system is caused by the motion of upper point and the effect of fluid,and with the increase of fluid velocity,the super-harmonic response of the system increases.The super-harmonic response component has significant influence on fatigue cumulative damage of cable,and should be considered in the fatigue analysis.