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在立管动力平衡系统的力学模型中考虑浮式平台的惯性作用和管-土相互作用,研究在不同参数激励下钢悬链线立管触地点动力响应。基于大挠度柔性索理论,分别采用具有弯曲刚度的大挠度细长梁、弹性地基梁模拟立管的悬垂段和流线段,考虑触地点处的大曲率,建立了立管的三维有限元模型,利用Galerkin方法对运动方程离散为一组非线性二阶常微分方程,运用Newmark-β法求解离散方程。通过在立管的动力方程中引入δ函数来体现浮式平台对立管的惯性和水动力影响,将悬链线立管与浮式平台作为一个整体进行动力分析,以工程中实际使用的1800m水深的钢悬链线立管为例,通过对立管顶部进行谐波激励,分别就水动力系数、管内流体密度和海床土体刚度对立管特征点动力分析的影响进行分析,研究表明:水动力系数的改变对立管触地点的动力响应的影响较为显著,主要体现在弯矩和张力幅值的增加;管内流体密度不同,触地点位置不同,表明立管在输送不同液体或气体可能发生疲劳破坏的位置也不同;而海床土刚度对立管触地点区域的弯曲应力影响较大,对轴向应力则影响不大,其结果对SCR设计具有重要的指导意义。
In the mechanical model of riser dynamic balance system, the inertial action of floating platform and tube-soil interaction are considered, and the dynamic response of riser contact point under different parameters is studied. Based on the theory of large deflection flexible cable, large-deflection slender beams with bending stiffness and elastic foundation beams are respectively used to simulate the overhanging section and streamline section of the riser. Considering the large curvature at the contact point, a three-dimensional finite element model , The Galerkin method was used to discrete the equations of motion into a set of nonlinear second-order ordinary differential equations. The Newmark-β method was used to solve the discrete equations. By introducing delta function into the dynamic equation of riser, the inertial and hydrodynamic effects of the riser on the floating platform are reflected. The dynamic analysis of catenary riser and floating platform as a whole is carried out. The water depth of 1800m Taking the steel catenary riser as an example, the influence of hydrodynamic coefficient, the fluid density in the tube and the stiffness of the sea floor on the dynamic analysis of the characteristic points of the riser were analyzed by harmonic excitation at the top of the riser. The results show that: The change of coefficient has more significant influence on the dynamic response of the contact point of the riser, which is mainly reflected in the increase of the bending moment and the amplitude of tension. The different density of fluid in the pipe and the location of the touchdown point indicate that the riser may experience fatigue failure when conveying different liquids or gases And the location of the soil is also different. However, the stiffness of the seabed soil has a great influence on the bending stress in the contact point area of the vertical tube and has little effect on the axial stress, and the result has an important guiding significance for the SCR design.