Behavior of Unbonded Flexible Risers Subject to Axial Tension

• Published in: China ocean engineering Vol. 28; no. 2; pp. 249 - 258
• Main Author: 任少飞 唐文勇 郭晋挺
• Format: Journal Article
• Language: English
• Published: Heidelberg Chinese Ocean Engineering Society 01-04-2014
• Subjects: ABAQUS; Axial stress; Coastal Sciences; Computer simulation; Engineering; Finite element method; Fluid- and Aerodynamics; Marine; Marine & Freshwater Sciences; Mathematical analysis; Mathematical models; Numerical analysis; Numerical and Computational Physics; Oceanography; Offshore Engineering; Risers; Simulation; Stiffness; 拉伸行为; 无粘结; 有限元模型; 柔性; 正交各向异性材料; 立管; 轴向刚度; unbonded flexible risers; quasi-static; friction; contact; axis stiffness
• ISSN: 0890-5487; 2191-8945
• DOI: 10.1007/s13344-014-0020-9

Owing to nonlinear contact problems with slip and friction, a lot of limiting assumptions are made when developing analytical models to simulate the behavior of an unbonded flexible riser. Meanwhile, in order to avoid convergence problems and excessive calculating time associated with running the detailed finite element （FE） model of an unbonded flexible riser, interlocked carcass and zeta layers with complicated cross section shapes are replaced by simple geometrical shapes （e.g. hollow cylindrical shell） with equivalent orthotropic materials. But the simplified model does not imply the stresses equivalence of these two layers. To solve these problems, based on ABAQUS/Explicit, a numerical method that is suitable for the detailed FE model is proposed. In consideration of interaction among all component layers, the axial stiffness of an eight-layer unbonded flexible riser subjected to axial tension is predicted. Compared with analytical and experimental results, it is shown that the proposed numerical method not only has high accuracy but also can substantially reduce the calculating time. In addition, the impact of the lay angle of helical tendons on axial stiffness is discussed.