Coupled element modeling scheme for the global dynamic analysis of unbonded flexible risers

A coupled element modeling method is proposed for global dynamic analyses of unbonded flexible risers. Owing to the multi-layer structure of unbonded flexible risers, the global-dynamic-analysis method applied to the steel rigid risers is insufficient for flexible risers. The main challenges lie in the enormous difference between the anti-tension and anti-binding capacity of unbonded flexible risers which results in serious ill-conditional calculation in global dynamic analysis. In order to solve this problem, the coupled element modeling approach was proposed in this study. A time domain fatigue analysis was applied to illustrate the necessity of the proposed approach. A dynamic benchmark case is used to demonstrate the accuracy of the coupled element method respectively. Subsequently the validated coupling element method is employed to conduct the global dynamic analyses for a free hanging flexible riser. The results demonstrate that the proposed approach can give the accurate global dynamic response under the guidance of the fatigue failure mode for unbonded flexible riser. The parametric influence analyses also provide a practical and effective way for predicting the global dynamic response. © 2015, Shanghai Jiaotong University and Springer-Verlag Berlin Heidelberg.