Dynamic analysis of steel catenary riser on the nonlinear seabed using vector form intrinsic finite element method

Abstract

The dynamics of a steel catenary riser (SCR) are highly nonlinear and strongly affected by the interaction between riser and seabed. Possessing the advantages of robustness and high efficiency, the vector form intrinsic finite element (VFIFE) method is applied to solve this problem. The nonlinear hysteretic riser-seabed interaction is integrated into the model. Simulation results are compared to the commercial software Ocraflex, and high similarities prove the capability of VFIFE to simulate the dynamics of SCR on the nonlinear seabed. In dynamic analysis, a larger mass damping coefficient should be applied in the touchdown zone (TDZ) and flowline part to increase the stabilization. In contrast, the coefficient in the catenary part has only minor influences on the behavior of SCR. To improve the computation efficiency, the effect of using coarse meshes with different densities in the catenary part has been investigated, while the fine meshes are applied in the TDZ and flowline part. In the dynamic analysis of TDZ, the distribution of seabed reaction force and stress range are present and discussed. Furthermore, the effects of different loading parameters and hanging-off positions on the trench profiles and fatigue damage of SCR have been studied in detail.