Enhanced Multi-Layer Fatigue-Analysis Approach for Unbonded Flexible Risers

• Published in: China ocean engineering Vol. 28; no. 3; pp. 363 - 379
• Main Author: 杨和振 姜豪 杨启
• Format: Journal Article
• Language: English
• Published: Heidelberg Chinese Ocean Engineering Society 01.06.2014
• Subjects: China; Coastal Sciences; Design engineering; Engineering; Fatigue life; Fluid- and Aerodynamics; Marine; Marine & Freshwater Sciences; Mathematical models; Multilayers; Numerical and Computational Physics; Ocean engineering; Oceanography; Offshore Engineering; Risers; Simulation; Touchdown; 增强层; 复杂结构; 数值模型; 无粘结; 柔性管; 疲劳分析; 疲劳寿命; 立管; fatigue; dynamic analysis; finite element method; unbonded flexible riser
• ISSN: 0890-5487; 2191-8945
• DOI: 10.1007/s13344-014-0029-0

This paper proposes an enhanced approach for evaluating the fatigue life of each metallic layer of unbonded flexible risers. Owing to the complex structure of unbonded flexible risers and the nonlinearity of the system, particularly in the critical touchdown zone, the traditional method is insufficient for accurately evaluating the fatigue life of these risers. The main challenge lies in the transposition from global to local analyses, which is a key stage for the fatigue analysis of flexible pipes owing to their complex structure. The new enhanced approach derives a multi-layer stress-decomposition method to meet this challenge. In this study, a numerical model validated experimentally is used to demonstrate the accuracy of the stress-decomposition method. And a numerical case is studied to validate the proposed approach. The results demonstrate that the multi-layer stress-decomposition method is accurate, and the fatigue lives of the metallic layers predicted by the enhanced multi-layer analysis approach are rational. The proposed fatigue-analysis approach provides a practical and reasonable method for predicting fatigue life in the design of unbonded flexible risers.