摘要
顶部张紧式立管(TTR)作为海洋油气生产的关键装备,其环焊缝在复杂波浪载荷作用下易发生疲劳损伤,现有的疲劳可靠性分析方法存在模态关联不足、S-N曲线选型困难等问题。提出了一种适用于波浪谱激励的TTR环焊缝多轴频域疲劳可靠性分析模型,能有效解决传统方法的局限性。该方法首先基于Pierson-Moskowitz谱建立线性化的波浪力谱,进而结合模态动力学分析实现立管环焊缝的结构应力功率谱的构建;随后,结合PDMR多轴疲劳准则及主S-N曲线构建了立管环焊缝的疲劳极限状态函数,并分别采用一次二阶矩法(FOSM)和蒙特卡洛法(MCS)对模型精度进行验证;最后,分析并计算了多海况下立管环焊缝的疲劳可靠度指标及失效概率。研究结果表明:立管前10阶模态为响应主导模态,第4、6、8阶模态响应最显著,多模态叠加会加剧疲劳损伤;距离顶部16 m处焊缝的疲劳可靠度指标最小(1.72),失效概率为0.043,水下井口连接位置焊缝可靠度指标为2.17,失效概率0.0151。基于等效结构应力和主S-N曲线的极限状态函数形式简洁,模型精度满足工程要求。研究成果为海洋结构物焊缝疲劳可靠性分析提供了新方法,对提升TTR设计安全性具有重要工程价值。
Top-tensioned risers(TTR),as key equipment in offshore oil and gas production,are prone to fatigue damage at their girth welds under complex wave loading.However,existing fatigue reliability analysis methods often suffer from insufficient modal correlation and difficulties in selecting appropriate S-N curves.To address these issues,a multiaxial frequency-domain fatigue reliability model for TTR girth welds suitable for wave spectrum excitation was proposed,aiming to overcome the limitations of traditional approaches.The proposed method first established a linearized wave force spectrum based on the Pierson-Moskowitz spectrum,and it employed modal dynamics analysis to construct the structural stress power spectrum at the TTR girth welds.Subsequently,a fatigue limit state function was formulated using the PDMR multiaxial fatigue criterion and the master S-N curve.The model accuracy was verified using both the first-order second moment(FOSM)method and the Monte Carlo simulation(MCS).Finally,fatigue reliability index and failure probabilities of the TTR girth welds under multiple sea states were calculated.The results indicate that the modes of the first 10 orders dominate the riser response,with the 4th,6th,and 8th modes showing the most significant contributions.Furthermore,the superposition of multiple modes further exacerbates fatigue damage.The girth weld located 16 meters below the top exhibits the lowest fatigue reliability index(1.72)and the highest failure probability(0.043),while the weld at the subsea wellhead connection has a reliability index of 2.17 and a failure probability of 0.0151.The limit state function,based on equivalent structural stress and the master S-N curve,is concise in form and satisfies engineering accuracy requirements.This study provides a novel method for fatigue reliability analysis of offshore structural welds and offers valuable insights for improving the safety and design of TTR systems.
作者
贾鲁生
张龙
付丽宁
赵天奉
JIA Lusheng;ZHANG Long;FU Lining;ZHAO Tianfeng(China University of Petroleum,Beijing,Beijing 102249,China;CNOOC Research Institute Ltd.,Beijing 100028,China;National Energy Deepwater Oil and Gas Engineering Technology Research and Development Center,Beijing 100028,China)
出处
《中国海上油气》
北大核心
2025年第5期193-203,共11页
China Offshore Oil and Gas
基金
国家能源深水油气工程技术研发中心主任基金(2024)项目前瞻课题“基于环焊缝疲劳失效的深水立管可靠性评价方法与设计理论(编号:KJQZ-2024-2103)”
国家科技重大专项“深水油气干式生产处理平台关键技术与装备”课题3“浮式深水干式油气生产处理平台生产立管关键技术研究(编号:2024ZD1403303)”
国家重点研发计划项目“深海采矿非金属非黏结柔性混输管关键技术研究”课题1“深海采矿非金属柔性混输管设计及其关键技术研究(编号:2022YFC2803701)”部分研究成果。
