【作者】 傅俊杰；

【导师】 杨和振；

【作者基本信息】 上海交通大学 ， 船舶与海洋结构物设计制造， 2010， 硕士

【摘要】 近年来我国加快开发南海资源的脚步,因此研发具有自主核心技术的深海工程装备已成为优先任务。钢悬链立管(SCR)是进行深海资源开发的关键设备,它具有复杂的非线性动力特性,其独特的结构形式为设计、制造、安装和安全服役提出了新挑战。触地点(TDP)是钢悬链立管最初接触到海床的部位,也是结构分析的特征点。该位置是悬垂段与流线段的连接点,易发生疲劳破坏,进而危及整个采油系统的安全。该区域有部分初始悬空的立管会浸入海底,与土壤发生相互作用,同时涉及到大变形与非线性。所以,触地点是钢悬链立管数值分析的难点,需要展开针对性的研究。本文针对深海钢悬链立管的动力分析及触地点的疲劳特性问题进行深入研究,主要工作如下:1、考虑海洋环境,建立基于非线性弹簧的钢悬链立管Lumped-Mass有限元耦合模型。探讨了钢悬链立管的发展及数值分析、疲劳分析的研究进展,在此基础上明确了研究方法,确立触地点为立管整体分析过程中需要重点关注的区域。借助P-y曲线考虑土壤的三维非线性反力,用修正后的Morison方程仿真海洋环境载荷,最终成功构造立管数值模型,并通过实验分析验证了该模型的合理性。2、展开多工况非线性动力分析,得到立管的动力特性,重点研究触地点的动力响应。相对于频域动力分析,时域分析能更好的处理立管强非线性问题,其计算精度更高。结构整体分析的结果表明:在不同工况下,上端点均是刚性立管疲劳分析的特征点,而钢悬链立管疲劳分析的特征点位于触地点区域。通过比较多工况下的触地点响应时程,展示各因素的影响程度:浮体运动与制造材料变化的作用较大,而波浪改变对触地点动力特性的影响有限。此外,讨论的其它环境载荷与设计参数也具有一定影响。3、参数敏感性分析立管工作寿命,着重探讨触地点疲劳特性,提出改善疲劳寿命的建议。基于立管动力研究,展开S-N曲线法疲劳分析,对比计算结果可知:触地点的疲劳寿命最小,定期变换该区域,可缓解疲劳累积;合理采用S-N曲线、改良制造工艺,能优化特征点应力集中;浮体垂荡对立管疲劳寿命影响较大,适当选择浮体有利于缓和耦合运动;借助浮力装置或混合形式,可以改善土壤非线性反力作用;在特征位置使用保护外层或钛合金等材料,有助于拓展立管适用空间。更多还原

【Abstract】 Nowadays, China has accelerated the exploitation in the South China Sea. The development of deep-sea engineering equipments with core technology has become a priority. The steel catenary riser (SCR) is the key apparatus in ultra-deep water work. Since the complex nonlinear dynamic behaviors, the SCR brings new challenges in design, manufacture, installation and security application.The touchdown point (TDP) is the characteristic point in structure analysis, also the combined point of sag bend and flow line. The most vulnerable location to fatigue damage exists at the TDP, where the riser first touches the seafloor. Furthermore, the SCR fatigue damage will endanger the whole oil production system. The SCR-Seabed interaction relates to the large deformation and nonlinear reaction. Parts of the riser interact with the soil significantly near the touchdown zone, which above the seabed at the beginning. Therefore, the TDP is the principal region to be focused in numerical analysis.Dynamic analysis of deepwater steel catenary risers and fatigue characteristic assessment at the touchdown point are studied in this work, the main tasks are given as follows:1. Based on nonlinear springs, a Lumped-Mass SCR coupling model is established in marine environment.On the basis of discussions in the SCR comprehensive development, numerical research and fatigue analysis, the study methodology is brought. The TDP is defined as the principal objective during the whole investigation. Due to P-y Curve and Morison Equation, three-dimensional seabed reactions and marine-ambient excitations are simulated respectively. Above all, the SCR model is proved successfully through reasonable analysis.2. Acquire nonlinear dynamic features of the SCR in different operating conditions, and focus on dynamic responses at the TDP.Comparing with frequency domain dynamic analysis, it’s better and more accurate to solve the strong nonlinear problems of SCR in time domain. The overall structure research indicates: in fatigue assessment, top end is the key location of rigid riser in different cases, and the TDP is the characteristic point of SCR. By studying dynamic responses in multi-operating conditions, the impacts of various factors to the TDP are discussed: The vessel motion and construction material are significant influences. On the contrary, the wave load couldn’t change dynamic features at the TDP directly. In addition, other environment loads and design parameters have some effects as well.3. The TDP is investigated as a key position in the SCR fatigue study, meanwhile, some fatigue life enhancements are stated.Through dynamic analysis and S-N Curve Method, the results of fatigue assessment are shown: The TDP appears the shortest fatigue life, and the fatigue accumulation can be alleviated by transforming the touchdown zone regularly. Selecting S-N curves carefully or optimizing manufacturing crafts are helpful to control the stress concentration in the feature point. The SCR fatigue life is highly sensitive to vessel heave, so an excellent vessel could relieve coupling movement notably. Use of the buoyancy device or hybrid form is an available approach to better the soil nonlinear reaction. Besides, the employment of protective coating and titanium in characteristic locations could expand the SCR application.更多还原