【作者】 陈团海；

【导师】 陈国明；

【作者基本信息】 中国石油大学 ， 安全技术及工程， 2011， 博士

【摘要】 目前世界范围内有大量老龄平台需要延寿继续服役,为保证平台延寿服役期间的安全,必须对老龄平台结构完整性进行动态评估,研究相关的风险控制技术。本课题结合国家863项目“近海老龄平台延寿技术研究”、国家自然科学基金项目“面向老龄平台延寿工程的寿命预测与管理理论及方法研究”和中央高校基本科研业务费专项资金资助项目“南海深水油气开采风险控制技术应用基础研究”中老龄平台结构完整性管理的内容展开研究,在老龄平台时变可靠性、动态疲劳可靠性、风险动态评价与控制技术、基于风险的老龄平台检修优化等4个方面取得了较大进展,并综合所取得理论与技术成果,开发老龄平台结构完整性管理软件系统APSIMS,为技术理论的实际工程应用提供方便。本文主要研究成果归纳如下:1老龄平台整体时变可靠性分析将老龄平台延寿服役期间的结构抗力与载荷效应作为随机过程,研究老龄平台在极值海洋环境载荷作用下的时变可靠性。分析老龄平台抗力衰减的因素,研究腐蚀和裂纹两种主要因素对平台抗力的影响规律,根据腐蚀与裂纹参量随时间的变化分析平台抗力衰减规律,确定平台抗力衰减的多项目函数、幂函数和指数函数共3种函数模型;分析老龄平台延寿服役期间可能出现的极值海冰、台风和地震3种极值载荷概率特征,研究平台在不同极值载荷作用下的载荷效应,提出平台载荷效应概率模型分析方法;根据抗力—载荷干涉理论,分别采用时间离散法、等效载荷法和时间增量法3种方法建立基于极值载荷的老龄平台时变可靠性分析模型;以此为基础利用可靠性更新理论,研究两种老龄平台时变可靠性更新方法:基于检测资料的Bayes更新与基于验证载荷的更新。2老龄平台动态疲劳可靠性分析随着老龄平台服役时间的增长,平台结构疲劳损伤不断累计从而导致平台疲劳抗力下降,基于S-N曲线法和断裂力学法建立平台疲劳损伤累计模型和裂纹扩展模型,采用时域分析法和频域分析法计算名义应力;将管节点作为平台疲劳分析的基本单元,提出基于路径映射技术的管节点热点应力集中系数计算方法,并研究复合载荷下管节点应力集中系数沿管节点分布规律;分别将平台延寿服役期间疲劳损伤和裂纹扩展尺寸作为随机过程,基于动态疲劳损伤干涉理论和动态裂纹尺寸干涉理论,建立动态疲劳可靠性分析模型;考虑腐蚀对平台疲劳损伤累计与裂纹扩展的影响,研究腐蚀作用下疲劳应力范围随时间的变化函数,建立考虑疲劳与腐蚀交互作用的平台动态可靠性模型;基于检测与维修情况对平台动态可靠性进行更新,给出在2种不同检测结果与维修情况下的动态疲劳可靠性更新模型;将可靠性分析提高至系统层面,分析平台系统动态疲劳可靠性,研究老龄平台系统失效模式确定方法与系统动态可靠性计算方法。3老龄平台动态风险评价与控制技术研究将风险作为老龄平台结构完整性评价指标,采用故障类型及影响分析法对老龄平台风险进行识别,借助于有限元分析方法确定危险因素对平台结构的影响程度,采用故障类型和影响、危险度分析法对平台结构风险进行半定量评价;研究老龄平台结构风险衡量方法和接受准则,通过建立老龄平台失效事故树模型计算平台失效概率,研究平台失效后果分析方法,根据“最低合理可行(ALARP)”原则对老龄平台进行定量风险评价;考虑到平台延寿服役期间结构失效概率与风险后果的动态特征,研究老龄平台动态风险评价方法;针对风险超过临界值的情况提出4种风险控制技术,采用ANSYS软件建立每种风险控制方法评价模型,并对采取风险控制措施后的平台结构风险进行动态评估,利用数值方法验证这些风险控制技术的有效性。4基于风险优化的老龄平台检测与维修规划检测与维修是保证老龄平台结构完整性的主要方式,为确定老龄平台合理的检修方案,建立基于风险的老龄平台检修规划优化模型,分析模型中检测、维修和失效期望费用的计算方法,制定采用MATLAB工具箱中遗传算法进行检修优化求解的步骤;鉴于各种期望费用为检测、维修和失效事件发生概率的函数,建立这三个事件的安全裕度方程,根据事件树模型分析各个检测时间点平台需要检测、维修以及结构失效的概率。首先根据建立的检修优化模型对检修过程中的检测次数和时间、检测方法以及维修方法三种单项影响因素进行优化,并对相关费用进行敏感性分析;再根据实际情况,综合考虑各种因素的不确定性,对各种检测与维修方法进行组合,并对每种方案均进行基于风险的检修优化分析,通过对优化结果确定最佳检修方案。5老龄平台结构完整性管理系统的研制为方便结构完整性管理理论的应用,采用Visual Basic 6.0语言开发老龄平台结构完整性管理软件系统APSIMS。根据API规范中海洋平台结构完整性管理流程建立详细的老龄平台结构完整性管理框架,据此对软件APSIMS的系统结构进行设计;采用Microsoft Office Access建立软件数据库系统实现软件内部的数据储存与传输,共设计平台结构数据库、海洋环境载荷数据库和结构检测数据库3类数据库,通过调用ANSYS和MATLAB作为程序接口完成平台有限元分析和检修优化求解;APSIMS软件集老龄平台结构完整性管理理论集成为一体,主要功能包括动态可靠性分析、风险分析、风险控制与评价、检修决策与规划,能够实现对老龄平台延寿服役期间的结构完整性进行全过程管理。更多还原

【Abstract】 At present, there are a large number of ageing platforms that are needed to extend life for continual service in the world. To ensure the continued safe performance of these ageing platforms, it’s necessary to research on the dynamic structural integrity assessment and risk management technologies. The dissertation focuses on structural integrity management (SIM) for ageing offshore platforms, which is a part of the“863”High Technology Research and Development Program of China (No. 2006AA09Z355) of“Research on Life Extension Technology for Ageing Offshore Platforms”, the National Natural Science Foundation Program (No. 50679083) of“Research on Life Prediction Methods and Management Theory of Ageing Offshore Platforms for Life Extension”and the Fundamental Research Funds for the Central Universities (No. 09CX05008A) of“Fundamental Research on Risk Control Techniques Application for Deepwater Oil and Gas exploitation in South China Sea”. The main investigate issues include the time-dependent reliability, dynamic fatigue reliability, risk assessment and management technologies, and risk-based inspection and repair planning for ageing platforms. And based on the theoretical achievements, the ageing platform structural integrity management system software APSISM is developed. The main work is summarized as follows:1. Time-dependent reliability analysis of ageing platformsAs ageing effects would imperil the safety and serviceability of the structures, the global time-dependent reliability of ageing platforms is investigated. The stressors of resistance degradation were analyzed, and within these factors, structural deterioration of the platforms by corrosion and crack are studied. According to the function of corrosion process and crack propagation with time, the resistance degradation models with polynomial expression, power function expression and exponential expression are proposed. The probabilistic characteristics of the extreme loads including extreme ice load, typhoon load and seismic load are analyzed. The methods for determination of the load effect and its probabilistic characteristics are presented. Based on the resistance-load interference theory, the global time-dependent reliability analysis model of ageing platforms is proposed through discrete time method, equivalent load method and incremental time method. On the based of the time-dependent model, reliability updating based on Bayesian approach and proof load is studied.2. Dynamic fatigue reliability analysis of ageing platformsWith the service time increasing, the fatigue resistance of ageing platforms degrades for fatigue damage accumulation. Based on the S-N curve approach and fracture mechanics approach, the models of fatigue damage accumulation and crack propagation are established. The time domain analysis and frequency domain analysis are employed to calculate the nominal stress in the fatigue analysis model. The tubular joint is taken as the basic element of fatigue analysis, by virtue of path mapping technique, a new numerical method on stress concentration factors (SCFs) calculation of welded tubular joints is proposed, and the SCF distribution of tubular joints under combined loadings is studied. Taking fatigue damage accumulation and crack propagation as stochastic processes, the dynamic fatigue reliability analysis models are proposed based on fatigue damage interference and crack parameters interference theories. Considering the effect of corrosion, the fatigue stress under corrosion condition is investigated, and the dynamic reliability analysis model including the fatigue- corrosion interaction is proposed. The reliability is updated based on inspection and repair data, and the updating models under different results of inspection and repair are presented. According to the system-level reliability theory, the methods for failure modes determination and system reliability calculation are presented, and the dynamic fatigue system reliability of ageing platforms is studied.3. Dynamic risk assessment and risk managementApplying risk assessment to SIM of ageing platforms, the failure mode and effect analysis (FMEA) method is used for risk identification. By virtue of finite element analysis, the criticality of hazardous factors is classified, and the structural risk is assessed semiquantita -tively by failure modes and effect and criticality analysis (FMECA) method. For quantitative expression of risk, risk estimation and risk acceptance criteria are investigated. The failure probability of ageing platform is calculated by fault tree analysis method. According to the ALARP (“As Low As Reasonably Practicable”) principle, the quantitative risk assessment is carried out. As the risk of ageing platform is varied with time, the dynamic risk is studied. Mitigation and risk reduction measures are considered if the risk of the platforms does not meet the fitness-for-purpose acceptance criteria, and four methods for risk reduction are proposed in this paper. The validity of these measures is verified by finite element method.4 Risk-based inspection and repair planningInspection and repair are the main ways to ensure structural integrity of ageing platforms, and at the same time they bring about economic burden if the times of inspection and repair increase. Therefore, it is necessary to develop the optimal inspection and repair planning. The planning programme is formulated as an optimization problem where the expected lifetime costs are minimized with a constraint on the minimum acceptable reliability index, and the expected inspection, repair and failure costs models are proposed. The genetic algorithm in Matlab toolbox is employed to solve the optimization problems. The safety margins are presented for the inspection events, the repair events and the failure events of ageing platforms. Moreover, based on event tree analysis, the formula is derived to calculate inspection probability, repair probability and failure probability at the time of each inspection. Based on the optimization model, the optimal results of single factor including inspection times, inspection intervals, inspection methods and repair methods are obtained. Then all the indeterminate factors are considered in the optimization problem, and 10 candidate strategies are determined by combining different inspection methods and repair methods. In each strategy, the inspection times and inspection intervals are optimized, and by comparison between the different inspection and repair strategies, the best inspection and repair planning is determined.5 Software development of ageing platform structural integrity management systemFor convenient application of the ageing platform SIM theory porposed in the paper, the ageing platform SIM software system APSIMS is developed by Visual Basic 6.0 program. The framework of ageing platform SIM is constructed according to the processes of fixed offshore structures SIM in API standard. And based on the framework, the software structure of APSIMS is designed. The database system is established by Microsoft Office Access for data storage and transmission. And three kinds of database, including platform structure database, environmental load database and inspection database, are designed. ANSYS program and MATLAB program are employed as application programming interface for structural analysis and optimization solution. The main functions of APSIMS consist of dynamic reliability analysis, risk analysis, risk management and assessment, and risk-based inspection and repair planning, which can implement SIM of all the life extension period for ageing platforms.更多还原