【作者】 刘翔；

【导师】 李刚； 程耿东； 岳前进；

【作者基本信息】 大连理工大学 ， 工程力学， 2008， 博士

【摘要】 考虑到我国渤海冬季结冰的环境条件和边际油田的油藏特性,渤海海洋平台多采用比较经济的钢质导管架固定式平台,并通过安装破冰锥体的措施来抗冰。多年的现场监测发现平台存在冰激振动现象,然而,现行平台设计规范没有明确冰激振动的处理方式,所以经济型抗冰振导管架平台的动力设计成为渤海海洋平台的关键问题。本文基于多年的冰激振动现场监测和冰荷载研究的成果,结合“十五”863项目“新型平台抗冰振的关键技术”(2001AA602015-1),开展适用于渤海的面向动力性能的抗冰导管架平台优化设计研究。将基于性能的设计思想和优化概念引入新型平台抗冰振设计研究中,重点研究抗冰导管架平台的动力优化设计,深入讨论了抗冰导管架平台的性能定义、抗冰振设计动冰力的确定、冰激振动的分析和抗冰振优化模型的建立等关键问题,为渤海边际油田的经济型抗冰导管架平台设计提供相关的理论、方法与技术支持。本文主要研究内容如下:1.在基于性能的设计框架下,明确抗冰导管架平台的性能定义,提出在设计优化中把极值静力性能要求和动力性能要求加以区分处理的解决方案,对抗冰导管架平台明确提出了面向动力性能的优化问题的两种列式。2.强烈的冰激振动会导致显著的管节点动应力,这会引发节点的冰激疲劳。为了解决复杂管节点疲劳分析时精度和效率之间的矛盾,在可兼顾整体和局部结构特征的有限元模型的基础上结合虚拟激励法的特点,提出了一个复杂节点冰激疲劳分析的高效谱分析方法。3.针对有一类关注减重并需要考虑冰激疲劳的平台,如无人井口平台,从不同的角度入手将冰激疲劳和优化结合,分别提出了考虑节点疲劳寿命和考虑节点疲劳可靠性的两种抗冰导管架平台结构优化问题。4.提出了短期动冰力的概念和冰激加速度的条件超越概率的计算方法,在此基础上同时考虑海冰环境的不确定性和结构特性的差异,提出了确定面向抗冰导管架平台动力分析的短期动冰力的两种方法:基于失效概率的方法和基于损失期望的方法。5.针对有一类对冰激振动加速度要求高且需限制材料用量的平台,如有人居住的生活动力平台,提出了目标函数为冰激甲板加速度均方根值的抗冰导管架平台结构优化问题,在优化中整合了所建议的确定短期动冰力的方法,旨在解决在优化中需要考虑海冰环境不确定性和结构特性变化的问题。6.建立了抗冰导管架平台的概念模型,推导抗冰导管架平台的概念参数和整体性能之间的关系,给出了一个参数优化问题的表述,分析了参数对性能的影响,讨论了刚性和柔性抗冰设计的特点,指出适合渤海的经济型抗冰导管架平台设计应采用柔性抗冰设计,而面向动力性能的抗冰导管架平台优化是实现它的重要手段之一。更多还原

【Abstract】 In view of characteristics of the enviroments and the oil and gas recourses in the Bohai Sea, where there are many ice-infested marginal fields, the economic steel fixed jacket platforms with the ice-beaking cone have been used widely. For some in-service plalforms in the Bohai Sea, in-field observations show that there are considerable ice-induced vibrations in some cases. However, the current codes do not speicify how to consider the ice-induced vibration. The dynamic problem of the economic ice-resistant jacket platform becomes a key issue. Under the framework of 863 Program (No. 2001AA602015-1), this paper introduced the concepts of performance-based design and structural optimization into the research of the novel ice-resistant platform, and focused on the dynamic design optimization for ice-resistant jacket platform, and discussed key issues, such as the definitions of performances of the ice-resistant jacket platform, the determination of dynamic ice force for dynamic design, the analysises of ice-induced vibrations and the formulation of ice-resistant design optimization.Related studies of this paper are listed as follows:1. In framework of the performance-based design, the definitions of performances of the ice-resistant jacket platform has been specified. It is suggested that the extreme static performance requirments and the dynamic performance requrirments should be considered separately in design optimization. For ice-resistant jacket platmorms with ice-breaking cone, two forms of dynamic performance-oriented design optimization for ice-resistant jacket platform are developed.2. Severe ice-induced vibrations can cause significant dynamic stress of tubular joints, which could evoke fatigue of tubular joints. In order to overcome the conflict beteen the accuracy and the efficiency of fatigue analysis for complex tubular joints, an efficient spectral method of ice-induced fatigue analysis for complex tubular joints has been proposed, which employs the pseudo exitation method and a mixed finite element model that can reflect the global and local characters of the jacket platform.3. Two detailed optimization formulations of ice-resistant jacket platforms have been developed from different views to consider the ice-induced fatigue of tubular joint: optimum design considering fatigue life of tubular joints and optimum design considering fatigue reliability of tubular joints, respectively. These proposed optimization models can meet the requirements of the platform such as the wellhead platform without crews, which should consider ice-induced fatigue and weight reduction,4. The definition of short-term dynamic ice cases has been specified and an approach to assessing the conditional exceedance probability of ice-induced acceleration is proposed. Based on these, the framework of determination of the short-term dynamic ice case for dynamic analysis of ice-resistant jacket platform is developed, including two approaches: the failure probability-based approach and the expected loss-based approach. This framework can cover the influence of the uncertainty of ice environments and the distinction between different ice-resistant structures.5. The acceleration-oriented design optimization of ice-resistant jacket platforms has been developed, which could emphasize ice-induced deck acceleration and need controlling weight. This model can treat the requirements of the platform such as accommodation and power platform with crews. The objective function is the root mean square value of ice-induced deck acceleration caculated by the proposed approach to determination of the short-term dynamic ice force. In this way the uncertainty of ice environments and the variability of ice-resistant structure could be reflected during design optimization.6. A simplified conceptual model of ice-resistant jacket platform is developed and employed to make some analytical discussions. The influence of conceptual parameters on conceptual performances of ice-resistant jacket platform is studied in analytical form. Subsequently, a statement of performance-oriented conceptual parameter optimization is proposed. The characteristics of the rigid ice-reistant design and the flexible ice-resistant design are discussed. It is pointed out that in order to meet the requirements of the Bohai Sea the ice-resistant jacket platform design should follow the flexible ice-resistant design and pay more attention to ice-induced vibrations, and this intent could be implemented by the proposed dynamic performance-oriented ice-resistant jacket platform optimization as one of important approaches.更多还原