【作者】 孙玉武；

【导师】 聂武；

【作者基本信息】 哈尔滨工程大学 ， 船舶与海洋结构物设计制造， 2001， 博士

【摘要】 渤海8号平台是一座由槽口式改为悬臂式的自升式平台，并已经进入后服役期阶段的老龄化平台。由于改装改变了平台的结构形式和应力分布，造成承载能力与外载荷的不匹配。本文根据渤海8号在使用中出现的问题，对处于升船钻井状态的平台从静力、疲劳、稳定性和变形等多方面进行了分析，并在此基础上进行结构强度校核和损伤评估，提出改进平台结构强度性能的方案。 首先，建立渤海8号平台整体空间板梁组合结构有限元分析模型。在环境载荷和工作载荷作用下，计及钻井载荷动载效应，利用结构有限元软件计算平台不同工况下的应力分布，根据结构强度和规范要求校核平台主船体结构及桩腿的静强度。 其次，本文通过分析提出了平台主体结构不同以往的疲劳区域和循环载荷，采用P-S-N曲线方法和线性累计损伤理论，计算在由钻井载荷波动引起的循环载荷作用下平台升降室围井区垂直焊缝处疲劳计算点的累积损伤，并进行寿命估算。疲劳计算中考虑了焊接残余应力、应力集中和平均应力等因素的影响。 本文以试验为基础，通过比较性分析建立平台升降室疲劳区域的裂纹扩展动态模型，预报裂纹扩展长度，估算裂纹扩展寿命。并采用剩余强度干涉理论和损伤容限分析思想对平台进行可靠性评估。然后根据现场裂纹扩展测量数据对裂纹扩展预报和结构可靠性进行贝叶斯修正。 针对机械甲板变形问题，利用理论和经验公式进行整体板架和局部板格屈曲分析。通过与有限元应力计算结果比较，校核机械甲板的稳定性。在确定屈曲类型和原因的基础上，提出消除局部板格屈曲的方案。 最后，利用平台整体结构有限元位移计算结果，分析悬臂梁的最大挠度和变形曲线。根据业主要求和结构特点，提出减小悬臂梁挠度和结构应力的改装方案，进行结构再分析，定量计算改装对悬臂梁挠度的影响。更多还原

【Abstract】 Bohai8 jack-up platform was refitted from slot type to cantilever-beam type and is in its later service period now. The refitting changes the structure form and stress distribution and thus causes mismatching between carrying capacity and loads. According to the problems of BohaiS met in service,the platform that is in lift state is analyzed from aspects of static,fatigue,buckling and deformation. On this base,the structure strength check and damage evaluation are carried out and a proposal plan for improving strength of the platform structures in the next refittment is brought forward.First,integral special shell-beam element model of BohaiS is set up. After applying environment loads and work load and taking into account dynamic effect of drilling load,the stress distributions of the platform under various conditions are calculated by using finite element analysis software. Then the static strength of main hull and legs are checked.Second,a fatigue area of the main hull and cycling load that is different from previous (i.e. typical fatigue of tubular joints of legs) is put forward in this thesis. It is found through analysis that the fatigue happens at the vertical weld of yoke house and is caused by the fluctuation of drilling load. The fatigue accumulated damage is calculated and fatigue life estimated by adopting P - S - N curve method and linear accumulative damage theory. The affects of residual stress,stress concentration and mean stress are taken into account in calculation.On the base of experiment and comparative study,a dynamic crack propagation model of the yoke house fatigue area is established,which can be used to forecast the length of crack and estimate crack propagation life. By using residual strength interference theory and damage tolerance idea,the reliability of the structure is evaluated. Then the crack propagation rule and reliability index are modified through using field crack length measured data and Bayesian method. To deal with the deformation problem of machinery deck,global and localbuckling analysis are carried out by using theoretical and experiential formula in this thesis. Comparing with stress results from finite element analysis,the reason and type of buckling are confirmed and a plan to eliminate local plate buckling is given.At last,the maximum deflection and integral deformation of cantilever-beam structure are analyzed on the base of finite element analysis. Due to the requirements of the ship owner and structure characters,a structure refit scheme of letting up the deformation of the cantilever-beam is brought forward and quantitative calculation is conducted.更多还原