A New Probability of Detection Model for Updating Crack Distribution of Offshore Structures

1 .IntroductionNondestructiveinspection (NDI)isveryimportantforensuringthereliabilityofoffshorestructuresintheirservicelives (Lauraetal.,1 996 ) .Itiswellknownthatdetectionofflawsinvolvesconsider ablestatisticaluncertainties.Asaresult,theprobabilityofdetection (POD)forallflawsofagivensizehasbeenusedintheliteraturetodefinethecapabilityofaparticularNDItechniqueinagivenen vironment.SincethedataofPODusuallyscatterlargely ,itisdifficulttodeterminewhichmodelfitstheavailabledatabest.Thismodelun…     

受损结构余度评估的半概率方法

本文给出了一种结构系统余度的度量定义，基于结构系统机构化失效概念和相当可靠性指数。本文提出了对受损结构安全评做的半概率方法。所示算例表明了本方法的有效性。     

深水半潜式生产平台耦合动力特性对比研究

应用数值模拟与模型试验相结合的方法研究半潜式生产平台系泊状态下的耦合动力特性。建立耦合分析模型,时域内计算求解平台的动力响应,选取缩尺比为1∶60,采用等效截断模型方法对数值模拟结果进行验证。通过对比模型试验与数值模拟结果发现:等效截断系泊系统可以较好地模拟平台的位移响应,但在系泊张力方面却差异较大,此外极端海况下平台的甲板上浪问题也必须得到充分重视。     

海洋工程风险评估的现状和发展

复杂工程风险评估是近年来得到迅速发展的新的系统化的方法,本文讨论了适合于海洋工程风险评估的理论框架,涉及了动态系统风险评估和人因可靠性分析技术,为其进一步发展提出方向,文中给出了ＴＬＰ风险评估的实例。该框架同样适用于其它复杂的工程系统。     

Simplified Prediction Model for Vortex-Induced Vibrations of Top Tensioned Risers

According to the characteristics of deepwater top tensioned risers, a simplified model is presented to predict the multi-modal response of vortex-induced vibration （VIV） in non-uniform flow based on energy equilibrium theory and the exporimental data from VIV self-excited and forced oscillations of rigid cylinders. The response amplitude of each mode is determined by a balance between the energy fed into the riser over the lock-in regions and the energy dissipated by the fluid damping over the remainders. Compared with the previous prediction models, this method can take fully account of the intrinsic nature of VIV for low mass ratio structures on lock-in regions, added mass and nonlinear fluid damping effect, etc. Moreover, it is the first time to propose the accurate calculating procedure for VIV amplitude correction factor by solving energy equilibrium equation and a closed form solution is presented for the case of a riser of uniform mass and cross-section oscillating in a uniform flow. The predicted values show a reasonable agreement with VIV experiments of riser models in stepped and sheared currents.     

惠州25-8 DPP组块动力定位浮托安装研究

从动力定位船舶浮托安装研究出发,归纳了动力定位船舶浮托安装的优势,并以"海洋石油278"驳船进行组块浮托安装为例,提出了南中国海大型组块采用动力定位船舶浮托安装的气候窗及动力定位能力分析方法,给出了惠州25-8 DPP组块动力定位浮托安装的关键设计结果。本研究对环境恶劣海况下的大型组块浮托安装具有一定借鉴意义。     

考虑节点柔度的海洋平台结构总体分析

本文提出了一种改进的空间梁单元,可以考虑单元两端节点的柔性,用来模拟海洋平台等工程结构的柔性接头特性,用此改进梁单元作海洋平台结构总体分析,不仅简单可行、通用性强,而且有足够的精度,算例结果表明了它的有效性和可靠性。     

34万吨级FPSO的中横剖面优化设计

以中横剖面的面积最小为目标函数，应用自适应步长随机搜索法，对34万吨级FPSO中横剖面进行了优化设计，并将规范设计结果和优化设计结果进行了比较，优化效果较好。     

Risk Based Optimal Inspection and Repair Planning for Ship Structures Subjected to Corrosion Deterioration

A framework of risk based inspection and repair planning was presented to optimize for the ship structures subjected to corrosion deterioration. The planning problem was formulated as an optimization problem where the expected lifetime costs were minimized with a eonstraint on the minimum aceeptable rehability index. The safety margins were established for the inspection events, the repair events and the failure events for ship struetures. Moreover, the formulae were derived to calculate failure probabihties and repair probabilities. Based on them, a component subjected to corrosion is investigated for illustration of the process of selecting the optimal inspection and repair strategy. Furthermore, some sensitivity studies were provided. The results show that the optimal inspection instants should take place before the reliability index reaches the minimum acceptable reliability index. The optimal target failure probability is 10^-3. In addition, a balance can be achieved between the risk cost and total expected inspection and repair costs by means of the risk-based optimal inspection and repair method, which is very effective in selecting the optimal inspection and repair strategy.     

Truss Spar平台桁架管节点疲劳分析

Truss Spar平台在风、浪、流的作用下,结构受力十分复杂,准确分析其疲劳强度相当困难。通过建立Truss Spar平台三维有限元模型,利用HydroD软件进行载荷预报、波浪搜索,得到产生最大应力幅响应的最不利浪向和相位角。运用Sestra软件进行整体有限元分析,得到的结果作为桁架管节点细化模型的边界条件,再用Nastran软件进行局部分析求得节点的热点应力,修正壁厚影响。最后根据DNV规范的S-N曲线计算了管节点的疲劳寿命。