Cost-Benefit Assessment of Inspection and Repair Planning for Ship Structures Considering Corrosion Model Uncertainty

Owing to high costs and unnecessary inspections necessitated by the traditional inspection planning for ship structures, the risk-based inspection and repair planning should be investigated for the most cost-effective inspection. This paper aims to propose a cost-benefit assessment model of risk-based inspection and repair planning for ship structures subjected to corrosion deterioration. Then, the benefit-cost ratio is taken to be an index for the selection of the optimal inspection and repair strategy. The planning problem is formulated as an optimization problem where the benefit-cost ratio for the expected lifetime is maximized with a constraint on the minimum acceptalbe reliability index. To account for the effect of corrosion model uncertainty on the cost-benefit assessment, two corrosion models, namgly, Paik＇ s model and Guedes Soares＇ model, are adopted for analysis. A numerical example is presented to illustrate the proposed method. Sensitivity studies are also providet. The results indicate that the proposed method of risk-based cost-benefit analysis can effectively integrate the economy with reliability of the inspection and repair planning. A balance can be achieved between the risk cost and total expected inspection and repair costs with the proposed method, which is very. effective in selecting the optimal inspection and repair strategy. It is pointed out that the corrosion model uncertainty and parametric uncertaintg have a significant impact on the cost-benefit assessment of inspection and repair planning.     

船体结构腐蚀检测规划的成本及效益分析

建立了基于风险的船体结构腐蚀优化检测规划的成本-效益分析模型。以费效比作为选择最优检测策略的标准,最优的检测策略是在保证结构设计工作寿命期内的可靠指标大于最低可靠指标的基础上,使得结构生命周期内总的费效比最大。在此基础上,以受点腐蚀损伤的船体构件为例,对其检测策略进行了成本-效益评估,并对计算结果进行了敏感性分析。结果表明,基于风险的成本及效益分析方法可以将检测规划的经济性和可靠性有效地结合起来,能够在风险与成本之间达到一种平衡,它在优化检测策略时是有效的。     

Cost-reliability consequence resource allocation: Application to an offshore structure

A model is given for the planning of the inspection and maintenance operations of a system: an application to an offshore structure is described. The objectiveis to minimize the total cost of inspections and consequences of failures, subject to an upper boundon the total failure probability of the system. An incremental algorithm is defined for the approximate solution of the problem, and a method is described for the evaluation of the quality of any feasible solution in terms of bounds of the optimal objective value. The incremental algorithm solves the problem parametrically for certain values of the system reliability. The model has been applied to obtain an optimal inspection plan against the consequences of gross errors, accidental events, fatigue and corrosion in terms of input describing element importance values, element reliability values, error detection probabilities, error detection costs and error repair costs for parametrical variations of the structural reliability.     

基于风险的海洋结构物无损检测功能的分级

提出了基于风险的海洋结构物无损检测功能分级方法,采用检测概率、错误识别概率和裂纹出现概率度量检测功能,并修正了错误识别概率的取值范围。根据风险值对无损检测功能进行了分级,研究了风险值随检测概率、错误识别概率和裂纹出现概率的变化规律,分析了风险值对检测费用、维修费用及失效费用的敏感性。在此基础上,将基于风险的海洋结构物无损检测功能分级方法应用于优化检测策略,用算例证明了文中所提方法的有效性。     

Failure Statistics Analysis Based on Bayesian Theory: A Study of FPSO Internal Turret Leakage

The load and corrosion caused by the harsh marine environment lead to the severe degradation of offshore equipment and to their compromised security and reliability. In the quantitative risk analysis, the failure models are difficult to establish through traditional statistical methods. Hence, the calculation of the occurrence probability of small sample events is often met with great uncertainty. In this study, the Bayesian statistical method is implemented to analyze the oil and gas leakages of FPSO internal turret, which is a typical small sample risk but could lead to severe losses.According to the corresponding failure mechanism, two Bayesian statistical models using the Weibull distribution and logarithmic normal distribution as the population distribution are established, and the posterior distribution of the corresponding parameters is calculated. The optimal Bayesian statistical model is determined according to the Bayesian information criterion and Akaike criterion. On the basis of the determined optimal model, the corresponding reliability index is solved to provide basic data for the subsequent risk assessments of FPSO systems.     

基于风险海洋结构物检测及维护研究进展

随着海洋石油天然气资源的不断开发,海洋结构物得到了广泛的应用。长时间持续工作于海洋环境以及一旦失效代价高昂的特点使得海洋结构物的安全问题倍加瞩目。基于风险的检测和维护将海洋结构物的风险与费用相结合,可以在满足安全要求的前提下合理地降低运营费用,是目前国际上研究领域的热点问题。通过分析基于风险的海洋结构物检测和维护的国内外研究现状,对检测及维护操作过程中的一些关键问题和目前主流的研究方法及应用情况做了概述。最后讨论了海洋结构物检测维护研究中存在的一些问题,提出了今后的研究方向。基于风险的检测和维护将是今后一个值得关注的重要课题。     

船舶的微生物腐蚀与防护技术*

海洋环境中的微生物腐蚀已被公认为是海洋工程金属构筑物的腐蚀破坏的重要形式。航行在海洋中的船舶不仅受到海水腐蚀的影响,各个部件还会受到微生物腐蚀的影响。严重的微生物腐蚀会导致管路阻塞、部件失效和腐蚀穿孔,不仅影响船舶设备正常运行,也严重威胁船舶安全。本文系统分析了船舶微生物腐蚀发生的位点和危害、不同位点的腐蚀微生物群落结构特征、船舶材料的微生物腐蚀以及不同防护技术的适用范围,并在此基础上提出对船舶微生物腐蚀研究工作的建议。     

Minimum time-energy trajectory planning for automatic ship berthing

A ship optimal trajectory planning method based on the dynamic model of the ship is presented. First a mathematical modular model is introduced for describing the non-linear dynamics of the ship. Then the problem of optimal trajectory planning is discussed. The trajectory is obtained through the optimization of a time-energy criterion, taking into account constraints on the steering system, environment, non-linearities, and non-convexity of the state space equations. The discrete augmented Lagrangian approach is used to compute the optimal constrained controller. The method was programmed on a HP700 workstation. This approach was applied to automatic ship berthing maneuver     

Checking vulnerability to pure loss of stability in long crested following waves: A probabilistic approach

This paper presents a probabilistic methodology for the analysis of the vulnerability of a ship to the risk of inception of pure loss of stability events. A pure loss of stability failure is modelled as the persistence of the metacentric height below a critical level for a too long time. The metacentric height is modelled as a stationary Gaussian process with a spectrum obtained from the sea elevation spectrum. The time dependent failure index is obtained under the assumption of filtered Poisson process for the occurrence of critical events. The analysis separates cases where the fluctuation of the metacentric height is narrow-band from those where the bandwidth of the spectrum is wide, with an intermediate blending. In case of narrow-band processes appropriate approximate solutions to the problem are provided, while in the wide-band cases an exponential distribution for the persistence time below the critical level is employed. A rational development for the critical persistence time is also provided considering an approximation of the roll dynamics during periods of time where the metacentric height is negative. Monte Carlo simulations are performed to check the developed approximate distributions for the persistence time, and examples of application are provided for a sample ship.     

A Global Refiability Assessment Method on Aging Offshore Platforms with Corrosion and Cracks

Corrosion and fatigue cracks are major threats to the structural integrity of aging offshore platforms.For the rational estimation of the safety levels of aging platforms,a global reliability assessment approach for aging offshore platforms with corrosion and fatigue cracks is presented in this paper.The base shear capacity is taken as the global ultimate strength of the offshore plaffoms,it is modeled as a random process that decreases with time in the presence of corrosion and fatigue crack propagation.And the corrosion and fatigue crack growth rates in the main members and key joints are modeled as random variables.A simulation method of the extreme wave loads which are applied to the structures of offshore platforms is proposed too.Furthermore,the statistics of global base shear capacity and extreme wave loads are obtained by Monte Carlo simulation method.On the basis of the limit state equation of global failure mode,the instantaneous reliability and time dependent reliability assessment methods are both presented in this paper.Finally the instantaueous reliability index and time dependent failure probability of a jacket platform are estimated with different ages in the demonstration example.     

宁波舟山港主通道混凝土结构耐久性评估与维护技术

系统阐述宁波舟山港主通道跨海工程混凝土结构耐久性评估与维护技术。首先介绍宁波舟山港主通道工程概况及100年使用年限的总体要求;确定耐久性极限状态为海洋氯离子侵入引起的钢筋表面脱钝。针对此极限状态,建立了氯离子侵入过程的耐久性评估模型,确定了不同暴露条件下模型参数的统计规律;根据混凝土保护层厚度的现场实测数据和修正的暴露条件下氯离子扩散系数,对模型参数进行了更新;考虑施工阶段混凝土构件的耐久性附加措施,以某标段非通航孔桥为例,使用全概率方法计算了各类混凝土桥梁构件的失效概率和可靠指标;最终在混凝土构件耐久性评估的基础上,提出了某标段非通航孔桥各类混凝土构件的基本维护制度和维护周期。     

船舶金属腐蚀失效与防护研究

论文对船舶金属腐蚀机理及表现、船舶结构防腐要求等问题做了探讨,对船舶防腐蚀系统进行了分类,分析了腐蚀涂层状况与检验的关系,并对涂层失效的对策和恢复涂层的要求进行了研究。     

渤南油气田海底管道内检测结果分析及评价

运用腐蚀分析的方法, 对渤南油气田海底管道的内检测结果进行了清出物分析、腐蚀规律分析及维修因子分析, 得出了管道的腐蚀规律和安全状况, 并提出了本条海管的运维建议。海底管道内检测结果腐蚀分析方法的应用, 是国内首次将这一办法系统地应用于海底管道内检测结果分析, 对于今后海底管道内检测的结果分析具有开创和借鉴意义。     

三向载荷联合作用下的大型集装箱船结构可靠性研究

大型集装箱船（LCS）具有较大的甲板开口,抗扭刚度非常低。在恶劣海况下航行时,大型集装箱船可能会遭遇斜浪的作用,此时船体将受到三向载荷的联合作用,水平波浪弯矩和扭转波浪弯矩可能会接近甚至超过垂向波浪弯矩,船体可能因发生组合变形而破坏。因此有必要研究大型集装箱船在三向载荷联合作用下的结构可靠性。在研究三向载荷联合作用下各维度极限强度的相互关系的基础上,提出了大型集装箱船的极限承载能力的可靠性评估方法,并对目标船在各浪向角下的结构可靠性进行评估。结果表明：目标船在0°浪向角下的失效概率最高;考虑水平波浪弯矩影响后目标船的结构可靠性有所降低;扭转波浪弯矩对目标船船中剖面的结构可靠性影响较小。     

跨海桥梁船撞风险综合评估

近年来全世界范围内船撞桥事故时常发生,尤其是大型跨海桥梁,对其进行合理的船撞桥风险评估逐渐成为桥梁安全运营的重要保障之一。通过对近年国内外船撞桥案例调研分析,确定了影响事故的多重因素,建立包括4个二级风险评价指标和18个三级指标的层次化评价指标体系,并运用层次分析（AHP）法和熵权法,对各评价指标进行主客观综合赋权,明确各个风险因素对船舶撞击的重要性程度,基于模糊数学理论对船撞桥风险进行多层次综合评判。以浙江省舟山朱家尖跨海大桥为工程背景,结合该桥某年船舶通航统计数据,运用上述方法进行船撞桥风险评估,计算表明朱家尖跨海大桥平均风险评价值为4.22,属于可接受中风险水平,并提出了相应的风险控制对策及措施。     

远洋运输系统人因可靠性定量分析

远洋运输中可能发生的灾害性事故,如船舶碰撞、搁浅、腐蚀疲劳破坏、火灾、爆炸等,大多与人为失误和组织失误（HOE）有关.因此,进行远洋运输系统人因可靠性定量分析,对于运输系统的安全非常重要.针对此问题,文章结合操作风险管理（ORM）技术,对远洋运输系统进行人因可靠性定量分析.为远洋船舶提供了一套预测人为误操作的分析方法,可以降低HOE风险的发生概率,以减小事故的发生.     

Fatigue reliability analysis in time domain for inspection strategy of fixed offshore structures

The paper describes a methodology for estimation of reliability of fixed offshore structures with respect to fatigue and extreme stress. The failure criteria for fatigue are formulated using fracture mechanics principle and that for extreme stress using API Code. Advanced Second Moment method is used to find the reliability index. The total life of the structure is divided into a set of stationary sea-states, occurring during storms and described by directional power spectrum. The method has been illustrated through application to a typical jacket platform. Usefulness of the methodology for planning in-service inspections has been highlighted.     

Time-Variant Reliability Analysis of FPSO Hull Girder Considering Corrosion Based on Statistics

FPSO is a kind of important exploitation platform used in ocean oil and gas industry, which has the unique character of mooring at outsea for a long time. Since it can not be inspected and maintained thoroughly at dock like other kinds of ships, the reliability of FPSO hull girder during the whole service should be focused. Based on latest corrosion database and rational corrosion model, the ultimate strength of one FPSO is calculated under the conditions of slight, moderate and severe corrosion. The results not only provide the reliability under different corrosion conditions, but also do well for further inspection and maintenance research. The results provide necessary foundation for deciding inspection intervals and maintenance measures, which has practical sense to improve the general safety level of ocean engineering.     

高锰铝青铜在流动海水中阴极保护参数的研究

采用稳态动电位极化法测量了螺旋桨材料ZQAl12-8-3-2高锰铝青铜在静态和流动海水中的极化曲线,分析了其在流动海水中的腐蚀电化学行为,解析了最小保护电位、最大保护电位、最小保护电流密度等阴极保护参数,其在海水中的保护电位范围为-0．45～0．72V,最大保护电位在常规阴极保护范围内没有限制,流动海水中的最小保护电流密度比静态时增加几十倍,为海水中螺旋桨阴极保护设计及应用提供参考数据。