Prediction of most probable extreme values for jackup dynamic analysis

Many important technical issues in the design of deep water jackup rigs stem from the prediction of extreme values of global design parameters such as platform sway, base shear, and overturning moment. Several analytical methods primarily based on time-domain dynamic simulation have been recommended in SNAME T&R Bulletin 5–5A (hereafter referred to as “the Bulletin”) in the realm of the so-called most probable maximum extreme. This paper compares the four major dynamic, time-domain methods recommended in the Bulletin, investigates the random seed effect on each method, exams the convergence of the statistical properties within the recommended time simulation, and presents the impact on the dynamic response due to various parameters, e.g. leg-to-hull flexibility, P-delta effect and foundation fixity. Comparison among the four methods is presented in terms of the calculated extreme values and the corresponding dynamic amplification factors. The structural models employed in this investigation were constructed to reflect the behavior of two jackup rigs in service. These rigs were purposely selected to represent two of the most widely used jackup designs, which are of different leg types, different chord types, and designed for different water depth.     

The weldability of steels used in jack-up drilling platforms

Weldability problems in jack-up rigs arise principally in leg construction where particularly high-strength steels (690 N mm⁻² yield) are used for chords and racks. Attainment of mechanical properties is not usually difficult, although procedural trials are advisable.

Of potential fabrication problems, hydrogen cracking (heat-affected zones or weld metal) is of greatest concern, and consideration of solidification cracking is advisable. Lamellar tearing is not generally a problem with modern steels, and the risk of stress-relief cracking will be confined to the limited number of joints which can be heat-treated.

Fatigue cracking is probably the major cause of service failure of jack-up rigs, and the use of high-strength steels, which permits higher static stress limits, can exacerbate this problem. Hydrogen-induced stress corrosion can also occur, either due to cathodic polarisation or corrosion, particularly in the presence of H₂S in foul sea-water. For this reason weld hardness limits need to be maintained.     

Controlled installation of spudcan foundations on loose sand overlying weak clay

Offshore jack-up rigs are often used for site exploration and oil well drilling. The footings of jack-up rigs are known as spudcan foundations. The risk of rapid uncontrolled penetration of spudcan in seabed (“punch-through”) exposes jack-ups to significant risk during installation in strong over weak layered seabeds. An example for this is a thin loose sand layer overlying a weaker stratum of clay. To prevent spudcans from “punch-through”, an in-situ measurement concept is suggested in this paper to control the installation process of spudcan foundations. First, three-dimensional finite element studies using a Coupled Eulerian–Lagrangian method are carried out to simulate the penetration process. The numerical results have been validated with existing analytical solutions and centrifuge model test data. Furthermore, parametric studies are carried out to quantify the influences of the sand thickness and shear strength of the clay on the bearing capacity of spudcans. Based on the numerical studies an idea for the development of an in-situ measurement concept is suggested to control the spudcan penetration process in-situ.     

两种不同系泊系统的风险对比

随着FPSO在海洋石油开发中的广泛应用，以及其系泊技术逐步趋向成熟，各种系泊方式的应用和研究也相对比较深入。对不同系泊方式进行全面风险分析，相互比较，对于以后选择系泊系统形式和避免现有系泊系统的一些风险是非常重要。基于上述考虑，进行散射系泊方式与转塔式系泊方式的风险对比，乃是极其必要的。     

Total oil spill costs and compensations

Although counteracting environmental programmes and policies have been strengthened, large oil spills still occur at irregular intervals. The total oil spill costs and their compensations have attracted much interest from various parties, such as local stakeholders, and state and federal governments. This paper addresses five major cost categories whose aggregations are expected to cover the overall direct and indirect costs after the release of an oil spill. Among them, research costs should not be neglected, since they tend to be high if public attention has been drawn to the case. Through an examination of the relationship between the total oil spill costs and their admissible claims, we found that:

1. admissible claims do not cover the overall costs of the oil spill, and
2. admissible claims cannot be compensated in full in the case of large spills.

Clearly, a sound oil spill contingency management aims to minimize both the environmental impacts of areas most at risk and the total oil spill costs. In this paper an economic model for measuring environmental damages following an oil spill is addressed and applied to the Prestige case which happened to be the worst oil pollution in the history of Spain. The model indicates how an ideally a priori economic evaluation may intuitively help managers to make informed as well as fast decisions in contingency cases.     

船用变频电缆结构分析及敷设

变频设备在船舶、石油平台等设备上的大量使用使得变频器专用电缆的需求越来越大.文章对船用变频电缆的结构设计做了详尽的分析,并探讨了船用变频电缆的敷设安装.     

Evaluation of risk attitude in the shipping freight market under uncertainty

ABSTRACT

The main purpose of this study is to examine how market participants take risks, in other words, what their risk attitude/preference is, and how their risk attitude could be related to the shipping freight and other markets. To address them, we calibrated the risk attitude of participants in shipping freight markets from 2007 to 2013, and provided an example of the application of risk attitude. For market participants, risk attitude/preference has an important role in understanding shipping freight markets and managing risks under uncertainty. However, risk attitude is not directly observable. To achieve this, we applied a framework that consists of structural model and calibration with market data. We interpreted risk attitude and confirmed that a structural break occurred around 2008 for the calibrated risk attitude parameter. The average risk attitude of market participants tended to be more risk-averse after 2010. We conducted an additional analysis to provide an example of the application of calibrated risk attitude, using structural equation modeling to calculate a latent variable that reflected other commodity markets. We compared the risk attitude parameter and the latent variable, and clarified the relationship between the risk attitude parameter and commodity markets.     

Risk assessment framework for exposure of cargo and ports to natural hazards and climate extremes

There is an increase in risks and catastrophic losses in maritime transport including ports and cargo. Significant losses have been associated with large scale natural hazards, such as earthquakes, tsunami, cyclones, and other extreme weather events. This paper identifies the main gaps in understanding maritime risks in transportation research. The gaps are attributed to insufficient empirical work available from the maritime transport and logistics research community to guide multi-risk and natural hazards impact assessment on seaport and cargo. In addition, disaster studies communities have barely made adequate efforts to understand and assess port and cargo risks arising from multi-hazards and disaster events. This paper examines existing conceptual frameworks concerning exposure and risk assessments of natural catastrophe’s impacts. Furthermore, the paper identifies trends and gaps in risk assessment frameworks in the field of disaster studies that can be beneficial for maritime risk research. The authors propose a new risk assessment framework that can guide future research and multi-hazard risk assessment processes at different scales of maritime risks.     

The role of the Classification Societies in the era of globalization: a case study

Although in the great majority of States, the inspection and certification of vessels are provided as public services, the Classification Societies continue being an essential element in maritime traffic, since the official inspections and certifications generally do not take into consideration certain structural aspects or details of vessels. The starting point is an analysis of the role of the Classification Societies on the global and local scale; a case study in a medium-size port of the European Union, the Port of the Bay of Cadiz, is presented. For the case study, an analysis has been made of 507 vessels between the years 2002 and 2008. From the statistical results, it is concluded that there tends to be a direct relationship between the age of the vessel and its classification by a particular type of Society, both with respect to the profiles of risk and to whether the society is a member of the International Association of Classification Societies. The same occurs with respect to the number of days a vessel is detained as a consequence of the Port State Control (PSC) inspections. Similar relationships between Classification Societies and vessels are observed with respect to the flags States, based on featuring in the Black List of the MoU, and with the subclassification of risks.     

2500t沉垫自升式风电安装平台稳性分析探究

带有沉垫的自升式平台是较为特殊的一种平台，而其稳性分析相比常规的桩靴式自升式平台也有所不同。文章研究了一型沉垫自升式风电平台的拖航稳性和沉浮稳性，在破舱稳性计算中增加了对于空舱未设置舱底水系统时的特殊考虑，按照规范对坐底式平台的要求校核其沉浮稳性，并提出平台沉浮过程中重心变化的便捷计算方法，可以为类似平台的稳性计算提供借鉴。     

人为失误与海上事故发生的机理分析

海上事故的发生与航海人员在完成航行任务和处理海上风险过程中的能力有非常密切的关系。保障此过程中的行为能有效地完成成为关键，而航海人员完成任务的能力又直接受到人为失误的影响，也就是说，人为失误的发生直接降低了人的处理能力，使航行任务归于失败。现从行为学的观点对人为失误的发生进行了初步的分析，寻求减少人为失误发生的途径。并从统计学的观点解释了由人为失误引起的海上事故发生的原因。     

基于价值链的中海集运公司风险管理

现代海运业具有"高投资、高风险、高收益"的特点.由于风险众多而分散,传统的企业风险管理模式已难以满足现代航运企业对于风险管理的需求.从系统和集成的角度出发,提出了基于Hines价值链的航运企业风险管理模式,将航运企业面临的风险分为企业内部风险、企业间风险、价值链外部风险等3个层次;针对不同层次的风险宜采取不同的风险处理策略,并特别论述了上述3层次风险之间的关联性.作为案例,对中海集运公司的风险管理实践进行了剖析.结论表明,我国航运企业在企业内部风险管理方面已积累了丰富的经验,并开始重视通过企业间合作来削弱企业间风险的影响,但在价值链外部风险上尚乏举措,在风险管理文化的构建上亦有待深化.     

运用贝叶斯网络对浮台吊装进行基于知识的危险场景概率分析（英文）

Owing to the increase in unprecedented accidents with new root causes in almost all operational areas, the importance of risk management has dramatically risen. Risk assessment, one of the most significant aspects of risk management, has a substantial impact on the system-safety level of organizations, industries, and operations. If the causes of all kinds of failure and the interactions between them are considered, effective risk assessment can be highly accurate. A combination of traditional risk assessment approaches and modern scientific probability methods can help in realizing better quantitative risk assessment methods. Most researchers face the problem of minimal field data with respect to the probability and frequency of each failure. Because of this limitation in the availability of epistemic knowledge, it is important to conduct epistemic estimations by applying the Bayesian theory for identifying plausible outcomes. In this paper, we propose an algorithm and demonstrate its application in a case study for a light-weight lifting operation in the Persian Gulf of Iran. First, we identify potential accident scenarios and present them in an event tree format. Next, excluding human error, we use the event tree to roughly estimate the prior probability of other hazard-promoting factors using a minimal amount of field data. We then use the Success Likelihood Index Method(SLIM) to calculate the probability of human error. On the basis of the proposed event tree, we use the Bayesian network of the provided scenarios to compensate for the lack of data. Finally, we determine the resulting probability of each event based on its evidence in the epistemic estimation format by building on two Bayesian network types: the probability of hazard promotion factors and the Bayesian theory. The study results indicate that despite the lack of available information on the operation of floating objects, a satisfactory result can be achieved using epistemic data.     

Epistemic-based investigation of the probability of hazard scenarios using Bayesian network for the lifting operation of floating objects

Owing to the increase in unprecedented accidents with new root causes in almost all operational areas, the importance of risk management has dramatically risen. Risk assessment, one of the most significant aspects of risk management, has a substantial impact on the system-safety level of organizations, industries, and operations. If the causes of all kinds of failure and the interactions between them are considered, effective risk assessment can be highly accurate. A combination of traditional risk assessment approaches and modern scientific probability methods can help in realizing better quantitative risk assessment methods. Most researchers face the problem of minimal field data with respect to the probability and frequency of each failure. Because of this limitation in the availability of epistemic knowledge, it is important to conduct epistemic estimations by applying the Bayesian theory for identifying plausible outcomes. In this paper, we propose an algorithm and demonstrate its application in a case study for a light-weight lifting operation in the Persian Gulf of Iran. First, we identify potential accident scenarios and present them in an event tree format. Next, excluding human error, we use the event tree to roughly estimate the prior probability of other hazard-promoting factors using a minimal amount of field data. We then use the Success Likelihood Index Method (SLIM) to calculate the probability of human error. On the basis of the proposed event tree, we use the Bayesian network of the provided scenarios to compensate for the lack of data. Finally, we determine the resulting probability of each event based on its evidence in the epistemic estimation format by building on two Bayesian network types: the probability of hazard promotion factors and the Bayesian theory. The study results indicate that despite the lack of available information on the operation of floating objects, a satisfactory result can be achieved using epistemic data.     

Evaluation of political risk in a shipping project

Shipping projects, as land-based ones, are evaluated by using different measures of merit based on discounted cash flows. The bulk carrying industry, where costs are known better than revenues, adopted the required freight rate (RFR) and its derivative the economic cost of transport (ECT) as its major measures of merit. Shipping is a business exposed to many unforeseen risks. Although many of these risks are beyond the control of the shipowners/operators, they should all be carefully weighed during the process of project selection designed for investment decisions. One such risk is the expropriation of shore-based facilities built by the shipping operator at one or more termini of the maritime distribution channel. The operator has to assess the value and probability of risk and translate them into a premium which he will levy on each unit of goods transported. Adding this premium to the required freight rate together with the inventory holding costs and marine insurance charges will produce the real economic cost of transport.     

40自升式钻井平台桩腿加长实践

平台老龄化已成为中海油服钻井装备发展的瓶颈,船龄在30年以上的平台已占现有平台的30%～40%。如何充分发挥这些平台的作业能力,使其在原有设计的基础上,进行重新评估,改造提升其作业能力及适应范围,使其能完成典型区域的作业,已成为重要课题列入装备管理的日程中。本文主要介绍了一国产平台通过论证、计算并对桩腿进行加长,使其在满足作业环境工况及设计规范情况下,适应了作业任务。     

船东风险评估及实证研究

船东风险是造船企业面临的主要风险之一.船东风险持续时间长、发生的后果对造船企业造成的损失大,并且由于受航运市场波动的影响,具有很大的不确定性,因此船东风险评估成为造船企业风险决策的重要依据.在建立船东主要风险体系的基础上,应用模糊层次分析法建立船东风险评估模型,通过调研我国某家厂的国外船东A,应用建立的船东风险评估模型对其进行风险评估,并对该船东的风险进行了分析.基于模糊层次分析的船东风险评估模型,将对船东风险的模糊判断转化成风险数值,以直观的形式将船东风险及影响船东风险内外部特征的评估值呈现出来,为船厂对船东风险分析与接单决策提供技术支持,具有普遍意义.     

The impact of the Polar Code on risk mitigation in Arctic waters: a “toolbox” for underwriters?

The existing risk weighing on vessel, crew and ecosystem in the Arctic and more globally in Polar waters promoted the adoption of the Polar Code (PC) early 2017, a mandatory international legal framework intended for enhanced safety and environmental protection. While the substance of the PC has been extensively analyzed, few studies have focused on the underlying relationships between the PC and underwriters. Based on an extensive literature review, documentary materials and interviews with insurance companies, this article conceptualizes the PC as a “toolbox” and analyzes how underwriters can exploit it in their work within the emerging Arctic market. The PC does not only regulate the navigation in Arctic waters in legal terms, but is also aimed at mitigating risks in the Polar areas through the identification of hazard sources and proceduralization of risk assessment. As a result we observe a certain “Polar Code paradox”. Even though the PC is a risk-based instrument and constitutes a key step for improving ship insurability, it has only limited capacity to assist underwriters in assessing risks and insuring vessels. Marine insurers still face a lack of data and high pending uncertainties leading them to exercise extreme caution with Arctic risks appraisal.     

Shipping freight derivatives: a survey of recent evidence

In an industry that is characterized by highly volatile prices, seasonality, strong business cycles, cyclicality and capital intensiveness, risk management is extremely important. Ship-owners and charterers face enormous risks, which emanate from fluctuations in freight rates, bunker prices, interest rates, foreign exchange rates and vessel values. These risks substantially affect the interplay between revenue and cost. Modern risk management techniques, involve the use of financial derivatives products, some of which have been developed exclusively for protecting (hedging) against the adverse price fluctuations of the aforementioned sources of risk in shipping. By using derivatives products, ship-owners and charterers can secure (stabilize) the level of their future income or costs and thus reduce uncertainty and unforeseen volatility of their cash-flow. To explore the importance of hedging freight rate risk in shipping operations, a survey of recent empirical evidence that has appeared in economic studies has been conducted. Developments over the past 20 years have been fast, with certain amount of research carried, which has helped to understand better the special features of these derivatives markets. They are all summarized in the current study, which can provide the stepping stone for further work in the area of shipping derivatives and risk management in shipping.     

Shipping freight derivatives: a survey of recent evidence

In an industry that is characterized by highly volatile prices, seasonality, strong business cycles, cyclicality and capital intensiveness, risk management is extremely important. Ship-owners and charterers face enormous risks, which emanate from fluctuations in freight rates, bunker prices, interest rates, foreign exchange rates and vessel values. These risks substantially affect the interplay between revenue and cost. Modern risk management techniques, involve the use of financial derivatives products, some of which have been developed exclusively for protecting (hedging) against the adverse price fluctuations of the aforementioned sources of risk in shipping. By using derivatives products, ship-owners and charterers can secure (stabilize) the level of their future income or costs and thus reduce uncertainty and unforeseen volatility of their cash-flow. To explore the importance of hedging freight rate risk in shipping operations, a survey of recent empirical evidence that has appeared in economic studies has been conducted. Developments over the past 20 years have been fast, with certain amount of research carried, which has helped to understand better the special features of these derivatives markets. They are all summarized in the current study, which can provide the stepping stone for further work in the area of shipping derivatives and risk management in shipping.