崖城13-1气田海底输气管线带压回收修复方案设计及作业实践

针对崖城13-1气田服役20年的海底输气管线出现泄漏和阀组保护罩侧翻但必须采用带压修复的现状,根据现场危险性气体封堵情况设计了海管带压修复方案,并对带压回收修复海底管线进行了疲劳损伤分析,给出了疲劳许用值,以此指导修复期间作业线的疲劳时间控制措施;提出了带压回收修复老海底管线期间的危险性气体检测方法及应急方案,保证了带压回收修复的正常进行及作业人员、船舶的安全。本次老海底管线带压回收修复技术填补了国内相关领域的空白,为海底管线维抢修技术的发展奠定了坚实基础。

Subsea rigid jumper design and VIV fatigue evaluation

The purpose of this paper is to present a design procedure for subsea rigid jumper system including strength and fatigue analysis. Special attention gives to a methodology based on DNV-RP-F105 to evaluate jumper fatigue damage caused by vortex induced vibration (VIV). Jumper strength analysis is to determine the jumper con-figuration which can accommodate various load conditions and all possible span lengths driven by installation tole-rances of connected subsea structures. Fatigue analysis includes two parts:thermal fatigue and VIV fatigue. This paper presents the procedure of VIV fatigue damage calculation. An example is given to illustrate above methodologies.

Probabilistic Analysis and Fatigue Damage Assessment of Offshore Mooring System due to Non-Gaussian Bimodal Tension Processes

Both wave-frequency(WF) and low-frequency(LF) components of mooring tension are in principle non-Gaussian due to nonlinearities in the dynamic system.This paper conducts a comprehensive investigation of applicable probability density functions(PDFs) of mooring tension amplitudes used to assess mooring-line fatigue damage via the spectral method.Short-term statistical characteristics of mooring-line tension responses are firstly investigated,in which the discrepancy arising from Gaussian approximation is revealed by comparing kurtosis and skewness coefficients.Several distribution functions based on present analytical spectral methods are selected to express the statistical distribution of the mooring-line tension amplitudes.Results indicate that the Gamma-type distribution and a linear combination of Dirlik and Tovo-Benasciutti formulas are suitable for separate WF and LF mooring tension components.A novel parametric method based on nonlinear transformations and stochastic optimization is then proposed to increase the effectiveness of mooring-line fatigue assessment due to non-Gaussian bimodal tension responses.Using time domain simulation as a benchmark,its accuracy is further validated using a numerical case study of a moored semi-submersible platform.

Fatigue analysis of the bow structure of FPSO

The bow structure of FPSO moored by the single mooring system is rather complicated. There are many potential hot spots in connection parts of structures between the mooring support frame and the forecastle. Mooring forces, which are induced by wave excitation and transferred by the YOKE and the mooring support frame, may cause fatigue damage to the bow structure. Different from direct wave-in duced-forces, the mooring force consists of wave frequency force (WF) and 2nd dr aft low frequency force (LF) [3] , which are represented by two sets of short-term distribution respectively. Based on two sets of short-term distribution of moor ing forces obtained by the model test, the fatigue damage of the bow structure of FPSO is analyzed, with emphasis on two points. One is the procedure and position selection for fatigue check, and the other is the application of new formulae for the calculation of accumulative fatigue damage caused by two sets of short-term distribution of hot spot stress range. From the results distingui shed features of fatigue damage to the FPSO’s bow structure can be observed.

AFC （AREVA Fatigue Concept）-An Integrated and Multi-disciplinary Approach to the Fatigue Assessment of NPP Components

The prevention of fatigue damages is a crucial issue for NPPs （nuclear power plants）. The AFC （AR.EVA fatigue concept） provides for a multi-step and mnlti-disciplinary process against fatigue during the design and operating phase of NPPs. The entire process of fatigne design is based on an installed FAMOS （fatigue monitoring system）. In this way, realistic load data are available to manage the component ageing and enable the optimization of operating modes. The measured temperatures are processed via a FFE （fast fatigue evaluation）. Thus, an online fatigue evaluation of the cumulative usage factor is performed after every operational cycle. This procedure gives a first fatigue status of the power plant. Furthermore, a DFC （detailed fatigue calculation） conforming to the code rules is carried out in order to determine the state of the plant at the highest loaded positions. These finite element analyses include determination of thermal transient and subsequent stresses and strains. Fatigue environmental factors are taken into account in these studies.

Electroacupuncture at Houxi(SI 3) for acute lumbar sprain: a meta-analysis of randomized controlled trials

Objective： To assess the efficacy and safety of electroacupuncture （EA） at Houxi （SI 3） in treating acute lumbar sprain. Methods： Randomized controlled trials （RCTs） involving EA at Houxi （SI 3） for acute lumbar sprain were retrieved from PubMed （1966-2014）, EMBASE （1980-2014）, Cochrane Library （Issue 1, 2014）, CO, VIP Database （1989-2014）, Wanfang Digital Journal （1998-2014）, the Chinese Biological Medical Literature Database （CBM, 1978-2014）, and China National Knowledge Internet （CNKI, 1979-2014）. The collection of data also adopted hand-search of the relevant journals from the Library of Shanghai Jiao Tong University. All of the data were first evaluated and extracted by two reviewers independently with a specially designed form. Then, the available data were analyzed by the Cochrane Collaboration＇s RevMan 5.2.0 software. Results： A total of 6 trials involving 1 288 patients were eligible. Meta-analysis showed that the total effectiveness rate in the EA group was significantly different when compared with Nimesulide [RR----1.33; 95% CI （1.19 to 1.49）] and Mobic [RR= 1.08; 95% Cl （1.03 to 1.14）], but similar to that of acupuncture at Yaotongdian （EX-UE 7） [RR=71.09; 95% Cl （1.00 to 1.19）] and Diclofenac Sodium [RR----1.08; （95% CI 0.96 to 1.21）]. The recovery rate in the EA group was significantly different when compared with Mobic [RR----1.67; （95% CI 1.45 to 1.92）] and Nimesulid [RR：1.37; （95% Cl 1.15 to 1.62）], but similar to that of acupuncture at Yaotongdian [（RR=1.35; 95% CI 0.99 to 1.84）] and Diclofenac Sodium [（RR=I.19; 95% Cl 0.88 to 1.61）]. Conclusion： Up to the search date, there are few high quality RCTs to evaluate the clinical efficacy of EA at Houxi （SI 3） for acute lumbar sprain, especially studies in English. Yet EA at Houxi （SI 3） still appeared to be an efficacious method for acute lumbar sprain, despite several inherent defects of the included studies. Further large scale trials are required to define the role of EA at Houxi （SI 3） in the treatment of this disease.