油气爆炸作用下海洋平台抗冲结构研究

海洋平台在服役期间,常会遭受到油气泄露而爆炸引起的冲击破坏.结合歧口QK18-2海洋平台结构,利用非线性瞬态动力学计算软件MSC.Dytran对气体爆炸造成海洋平台结构的损伤机理进行数值仿真研究.在此基础上,详细研究舱室在爆炸载荷下的动态响应,将舱室和爆炸区之间的围壁结构采用增加板厚和改变支撑结构形式、尺寸等四种不同的方式进行比较研究,得出支撑结构对于平台抗冲击的重要性,从而提出有效可行的抗冲结构形式.     

爆炸载荷下海洋平台波纹板防爆结构数值模拟研究

采用非线性瞬态动力学分析软件MSC.Dytran,对泄漏气体的爆炸载荷进行数值计算并与经验公式的计算值作比较。以海洋平台燃油舱围壁为研究对象,对其进行波纹板结构设计,根据波纹高度的不同,将波纹板分为三种:波纹板Ⅰ、波纹板Ⅱ和波纹板Ⅲ。利用MSC.Dytran,对不同波纹板围壁下燃油舱在油气爆炸载荷作用下的变形、能量吸收和加速度等响应进行数值模拟研究。通过对不同波纹板围壁与传统平板围壁的燃油舱动态响应的分析比较发现,燃油舱围壁采用波纹板Ⅰ时防爆效果相对较优。     

海洋平台结构地震响应不确定性因素分析

本文将海洋平台结构的刚度、质量、阻尼以及动水阳力系数C_m,C_d模拟为随机变量,利用随机有限元法,分析了这些参数的变异性引起的海洋平台结构地震响应变异性问题。结果表明,海洋平台结构地震响应的变异性与输入结构参数本身的变异性具有同一量级,动水阻力参数变异性对平台反应的影响比结构参数变异性平台反应的影响稍小。     

火灾作用下海洋平台结构响应分析

结合BZ28-1南井口平台导管架,建立了海洋平台结构有限元计算模型。采用弹塑性分析方法,并应用温度升高时钢材的非线性应力/应变关系,采用火灾的标准温度-时间曲线建立平台结构温度随时间的变化模型,基于能量守恒原理建立热传导微分方程,计算热传导和对流对结构温度的影响,分析得到受火区域构件的温度场。依据钢材性能随温度升高的变化,分析火灾荷载下平台结构的响应。火灾发生时,平台结构中的构件在火温的作用下,温度逐渐升高,虽然作用在结构上的荷载不变,但由于钢材的弹性模量和屈服强度都急剧下降,使平台结构的承载能力下降;当温度上升到600℃以上时,平台结构就形成足够数目的塑性铰,使结构达到极限破坏状态。通过计算分析表明,当火灾作用6 min后,着火房间构件发生严重屈曲,但平台结构整体性能保持良好;当火灾作用22 min后,受火区域构件都发生了较大的变形,引起平台结构的毁损和倾覆。     

油气泄漏灾害下海洋平台风险影响因素研究

海洋平台上存在着大量的风险源,稍有不慎就会引发火灾、爆炸等事故.火灾、爆炸事故不仅会破坏海洋平台的结构承载能力,而且还会造成大量的人员伤亡、严重的财产损失和恶劣的环境污染.采用海洋平台定量风险分析方法,通过DNV风险评估软件,以事件发生的概率、造成的后果两方面为依据,利用事件树方法对影响海洋平台火灾、爆炸风险的因素(油气泄漏概率、不同泄漏方式和人员位置与风险源距离)进行了研究,所得结果对如何降低风险提供了参考依据.     

海洋平台结构动力响应优化设计与灵敏度分析

研究了海洋平台结构动力响应优化设计以结构动力响应的灵敏度计算方法。给出了结构稳态频率响应和瞬态时程响应的灵敏度分析算法，并通过数值试验讨论了瞬态响应灵敏度分析算法的精度和差分法中变量摄动量的影响。在JIFEX软件中实现了结构动力响应灵敏度计算，建立海洋平台结构优化模型和求解方法。数值算例表明了本文方法和程序的有效性。     

大型船舶碰撞引起的海洋导管架平台结构损伤分析

主要对某一海洋导管架平台结构受到大吨位起重铺管船的碰撞进行了详细的非线性数值动力模拟。采用非线性弹簧来模拟受损构件的凹陷特性，计算分析了船舶侧向撞击导管架平台结构在不同的碰撞接触时间下的构件损伤情况，与实际结构损伤的检测结果相比较，反演计算分析了船舶以不同的速度与平台发生碰撞，得到了不同的碰撞接触时间和最大撞击力，以及导管架平台结构主要节点的应力、位移时间历程曲线，可以确定受到撞击后导管架平台结构构件和管节点的损伤程度，对提出合理可行的修理加固方案提供了理论依据。     

海洋平台结构风险评估

作为结构系统可靠性方法与结构损伤冗余设计的一个合理延伸与综合，结构风险评估与决策技术是近年来得到迅速发展的新方法。本文讨论了海洋平台结构风险评估的理论框架，涉及了结构风险评估的几个基本方面，为进一步进行详细研究确立了一条主线。本文还对导管架式平台的结构风险评估进行了简要讨论。     

可燃气体泄漏爆炸下海洋平台数值仿真计算

用等效TNT方法计算了海洋平台复杂结构在油气爆炸冲击波作用下的动态响应,采用MSC.DYTRAN中的多欧拉-拉格朗日耦合方法进行数值模拟研究。用多欧拉域模拟结构内外空气中爆炸冲击波传播情况,用快速耦合方法计算结构和流体的耦合作用。模拟结果显示:在油气爆炸冲击波的作用下,平台舱室变形、失效后破裂,冲击波通过破口传入平台其它舱室;研究了平台各层甲板、舱壁等构件的吸能情况,为平台的结构设计和结构加强打下基础。     

锥体导管架海洋平台冰激结构振动响应分析

渤海冰区油气开发中,在桩腿上安装抗冰锥体的导管架平台是最常见的结构形式.冰激结构振动不仅会造成平台结构的损伤,还将对平台上部管线和设备的安全运行构成极大的威胁,并影响平台作业人员的正常生活和生产操作.针对渤海冰区锥体平台结构冰激振动响应的三种计算方法进行了研究,即平台结构的有限元分析、简化的结构动力分析和冰振响应幅值统计分析.以辽东湾JZ20-2油气田的MUQ平台为例,对以上三种冰振响应计算方法进行对比,以讨论它们的一致性和各自的适用条件.结果表明,这三种分析方法的计算结果基本一致,但有些计算参数需要现场实测资料的确定.     

海洋平台优化设计的研究进展

结构优化是结构设计理论的重要发展,随着“十五”渤海大油田勘探开发战略的实施,结构优化技术将在新型抗冰振平台设计中发挥重要作用。从静力优化设计、动力优化设计、基于可靠度优化设计、全寿命优化设计四个方面论述了海洋平台结构优化设计的研究现状,并展望了海洋平台优化设计的研究前景。     

Summer and winter plankton fish assemblages around offshore oil and gas platforms in south-eastern Australia

Opportunistic plankton surveys were conducted within a 5-nmi radius of nine offshore oil and gas platforms in Bass Strait, south-eastern Australia, in February 1998 and 1999 (summer) and August 1998 (winter). The 108 day-night samples collected alongside (vertical tows) and nearby (surface and oblique tows) platforms yielded 1526 larval and early juvenile fishes representing 55 taxa from 45 families. Epipelagic/mesopelagic taxa dominated the catches, whereas hard/soft habitat-associated taxa were uncommon. Carangidae (36.2%) and Myctophidae (31.5%) dominated in summer and winter, respectively. The most abundant taxon was Trachurus declivis (Carangidae, 35.1%), followed by Bovichtus angustifrons (Bovichtidae, 8.7%), Scomberesox saurus (Scomberesocidae, 3.7%), Centroberyx affinis (Berycidae, 3.0%) and Arripis trutta (Arripidae, 1.7%). Fish concentrations (nos. per 100 m³) alongside platforms did not differ significantly between day and night across all surveys. Likewise, concentrations nearby platforms in February 1999, including those of T. declivis, did not vary significantly by tow type (surface vs. oblique) or day vs. night. The far greater diversity and abundance recorded in February 1999 are likely the result of upwelling conditions over the eastern Bass Strait shelf during the sampling period, and which were not detected in February 1998. In the absence of data on adult fishes associated with the Bass Strait platforms, and given the limited availability of reefs directly around the area, it could be argued that some of the taxa caught may originate from spawning around neighboring natural reefs, particularly those off the Gippsland coastline and the south-east corner of mainland Australia. However, the prime position of the platforms almost right in the center of a productivity “hotspot” would have a confounding effect on the potential source(s) of larval fishes in that region of south-eastern Australia. The role of platforms as potential de-facto reefs for juvenile fishes in Bass Strait, as well as spawning areas, is discussed based on the findings of this study, the first on early stages of fishes around oil and gas platforms in Australia.     

基于实测的导管架海洋平台振动对人员安全评价

目前我国的海洋工程结构中,导管架式海洋平台占有很大比重,动荷载作用下导管架式海洋平台的振动问题日益突出。随着石油开发向深海进军,平台结构柔性更大,振动问题更为显著,可能对结构、设备及人员造成一定的安全隐患。基于现场监测获得的导管架平台振动响应,结合相关规范给出振动对人体的影响,提出人员感受评价流程。最后,以渤海、南海海域的导管架平台为例,基于现场监测,分析了结构的振动特性及作业人员在相应振动环境下的感受。此方法对导管架平台上部作业人员的工作与安全保障提供了科学依据。     

Response-based method for determining the extreme behaviour of floating offshore platforms

The accurate prediction of extreme excursion and mooring force of floating offshore structures due to multi-variete environmental conditions which requires the joint probability analysis of environmental conditions for the worst case situation is still impractical as the processing of large amount of met-ocean data is required. On the other hand, the simplified multiple design criteria (e.g. the N-year wave with associated winds and currents) recommended by API known as traditional method does lead neither to the N-year platform response nor to the N-year mooring force. Therefore, in order to reduce the level of conservatism as well as uncertainties involved in the traditional method the response-based method can be used as a reliable alternative approach. In this paper this method is described. In order to perform the calculations faster using large databases of sea states, Artificial Neural Networks (ANN) is designed and employed. In the paper the response-based method is applied to a 200,000 tdw FPSO and the results are discussed.     

Inverse vibration technique for structural health monitoring of offshore jacket platforms

In this paper a new approach is introduced for structural health monitoring of offshore jacket platforms. The procedure uses the measured ambient vibration responses and the corresponding readable natural frequencies and mode shapes of the structural system. Since offshore platforms are composed of heavy topsides supported by jacket structures, participation of the first mode is dominant in each direction in the response of the structure under field excitations. Moreover, ambient vibrations such as wave loads and boat impacts only excite the first modes of the structure. Therefore, it is difficult to find higher modes and the pertinent frequencies by use of accelerometers data. The introduced innovative method in this research uses the first few fundamental frequencies and mode shapes of the structure. The algorithm employs the inverse vibration technique to develop a simple two and three dimensional reference model for monitoring health of the structure. To show the efficiency of the proposed procedure, a case study is carried out on the models of a jacket-type platform in the Persian Gulf, namely SPD2. Finally, an uncertainty analysis is performed, due to the existence of noises and uncertainties in input data collected by accelerometers. Results indicate that the proposed method has the ability to detect the induced damages by a high level of accuracy considering probable sources of error.     

海洋平台结构形状与拓扑优化设计

以实际环境荷载作用下的实际海洋导管架平台结构为对象，研究了海洋平台结构在风，流，海冰等多荷载模式和多荷载工况下的优化设计的理论方法和应用技术，建立了结构尺寸优化，形状优化和拓扑优化问题的统一模型。计算结果反映出形状优化比尺寸优化所得设计更优，而拓扑优化的设计效果最好。不同的荷载工况对应的最优拓扑形式不同，因此在实际设计中应考虑实际的荷载工况，选取不同的拓扑形式。     

Structural monitoring of offshore platforms using impulse and relaxation response

Monitoring offshore platforms, long span bridges, high rise buildings, TV towers and other similar structures is essential for ensuring their safety in service. Continuous monitoring assumes even greater significance in the case of offshore platforms, which are highly susceptible to damage due to the corrosive environment and the continuous action of waves. Also, since a major part of the structure is under water and covered by marine growth, even a trained diver cannot easily detect damage in the structure. In the present work, vibration criterion is adopted for structural monitoring of jacket platforms. Artificial excitation of these structures is not always practicable and ambient excitation due to wind and waves may not be sufficient for collecting the required vibration data. Alternate methods can be adopted for the same purpose, for example, the application of an impact or a sudden relaxation of an applied force for exciting the structure. For jacket platforms, impact can be applied by gently pushing the structure at the fender while relaxation can be accomplished by pulling the structure and then suddenly releasing it using a tug or a supply vessel in both cases. The present study is an experimental investigation on a laboratory model of a jacket platform, for exploring the feasibility of adapting vibration responses due to impulse and relaxation, for structural monitoring. Effects of damage in six members of the platform as well as changes in deck masses were studied. A finite element model of the structure was used to analyze all the cases for comparison of the results as well as system identification. A data acquisition and analysis procedure for obtaining the response signatures of the platform due to the impulse and relaxation procedure was also developed for possible adoption in on-line monitoring of offshore platforms. From the study, it has been concluded that both impulse and relaxation responses are useful tools for monitoring offshore jacket platforms. The present work forms the basis for the development of an automated, on-line monitoring system for offshore platforms, using neural networks.