靠球减震系统在导管架平台中的应用

导管架生产储油平台在油轮靠泊和外输期间,如遇风浪天气,平台的晃动非常明显,为此引入橡胶靠球减震系统。运用ANSYS有限元分析软件,建立导管架生产储油平台的真实有限元模型,计算平台在靠船碰撞力和波浪力共同作用下平台关键点位置应力变化及振动响应过程,为靠球减震系统在实际工程中应用提供理论依据。     

南海某导管架海洋平台倒塌分析

针对在役老龄导管架平台进行倒塌计算分析,确定极限承载力进而评估老龄导管架的安全裕度。采用非线性有限元方法,考虑平台的波流载荷及桩-土的非线性相互作用,利用SACS软件建立导管架整体三维有限元计算分析模型,并用逐步加载的方式,对南海某导管架平台进行了全过程非线性倒塌分析。计算分析表明,该导管架平台极限强度很高,具有较大的安全裕度;导管架倒塌过程呈逐步破坏形式,先是撑杆屈服,造成局部结构破坏,然后是钢桩发生屈服,降低结构承载力,最后节点逐步失效,造成结构倒塌。揭示了导管架平台结构失效倒塌的机理,给出了倒塌分析的可行方法和步骤。     

基于Archimedean Copula函数的风浪联合统计分析

选取渤海海域某导管架平台24年的年最大波高和相应风速,基于Gumbel分布对2个边缘分布的拟合优度检验,采用Archimedean Copula函数族中的4种函数构建两变量联合概率分布模型,并进行了拟合优度评价。利用优选出的Clayton Copula函数,计算风浪联合分布的联合重现值。以海洋平台响应作为约束条件,进行了二维Clayton Copula函数的风浪联合统计分析。研究结果表明:基于Copula函数构造的二维分布,考虑了风浪之间的相关性,在相同重现值设计参数下,可以降低导管架平台的结构响应,从而可以降低海洋平台的环境条件设计标准。     

柔性气囊助浮法拆除导管架技术研究

文中研究采用柔性气囊助浮法起升导管架的拆除技术。浅水海域浮吊进入困难并且拆除导管架的施工费用昂贵。考虑气囊产生的浮力巨大、价格便宜及连接结构方便的特点,针对即将拆除的QK18-2平台,设计气囊助浮起升导管架的技术方案。考虑水深确定导管架吃水,设计气囊与导管架的连接方式。针对导管架在位起浮状态,计算带有气囊的导管架系统幅频响应RAOs,考虑不同的海洋环境参数,计算分析风浪流作用下导管架系统6个自由度的时域运动响应,文中提出了多点系泊控制导管架运动的合理系泊方式。研究结果表明,气囊助浮法拆除导管架技术具有较高的工程实用价值,针对目标导管架平台设计的气囊助浮拆除技术方案,具有费用低、风险小及不需使用浮吊的技术优势,该项技术可以在导管架平台拆除中推广应用。     

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。     

番禺30-1导管架海洋平台结构振动监测与安全分析

番禺30-1平台是我国首座位于南海海域水深200 m的固定式导管架海洋平台结构,平台结构基频较低,在动载荷作用下平台结构极易发生振动响应,可能对平台结构构件、设备及人员造成一定的安全隐患。现场监测得到的番禺30-1平台结构振动响应统计数据发现,季风期平台结构在波浪作用下发生稳定持续的振动响应,偶然性拖船撞击平台结构桩腿时发生较为强烈的瞬态振动响应。运用有限元数值动力分析方法,结合相关规定对平台结构在波浪及拖船撞击时进行了结构安全性能分析,为平台结构的安全运行及安全保障提供参考价值。     

导管架平台健康监测中的信号处理技术

振动信号处理技术能够提取反映结构健康的特征信息,在导管架平台健康监测中发挥了重要作用。为了给导管架平台健康监测与振动特征提取的发展提供借鉴和指导,文中对导管架平台特征提取中常用的信号处理方法:傅里叶变换、小波变换和希尔伯特-黄(Hilbert-Huang)变换进行了综述,系统总结了它们的基本理论、适用范围、优缺点以及在导管架平台健康监测中的应用情况。文中发现傅里叶变换方法简单、适用性强,对于平稳信号有很好的处理效果;小波变换和希尔伯特-黄变换能很好地提取非平稳信号的时频特性,在导管架平台健康监测与特征提取中应用广泛。同时,随着人工智能算法的快速发展,未来的发展中,可以进行信号处理方法与人工智能算法的结合使用,以期获得更好的信号处理效果。     

考虑隔水导管群桩基作用的导管架平台强度分析方法

本文探讨了导管架平台结构强度分析一种改进方法。在该方法中,考虑了隔水导管群刚度和桩基作用,同时考虑了隔水导管之间以及隔水导管与主桩之间的群桩效应以及上部结构－桩－土相互作用。通过对某六腿导管架平台的分析表明,改进方法可以给出比常规方法更合理的结果。     

不同浪向的波浪载荷作用下导管架平台主桩强度分析

以包括泥面以下桩基在内的所有杆件所构成的桁架式导管架平台为对象,首先通过数值模拟计算组成导管架平台的每一构件的波浪载荷,然后以有限元算法建立包含了平台桩基土反力等因素的导管架整体结构的力学模型,将计算所得波浪载荷施加到该有限元力学模型上,以此通过数值计算手段分析平台中包括泥面以下主桩在内所有杆件的最大应力分布以及桩基的位移特征,从而对平台在特定的波浪环境下的平台主桩的安全性问题进行观察。所提出的方法可为导管架平台在波浪环境下主桩的强度特征分析提供一种实用手段。     

导管架平台拆除过程稳定性及影响因素分析

现有服役海洋平台正逐步走向老龄化,海洋平台拆除成为海洋工程新的经济增长点。针对达到服役年限的导管架平台,基于数值分析方法模拟拆除过程,开展平台在不同拆除阶段和环境载荷等参数下的稳定性及影响规律研究。基于钢结构整体稳定性理论,以导管架平台拆除过程中顶点位移为参考,定义导管架平台拆除作业稳定性指标,提出拆除作业阶段划分方法,通过分析导管架平台在不同影响因素作用下拆除过程稳定性响应,给出拆除作业建议。选取我国南海某4裙12腿进行实例分析,结果表明:主桩腿对导管架平台起决定性承载作用,拆除部分主桩腿后需要引入外部支撑力,以保证拆除作业安全进行;拆除构件越多,来浪方向和环境载荷大小对平台影响越加显著。研究结果可为导管架平台拆除作业提供参考。     

Vibration Characteristics of An Offshore Platform and Its Vibration Control

A template offshore platform, located in the Bohai Bay of China, has exhibited excessive, unexpected vibration un-der mildly hostile sea conditions, which has affected the normal operation of the platform. Since the structure was de-signed to sustain more severe wave climate, the cause of the excessive vibration has been suspected to originate from other sources. The main objectives of this study are to investigate the causes of the excessive vibration, and to explore possible remedies to solve the problem, In this paper, the vibration behavior of the offshore platform is analyzed by means of finite element (FE) modeling, field measurements and laboratory test. Results of analysis suggest that relative movement and impact between the piles and the jacket legs exist, i. e. the piles and the jacket are not perfectly connected. The discon-nection of the piles and jacket weakens the overall stiffness of the platform, and therefore produces unexpected excessive vibration. In this study, measures for reducing     

渤海导管架平台的冰激振动响应分析

为研究渤海海域海冰撞击导管架海洋平台的冰振响应,基于锥体冰力函数,本文建立了渤海海域的冰力作用模型。采用ANSYS有限元软件对导管架平台与海冰的相互作用进行数值模拟,开展了海冰作用下抗冰平台的静力分析及平台动力响应分析。通过与静力分析结果对比,验证了动冰力对结构响应的动力放大效应。在此基础上通过改变冰厚、冰速等海冰参数,研究了不同冰力作用周期下导管架平台的冰振响应。研究表明,海冰厚度及海冰流动速度是影响平台动力响应的主要因素,为导管架平台结构的动力优化设计提供了研究基础。     

Wave-induced vibration control of offshore jacket platforms through SMA dampers

Since permanent wave-induced vibrations of offshore jacket platforms reduce the service life of the jacket structure and deck equipment and increase the fatigue failure of the welded connections, this research has used SMA (shape memory alloy) dampers to control the jacket platform oscillations. Superelasticity, high durability, and energy dissipation capability make SMA elements good nominees for the design of vibration control devices. In this research, to model the force-displacement hysteretic behavior of SMA elements their idealized multi-linear constitutive model has been implemented and the time history responses of vibration equations have been evaluated by direct integration method. To analyze the SMA damper effects on the vibration suppression of the jacket platforms, a 90 (m) high jacket located 80 (m) deep in water has been selected as a case study. Numerical results have shown that optimized SMA dampers with constant-geometry SMA bars will improve the dynamic behavior of the jacket platform under the action of an extreme regular wave. However, under the action of two irregular waves, SMA dampers with varying-geometry SMA bars will cause significant reduction in the dynamic responses of the jacket platform. The power spectral density function of the deck displacements have shown that the previously mentioned SMA dampers avoid resonance by shifting the natural frequencies of the jacket structure away from the excitation frequencies.     

防振锤对深水导管架圆管风致涡激振动抑制研究

研究了阻尼防振锤对深水导管架圆管风致涡激振动的抑制。建立了防振锤动力学模型,分析了防振锤的动力学特性;将在建深水导管架圆管简化为固支梁,建立了结构有限元模型,通过瞬态分析计算了圆管的振动幅值;在圆管中部添加防振锤,分析了防振锤对圆管振动的抑制效果;进行了现场测试,对比了数值模拟和实际测试管道的振动响应。研究表明,文中设计的防振锤可以有效地抑制圆管的涡激共振;数值模拟结果与测试结果非常接近,验证了数值分析方法的有效性。     

Energy Anaiysis for TMD-Structure Systems Subjected to Impact Loading

This paper investigates the characteristics of reduction of the lateral vibration by use of a Tuned Mass Damper (TMD) for offshore jacket platforms under impact loading. Unlike traditional analysis, the present analysis focuses on the energy concept of TMD/structure systems. In this study, a time domain is taken. The platform is modeled as a simplified single-degree-of-freedom (SDOF) system by extraction of the first vibration mode of the structure and the excited force is assumed to be impact loading. The energy dissipation and energy transmission of the structure-TMD system are studied. Finally, an optimized TMD design for the modeled platform is demonstrated based on a new type of cost function - maxi-mum dissipated energy by TMD. Results indicate that TMD control is effective in reducing the Standard deviation of the deck motion but less effective in reducing the maximum response under impact loading.     

Energy Analysis for TMD-Structure Systems Subjected to Impact Loading

This paper investigates the characteristics of reduction of the lateral vibration by use of a Tuned Mass Damper(TMD) for offshore jacket platforms under impact loading. Unlike traditional analysis, the present analysis focnses on theenergy concept of TMD/structure systems. In this study, a time domain is taken. The platform is modeled as a simplifiedsingle-degree-of-freedom (SDOF) system by extraction of the first vibration mode of the structure and the excited force isassumed to be impact loading. The energy dissipation and energy transmission of the structure-TMD system are studied.Finally, an optimized TMD design for the modeled platform is demonstrated based on a new type of cost function - maxi-mum dissipated energy by TMD. Results indicate that TMD control is effective in reducing the standard deviation of thedeck motion but less effective in reducing the maximum response under impact loading.     

Adaptive Predictive Inverse Control of Offshore Jacket Platform Based on Rough Neural Network

The offshore jacket platform is a complex and time-varying nonlinear system,which can be excited of harmful vibration by external loads.It is difficult to obtain an ideal control performance for passive control methods or traditional active control methods based on accurate mathematic model.In this paper,an adaptive inverse control method is proposed on the basis of novel rough neural networks (RNN) to control the harmful vibration of the offshore jacket platform,and the offshore jacket platform model is established by dynamic stiffness matrix (DSM) method.Benefited from the nonlinear processing ability of the neural networks and data interpretation ability of the rough set theory,RNN is utilized to identify the predictive inverse model of the offshore jacket platform system.Then the identified model is used as the adaptive predictive inverse controller to control the harmful vibration caused by wave and wind loads,and to deal with the delay problem caused by signal transmission in the control process.The numerical results show that the constructed novel RNN has advantages such as clear structure,fast training speed and strong error-tolerance ability,and the proposed method based on RNN can effectively control the harmfid vibration of the offshore jacket platform.     

Mitigation of Ice-Induced Vibrations for Offshore Platforms Using Tuned Mass Damper

The problems of ice-induced vibration have been noticed and concerned since the 1960s, but it has not been well resolved. One reason is that the dynamic interaction between ice and structure is so complicated that practical ice force model has not been developed. The recent full-scale tests conducted on jacket platforms in the Bohai Sea presented that ice could cause intense vibrations which endanger the facilities on the deck and make discomfort for the crew. In this paper, the strategy of mitigation of ice-induced offshore structure vibration is discussed. Based on field observations and understanding of the interaction between ice and structure, the absorption mitigation method to suppress ice-induced vibration is presented. The numerical simulations were conducted for a simplified model of platform attached with a Tuned Mass Danlper （TMD） under ice force function and ice force time history. The simulation results show that TMD can fa- vorably reduce ice-induced vibrations, therefore, it can be considered to be an alternative approach to utilize. Finally, the application possibilities of utilizing TMDs on other miniature offshore structures in ice-covered areas of marginal oil fields are discussed.