共查询到20条相似文献，搜索用时 15 毫秒
1.
通过对平台在风浪作用下的振动测试分析,发现了直立式非灌浆桩腿导管架平台在海底冲刷条件下发生异常振动的原因是导管架与桩之间存在较大的相对运动,以至于在风浪较大时发生碰撞。因而,结构的动力特性和动态响应都与设计结果不一致。在非极值海况条件下,平台的振动超出了设计预测值,并提出了治理和设计建议。 相似文献
2.
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. 相似文献
3.
Passive control of offshore jacket platforms 总被引：3，自引：0，他引：3
The wave-induced dynamic force is one of the most important excitations to be dealt with in the design of offshore structures. In order to perform a reliable design of an offshore structure, it is important to obtain an exact evaluation of its dynamic response but also to examine the ways of reducing the response. This paper presents the response of offshore jacket platforms installed with energy dissipation devices such as viscoelastic, viscous and friction dampers under wave loading. The offshore jacket platforms are modeled as multi-degrees-of-freedom system provided with dampers at each floor location. The wave forces are modeled as per Morison's equation. The governing equations of motion of the jacket platform with dampers are derived and their solution in the frequency domain is presented. The uni-directional random wave loading is expressed by the Pierson-Muskowitz spectrum. The response of the jacket platform with viscoelastic, viscous and friction dampers is compared with the corresponding response without dampers in order to investigate the effectiveness of the passive control systems. It is observed that the additional dampers add substantial damping to structure and thus favorably control the response of platform structure. Among the various energy dissipation devices used for study, the viscoelastic dampers perform better in comparison to the other dampers. This is due to the fact that the added viscoelastic dampers contribute to increased viscous damping as well as lateral stiffness which reduces the response of the offshore jacket platforms significantly. 相似文献
4.
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. 相似文献
5.
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. 相似文献
6.
In this study, the seismic response control of offshore platform structures with Shape Memory Alloy (SMA) dampers is investigated. A new SMA damper and its restoring force medel are introduced for the calculation of seismic response reduction. Based on an actual platform structure and its mechanical medel, the parameters which may affect the rate of shock absorption are analyzed, such as the number, position and characteristics of the SMA dampers and the condition of the site where the platform is located. The results show that the SMA damper is an effective control device for offshore platforms and satisfactory control can be achieved by proper selection of the parameters. 相似文献
7.
地震与波浪联合作用下海洋平台动力特性分析 总被引：1，自引：0，他引：1
主要针对地震与波浪联合作用下空间导管架式海洋平台结构的动力响应特性进行研究。以春晓平台结构为例,利用ANSYS程序进行了动力响应的数值计算,分析中考虑了地震设防烈度、风浪条件及场地土类型等因素对结构响应的影响,并与地震单独作用下的结构响应进行了对比。分析结果表明,抗震设防烈度较低、中等及较大风浪条件下对海洋平台结构进行抗震分析时有必要考虑地震与波浪的联合作用。 相似文献
8.
迄今为至胜利浅海油田已相继建成大小平台几十座,平台结构型式是导管架式,志管架平台的结构计算理论已基本成熟,现场应力测试是对平台结构设计的验证、补充和发展,但是有关平台的现场应力测试在海洋工程界则是一个空白。本文主要介绍埕北２５Ａ井组平台现场应力测试的方法、结果以及与理论计算的对比。 相似文献
9.
Farhad HOSSEINLOU 《中国海洋工程》2021,(1):96-106
The identification of variations in the dynamic behavior of structures is an important subject in structural integrity assessment.Improvement and servicing of offshore platforms in the marine environment with constant changing,requires understanding the real behavior of these structures to prevent possible failure.In this work,empirical and numerical models of jacket structure are investigated.A test on experimental modal analysis is accomplished to acquire the response of structure and a mathematical model of the jacket structure is also performed.Then,based on the control theory using developed reduction system,the matrices of the platform model is calibrated and updated.The current methodology can be applied to prepare the finite element model to be more adaptable to the empirical model.Calibrated results with the proposed approach in this paper are very close to those of the actual model and also this technique leads to a reduction in the amount of calculations and expenses.The research clearly confirms that the dynamic behavior of fixed marine structures should be designed and assessed considering the calibrated analytical models for the safety of these structures. 相似文献
10.
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. 相似文献
11.
12.
- The ultimate strength analysis of offshore jacket platforms is a research project which has been developed in recent years. With the rapid development of marine oil industry, the departments of design and IMR (Inspection, Maintenance and Repair) in the offshore engineering have attached great importance to this project. The research procedure applies to both the stress check of new design platforms and the whole safety assessment of existing platforms. In this paper, we combine the pseudo non-linear technique with the linear analysis program and successfully analyze the ultimate strength of the space frame structure subject to the concentrated load and a real jacket platform subject to the dead load and environmental load. 相似文献
13.
考虑流固耦合时的海洋平台结构非线性动力分析 总被引：11，自引：0，他引：11
采用非线性的Morison方程,建立了考虑流固耦合时的海洋平台非线性动力方程及其时程分析方法.以一固定式导管架平台为算例,计算了考虑流固耦合时的海洋平台浪致振动响应,比较了考虑流固耦合和不考虑流固耦合时海洋平台动力响应的差异.算例表明：在较大的波浪条件下,不考虑流固耦合时的计算结果明显小于考虑流固耦合时的计算结果,因此,偏于不安全.分析认为,在极端海况条件下,考虑流固耦合的分析方法更符合实际情况. 相似文献
14.
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 相似文献
15.
海洋导管架平台的极限强度分析 总被引：5，自引：1，他引：5
海洋导管架平台的极限分析是一项较新的研究课题，随着海上采油事业的飞速发展，它已越来越受到海洋工程设计及维修部门的重视。其研究成果不仅能用于设计结构的应力校核，尚可用于现有平台结构的整体安全估算。本文利用非线性模拟技术及线性分析程序的完美结合。成功地分析计算了受集中哉茶作用的空间框架结构，及受静载荷和环境载荷作用下的真实导管架平台极限强度。 相似文献
16.
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。 相似文献
17.
The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance. 相似文献
18.
锥体导管架海洋平台冰激振动的DEM-FEM耦合分析及高性能算法 总被引：1，自引：0，他引：1
在寒区海域,冰荷载是影响海洋平台安全运行的主要环境荷载之一,由其引起的冰激振动给平台结构及其上部设备带来了严重危害。为分析不同冰况下平台的振动响应,本文建立了导管架海洋平台冰激振动的离散元（DEM）-有限元（FEM）耦合模型。采用具有黏接-破碎性能的等粒径球体离散单元对海冰的破碎特性进行模拟,通过由梁单元构建的海洋平台有限元模型获得结构的振动响应。在离散元与有限元的接触区域中实现了两个模型间计算参数的传递。为提高该耦合模型的计算效率和规模,发展了基于动力子结构方法的DEM-FEM耦合模型。为验证该耦合模型的有效性和可行性,将不同冰况下得到的冰荷载与ISO19906和JTS 144-1-2010标准进行了对比。结果表明,计算得到的冰荷载与标准相近,且冰厚与冰荷载呈二次非线性关系。同时,从冰速和冰厚两方面对比了渤海四桩腿JZ20-2 MUQ锥体导管架平台冰激振动加速度的数值结果和现场实测数据,发现冰速与振动加速度呈线性关系,冰厚与振动加速度呈二次非线性关系,并且振动加速度与冰速和冰厚平方的乘积呈线性关系。 相似文献
19.
海上风电基础结构动力分析 总被引：1，自引：0，他引：1
针对单桩、三桩、四桩导管架3种常规海上风电基础结构型式动力特性展开研究。以模态分析为基础,获得结构整体固有频率和振型;进而综合运用谐响应分析、瞬态分析、谱分析等方法,对基础结构在简谐荷载、冲击荷载、地震荷载及波浪荷载作用下的动力响应特性进行了数值模拟计算和分析。结果显示:本设计中的单桩、三桩、四桩基础结构刚度依次增大,一阶固有频率递增;对于相同的动力荷载激励,基础结构动力响应递减;基础结构设计中既要保证结构具有足够的刚度以满足荷载作用下的变形控制要求,还要使基础刚度适中以避免共振。为海上风电基础结构动力分析提供了参考。 相似文献
20.
Multiple Tuned Mass Damper Based Vibration Mitigation of Offshore Wind Turbine Considering Soil–Structure Interaction 总被引：1，自引：0，他引：1
The dynamics of jacket supported offshore wind turbine(OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil–structure interaction(SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper(MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology(RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base(without SSI) and flexible base(with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit.Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance. 相似文献