共查询到20条相似文献,搜索用时 15 毫秒
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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
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A three-dimensional fixed offshore platform in deep water modeled by the finite element method is studied in this paper. Analysis of the dynamic response of the MDOF structure is realized taking the non-linearity of the wave drag force and the wave-structure interaction into account. The structural response statistics, which have Gaussian distributions, are used to evaluate the vibration effect of the structure without TMD and with TMD. And an optimal method to design TMD controlling the first mode of the multi-mode structure is proposed. Moreover, the probabilities of occurrence of sea states at the platform site are considered for prediction of the long-term effect of a TMD. Simulation results demonstrate that the long-term effect of a well-designed TMD is good and the practical use is possible due to the good stability of its optimal parameters under different sea states. 相似文献
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海洋平台磁流变阻尼器半主动控制研究 总被引:1,自引:0,他引:1
基于现代最优控制理论建立海洋平台磁流变 (MR)半主动控制系统的数学模型 ,采用白噪声过程通过滤波器来近似随机波浪力谱。以典型导管架平台为算例 ,对磁流变阻尼器进行了参数设计。分析了 MR阻尼器对海洋平台振动控制的有效性 ,仿真结果表明 ,采用磁流变阻尼器对海洋平台进行半主动控制能够有效的减小平台的动态响应。 相似文献
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An obvious motivation of this paper is to examine the effectiveness of the lateral vibration control of a jacket type offshore platform with an AMD control device, in conjunction with H2 control algorithm, which is an optimal frequency domain control method based on minimization of H2 norm of the system transfer function. In this study, the offshore platform is modeled numerically by use of the finite element method, instead of a lumped mass model. This structural model is later simplified to be single-degree-of-freedom (SDOF) system by extracting the first vibration mode of the structure. The corresponding "generalized" wave force is determined based on an analytical approximation of the first mode shape function, the physical wave loading being calculated from the linearized Morison equation. This approach facilitates the filter design for the generalized force. Furthermore, the present paper also intends to make numerical comparison between H2 active control and the corresponding passive control using a T 相似文献
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Suppression of Wave-Excited Vibration of Offshore Platform by Use of Tuned Liquid Dampers 总被引:3,自引:0,他引:3
This paper describes experimenlal and theoretical investigations of Tuned Liquid Damper (TLD) characteristics tor suppressing the wave-excited structural vibration. The structural model lor the experiments is scaled according to a full size offshore platform by matching their dynamic properties. Rectangular TLDs of different sizes with partially filled liquid are examined. By observing the performance and behavior of TLDs through laboratory experiments, the study investigates the influence of a number of parameters, including container size, container shape, frequency ratio, and incident wave characteristics. In an analytical study, a mathematical model that describes the nonlinear behavior of liquid in TLD and the interaction of TLD and structure is prerequisite. The validity of the model is evaluated and simulating results can reasonably match the corresponding experimental results. 相似文献
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The purpose of this study is to investigate the effectiveness of multi-tuned mass dampers (MTMD) on mitigating vi-bration of an offshore oil platform subjected to ocean wave loading. An optimal design method is used to determine the optimal damper parameters under ocean wave loading. The force on the structure is determined by use of the linearized Morison equation. Investigation on the deck motion with and vvithout MTMD on the structure is made under design condi-tions. The results show that MTMD with the optimized parameters suppress the response of each structural mode. The sensitivity of optimum values of MTMD to characteristic wave parameters is also analyzed. it is indicated that a single TMD on the deck of a platform can have the best performance, and the small the damping value of TMD, the betler the vibration control. 相似文献
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Li Hongnan Ma Baicun
Professor Shenyang Architectural Civil Engineering Institute Shenyang Assistant Engineer Shenyang Architectural Civil Engineering Institute Shenyang 《中国海洋工程》1997,(2)
An approach to seismic response reduction for offshore platforms by the use of the tuned liq-uid damper is presented in this paper.First of all,the effects of the tuned frequency ratio and excited fre-quency ratio on the seismic response reduction of the platform structure are investigated.Based on the re-sults,a mechanical model and equation of motion for the TLD-platform system are established.And theneffectiveness of the appraoch is verified by numerical calculation. 相似文献
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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
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Jin Xianding Sun Renzhang Rrofessor Dept. of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai Engineer Applied Software Development Center of China State Shipbuilding Corp 《中国海洋工程》1994,(1)
-This paper reviews the current methodology for dynamic reanalysis. Rayleigh-Ritz approach and receptance approach are discussed in detail. Based on a general finite element structural analysis program SAPS, an eigenproblem re-analysis prorgram ERP was compiled. With a very small change the program can be implemented readily with any general FEM program. Finally, some numerical examples show that the new algorithm is of high precision and efficiency. In the case of local modification in the offshore platform, the efficiency is raised by 20- 50 times when compared with the re-calculation of the whole model. 相似文献
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Zhao Deting
Senior Engineer China Offshore Oil Development Engineering Corporation Beijing 《中国海洋工程》1995,(4)
Based on some mechanical principles, this paper presents a new way for simplifying the tower structure on the platform, i. e., substituting the three-dimensional tower structure by using beam elements. For the overall analysis of offshore platform, this method can not only save man- power and computer time, but also get better results. This paper introduces the equivalent-simplifying method and its application in engineering. 相似文献
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- 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
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Chu Liangcheng Qu Naisi Guo Yonggang Lu Min Ph.D. Dalian University of Technology Dalian
Associate Professor Dalian University of Technology Dalian
Assistant M.S. Dalian University of Technology Dalian
Engineer Bohai Oil Company Tianjin 《中国海洋工程》1993,(4)
- Theoretically speaking, it is impossible to make the differential equation of motion uncoupled for the natural modes of a system in consideration of the attached water. The hydro-elastic structure is equal to the, non-proportional damping system. In this paper a perturbation analysis method is put forward. The structure motion equation is strictly solved mathematically, and the non-proportional damping problem is transformed into a series of proportional damping ones in the superposition form. The paper also presents the calculation formula of the dyanamic response of the structure being subjected to harmonic and arbitrary load. The convergence of the proposed method is also studied in this paper, and the corresponding convergence conditions are given. Finally, the proposed method is used to analyze the displacement response of a real offshore platform. The calculation results show that this method has the characteristics of high accuracy and fast convergence. 相似文献
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Semi-Active Control of Wave-Induced Vibration for Offshore Platforms by Use of MR Damper 总被引:2,自引:0,他引:2
The objective of the present research is to examine the effectiveness of the lateral vibration control of wave-excited re-sponse of offshore platforms with magnelo-rheological (MR) damper, In this study, the offshore platform is simplified to be a single-degree-of-freedom (SDOF) system by extracting the first vibration mode of the struclure. The exlernal 'generalized' wave force is determined with a white noise via a designed filler. A semi-active control method based on optimal control the-ory is proposed considering that the yield stress of the MR damper can be varied continuously within a certain range. The dy-namics of SDOF structure coupled with the MR damper is investigated. Numerical simulation demonstrates that the MR damper with this control strategy can significantly reduce the maximum responses and the root-mean-square (RMS) values. 相似文献
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Torsional Response of the Offshore Platform with TMD 总被引:1,自引:1,他引:1
JIANG Yicheng 《中国海洋工程》2001,(2):309-314
It is pointed out in this paper that the offshore platform could be controlled by means of the Tuned Mass Damper (TMD) if there is torsional vibration in the system. The effectiveness of the location of TMD is quantified with the help of the response ratio between the peak responses of the system in the presence and in the absence of TMD. In addition, the parameters of frequency and damping ratio of TMD are optimized. 相似文献
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In this paper, the main problems concerning reliability design of offshore platform structure are described and the general steps for the use of Safety Coefficient Method are presented. 相似文献
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The element stiffness matrix of the equivalent beam or pipe element of the deformed leg of the platform is derived by the finite element method. The stresses and displacements of some damaged components are calculated, and the numeri-cal solutions agree well with those obtained by the fine mesh finite element method. Finally, as an application of this method, the stresses of some platform structures are calculated and analyzed. 相似文献