共查询到19条相似文献，搜索用时 94 毫秒
1.
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
2.
Cao Guoao Shen Yilei
Dr.Professor Tongji University Shanghai
Shanghai College of Architectural Municipal Engineering Shanghai 《中国海洋工程》1991,(1)
In this paper, the responses of the interaction system of R.C. gravity single-leg platform to seismic excitation are mainly analysed. A set of nonlinear equations for the interaction system are established by using the wave, one is the soil-structure interaction and the other is the fluid-structure interaction. The seismic response of the interaction system is analysed for the influence of the asymmetric structure, fluid action, etc. with the input of seismic SH waves in any direction. The numerical results are given for a simple example. 相似文献
3.
In the present study, the dynamic response of a coupled SPM-feeder-cage system under irregular waves and shear currents is analyzed. A numerical model is developed by using the commercial software Orca Flex. Hydrodynamics coefficients of the vessel are calculated by using a 3D diffraction/radiation panel program. First- and second-order wave forces are included in the calculations. Morison equation is used to compute the drag force on line elements representing the net. Drag coefficients are determined at every time step in the simulation considering the relative normal velocity between the structural elements and the fluid flow. The dynamic response of the coupled system is analyzed for various environments and net materials. The results of the study show the effects of solidity ratio of the net and vertical positions of the cage on the overall dynamic response of the system, confirming the viability of this type of configuration for future development of offshore aquaculture in deep waters. 相似文献
4.
《中国海洋工程》2020,(4)
This paper presents a numerical study on the high-frequency wave loads and ringing response of offshore wind turbine foundations exposed to moderately steep transient water waves. Input wave groups are generated by the technique of frequency-focusing, and the numerical simulation of focused waves is based on the NewWave model and a Fourier time-stepping procedure. The proposed model is validated by comparison with the published laboratory data. In respect of both the wave elevations and the underlying water particle kinematics, the numerical results are in excellent agreement with the experimental data. Furthermore, the local evolution of power spectra and the transfer of energy into higher frequencies can be clearly identified. Then the generalized FNV theory and Rainey's model are applied respectively to calculate the nonlinear wave loads on a bottom-hinged vertical cylinder in focused waves.Resonant ringing response excited by the nonlinear high-frequency wave loads is found in the numerical simulation when frequency ratios(natural frequency of the structure to peak frequency of wave spectra) are equal to 3–5.Dynamic amplification factor of ringing response is also investigated for different dynamic properties(natural frequency and damping ratio) of the structure. 相似文献
5.
A model based on the data from forced vibration experiments is developed for predicting the vortex-induced vibrations (VIV) of elastically mounted circular cylinders in flow. The assumptions for free and forced vibration tests are explored briefly. Energy equilibrium is taken into account to set up the relationship between the dynamic response of self-excited oscillations and the force coefficients from forced vibration experiments. The gap between these two cases is bridged straightforwardly with careful treatment of key parameters. Given reduced mass m and material damping ratio ζ of an elastically mounted circular cylinder in flow, the response characteristics such as amplitude, frequency, lock-in range, added mass coefficient, cross-flow fluid force and the corresponding phase angle can be predicted all at once. Instances with different combination of reduced mass and material damping ratio are compared to investigate their effects on VIV. The hysteresis phenomenon can be interpreted reasonably. The predictions and the results from recent experiments carried out by Williamson's group are in rather good agreement. 相似文献
6.
In this paper, the control performance is investigated of Circular Tuned Liquid Column Dampers (CTLCD) over torsional response of offshore platform structures excited by ground motions. Based on the equation of motion for the CTLCD-structure system, the optimal control parameters of CTLCD are given through some derivations on the supposition that the ground motion is a stochastic process. The influence of systematic parameters on the equivalent damping ratio of the structures is analyzed with purely torsional vibration and translational-torsional coupled vibration, respectively, The results show that the Circular Tuned Liquid Column Damper (CTLCD) is an effective torsional response control device. 相似文献
7.
Zhang Huaishui 《海洋学报(英文版)》1991,10(2):229-236
In this paper, the discussion is made on the problem of the oceanic response caused by air-sea interaction under storm. First, the perturbation differential equations for the problem are given, and the interaction functions are supposed to be the solving conditions. Next, the nonlinear diffusion equations of the problem are solved by using the method of the given variable transforms and the specific variable power series. Finally, the response disturbances to the circular intense storm is calculated so as to discribe quantitatively the evolution processes of the oceanic response. 相似文献
8.
This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dimensional coupled fluid-structure-soil finite element modelling is employed to obtain the quay-wall response. The seawater medium is represented by acoustic type, potential based fluid elements. The elasto-plastic behavior of the soil medium is idealized using Drucker-Prager yield criterion based on associated flow rule assumption. Four nodded plane strain elements are used to model the concrete wall, foundation, subsoil, backfill and seabed zones. Fluid Structure Interface (FSI) elements are considered between the seawater interfaces with the quay-wall and the seabed. Frictional contact elements are employed between the wall and soil interfaces. The numerical model is validated using field measurements available for permanent drifts in a quay-wall damaged during Kobe earthquake. Reasonable agreements are obtained between the model predictions and the field measurements. Non-linear seismic analyses of the selected quay-wall subjected to both near-fault and far-fault ground motions are performed. An incremental dynamic analysis approach (IDA) is used. In general, at least for models examined in the current study, the gravity quay-walls are found to be more vulnerable to near-field, in comparison with the corresponding far-field, earthquakes. 相似文献
9.
Feedback and Feedforward Optimal Control for Offshore Jacket Platforms 总被引：18，自引：0，他引：18
The optimal control is investigated for linear systems affected by external harmonic disturbance and applied to vibration control systems of offshore steel jacket platforms. The wave-induced force is the dominant load that offshore structures are subjected to, and it can be taken as harmonic excitation for the system. The iineafized Morison equation is employed to estimate the wave loading. The main result concerns the existence and design of a realizable optimal regulator, which is proposed to damp the forced oscillation in an optimal fashion. For demonstration of the effectiveness of the control scheme, the platform performance is investigated for different wave states. The simulations axe based on the tuned mass damper (TMD) and the active mass damper (AMD) control devices. It is demonstrated that the control scheme is useful in reducing the displacement response of jacket-type offshore platforms. 相似文献
10.
Seismic load has a significant effect on the response of a free spanning submarine pipeline when the pipeline is con-structed in a seismically active region. The model experiment is performed on an underwater shaking tahle to simulate the response of submarine pipelines under dynamic input. In consideration of the effects of the terrestrial and submarine pipeline , water depth, support condition, distance from seabed, empty and full pipeline, and span on dynamic response, 120 groups of experiments are conducted. Affecting factors are analyzed and conclusions are drawn for reference. For the con-trol of dynamic response, the span of a submarine pipeline is by far more important than the other factors. Meanwhile, the rosponse difference between a submarine pipeline under sine excitation and that under random excitation exists in ex-periments. 相似文献
11.
固定式海洋平台利用TLD的减震研究 总被引：7，自引：0，他引：7
本文研究固定式海洋平台利用调谐液体阻尼器（ＴｕｎｅｄＬｉｑｕｉｄＤａｍｐｅｒ，简称ＴＬＤ）减小地震反应的方法。首先探讨了调谐频率比、激磁频率比对减震效果的影响，在此基础上建立了ＴＬＤ——平台系统的力学模型和运动方程，通过数值计算验证了该方法的有效性 相似文献
12.
海洋石油平台TMD振动控制及参数优化 总被引：2，自引：1，他引：1
研究了随机波浪载荷作用下调谐质量阻尼器（ＴＭＤ）对桩基钢结构海洋平台的减振效果,采用谱分析法对ＴＭＤ参数进行优化,优化ＴＭＤ 使平台的位移响应标准偏差比无ＴＭＤ下降１２．４％ 。并研究了ＴＭＤ参数在优化域内的失调对响应的影响,ＴＭＤ刚度失调比阻尼失调要敏感,欠阻尼失调比过阻尼失调要敏感。从振害累积概念出发,对谐激励下ＳＤＯＦ－ ＴＭＤ的Ｒａｎｄａｌｌ参数优化方法提出了改进。 相似文献
13.
Mjelde Rolf Fjellanger Jan Petter Digranes Per Kodaira Shuichi Shimamura Hideki Shiobara Hajime 《Marine Geophysical Researches》1997,19(1):81-96
A 140 km long wide-angle seismic profile has been acquired by use of 6 Ocean Bottom Seismographs across the Jan Mayen Ridge, North Atlantic. The profile was acquired twice; once with a traditionally tuned standard source and secondly with a somewhat smaller source tuned on the first bubble pulse. Analysis of the frequency content of the data reveals that the single-bubble source within the 10-15 Hz frequency range generates a signal with a level about 5 db above that of the standard source. These differences can partly be related to differences in airgun depth. The higher output level for these frequencies enables the single-bubble source to resolve intra-crustal structures with a higher degree of certainty, when compared to the data acquired by use of the standard source array. The standard source seems to generate slightly more energy for frequencies around 6 Hz, probably due to the use of a large 1200 in/sup3 gun in this array. These low frequencies a re of importance for mapping of lower crustal and upper mantle structures, and it is recommended that this is taken into account when seismic sources for mapping of deep crustal and upper mantle structures are designed. 相似文献
14.
常规的基于叠后地震资料的地层Q值补偿方法受数据平均效应的影响,Q值估算精度较低,导致保真性差,而HHT时频分析可以反映出信号的局部信息,基于以上原因,提出一种基于HHT方法的地层Q值补偿方法。首先应用HHT分频技术将浅层、中深层地震数据分成不同的频率范围,得到不同目标层频率尺度的地震数据;然后在HHT时频域内通过谱比法提取Q值;最后分别进行地层Q值振幅补偿和相位补偿。该方法针对不同的目标地层将地震数据分解成不同的频率尺度,避免了不同频率成分之间的干扰,而且可针对性处理目标层的频率信息,提高了地层Q值提取的稳定性。模型试算和实际资料应用表明,该方法能够有效地对振幅和相位进行补偿,使中深层反射波形得到恢复,主频提高,频带展宽,地震资料的品质得到提升。 相似文献
15.
16.
The measurement of the signal to noise ratio in continuous seismic profiling systems is carried out by means of a small general purpose digital computer equipped with an analog to digital converter. The computer is programmed to compute and compare the power spectrum of a sample of noise to the power spectrum of a sample of noise plus an echo. Power spectra of some twenty to fifty shots are averaged to yield reliable estimates of the signal to noise ratio as a function of frequency. The observed spectra agree well with spectra calculated from signals measured near to an air-gun. This measurement of signal to noise ratio as a function of frequency provides unambiguous information for the adjustment of the necessary band-pass filter thus improving the operation of a continuous seismic profiler. 相似文献
17.
海上单道地震与浅地层剖面数据海浪改正处理研究 总被引：2，自引：1，他引：1
因受海面大风浪与涌浪等影响,海上单道地震与浅地层剖面数据反射同相轴常出现波浪状起伏,造成剖面反射层位错乱,分辨率与信噪比降低。根据海浪噪声与海底反射地层在横向上的相关性与变化频率等特性,以及综合前人的研究成果,采用陆上地震数据剩余静校正处理中的统计模型道互相关方法来实现对剖面反射同相轴的海浪改正处理;为减少强能量噪声对相关运算的影响,采用中值滤波、光滑滤波技术对反射同相轴曲线进行滤波处理,以进一步减少残留海浪的影响及相关运算改正误差。将这些方法综合运用于海上实际调查资料处理后,大风浪与涌浪影响下的波浪状反射同相轴变得连续、光滑,海底下混乱模糊的反射层位变得清晰、连续,剖面信噪比与分辨率得到了极大的提高。 相似文献
18.
V. A. Lazarev A. I. Malekhanov L. R. Merklin V. I. Romanova V. I. Talanov A. I. Khil’ko 《Oceanology》2013,53(6):755-761
Experimental results of the seismic profiling with bottom penetration up to 1000 m based on broadband signals and conducted in the Caspian Sea sites are presented. Use has been made of synchronized sequences of probing pulses with linear frequency modulation at a frequency deviation of 50 to100 Hz. The pulses were emitted by a towed sound source of an original design (acoustic power up to 300 W, frequency ranged from 100 to 1000 Hz) and received by a standard digital seismic streamer. The processing of the signals involved the matched filtering of the individual pulses and the trajectory accumulation of a long sequence of pulses lengthwise the horizontal-homogeneous reflecting layers of the bottom structure. The adaptive stacking procedure taking into account the linear inclinations of the individual layers allowed us to enlarge the stacking interval by up to 100 pulses and to increase the effective depth and the spatial resolution of the seismic profiling, which gave us a total increase of more than 30 dB in the S/N ratio. In our view, the seismic profiling using low-power (about 100 W) and broadband (up to several hundred Hz) coherent sound sources represents a promising technology for decreasing the hazardous impact on aquatic ecosystems. The approach developed is an alternative to the conventional technology of marine seismic prospecting based on powerful pulse sources of the shock type (air guns, sparkers) in the low frequency range (less than ～200 Hz). 相似文献
19.
The worldwide demand for renewable energy is increasing rapidly. Wind energy appears as a good solution to copy with the energy shortage situation. In recent years, offshore wind energy has become an attractive option due to the increasing development of the multitudinous offshore wind turbines. Because of the unstable vibration for the barge-type offshore wind turbine in various maritime conditions, an ameliorative method incorporating a tuned mass damper (TMD) in offshore wind turbine platform is proposed to demonstrate the improvement of the structural dynamic performance in this investigation. The Lagrange's equations are applied to establish a limited degree-of-freedom (DOF) mathematical model for the barge-type offshore wind turbine. The objective function is defined as the suppression rate of the standard deviation for the tower top deflection due to the fact that the tower top deflection is essential to the tower bottom fatigue loads, then frequency tuning method and genetic algorithm (GA) are employed respectively to obtain the globally optimum TMD design parameters using this objective function. Numerical simulations based on FAST have been carried out in typical load cases in order to evaluate the effect of the passive control system. The need to prevent the platform mass increasing obviously has become apparent due to the installation of a heavy TMD in the barge-type platform. In this case, partial ballast is substituted for the equal mass of the tuned mass damper, and then the vibration mitigation is simulated in five typical load cases. The results show that the passive control can improve the dynamic responses of the barge-type wind turbine by placing a TMD in the floating platform. Through replacing partial ballast with a uniform mass of the tuned mass damper, a significant reduction of the dynamic response is also observed in simulation results for the barge-type floating structure. 相似文献