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961.
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
962.
963.
利用均震法判别扩腰桩桩身的完整性 总被引:1,自引:0,他引:1
本文阐述了均震动测法检测扩腰桩的方法及原理 ,分析了扩腰模型及工程实例 ,总结了不同质量扩腰桩的波形特征 ,为判别扩腰桩桩身的完整性提供了新思路。 相似文献
964.
利用TLD减小高柔结构多振型地震反应的研究 总被引:13,自引:2,他引:11
本文提出了利多多个调谐液体阻尼器(简称TLDS)减小高柔结构多振型地震反应的方法,给出了TLD的布置方案和计算公式,通过钢框架模拟地震振动台试验和理论分析,验证了本文提出的方法的正确性. 相似文献
965.
振动沉管中的一种“反常现象”的处理及原因分析 总被引:1,自引:0,他引:1
就振动沉管工程实践中处理过的一种“反常现象” ,从理论上作一探讨。意在抛砖引玉 ,希望能引起有关专家、地基设计人员及有关施工人员承接工程时参考。 相似文献
966.
利用加速度记录分析P波质点的受力状态、P波质点随机震动的概率分布及其偏振现象,结果显示,P波质点随机震动的受力矢量服从三维高斯分布,其概率密度呈椭球状分布,可通过加速度记录的协方差矩阵求出偏振椭球的几何参数,从而求出震中方位角. 相似文献
967.
Unlike most previous studies on the transverse vortex-induced vibration(VIV) of a cylinder mainly under the wallfree condition (Williamson & Govardhan,2004),this paper experimentally investigates the vortex-induced vibration of a cylinder with two degrees of freedom near a rigid wall exposed to steady flow.The amplitude and frequency responses of the cylinder are discussed.The lee wake flow patterns of the cylinder undergoing VIV were visualized by employing the hydrogen bubble technique.The effects of the gap-to-diameter ratio (e0/D) and the mass ratio on the vibration amplitude and frequency are analyzed.Comparisons of VIV response of the cylinder are made between one degree (only transverse) and two degrees of freedom (streamwise and transverse) and those between the present study and previous ones.The experimental observation indicates that there are two types of streamwise vibration,i.e.the first streamwise vibration (FSV) with small amplitude and the second streamwise vibration (SSV) which coexists with transverse vibration.The vortex shedding pattem for the FSV is approximately symmetric and that for the SSV is alternate.The first streamwise vibration tends to disappear with the decrease of e0/D.For the case of large gap-to-diameter ratios (e.g.e0/D = 0.54~1.58),the maximum amplitudes of the second streamwise vibration and transverse one increase with the increasing gapto-diameter ratio.But for the case of small gap-to-diameter ratios (e.g.e0/D = 0.16,0.23),the vibration amplitude of the cylinder increases slowly at the initial stage (i.e.at small reduced velocity V,),and across the maximum amplitude it decreases quickly at the last stage (i.e.at large Vr).Within the range ofthe examined small mass ratio (m<4),both streamwise and transverse vibration amplitude of the cylinder decrease with the increase of mass ratio for the fixed value of V,.The vibration range (in terms of Vr ) tends to widen with the decrease of the mass ratio.In the second streamwise vibration region,the vibration frequency of the cylinder with a small mass ratio (e.g.mx = 1.44) undergoes a jump at a certain Vr,.The maximum amplitudes of the transverse vibration for two-degree-of-freedom case is larger than that for one-degree-of-freedom case,but the transverse vibration frequency of the cylinder with two degrees of freedom is lower than that with one degree of freedom (transverse). 相似文献
968.
Numerical Simulation of Self-Excited and Forced Vibration of Circular Cylinders in Current 总被引:1,自引:0,他引:1
Numerical simulations of a low-mass-damping circular cylinder which can oscillate freely at transverse and streamwise directions are presented in this work.The Navier-Stokes equations are solved with finite volume method,and large eddy simulation of vortex is also performed in the calculation.In order to implement dynamic mesh,overlapping grids are generated to lessen the computation for mesh field itself.Self-excited vibrations are firstly calculated to obtain the average amplitudes and frequencies of the target circular cylinder in the current flow situation,and then forced oscillations are implemented with parameters obtained in vortex-induced vibrations previously.With slight amplitude modulation,time series of displacements in vortex-induced vibrations are essentially harmonic.Regarding the fluid force,which are larger in forced oscillations than those in corresponding self-excited cases because the fluid subtracts energy from the forced cylinders.The phase angles between forces and displacements are 0° and 180° for self-excited case and forced case respectively.In vortex-induced vibrations,the interactions between fluid and structure produce some weakly energetic vortices which induce the modulations of amplitude and frequency. 相似文献
969.
Based on similarity analyses, a series of experiments have been conducted with a newly established hydro-elastic facility to investigate the transverse vortex-induced vibrations (VIVs) of a submarine pipeline near an erodible sandy seabed under the influence of ocean currents. Typical characteristics of coupling processes between pipe vibration and soil scour in the currents have been summarized for Case I: pipe is laid above seabed and Case II: pipe is partially embedded in seabed on the basis of the experimental observations. Pipe vibration and the corresponding local scour are usually two coupled physical processes leading to an equilibrium state. The influence of initial gap-to-diameter ratio (e0/D) on the interaction between pipe vibration and local scour has been studied. Experimental results show that the critical values of Vr for the initiation of VIVs of the pipe near an erodible sand bed get bigger with decreasing initial gap-to-diameter ratio within the examined range of e0/D (−0.25<e0/D<0.75). The comparison of the pipe vibrations near an erodible soil with those near a rigid boundary and under wall-free conditions indicates that the vibration amplitudes of the pipe near an erodible sand bed are close to the curve fit under wall-free conditions; nevertheless, for the same stability parameter, the maximum amplitudes for the VIV coupled with local scour increase with the increase of initial gap-to-diameter ratio. 相似文献
970.
A free vibration analysis of laminated composite plates carrying a distributed patch mass is analyzed and presented in this paper. The Hamilton's Principle, using third-order shear deformation theory, is applied to simply supported rectangular plates. The displacement of the plate is postulated by a double Fourier series. The effects of size and location of the distributed patch mass on the response of the plate are also presented. A thorough comparison with well known published results is presented for the case of free vibration of unloaded plates and good agreement is observed. 相似文献