Effects of fundamental factors on coupled vibration of wind-rail vehicle-bridge system for long-span cable-stayed bridge

In a wind-vehicle-bridge(WVB) system,there are various interactions among wind,vehicle and bridge.The mechanism for coupling vibration of wind-vehicle-bridge systems is explored to demonstrate the effects of fundamental factors,such as mean wind,fluctuating wind,buffeting,rail irregularities,light rail vehicle vibration and bridge stiffness.A long cable-stayed bridge which carries light rail traffic is regarded as a numerical example.Firstly,a finite element model is built for the long cable-stayed bridge.The deck can generally be idealized as three-dimensional spine beam while cables are modeled as truss elements.Vehicles are modeled as mass-spring-damper systems.Rail irregularities and wind fluctuation are simulated in time domain by spectrum representation method.Then,aerodynamic loads on vehicle and bridge deck are measured by section model wind tunnel tests.Eight vertical and torsional flutter derivatives of bridge deck are identified by weighting ensemble least-square method.Finally,dynamic responses of the WVB system are analyzed in a series of cases.The results show that the accelerations of the vehicle are excited by the fluctuating wind and the track irregularity to a great extent.The transverse forces of wheel axles mainly depend on the track irregularity.The displacements of the bridge are predominantly determined by the mean wind and restricted by its stiffness.And the accelerations of the bridge are enlarged after adding the fluctuating wind.

Conformal analysis of fundamental frequency of vibration of simple-supported elastic ellipse-plates with concentrated substance

Aimed at calculating the fundamental frequency of vibration of special-shaped, simple-supported elastic plates, Conformal Mapping theory is applied, and the mathematical method of trigonometric interpolation with interpolation points mutual iterative between odd and even sequences in boundary region is provided, as well as the conformal mapping function which can be described by real number region between complicated region and unit dish region is carried out. Furthermore, in the in-plane state of constant stress, vibrating function is completed by unit dish region method for simple-supported elastic plates with concentrated substance of complicated vibrating region, and the coefficient of fundamental frequency of the plate is analyzed. Meanwhile, taking simple-supported elastic ellipse-plates as an example, the effects on fundamental frequency caused by eccentric ratio, the coefficient of constant in-plane stress, as well as the concentrated substance mass and positions are analyzed respectively.

Experimental Mode and Vibration Comfort Analysis of High-Rise Glulam Building Floor Structure

In order to better meet the objective requirements of the use safety of the high-rise glulam building floor structure and the living comfort of the residents,the transient excitation,environmental excitation and frequency spectrum identification methods were used to carry out experimental modal test in-site on the three rooms numbered A,B and C of the same glulam structural building.The three rooms have different functions,different floor sizes and different floor supporting structures.The research results have shown that the first-order bending frequency of the floor structure of Room A is 27.50 Hz,the transverse second-order bending frequency is 34.75 Hz,the longitudinal second-order bending frequency is 53.25 Hz,and the first-order torsional frequency is 56.25 Hz.The reinforced wooden beam at the bottom of the floor of Room A increases the transverse stiffness of the floor structure,but does not offset the anisotropy caused by the longitudinally installed glulam floors.The fundamental frequency values of the floor structures of the three rooms numbered A,B,and C are 27.5,13 and 18 Hz,respectively.This has a relatively high innovation and reference significance for integrating the theory of structural dynamic characteristics with the dynamic testing technology,improving the design level of high-rise glulam structure buildings,and improving the living comfort of residents.

Mapping analysis of vibrating fundamental frequency for simple-supported elastic rectangle-plates with concentrated mass

By conformal mapping theory, a trigonometric interpolation method between odd and even sequences in rectangle boundary region was provided, and the conformal mapping function of rectangle-plate with arc radius between complicated region and unite dish region was carried out. Aiming at calculating the vibrating fundamental frequency of special-shaped, elastic simple-supported rectangle-plates, in the in-plane state of constant stress, the vibration function of this complicated plate was depicted by unit dish region. The coefficient of ftmdamental frequency was calculated. Whilst, taking simple-supported elastic rectangle-plates with arc radius as an example, the effects on fundamental frequency caused by the concentrated mass and position, the ratio of the length to width of rectangle, as well as the coefficient of constant in-plane stress were analyzed respectively.

Correlation of Structural Seismic Damage with Fundamental Period of RC Buildings

The sufficient estimation of the natural period of vibration constitutes an essential step in earthquake design and assessment and its role in the development of seismic damage is investigated in the current research. The fundamental period is estimated for typical reinforced concrete building types, representative of the building stock of Southern Europe, according to existing relationships. The building typologies also represent groups of 180,945 existing damaged buildings of an observational database created after the Athens (7-9-1999) near field earthquake. The estimated fundamental periods are correlated to several degrees of the recorded damage. Important conclusions are drawn on the parameters (height, structural type, etc.) that influence the seismic response and the development of damage based on the wide database. After conducting a correlation analysis, noticeable is the difference between the seismic demand of the elastic spectrum of the first (1959), the contemporary (2003) Greek Seismic Code and the values of peak ground accelerations of several Athens earthquake records. Moreover, PGAs in most records are often between the lower and the upper bound of the estimated fundamental periods for RC buildings with regular infills (n-normal) and with ground levels without infill panels (p-pilotis) regardless the height. A disparity is noticed when the estimated fundamental period is based on EC8 provisions for the considered as “high” buildings in S. Europe regarding the referring earthquake. The majority of buildings that developed several degree, type and extent of damage are considered of “low” height with estimated fundamental periods close to the PGA values of Athens earthquake ground motions. However, the developed damage was the result of the combination of parameters based on geological, tectonic and morphological characteristics of the affected area. In addition, a damage scale for the measurable recording, beyond the qualitative characterization of seismic damage in Greek post-earthquake surveys, is presented wherein the performance levels are defined according to the physical description of the seismic damage and, as well, in terms of structural and economic damage index.

爆破振动强度、波形与频谱研究综述:预测及主动控制

岩石钻孔爆破不可避免地会产生爆破振动效应及危害,准确预测爆破振动效应并进行主动控制具有极大的现实意义。论文综述了近40年来,国内外研究人员在爆破振动预测及主动控制方面取得的研究成果。在爆破振动速度峰值(PPV)预测方面,经验模型预测方法体现出了较大的便捷性,但预测精度与效果较差,将概率统计理论引入经验模型预测方法,提高了PPV预测精度;而基波叠加预测方法可实现对振速、频率和持续时间的综合预测,但是该方法对振动基波的测试精度要求较高,同时亟须在行业内建立对爆破振动采集设备的定期标定与校核机制;人工智能预测方法极大提高了PPV预测精度,同时为多因素影响下的爆破振动效应预测提供了新思路,但需要建立在海量真实有效实测数据的基础上,目前还缺乏充实的振动测试样本数据库;PPV预测理论模型及数值模拟预测法对理论与专业知识、数值模拟技术等要求高,限制了两种方法在工程的普遍应用。在爆破振动速度主动控制上,可以确定合理的延期时间,采用毫秒延迟干扰减振法来降低PPV,但目前多为单一防护对象所提出的延期时间建议值;从调整爆破振动频谱结构的角度,通过主动改变延期时间调控爆破振动频率成分,可避开建(构)筑物自振频带,减小爆破振动危害,然而目前仅仅停留在理论层面或模型试验尺度条件下,缺乏大规模的现场应用实例。最后,对未来爆破振动预测及控制方面重点研究内容进行了展望。

GIS设备内外部紧固松动机械缺陷振动特性对比分析研究

气体绝缘组合电器(gas insulated switchgear,GIS)机械性缺陷是导致设备故障的重要原因。当GIS存在机械缺陷时,在交流电动力的作用下会产生异常振动信号,通过测量GIS外壳上的机械振动信号能够实现对设备机械缺陷的检测和诊断。GIS设备内部或者外部紧固松动是现场常见的机械性缺陷,然而目前对于内外部紧固松动缺陷的振动信号特性尚不清楚,制约了现场对于该类型缺陷的检测与诊断。针对于此,文中在550 kV实体GIS试验平台上构建了内部屏蔽罩松动和外部地脚螺栓松动两类缺陷,对比分析了不同缺陷下的振动信号时、频域特征,以及信号特征和负载电流的关联关系。结果表明,内外部缺陷均不会引起100 Hz基频振动信号发生变化,而仅导致其余频率点信号略有升高,因此无论是内部还是外部松动缺陷都不会引起设备振动信号幅值的明显升高;相比较而言,内部松动缺陷主要引起200、300 Hz等低频信号分量的升高,而外部松动缺陷主要引起1500 Hz以上高频信号分量的幅值升高;内部松动缺陷引起的低频信号分量升高程度随着负载电流的增加明显增加,而外部松动缺陷引起的高频分量升高程度与负载电流相关性较小。文中的研究成果为现场GIS内外部松动缺陷的检测和分析提供了理论支撑。

温度场下功能梯度圆锥壳-环板振动特性分析

针对功能梯度圆锥壳-环板组合结构振动问题,本文采用一阶剪切变形理论和Rayleigh-Ritz法分析了温度场下组合结构的振动特性。组合结构位移变量采用谱几何法来表征,考虑材料参数与温度相关并引入人工边界弹簧建立了组合结构振动特性分析模型。数值算例中,通过将文中求解结果与文献解和有限元法结果进行对比验证了模型的正确性,进而分析尺寸、材料、温度和连接位置等参数对结构振动特性的影响。研究结果表明:组合结构基频随厚度增加而增加,随着幂律指数、半顶角和温度场参数增加而降低,随环板内径和连接位置变化会呈现非单一变化趋势。

An Analysis of the Origin of the Interaction Force between Electric Charges, including Justification of the ln<i>r</i>Term in the Completed Coulomb’s Law, in HM16 Ether

In this study, we demonstrate the correctness of our 2010 hypothesis regarding the need to complete Coulomb’s FC law with the term lnr, resulting in the completed FCC force. For this purpose, we consider the electrical interactions between charged microparticles (MPs), which develop as fundamental vibrations (FVs) in ether, producing the vibrational strains &epsilon;and &gamma;and the resulting stresses &sigma;and &tau;, as percussions of ether cells (ECs) upon the MP surface. The stresses &sigma;?and?&tau;produce a resultant force FP, due to the percussions which constitute the real electric force FCC. The spatial effect of ether on FP is demonstrated by an analytical method, considering the electrical interaction between MPs through various equidistant spatial paths li of FVs, modelled on the basis of the Huygens principle for waves. For this issue, we utilized a numerical calculation, which could be generalized. But this spatial effect of the ether leads at a very slow decreasing of the FP forces ratio rF when doubling the distance l, in contrast to Coulomb’s FC forces whose ratio rF?decreases accentuate with doubling l. Accordingly, the necessity of including the term ln r in the FCC force, which is limited to 1.0 for doubling l, at long distances, was justified.

Surface Soil Effects Studies Based on HN Ratios of Microtremors at Kingston Metropolitan Area, Jamaica

The authors performed single mobile microtremor measurements at 218 sites at KMA （Kingston Metropolitan Area） with the objective of estimating the amplification effects due to the earthquake ground motion on the surface geology. The Fourier transform was applied to the most stationary parts of the triaxial wave motion recordings for each individual site and applied the traditional Nakamura technique, namely, the horizontal to vertical spectral ratio （H/V） to retrieve the predominant shear wave period of vibration of the soil profiles above the bedrock. The results yield predominant long periods of about 3.0-4.0 s in the port area and the waterfront, 1.0-2.0 s in the central part of Kingston, 0.3-1.0 s in Portmore and very stiff soil conditions in the surrounding area of the city. The results coincide fairly well with previous geological studies in the region, geotechnical data in boreholes, gravimetric measurements and strong motion recordings, suggesting a high degree of amplification of ground motion in the whole period range of engineering interest. Additionally, the authors obtained the liquefaction vulnerability factor Kg proposed by Nakamura based on the H/V ratio of microtremors. The results suggest that the port area, the waterfront and the Port Royal are highly susceptible to liquefaction. Finally, the authors obtained fundamental periods of vibration based on microtremor measurements on the roof and the basement of four important buildings in the KMA and indicated future lines of research employing ambient noise measurements on structures.

New Properties of HM16 Ether, with Submicroparticles as Self-Functional Cells Interacting through Percussion Forces, Establishing Nature of Electrical Charges, including Gravitation

Article continues and complements our previous articles on the HM16 ether (ETH) model. Here, we describe the mechanism of occurrence of the submicroparticle (SMP). A general hypothesis, HFVI, is introduced for the modalities of interaction between two SMPs, based on periodic mechanical percussion forces, produced by fundamental vibrations FVs. A mechanism for describing the interaction between a SMPs and the ETH is presented. Positive and negative particles are defined by their membrane types of movement, such as +, −u/+, −v vibrations, and rotations at speeds +Ω/−Ω. The process of creating a pair of SMPs is discussed. Applying HFVI to the interaction between pairs of SMPs immobile in ETH, and considering longitudinal FVL, was obtained the forces of attraction/repulsion +FL21/–FL21, which correspond to the completed Coulomb force FCC including gravitation. The resultant FRL21 will form an oriented field of forces, which is a quasielectric field QE, equivalent to actual E electric field. Considering transversal FVT, was obtained the vibratory forces +, −FT21, whose resultant forms an vibrating field of forces, QHs, a quasimagnetic special field, which may explain some of the quantum properties of SMPs. Considering a mobile SMP, two new γ strains in ETH appear. Strains γL are created by the displacement of SMP with velocity V, whose force +, −FT12 is the support of a component of the magnetic field H (quasimagnetic field QH), giving the QHL component. Strains γR are created by the rotation of SMP with speed Ω, whose force +, −FR12 constitutes physical support of the component QHR of magnetic field H (i.e. QH). The creation of a photon PH is modelled as a special ESMP containing two zones of opposed rotations, and a mechanism is presented for its movement in the ETH with speed c based on the HS hypothesis of screwing in ETH, with frequency ν.

削弱表贴式永磁电机2p阶径向电磁力波幅值的磁极设计方法

电磁振动是影响电机性能的主要因素之一,针对瓦片形磁极永磁电机2 p阶径向电磁力波引起的电磁振动,提出优化磁极参数的方法用以改变高阶磁密谐波相位和幅值,进一步削弱2 p阶径向电磁力波幅值。根据径向磁密解析表达式,推导出2 p阶径向电磁力波与磁极参数的函数关系,分析各磁极参数对气隙磁密和2 p阶径向电磁力波的影响;进一步求得使2 p阶径向电磁力波幅值最小化的目标函数,并用内点法得到优化的磁极结构参数,对比分析优化前后有限元计算的电磁性能和2 p阶处的振动响应。结果表明,该优化设计磁极的方法可在不降低电机性能的同时,抑制2 p阶径向电磁力波引起的电磁振动。

3种无损检测技术评估足尺规格材的静态弹性模量

首先利用横向振动、纵向基频振动和超声波3种无损检测法获得天然林樟子松Pinus sylvestris var.mongolica足尺规格材(38 mm×89 mm×4 000 mm)和人工林杉木Cunninghamia lanceolata足尺规格材(45 mm×90 mm×2 500 mm)动态弹性模量,同时根据D198-99(American Society for Testing and Materials)标准测试了其静态弹性模量;进而通过探讨动态与静态弹性模量之间的相互关系。研究结果表明,无论对哪种木材的规格材,利用上述3种无损检测方法获得动态弹性模量(Etv,Efr,Eusw)与静态弹性模量(Etru)平均值之间的关系为:Eusw>Efr>Etru>Etv;动态弹性模量与静态弹性模量之间的线性相关极显著,表明这3种无损检测方法均可以用于评估规格材的静态弹性性质;从设备的方便、可靠和易操作等方面综合考虑,利用纵向基频振动法来评估规格材的静态弹性模量,其预测效果更为理想;天然林樟子松和人工林杉木比较而言,动静态弹性模量线性相关决定系数前者大于后者,即预测天然林樟子松规格材效果更好。

基于振动频率法的斜拉桥索力测试影响因素

基于振动频率法,研究拉索自身参数和外界条件对拉索基频的影响。运用拉索静力平衡振动方程,推导考虑阻尼的拉索振动基频计算方法,研究拉索垂度和抗弯刚度对基频计算的影响范围。通过数值计算,分析阻尼器、梁体振动和温度变化等外界条件对基频计算的影响规律,提出斜拉桥索力测试和基频计算建议。研究结果表明:当反映垂度影响的量λ2≤0.9,不可忽略垂度的影响;当反映抗弯刚度影响的量0≤ξ≤210,不可忽略抗弯刚度的影响。拉索安装阻尼器将导致索基频增加,阻尼器安装越远离锚固端对基频的影响越大;拉索越长和直径越小,阻尼器对基频影响也越大。斜拉桥梁体振动时进行索力测试,拉索的基频存在动态波动;拉索温度越高,基频越小。建议选取车流较少、温度稳定的环境进行索力测试以获得较准确的基频。

动态弹性模量用于评估不同等级规格材的研究

参照加拿大锯材目测分等规则,将人工林杉木(Cunninghamia lanceolata(Lamb.)Hook.)足尺规格材(45 mm×90 mm×3 700 mm)分成精选级(SS)及Ⅰ、Ⅱ、Ⅲ4个等级,利用纵向基频振动无损检测法获得动态弹性模量,同时参照ASTM D198—99标准测试了其静态抗弯弹性模量。探讨不同等级的动态与静态抗弯弹性模量之间的相互关系,并比较不同等级静态抗弯弹性模量发现:不同等级动静态弹性模量的相互关系不同,其决定系数(R2)依次分别是0.761(Ⅱ)、0.715(SS)、0.703(Ⅰ)和0.356(Ⅲ),即Ⅱ等级以上的动静态弹性模量的相关性很好,可以通过动态弹性模量预测规格材的静态弹性模量;Ⅲ等级的相关性稍差一点,但都在0.01水平上具有显著的相关性;不同等级的静态抗弯弹性模量不等,Ⅱ等级的静态抗弯弹性模量值最大10.701 GPa,其次分别是SS、Ⅰ、Ⅲ,依次分别为:10.359、9.840、9.554 GPa。

基于广义回归神经网络的变压器表面振动基频幅值计算

变压器振动基频幅值大小是分析和评判变压器运行状态和故障诊断的重要依据。为此,提出一种基于广义回归神经网络(GRNN)的变压器振动基频幅值计算方法,用于计算正常运行状态下的变压器表面振动基频幅值。所提方法考虑变压器振动产生机理和影响因素,先根据变压器运行电压、负载电流、油温等历史运行工况数据以及表面振动历史数据进行GRNN训练,保存训练好的GRNN网络即可根据实时运行工况数据计算变压器表面振动基频幅值。某台在运变压器表面振动实测信号的计算结果表明:所提方法比现有方法计算误差大幅下降约50%。研究结果可为变压器振动在线监测提供重要参考。

大跨度蜂窝形空腹夹层板楼盖动力特性分析

为研究新型大跨度钢筋混凝土蜂窝形空腹夹层板楼盖的动力特性,基于通用有限元软件ANSYS,采用子空间迭代法计算结构的基频和各阶振型,考察高跨比、空腹率、上肋和下肋宽度、密肋宽度与高度、表层板厚度、密柱截面边长和边梁宽度等参数对结构基频的影响。分析结果表明,空腹夹层板的振型特征与实心平板结构的振型相似,低阶振型主要表现为楼盖的竖向振动,但空腹夹层板质量轻,刚度分布均匀,受力合理。影响结构基频的主要因素为高跨比、空腹率和密柱截面边长以及上肋和下肋宽度;密肋尺寸、表层板厚度和边梁宽度对空腹夹层板的基频影响较小。为了满足对结构振动舒适度的要求,在工程设计时应将高跨比、空腹率和密柱截面边长作为主要指标进行控制。

硬岩掘进机比例调速阀选型方法

针对硬岩掘进机(Tunnel boring machine,TBM)破岩掘进过程中产生的振动对比例调速阀性能的影响,建立基础振动下比例调速阀的选型准则。选择比例调速阀为研究对象,分析其工作原理,建立比例调速阀仿真模型,并对其进行试验验证,仿真分析基础振动参数对其流量波动特性的影响规律。以10%的流量偏差值为评定标准,结合实例分析确定TBM比例调速阀的稳定工作区域并建立其选型流程。结果表明:基础振动会引起比例调速阀流量波动而导致其性能失效,新的选型流程满足TBM比例调速阀的工程实际要求。

β-榄香烯振动光谱的量子化学从头计算

利用G98及GAMESS从头计算程序的RHF 6 31 方法 ,对 β 榄香烯的全部振动基频作了计算 ,并与实测红外光谱做了对比 ,归属了它们的振动模式 ,讨论了它们的特征基频 ,并对理论计算的振动频率进行了标度校正。

纵振激励频率对圆盘弯曲振动特性的影响

利用有限元方法,计算并分析了具有一定大小的激励面积、频率不同的纵向夹心式换能器激励圆盘中心时,产生一阶弯曲振动的规律。结果表明:随着激励源频率的逐渐提高,圆盘弯曲振动的基频在不断增大,节圆半径也在增大,圆盘圆心处的位移振幅先增大后减小。实验测试与有限元计算结果基本吻合。该研究为此类复合纵弯振动系统的设计和实际应用提供了一定的参考。