Wind-induced vibration control of bridges using liquid column damper

The potential application of tuned liquid column damper (TLCD) for suppressing wind-induced vibration of long span bridges is explored in this paper.By installing the TLCD in the bridge deck,a mathematical model for the bridge-TLCD system is established.The governing equations of the system are developed by considering all three displacement components of the deck in vertical,lateral,and torsional vibrations,in which the interactions between the bridge deck,the TLCD,the aeroelastic forces,and the aerodynamic forces are fully reflected.Both buffeting and flutter analyses are carried out.The buffeting analysis is performed through random vibration approach,and a critical flutter condition is identified from flutter analysis.A numerical example is presented to demonstrate the control effectiveness of the damper and it is shown that the TLCD can be an effective device for suppressing wind-induced vibration of long span bridges,either for reducing the buffeting response or increasing the critical flutter wind velocity of the bridge.

Wind-Induced Vibration Control for Substation Frame on Viscous Damper

In order to study the wind-induced vibration control effect of the viscous damper on the large-scale substation frame,this paper takes the large-scale 1000 kV substation frame of western Inner Mongolia as an example.The time-history sample of pulsating wind load is simulated by harmonic superposition method based on Matlab software.6 kinds of viscous damper arrangement schemes have been designed,and SAP2000 finite element software is used for fine modeling and input wind speed time history load for nonlinear time history analysis.The displacement and acceleration of a typical node are the indicators of wind vibration control.The wind-induced vibration control effects of different schemes under different damping parameters have compared,and the damping parameters are analyzed for the optimal layout scheme.The results show that a viscous damper has installed in the lower layers of the substation;a viscous damper is placed between the ground column and the lattice beam.It is an integrated optimal solution.The wind-induced vibration control effect of the optimal scheme is sensitive to the viscous damper parameters,and the control effect does not increase linearly with the increase of the damping index and the damping coefficient.Corresponding to different damping indexes,the damping coefficient has a better range of values.

Wind-induced vibration control of long-span power transmission towers

We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.

Wind-induced vibration of single-layer reticulated shell structures

Aiming at the dynamic response of reticulated shell structures under wind load,systematic parameter analyses on wind-induced responses of Kiewitt6-6 type single-layer spherical reticulated shell structures and three-way grid single-layer cylindrical reticulated shell structures were performed with the random simulation method in time domain,including geometric parameters,structural parameters and aerodynamic parameters.Moreover,a wind-induced vibration coefficient was obtained,which can be a reference to the wind-resistance design of reticulated shell structures.The results indicate that the geometric parameters are the most important factor influencing wind-induced responses of the reticulated shell structures;the wind-induced vibration coeffi-cient is 3.0-3.2 for the spherical reticulated shell structures and that is 2.8-3.0 for the cylindrical reticula-ted shell structures,which shows that the wind-induced vibration coefficients of these two kinds of space frames are well-proportioned.

Case Study of Wind-Induced Vibration of a Cooling Tower Under Typhoon Environment

As high-rise cooling towers are constantly emerging,wind effects on this kind of wind-sensitive structures have attracted more and more attention,especially in typhoon prone areas.Terrain Type B turbulent flow fields under the normal wind and typhoon are simulated by active wind tunnel technology,and rigid-pressure-measurement model and aero-elastic-vibration-measurement model of a large cooling tower are built.The stagnation point,peak suction point,separation point and leeward point of the throat position shell are selected to analyze pressure coefficient,probability distribution,peak factor,power spectral density and dynamic amplification factor under normal wind and typhoon.It is clarified that there exists a significant non-Gaussian characteristic under typhoon condition,which also exists in structural response level.Resonance response ratio of the total response is higher during typhoon condition.The maximum value of dynamic amplification coefficient under typhoon field is up to 1.18 times over that under normal wind.The findings of this study are expected to be of interest and practical use to professional and researchers involved in the wind-resistant designs of super-large cooling towers in typhoon prone regions.

Wind tunnel study on wind-induced vibration of middle pylon of Taizhou Bridge

Full aero-elastic model tests are carried out to investigate wind-induced vibration of middle steel pylon of Taizhou Bridge. Model of the pylon under different construction periods is tested in both uniform and turbulent flow field. And the yaw angle of wind changes from transverse to longitudinal. Through full aero-elastic model testing, wind-induced vibration is checked, which includes vortex resonance, buffeting and galloping. Vortex resonance is observed and further studies are carried out by changing damping ratio. Based on wind tunnel testing results, wind-resistance of middle pylon is evaluated and some suggestions are given for middle pylon's construction.

Rain-Wind Induced Vibration Mitigation of Stay Cables by Aerodynamic Means

Stay cables with various surface profiles were tested in wind tunnel. Dimples and helical fillets were applied to mitigate the rain- wind induced vibration. The rain-wind excited responses of the cable with smooth surface were larger than those of the cables with dimples and helical fillets. At high Reynolds number, the drag coefficients of cables with dimples and helical fillets are much larger than those of smooth surface cable.

Wind Vibration Study of Long-span Steel Arch Structure of Beijing Capital International Airport

The wind-induced dynamic response of long-span light-weight steel arch structure of the global transportation center (GTC) of Beijing Capital International Airport was studied. A composite technique with combination of WAWS(Weighted Amplitude Wavelet Superposition) and FFT(Fast Fourier Transformation) was introduced to simulate wind velocity time series of hundreds of spatial points simultaneously. The structural shape factors of wind load was obtained from wind tunnel model test. The wind vibration factor based on structural displacement response was investigated. After comparing the computational results with wind tunnel model test data, it was found out that the two results accord with each other if wind comes from 0° direction angle, but are quite different if wind comes from 180° direction angle in the area blocked off by airport terminals. The possible reasons of this difference were analyzed. Haar wavelet was used to transform and analyze wind velocity time series and structural wind-induced dynamic responses. The relationship between exciting wind loads and structural responses was studied in time and frequency domains.

Wind-induced responses of super-large cooling towers

Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.

Passive Perforated Pipe Control Method for Wind?Induced Vibration of a High?Rise Chemical Tower

Vortex-induced vibration is likely to occur when subjected to wind loads because of low horizontal stiffness,resulting in internal force and large lateral amplitude.Long-term wind-induced vibration can not only affect the normal service and durability performance of chemical towers,but also seriously endanger the safety of towers in service periods,and cause property losses.In this study,a passive control method for suppressing wind-induced vibration of chemical towers is proposed.The flow around the flow field is guided by a pre-set air-blowing channel,thus destroying the unsteady vortex shedding in the wake region of the flow field and achieving the purpose of flow control.Two accelerometers are used to measure the vibration signal of the chemical tower model with and without the perforated pipe.The control effects of the spacing and the installation position of the perforated pipe are then studied.Experimental results show that the passive perforated pipe control method can effectively reduce the vibration amplitude of the chemical tower under wind loads,and decrease the potential wind-induced vibration.

Application of Lead Viscoelastic Dampers to Wind Vibration Control on Big-Span Power Transmission Tower

To study the wind vibration response of power transmission tower, the lead viscoelastic dampers （LVDs） were applied to a cup tower. With time history analysis method, the displacement, velocity, acceleration and force response of the tower was calculated and analyzed. The results show that the control effect of lead viscoelastic dampers is very good, and the damping ratio can reach 20% or more when they are applied to the tower head.

Numerical Simulation Study of Vibration Characteristics of Cantilever Traffic Signal Support Structure under Wind Environment

Computational fluid dynamics(CFD)and the finite element method(FEM)are used to investigate the wind-driven dynamic response of cantilever traffic signal support structures as a whole.By building a finite element model with the same scale as the actual structure and performing modal analysis,a preliminary understanding of the dynamic properties of the structure is obtained.Based on the two-way fluid-structure coupling calculation method,the wind vibration response of the structure under different incoming flow conditions is calculated,and the vibration characteristics of the structure are analyzed through the displacement time course data of the structure in the crosswind direction and along-wind direction.The results show that the maximum response of the structure increases gradually with the increase of wind speed under 90°wind direction angle,showing a vibration dispersion state,and the vibration response characteristics are following the vibration phenomenon of galloping;under 270°wind direction angle,the maximum displacement response of the structure occurs at the lower wind speed of 5 and 6m/s,and the vibration generated by the structure is vortex vibration at this time;the displacement response of the structure in along-wind direction increaseswith the increase of wind speed.The along-wind displacement response of the structure will increase with increasing wind speed,and the effective wind area and shape characteristics of the structurewill also affect the vibration response of the structure.

Statistical extremes and peak factors in wind-induced vibration of tall buildings

In the structural design of tall buildings, peak factors have been widely used to predict mean extreme responses of tall buildings under wind excitations. Vanmarcke＇s peak factor is directly related to an explicit measure of structural reliability against a Gaussian response process. We review the use of this factor for time-variant reliability design by comparing it to the conven- tional Davenport＇s peak factor. Based on the asymptotic theory of statistical extremes, a new closed-form peak factor, the so-called Gamma peak factor, can be obtained for a non-Gaussian resultant response characterized by a Rayleigh distribution process. Using the Gamma peak factor, a combined peak factor method was developed for predicting the expected maximum resultant responses of a building undergoing lateral-torsional vibration. The effects of the standard deviation ratio of two sway components and the inter-component correlation on the evaluation of peak resultant response were also investigated. Utilizing wind tunnel data derived from synchronous multi-pressure measurements, we carried out a wind-induced time history response analysis of the Common- wealth Advisory Aeronautical Research Council （CAARC） standard tall building to validate the applicability of the Gamma peak factor to the prediction of the peak resultant acceleration. Results from the building example indicated that the use of the Gamma peak factor enables accurate predictions to be made of the mean extreme resultant acceleration responses for dynamic service- ability performance design of modem tall buildings.

Experimental study and finite element analysis of wind-induced vibration of modal car based on fluid-structure interaction

The wind-induced vibration of the front windshield concerns the traffic safety and the aerodynamic characteristics of cars. In this paper, the numerical simulation and the experiment are combined to study the wind-induced vibrations of the front windshield at different speeds of a van-body model bus. The Fluid-Structure Interaction （FSI） model is used for the finite element analysis of the vibration characteristics of the front windshield glass in the travelling process, and the wind-induced vibration response characteristics of the glass is obtained. A wind-tunnel experiment with an eddy current displacement sensor is carried out to study the deformation of the windshield at different wind speeds, and to verify the numerical simulation results. It is shown that the windshield of the model bus windshield undergoes a noticeable deformation as the speed changes, and from the deformation curve obtained, it is seen that in the accelerating process, the deformation of the glass increases as the speed increases, and with the speed being stablized, it also tends to a certain value. The results of this study can provide a scientific basis for the safety design of the windshield and the body.

Wind-induced vibration control of Hefei TV tower with fluid viscous damper

The Hefei TV tower is taken as an analytical case to examine the control method with a fluid viscous damper under wind load fluctuation.Firstly,according to the random vibration theory,the effect of fluctuating wind on the tower can be modeled as a 19-dimensional correlated random process,and the wind-induced vibration analysis of the tower subjected to dynamic wind load was further obtained.On the basis of the others'works,a bi-model dynamic model is proposed.Finally,a dynamic model is proposed to study the wind-induced vibration control analysis using viscous fluid dampers,and the optimal damping coefficient is obtained regarding the wind-induced response of the upper turret as optimization objectives.Analysis results show that the maximum peak response of the tower under dynamic wind load is far beyond the allowable range of the code.The wind-induced responses and the wind vibration input energy of the tower are decreased greatly by using a fluid viscous damper,and the peak acceleration responses of the upper turret is reduced by 43.4%.

考虑质量分布的雨蚀叶片横向振动分析与自抗扰解耦控制

为提升高速耐雨蚀测试装置运行的稳定性与安全性,以其转子-雨蚀叶片系统为研究对象,开展雨蚀叶片的横向振动特性分析。首先,综合考虑雨蚀叶片振动、旋叶连接盘质量偏心及转子不平衡磁拉力的影响,建立转子-雨蚀叶片系统的四自由度横向振动模型。然后,基于Lagrange方程建立转子-雨蚀叶片系统的运动微分方程,并利用Runge-Kutta算法对方程进行数值求解,以观察转子及雨蚀叶片的轴心轨迹与振幅的分布规律。考虑到转子与雨蚀叶片的非线性强耦合关系,采用自抗扰解耦控制方法来抑制雨蚀叶片的横向振动,其中扩张状态观测器的参数采用极点配置和带宽进行调节。最后,通过搭建实验平台来分析采用自抗扰解耦控制前后雨蚀叶片的振动特性,并与数值分析结果进行对比。结果表明,在采用自抗扰解耦控制前转子-雨蚀叶片系统存在振动超标现象,而采用自抗扰解耦控制后雨蚀叶片的横向振动得到了有效抑制,验证了该控制方法的可行性和有效性。研究结果可为后续高速耐雨蚀测试装置的结构优化提供理论参考。

基于轴箱振动加速度的高速动车组车轮载荷谱编制方法研究

提出了一种基于线路实测轴箱振动加速度的车轮载荷测量新方法。通过建立高速动车组动力学模型,开展时域仿真得到轴箱振动加速度和轮轨力的时域信号,并以轴箱振动加速度线路测试结果对仿真模型的有效性进行验证,依据3σ原则计算仿真结果中轴箱垂向和横向加速度以及轮轨作用力的统计值,获得由轴箱振动加速度推算车轮的载荷传递系数。应用载荷传递系数,结合线路实测轴箱振动加速度推算了车轮载荷-时间历程,并编制了车轮垂向和横向载荷谱。研究结果表明:基于轴箱振动加速度的车轮载荷谱推算方法切实可行,为车轮载荷谱编制工作提供了一种新的思路。

斜拉桥拉索的风(雨)激振及控制

目前,国内建造了大量的斜拉桥。随着斜拉桥跨度的增大,拉索的风致振动及风雨激振问题越来越突出。本文总结了国际上的有关研究,特别是拉索风雨激振及控制研究的成果,指出了这一领域中有重要意义的研究方向。

磁流变阻尼器在斜拉索减振中的应用

大跨度斜拉桥拉索的大幅振动及其控制越来越引起人们的重视 ,应用磁流变阻尼器进行拉索减振是一种新的探索。文中介绍在洞庭湖大桥应用磁流变阻尼器进行拉索减振的试验研究情况 ,得到了安装阻尼器前后拉索的动力特性 ,结果显示拉索系统的模态频率在安装阻尼器后增大了 3 %～ 4% ,模态阻尼比无阻尼器时增大了 3倍～ 6倍。磁流变阻尼器的减振效果经历了实际风雨振的检验 ,在其他拉索发生大幅振动的情况下 ,装有磁流变阻尼器的拉索稳定如常 ,其振幅减小 2 0倍～ 3 0倍。证明该阻尼器是拉索减振的有效手段。

高精度风雨模拟环境下拉索风雨激振试验研究新发现

拉索风雨激振是一种在风雨共同作用下发生的拉索大幅低频振动,现有人工降雨风雨激振试验无法准确模拟自然降雨的多种特性,难于实时再现风雨介质耦合环境拉索气动失稳现象。开发高精度人工降雨模拟装置,可对降雨强度进行精细连续调节,较为准确模拟雨滴大小、能量、均匀度等自然降雨的特性,合理地再现风雨联合作用条件下拉索风雨激振过程;系统研究风速、雨量以及风雨联合作用对拉索风雨激振的影响,揭示了拉索在低风速大雨量、高风速小雨量时,风雨激振发生规律和特点。