Sectional model test study on vortex-excited resonance of vehicle-bridge system of Shanghai Bridge over Yangtse River

It is necessary to study how vehicles influence the vortex-excited resonance of vehicle-bridge systems, because lock-in wind speed is low and vortex-excited resonance is sensitive to any change in the main girder sections. Based on the Shanghai Bridge over the Yangtse River, the vortex-excited resonance of a 1:60 scale sectional model was tested in a TJ-1wind tunnel, with or without vehicles at the attack angle of 0°, + 3 and − 3°, respectively. The conversion relationships between the resonant amplitudes of the sectional model and that of the prototype bridge were also established by mode shape correction. The result indicates that: 1) for the bridge with vehicles, the vertical vortex-excited resonance is accompanied by torsion vibration with the same frequency, and vice versa, 2) the amplitude of vortex-excited resonance of the bridge with vehicles is much larger than that of the bridge without vehicles, and 3) the lock-in wind speed of the vortex-excited resonance becomes smaller due to the disturbance of vehicles. It is obvious that vehicles bring about changes in the aerodynamic shape of the main girder. Therefore, the influence of vehicles on vortex-excited resonance performance of vehicle-bridge systems, in terms of both amplitude and mode, should not be ignored. __________ Translated from China Civil Engineering Journal, 2007, 40(8): 61–66 [译自: 土木工程学报]     

上海长江大桥风-轨道车辆-桥耦合振动及抗风行车准则研究

为确定上海长江大桥轨道交通车辆的抗风行车准则,将风、车、桥三者视为一个交互作用、协调工作的耦合动力系统,通过风洞试验测定主梁及车辆的气动参数,采用自主研发的桥梁结构分析软件BANSYS进行风-车-桥耦合动力分析计算。计算结果表明:桥梁和车辆的响应随风速的增大而增大,风荷载对行车的安全性和舒适性有很大影响。当风速小于20m/s时,车辆可按设计车速90km/h运行;当风速在20～30m/s之间时,车速不应大于60km/h;当风速超过30m/s时,应封闭轨道交通。     

Vibration analysis of medium and small span bridges subjected to mixed marshalling freight trains

It has been reported several times that train derailment occurs when mixed marshalling freight trains traverse bridges at high speeds in China. This study aims to explain this phenomenon numerically based on the train-bridge coupling vibration theory and its associated computer program. The train-bridge vibration characteristic is analyzed by a computer program when mixed marshalling freight trains traverse 32-meter-span prestressed concrete simple beam bridges. The mechanism that dynamic responses of the bridges are prominent and that empty trains are inclined to derail are derived from the dynamic responses analysis. The analysis indicates that the significant differences of axle loads between heavy vehicles and empty vehicles produce periodic forced loadings of large amplitudes. These periodic loadings cause severe vibration of bridges. In turn, severe vibration of the bridges produces intensive counteraction to empty vehicles. __________ Translated from Journal of Tongji University (Natural Science), 2007, 35(2): 171–175 [译自: 同济大学学报(自然科学版)]     

Dynamics of wind-rail vehicle-bridge systems

An analytical model for dynamics of wind-vehicle-bridge (WVB) systems is presented in this paper in the time domain with wind, rail vehicles and bridge modeled as a coupled vibration system. The analytical model considers many special issues in a WVB system, which include fluid-solid interaction between wind and bridge, solid contact between vehicles and bridge, stochastic wind excitation on vehicles and bridge, time dependence of the system due to vehicle movement, and effect of bridge deck on vehicle wind load and vice versa. The models of wind, vehicles and bridge are presented with wind velocity fluctuations simulated using the simplified spectral representation method, with vehicles modeled as mass-spring-damper systems, and with bridge represented by a finite element model. The interactions between wind and bridge are similar to those considered in conventional buffeting analysis for long span bridges. In considering difficulties in measuring aerodynamic coefficients of moving vehicles on bridge deck, the cosine rule is adopted for the aerodynamic coefficients of moving vehicles to consider yaw angle effect, and expressions of wind forces on moving vehicles are then derived for engineering application. To include mutual effects of wind loads, aerodynamic parameters of vehicles and bridge deck are measured, respectively, using a composite section model test and a specially designed test device. The dynamic interaction between vehicle and bridge depends on both geometric and mechanical relationships between wheels of vehicles and rails on the bridge deck. The equations of motion of the coupled WVB system are derived and solved with a nonlinear iterative procedure. A cable-stayed bridge in China is finally selected as a numerical example to demonstrate dynamic interaction of the WVB system. The results show the validity of the present model as well as wind effects on the rail vehicles and the bridge.     

Dynamic analysis of rail transit elevated bridge with ladder track

In this paper, a dynamic analysis model of an elevated bridge with ladder tracks under moving train load is established. The whole process of a train running through an elevated bridge at different speeds is simulated. The dynamic responses of the elevated bridge with ladder track and the running safety and comfort index of train vehicles are evaluated. Compared with the dynamic responses of an elevated bridge with ordinary nonballasted slab track, the ladder track’s effect on reducing the vibration of an elevated bridge is analyzed. The analysis results show that the ladder track has good vibration reduction characteristics as compared to ordinary non-ballasted track.     

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 bimodel 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%. __________ Translated from Journal of Southeast University (Natural Science Edition), 2008, 37(6): 1018–1022 [译自: 东南大学学报(自然科学版)]     

Dynamic test and finite element model updating of bridge structures based on ambient vibration

The dynamic characteristics of bridge structures are the basis of structural dynamic response and seismic analysis, and are also an important target of health condition monitoring. In this paper, a three-dimensional finite-element model is first established for a highway bridge over a railroad on No.312 National Highway. Based on design drawings, the dynamic characteristics of the bridge are studied using finite element analysis and ambient vibration measurements. Thus, a set of data is selected based on sensitivity analysis and optimization theory; the finite element model of the bridge is updated. The numerical and experimental results show that the updated method is more simple and effective, the updated finite element model can reflect the dynamic characteristics of the bridge better, and it can be used to predict the dynamic response under complex external forces. It is also helpful for further damage identification and health condition monitoring. __________ Translated from Chinese Journal of Huazhong University of Science and Technology (Urban Science Edition), 2006, 23(4): 57–60 [译自: 华 中科技大学学报(城市科学版)]     

Fatigue stress monitoring and analyses for steel box girder of Runyang Suspension Bridge

The monitoring of fatigue stress of steel bridge is a key issue of bridge health monitoring and safety assessment. This paper aims to find out the strain history features of the girder components of Runyang Suspension Bridge (RYSB) under vehicle and environmental loading during its first year of service based on the strain-history data recorded by structural health monitoring system installed in the bridge. The fatigue stress spectrums of steel box girders under normal traffic load, heavy trucks and typhoon loads were studied as well as the correlation between varying strain and temperature based on real-time monitoring of temperature histories. The results show that, monitoring on local strain in health monitoring systems of RYSB can effectively provide the information on fatigue stresses. The range of the equivalent fatigue stress on the monitoring location of the bridge is currently low, mainly due to varying traffic loading and temperature. There exists significant correlation between varying temperature and mean value of fatigue stress. Effect of the passing of heavy trucks on bridge fatigue is quite significant since the value of the cumulative fatigue damage generated by heavy trucks is 10 to 100 times larger than that by normal traffic. Therefore, the effect on fatigue cumulative damage due to heavy trucks or overloaded vehicles needs to be monitored and paid much attention to. __________ Translated from Journal of Southeast University (Natural Science Edition), 2007, 37(2): 280–286 [译自: 东南大学学报(自然科学版)]     

Framework of vehicle–bridge–wind dynamic analysis

This paper presents a framework of dynamic analysis of coupled three-dimensional vehicle–bridge system under strong winds. A general formulation of this system is introduced to simulate a series of vehicles consisting of different numbers and different types of vehicles running on bridges under hurricane-induced strong winds. Each vehicle is modeled as a combination of several rigid bodies, axle mass blocks, springs, and dampers, considering wind and road roughness loads. With this vehicle–bridge model, coupled dynamic analysis of vehicles running on bridges is conducted with a numerical example. Effects of driving speeds on the dynamic performance of the vehicles as well as the bridge are discussed. It is found that the driving speeds mainly affect the vehicle's vertical relative response while they have insignificant effect on the rolling response of vehicles. Vehicle's absolute response is dominated by the bridge response when wind speed is high, while it is dominated by road roughness when the wind speed is low. Detailed accident analysis of vehicles on bridges under strong winds will be reported in an accompanying paper.     

Comparisons of bridges flutter derivatives and generalized ones

The causes of the nonlinearity of self-excited aerodynamic force of bridge are interpreted from such two aspects as amplitude and wind velocity. The concept of “generalized flutter derivative” is proposed, and its physical meaning is illustrated. The graphs of the generalized flutter derivatives of plate and Sutong Bridge section model are plotted. The characteristics of all generalized flutter derivatives are compared and analyzed, and their superiorities are verified. The results indicate that the physical meaning of generalized flutter derivatives are more explicit compared to the traditional ones. It is more convenient to understand the nonlinearity properties of self-excited aerodynamic force of bridge according to the generalized flutter derivatives graphs with the wind velocity as the horizontal coordinate. __________ Translated from Journal of Wuhan University of Technology (Transportation Science and Engineering), 2008, 32(4): 607–610 [译自: 武汉理工大学学报(交通科学与工程版)]     

Design and stability analysis of continuous skew tied-arch bridge over Bin Jiang River

A tied arch bridge without wind bracing was built over the Bin Jiang River, with oblique angle of 20°. Its main design details are described and mechanical performances are analyzed. The stability analytical types are also introduced and the first elastic stability theory is used. A space finite element model has been built to analyze the stability performances in both construction and operation stages for single span or continuous, orthogonal or oblique bridge. The influence of stiffness of the end crossbeam is also analyzed. The result shows that out-plane buckling occur for a rigid tie and similar no matter whether it is single span or continuous and orthogonal or oblique. When there are more and stronger inner crossbeams, the influence of the end crossbeams on arch stability becomes unremarkable. __________ Translated from Journal of Southeast University, 2006, 36(6): 1007–1012 [译自: 东南大学学报]     

Analysis on running safety of train on the bridge considering sudden change of wind load caused by wind barriers

The calculation formulae for change of wind load acting on the car-body are derived when a train moves into or out of the wind barrier structure, the dynamic analysis model of wind-vehicle-bridge system with wind barrier is established, and the influence of sudden change of wind load on the running safety of the train is analyzed. For a 10-span simply-supported U-shaped girder bridge with 100 m long double-side 3.5 m barrier, the response and the running safety indices of the train are calculated. The results are compared with those of the case with wind barrier on the whole bridge. It is shown that the sudden change of wind load caused by wind barrier has significant influence on the lateral acceleration of the car-body, but no distinct on the vertical acceleration. The running safety indices of train vehicle with sectional wind barriers are worse than those with full wind barriers, and the difference increases rapidly with wind velocity.     

Ribbon bridge in waves based on hydroelasticity theory

For the design and operation of a floating bridge, the understanding of its hydroelastic behavior in waves is of great importance. This paper investigated the hydroelastic performances of a ribbon bridge under wave action. A brief introduction on the estimation of dynamic responses of the floating bridge and the comparisons between the experiments and estimation were presented. Based on the 3D hydroelasticity theory, the hydroelastic behavior of the ribbon bridge modeled by finite element method (FEM) was analyzed by employing the mode superposition method. And the relevant comparisons between the numerical results and experimental data obtained from one tenth scale elastic model test in the ocean basin were made. It is found that the present method is applicable and adaptable for predicting the hydroelastic response of the floating bridge in waves. __________ Translated from Journal of Shanghai Jiaotong University, 2007, 41(9): 1441–1444 [译自: 上海交通大学学报]     

Limit span of self-anchored cable-stayed suspension cooperation system bridge based on strength

The limit span of self-anchored cable-stayed suspension bridge is deduced. The relations among the geometrical parameters, loads and material characteristics are also analyzed. Based on the material strength and commonly used materials, the limit spans of self-anchored cable-stayed suspension bridges with concrete girder or steel girder under vertical static load are discussed in detail. The corresponding upper limit spans and the effect of the factors on the span are given. The results indicate that increasing rise-span ratio, height-span ratio and cable-stayed segment length or reducing the second dead load could increase the cooperation system span. __________ Translated from Journal of Dalian University of Technology, 2008, 48(3): 387–391 [译自: 大连理工大学学报]     

双车交会过程的风-车-桥耦合振动研究

侧向风作用下,双车交会过程中车辆和桥梁的风荷载会发生突变。以大跨度悬索桥为工程背景,通过车桥组合节段模型风洞试验,测试不同状态车辆和桥梁各自的气动力系数。针对强风作用下双车交会过程,通过风-车-桥耦合振动分析,对比分析双车交会情况下车辆和桥梁的响应,讨论双车间距、风速、车速等因素的影响。研究表明双车交会时背风侧车辆风荷载突变使车辆的横向响应显著增大。     

根据随机交通状况修正横截面尺寸的大跨桥梁的风致性能

现有的交通状况对细长大跨桥梁(SLB)面板主要影响有两类:1)桥梁横截面尺寸发生改变,这可能会反过来改变颤振导数及作用在桥梁上的风致气动弹性荷载;2)作用于桥梁上的附加动力荷载,包括来自于车辆的动力相互作用。与外部动力荷载——车辆相比,通过改变桥梁横截面尺寸来研究其影响是很少见的。在桥面板上分布车辆模型,在风洞实验室模拟随机交通流对按比例制作的桥梁截面模型进行试验。在风洞试验中通过改变桥梁的横截面尺寸来获得不同的颤振导数,目前的研究是从数值上评估其对大跨桥梁的风致性能,如气动弹性性能、风致响应和潜在疲劳累积性能的影响。     

Experimental study of aerodynamic interference effects on aerostatic coefficients of twin deck bridges

The aerodynamic interference effects on aerostatic coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test. The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks. The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck. The drag coefficients of a windward deck decrease slightly compared with that of a single deck. The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks. And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected. __________ Translated from Journal of Hunan University (Natural Science), 2008, 35(1): 16–20 [译自: 湖南大学学报(自然科学版)]     

侧风作用下静动态车-桥系统气动特性数值模拟研究

我国现阶段正处于轨道交通建设的高峰时期,线路中桥梁占有相当大的比重,车辆在桥梁上运行时构成车-桥系统共同承受侧向风的作用,车辆和桥梁间存在着显著的相互气动影响。基于数值模拟方法,对侧向风作用下车-桥体系的空气绕流场进行静动态模拟分析,将静态数值模拟气动力系数与风洞试验结果进行对比,基于动态气动统流特性,提出将桥面上方流场分为6个特征区域,并进一步分析风速和车速对车-桥系统气动特性的影响。分析表明,体系绕流状态具有三维特性,气动力随着车速和风速变化显著。研究结论对车-桥系统绕流及静动态气动荷载的确定具有一定的参考价值。     

Investigations concerning seismic response control of self-anchored suspension bridge with MR dampers

To mitigate the seismic response of self-anchored suspension bridges, equations of motion governing the coupled system of bridge-magneto-rheological (MR) dampers subject to seismic excitation are formulated by employing the phenomenological model of MR dampers. A corresponding computer program is developed and employed for studying the seismic response control of a self-anchored suspension bridge with a main span of 350 m. The effect of variable current and number of dampers on seismic response control is investigated. The numerical results indicate the longitudinal displacement of the tower top and bridge girder decrease with the increase in input current and number of MR dampers attached longitudinally at the tower-girder connections, and the internal forces of the tower are effectively attenuated as well. It appears that small electronic current (0.5 A in this study) may sufficiently attenuate the seismic responses for practical engineering applications. __________ Translated from China Civil Engineering Journal, 2006, 39(11): 84–89 [译自: 土木工程学报]