为了解试验模拟的地表粗糙度偏差对方形结构风荷载的影响,在风洞中模拟不同缩尺比的A、B两类粗糙度指数风场,研究Jensen数分别为1200、6000时结构风荷载的Jensen数效应.结果表明:Jensen数变化对平均风荷载影响很小,对脉动风荷载影响较大;Jensen数由6000减小到1200时,顺风向、横风向、扭矩脉动风荷载增大幅度约为200％～250％;Jensen数减小会使风荷载功率谱低频段能量呈小幅增大趋势,高频段能量呈小幅减小趋势;当来流与方形结构的直线边存在一定夹角时,Jensen数变化对各类型风荷载相关性影响变小;Jensen数增大会使各层间顺风向、横风向与扭矩风荷载相关性减小;Jensen数由1200增大为6000时,对扭矩风荷载相关性影响最大,降幅为63％,横风向风荷载相关性最大降幅为40％,顺风向风荷载相关性最大降幅为15％;增大Jensen数会使顺风向风荷载相干函数与Davenport指数衰减形式吻合的频率范围增大,高频部分的竖向相干函数减小;横风向风荷载与扭矩风荷载竖向相干函数更符合Davenport指数衰减形式.

Increasing the surface roughness of structures is an effective method to suppress the Reynolds number effect of the approximate streamlined bridge.The deck railing, maintenance track and other ancillary facilities can change the appearance of the bridge and increase the'roughness' of the approximate streamlined cross-section.In this paper, the impacts of the deck railing, maintenance track and other ancillary facilities on the Reynolds number effect of the approximate streamlined bridge cross-section are studied via large-scale model wind tunnel test of force and pressure measurements.The results show that the maintenance track can increase the Reynolds number effect of the drag coefficient of the streamlined bridge under the condition of 0°wind attack angle and suppress the Reynolds number effect of the drag coefficient at the other wind attack angles.The impact of the railing on the Reynolds number effect of the drag coefficient is small.The impact of the maintenance track and railing on the Reynolds number effect of the lift coefficient at negative wind attack angles is very small.The maintenance track can suppress the Reynolds number effect of the lift coefficient at positive wind attack angles and the deck railing can increase the Reynolds number effect of the lift coefficient at positive wind attack angles.Both the maintenance track and the railing can suppress the Reynolds number effect of the lifting moment coefficient at negative wind attack angles and increase the Reynolds number effect of the pitch moment coefficient at positive wind attack angles.In order to reduce the impact of the Reynolds number effect, the critical Reynolds number critical of the cylinder should be avoided as far as possible in wind tunnel test.

风洞试验时紊流风特性参数的模拟精度会对桥梁结构的抖振、颤振、涡振等试验结果产生影响, 为了提高试验精度, 分析紊流风特性参数模拟误差所带来的影响、总结桥梁结构表面风压分布受紊流风参数的影响规律, 在风洞中采用格栅紊流, 分别形成了紊流强度相同但积分尺度不同与积分尺度相同但紊流强度不同的几种局部紊流风场,以此来研究紊流风特性参数单独变化对桥梁结构表面风压分布规律的影响.结果表明: 紊流强度增大会使桥梁表面平均风压系数绝对值减小, 减小的幅度会受结构表面位置、风攻角等因素的影响.当位置或风攻角发生变化后, 紊流强度增大导致平均风压系数绝对值减小的幅度也会发生变化, 很难进行定量修正.大部分位置的脉动风压系数会随紊流强度增大而增大.但受栏杆、风嘴、检修车轨道等附属结构影响, 这种趋势可能出现相反的变化.紊流积分尺度增大会使近流线形桥梁表面平均风荷载增大, 对脉动风荷载影响很小.进行桥梁气弹模型试验时, 应首先保证准确模拟紊流强度, 在条件许可的情况下再准确模拟紊流积分尺度.积分尺度越小, 表面压力相关系数也越小.相邻位置的脉动风压相关系数主要受特征紊流影响, 与来流的积分尺度无关.

紊流风特性参数如紊流强度与紊流积分尺度的试验模拟精度会影响风洞试验结果,导致不同的风振响应.为得到影响规律,分析了紊流风特性参数对方形结构表面脉动风荷载的影响.为减小干扰因素,利用格栅形成局部紊流场,在此流场中研究紊流强度或紊流积分尺度单参数变化,其它参数不变对结构表面脉动风荷载分布规律的影响.结果表明:方形结构底部区域的概率分布曲线与高斯分布吻合较好,随来流紊流强度增大,分布曲线较高斯分布偏移幅度有增大趋势.紊流强度增大会导致脉动风压系数增大,方形结构迎风面中上部区域对紊流强度非常敏感.紊流积分尺度对脉动风压系数的影响很小,来流积分尺度越大,水平相关性与竖向相关性越好.

Super long-span bridges provide people with great convenience, but they also bring traffic safety problems caused by strong wind owing to their high decks. In this paper, the large eddy simulation together with dynamic mesh technology in computational fluid dynamics (CFD) is used to explore the mechanism of a moving vehicle's transient aerodynamic force in crosswind, the regularity and mechanism of the vehicle's aerodynamic forces when it passes through a bridge tower's wake zone in crosswind. By comparing the calculated results and those from wind tunnel tests, the reliability of the methods used in the paper is verified on a moving vehicle's aerodynamic forces in a bridge tower's wake region. A vehicle's aerodynamic force coefficient decreases sharply when it enters into the wake region, and reaches its minimum on the leeward of the bridge tower where exists a backflow region. When a vehicle moves on the outermost lane on the windward direction and just passes through the backflow region, it will suffer from negative lateral aerodynamic force and yaw moment in the bridge tower's wake zone. And the vehicle's passing ruins the original vortex structure there, resulting in that the lateral wind on the right side of the bridge tower does not change its direction but directly impact on the vehicle's windward. So when the vehicle leaves from the backflow region, it will suffer stronger aerodynamic than that borne by the vehicle when it just enters into the region. Other cases of vehicle moving on different lane and different directions were also discussed thoroughly. The results show that the vehicle's pneumatic safety performance is evidently better than that of a vehicle on the outermost lane on the windward.

Based on a wind-vehicle-bridge analysis system and quasi-steady pneumatic force coefficient data obtained from wind tunnel tests, the problem of moving vehicles on a cable-stayed bridge deck overturning in a strong wind environment is studied, with the probability evaluation as the emphasis. It is put forward that the evaluation of a vehicle's overturning is a probability problem that a stochastic process overpasses a threshold level, and the influence of the statistic process characteristics of excitations on driving safety is profoundly discussed in the paper. The analysis shows that the higher the driving speed, the more obvious the effect of statistic process characteristics tends to be. Moreover, the influence degree of stochastic process characteristics is relevant to the wind velocity range of the dynamic reliability curve and the range of the probability distribution for the mean wind velocity. When the range of the former is broad enough and overlaps with the range of the latter, the influence of stochastic process characteristics should be considered. Wind barriers can promote a safe driving velocity from 80 to 100 km/h under normal weather conditions. Under extreme weather conditions, traffic control measures should be implemented to maintain the bridge's traffic service. Wind barriers together with the speed limitation (80 km/h) can ensure that a truck passes the bridge safely during storm conditions (24.5 m/s, Beaufort Scale 10). When the natural wind is a violent storm (28.5 m/s, Beaufort Scale 11), the speed limitation should be 60 km/h. (C) 2014 American Society of Civil Engineers.

Based on Zhijiang Bridge in Hangzhou,the dynamic characteristics and Multiple T uned Mass Dampers(MTMD) control method of wind-induced vibration for the arch steel tower of cable-stayed bridge were studied.Using software ANSYS, the dynamic characteristics of arch steel tower under construction and service status were analyzed.The control objectives of the vibration modes and frequenc y of the arch steel tower were suggested.Perfect stochastic fluctuating wind fi eld processes were generated by improved WAWS.With the wind vibration response reduction ratios of the displacement and acceleration at the top of arch steel t ower as optimization objectives,the parameters of MTMD system were optimized an d the Tuned Mass Damper(TMD) devices and parameters which could control the pla ne vibration and out-of-plane vibration for arch steel tower were designed.Th e results show that the control efficiency of MTMD system has much to do wit h its parameters,and MTMD system has optimum parameter combinations.Wh en the arch steel tower is under construction,especially at non-closure stage, (the most disadvantageous state of wind vibration),the parameter combinations for MTMD system are suggested: the mass ratio is 0.01,the number of TMD is 12, the damping ratio is 0.05 and the bandwidth is 0.1.The parameters in MTMD sy stem have a consistent vibration reduction effect on structural displacement and acceleration.In general,the vibration reduction ratio of acceleration is grea ter than that of displacement.

The formation of two lock-in districts of vertical vortex-induced vibration of a box bridge deck section was investigated via the amplitude response and surface pressure time-histories obtained by synchronizing vibration and surface pressure measurement in the uniform flow wind tunnel test.The relationship between amplitude and wind velocity,means and standard deviations of surface pressure coefficient,correlation coefficient between local lift force and total lift force,contribution of the local lift force to vertical vortex-induced vibration were studied.The results show that the lock-in district of high wind speed vertical vortex response is wider than that of low wind speed vertical vortex response,and the amplitude of high wind speed vertical vortex response is larger than that of low wind speed vertical vortex response.It is considered that the cause of two vertical vortex shedding response results from two different vortex shedding with a respective Strouhal number of 0.145 and 0.082.Vortex-induced forces of low wind vertical vortex response come mainly from the airflow fluctuation at 2 guard rails's area of the middle upper surface and back pressure zone of the lower surface,vortex vortex-induced forces of high wind vertical vortex response come mainly from the airflow fluctuation at the downstream zone of the upper surface and back pressure zone of the lower surface,and the vortex shedding at their upper surface are significantly different.The research results have general applicability for some typical blunt box girder sections,and the research methods can provide a reference for similar studies.

The longitudinal vibration of suspension bridge stiffening girder was simplified as some independent single degree of freedom vibration systems.Stochastic vibration theory was used,and earthquake excitation was simplified as stationary white-noise excitation,the analytical expression of absolute acceleration mean square for stiffening girder longitudinal vibration was deduced.According to the principle of derivative extremum,the minimum absolute acceleration mean square and the corresponding system optimum damping ratio were derived,and the analytical expression of optimum damping coefficient for suspension bridge linear fluid viscous damper was got.A suspension bridge was selected as example,parametric sensitivity study was carried out based on dynamic time-historical method,and the reliability of the analytical expression was verified.Analysis result shows that the theoretical optimum damping ratio of suspension bridge linear fluid viscous damper is 0.5,and the efficiency of damper reaches its maximum with the corresponding optimum damping coefficient.When damping ratio is 0.3,damper efficiency is about 90% of optimum damping ratio.When damping ratio is 0.4-0.6,damper efficiency is 99% of optimum damping ratio,so the optimum damping coefficient of linear fluid viscous damper can be adjusted properly in the range according to earthquake intensity,damper stroke and cost.

In truss structures, the aerostatic drag coefficients are different between trusses in windward and leeward due to the shielding effect. To solve this problem, the shielding factor is introduced in Wind-resistant Design Specification for Highway Bridges (2004) of China which refers to BS5400-1 (1988) of British Standard. But it doesn’t take the shielding factors of non-zero wind attack angles into consideration in these two specifications. When calculating the shielding factor of the truss girder bridge which has a bridge deck system, it is necessary to add the height of bridge deck pavement into the windward truss and to include the windward area of bridge deck pavement to the overall truss for calculating the spacing ratio and the solidity ratio. Based on pressure coefficients from 24 measurement points, the shielding factors for different wind attack angles (from -10° to 10°) can generally be obtained. The results show that the shielding factor decreases with increasingly different wind attack angle and a ‘linear’ fit equation is demonstrated as a possible way to find the shielding factor of truss girder bridges.

In order to investigate the aerodynamic interference effects between parallel bridges, the aerodynamic interference effects on aerostatic coefficients of double thin-walled hollow pier in the parallel continuous rigid frame bridges with high-pier and long-span were investigated in details by means of wind tunnel test. The tandem interval and side-by-side interval between the two piers and wind direction angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin piers. The test got aerostatic coefficients of 10 conditions. The research results have shown that the aerodynamic interference effects on aerostatic coefficients of double thin-walled hollow pier in parallel bridges can not be ignored. The tandem interval and side-by-side interval between the two piers and wind direction angles are important factors affecting interference effects. The drag coefficient, lateral force coefficient and torque coefficient are affected by these factors.

Against the problem of the aerodynamic interference effects on aerostatic coefficients between parallel continuous rigid frame bridges with high-pier and long-span, the aerodynamic interference effects on aerostatic coefficients of main beam in the parallel long-span continuous rigid frame bridges were investigated in details by means of wind tunnel test. The space between the two main beams and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of main beam. The test got aerostatic coefficients of 10 conditions. The research results have shown that the aerodynamic interference effects on aerostatic coefficients of main beam in parallel bridges can not be ignored. The aerodynamic interference effects on parallel bridge main beam is shown mainly as follows: The drag coefficient of main beam downstream dropped and the drag coefficient of main beam upstream changed but not change significantly. There are also the aerodynamic interference effects of lateral force coefficient and torque coefficient between the main beams upstream and downstream. The effects upstream are smaller and the effects downstream are larger.

The plate type elastomeric pad bearing is the most commonly used in highway bridge bearings. In the seismic design of bridges, the horizontal rigidity of the bearing is an important calculation parameters. The specific values of each parameter in the formula are not clear, and it can not provide a clear computation measures, although the formula of horizontal rigidity is given in the specification. Against Series bearings in plate type elastomeric pad bearing for Highway Bridge (JT/T4-2004), the People's Republic of China Communications Industry Standard, the structural parameters of the bearing are systematically introduced, including the shape factor, the bearing thickness, the thickness of the single-layer rubber and the total thickness of rubber layer. The methodology and detailed steps of the bearing horizontal rigidity are then analyzed and summarized by the formulas above. At last several examples of the different type of bearings are given. Some reference are Provided for the calculation of the stiffness frequently of plate type elastomeric pad bearing which are frequently used for highway bridges.

The effects of the stochastic progress characteristics of turbulent wind and road roughness on driving safety reliability of a vehicle were discussed,and the evaluation method for safety probability of a vehicle driving on a bridge deck was studied considering the randomness of mean wind velocity as well as the stochastic progress characteristics of turbulent wind.The effects of the stochastic progress characteristics were analyzed with the classical dynamic reliability theory.The results showed that contacting forces of vehicle tires are weak non-stationary progress within lateral wind environment,so the classical dynamic reliability theory is applicable to safety reliability analysis of driving vehicles;the higher the driving speed,the more obvious the effect of the stochastic progress characteristics;driving reliability of a Santana representing small cars is influenced more than that of box-type truck by the stochastic progress characteristics;the level of the effect is relevant to the wind velocity range of dynamic reliability curve and that of probability density function of mean wind velocity.

In order to study mathematically the dynamic magnification factors of a suspension large bridge,the current vehicle-bridge coupling vibration analysis system under highway stochastic traffic flow was improved,and the random simulation technology of multi-path surface roughness was built.The dynamic equations of multi-axle vehicles were deduced and further embedded into the vehicle-bridge coupling vibration analysis system.The random simulation technology of multi-path surface roughness was studied,and fast Fourier transform was used to promote the efficiency of the harmonic wave synthesis algorithm.The impact effect of traffic flow on the large bridge was analyzed and the influence of vehicle-bridge coupling vibration effect was discussed.The results show that the impact effect of traffic flow on suspension bridges is obvious and the coupling vibration effect leads to the phase variation of the vibration responses.However,with regard to the bridge main beam,coupling effect does not make vibration amplitude increase significantly.It is more reasonable to take the values of the dynamic magnification factors of a large suspension bridge according to BS 5400 or OHBDC.1982.The influence of driving velocity on dynamic magnification factors is evident.

The Lead-Rubber-Bearing is a type of isolation device in entirety. Its design parameter is complicated. when it is used in bridges, it always need plenty of time to design. It is not beneficial to its application and dissemination. The design formula now available are lack of relevance，can not provide a clear and distinct computation measure. This paper explains in a systematic way the formula and reasonable value range of the design parameter. These parameters include the diameter and height of lead pin, effective design deflection, the equivalent linear model, shear strain of rubber bearing shear stress of the lead，initial rigidity and second rigidity and so on. At last this paper induces computing method of equivalent rigidity and equivalent damping constant and gives some examples。This paper gives scientific basis for the concrete design and makes the bearing standard and serial to lay a foundation for its application.

It's important to identify structural modal parameters, especially, accurate modal shapes in time domain for accurate damage identification and health monitoring of structures. The natural excitation vibration is used to identify the structural modal parameters. The power spectral density curve has obtained according to the measuring point vibration time domain curve, and then natural frequencies and vibration value are determined by the curve peak. The reference point is taken for the vibration unit values to normalize other modal shapes. The modal shapes are calculated using the phase measuring point relative to a reference point. After the finite element analysis and calculation, and the measured modal is compared with it. The results show that the dynamic performance of the bridge is reliable because the measurement method and the finite element method are basically consistent. The damping ratio of the bridge is larger dispersion but the average damping ratio is in line with the rules and scope of the cable-stayed bridge.

Taking Sanshui river bridge as an engineering background,the wind field characteristics of the bridge site located in the west valley region were derived through the wind tunnel test of a terrain model.The changes of wind speed profile,turbulence intensity,turbulence integral scale and turbulence spectrum in different wind directions in west valley region were analysed.According to the similarity relation related to the gradient wind speed,and referencing the gradient wind speed stipulated in the wind-resistant design code,a method of calculating design wind speed of bridge in agreement with the wind speed profile and the magnitude of the gradient wind speed measured at the bridge site in wind tunnel test was proposed.Test results show that the wind speed profile is of a power-law distribution,when the coming wind is parallel to the trend of the valley.The wind speed profile in other directions cannot be simulated by a uniform power-law relationship.The power exponent of wind speed profile parallel to the trend of the valley is less than those in other directions,and the value is equal to 0.142.The intensity of turbulence in the valley is the largest,especially near the side slope,and the value is bigger than 15% at the upper part of bridge deck near midspan.The wind speed is attenuated rather than amplified compared to the coming wind speed.Because the bridge is located in the valley,so the bridge site has no notable magnification effect on wind speed.When considering the turbulence integral scale and turbulence spectrum,the shape of mountain on both sides should be taken into account.

The vibration damping measures may affect the static stability of the structure.Taking a bridge as the engineering background,through the section model wind tunnel test,the influence of vibration damping measures on three-component force coefficients of the structure was studied to improve the structural characteristics.The influence factors include the central stabilizer,baluster drafty rate,windbreak,and vehicle,the 13 working conditions were simulated.The results show that the changes of three-component force coefficients affect the static wind loads directly,and the influence of changes of these parameters on the static wind load cannot be ignored.The different setting method of central stabilizer has a significant influence on the static three component coefficient of the girder.The central stabilizer setting on board alone has a significant increase of drag coefficient,it is more than 100% at large wind attack angle.The central stabilizer setting on board and bottom of the girder has a small influence on the aerostatic factor.Windbreak has a significant increase to the draft coefficient of main girder.

In order to study the Reynolds number effect on vortex resonance of streamline-like bridge deck section,Reynolds number was changed by adjusting scale of model,and pressure taps were set on the surface of model.Amplitude and wind pressure time history of two models were recorded.Reynolds number effect on vibration frequency spectrum,moment coefficient time history and fluctuation pressure frequency spectrum were studied.Intrinsic reasons of Reynolds number effect on vortex was revealed.The investigation indicates that Reynolds number effect on pressure spectrum cause the Reynolds number effect on moment coefficient time history and cause Reynolds number effect on vibration frequency spectum,lead to Reynolds number effect on vortex resonance of streamline-like bridge deck section.1 tab,9 figs,11 refs.