Dynamic behavior of hybrid framed arch railway bridge under moving trains

In this study, the dynamic behavior of a concrete-filled steel tube (CFST) hybrid framed arch railway bridge under moving trains are investigated through an in-site dynamic test. The bridge was tested under train loadings in different scenarios and at different speeds of the trains. The free vibration characteristics, strain, displacement, and acceleration of the bridge structure were measured to evaluate the dynamic responses of the train-bridge coupling system. A three-dimensional finite element model, which took into account the train-bridge coupling and track irregularities, was established to analyze the behaviors of the train-bridge system. The model was validated against the in situ test results. The impact effect on the girder was greater than that of the arch frame. The acceleration responses of the trains on the bridge increased with the train’s speed. The riding comfort of the trains was evaluated based on the measured dynamic responses of trains.     

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。     

京通线烟囱沟桥上列车走行安全性、舒适性及平稳性分析

指出了国内外在列车—桥梁时变系统空间振动计算中存在的不足,并提出了改进办法。诠释了桥上列车走行安全性的含义。基于桥上列车脱轨力学机理,提出了桥上列车走行安全性、舒适性及平稳性的计算原理。阐述了系统运动稳定性的判别准则。根据列车脱轨能量随机分析理论及列车—桥梁时变系统空间振动计算模型,对京通线烟囱沟桥上列车走行安全性、舒适性及平稳性进行了计算,并对其计算结果进行了分析。由于该桥跨中横向水平振幅达到8.465mm,晃动较大,文中最后还对该桥提出了限速建议值。     

横向紊流风作用下桁架梁上高速列车抖振力空间相关性试验研究

为分析横风作用下钢桁梁上高速列车受到抖振力的空间相关性,在XNJD-3风洞实验室建立了两种大气紊流场,基于1∶29.7的车桥节段模型,采用同步测压法得到了静止列车上的抖振力分布,尝试从时域、频域两个方面分析攻角、紊流场、列车位置等参数对列车抖振力空间相关性的影响,并对试验现象及影响因素总结,提出了列车抖振力跨向相干函数的拟合公式,证实了列车侧向抖振力的相关性与顺风向脉动风的相关性较接近,升力和力矩的相关性略小于竖向脉动风的相关性,也指出了进一步的研究方向,研究结论对类似桥梁上列车运行的舒适性研究具有指导意义。     

Fatigue assessment of a composite railway bridge for high speed trains. Part I: Modeling and fatigue critical details

Steel bridges for high speed trains may sustain excessive fatigue damage due to stronger dynamic effects induced by the increased train speed. Dynamic tests were carried out on a composite railway bridge for high speed trains. A detailed finite element (FE) model of the bridge was established and validated by the dynamic test results. Six types of structural details in the bridge were considered for fatigue evaluation. The stress history of each concerned detail during a single train passage was generated by the validated FE model. The stress spectrum, obtained through Rainflow cycle counting of stress history, was used to calculate the fatigue damage of each detail, based on the detail category specified S–N design curve and the Palmgren–Miner damage rule. Among various structural details, the load carrying fillet weld around the gusset plate of the diagonal bracing at the bridge bearing is predicted to be the most fatigue critical detail. In this paper, a general methodology for determination of fatigue critical details is presented, which can serve as a basis of enhanced fatigue evaluation by using local stress approaches. In “Part II: conditions for which a dynamic analysis is needed” as the continuation of this paper, fatigue assessment will be investigated based on the dynamic stresses predicted by different approaches, i.e. static analysis considering dynamic amplification factor, direct dynamic analysis with a moving load model or a train–bridge interaction model.     

An analytical approach to train-induced site vibration around Shinkansen viaducts

This study is intended to establish an analytical approach to evaluate the site vibration caused by the passage of bullet trains over Shinkansen viaducts. In this approach, to simplify the problem the entire train–bridge–ground interaction system is divided into two subsystems: train–bridge interaction and foundation–ground interaction. In the train–bridge interaction problem, the analytical programme to simulate the traffic-induced bridge vibration is developed. Then, the dynamic responses of the viaducts are calculated to obtain the dynamic reaction forces at the bottoms of the piers. Applying these reaction forces as input excitation forces in the foundation–ground interaction problem, the site vibration around the viaducts is simulated and evaluated using a general-purpose programme.     

Development of an experimental facility for measuring pressure waves generated by high-speed trains

An experimental facility was developed for investigating pressure waves generated by high-speed trains. The facility launches a 1/30 scale model conforming to the actual shape of the train and enables measurements to be carried out with the same geometric configurations at full scale. The train models are launched using compressed air. A mathematical model is developed to predict the performance of the experimental facility. This model allows the optimum values of the design parameters of the facility to be determined in order to achieve a given target velocity and to control the launching velocity by adjusting the pressure of the compressed air. Measurement of the flow in the experimental facility shows that the facility performs as designed by the mathematical model and is capable of launching a train model at velocities greater than 500 km/h. Pressure waves generated by a train moving into a tunnel are measured, and the experimental data agree well with field measurements. The effect of the train nose on the strength and form of the pressure waves is also discussed.     

高速列车与铁路简支梁桥动力相互作用研究

通过有限元分析软件建立桥梁有限元模型,以移动车轮加簧上质量模拟车辆,对不同工况下高速行驶的列车与简支桥梁的动力响应进行了研究和比较,得出了高速列车与桥梁系统的一些动力响应特性。     

大型桥梁行车振动舒适性的烦恼率模型研究

针对目前国内外对行车振动舒适性的度量及具体判定上还有一定的模糊性,迫切需要定量化的评价方法.本文结合振动舒适度标准和国际上公认的振动舒适度实验,分析了概念隶属度值和相应的振动加速度对数值之间的关系,给出了烦恼率计算公式,提出了烦恼率的近似拟合曲线,并把烦恼率作为行车振动舒适性的量化指标,提出评价行车振动舒适性较精确的量...     

Monitoring and analysis of combustion aerosol emissions from fast moving diesel trains

In this paper we report the results of the detailed monitoring and analysis of combustion emissions from fast moving diesel trains. A new highly efficient monitoring methodology is proposed based on the measurements of the total number concentration (TNC) of combustion aerosols at a fixed point (on a bridge overpassing the railway) inside the violently mixing zone created by a fast moving train. Applicability conditions for the proposed methodology are presented, discussed and linked to the formation of the stable and uniform mixing zone. In particular, it is demonstrated that if such a mixing zone is formed, the monitoring results are highly consistent, repeatable (with typically negligible statistical errors and dispersion), stable with respect to the external atmospheric turbulence and result in an unusual pattern of the aerosol evolution with two or three distinct TNC maximums. It is also shown that the stability and uniformity of the created mixing zone (as well as the repeatability of the monitoring results) increase with increasing length of the train (with an estimated critical train length of ~ 10 carriages, at the speed of ~ 150 km/h). The analysis of the obtained evolutionary dependencies of aerosol TNC suggests that the major possible mechanisms responsible for the formation of the distinct concentration maximums are condensation (the second maximum) and thermal fragmentation of solid nanoparticle aggregates (third maximum). The obtained results and the new methodology will be important for monitoring and analysis of combustion emissions from fast moving trains, and for the determination of the impact of rail networks on the atmospheric environment and human exposure to combustion emissions.     

An investigation of the aerodynamic admittances and aerodynamic weighting functions of trains

Increasing train speeds combined with the predicted reduction in the weight of new trains ensure that the effect of crosswinds on train stability is of continued interest to the rail industry. Changes in the approaching wind velocity can in turn lead to changes in both the lift and side force on a vehicle. Calculations of the wind induced force can either be undertaken in the frequency domain with knowledge of aerodynamic admittance characteristics or in the time domain using aerodynamic weighting functions. This paper investigates the applicability of developing a universal aerodynamic admittance function and a corresponding analytical weighting function for a variety of train types based on a range of experimental data. It is suggested that only two variables are required to parameterise both the admittance and weighting functions. It is also argued that for certain train types one of these variables can be considered as a constant across a wide range of yaw angles.     

大跨度连续梁拱组合桥列车走行性分析

指出连续梁拱组合桥的受力特性,介绍了列车安全性、舒适性及平稳性的基本涵义及评价标准,并基于列车—桥梁时变系统空间振动计算模型,对温福线昆阳特大桥列车走行安全性、舒适性及平稳性进行了计算和分析。     

Determination of the critical loading conditions for bridges under crossing trains

A procedure based on experimental and theoretical analyses to identify critical loading conditions on existing metallic railway bridges is presented. This method requires knowledge of the principal modal frequencies, and for this reason, a consolidated and simple procedure to study the bridge dynamics is herein explained. This consists of: preliminary studies; material and dynamic tests; and identification techniques to identify modal parameters and eventual non-linear behaviours. Generally the information collected can be used both to calibrate the bridge model and to obtain the refined frequency response function. In order to avoid high computational effort due to long time-history dynamic analyses by using the bridge model subjected to a series of train crossings, a new frequency domain approach for the identification of critical loading conditions is proposed. Evidence of the influence of the axle spacing and velocity of the vehicle on the dynamic magnification due to the train crossing is shown. The method is based on the construction of an excitation spectrum related to the train axle spacing and the velocity, given the weight of the vehicle. Comparison of the excitation spectrum with the frequency response function allows identification of the load patterns that bring the bridge to resonance conditions and might threaten bridge stability, bearing in mind continual changes in train technology.     

Impact of track irregularities and damping on the fatigue damage of a railway bridge deck slab

The structural response of reinforced concrete slabs in railway bridges is strongly influenced by local dynamic effects and, therefore, detailed calculations of internal forces have to be performed for a realistic fatigue assessment. In this context, this paper discusses the influence of track irregularities and modal damping coefficients in the dynamic response and fatigue behaviour of a railway bridge deck slab. For that purpose, track irregularities were measured (at different instants of time) and damping coefficients were determined based on acceleration records for passing trains in a real bridge. The bridge behaviour was calculated using a train–bridge interaction methodology, considering calibrated numerical models of the viaduct and the train. The fatigue damage was quantified through the linear damage accumulation method. This methodology allowed to understand the way track irregularities and damping coefficients affect the magnitude of applied bending moments and fatigue damage in the slab.     

龙卷风作用下高速列车的运行安全性评估

随着我国铁路线网密度的加大以及龙卷风等极端天气出现的频次增多,列车遭受龙卷风袭击的风险不断增加。利用物理模拟器对列车进行测压试验,通过试验得到的气动力对龙卷风作用下高速列车的运行安全性进行评估。结果表明:受龙卷风气压降和水平风速的共同影响,列车距龙卷风中心不同相对位置时,所受风荷载作用机制明显不同;迎风侧轮轨横向力主要由侧力产生,风速较大时,升力和侧滚力矩对轮轨垂向力的贡献增大;横向力、脱轨系数、轮重减载率等列车运行安全性指标随径向距离的增大先增大后减小;列车运行安全性指标随风速、车速的增大而增大,列车安全运行的龙卷风临界风速值随车速的增大而急剧减小,其中,当车速为350km/h时,轮对横向力对应的临界风速仅为11.06m/s。     

包西铁路128m钢管混凝土系杆拱动力性能分析

以200km／h时速客货共线128m钢管混凝土拱为研究对象,采用空间有限元分析模型,计算了桥梁的自振特性,详细探讨了横撑刚度和拱肋截面形式对桥梁自振特性的影响,评价了桥梁的动力性能和列车运行的安全性与舒适性。     

移动荷载作用下大跨度铁路斜拉桥纵向共振机理

列车荷载作用下铁路斜拉桥将在不同方向上发生振动,列车竖向荷载作用下导致的主梁纵向振动将影响道床稳定性和伸缩装置的使用,甚至影响行车安全性和舒适性。采用等效纵向荷载研究移动荷载作用下斜拉桥纵向振动机理,推导纵向共振速度估算公式。以一大跨度铁路斜拉桥为实例,分析了不同速度的移动荷载作用下结构动力响应。结果表明,当移动荷载速度与估算纵向共振速度接近时,移动荷载通过桥梁时的纵向加载频率与桥梁一阶纵向振动频率接近,斜拉桥发生纵向共振现象,主梁和桥塔动力响应显著增大。     

A multidisciplinary approach for fatigue assessment of a steel–concrete high-speed railway bridge on Sesia river

Steel–concrete composite bridge solutions have been more and more exploited in the new high-speed (HS) lines of European railway networks. New design solutions, introduced during a period of quick expansion for railway networks, amplified open problems related to dynamic effects, train–bridge interaction phenomena, fatigue loadings, structural modelling, fatigue life and comfort. In this article, results obtained by long-term dynamic monitoring of Sesia viaduct, a medium span double-box composite bridge of the new Italian HS network, are described and analysed. Structural modal properties were determined in order to evaluate the real-time dynamic behaviour and its correlation with environmental conditions. A suitable numerical procedure was then implemented in order to identify typology, length and velocity of trains crossing the bridge, to evaluate the intensity of deck vertical accelerations as a function of train speed and to obtain a reliable evaluation of real traffic spectra. A final fatigue assessment on welded connections was executed evaluating fatigue spectra by the aforementioned real traffic spectra and assuming S–N curves obtained by suitably executed experimental tests.     

Strengthening of a steel railway bridge and its impact on the dynamic response to passing trains

Two different strengthening methods for a through-girder steel railway bridge are investigated. The studied structure is the Söderström Bridge, located in the city of Stockholm, Sweden. Due to fatigue problems, it is in need of assessment and strengthening. In one of the methods, arches are added under the bridge modifying the structural system and lowering the stress ranges for all structural members. The other method consists of prestressing the floor beams. This increases their stiffness and transforms the mean stress in the lower flanges from tension to compression. A 3D finite element model is created and verified with measurements. The different strengthening methods are tested in the model by dynamic analysis with moving train loads. The strengthening methods show some positive effect concerning the fatigue life. Changes in vertical bridge deck acceleration for high speed traffic are also presented. A comparison between the European code and the Swedish code regarding vertical bridge deck acceleration levels for high speed traffic shows large differences for the bridge.     

跨高铁桥梁设计及施工

随着我国高速铁路的快速发展,跨越既有高速铁路的桥梁越来越多.由于铁路建筑界限及安全的要求,与跨越普通铁路的桥梁相比,跨高铁桥梁的跨径一般都较大.研究跨高铁桥梁设计及施工,供类似工程参考.