参数化分析列车运行产生的路堤–地基振动

 为预测和分析高速列车运行产生的轨道和路堤振动及波动在沿线周围地基中的传播，利用2.5维有限元方法建立了轨道、路堤和下卧层地基在移动荷载作用下的动力耦合分析模型及无路堤情况下的轨道地基模型，求解三维地基的动力响应。对高速或低速运行的列车多轮重荷载产生的路堤和地基振动进行对比分析。通过参数化分析明确轨道刚度、路堤高度、地基土的剪切波速及阻尼系数、列车速度和振动频率等参数对地基振动和传播特性的影响。给出的方法和结论可用于分析软土地基上运行高速列车时的稳定性问题和评估列车运行对周围环境的振动影响。     

列车运行引起高架桥群桩基础地面振动分析

采用半解析数值方法分析列车运行引起高架桥群桩基础地面振动,研究合理设计桩基减小地面振动。半解析数值模型包括列车–轨道模型、高架桥模型、群桩模型。列车轨道模型中采用多质点弹簧–阻尼模型模拟列车,采用美国功率谱描述轨道随机不平顺,使用Euler梁模拟钢轨,采用Hertzian非线性公式描述轮轨接触,采用振型分解法求解轮轨作用力。铁路高架桥采用弹性支座简支梁模拟,采用传递系数矩阵和群桩影响因子分析桥墩下群桩的动力阻抗,根据桥墩的动力平衡方程求得桥墩–地基相互作用力,采用Green函数求得弹性半空间地面振动。研究铁路高架桥下群桩参数对地面振动的影响,分析不同桩长、桩直径、桩间距和轨道不平顺条件下地面振动速度1/3倍频程的大小。结果表明:轨道不平顺对桥墩作用力有较大影响,对小于6 Hz的地面振动影响较小,对大于6 Hz的地面振动影响较大。合适调整桥梁跨度与车速组合可减小地面振动。车速小于260 km/h时,桩径对地面振动影响较小;车速大于260 km/h时,增加桩径可减小地面振动。适当增加桩间距可避开振动增大区、减小地面振动随车速的增加。合理设计桩长可减小地面振动的增大区域。     

桥梁减振技术的发展与应用

介绍了既有铁路桥梁因横向刚度不足及列车提速致使的横向振动、城市桥梁轨道交通车桥耦合动力振动、大跨度桥梁拉索的风雨激振、轴向流激振等几类桥梁振动减振技术的发展与应用.在铁路桥梁和高架桥梁中,对车桥耦合振动体系,采用被动控制法,安装质量阻尼器,改变桥梁基础结构的型式,进行桥梁减振和降噪.在斜拉桥拉索减振上,主要采用机械减振控制,安装目前较常用的粘性剪切型阻尼器进行减振,介绍了新型的磁流变阻尼器半主动控制法减振技术.这些减振措施在一些实际的桥梁减振中都取得了不错的效果.同时,还阐述了近年来在人行桥梁中新发现的人致桥梁侧向振动的桥梁减振新问题.     

列车荷载作用下铁路斜拉桥索-梁相关振动研究

为了研究大跨度铁路斜拉桥的索-梁相关振动,基于拉索非线性振动理论,开发了有限元索动力单元,该单元在静力计算中为普通直杆单元,动力特性计算中可以计算拉索局部自振频率,动力时程计算中可以计算拉索非线性振动与整体结构振动的相互作用;编制了计算程序,建立了大跨度铁路斜拉桥有限元模型,同时使用索动力单元模拟斜拉索,最后研究了列车通过斜拉桥时梁、塔的带动下拉索发生索-梁相关振动的特性。结果表明:对于大跨度铁路斜拉桥,列车在设计速度范围内通过桥梁时索-梁相关振动不会导致拉索产生大幅振动。     

大跨度铁路悬索桥车-线-桥耦合振动分析

运用车辆-线路-桥梁耦合振动理论,建立相对完善的车辆-线路-桥梁耦合动力学模型。以某座主跨为1120m的悬索桥方案为工程背景,对该方案在ICE3列车以速度160～300km/h作用下桥梁、轨道和车辆的动力性能进行分析,并对主缆和吊索在不同索力下桥梁和车辆的动力响应进行对比研究。     

基于振源-传播模型的地铁引起地面振动数值预测

针对上海地铁运行引起地面振动的预测问题,应用振源模型计算不同车速对轨道基础的激振力,应用传播模型计算不同激振力输入下的地面振动加速度,建立了“地铁-隧道-土层”系统动力有限元模型。通过对比数值模拟结果与实测结果,分析了不同因素对地铁引起地面振动的影响规律。结果表明:随着地铁车速增加,振源激振力和地面振动加速度的幅值均明显增大;地面上距地铁中心线30 m范围内各点振动加速度峰值随距地铁中心线距离由近及远呈幂函数形式衰减;地面振动加速度频率主要为低频振动,随着距地铁中心线距离的增大,高频衰减相对于低频更为明显;建议上海地区建筑尽量在地铁中心线20 m范围外进行规划,或采取降低设计车速、减轻车辆荷载、优化隔振措施等方法,减少地铁运行引起地面振动对地面建筑及居民生活的影响。     

高速列车引起高架车站振动舒适度分析

针对京沪高铁沿线某高架火车站的振动舒适度问题,建立高架车站结构的有限元模型,充分考虑桥墩桩和土的相互作用,输入高铁列车的行驶荷载,计算结构振动在时域内的动力响应。基于目前常用的国际标准,评价各楼层的舒适度。     

Response of a train moving on multi-span railway bridges undergoing ground settlement

This paper presents an incremental-iterative procedure to investigate the influence of ground settlement on dynamic interactions of train–bridge system. The train is simulated as a sequence of identical sprung mass units with equal intervals and the bridge system as a series of simple beams with identical properties. To resolve the train-induced vibrations of a beam structure undergoing support settlement, this study decomposes the total beam response into two parts: the static response due to vertical support settlement and the dynamic component caused by inertia effect of beam vibration. An exact solution for static displacement is presented by exerting the support displacements on the beam statically. Thus the remaining dynamic response of the vehicle/bridge coupling system is solved by Galerkin’s method and computed using an iterative approach with Newmark’s finite difference formulas. Numerical studies indicate that for the dynamic interactions of train–bridge system, the inclusion of ground settlement is generally small on the bridge response, but it can amplify drastically the vertical response of the moving train, especially for the concave-up settlement profile. This conclusion is of significance in aligning a rail route that has to cross a region with local land subsidence.     

强夯加固粉土地基地面振动衰减规律研究

为研究强夯加固粉土地基地面振动衰减规律并确定强夯影响范围,依托济南-东营高速公路工程,对不同夯击能强夯加固粉土地基地面振动的速度幅值及振动频谱进行了现场测试,并基于测试数据通过量纲分析推导了强夯加固粉土地基地面振动衰减规律的计算公式。研究表明:(1)地面振动速度随距离增加呈现出不同的衰减区;(2)单击夯击能越大,强夯施工对邻近环境不利影响的范围越大,单击夯击能相同时夯击次数越多,对邻近环境影响范围越大;(3)地面振动衰减与夯击能和夯锤面积相关,随夯检距离呈负幂函数衰减,量纲分析推导出粉土地基地面振动衰减公式,经验证是合理的。     

基于2.5维有限元法分析横观各向同性地基上列车运行引起的地面振动

根据2.5维有限元原理,从横观各向同性土体弹性本构方程出发,推导出横观各向同性土体2.5维有限元弹性波动方程.轨道简化成铺设在横观各向同性地基上的Euler梁.在轨道方向的垂直截面上,将轨道结构和地基进行有限元离散,采用八节点单元,每个节点包含三个自由度,从而使复杂的三维问题转化为平面应变问题,再通过FFT逆变换将转换为沿轨道方向三维空间中的时域振动响应.分别基于上海和北京地区的典型土质参数,进行场地动力响应分析.结果表明:列车运行引起的北京地区场地的加速度响应幅值及位移响应幅值均大于上海地区场地;随着距轨道中心处距离的增加,两地区土体的动力响应频率均衰减到简谐荷载的自振频率周围,反映出横观各向同性土体的滤波作用;列车运行引起的地面振动衰减曲线会出现反弹增大的现象,其反弹特性及出现的位置与地基土体参数及列车运行速度密切相关.     

磁悬浮列车产生的地面振动及其对周围环境的影响

磁悬浮列车是一种新型的交通运输工具,但目前关于磁悬浮运行时所产生的地面振动和其对周围环境的影响还未见报道。首次对这一问题进行了系统的现场测试,分析了磁悬浮列车产生的振动特性。与其它交通工具产生的地面振动比较,结果表明,磁悬浮运行时产生的地面振动远小于一般轮轨运输工具产生的地面振动;并且当列车运行速度达到较高值时也不会像高速铁路那样出现地面振动急剧增大的现象。     

Dynamical identification and modelling of steel–concrete composite high-speed railway bridges

In the last few years, the construction of new high-speed (HS) railways across Europe, as well as in many other countries, has required many different bridges and viaducts. Together with classical concrete solutions, new steel–concrete composite typologies have been developed, giving light and cheap structures. Despite these studies and applications, some concerns still remain about the definition of reliable models for the evaluation of their actual dynamical behaviour under HS train passage. In particular, the influence of many structural and non-structural components, such as cross-girders and ballast, are still not well recognised. In this paper, open problems related to the dynamical assessment and modelling of new steel–concrete four-parallel-girder and box-girder solutions are exposed and analysed. A suitable procedure, based on operational modal analysis, model updating and train–bridge interaction analysis is applied to two bridges, recently built in the new Italian HS network, in order to assess and verify their dynamic behaviour under operative conditions.     

天津Z2线地铁运营对沿线地面振动的影响分析

天津滨海新区Z2线为新型地铁线路,有着列车运行速度快、发车频次高等特点,其地铁运营时速最高可达120km,而中国现阶段城市中运行的普通地铁列车时速一般在60～80km。高速地铁荷载与普通列车荷载相比,有着频率高、幅值大的特点,所造成的环境振动规律也有所不同。以天津市Z2地铁线一期工程作为实例,依托实际工程数据,利用大型通用有限元软件ABAQUS建立隧道–土层三维有限元模型,采用动力隐式分析模拟地基土高速移动地铁列车荷载下的地表振动强度衰减规律,比较不同盾构隧道埋深、不同地铁列车行车速度以及不同隧道上覆土层性质工况下的地表振动变化规律,并结合相关城市环境振动评估标准,对地铁造成的环境振动进行评价,初步得到了地铁线路环境振动防护距离随以上三种因素的变化规律。研究结论可为今后高速地铁线路工程建设选线以及运营沿线振动预测、地铁沿线规划提供一定指导。     

基于现场测试的列车引起地基振动分析

 对秦沈客运专线列车引起地基振动进行现场测试,通过对实测数据的时频分析,得到一个由轨道不平顺引起的基频。推导考虑轨道不平顺条件下列车动荷载的简化解析解,基于波数有限元理论推导动荷载作用下地基动力响应的柔度矩阵。以现场实测数据为依据,建立列车–轨道–地基振动模型,以推导的列车荷载为输入,计算轨道不平顺条件下列车运行引起的地基振动。分析不平顺幅值、波长以及车速对动态轮轨力的影响;研究层状地基上多轮荷载作用产生的动力响应,讨论车速变化对地基振动的影响。研究结果表明：所提出计算模型可以高效地预测轨道不平顺引起的地基振动;不平顺波长与列车运行速度一定时,轨道不平顺幅值越大,地基振动响应和轮轨作用力越大;不平顺幅值与列车运行速度一定时,不平顺波长越长,地基振动加速度和动态轮轨作用力越小;轨道不平顺波长与不平顺幅值一定时,车速越大振动加速度越大。     

Effectiveness of Soil–Structure Interaction and Dynamic Characteristics on Cable-Stayed Bridges Subjected to Multiple Support Excitation

The purpose of the study is to determine the effects of multiple support excitations (MSE) and soil–structure interaction (SSI) on the dynamic characteristics of cable-stayed bridges founded on pile foundation groups. In the design of these structures, it is important to consider the effects of spatial variability of earthquake ground motions. To do this, the time histories of the ground motions are generated based on the spatially varying ground motion components of incoherence, wave-passage, and site-response. The effects of SSI on the response of a bridge subjected to the MSE are numerically illustrated using a three-dimensional model of Quincy Bayview cable-stayed bridge in the USA. The soil around the pile is linearly elastic, homogeneous isotropic half space represented by dynamic impedance functions based on the Winkler model of soil reaction. Structural responses obtained from the dynamic analysis of the bridge system show the importance of the SSI and the MSE effects on the dynamic responses of cable-stayed bridges.     

Probabilistic assessment of the train running safety on a short-span high-speed railway bridge

In this work the running safety of high-speed trains on a short-span bridge is assessed. A probabilistic approach that combines Monte Carlo simulation with the extreme value theory is used and the existence of track irregularities is taken into account along with the variability of parameters related to the bridge, the track and the train. As case study, a 12 m span filler beam bridge was selected as the train–bridge interaction effects are most significant for short spans. The running safety is assessed for the case of loss of contact between the wheel and the rail, taking into consideration only the vertical wheel–rail interaction and assuming that no lateral forces act on the train. This research enables the characterisation of the wheel unloading coefficient, the identification of the critical wheel and also the definition of the maximum allowable speed for trains to run safely on the bridge.     

Seismic performance of isolated curved steel viaducts equipped with deck unseating prevention cable restrainers

This paper presents an in-depth analysis to evaluate the efficiency of using cable restrainers connecting isolated and non-isolated spans for preventing unseating of curved steel viaducts. For this purpose, the overall three-dimensional non-linear bridge response is examined in detail under the action of strong earthquake ground motions. The expected seismic vulnerability of bridge structures with curved deck geometries has been demonstrated, providing a refined estimation of seismic demands on most critical bridge components. The advantage of using a precise three-dimensional model has revealed the concentration of large seismic forces on specific steel bearing supports and cable restrainer units that greatly increase their failure possibility. Moreover, the unbalanced distribution of pounding forces found across the expansion joint is able to cause local damage to colliding girders and transmit high impact forces to bearing supports. In general, restrainers perform effectively to minimize the possibility of deck unseating and reduce the pounding forces at the expansion joint. Special attention should be paid to the non-linear bridge dynamic response in order to avoid failure of restrainers and ensure the adequate proportioning of the cables according to the characteristics of isolation bearings.     

桥梁桩基冲击钻孔振动衰减特性试验分析

本文对张石高速公路N9标段拒马河8#大桥桥梁桩基冲击钻孔施工过程中地面振动进行了现场测试,利用实测数据,分析了冲击钻不同的提升高度(落锤高度)、质点的竖直振动速度随水平距离的变化的传播规律.     

Assessment of the dynamic and fatigue behaviour of the Panaro railway steel bridge

The functionality maintenance of European infrastructures like bridges is acquiring more and more importance due to the huge economic losses related to the interruption of their regular service. In particular, fatigue represents one of the most common failure modes occurring in steel and steel–concrete composite bridges: most failures in steel structures are related to fracture and fatigue. Railway bridges endure millions of stress cycles during their life and they are expected to be highly vulnerable to such phenomena. Phenomena like ‘vibration induced’ and ‘distortion induced’ fatigue are still partially uncovered by actual design codes and they represent critical aspects for the assessment of existing bridge remaining life and for the design of new bridges. The European research project FADLESS ‘Fatigue damage control and assessment for railways bridges’, funded by the Research Fund for Coal and Steel, aims at defining innovative technical guidelines for the assessment and control of existing and new bridges with regard to fatigue phenomena induced by vibrations and distortions produced by train passages. The project combines experimental and numerical techniques to study fatigue cracking induced by vibration and distortion phenomena taking into account the dynamic train–bridge interaction effects and the actual traffic spectra on European railway lines. In the present paper, preliminary analyses performed on the Italian case study, the Panaro Bridge, are being reported upon. Results obtained by standard fatigue assessment according to Eurocode rules were compared with the actual fatigue cracks found in the deck secondary components. A preliminary critical review of adopted fatigue assessment methodologies was carried out. Moreover, experimental tests were designed and performed on the bridge in order to identify global and local vibration modes and to evaluate the strain time-histories under train passages of critical details. Finally, experimental global/local mode shapes were compared to numerical results from the preliminary FE bridge model.     

基于Betti-Rayleigh动力互易定理求解移动荷载引起的地基土振动

 基于Betti-Rayleigh动力互易定理,论证了地基土Green函数的互易性,推导了移动荷载引起的地基土振动解析解,进而推证出移动常力荷载和移动简谐荷载作用下地基土表面振动在波数–频率域内和空间–时间域内的解析表达式,并采用Matlab对其进行数值计算。通过互易定理的使用将振源的移动问题变换为地面上受振点的移动问题,使移动荷载作用下地基土振动响应的解析表达式大大简化。最后结合某地基土参数对移动的单位常力荷载和单位简谐荷载作用下的地面振动进行算例分析,结果表明：移动常力荷载引起的地面振动属于典型的低频振动;移动简谐荷载作用下地基土表面出现波动的Doppler效应,且地面上受振点的振动频率范围由最上层地基土的Rayleigh波波速控制;地面上的受振点距振源较近时,地基土表面R波对振动的贡献明显高于P波和S波,而当受振点距振源较远时,P波对振动的影响较明显。