有砟轨道动刚度特性及影响因素分析

应用轨道结构的动力学频域分析方法,研究了有砟轨道的动刚度特性及轨道参数对它的影响。有砟轨道动刚度随频率变化幅度很大,在激振频率为72 Hz时达到最小值55 kN/mm,约为静刚度的60 %。扣件刚度、扣件阻尼、轨枕类型、道床弹性模量对有砟轨道动刚度都有影响。     

城市轨道交通地下线整体道床设计相关问题探讨

根据广州地铁设计与运营的情况,建立了地下线整体道床有限元分析模型,探讨了整体道床钢筋网设置方式、非盾构地段隧道结构与整体道床连接设计、轨枕、排水方式等的合理方案。分析结果表明:在列车活载作用下,道床板的上下表面在纵横向都有受拉或受压的可能,道床板宜双层配筋;轨枕的长度对道床板应力影响很小,而道床板应力随着轨枕宽度的增加而增大,地下线整体道床在保证施工方便及扣件锚固需要的尺寸外,建议采用尺寸较小的钢筋混凝土长轨枕。为预防结构底板变形缝处渗水病害,在道床设计时,应加强道床与基础的连接,考虑疏水、导水     

地铁列车荷载作用位置对道床与管片剥离的影响研究

城市地铁盾构区间隧道若出现道床与管片剥离病害,会直接威胁到列车的运行安全。以某地铁区间线路为背景,通过数值模拟研究了列车运行过程中对道床和管片剥离影响最大的荷载位置。根据荷载作用在道床上的不同位置,发现荷载在远离道床伸缩缝的过程中相邻道床底部的拉应力值急剧减小,确定了荷载最不利位置为道床靠近伸缩缝处,可为模型试验和病害治理提供参考。     

隧道内新型组合轨枕块式无砟轨道结构分析

针对复杂艰险山区铁路隧道内区段较为严重且整治难度较大的基础变形病害,提出了一种隧道内新型组合轨枕块式无砟轨道,能充分适应轨道下部基础的变形,并基于有限元法对该结构的不同参数进行了力学分析。结果表明:为保证钢轨垂横向位移及轨道结构各部分所受拉应力值较小,建议组合式轨枕块的长宽高分别为830,276,140 mm;凹槽的深度宽度分别为80,970 mm;凸出高度为60 mm;为保证结构的整体性,建议组合式轨枕块选取聚氨酯材料;列车在新型组合轨枕式无砟轨道上运行时,其安全性与平顺性均满足要求。     

无砟轨道路基动力响应影响因素分析

以双块式无砟轨道路基典型结构为研究对象,分析车辆轴重、结构层间接触条件、轨道结构整体模量、支承层模量和基床表层模量等对路基面动力响应的影响,分析路基动力响应对各参数的敏感性。数值仿真结果表明:在车辆单轴荷载作用下,路基面动应力分布表现为横向均匀、纵向三角形的基本形式;对路基面动应力沿线路纵向分布长度影响的主要因素,是无砟轨道结构的整体刚度、车辆轴重、支承层模量等;结构面间接触状态劣化导致无砟轨道结构刚度的降低和路基面的动压力增大。     

山区高陡横坡段桥梁桩基承载机理模型试验

以现场工程为原型,设计了45°,60°,75°三种不同陡坡下高陡横坡段桥梁桩基的室内模型承载试验.通过对承载过程中桩顶位移、桩身内力及桩侧土压力等的全程测量,对竖向及水平向荷载作用下桩基的荷载传递规律、内力分布规律及桩侧土压力分布规律进行了研究.结果表明:竖向荷载下高陡横坡段桥梁桩基承载力由桩侧摩阻力与桩端阻力组成,但由于临空面存在,靠边坡一侧桩侧摩阻力传递深度更大,且该效应随边坡坡度的增加而增大;水平向荷载作用下,桩基桩顶水平位移随边坡坡度增加而增大,而内力分布规律与平地桩基类似,即存在最大弯矩及反弯点,但最大弯矩随边坡坡度的增加明显增大,反弯点位置则随坡度增加而有所下移;不同荷载及坡度情况下,后桩桩侧压力随深度均呈现先增大后减小的基本规律,而前桩桩前土抗力则随深度逐渐衰减.     

弹性支承轨道短枕尺寸研究

建立了钢轨-轨枕-道床-路基相互作用的弹性支承轨道有限元分析模型，以固定荷载为加载条件，综合分析了不同的短枕尺寸及支承刚度对短枕稳定性的影响，确定了短枕的合理尺寸范围，提出了短枕位移及翻转角度的限值建议。     

隧道内合成轨枕无砟轨道参数分析

针对隧道内合成轨枕无砟轨道结构形式,应用有限元分析Ansys软件,建立钢轨-扣件-合成轨枕-橡胶层-道床板-弹性基础的有限元分析模型,分析不同合成轨枕下橡胶层刚度、合成轨枕参数对合成轨枕无砟轨道结构的影响,为大瑞线无砟轨道结构的设计和施工提供依据。     

斜坡段桥梁基桩竖向承载力试验及数值模拟研究

以某斜坡段桥梁基桩为原型建立室内模型进行竖向承载力试验,并与三维数值模拟计算结果进行对比,分析其竖向承载特性及破坏模式。结果表明,桩顶竖向荷载相同时,基桩顶沉降量随斜坡坡度及基桩自由段长度的增加而增大,基桩的荷载位移曲线上没有出现较明显的拐点;数值模拟计算结果比模型试验结果大,但两者变化规律基本一致,其误差除60°边坡达到15.54%外,其他均在10%以内;边坡坡度越大,基桩极限承载力越小,减小幅度为5%～25%;不同坡度下基桩桩身轴力均随深度增加而减小,坡度越小减小幅度越大;斜坡基桩的竖向荷载主要由桩端承担,桩端阻力占比为70%～80%,坡度越大桩端承担的荷载比例越大;随基桩自由段长度的增加,基桩极限承载力减小,减小幅度为5%～15%;竖向荷载作用下斜坡段桥梁基桩主要表现为变形过大所导致的基桩屈曲失稳破坏。     

斜坡段桥梁基桩竖向承载特性模型试验研究

以某实际工程桩为原型,考虑坡度和桩长的影响,根据相似理论设计并完成了竖向荷载作用下斜坡段桥梁基桩室内模型试验,获得了不同坡度及不同桩长下基桩的荷载-位移曲线、桩身轴力与桩侧摩阻力沿深度的分布规律以及基桩极限承载力,据此通过非线性拟合,建立了斜坡桥梁基桩竖向承载折减系数与桩长及坡度直接的关系式。试验研究表明:竖向荷载相同时,桩顶沉降与水平位移均随坡度及桩长的增加而增大,基桩的荷载-位移曲线均无明显拐点,并呈现出因变形过大导致基桩屈曲失稳的破坏模式;斜坡效应对基桩竖向承载的影响约限于8倍桩径深度范围内;与平地桩相比,斜坡桩的桩侧摩阻力更易达到极限值,实际工程设计时应对其进行适当折减;边坡坡度越大、自由段越长,基桩竖向承载力越小。     

Thermal buckling and post-buckling behaviour of continuous welded rail track

Because thermal expansions are constrained within continuous welded rail track, the track can buckle, and does so mainly in the horizontal plane. In this paper, a parametric finite element model of railway track is presented, and its sensitivity to the variations of the main parameters that characterise the scenario has been investigated and discussed. Comparison with existing literature shows good agreement. It is found that curved tracks suffer from thermal buckling more than tangent tracks do. To simulate a track misalignment defect, a new methodology has been utilised that does not introduce, as is usual, geometrical discontinuities near the same defect, because it takes into account – in a natural way – the bending stiffness of the whole railway track in the horizontal plane. To contribute to a better understanding of the safe utilisation of raw experimental data obtained from in situ tests, a deep analysis of the effects on the thermal track buckling response produced by each parameter characterising the sleeper–ballast lateral resistance curve is presented and discussed. It is found that for current ballasted railway tracks, the minimum buckling temperature depends only on the limit lateral resistance, whereas a high value of the initial stiffness can lead to overestimation of the maximum buckling temperature, also taking into account the ‘natural’ decrease in the maximum buckling temperature due to an increase in the railway-traffic-induced defect amplitude.     

Vertical Vibration Analysis of Vehicle/Imperfect Track Systems

Summary This paper studies the vertical vibration of a vehicle traveling on an imperfect track system. The car body and sleepers are modeled as Timoshenko beams with finite length, and the rail is assumed as an infinite Timoshenko beam with discrete supports. Imperfection of the track system comes from a sleeper lost partial support by the ballast. Since deflection of the rail is limited within a certain interval where the vehicle is passing over, the infinite domain problem can be transformed into a finite domain problem with moving boundary. In this work, the equations of motion of the car body, rail and sleepers are discretized first by the finite element method. The discretized equations of motion for the vehicle and track systems are then assembled, respectively. Finally, the Newmark method is applied to obtain the response of the vehicle and track systems at each time step. The effect of the vehicle speed on the response of the vehicle and track systems is investigated.     

Dynamic Train-Track Interaction: Variability Attributable to Scatter in the Track Properties

A numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure. A perturbation technique has been used to investigate the influence of the scatter in selected track properties. The train-track interaction problem has been numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the whole track structure. All numerical simulations have been carried out in the time-domain with a moving mass model. Properties such as rail pad stiffness, ballast stiffness, dynamic ballast-subgrade mass and sleeper spacing have been studied. To obtain sufficient statistical information from track structures, full-scale measurements in the field and laboratory measurements have been carried out. The influence of scatter in the track properties on the maximum contact force between the rail and the wheel, the maximum magnitude of the vertical wheelset acceleration, and the maximum sleeper displacement have been studied. Mean values and standard deviations of these quantities have been calculated. The effects of the variation of the investigated track properties are discussed.     

Dynamic Train-Track Interaction: Variability Attributable to Scatter in the Track Properties

A numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure. A perturbation technique has been used to investigate the influence of the scatter in selected track properties. The train-track interaction problem has been numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the whole track structure. All numerical simulations have been carried out in the time-domain with a moving mass model. Properties such as rail pad stiffness, ballast stiffness, dynamic ballast-subgrade mass and sleeper spacing have been studied. To obtain sufficient statistical information from track structures, full-scale measurements in the field and laboratory measurements have been carried out. The influence of scatter in the track properties on the maximum contact force between the rail and the wheel, the maximum magnitude of the vertical wheelset acceleration, and the maximum sleeper displacement have been studied. Mean values and standard deviations of these quantities have been calculated. The effects of the variation of the investigated track properties are discussed.     

大瑞铁路梯形轨枕减振材料参数研究

根据梯形轨枕结构形式的特点和大瑞线"三高四活跃"的地质条件,初步确定了高黎贡山隧道内L形混凝土支座式无砟轨道的结构形式,运用有限单元法建立梯形轨枕垂向受力有限元计算模型。通过分析各工况轨枕下减振材料在不同支撑间距下对梯形轨枕和L形支座的弯矩、梯形轨枕和钢轨的竖向位移情况,确定了梯形轨枕减振材料合理支撑间距为1.25m。     

梯子形枕在城市轻轨钢桥曲线地段的应用

根据城市轻轨钢桥上二期恒载不能太大的特点,文中选取梯子形枕的无砟轨道结构进行应用研究。对梯子形枕作了简要介绍并就梯子形轨道的结构、材质、尺寸、曲线地段几何线形实现方案及L形支座施工方案进行了初步设计。     

高速铁路列车荷载下钢轨平顺性影响因素分析

列车荷载作用下的钢轨变形曲线受列车荷载、轨道整体刚度、钢轨自身性能、扣件间距和温度力等因素的制约。文中运用有限单元法建立轨道简化模型,分析各种制约因素对轨道结构的影响程度。结果表明,随着列车荷载、轨道整体刚度的减小和钢轨重量的增大,钢轨的变形曲线也越来越平顺,而钢轨内部温度力和扣件间距的改变对钢轨的变形曲线影响很小,可忽略不计。     

高速铁路双方孔板式轨道结构静力分析

采用有限单元法,研究了双方孔板式无砟轨道结构的静力学特性。双方孔板式轨道作为一种新型的板式轨道结构,在纵向荷载、横向荷载和温度荷载作用下,随着轨道板长度的变化,各部件应力、变形值基本呈线性变化,但量值均较小,结构的力学性能优于日本板式无砟轨道。