CRTSⅡ型板式轨道CA砂浆层应力波法损伤识别

CRTSⅡ型板式无砟轨道在常年反复的使用过程中,其CA砂浆层易出现层间离缝、脱空等损伤。目前应用冲击回波法对无砟轨道板进行的无损检测需要在轨道板上布置较密的测线,并进行多点激发与接收。这种方法不适合对轨道板CA砂浆层损伤进行快速普查。作者用三维有限元法分析了单点激发下应力波在CRTSⅡ型轨道板中的传播规律。通过比较有无CA砂浆层缺陷轨道板周边的速度或加速度峰值,发现可根据CA砂浆层缺陷引起的速度或加速度峰值的变化率检测缺陷。如果取6%的变化率为阀值,在轨道板周边按20cm的间距设加速度检测点,或按30cm的间距设速度检测点,单点激发即可识别CA砂浆层中40cm×40cm以上的损伤。     

轨道刚度变化对高速列车-板式轨道系统振动响应的影响分析

针对板式轨道的结构特点,利用横向有限条与板段单元模拟板式轨道,并考虑轮轨竖向位移衔接条件,基于弹性系统动力学总势能不变值原理及形成系统矩阵的“对号入座”法则,建立了高速列车-板式轨道动力学耦合系统的竖向振动矩阵方程.在此基础上,分析了板式轨道的刚度变化对此系统竖向振动响应的影响规律.计算结果表明,合理的轨道刚度将有利于降低此系统的竖向振动响应.并建议CA砂浆刚度合理的取值范围为1 000—1 500 MPa/m,轨下垫层刚度合理的取值范围为60—80 kN/mm.     

CRTSⅡ型无砟轨道CA砂浆开裂风险有限元计算

工程实践表明,CRTSⅡ型无砟轨道CA砂浆在施工早期阶段具有较高的开裂风险,为揭示CA砂浆开裂的规律,采用有限元模拟的手段对CRTSⅡ型无砟轨道CA砂浆的早期收缩开裂风险进行了模拟计算。结果表明:CRTSⅡ型无砟轨道CA砂浆两侧边的开裂风险远高于板中部分,侧边部位CA砂浆早期收缩应力随着龄期发展不断增大,第6d后开裂风险因子首次突破临界值1;氢氧化钙类膨胀剂可以有效延迟CA砂浆开裂的时间;CRTSⅡ型无砟轨道侧边CA砂浆28d干燥收缩率小于120×10-6时,在整个观测期内无开裂风险。研究结果可为我国CRTSⅡ型无砟轨道CA砂浆裂缝的预防与控制提供参考。     

基于分段式模型考虑界面损伤的GFRP锚杆-砂浆粘结性能数值模拟

通过编写Vumat子程序定义玻璃纤维增强塑料（GFRP）锚杆材料参数,并考虑GFRP锚杆与砂浆界面的不均匀及损伤特性进行正交各向异性建模,借助ABAQUS有限元软件对GFRP锚杆与砂浆界面的粘结滑移特性进行分段模拟,探究GFRP锚杆轴力、界面剪应力分布形态,进而对不同直径GFRP锚杆-砂浆界面力学特性进行分析。研究结果表明：分段式有限元模型能够较好地反映GFRP锚杆-砂浆的粘结特性。随着施加荷载的增加,GFRP锚杆所受轴力逐渐增大,荷载传递深度逐渐加深,锚固作用自上而下逐渐发挥;GFRP锚杆拔出所需最大拉力、界面破坏位移随直径减小而增大。GFRP锚杆发生破坏的临界直径为28 mm,当直径大于28 mm时发生滑移破坏,直径小于28 mm时发生强度破坏。计算确定直径28 mm GFRP锚杆的锚固系数K₁为0.155。     

温差对磁浮双跨轨道梁变形的影响

为探讨现有规定对磁悬浮轨道梁受温差荷载作用下产生的位移要求是否过于严苛,建立三种不同截面高度的磁浮双跨轨道梁有限元模型进行稳态分析,得到三种不同环境温度下的温度分布及竖向、横向最大位移。比较分析可知:竖向挠跨比均不满足现有规范,现有规范过于严苛;横向挠跨比均满足现有规范。     

空心板桥损伤铰缝模拟界面单元法研究

针对既有铰缝损伤模型难以直接利用现场实桥裂缝常规检测信息的问题,提出一种将界面单元和工程中铰缝处横向开裂宽度和竖向错动检测数据相融合的铰缝损伤模拟新方法。基于试验曲线,通过理论解析获得了切向刚度与铰缝开裂和错动位移的变化规律,揭示了破坏过程中切向与法向的交互作用,给出了损伤状态下切向刚度与铰缝开裂大小的关系曲线,拟合建立了法向位移和切向位移与切向刚度的数值方程,据此可获得不同强度和粒径尺寸混凝土铰缝的刚度参数上限值,结合工程案例进行了仿真测试。结果表明:切向刚度随着裂缝宽度而递减,工作范围在0～0.4 mm;当裂缝宽度处于0～2 mm时,耦联刚度值不应忽略,并给出了与铰接板和刚接板相等效的界面单元切向刚度参数值。所做工作有助于促进界面单元在铰缝损伤模拟方面的实用化进程。     

铰缝及板损伤后对空心板桥横向受力的影响

为研究空心板桥在铰缝及板受损后的横向受力状况,基于铰接板理论,建立了空心板桥铰缝及板受损后的解析模型,揭示了铰缝及板损伤后对桥梁整体横向受力的影响程度.结果表明:铰缝损伤会降低空心板横向传递荷载的能力,损伤程度越大,各板分配到的最大荷载越大,且距离受损铰缝越近的板受到的影响越大;当铰缝与板同时损伤时会导致周围完好板承担的荷载增加,越易出现损伤.     

移动荷载作用下加筋路堤和轨道系统的三维动力响应

用解析法研究了加筋路堤上轨道系统在移动荷载作用下的三维动力响应问题。基于Biot多孔弹性介质的波动理论,建立了加筋路堤轨道系统分析模型。将钢轨简化为无限长弹性Euler梁,将枕木简化为连续质量块,将加筋路堤作为一横观各向同性层来考虑,将下卧土体考虑为由Biot波动方程描述的饱和半空间。联立轨道系统、加筋路堤和下卧土体的动力方程,在Fourier变换域内求解荷载作用下钢轨位移和土体位移的表达式,将求得的表达式进行Fourier逆变换得到其在时域里的表达式。研究了列车移动速度、加筋路堤层的厚度、荷载幅值大小和加筋率等对路堤及轨道系统动力响应的影响。计算结果表明,钢轨竖向变形随着速度的增大呈现先增大后减小的趋势;加筋路堤上的钢轨竖向变形显著小于同厚度下未加筋路堤上的钢轨竖向变形;钢轨竖向变形随着荷载幅值的增大而增大;随着加筋率的增大而减小。     

季冻区CRTS I型无砟轨道不平顺规律及受力特性

为探讨路基冻胀变形对轨道不平顺及结构受力的影响规律,基于ANSYS有限单元分析方法,以哈大高速铁路冻胀区路基段为研究基础,建立了考虑限位凸台、凝胶树脂及层间粘结接触特征的CRTS I型板式无砟轨道-路基冻胀冻融耦合精细化有限元模型. 在此基础上,探讨局部冻胀区路基冻胀变形发生位置、不同冻胀波长及幅值对无砟轨道结构的影响,分析了短波冻胀下轨道不平顺、层间离缝特性与静力学性能. 结果表明:短波冻胀时无砟轨道结构不平顺范围、变形、离缝、受力等各项指标均随冻胀波长的减小、冻胀峰值的增加而增大;冻胀发生于底座板板中时对轨道结构受力影响最大,冻胀发生于底座板伸缩缝时对轨道结构变形离缝影响最大;相对于轨道板结构,底座板承受拉应力最大,冻胀发生于底座板板中时结构受力影响更大;在轨道结构抗拉强度方面,底座板为限制结构,建议冻胀检修限值的波长为10 m、峰值为5 mm.     

季冻区CRTSⅠ型无砟轨道不平顺规律及受力特性

为探讨路基冻胀变形对轨道不平顺及结构受力的影响规律,基于ANSYS有限单元分析方法,以哈大高速铁路冻胀区路基段为研究基础,建立了考虑限位凸台、凝胶树脂及层间粘结接触特征的CRTS Ⅰ型板式无砟轨道-路基冻胀冻融耦合精细化有限元模型.在此基础上,探讨局部冻胀区路基冻胀变形发生位置、不同冻胀波长及幅值对无砟轨道结构的影响,分析了短波冻胀下轨道不平顺、层间离缝特性与静力学性能.结果表明:短波冻胀时无砟轨道结构不平顺范围、变形、离缝、受力等各项指标均随冻胀波长的减小、冻胀峰值的增加而增大;冻胀发生于底座板板中时对轨道结构受力影响最大,冻胀发生于底座板伸缩缝时对轨道结构变形离缝影响最大;相对于轨道板结构,底座板承受拉应力最大,冻胀发生于底座板板中时结构受力影响更大;在轨道结构抗拉强度方面,底座板为限制结构,建议冻胀检修限值的波长为10 m、峰值为5 mm.     

Effect of cross-wind on spatial vibration responses of train and track system

By taking cross-wind forces acting on trains into consideration, a dynamic analysis method of the cross-wind and high-speed train and slab track system was proposed on the basis of the analysis theory of spatial vibration of high-speed train and slab track system. The corresponding computer program was written by FORTRAN language. The dynamic responses of the high-speed train and slab track under cross-wind action were calculated. Meanwhile, the effects of the cross-wind on the dynamic responses of the system were also analyzed. The results show that the cross-wind has a significant influence on the lateral and vertical displacement responses of the car body, load reduction factor and overturning factor. For example, the maximum lateral displacement responses of the car body of the first trailer with and without cross-wind forces are 32.10 and 1.60 mm, respectively. The maximum vertical displacement responses of the car body of the first trailer with and without cross-wind forces are 6.60 and 3.29 mm, respectively. The maximum wheel load reduction factors of the first trailer with and without cross-wind forces are 0.43 and 0.22, respectively. The maximum overturning factors of the first trailer with and without cross-wind forces are 0.28 and 0.08, respectively. The cross-wind affects the derailment factor and lateral Sperling factor of the moving train to a certain extent. However, the lateral and vertical displacement responses of rails with the cross-wind are almost the same as those without the cross-wind. The method presented and the corresponding computer program can be used to calculate the interaction between trains and track in cross-wind. Foundation item: Project (2007CB714706) supported by the Major State Basic Research and Development Program of China; Project (50678176) supported by the National Natural Science Foundation of China; Project (NCET-07-0866) supported by the New Century Excellent Talents in University     

Damage evolution and dynamic response of cement asphalt mortar layer of slab track under vehicle dynamic load

The damage evolution and dynamic performance of a cement asphalt (CA) mortar layer of slab track subjected to vehicle dynamic load is investigated in this paper. Initially, a statistical damage constitutive model for the CA mortar layer is developed using continuous damage mechanics and probability theory. In this model, the strength of the CA mortar elements is treated as a random variable, which follows the Weibull distribution. The inclusion of strain rate dependence affords considering its influence on the damage development and the transition between viscosity and elasticity. Comparisons with experimental data support the reliability of the model. A three-dimensional finite element (FE) model of a slab track is then created with the commercial software ABAQUS, where the devised model for the CA mortar is implemented as a user-defined material subroutine. Finally, a vertical vehicle model is coupled with the FE model of the slab track, through the wheel-rail contact forces, based on the nonlinear Hertzian contact theory. The evolution of the damage and of the dynamic performance of the CA mortar layer with various initial damage is investigated under the train and track interaction. The analysis indicates that the proposed model is capable of predicting the damage evolution of the CA mortar layer exposed to vehicle dynamic load. The dynamic compressive strain, the strain rate, and the induced damage increase significantly with an increase in the initial damage, whereas the dynamic compressive stress exhibits a sharp decrease with the increasing initial damage. Also, it is found that the strain rate dependence significantly influences the damage evolution and the dynamic behavior of the CA mortar layer.     

Analysis theory of spatial vibration of high-speed train and slab track system

The motor and trailer cars of a high-speed train were modeled as a multi-rigid body system with two suspensions. According to structural characteristic of a slab track, a new spatial vibration model of track segment element of the slab track was put forward. The spatial vibration equation set of the high-speed train and slab track system was then established on the basis of the principle of total potential energy with stationary value in elastic system dynamics and the rule of ＂set-in-right-position＂ for formulating system matrices. The equation set was solved by the Wilson-θ direct integration method. The contents mentioned above constitute the analysis theory of spatial vibration of high-speed train and slab track system. The theory was then verified by the high-speed running experiment carried out on the slab track in the Qinghuangdao-Shenyang passenger transport line. The results show that the calculated results agree well with the measured rcsults, such as the calculated lateral and vertical rail displacements are 0.82 mm and 0.9 mm and the measured ones 0.75 mm and 0.93 mm, respectively; the calculated lateral and vertical wheel-rail forces are 8.9 kN and 102.3 kN and the measured ones 8.6 kN and 80.2 kN, respectively. The interpolation method, that is, the lateral finite strip and slab segment element, for slab deformation proposed is of simplification and applicability compared with the traditional plate element method. All of these demonstrate the reliability of the theory proposed.     

Temperature-induced deformation of CRTS II slab track and its effect on track dynamical properties

Two finite-element models of the CRTS II slab track are presented to simulate temperature-induced deformations of the concrete track slab with no deterioration or with a deteriorated cement asphalt mortar(CAM).One model,which considers the fully bonding interface between the slab and the CAM layer,could applied to a track that is in good condition;the other model uses cohesive zone elements to simulate the deteriorated CAM with some possible interfacial separation and slip.Utilizing both of the models,temperature-induced warp deformations of track under various temperature loads are investigated.The influence of temperature deformation on the dynamic properties of the track is analyzed based on the train-track coupled dynamics.Numerical results show that the deteriorated CAM layer can significantly increase temperature deformations of a CRTS II track slab,which would produce tiny rail irregularities.There are clear differences between the deformation shapes of the track slabs that have an inseparable mortar layer and those have a separable mortar layer.The track slab with a deteriorated mortar layer showed more open curl distortion than the track slab in good condition.The dynamical response index of the slab track is intensified to a certain level due to the temperature deformation;with an increase of the train speed,the track dynamical responses increased linearly.However,rail irregularities due to the temperature deformations are very tiny.Even if a track is exposed to extreme temperature loads and the mortar layer is deteriorated,temperature deformation can have a negligible effect on the track’s dynamical properties.     

预制式轨道板质量对钢轨和桥梁的振动影响

本文针对轨道交通和高速铁路中广泛采用的无砟轨道结构,对无砟轨道的轨道板结构的分析基础上,针对预制式轨道板结构的特点,建立了预制式轨道板结构的力学模型,即弹性支撑的刚体模型。通过对预制式轨道板结构质量变化对轨道和桥梁系统振动响应影响的分析,求得无砟轨道中预制式轨道板结构的质量对振动影响的规律,提出了无砟轨道结构减振设计的优化方案。     

地铁列车引起的振动对城市敏感建筑结构的影响

以某相对地铁线路水平距离较近的市级文物保护敏感建筑为研究对象,设线路时速70km／h,分析地铁列车运行时产生的振动对该建筑结构的动力影响。针对整体道床和橡胶减振垫浮置板道床,建立车辆-轨道耦合模型,采用Newmark方法计算列车载荷;建立轨道-土层耦合模型,利用有限元方法分析地铁列车引起的振动在地表面的传播特性,并计算地铁列车振动对敏感建筑结构及周围环境的影响。研究结果表明:采用整体道床时,敏感点的垂向Z振级和敏感建筑结构的水平速度都大于标准值;采用橡胶减振垫浮置板道床时,敏感点的垂向Z振级和敏感建筑结构的水平速度都低于标准值;同时说明橡胶减振垫浮置板道床具有很好的减振效果。     

剪压区和剪跨比对混凝土板受剪承载力的影响

为探究受拉纵筋屈服的情况下,混凝土板内支座控制截面的相对剪压区高度和板的剪跨比对其受剪承载力的影响,完成了4个混凝土板试件的受剪试验.试件由板、板端伸臂构件、板下柱以及底梁构成,试验借助板端伸臂构件在板端施加力偶,在预估斜裂缝起始位置的外侧施加竖向荷载,在竖向荷载和板端力偶共同作用下使板顶纵筋在斜裂缝与其相交处接近屈服...     

高速铁路双块式无砟轨道车辆荷载动态传递特征

为研究车辆荷载在无砟轨道中的传递特征,建立车辆-双块式无砟轨道耦合动力学模型,对车辆荷载在无砟轨道主体结构内的动应力和振动加速度传递规律进行研究,并对行车速度、结构尺寸及层间接触状态等影响因素进行分析. 结果表明:车辆荷载的主承载区分布在道床板内,垂向动应力峰值在0.1 m深度之内衰减73%;车辆荷载的主振动区主要分布在道床板内并传递至支承层,垂向加速度峰值在0.1 m深度之内衰减89%;轨道结构动态受力及振动响应均随行车速度的增加而增大;适当减少轨道结构宽度,对其受力和振动特性影响较小. 无砟轨道结构层间插入隔离层,可减小轮轨动力响应及轨道结构动态受力,但结构层间垂向加速度明显增大,插入弹性层,可减小钢轨垂向加速度,但对轮轨动力响应、道床板和支承层动态受力及振动特性影响较小. 所得结论可为无砟轨道设计和优化提供理论参考.     

列车作用下青藏铁路路基动力响应试验

目的分析研究多年冻土区青藏铁路在列车动荷载作用下路基的稳定性及振动衰减规律．方法选取青藏铁路北麓河段三个典型试验断面,在春季进行了列车荷载作用下的路基动力响应现场试验,采集路基、边坡、道床3处振动数据,统计计算了青藏铁路客车与货车行驶时路基振动的最大和平均加速度幅值,对实测数据进行了功率谱分析．结果路基上货运和客运列车的竖向最大加速度分别为2．2132m／ss^2和2．0004m／ss^2,对应的平均加速度分别为0．1495m／s^2和0．1143m／ss^2,道床上的振动明显减小．在T28次客运列车的作用下,对于断面Ⅲ,C3测点在振动频率为25Hz、38Hz、46Hz,55Hz出现峰值,能量集中在18～53Hz．边坡C4测点振动能量集中在20—65Hz,C5测点的优势频段为20—80Hz．结论路基上货运列车的振动比客运列车振动大,同一断面竖向衰减速度大于横向,素土路基各方向衰减小于块石路基,下一测点加速度峰值大致减小为相邻上一测点的1／10．