Study on the safe value of multi-pier settlement for simply supported girder bridges in high-speed railways

This paper presents a method to analyse the influence of multi-pier settlement on the train–track–bridge coupled dynamic system, and to determine the safe value of the continuous multi-pier settlement for simply supported girder bridges in Chinese high-speed railways. Firstly, the mapping relationship between the multi-pier settlement and the rail deformation is derived theoretically. Then, taking the superposition of the rail deformation and the track random irregularity as excitation, the variations of vehicle dynamic indices are analysed based on the train–track–bridge dynamic interaction theory. Further, the relationships between the pier settlement and the change amounts of vehicle dynamic indices are obtained. The multi-pier settlement safe value is determined according to the limits of vehicle dynamic indices. Results show that the rail deformation caused by multi-pier settlement agrees well with the settlement data. When passing through the 32.6 m-long simply supported girder bridge with multi-pier settlement, the train suffers a low-frequency excitation. Only considering the influence of pier settlement, the settlement value difference between two adjacent piers should be less than 26.3 mm at China’s highest operation speed of 350 km/h from the perspective of dynamics, which is much larger than the pier settlement limit in the current code for Chinese high-speed railways.     

Mitigation of track buckling in transition zones of steel bridges by geotextile reinforcement of the ballast layer

Track thermal buckling is one of the primary safety issues of continuously welded rail tracks. It has been shown that transition zones of open deck steel bridges are more prone to track buckling, as the thermal loads from the bridge and lower track lateral resistance in this region can destabilize the track in the lateral plane. The aim of this paper is to assess the possibility of reinforcing the ballast layer with geotextiles to mitigate the track buckling problem in the transition zones. To do so, a number of laboratory experiments are performed using one and two layers of geogrids and various depths of ballast layer. Single tie push tests are performed on the track and force-displacement curves are derived for the sleepers. It is shown that adding the geotextile layer to the ballast layer can increase its lateral resistance by up to 41%. The results are then introduced in the numerical model of a track developed in Abaqus finite element software for track buckling analysis. It is shown that adding the geogrid layer can increase the track buckling temperature by up to 11.33 °C, an increase of almost 21%, compared to that of an unreinforced track.     

铁路既有线提速对轨道结构的要求

为了提高列车的运行速度，从钢轨、轨枕、扣件、道岔、道床和线路的养护维修方式等方面对铁路轨道技术方面提出了更高的要求，针对钢轨磨耗和伤损的严重情况，提出了延长钢轨使用寿命的措施，为铁路的建设和维修提拱了参考借鉴。     

轨道交通莘闵线高架桥抗震研究

结合上海市轨道交通莘闵线独柱墩设计 ,针对高架上铺设无缝线路的实际情况 ,建立了高架桥梁结构一桩基—土动力相互作用力学模型 ,采用工程场地波计算了高架桥的弹性、非线性地震响应 ,并对其进行抗震延性分析 ;重点探讨了高架桥上长钢轨对桥梁的纵向约束作用及后继结构对桥梁抗震性能的影响 ,分析了橡胶支座对高架桥的减隔震作用 ;提出了莘闵线高架桥合理抗震设计参数及抗震措施     

滑动摩擦支座隔震桥梁地震反应分析

多滑面摩擦隔震支座具有刚度和阻尼的自适应性,在基于性能的桥梁抗震设计中有广泛的应用前景。本文以某近海连续梁桥为工程背景,考虑海洋软土条件,应用p-y法模拟桩-土相互作用,通过单摩擦摆（FPS）串联组成多滑动面摩擦摆支座（MFPS）模型,并建立全桥有限元模型。采用反应谱法和快速非线性分析（FNA）两种方法,对设置单滑面摩擦摆支座和多滑面摩擦摆支座的两种不同支座的隔震桥梁体系进行地震响应分析。对比分析两种方法得到的两种隔震桥梁结构的支座滞回性能和墩底剪力等的地震响应规律。研究结果表明,两种支座均具有较好的隔震效果,采用MFPS支座的桥墩的地震响应比FPS支座有所减小,且具有较大位移能力。     

高铁连续梁桥横向变形与轨面几何形态变化的映射关系研究

为研究高速铁路桥梁结构横向变形与轨面变形间的映射关系,在考虑高速铁路桥梁-路基-无砟轨道系统层间相互作用的基础上,基于势能驻值原理,推导出连续梁桥横向变形与轨面变形的微分方程及边界条件,提出连续梁桥横向变形与轨面变形的映射解析模型。利用所提的解析方法及有限元方法分别求解连续梁桥横向变形下的钢轨变形,并研究横向变形幅值不确定性对轨面变形的影响。结果表明：两种方法求解结果吻合良好,验证了所提的解析模型的正确性;桥梁结构变形与轨面变形的映射系数随桥梁结构变形幅值的增加而非线性增大;钢轨变形具有明显的“跟随性”;钢轨变形及层间扣件内力随连续梁桥变形幅值的增大而增大;列车运行速度越快,钢轨变形引起的激励频率越大。     

Integrated risk of rail buckling in ballasted tracks at transition zones and its countermeasures

Railway ballasted tracks at transition zones from embankment sections to bridge sections (or the reverse) suffer not only from seismic motions, but also from differential settlements during seismic motions. Therefore, an attempt is made in this study to evaluate the combined effects of hanging sleepers and seismic inertia force on the lateral resistance of ballast in the tracks at transition zones. A series of laboratory tests was conducted on 1/5 scale models to evaluate the lateral resistance characteristics under situations of hanging sleepers or under pseudostatic conditions. The results of the pullout tests revealed that the rail-buckling potential can be underestimated without the consideration of combined effects of hanging sleepers and the seismic inertia force on the lateral resistance. Based on the model test results, the combination of anti-buckling plates and ballast retaining walls is proposed as a new earthquake countermeasure.     

高速铁路无砟轨道基础结构垂向位移分布特性分析

建立高速铁路无砟轨道-路基结构动力有限元模型,系统分析高速列车荷载作用下轨道和路基垂向位移在时间和空间上的分布规律,比较轨道不平顺和断面位置对位移分布的影响规律。数值分析结果表明,轨道不平顺和横断面位置对轨道和路基垂向位移分布的影响可以忽略不计;高速列车荷载作用下钢轨和轨道板垂向位移的最大值分别为0.79mm和0.238mm,结果都在京津铁路现场试验实测数据的范围之内;轨道板和底座的垂向位移沿横向衰减非常缓慢,仅分别降低了3.6%和6.5%,沿深度基本没有变化;路基各层面垂向位移在轨道宽度范围内沿横向仅衰减10%左右,轨道宽度范围外位移按指数函数快速衰减,在距离线路中心线3m和4m附近,基床表层和基床底层的垂向位移已衰减一半以上,路基位移沿深度线性衰减,在距钢轨底面4m附近,垂向位移衰减50%左右,到基床底面处位移衰减70%以上。     

The Evaluation of Axial Stress in Continuous Welded Rails via Three-Dimensional Bridge–Track Interaction

The crucial differences between conventional rail with split-type connectors and continuous welded rails are axial stress in the longitudinal direction and stability, as well as other issues generated under the influence of loading effects. Longitudinal stresses generated in continuously welded rails on railway bridges are strongly influenced by the nonlinear behavior of the supporting system comprising sleepers and ballasts. Thus, the track structure interaction cannot be neglected. The rail-support system mentioned above has properties of non-uniform material distribution and uncertainty of construction quality. The linear elastic hypothesis therefore cannot correctly evaluate the stress distribution within the rails. The aim of this study is to apply the nonlinear finite element method using the nonlinear coupling interface between the track and structural model and to illustrate the welded rail behavior under the loading effect and uncertain factors of the ballast. Numerical results of nonlinear finite analysis with a three-dimensional solid and frame element model are presented for a typical track–bridge system. A composite plate girder, modeled by solid and shell elements, is also analyzed to consider the behavior of the welded rail. The analysis result showed buckling under the independent calculations of load cases, including ‘temperature change’, ‘bending of the supporting structure’, and ‘braking’ of the railway vehicle. A parametric study of the load combination method and the loading sequence is also included in this analysis.     

基底摇摆隔震桥墩振动台试验与数值模拟研究

为了研究不同构造形式的基底摇摆隔震桥墩在不同水准地震作用下的响应规律和抗震性能，提出了设置高阻尼橡胶垫块和线性弹簧的两种基底摇摆隔震桥墩模型。通过振动台试验和数值模拟，对两种摇摆隔震桥墩的地震响应规律和抗震性能进行了对比研究。结果表明：两种基底摇摆隔震桥墩在不同水准地震作用后，桥墩均没有出现严重的破坏，其破坏特征主要表现为限位钢板的弯曲变形和提离约束部件的移位，桥墩呈现出良好的抗震性能；两种基底摇摆隔震桥墩相对于传统桥墩能够显著降低墩顶加速度和墩底应变响应，但墩顶水平位移响应也会相应增加，在摇摆隔震桥墩的设计上，应将墩顶水平位移作为主要设计参数；提出了两种基底摇摆隔震桥墩改进的Winkler两弹簧数值计算模型，通过与振动台试验结果对比，证明了该模型能够较好地模拟两种基底摇摆隔震桥墩的摇摆行为及其地震响应规律。     

超高分子量聚乙烯在小阻力扣件系统中的应用

结合小阻力扣件系统在轨道交通高架线无碴轨道中的重要作用,简要介绍了超高分子量聚乙烯的性质和功能,并根据轨下垫板的实际使用环境和受力情况,采用该种材料制成轨下垫板进行了大量试验得出相关结论,最后联系实际应用状况阐述了该种轨下垫板的社会经济效益。     

在役混凝土梁式桥的抗震加固研究

对已建桥梁按照新的抗震设计规范进行抗震性能评价,根据评价的结果采取相应的抗震加固措施,考虑采取足够的构造措施和基于性能设计方法保证结构的整体延性,防止桥墩等构件的局部破坏,按照最新抗震规范,对某一在役混凝土梁式桥桥墩采取一定的加固措施,通过计算分析验证抗震加固的有效性,对地震作用下桥梁结构的安全性提出探讨     

河床冲刷深度变化对大型桩基桥梁地震反应的影响

以一座超大跨度斜拉桥为工程背景,采用解析解和有限元模拟计算相结合的方法,对河床冲刷深度变化对大型桩基桥梁地震反应的影响进行初步探索性研究。建立两质点单墩模型,推导地震反应计算公式,用解析法计算桥墩及其基础的地震反应随河床冲刷深度变化的情况,分析高桩承台基础与桥墩的动力相互作用规律,结果表明,由于承台大质量的存在,桥墩的地震反应会表现出显著的共振效应,当桥墩和基础的自振周期相近时,会出现一个峰值。进一步地,建立斜拉桥的全桥有限元模型,计算边墩、主塔及其基础的地震反应随河床冲刷深度变化的情况,验证了解析法得出的影响规律:河床冲刷深度变化对大型桩基桥梁的地震反应有很大的影响,随着冲刷深度的增加,桥梁结构的地震反应并不是单调减小,而可能出现一个峰值。     

轨道结构形式对箱梁中高频振动的影响研究

为探讨不同轨道结构对桥梁中高频振动的影响,在频域内建立考虑多轮对相互影响的车辆-轨道系统耦合模型和桥梁有限元模型,以某城市轨道交通30 m简支箱梁的现场动载试验为依据,对所建模型进行验证。在此基础上,采用数值方法就三种轨道结构形式（埋入式轨枕、梯形轨枕以及钢弹簧浮置板）对箱梁中高频振动的影响规律及原因进行了探讨。结果表明：“车轮-轨道系统”的固有频率影响轮轨力的峰值频段;频率低于“钢轨-扣件系统”的固有频率时,钢轨的动柔度受到轨道结构形式的影响;各轨道结构系统的固有频率决定着力传递率的衰减趋势,并在该固有频率附近放大力传递率;轮轨力（外因）与力传递率（内因）共同决定着传递到箱梁上的力,从而影响箱梁中高频振动;对于箱梁中高频振动的减振效果而言,钢弹簧浮置板最优,梯形轨枕次之,埋入式轨枕最差。     

Optimisation model to schedule railway track renewal operations: a life-cycle cost approach

Besides high initial construction costs, ballasted railway tracks also have high investment requirements, related to maintenance and renewal (M&R) works. Decision support tools for railway track components that optimise these works are increasingly gaining in importance. This paper presents an optimisation model that integrates ballast, rail and sleeper degradation models in a mixed integer linear programming model. This model links the decisions to renew these components with their condition and takes advantage of the integrated planning of renewal works to minimise the railway track life-cycle cost (LCC). The practical utility of the model is illustrated with a case study involving the Portuguese Lisbon–Porto line. The results indicate a reduction in track renewal cost if the grouping of components, track segments and time interval for renewal operations are optimised. Furthermore, this paper demonstrates that possible annual budget restrictions for railway track M&R operations can have an important influence on the railway track LCC.     

基于有限元计算的连续刚构桥地震响应分析

文章以某连续刚构桥为工程背景,运用了大型专业有限元结构分析软件分析了不等高墩大跨连续刚构桥地震响应。对比考虑桩土效应、不考虑桩土效应以及在考虑桩土效应的基础上引入隔震摩擦摆支座的3种不同边界条件的自振频率,结果表明考虑桩土效应和加入隔震支座可以减小结构的自振频率。分别采用反应谱分析法和线性时程分析法对连续刚构桥在地震作用下各控制截面的位移和内力进行比较分析,得出结构在地震作用下的一般性规律。同时将时程分析结果与相应的反应谱分析结果比较,验证了选取地震波是否满足规范要求。     

铁路机车车辆工厂厂房移动式轨道设计探讨

铁路工厂厂房内的移动式轨道,即在同一条轨道线上可方便灵活的转换成不同轨距,以满足对国内外不同种类机车车辆生产组装、维护维修、例行试验等工序作业。通过移动式轨道运用,大大节省了建设工程一次性投资。由于它具有拆装简便,安全可靠的特点,移动式轨道已取得国家发明专利。     

A new approach for evaluating lateral resistance of railway ballast associated with extended sleeper spacing

Recently, attempts have been made to replace wooden sleepers with concrete sleepers with expanded sleeper spacing, especially on conventional railway lines. By extending sleeper spacing in the replacement process, the number of sleepers required is lower. A reduction in the number of sleepers can reduce replacement costs. Behind this attempt to change materials and spacing is the generally held notion the lateral resistance of a ballast is unchanged after the change in the sleeper spacing, whether it is a wooden or a concrete sleeper. However, the changes in the interference degrees of adjacent sleepers and in the rail weight supported by each sleeper are expected to affect the lateral resistance of the ballast. They can change the lateral stability of ballasted tracks in a more complicated fashion than the simple effect of a reduced number of sleepers. However, the current standard design does not consider the combined effects of these changes on the lateral resistance of a ballast. Accordingly, the design of ballasted tracks with extended sleeper spacing cannot be optimized.Therefore, the aim of this study was to investigate the lateral resistance characteristics of a ballast as associated with changes in the sleeper spacing of conventional railway lines. First, single-sleeper pullout tests were conducted on models based on various sleeper spacing conditions to evaluate the lateral resistance of the ballast. The effect of the rail weight on the lateral resistance of the ballast was determined from the test results. An increased frictional resistance at the sleeper bottom was considered to contribute to an increase in the lateral resistance; thus, the friction angle between the ballast and sleeper bottom was used to evaluate the degree of increase. Subsequently, track panel pullout tests were conducted by simulating an expansion of the sleeper spacing. Based on the test results, the effect of the interference between adjacent sleepers on the lateral resistance per sleeper was investigated. The obtained results were quantitatively modeled as a function by using the sleeper width as a parameter (as normalized by the sleeper spacing). Finally, a new approach was proposed for estimating the lateral resistance of a ballast which considered the change in the sleeper spacing for conventional railway lines. The method considered the combined effects of change in the interference of adjacent sleepers and in the rail weight supported by each sleeper on the lateral resistance. Based on the results calculated by the proposed method, practical applications were examined by determining the extent to which the sleeper spacing could be increased without reducing the lateral resistance of the ballast when replacing wooden sleepers with concrete sleepers. It was demonstrated that the proposed method could improve the estimation accuracy of the lateral resistance of a ballast track with extended sleeper spacing.     

多点激励下桩-土-斜拉桥全模型振动台试验研究

大跨斜拉桥的自振频率和阻尼低以及空间尺度大,其地震响应受桩基础、场地土特性和地震动空间效应的影响较大。然而,由于试验条件和技术所限,目前尚缺乏相关的全模型振动台试验研究。以一座试设计主跨1400m超大跨斜拉桥为原型,设计和制作了一座几何相似比为1/70且包括上部结构、桩基础和场地土等在内的试验模型,通过振动台试验研究了多点激励对桩-土-斜拉桥全模型地震响应的影响及其规律。试验结果表明：纵向多点激励使一侧主塔的纵向位移、一侧主塔和桥墩的纵向桩-土-结构相互作用效果以及主跨一侧竖向位移增大,而另一侧减小;横向多点激励使一侧主塔的横向位移和一侧桥墩的横向桩-土-结构相互作用效果增大,另一侧减小,但使两侧主塔的横向桩-土-结构相互作用效果和主跨两侧横向位移响应均增大;桩-土-结构相互作用对斜拉桥的加速度响应产生不利影响。基于上述结果,大跨斜拉桥的抗震设计或性能评估应考虑多点激励和桩-土-结构相互作用的影响。     

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.