Calculation of the dynamic response of a viscoelastic railway structure based on a quasi-stationary approach

A semi-analytical method has been developed for computing the dynamic response of railways composed of viscoelastic layers under moving loads. One of the aims of this new approach is to be able to simulate railways incorporating asphalt materials. These materials are increasingly used or highly considered for construction projects. We have modeled the mechanical behavior of bituminous mixes with the Huet–Sayegh thermo-sensitive viscoelastic law that is specifically intended for such materials. This method, implemented in a numerical program, is based on a quasi-stationary approach, so that time is not a specific factor in the solution. The required calculation time is therefore small, for the convenience of parametric studies. The capability of this method is proved with a numerical example that provides several validation points and illustrates at the same time the temperature effect on the response of a railway including an asphalt layer.     

Rail-bridge coupling element of unequal lengths for analysing train-track-bridge interaction systems

This paper presents a rail-bridge coupling element of unequal lengths, in which the length of a bridge element is longer than that of a rail element, to investigate the dynamic problem of train-track-bridge interaction systems. The equation of motion in matrix form is given for a train-track-bridge interaction system with the proposed element. The first two numerical examples with two types of bridge models are chosen to illustrate the application of the proposed element. The results show that, for the same length of rail element, (1) the dynamic responses of train, track and bridge obtained by the proposed element are almost identical to those obtained by the rail-bridge coupling element of equal length, and (2) compared with the rail-bridge coupling element of equal length, the proposed element can help to save computer time. Furthermore, the influence of the length of rail element on the dynamic responses of rail is significant. However, the influence of the length of rail element on the dynamic responses of bridge is insignificant. Therefore, the proposed element with a shorter rail element and a longer bridge element may be adopted to study the dynamic responses of a train-track-bridge interaction system. The last numerical example is to investigate the effects of two types of track models on the dynamic responses of vehicle, rail and bridge. The results show that: (1) there are differences of the dynamic responses of vehicle, rail and bridge based on the single-layer and double-layer track models, (2) the maximum differences increase with the increase of the mass of sleeper, (3) the double-layer track model is more accurate.     

The effects of floating slab bending resonances on the vibration isolation of rail viaduct

This paper compared the performance of several isolation designs to control vibration transmissions from concrete rail viaducts. The isolation systems analysed includes medium- and short-length floating slabs, and floating ladders. The vibration was measured in Japan, Korea and Hong Kong. The study aimed to assess the effects of bending resonances of the floating slab systems. Simple formulae of estimating the significant bending resonance frequency and support passage frequency of a floating slab system are proposed. The resonance peaks obtained in site measurement are found to be in agreement with the calculation results. The results show that other than the vertical rigid body resonances for the isolation systems, the bending resonances of slabs have significant effects on vibration isolation performance. In particular, bending resonance frequencies should not coincide with the vertical isolator resonance and support passage frequency. According to the in-situ measurement results, a mini-type concrete floating slab can reduce the vibration level by more than 30 dB in the frequency range of 63-200 Hz. This should be achieved by designing the first bending resonances of the floating slab to be out of the dominant frequency range of concrete rail viaduct vibration.     

“一带一路”重大铁路建设生态与经济影响遥感监测

“一带一路”提出以来,中国海外建设的重大铁路工程增长迅速,铁路建设在促进经济发展、增强区域互联互通的同时,也对当地的自然生态环境产生一定程度的影响,对铁路建设造成的生态环境和社会经济影响进行监测与分析,可以为“一带一路”工程建设提供科学有效的信息支撑。本文利用多尺度、多源遥感数据,通过遥感和GIS技术,从生态资源占用与损失、生物多样性保护举措、夜间灯光指数等方面,以“一带一路”重大铁路工程本格拉铁路为例,对其沿线区域生态环境状况和社会经济影响进行监测与分析,旨在为今后铁路工程建设生态保护提供科学有效的指导。研究结果表明：(1)本格拉铁路工程建设没有对沿线自然生态环境整体格局造成破坏性扰动,工程建设占用的自然生态资源较小,保护了区域的生物多样性;(2)本格拉铁路建设促进了沿线区域的经济发展,极大地缩短及沿线城市之间的通行时间,实现南部非洲区域铁路的互联互通,极大地降低周边国家的资源运输成本和时间;(3)通过遥感与GIS技术,能够对铁路工程建设自然生态环境和社会经济影响进行快速、定量、客观的监测,对今后铁路工程建设影响研究以及生态保护具有一定的参考意义。     

铁路工程物资采购供应管理研究

铁路工程物资集中采购与管理对于我国铁路工程建设具有重要作用,本论文从物资管理的基本含义作为出发点,详细讨论了当前我国铁路工程物资采购管理中存在的问题,在此基础上,重点对铁路工程物资采购与供应管理的发展提出了建议与策略,构建了面向铁路工程的集中采购与供应管理模式环节,并从建立评价体系和风险防范机制两个角度详细探讨了铁路工程物资采购供应管理的发展建议,对于进一步提高我国铁路工程物资采购与供应管理水平具有一定借鉴意义。     

远程无线铁路信号灯监控系统设计与实现

摘 要：GPRS无线通信网络技术的发展,使得远程无线监控系统能够实现并推广应用。同时由于基于.NET的人机交互界面的普及,便于查看和监控整个监控系统的运行状态。基于此,应用C/S模式和套接字网络编程技术,本文提出并实现了远程无线通信网络在铁路信号灯监控系统中的应用,以满足当前铁路信号灯监控系统的实时性、可靠性等新的需求。     

一种新的列车编组问题优化模型及算法

列车编组计划是编组站完成列车调度和组织工作的指导性文件之一,编制科学的列车编组计划是提高运输效率的重要保证。本文主要探讨了列车编组计划问题的建模、模型计算与求解的方法、编组计划的制定等问题。首先根据某站一天过站列车的数据,以白班和夜班的最小中时为指标,建立了列车解体和编组的优化模型。然后利用遗传算法和Matlab遗传算法工具箱对其进行了求解,最后给出了该站的列车解体计划和编组方案。     

三叶鬼针草和胜红蓟的叶浸提液对旱稻种子萌发的影响

通过测定旱稻种子萌发率、根长、苗高、根系活力、过氧化物酶(POD)活性、超氧化物歧化酶(SOD)活性等6项生理指标,研究了三叶鬼针草和胜红蓟的叶浸提液对旱稻种子萌发的影响。结果表明:三叶鬼针草和胜红蓟的叶浸提液对旱稻种子萌发具有抑制作用。在较低浓度下,两种植物的叶浸提液降低了旱稻种子的萌发率,抑制了幼苗根和茎的生长,降低幼苗的根系活力,提高了POD和SOD的活性,从而抑制旱稻种子萌发及生长。综合各项指标,在相同浸提液浓度下,胜红蓟对旱稻种子萌发及生长抑制作用更强。     

天津市软土地层地铁盾构区间下穿施工对京沪高铁南仓特大桥影响的数值分析

为研究天津地区软土地层隧道盾构区间下穿施工对京沪高铁南仓特大桥的影响,以下穿京沪高铁的天津地铁7号线外院附中站-榆关道站区间隧道工程为背景,对下穿京沪高铁南仓特大桥段区间盾构隧道进行设计,通过运用Midas/GTS有限元软件数值分析方法对盾构区间下穿京沪高铁南仓特大桥进行有限元数值分析。研究盾构区间下穿京沪高铁南仓特大桥施工过程中桥面、桥墩、承台及桥桩位移变化规律特征。总结盾构区间侧穿桥桩施工过程中桥桩附加应力变化规律;揭示了盾构区间下穿京沪高铁特大桥施工过程中承台差异沉降及地层应力变化规律。结果表明,盾构隧道施工过程中京沪高铁天津南仓特大桥桥桩附加弯矩较小,桥面、承台、桥墩及桥桩沉降最大值均在控制标准值范围以内,桥桩水平位移最大值在控制标准值范围以内,不会对大桥产生破坏影响。可见在软土地区盾构施工对高铁特大桥有一定程度影响,但通过施加工程措施后,可有效降低对桥的影响程度,保证高铁桥的安全。研究成果可为类型工程施工设计提供参考。     

基于生态系统稀缺性与生物量损失的道路选线方法

道路工程的建设对生态环境造成了一定的影响,导致了生态系统的破碎化,定量评价道路建设对生态系统造成的损失对道路设计和规划具有重要的参考价值。道路线路的选择直接决定着对生态系统影响程度的大小,因此道路方案的比选分析对生物多样性保护而言具有很重要的参考价值。以临策铁路天鹅湖至额济纳段线路为研究对象,利用生态系统稀缺性和生物量损失为评价指标,分析不同线路方案对生态系统造成的损失。结果表明:临策铁路天鹅湖至额济纳段绕避胡杨林保护区方案与其他三个方案相比,对生态系统造成的损失最小,为最优方案。