【作者】 张田；

【导师】 夏禾； 郭薇薇；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 风灾是影响铁路运营安全的主要自然灾害之一,尤其是我国西北地区,铁路经过几大风区,时常发生列车停驶或倾覆事故,是我国乃至世界上铁路风灾最严重的地区。建于大风区的桥梁,受到风力的激扰会产生强烈的振动,同时,高速运行的列车在强劲的横向风压作用下,在桥上脱轨、倾覆的可能性大大增加。因此,对风荷载作用下车辆与桥梁耦合振动系统进行综合研究,并采取防风措施以确保列车在桥上的运行安全性,对于风区铁路桥梁和防风措施的设计建造具有重要的理论和工程意义。本文以在建的兰新铁路第二双线为研究背景,旨在建立一种合理的分析框架,对风荷载作用下车辆与桥梁耦合系统的振动响应做出估计,以便评价桥梁的动力性能和桥上高速列车的走行性能。同时对提高列车运行安全的防风结构进行研究,使桥梁在强风发生时尽量少甚至不限制行车。全文的主要内容及成果如下：(1)通过对国内外风致列车事故进行综述,阐明了风场中防护列车安全的重要性。然后对车桥耦合振动、风致桥梁振动、风场中车桥系统振动分析以及风场中列车运行安全性和防风措施的研究现状进行了归纳总结,明确了现阶段风—车一桥系统动力分析和防风措施研究的热点问题,在继承前人工作的基础上确定了本文的研究内容及主要方法。(2)对桥址区的风场特性进行了分析,并采用改进的数值方法模拟了桥址区脉动风速时程曲线。分析了风场的平均风特性和脉动风特性以及地形、地貌对风特性的影响,着重分析了大风区兴建的兰新铁路第二双线上桥梁所处的风环境,戈壁地区的风沙流特性及其对防风屏障的影响。详述了随机脉动风场的数值模拟计算公式,并以白杨河连续梁桥桥面及桥墩各点风速模拟为例加以实现。(3)对防风屏障进行了初步选型并分析了防风屏障对车桥系统气动性能的影响。根据计算流体力学(CFD)的相关原理,选择合适的湍流模型对气流经过防风屏障这一空气动力学问题进行数值模拟,针对几种防风屏障的设计方案,分析了不同设计参数(包括开孔率、高度等)的防风屏障对风速的影响规律,对桥上防风屏障的防风效果及有效防护区域进行定量分析,初步探讨防风屏障的合理形式和主要设计参数的合理取值。任何形式的防风屏障,都会对桥面风场产生影响,加强紊流效应,使桥梁结构周围风场更加复杂,当列车驶过时作用于列车上的风荷载与没有设置防风屏障时有明显区别,尤其是在列车的背风侧。(4)建立了考虑桥上安装防风屏障时风荷载作用下车桥系统动力相互作用分析模型,编制了相应的计算分析程序。针对桥上安装不同类型风屏障的情况,考虑风—车—桥—风屏障系统的动力相互作用,计算了强风与列车共同作用下桥梁和列车的动力响应及行车安全性指标,相较于无风屏障时,差异明显。以兰新铁路第二双线上的10跨简支箱梁桥为例,分为无风屏障、全段安装单侧4m风屏障、单侧7m风屏障及双侧7m风屏障四种情形,计算分析不同风速、不同车速条件下的车桥动力响应。(5)推导了列车进出防风屏障时车体上的风荷载变化计算公式,讨论了风载突变对列车运行安全的影响；并且计算了列车运行引起的风屏障上的气动脉冲力,将其作用于风屏障进行时程分析,得到风屏障的动力响应,同时考虑了外部自然风的作用。以兰新铁路第二双线上的10跨简支箱梁桥为例,在桥上200m区段安装单侧4m风屏障、单侧7m风屏障和双侧7m风屏障与无风屏障及全段安装同样风屏障时车辆的动力响应及行车安全性指标进行对比；计算了单侧4m风屏障在自然风荷载、气动脉冲力荷载以及二者组合时关键节点的动力响应。(6)基于自编的计算分析程序,计算了兰新铁路第二双线上常用跨度简支箱梁桥、简支T梁桥、简支槽梁桥以及白杨河连续梁桥列车运行时车辆、桥梁的动力响应,考虑桥上全段安装风屏障和桥上部分区段安装风屏障等不同情况。根据列车走行性能的评价方法和指标,计算了不同风速下列车的最大安全运行速度,提出了风场中安装不同风屏障的桥梁上列车安全运行车速阈值曲线。更多还原

【Abstract】 Wind disaster is one of the main natural disasters that affect the operation safety of the railway. Especially in the northwest region in China, which is one of the most serious wind disaster areas of railways in China as well as in the world, the railway lines pass through some strong wind areas, where the train service is often interrupted by the wind and the train overturn accidents occasionally occur.The bridges located in the strong wind area vibrate intensively when subjected to the wind force excitation. The strong lateral wind pressure acting on the high-speed train running on the bridge greatly increases the possibility of the train derailment or overturning. Therefore, it has the significant theoretical meaning and the practical engineering value to perform comprehensive research on the dynamic responses of vehicle-bridge system under wind loads and windproof measures. This is an important issue to ensure the running safety of the train on the bridge, and to guide the design and construction of railway bridges and windbreak structures in the wind area. With the new built Lanzhou-xinjiang railway as a research background, this paper aims to establish a rational analysis framework to estimate the vibration response of the coupled vehicle-bridges system in the wind field, so as to evaluate the dynamic performance of the bridge and the high-speed train running safety. At the same time, the windbreak structures are studied to improve the running safety of the train, so that the traffic on the bridge can be interrupted as little as possible when strong wind occurs.The main research contents and results are given as follows:(1) The wind-induced train accidents at home and abroad are described to show the importance of the train safety protection in wind field. Then the current research statuses are summarized for the vehicle-bridge coupled vibration, wind-induced bridge vibration, and wind-vehicle-bridge system, running safety of the train and windbreak measures. Furthermore, the current focused problems are proposed on the dynamic analysis of wind-vehicle-bridge system and windbreak measures, and the research content and method in this paper are clarified on the basis of the previous work.(2) The wind field characteristics of bridge sites are analyzed, and the fluctuating wind speed time histories on the bridge sites are simulated by the improved numerical method. Firstly, the wind is represented as the mean wind component with the time invariant characteristic and the turbulent wind component with the time varying characteristic, and the influence of the landform and topography on the wind field is discussed. Especially, the wind environment of the bridge in the new Lanzhou-Xinjiang railway line is analyzed and the wind-sand flow characteristic in the Gobi desert area and the effect on the wind barriers are described. Then the numerical calculation formulae of the random fluctuating wind field are derived in detail, and the wind speed time histories of the bridge deck and pier on the Baiyang River Bridge are simulated.(3) The preliminary form selection for wind barriers and the effect of wind barriers on the aerodynamic performance of the vehicle-bridge system are studied. According to the correlation principle of computational fluid dynamics, the aerodynamic characteristic for the airflow through the wind barrier is analyzed by the numerical simulation method with an applicable turbulence model. The numerical simulation is performed for several different types of wind barriers on bridge. The influence rules of wind velocity are researched. The windbreak effect and the effective protection area of wind barriers are quantitatively analyzed with different heights and different porosity percentage, to determine the reasonable type of the wind barrier and the main design parameters. Any kind of wind barrier may have an impact on the wind field on bridge deck and increase the turbulence effects, which makes the wind field around the bridge structure more complex. When the train travels on the bridge with or without wind barriers, the wind load acting on the train is very different, especially in the leeward side of the train.(4) The dynamic interaction analysis model of vehicle-bridge system is established and the corresponding computation program is developed. For different types of wind barriers, considering the wind-vehicle-bridge-barrier interaction, the dynamic responses of the bridge and the running safety indices of the train are calculated under the strong wind and running train. Compared to the case without wind barrier on the bridge, the results are obvious. Taking a10-span simply-supported box girder bridge in the new built Lanzhou-xinjiang railway line for example, the dynamic responses of the train and the bridge are calculated at different train speed and wind velocity under the cases without barrier and with single-side4m barrier, single-side7m barrier and double-side7m barrier on the whole bridge.(5) The calculation formulae for wind load change acting on the car-body are derived when the train moves into or out of the wind barrier structure, and then the influence of the sudden change of wind load on the running safety is discussed. Meanwhile, the aerodynamic pulse force caused by the running train on the wind barrier is obtained, and then the time historic analysis method is used for the dynamic response of the wind barrier under the pulse force as well to external natural wind load. Taking the10-span simply-supported box girder bridge for example, the response and the running safety indices of the train are given under the cases of200m long single-side4m barrier, single-side7m barrier and double-side7m barrier of the same section on the bridge. These results are compared with those of the cases without barrier and wind barriers on the whole bridge. And the dynamic response of the key nodes of the single-side4m wind barrier is calculated under the natural wind load, or the aerodynamic pulse load as well as the combination of both.(6) An analysis program is written, based on which the dynamic responses of the vehicle and the bridge are obtained when the train passes through the common span simply-supported box girder bridge, simply-supported T-shaped girder bridge, simply-supported U-shaped girder bridge or Baiyang River continuous beam bridge. In the analysis, the cases both with the wind barrier on the whole bridge and only partial section of the bridge are considered. Then according to the evaluating method and the running safety indices, the maximum safety speeds are obtained at different wind velocities, based on which the train speed threshold curves are proposed when the train runs on the bridge with different types of wind barriers.更多还原