Measured dynamic load distribution within the in situ axlebox bearing of high-speed trains under polygonal wheel–rail excitation

The dynamic load distribution within in-service axlebox bearings of high-speed trains is crucial for the fatigue reliability assessment and forward design of axlebox bearings. This paper presents an in situ measurement of the dynamic load distribution in the four rows of two axlebox bearings on a bogie wheelset of a high-speed train under polygonal wheel–rail excitation. The measurement employed an improved strain-based method to measure the dynamic radial load distribution of roller bearings. The four rows of two axlebox bearings on a wheelset exhibited different ranges of loaded zones and different means of distributed loads. Besides, the mean value and standard deviation of measured roller–raceway contact loads showed non-monotonic variations with the frequency of wheel–rail excitation. The fatigue life of the four bearing rows under polygonal wheel–rail excitation was quantitatively predicted by compiling the measured roller–raceway contact load spectra of the most loaded position and considering the load spectra as input.

Modeling and simulation of high-speed passenger train movements in the rail line

In this paper, we propose a new formula of the real-time minimum safety headway based on the relative velocity of consecutive trains and present a dynamic model of high-speed passenger train movements in the rail line based on the proposed formula of the minimum safety headway. Moreover, we provide the control strategies of the high-speed passenger train operations based on the proposed formula of the real-time minimum safety headway and the dynamic model of highspeed passenger train movements. The simulation results demonstrate that the proposed control strategies of the passenger train operations can greatly reduce the delay propagation in the high-speed rail line when a random delay occurs.

Running safety assessment method of trains under seismic conditions based on the derailment risk domain

The accurate assessment of running safety during earthquakes is of significant importance for ensuring the safety of railway lines.Currently,assessment methods based on a single index suffer from issues such as misjudgment of operational safety and difficulty in evaluating operational margin,making them unsuitable for assessing train safety during earthquakes.Therefore,in order to propose an effective evaluation method for the running safety of trains during earthquakes,this study employs three indexes,namely lateral displacement of the wheel–rail contact point,wheel unloading rate,and wheel lift,to describe the lateral and vertical contact states between the wheel and rail.The corresponding evolution characteristics of the wheel–rail contact states are determined,and the derailment forms under different frequency components of seismic motion are identified through dynamic numerical simulations of the train–track coupled system under sine excitation.The variations in the wheel–rail contact states during the transition from a safe state to the critical state of derailment are analyzed,thereby constructing the evolutionary path of train derailment and seismic derailment risk domain.Lastly,the wheel–rail contact and derailment states under seismic conditions are analyzed,thus verifying the effectiveness of the evaluation method for assessing running safety under earthquakes proposed in this study.The results indicate that the assessment method based on the derailment risk domain accurately and comprehensively reflects the wheel–rail contact states under seismic conditions.It successfully determines the forms of train derailment,the risk levels of derailment,and the evolutionary paths of derailment risk.

Last train timetable optimization for metro network to maximize the passenger accessibility over the end-of-service period

Purpose-This study aims to improve the passenger accessibility of passenger demands in the end-ofoperation period.Design/methodology/approach-A mixed integer nonlinear programming model for last train timetable optimization of the metro was proposed considering the constraints such as the maximum headway,the minimum headway and the latest end-of-operation time.The objective of the model is to maximize the number of reachable passengers in the end-of-operation period.A solution method based on a preset train service is proposed,which significantly reduces the variables of deciding train services in the original model and reformulates it into a mixed integer linear programming model.Findings-The results of the case study of Wuhan Metro show that the solution method can obtain highquality solutions in a shorter time;and the shorter the time interval of passenger flow data,the more obvious the advantage of solution speed;after optimization,the number of passengers reaching the destination among the passengers who need to take the last train during the end-of-operation period can be increased by 10%.Originality/value-Existing research results only consider the passengers who take the last train.Compared with previous research,considering the overall passenger demand during the end-of-operation period can make more passengers arrive at their destination.Appropriately delaying the end-of-operation time can increase the proportion of passengers who can reach the destination in the metro network,but due to the decrease in passenger demand,postponing the end-of-operation time has a bottleneck in increasing the proportion of passengers who can reach the destination.

A simulation model for estimating train and passenger delays in large-scale rail transit networks

A simulation model was proposed to investigate the relationship between train delays and passenger delays and to predict the dynamic passenger distribution in a large-scale rail transit network. It was assumed that the time varying original-destination demand and passenger path choice probability were given. Passengers were assumed not to change their destinations and travel paths after delay occurs. CapaciW constraints of train and queue rules of alighting and boarding were taken into account. By using the time-driven simulation, the states of passengers, trains and other facilities in the network were updated every time step. The proposed methodology was also tested in a real network, for demonstration. The results reveal that short train delay does not necessarily result in passenger delays, while, on the contrary, some passengers may get benefits from the short delay. However, large initial train delay may result in not only knock-on train and passenger delays along the same line, but also the passenger delays across the entire rail transit network.

A Control Simulation Method of High-Speed Trains on Railway Network with Irregular Influence

Based on the discrete time method, an effective movement control model is designed for a group of high- speed trains on a rail network. The purpose of the model is to investigate the specific traffic characteristics of high-speed trains under the interruption of stochastic irregular events. In the model, the high-speed rail traffic system is supposed to be equipped with the moving-block signalling system to guarantee maximum traversing capacity of the railway. To keep the safety of trains＇ movements, some operational strategies are proposed to control the movements of trains in the model, including traction operation, braking operation, and entering-station operation. The numerical simulations show that the designed model can well describe the movements of high-speed trains on the rail network. The research results can provide the useful information not only for investigating the propagation features of relevant delays under the irregular disturbance but also for rerouting and reseheduling trains on the rail network.

Minimum Curve Radii for High-Speed Trains, Including the Gyroscopic Moments of the Wheels

This paper studies the title problem including an analysis of the gyroscopic effects of the wheels of a rail-car travelling at high-speed around a level, horizontal curve. The analysis is based upon the fundamental principles of dynamics. The result is a design formula for the minimum curve radius needed to prevent derailment. Aside from the rail car geometric and physical properties, the minimum curve radius depends upon the square the train speed. An illustrative example shows that the wheel gyroscopic effect is destabilizing and additive to the centrifugal force derailment tendency. From a track design perspective, however, the gyroscopic effect is relatively small compared with the centrifugal force effect.

Influence of Random Track Irregularities on Dynamic Response of Bridge/Track Structure/High-Speed Train Systems

Random vertical track irregularities are one of essential vibration sources in bridge, track structure and high-speed train systems. The common model of such irregularities is a stationary and ergodic Gaussian process. The study presents the results of numerical dynamic analysis of advanced virtual models of composite BTT （bridge/ballasted track structure/high-speed train） systems. The analysis has been conducted for a series of types of single-span simply-supported railway composite （steel-concrete） bridges, with a symmetric platform, located on lines with ballasted track structure adapted for high-speed trains. The bridges are designed according to Polish bridge standards. A new methodology of numerical modeling and simulation of dynamic processes in BTT systems has been applied. The methodology takes into consideration viscoelastic suspensions of rail-vehicles, nonlinear Hertz wheel-rail contact stiffness and one-side wheel-rail contact, physically nonlinear elastic-damping properties of the track structure, random vertical track irregularities, approach slabs and other features. Computer algorithms of FE （finite element） modeling and simulation were programmed in Delphi. Both static and dynamic numerical investigations of the bridges forming the series of types have been carried out. It has been proved that in the case of common structural solutions of bridges and ballasted track structures, it is necessary to put certain limitations on operating speeds, macadam ballast and vertical track roughness.

Numerical study of wheel–rail adhesion performance of new-concept high-speed trains with aerodynamic wings

Wheel–rail adhesion is a complex tribological problem of wheel–rail rolling contact and is closely related to the operational safety of high-speed trains.A new design concept of high-speed trains was recently proposed with an expectation of a reduction of equivalent weight and total energy consumption by installing aerodynamic wings(aero-wings)on the roof,but it was accompanied by the disadvantage of deteriorating wheel–rail adhesion performance.In this study,a comprehensive multibody dynamics(MBD)model of the high-speed train with predesigned aero-wings is established using the commercial software SIMPACK,in which the real aerodynamic characteristics of the train are taken into account.The available adhesion and adhesion margin are employed to evaluate the wheel–rail adhesion performance.The influences of aero-wing lift,train speed,and contact conditions on the wheel–rail adhesion level are discussed.The results show that the load transfer caused by the action of aerodynamic load and braking torque was the main reason for the inconsistent adhesion condition of four wheelsets.The influences of aero-wing lift and train speed on the wheel–rail adhesion performance are coupled;the available adhesion of both motor car and trailer is negatively correlated with aero-wing lift and train speed under all contact conditions,while the variation law of adhesion margin with train speed shows differences under different contact conditions.When the wheel–rail interface was polluted by a‘third-body medium’such as water and oil,the wheel–rail adhesion performance was dramatically reduced and the wheelset tended to reach adhesion saturation and slide.However,track irregularity had little effect on the adhesion performance and could be ignored to save calculation time.These results are of positive significance for reducing the wheel idling or sliding phenomenon and to ensure the safe operation of high-speed trains with aero-wings.

Coupling analysis of passenger and train flows for a large-scale urban rail transit system

Coupling analysis of passenger and train flows is an important approach in evaluating and optimizing the operation efficiency of large-scale urban rail transit(URT)systems.This study proposes a passenger–train interaction simulation approach to determine the coupling relationship between passenger and train flows.On the bases of time-varying origin–destination demand,train timetable,and network topology,the proposed approach can restore passenger behaviors in URT systems.Upstream priority,queuing process with first-in-first-serve principle,and capacity constraints are considered in the proposed simulation mechanism.This approach can also obtain each passenger’s complete travel chain,which can be used to analyze(including but not limited to)various indicators discussed in this research to effectively support train schedule optimization and capacity evaluation for urban rail managers.Lastly,the proposed model and its potential application are demonstrated via numerical experiments using real-world data from the Beijing URT system(i.e.,rail network with the world’s highest passenger ridership).

Optimization method of urban rail train operational plan based on O-D time-varying demand

Purpose–Under the constraints of given passenger service level and coupling travel demand with train departure time,this study optimizes the train operational plan in an urban rail corridor to minimize the numbers of train trips and rolling stocks considering the time-varying demand of urban rail passenger flow.Design/methodology/approach–The authors optimize the train operational plan in a special network layout,i.e.an urban rail corridor with dead-end terminal yard,by decomposing it into two sub-problems:train timetable optimization and rolling stock circulation optimization.As for train timetable optimization,the authors propose a schedule-based passenger flow assignment method,construct the corresponding timetabling optimization model and design the bi-directional coordinated sequential optimization algorithm.For the optimization of rolling stock circulation,the authors construct the corresponding optimization assignment model and adopt the Hungary algorithm for solving the model.Findings–The case study shows that the train operational plan developed by the study’s approach meets requirements on the passenger service quality and reduces the operational cost to the maximum by minimizing the numbers of train trips and rolling stocks.Originality/value–The example verifies the efficiency of the model and algorithm.

考虑动态随机客流的城市轨道交通列车时刻表仿真优化

为更加精准刻画动态随机客流与列车时刻表编制间的复杂匹配过程,综合考虑乘客动态随机到达过程、列车容量限制、车内拥挤度对乘客上下车速率影响、停站时间动态调整和列车运行安全防护等重要运营特征,构建城市轨道交通列车运行离散仿真模型。在此基础上,建立以最小化乘客平均候车时间为目标的随机非线性优化模型,并设计一种基于仿真的有限差分随机逼近算法,用于优化城市轨道交通发车方案。以国内某条线路的实际运营数据为例验证仿真模型及优化方法,结果表明所构建模型及算法具有较好的优化效果和计算效率,优化后的列车实绩运行时刻能更好地适应客流需求的动态随机性,且在不增加发车频次的前提下有效降低乘客平均候车时间,提升城市轨道交通运营管理水平。

基于乘客服务水平和安全的城市轨道交通扣车方案评价

[目的]扣车是城市轨道交通发生长时间初始延误条件下经常采用的列车运行方案。为了评价该方案的合理性,需构建基于乘客服务和安全的扣车方案评价模型,并对扣车方案进行评价。[方法]考虑到乘客出行规律的复杂性和特殊性,制定了城市轨道交通扣车方案。构建了基于最大发车间隔、列车总延误时间、列车均衡性、终到延误列车数、滞留乘客数及乘客总旅行时间的扣车方案评价模型。选取上海某条轨道交通线路的4个区间,以早高峰小时的实际OD(起讫点)客流量为例进行计算。[结果及结论]计算表明,方案6下的综合评价指标最小,为最优扣车调整方案。该方案可以有效提高列车运行图的均衡性,减少滞留乘客的数量,降低车站的安全隐患。

基于可预知大客流的城市轨道交通列车加开计划调整模型与算法

[目的]节假日、大型文体活动等事件会导致城市轨道交通线路产生可预知大客流,需在确保列车运行安全的前提下,根据客流预测情况在已有列车运行图中加开列车,以期在运营成本、运营组织复杂度和乘客服务水平之间取得平衡。[方法]采用事件-活动网络,对列车运行过程进行了形式化描述,建立了3个目标函数及相关的约束条件,进而构建了独立运用策略下列车加开计划调整模型、套跑混合运用策略下列车加开计划调整模型。在此基础上,提出了基于混合遗传禁忌的搜索算法。结合深圳地铁11号线的实际运营数据,在高峰时段和非高峰时段分别建立了不同的算例场景,以验证所建模型和算法的有效性。[结果及结论]所建模型支持不同运营时段、不同运行交路、不同车底接续策略下列车加开需求,在可预知大客流的运营调整上具有适用性。在车辆资源相对有限的情况下,为有效缓解高峰时段的客流压力,可灵活采用大小交路套跑混合运用策略,使线路的运输能力最大化。

基于加线技术的轨道交通临客开行计划优化模型

基于运行图加线技术构建适于计划性临客开行的运行线铺画方法.以运力与客流匹配度最大化、对原运行图调整最小化为优化目标,考虑行车安全、临客加线位置、开行时间域等约束,构建临客运行线铺画非线性整数规划模型,并对其线性转换以提高求解效率.以北京地铁8号线某大型活动散场大客流为场景进行案例分析,结果表明:所构建方法能够在既有运行图上有效铺画临客运行线,满足不同行车密度及停站模式下的临客开行需求.建议在较高密度行车条件下不采用“空车直达”停站模式.

基于虚拟编组的城轨列车时刻表优化方法

针对高峰时段城市轨道交通客流与运力不匹配问题,考虑城市轨道交通客流时空分布特征、交通过饱和状态和车场车底数量限制,提出了基于虚拟编组的城轨列车时刻表优化方法。构造动态客流累计需求函数,预测不同时段客流量;考虑乘客需求、发车间隔、运行时间、车底数量、车底接续等约束条件,以列车在首站的发车时刻和各车次的编组方案为决策变量,以乘客平均等待时间与列车走行里程最小化为优化目标,建立了基于虚拟编组的城轨列车时刻表优化模型。针对原问题包含大量耦合约束条件,利用拉格朗日松弛算法将耦合性约束吸收至目标函数,将原问题分解为2个独立路径的子问题,降低问题的复杂度;再利用商业求解器求解子问题的下界解,并设计启发式算法求解子问题的上界可行解,得到原问题解的上下界。以上海地铁某线路为算例进行验证,结果表明:在高峰时段,所提动态客流累计需求函数与客流实际到达规律拟合度较高;固定编组模式下,非均匀发车时刻表相比于均匀发车时刻表,可降低24.15%的乘客平均等待时间和51.73%的滞留乘客等待时间;而所提虚拟编组列车时刻表相比于固定编组模式下非均匀发车时刻表,不仅可减少0.33%的列车运行里程,还可进一步减少16.95%的乘客平均等待时间和6.03%的滞留乘客等待时间。

城市轨道交通快慢车运行延误调整方案仿真评价模型

[目的]制定合理的列车运行延误调整方案,是保证城市轨道交通线路运营安全、可靠的重点工作之一。对于开行快慢车的城市轨道交通线路,需要研究列车运行延误后乘客的选择列车行为,并分析快慢车越行对乘客出行选择的影响。[方法]对快慢车线路运行过程中乘客的留乘现象及乘客选择列车行为进行了分析,设计了符合乘客上下车规则和乘客选择列车行为的仿真算法,构建了快慢车运行延误调整方案仿真评价模型。考虑快慢车的始发时间、顺序,以及越行的车次、站点,制定了不同的列车运行延误调整方案。对上海轨道交通16号线原有的计划方案、4个延误调整方案下乘客的出行过程进行了仿真,并对4个延误调整方案进行了综合评价。[结果及结论]该仿真评价模型具有有效性和可靠性,既可为城市轨道交通运营企业评价列车开行方案提供仿真手段,也可为乘客服务水平提升、列车运能利用率提高、列车开行方案优化等提供依据。

北京市中心城区外地铁线路开行快慢车对策研究

随着城市化进程的进一步加快,城市居民对通勤出行的时效性要求越来越高,连接中心城与外围新城之间的地铁是主要的通勤交通线路,如何提高其旅行速度、缩短乘客旅行时间,成为急需研究的一个重要问题。为满足不同乘客对出行条件和服务效率的需求,提出通过开行快慢车实现旅速时间的节省。从既有客流特征入手,分析客流来源及目的地,指出既有线开行快慢车的必要性;在借鉴日本相关案例经验的基础上,对开行快慢车需要考虑的问题进行分析;以北京燕房线、房山线、15号线为例,分析不同线路的客流特征及线路条件,分别提出利用大行车间隔及设置越行线开行快慢车的方案;并提出两种方案的特点及实施要点。利用大行车间隔开行快慢车,即在客流较小的线路上利用富裕的能力开行快慢车,仅需对运营图进行优化设计,投资小;设置越行线开行快慢车,需根据工程实施条件、客流特征,选择合理的越行站点。经分析研究,采用两种方式均可实现节省旅行时间的目的,对提升中心城区外客流快速进城需求有积极的意义。

考虑高铁平行通道分工的列车开行方案优化

结合通道内及跨区域旅客运输需求,考虑城市内部旅客出行成本,构造旅客出行服务网络,以通道内列车开行成本和旅客总出行成本最小化为目标函数,构建了基于平行通道分工的列车开行方案优化模型。以济青通道内胶济客运专线和济青高速铁路构成的平行通道为案例,验证模型的有效性。结果表明,平行通道的合理分工可以降低出行系统总成本,同时更好满足旅客出行需求。

面向客流聚集风险防控的城轨列车实时调度模型与算法

“后疫情时代”下,我国城市轨道交通客流量快速反弹并进一步持续攀升。在此背景下,以缓解车站拥挤度为目标,研究面向客流聚集风险防控的列车实时调度问题具有重要的现实意义。在线路运营受到异常事件干扰条件下,结合列车跳停策略和运行图协同调整,以最小化线路车站拥挤度为目标函数,以车厢满载率为模型约束,建立列车实时调度混合整数线性规划模型。为提高模型求解效率,提出可变邻域搜索算法,首先基于线性规划松弛原理设计模型初始解的启发式计算规则,之后基于可变邻域搜索算法寻找初始解邻域内的近似最优解作为列车实时调度问题的最终解。使用北京地铁亦庄线实际数据进行了仿真实验,仿真结果表明:以标准“站站停”策略生成的运行图调整方案作为评价基准,采用可变邻域搜索算法计算得到的列车实时调度策略可降低线路拥挤度约67.56%,减少约38.28%的线路最大断面客流量,计算时间在1 min左右,可满足列车实时调度的需求,验证了本文提出的列车实时调度模型与求解算法能有效降低车站拥挤度、均衡线路客流的断面分布,对突发大客流带来的车站乘客聚集问题具有较好的调整效果。