A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the...A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.展开更多
Short pitch corrugation has been a problem for railways worldwide over one century.In this paper,a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insight...Short pitch corrugation has been a problem for railways worldwide over one century.In this paper,a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation.A three-dimensional finite element vehicle-track dynamic interaction model is employed,which considers the coupling between the structural dynamics and the contact mechanics,while the damage mechanism is assumed to be differential wear.Various fastening models with different configurations,boundary conditions,and parameters of stiffness and damping are built up and analysed.These models may represent different service stages of fastenings in the field.Besides,the effect of train speeds on corrugation features is studied.The results indicate:(1)Fastening parameters and modelling play an important role in corrugation formation.(2)The fastening longitudinal constraint to the rail is the major factor that determines the corrugation formation.The fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components.(3)The strengthening of fastening constraints in the longitudinal dimension helps to mitigate corrugation.Meanwhile,the inner fastening constraint in the lateral direction is necessary for corrugation alleviation.(4)The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation propensity.The simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength components.It can also explain the field data with respect to the small variation between the corrugation wavelength and train speed,which is caused by frequency selection and jump between rail longitudinal compression modes.展开更多
科学的轨道交通出行模式分析是运营决策优化的重要依据。为挖掘城市轨道交通时空流动特征及其影响机理,提出一种基于非负张量分解的OD客流强度时空分布计算方法,采用融合SHAP归因分析的极端梯度提升树(eXtreme Gradient Boosting,XGBoo...科学的轨道交通出行模式分析是运营决策优化的重要依据。为挖掘城市轨道交通时空流动特征及其影响机理,提出一种基于非负张量分解的OD客流强度时空分布计算方法,采用融合SHAP归因分析的极端梯度提升树(eXtreme Gradient Boosting,XGBoost)对各模式OD客流强度进行拟合预测。使用城市轨道交通AFC(automatic fare collection system,AFC)系统数据,从空间、时段以及出行日3个维度构建3阶客流OD张量,采用交替非负最小二乘法(alternating non negative least squares,ANLS)实现非负CP张量分解。基于张量分解结果,从北京轨道交通344个站点连续1周16266966条出行数据中,提取出晨高峰长距离通勤、早高峰中短通勤、平峰休闲中转出行、晚归出行4种出行模式的时、空分布特征。基于可解释性机器学习模型,对各模式OD客流进行预测。结果表明XGBoost与CatBoost、LightGBM、OLS相比更具优势。根据OD起终点站域环境特征,考虑起终点缓冲区内各类兴趣点(point of interest,POI)数量、小区住户数、房价、人口数量、站点偏离距离以及出行距离等指标,构建OD强度关联指标体系,解释各指标对OD客流强度的正负反馈效应。SHAP归因分析说明,居民更倾向于14站以内的中短途出行,并分别得到了就业类POI数目对晨、早通勤客流正向影响,以及餐饮类POI数目对休闲中转出行客流正向影响的临界阈值。该方法可为轨道交通精细化出行引导和客流组织提供数据支撑,优化城市轨道交通供需平衡及服务水平。展开更多
In recent years, urban rail transit （URT） systems have rapidly developed in China, however, their existing strategies for vehicle maintenance are still based on experiential and qualitative methods which result in e...In recent years, urban rail transit （URT） systems have rapidly developed in China, however, their existing strategies for vehicle maintenance are still based on experiential and qualitative methods which result in either high cost or emergencies. In this paper, a tentative attempt at introducing the fuzzy set theory into quantitative analysis and assessment of URT trains＇ failures was presented. Based on the proposed FMEA-fuzzy model, a com- puter aided system for URT maintenance optimization was developed. The overall structure and procedure of the system were described in detail, and the important issues, including the development environment, improvement to FMEA table, acquisition of weight distribution matrix P, and setting of fuzzy vector R, were also discussed. Initial application into the vehicle maintenance of Shanghai Metro System shows, that the proposed model and computer aided system have a good performance and consequently are worth further development.展开更多
为揭示地铁运营突发中断下滞留乘客出行方式选择机制,明确关键情境因素的影响,基于情境模拟与陈述性偏好调查(Stated Preference,SP)构建考虑方式自身属性的基准多项Logit模型,采用逐步效用修正方法,量化预计恢复时间、天气、出行时间...为揭示地铁运营突发中断下滞留乘客出行方式选择机制,明确关键情境因素的影响,基于情境模拟与陈述性偏好调查(Stated Preference,SP)构建考虑方式自身属性的基准多项Logit模型,采用逐步效用修正方法,量化预计恢复时间、天气、出行时间与目的、剩余行程距离、人群条件及绕行线路可用性对乘客决策影响强度与作用模式,并结合似然比检验(Likelihood Ratio Test,LRT)、赤池信息准则(Akaike Information Criterion,AIC)、贝叶斯信息准则(Bayesian Information Criterion,BIC)与预测误差率评估模型改进效果.研究结果表明:乘客决策表现出强烈的情境依赖与风险厌恶特征;各情境因素作用强度显著不同,其中预计恢复时间影响最大(LR=183.98,预测误差下降1.94%),天气条件次之(LR=102.63,误差下降1.16%),出行目的与剩余行程距离也存在一定影响,周围人群行为与绕行线路可用性则未表现出显著影响;对各公共交通方式的偏好变化具有相似性;而原地等待作为被动选项虽有相当选取率,但在系统风险与情境风险叠加时显著降低;不同交通方式对情境因素敏感度差异明显,确定性高、风险低的方式在突发情境中更具吸引力.展开更多
基金supported by the National Natural Science Foundation of China(No.51275429)
文摘A finite element vibration model of a multiple wheel-rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self- excited oscillation of the wheel-rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.
文摘Short pitch corrugation has been a problem for railways worldwide over one century.In this paper,a parametric investigation of fastenings is conducted to understand the corrugation formation mechanism and gain insights into corrugation mitigation.A three-dimensional finite element vehicle-track dynamic interaction model is employed,which considers the coupling between the structural dynamics and the contact mechanics,while the damage mechanism is assumed to be differential wear.Various fastening models with different configurations,boundary conditions,and parameters of stiffness and damping are built up and analysed.These models may represent different service stages of fastenings in the field.Besides,the effect of train speeds on corrugation features is studied.The results indicate:(1)Fastening parameters and modelling play an important role in corrugation formation.(2)The fastening longitudinal constraint to the rail is the major factor that determines the corrugation formation.The fastening vertical and lateral constraints influence corrugation features in terms of spatial distribution and wavelength components.(3)The strengthening of fastening constraints in the longitudinal dimension helps to mitigate corrugation.Meanwhile,the inner fastening constraint in the lateral direction is necessary for corrugation alleviation.(4)The increase in fastening longitudinal stiffness and damping can reduce the vibration amplitudes of longitudinal compression modes and thus reduce the track corrugation propensity.The simulation in this work can well explain the field corrugation in terms of the occurrence possibility and major wavelength components.It can also explain the field data with respect to the small variation between the corrugation wavelength and train speed,which is caused by frequency selection and jump between rail longitudinal compression modes.
文摘科学的轨道交通出行模式分析是运营决策优化的重要依据。为挖掘城市轨道交通时空流动特征及其影响机理,提出一种基于非负张量分解的OD客流强度时空分布计算方法,采用融合SHAP归因分析的极端梯度提升树(eXtreme Gradient Boosting,XGBoost)对各模式OD客流强度进行拟合预测。使用城市轨道交通AFC(automatic fare collection system,AFC)系统数据,从空间、时段以及出行日3个维度构建3阶客流OD张量,采用交替非负最小二乘法(alternating non negative least squares,ANLS)实现非负CP张量分解。基于张量分解结果,从北京轨道交通344个站点连续1周16266966条出行数据中,提取出晨高峰长距离通勤、早高峰中短通勤、平峰休闲中转出行、晚归出行4种出行模式的时、空分布特征。基于可解释性机器学习模型,对各模式OD客流进行预测。结果表明XGBoost与CatBoost、LightGBM、OLS相比更具优势。根据OD起终点站域环境特征,考虑起终点缓冲区内各类兴趣点(point of interest,POI)数量、小区住户数、房价、人口数量、站点偏离距离以及出行距离等指标,构建OD强度关联指标体系,解释各指标对OD客流强度的正负反馈效应。SHAP归因分析说明,居民更倾向于14站以内的中短途出行,并分别得到了就业类POI数目对晨、早通勤客流正向影响,以及餐饮类POI数目对休闲中转出行客流正向影响的临界阈值。该方法可为轨道交通精细化出行引导和客流组织提供数据支撑,优化城市轨道交通供需平衡及服务水平。
基金supported by the Research Program of Science and Technology Commission in Shanghai under Grant No.10dz1122701
文摘In recent years, urban rail transit （URT） systems have rapidly developed in China, however, their existing strategies for vehicle maintenance are still based on experiential and qualitative methods which result in either high cost or emergencies. In this paper, a tentative attempt at introducing the fuzzy set theory into quantitative analysis and assessment of URT trains＇ failures was presented. Based on the proposed FMEA-fuzzy model, a com- puter aided system for URT maintenance optimization was developed. The overall structure and procedure of the system were described in detail, and the important issues, including the development environment, improvement to FMEA table, acquisition of weight distribution matrix P, and setting of fuzzy vector R, were also discussed. Initial application into the vehicle maintenance of Shanghai Metro System shows, that the proposed model and computer aided system have a good performance and consequently are worth further development.
文摘为揭示地铁运营突发中断下滞留乘客出行方式选择机制,明确关键情境因素的影响,基于情境模拟与陈述性偏好调查(Stated Preference,SP)构建考虑方式自身属性的基准多项Logit模型,采用逐步效用修正方法,量化预计恢复时间、天气、出行时间与目的、剩余行程距离、人群条件及绕行线路可用性对乘客决策影响强度与作用模式,并结合似然比检验(Likelihood Ratio Test,LRT)、赤池信息准则(Akaike Information Criterion,AIC)、贝叶斯信息准则(Bayesian Information Criterion,BIC)与预测误差率评估模型改进效果.研究结果表明:乘客决策表现出强烈的情境依赖与风险厌恶特征;各情境因素作用强度显著不同,其中预计恢复时间影响最大(LR=183.98,预测误差下降1.94%),天气条件次之(LR=102.63,误差下降1.16%),出行目的与剩余行程距离也存在一定影响,周围人群行为与绕行线路可用性则未表现出显著影响;对各公共交通方式的偏好变化具有相似性;而原地等待作为被动选项虽有相当选取率,但在系统风险与情境风险叠加时显著降低;不同交通方式对情境因素敏感度差异明显,确定性高、风险低的方式在突发情境中更具吸引力.
