纵向轨枕式无砟轨道界面裂缝对轨道力学性能的影响

纵向轨枕轨道结构改用预制混凝土纵梁连续支撑的结构设计,故预制轨枕与道床板的新旧混凝土界面是结构稳定分析不可回避的因素。为了分析新旧混凝土界面对整体结构的影响,并为纵向轨枕式无砟轨道设计提供相关参考,通过建立纵向轨枕式无砟轨道的二维有限元计算模型进行研究。结果表明:纵向轨枕式无砟轨道在列车荷载和温度变化作用下,轨枕与道床板界面附近会出现纵向裂缝,并裂缝加快扩展。界面裂缝对轨道内部应力分布影响很大,对钢轨扭转有一定影响。     

Standardization of capacity unit for headway-based rail capacity analysis

Determining the required capacity upgrades to accommodate future demand is a critical process in assisting public and private financing of capacity investments. Conventional railway systems usually operate multiple types of trains on the same track. These different types of trains can exert substantially different capacity impact, and can cause serious operational conflicts. In the past, rail line capacity is commonly defined as the maximum number of trains that can be operated on a section of track within a given time period. However, a specific unit (trains/hr or trains/day) does not reflect the heterogeneity of train types. According to the concept of base train equivalents (BTE) and base train unit (BTU), this study developed headway-based models to determine BTE for transforming different train types into a standard unit (i.e., BTU). An approximate method for lines with three and more types of trains was also proposed to compute BTEs for non-base trains. Results from the case studies demonstrate that this method enables the standardization of rail capacity unit, facilitates assessment of the impact from heterogeneous trains, and allows comparison and evaluation of the capacity measurements from different lines and systems.     

轨道交通梁式桥BIM辅助设计软件开发研究

为了满足轨道交通桥梁设计中的专业计算和建模需求,解决BIM桥梁正向设计实施困难的问题,结合轨道交通项目梁式桥的设计流程和操作习惯,提出以数据为依托的参数化解决方案。选取Bentley公司的Microstation软件进行轨道交通梁式桥设计程序开发,所开发的程序具有地质和线路专业资料获取、桥梁墩台及基础等构件管理、孔跨布置、墩台计算、一键式BIM模型创建、一键式计算和工程量清单输出等功能,为轨道交通桥梁BIM正向设计提供了有效的工具支撑。     

Applications of transport economics and imperfect competition

The great majority of analyses made in transport economics use, explicitly or, more often, implicitly, the common assumption of perfect competition. This is the case, for instance, when infrastructure projects are evaluated using the mere sum of the surpluses of transport users and providers. Even when putting aside the question of externalities such as noise, safety or environmental quality, the real chain of economic interactions that takes place in transport provision or downstream of transport provision is not taken into account. Surely enough, describing and simulating this chain could be quite complex. Nevertheless, it is not uninteresting to try to estimate if it does make a big difference or not to make this approximation. The paper makes such an attempt for two broad kinds of applications of transport economics:     

Life cycle assessment of High Speed Rail in China

China has built the world’s largest High Speed Rail (HSR) network. Its environmental impacts have been examined by the means of life cycle assessment (LCA) which describes the whole picture of the HSR system instead of single stages, with a case study for the high-speed railway that links Beijing and Shanghai. The research employs the China-specific life cycle inventory database Chinese Core Life Cycle Database (CLCD). Vehicle operation dominates most impact categories, while vehicle manufacturing/maintenance/disposal and infrastructure construction contribute mostly to mineral consumption (43% and 38%) and organic compounds in water (54% for infrastructure construction). Several scenarios are developed to explore effects of changes in HSR development, utilization, electricity mix, and infrastructure planning and construction. Suggestions are provided for improving the life cycle environmental performance of China’s HSR systems.     

Organizational effects of experience from accidents. Learning in the aftermath of the Tretten and Åsta train accidents

This article explores possible signs on learning in organizations following two major railway accidents in Norway, the Tretten accident in 1975 and the Åsta accident in 2000. These are the most serious railway accidents to have occurred in the past decades and both involved collisions on a single track system. The two events have been analyzed and compared in order to investigate possible learning effects and possible differences in learning given the 25-year span between them. The study is based on the analysis of selected documents related to the accidents in general and the narrative components in the documentation related to learning in particular.Our findings indicate that learning from these events was not expressed as an explicit goal in the aftermath. Learning in these cases seems to be linked for a large part to a change in measures, technical, operational and organizational, but we have not observed any managed confirmation or comprehension processes. The Tretten accident report suggests that the possibility of human error should be mitigated through the implementation of technological barriers, while it omits all other elaborations and risk reducing measures. The Åsta accident report recommended that the work to introduce modern safety management principles that had already been initiated before the accident should be continued. Neither of the accidents yielded any new insights and the knowledge brought forward was merely perceived as confirmation of already-agreed changes.     

Workshop 3A: Governance,contracting, ownership and competition issues in public transport: Looking up not down

Workshop 3A focussed on matters of institutional design that seem likely to improve public transport outcomes. It started by defining high level outcome goals, as measures of ultimate public transport success, and then identified the major societal issues that public transport systems can help to resolve. These issues were separately defined for Southern African and western settings. The importance of taking an integrated approach to transport, particularly land use/transport integration, was seen as fundamental to goal achievement. Workshop papers provided many and varied examples of this importance, ranging from PPPs for major public transport projects to system design issues and contracting out of services. The Workshop included detailed discussion on paratransit development in Southern Africa, where relationship management is proving to be critical, in-line with much previous Thredbo discussion about the important role of trusting partnerships. Parallels and contrasts were drawn with paratransit in western settings. Competition in passenger rail was also a focus, with some questioning of the benefits of franchising. Discussion concluded by proposing recommendations for policy and research and suggesting agenda items for future Thredbo Conferences.     

城市地下空间开发与地下交通系统——重庆市解放碑CBD地下交通系统

城市地下交通系统构建是解决现今城市问题的重要措施之一。该文针对这一课题,探讨了城市地下交通系统的组成及其对改善城市空间的重要作用。结合重庆市解放碑CBD交通现状评价分析与城市发展规划定位等因素,提出解放碑CBD地下交通系统方案——地下车行道路网络、地下快速人行系统。该方案对改善解放碑CBD现状交通和城市环境、提升该区域的经济活力具有重要意义,可作为其它城市发展城市核心区地下道路系统的参考和借鉴。     

一种基于转速反馈的独立轮对的主动导向控制方法

采用左、右轮转速差作为反馈量,对独立轮对的摇头量进行主动导向控制,并研究控制的效果。研究表明:如果仅使用左、右轮转速差作为反馈量,只能使轮对达到纯滚线位置;但在经过补偿速度和轨道曲率的信息后,能使轮对达到线路中心位置。采用转速差反馈主动导向控制后,系统的稳定性会发生变化,反馈增益的稳定区域随着速度增大而减小,补偿速度和轨道曲率信息不会改变控制增益的稳定区域。仿真分析表明这种主动导向控制方法所需要的功率很小。这种方法的反馈量,即左、右轮对转速差可以通过测量车轮的转速而获得,因而这种主动导向控制方法具有显著的实用价值。