Resilient rail infrastructure: dissipation driven fracture analysis of concrete support systems

英国的铁路基础设施目前每年要运送13亿人次的旅客和1亿吨的货物。仅货运一项就为英国经济贡献了8.7亿英镑。在过去的10年里，该行业的客运量和货运量分别增长了40%和60%，预计在未来30年里，客运量将翻一番，货运量将增长140%。随着网络的发展，施加在轨道支撑系统上的载荷的幅度和频率显着增加，甚至在过去的10年里。据估计，在2009年至2014年之间，英国铁路运营商网络铁路（NR）将投资37.5亿英镑来维持铁路网络。这32,000公里铁路基础设施中的绝大部分由预应力混凝土枕木（pcs）和过桥架（CBs）支撑。这些混凝土构件为运行的钢轨提供横向约束和垂直支撑。PCSs和cb依次由轨道镇流器三面支撑；碎石直径30-50mm。自20世纪50年代推出以来，压路机已经在新轨道上取代了传统的木制枕木，印度铁路公司每年用压路机取代大约20万个木制枕木。然而，尽管英国的铁路网依赖于这些混凝土结构，而且它们的几何形状很简单，但令人惊讶的是，人们对它们的结构行为知之甚少。NR的CP5交付计划估计，2013/14年期间支持该网络的枕木的使用寿命为60.9%，在同一时间段内将发生5,918次轨道故障。有人担心，混凝土支撑构件裂缝的发展正在破坏铁路网。为了维持一个安全、可靠和有弹性的铁路网络，必须了解如何设计混凝土支撑系统，以适应未来不断增长的结构需求。提出的研究涉及三维动力分析，以评估预应力混凝土和混凝土混凝土的结构鲁棒性，使用新的计算力学框架和相关的数值分析技术。如果成功，这项研究将为各种工程材料的断裂建模提供一个变革性的、完整的和一致的框架。该方案的创新之处在于将本构建模、断裂力学和数值分析技术的最新理念应用于英国铁路基础设施的一个鲜为人知但却至关重要的组成部分。它将为开发新的弹性轨道支撑系统紧固方法提供一个框架。

The UK's rail infrastructure currently supports 1.3 billion passenger journeys and 100 million tonnes of freight each year. The freight transport alone contributes £870 million to the UK economy. The sector has seen 40% and 60% increases in passengers and freight over the last 10 years, respectively, and it is expected that passenger numbers will double and freight increase by 140% over the next 30 years. As the network has developed the magnitude and frequency of loads applied to the rail support systems have increased significantly, even over the last 10 years. It is estimated that between 2009 and 2014, the UK's rail operator, Network Rail (NR), will invest £3.75bn in track to maintain the network. The vast majority of this 32,000km of rail infrastructure is supported by pre-stressed concrete sleepers (PCSs) and crossing bearers (CBs). These concrete members provide lateral restraint and vertical support to the running steel rails. The PCSs and CBs are in turn supported on three sides by track ballast; crushed stone 30-50mm in diameter. Since their introduction in the 1950s, PCSs have superseded traditional wooden sleepers in new track and NR replaces approximately 200,000 timber sleepers each year with PCSs. However, despite the reliance of the UK's rail network on these concrete structures, and the simplicity of their geometry, surprisingly their structural behaviour is poorly understood. NR's CP5 delivery plan estimated that the used life of the sleepers supporting the network for the 2013/14 period is 60.9% and that 5,918 track failures would occur during the same timeframe. There are concerns that the development of fractures in concrete supporting members is undermining the rail network. In order to maintain a safe, reliable and resilient rail network it is essential to understand how the concrete support systems can be designed to future proof them against ever increasing structural demands.The proposed research is concerned with three-dimensional dynamic analysis to assess the structural robustness of PCSs and CBs using a novel computational mechanics framework and associated numerical analysis technique. If successful, this research will provide a transformative, complete and consistent framework for modelling fracture in a variety of engineering materials. The creativity of this proposal lies in the application of up-to-the-minute ideas in constitutive modelling, fracture mechanics and numerical analysis techniques to a poorly understood yet critical component of the UK's rail infrastructure. It will provide a framework within which to develop new resilient rail-support system fastening methods.