Detection of local instabilities based on typical wheel-rail-forces (EPIB 2)

有碴轨道上部结构与上部结构和下部结构/地基提供的实际刚度特性相对应，达到了所要求的荷载分布和动载减振效果。然而，这些特性在轨道上并不是恒定的，例如由于底座结构性能的变化，而且由于道碴提供的枕木的单独支撑条件，也是从一个钢轨支撑到另一个钢轨支撑。沿加载轨道的几何偏差定义了初始质量以及轨道上的动态轮轨力来源。由于道床内部或下部结构/地基内的塑性变形，轨道几何形状和上部结构刚度面临着依赖于荷载周期和依赖于时间(气候影响)的变化。在具有单一局部缺陷的轨道路段上，由于车辆-轨道的高度局部反应效应，轨道质量将日益恶化，因此早期需要进行轨道维护。为了实现联合项目的目标，子项目EPIB 2将利用基于校准的车辆-轨道-基础结构相互作用模型的模拟来研究和确定基础结构/地基内的局部不稳定性对轮轨力的影响。对于模型校准，需要现场调查，这已经被DB Netz AG和ÖBB INFRA接受。该模型将覆盖一定长度的轨道，因为动态轮轨力取决于所加载轨道的几何形状，并与刚度特性和基于车辆的参数(惯性、弹簧和阻尼器特性、速度)相互作用。其目的是实现模型的高度灵活性和对不同有碴轨道系统的适用性。作为联合项目的一部分，EPIB 2工作包的主要目标是使在轨道几何形状发生重大偏差之前很长时间内尽可能简单和尽早地检测到局部不稳定。由于轨道下部结构中粘性土的局部薄弱，局部失稳会导致塑性变形增加。局部缺陷可以通过轮轨力的变化来检测，轮轨力的变化也叠加了由实际的、一般的轨道质量产生的动态力。轮轨力的典型动态激励(根据频率和幅值)是存在局部不稳定的指标，可以从测量列车或常规列车的垂直轮力或轴箱加速度的连续读数中提取，并可实施到轨道管理系统中。这也将加强探地雷达测量在确定轨道沿线刚度特性方面的结果。

The ballasted track superstructure achieves the required load distribution and the damping of dynamic traffic loads in correspondence with its actual stiffness properties provided by superstructure and substructure/subsoil. However, these properties are not constant along the track, e.g. caused by changes of substructure performance but also from one rail support to the next because of individual support conditions of the sleepers provided by the ballast. Deviations of geometry along the loaded track define the initial quality as well as the track borne source of dynamic wheel rail forces. Because of plastic deformations within the ballast layer or within substructure/subsoil the track geometry and the superstructure stiffness are facing load cycle dependent and time dependent (climatic impacts) changes. Along a track section with single, local defects, an increasing degradation of track quality and therefore early need for track maintenance will be observed, because of the high local vehicle-track reactive effects. To achieve the goal of the joint project, the subproject EPIB 2 will study and determine the effect of local instabilities within substructure/subsoil to wheel rail forces using simulations based on a calibrated vehicle-track-substructure interaction model. For model calibration in-situ investigations are needed, which are already accepted by DB Netz AG and ÖBB INFRA. The model will cover a certain length of the track, because the dynamic wheel rail forces are dependent on the geometry of the loaded track and are in interaction with stiffness properties and vehicle based parameters (Inertia, properties of springs and dampers, speed). The intension is to achieve a high flexibility of the model and applicability to different ballasted track systems. Main goal of work package EPIB 2, as part of the joint project, is to make the detection of local instabilities as simple and as early as possible, long time before significant deviations of track geometry occur. Local instabilities will cause increasing plastic deformations because of local weaknesses of cohesive soils within rail substructures. Local weakness can be detected by changes in wheel rail forces, which are also superimposed by dynamic forces generated by the actual, general track quality. Typical dynamic excitations (according to frequencies and amplitudes) of wheel rail forces, which are indicators for the presence of local instabilities, can be extracted from continuous readings of vertical wheel forces or axle box accelerations of measurement trains or regular trains and may be implemented into the track management system. This would also strengthen the results of ground penetrating radar measurements with respect to the determination of stiffness properties along the track.