Search

The introduction of special crossings and rail turnouts provides flexibility in the rail network as it allows for vehicles to switch between various tracks, thereby maximizing the utilization of current infrastructure. Turnouts are a costly and critical feature to a rail system as they suffer adverse operational loads, compared with a straight rail track, and thus require regular maintenance. This leads to the question of whether a turnout can be justified for flexibility against upkeep costs throughout the life of the turnout. Therefore, great consideration is given to the interaction between the turnout components and reducing wear in service, as failed components may have adverse effects on the performance of neighboring components. This paper presents a development of three-dimensional (3D) finite-element (FE) model, fostering nonlinearities in materials’ behaviors, to analyze the forces and reactions in a railway turnout system. The analysis provides new findings of critical sections in the turnout and further enables alterations to be made to the initial design of members to accommodate for the increased effects. The FE model is composed of standard concrete sleepers with 60-kg/m rail and a tangential turnout radius of 250 m. The turnout structure is supported by a ballast layer, which is represented by a deformable solid. The FE model is the first in the world to predict the torsional behavior of the turnout and its fragile support by considering multiwheel impacts, which would simulate in-service and cyclic loading and will be adapted as a set of concentrated loads to represent a coupled locomotive negotiating the turnout. The simulations demonstrate the significance of the third medium to suppress the torsional effect of the crossing forces on supporting bearers. [ABSTRACT FROM AUTHOR]

Prestressed concrete sleepers (or railroad ties) are designed to carry and transfer the wheel loads from the rails to the track foundation. Over a period of time, a railway track could experience various types of static and dynamic loading conditions, which are attributable to commercial train operations. Previous studies have established two main limit states for the design consideration of concrete sleepers: ultimate limit states under extreme impact and fatigue limit states under repeated probabilistic impact loads. Prestressed concrete has played a significant role in maintaining the high endurance of the sleepers under low to moderate repeated impact loads. Despite the most common use of the prestressed concrete sleepers in railway tracks, their remaining lives are not deeply appreciated nor taken into account for track maintenance and renewal. The present experimental investigation was aimed at determining the residual prestressing force of railway concrete sleepers after revenue services using the dynamic relaxation technique. Fifteen sleepers were extracted from a heavy-haul rail network for testing using experimental facilities at the University of Wollongong in Australia. The structural evaluation program included quasi-static bending tests, dynamic impact tests, and tests to establish the current level of prestress in the steel wires using the dynamic relaxation technique. Two of the sleepers were evaluated for the level of prestressing forces in accordance with Australian standards. It was found that the level of prestress determined using the dynamic relaxation technique was significantly lower than that expected from the theoretical analysis of time-dependent prestressing losses for the concrete sleepers. [ABSTRACT FROM AUTHOR]

A review of the article “Mitigation of Ground Vibration Generated by High-Speed Trains on Saturated Poroelastic Ground with Under-Sleeper Pads" by Zhigang Cao, Yuanqiang Cai and Jie Han is presented.