Progress in materials technology has led to many innovations, some of which can be applied to railways. In addition to the development of numerous materials and material technologies, advances in analytical and measurement methods have driven higher performance or improved the function of various types of equipment used on railway vehicles and facilities. Additional efforts now have to be made to adapt these new materials and technologies for practical application. This review describes some of recent results from research and development on the latest material technologies in RTRI including work to adapt these results for practical application in railway vehicles and facilities.
Aerodynamic phenomena concerning railway vehicles relate to various issues on railways. The improvement of aerodynamic characteristics of railway vehicles could enhance the value of railway from the view point of safety, convenience, comfort, harmony with the environment, cost reduction, etc. This paper describes the outlines of recent studies on the aerodynamic characteristics of railway vehicles conducted by the Railway Technical Research Institute such as stability against cross wind, air resistance, lateral motion in tunnels and aerodynamic noise.
It is important to reinforce the "robustness" and "restoration capacity" of railways for them to be more resilient not only against expected earthquakes but also against anticipated earthquakes. It is therefore important to respond to the earthquake in four steps in terms of timing: response before the earthquake, emergency response at the time of the earthquake, initial response immediately after the earthquake and restoration/ recovery response after the earthquake. Since railway systems comprise numerous facilities, a range of seismic countermeasures have to be designed covering all components: civil engineering structures, catenary masts, and vehicles etc. Responses both at each stage of the emergency and in relation to each of these components during a seismic emergency should dovetail seamlessly. This report therefore introduces the latest technology that enables the establishment of seamless earthquake countermeasures.
An H+-type geopolymer powder was prepared by grinding a Na+-type geopolymer hardened paste and processing it with sulfuric acid. At pH 7, the extent of cation exchange with Na+ and K+ ions of the H+-type geopolymer powder was one-fourth of that of the original Na+-form geopolymer at the same pH. The ion-exchange capacity of the H+-type geopolymer powder shows pH dependence, that is, has a tendency to increase with higher pH levels. A 10 mass% addition of the H+-type geopolymer reduced both pH and the soluble alkali quantity of the hardened cement pastes to a greater extent than when no addition to the cement paste was made. Further, the injection of cement paste of 40 mass% addition of the H+-type geopolymer suppressed expansion of Alkali-Silica-Reaction more compared to that of the non-addition one.
Running gear maintenance is indispensable for maintaining the safe operation of railway vehicles. The lubricant used on bearings is therefore regularly replaced in axle boxes and traction motors, to maintain performance. Lubricant deterioration depends on the service conditions in which it is used, therefore it was necessary to determine a set of criteria to evaluate its state. A series of criteria were formulated in the 1980's based on the correlation between analysis data and the process of deterioration of lubricating grease as it is used, and have been widely used until today as a guide for replacing grease. This paper therefore revises the criteria in the light of current running conditions.
Under-coat corrosion progresses very rapidly after the repainting of steel railway bridges that have been in use for long periods of time in highly corrosive environments. It is therefore important to use high-quality base conditioning methods. However, these methods can be very costly. Consequently, it is essential to establish not only a method for selecting steel bridges that require high quality repainting, but also to find repainting methods that factor in life-cycle costs (LCC evaluation method). This paper examines a method for selecting steel bridges for LCC evaluation, and then describes an LCC evaluation method that takes into account the cost of surface preparation. Based on a trial calculation of the LCC for models of steel bridges with typically found structures, an appropriate repainting method was proposed.
Aerodynamic and bridge noise originate from pressure fluctuations generated by high-speed trains in open sections without tunnels. In this study, field tests using a linear microphone array were conducted in order to clarify low-frequency aerodynamic sources of noise below 100 Hz. In addition, a scale-model experiment using a launching facility for a model train was carried out to simulate actual aerodynamic noise and investigate low-noise bogie cavity designs. Through these tests, the bogie cavities under the train body were identified as being one of the major sources of aerodynamic noise. It was also found out that rounding cavity edges could be an effective measure to reduce low-frequency aerodynamic noise.
To evaluate the running safety of railway vehicles exposed to strong winds, it is necessary to estimate the aerodynamic forces acting on trains. Numerous wind tunnel tests have already been conducted for this purpose. Meanwhile, computational simulations have been applied to engineering problems using high-performance computers in recent years. This report describes computational fluid dynamic simulations (RANS on unstructured grids and LES on Cartesian grids) that were carried out to reproduce wind tunnel tests. It compares the aerodynamic force coefficients obtained through simulations to those obtained in wind tunnel tests.
Impulsive pressure waves (micro-pressure waves) emitted from tunnel portals are one of the environmental problems affecting high-speed railways. The magnitude of the micro-pressure waves emitted from long ballast track tunnels decreases more than those emitted from long slab track tunnels due to the distortion of compression waves propagating through tunnels. This study investigated the effect of adding ballast to slab-track in tunnels on reducing micro-pressure waves by conducting four series of field measurements and numerical analyses. The results indicate that the addition of ballast to slab-track in tunnels is an effective measure for reducing micro-pressure waves as running speeds are increased on high-speed railways.
This article introduces a statistical relation between earthquake magnitude (M) and a characteristic measured from initial P-wave displacement records, which demonstrates that the final M can be inferred before the peak amplitude arrival (i.e., earthquake rupture completion) in the range of M < 7. Because it is unknown why and how the relation is established, we propose a model for explaining its physical background. We also discuss the application of the relation to earthquake early warning, which can help improve train running safety because M can be determined faster than with the conventional method while an earthquake rupture is underway.
More reasonable seismic design can be achieved by considering the input loss effect of the soil-foundation interaction. However, there is no practical evaluation method of the input loss in the seismic design by means of the static analysis method for the foundation widely used in the railway field. A practical method for evaluating input loss using the static analysis method was therefore examined. First, a sensitivity analysis was conducted by varying both ground and pile conditions, and the input loss effect due to the pile foundations was investigated. Practical methods were then proposed for calculating the effective input coefficient by means of a seismic deformation method and for calculating response spectra based on the random vibration theory. Furthermore, the applicability of these methods was verified through comparison between the dynamic analysis results and the evaluated results.
A static push-over analysis method was used to assess nonlinear behavior of embankments. Then, based on the results of the analysis, a simple method for carrying out nonlinear seismic response analysis of an embankment using an equivalent-single-degree-of-freedom model was proposed. Seismic responses of embankments calculated using the proposed method agreed well with those obtained using the two-dimensional finite element method. This confirmed the validity of the proposed simple method for evaluating seismic behaviors.
The proposed method enables the dynamic responses of embankments to be evaluated easily compared to the conventional two-dimensional finite element method. The method is thus considered an efficient and expedient procedure for evaluating the seismic responses of lengthy railway embankments.