RTRI is conducting R & D with the aim of improving railway safety, reducing maintenance costs, and improving rail services by introducing higher running speeds. Approximately half of all R & D for vehicles is concentrated on safety, mainly focusing on research on running safety evaluation methods such as flange climb derailment and crashworthiness evaluation. To improve the quality of railway services for passengers, other research and development aims to improve ride comfort by reducing vibration, developing tilting technology and noise reduction. This paper gives an overview of current research and development being conducted in the Vehicle Structure Technology Division, the status of crashworthiness evaluation, and of work to improve ride comfort.
Huge earthquakes and localized heavy rain, which occur frequently in recent years in Japan, have damaged many types of social infrastructure, including railway structures. Damage to railway structures has in the past lead to disruption or suspension of train operations, sometimes up to several years, or relatively shorter periods, depending on the seriousness of the damage. This report addresses issues that arose from the 2011 off the Pacific Coast of Tohoku Earthquake and the 2016 Kumamoto Earthquakes, and the heavy rain which fell in northern Kyushu in July 2012 and the 2016 heavy rains due to Typhoons 7, 9, 10 and 11. The report summarizes the findings obtained from damage to railway structures caused by past earthquakes and rains. In addition, it details railway structure countermeasures for disasters on which Railway Technical Research Institute(RTRI) has been working and examples of recovery technically supported by RTRI. Finally, it describes future work on disaster prevention and mitigation technology and early recovery technology.
RTRI's new Master plan began this year in 2020. In this plan, one of the directions set for research and development is how to use ICT to save labor in track maintenance. This report describes research results from the field of track technology achieved during the previous five-year master plan, and introduces RTRI's research policy for the new Master plan. Research results include, for example, an integrated data management system for railway infrastructure, the development of a system to support track monitoring from onboard trains, and a method for detecting loose sleeper on ballasted track. In future, we aim to use digital technology to facilitate track inspections and improve prediction methods.
There is growing demand for high energy efficiency railway vehicles which do not emit CO2 and NOx. To meet this demand, we have been developing railway vehicles powered by a hybrid configuration of fuel cells (FC) and batteries (Bat). In the previous development stage, we installed FC and power converters in passenger areas on the train, because of their size. In addition, acceleration of the vehicle was limited to that of a conventional DMU. For this paper, using passenger areas was not necessary, because downsized FC and power converters were installed under the vehicle floor. Furthermore, we improved tractive performance to reach that of a standard EMU, by increasing the power capacity of each FC and Bat.
Reducing elastic vibration of railway vehicle carbodies is required to improve ride comfort. A high-accuracy numerical analysis model is required to study effective vibration reduction methods. This paper describes a new numerical analysis model, and a method for determining parameters for the proposed model by using particle swarm optimization. After the application of the proposed method to a Shinkansen-type test vehicle, the authors created an analytical model with a maximum natural frequency difference between measured and calculated results of the targeted six elastic vibration modes within 0.86%, which indicates the effectiveness of the proposed model and parameter determination method.
Variation in driving or braking force can cause longitudinal vibrations of the vehicle, which sometimes causes a fall in adhesion and further slipping and skidding. As such, it is essential to elucidate the relationship between tractive force and longitudinal vibration in consideration of electric and mechanical systems. Understanding this relationship can facilitate improvement of motor control methods. This paper reports on investigations into longitudinal acceleration produced by variation in tractive force, and on results of a comparison between test results using an actual train set and results obtained from numerical simulation.
Fatigue cracks initiate in the lower flange of rivet girder supports because of the stress caused by bridge member deterioration. There are cases where fatigue cracks cannot be immediately repaired because the procedure would be time consuming and costly. This research identifies some of the causes of the stress in the lower flange of rivet girder supports, having conducted loading tests on a rivet girder, and FEM analyses. On the basis these results, we began developing reinforcement methods for inhibiting fatigue crack growth in the lower flanges of rivet girder supports. Moreover, we are verifying the effect of these reinforcement methods through loading tests.
In stations built beneath low viaducts, the void between the bottom of the viaduct and the suspended ceiling over the station is small, therefore it is difficult to install the usual anti-seismic braces used for reinforcement. In addition, the anti-vibration rubber that is conventionally used for noise abatement, weakens the anti-seismic reinforcement performance of this type of structure. As such, we developed a less costly, more practical seismic reinforcement method, where the ceiling cavity is not obstructed. Structural cyclic loading tests were carried out to evaluate the anti-seismic performance of this method. This method demonstrated strong anti-seismic performance. In addition, acoustic tests were conducted with the new construction method. Results demonstrated the noise reduction effect with the new and the conventional method was the same.
Earth retaining structures, such as bridge abutments and retaining walls, are constructed at the boundary of bridges or embankments. There are a variety of earth retaining structure failure modes, therefore in order to be able to ensure rational aseismic reinforcement, it is necessary to develop a range of different aseismic reinforcement methods adapted to the relevant earth retaining structure's failure mode. Moreover, there are many cases where construction work is severely restricted due to various limitations, such as land boundaries, available space, and time available for construction work. Therefore, the authors propose an aseismic reinforcement method, which can both improve seismic performance of earth retaining structures and be carried out efficiently. This paper outlines this research and describes some examples of the practical application of the newly developed reinforcement method.
Rail corrugation is a phenomenon where roughness patterns of regular wavelengths are formed on the rail running surface by passing vehicles. In order to elucidate the mechanisms underlying corrugation, rail roughness growth mechanisms and evolution process were analyzed using theoretical and numerical methods. The resulting characteristics obtained in this manner were verified on the basis of rail roughness measured on domestic commercial lines. These results confirmed that corrugation growth factors consist of four anti-resonance phenomena, and that there are three stages in the corrugation evolution process: formation, growth and saturation. Finally, this paper proposes possible approaches for developing countermeasures.
Track temperature and axial force can vary because of the influence of shadow cast by geographical features near railway lines. However, exactly how these variations affect track buckling has not yet been clarified. In this paper, the rail temperature distribution of the track is calculated in consideration of shadows cast by geographical features using a rail temperature prediction model. Results from these investigations confirmed that this method of analysis could reproduce drops in rail temperature of between 10°C and 15°C, which corresponds to the rail temperature difference actually observed in shaded and sunny areas.
To estimate the service life of rails, it is necessary to clarify the relationship between the stress and the number of loading cycles needed to reach breaking point through bending fatigue tests. In the previous studies, bending fatigue tests were conducted under high stress levels exceeding the stress generated on real tracks. In this study, bending fatigue tests were carried out under lower stress level conditions, and the service life of rails was estimated reflecting the results obtained in high cycle regions. Based on the results of these tests, this paper suggests it may be possible to extend the period between rail replacements.