To improve the performance and riding comfort of tilt-controlled vehicles, we developed a next-generation tilt control system that uses a position detecting system, a novel tilt pattern, high performance tilt actuators and other new technical elements. Under this system, the running train position is detected by curvature collation based on GPS signals and the tilting angle target pattern calculated to optimize the riding comfort evaluation index. The pattern thus created is called the JT pattern, according to which the tilt actuators are electro-hydraulically powered. Running tests have proved that low-frequency vibration causes train motion sickness has decreased as a result of this system.

抄録全体を表示

The goal of this study is to reduce the bending vibration of railway vehicles by applying a vibration suppression technique that utilizes piezoelectric elements electrically shunted by an external circuit. This paper presents an investigation that uses a scale model of a Shinkansen vehicle about 5m long. Small pieces of piezoelectric elements are bonded to its floor structure and electrically connected to a shunt circuit featuring a design based on a newly proposed method. The results of excitation tests show that the bending vibration of the carbody can be reduced successfully.

抄録全体を表示

Boundary element analysis has been performed on the cycle of stress intensity factors at a surface initiated rolling contact fatigue crack tip under a Hertzian contact pressure distribution. The model includes the effects of Coulomb friction between the faces of the crack and the possible effect of fluid penetrating into the crack. Three possible models to show the influence of fluid on crack propagation have been investigated, namely, (a) a fluid lubrication model; (b) a hydraulic pressure model; and (c) a fluid entrapment model. The analysis results indicate that when the fluid entrapment model was used, the values of generated mode I and II stress intensities were reasonable and the results were consistent with the behavior of the crack. Therefore, the fluid entrapment model is considered to be the most promising for explaining the behavior of the rolling contact fatigue cracks.

抄録全体を表示

Base isolation design has been adopted for a large number of bridges to prevent devastating structural damages due to severe earthquakes. In applying such a design to railway structures, however, the dynamic behavior of the track structure that significantly affects the bridge response should be investigated.
In this study, the behavior of the track structure under an earthquake was clarified and modeled through shake table tests. Numerical analyses were then conducted for a real bridge to evaluate the effect of the track structure. It is shown that supplemental damping introduced by the track structure is not negligible and can reduce the responses of piers and bearings simultaneously.

抄録全体を表示

The Impact Vibration Test is now a recognized method for evaluating the soundness of bridge substructures. This method focuses on the natural frequency of the pier under test, since it clearly shows the condition of the bearing capacity of the foundation and the soundness of the pier. The measured and standard values of the pier's natural frequency are compared for evaluation, and it is judged to be "sound" when the former is sufficiently higher than the latter, and as unsound otherwise. The standard value of the natural frequency is calculated by statistical analysis using several parameters, such as the pier height, pier width and the weight of the superstructure, although these parameters are highly correlated with the natural frequency. But the conventional standard value calculation formula does not have physical significance at all. Entirely based on a design concept for foundations, this paper introduces a new and progressive method for the standard value of the natural frequency of wooden pile foundations.

抄録全体を表示

Jointed rails are replaced periodically in Japan. Their service life is governed mainly by the fracture at the joints. To evaluate the fatigue life of jointed rails, it is necessary to verify the stress distribution around fish-bolt holes and an S-N curve of jointed rails. Therefore, we carried out static loading tests in a laboratory and field tests to measure the stresses around the fish-bolt holes, and further dynamic stress analysis of jointed rails and bending fatigue tests of rails used in the field.
The dynamic stress analysis model is composed of a beam model to calculate dynamic wheel/rail contact forces and a solid model to calculate stress distribution resulting from those contact forces. These models were validated using field test data. Based on the study results, we established a method to evaluate the fatigue life of jointed rails. In this method, we calculated the stresses under several combined conditions of jointed rail, vehicle type and vehicle speeds.
The fatigue life was calculated by applying the stresses to the S-N curve. As a result, the rail replacement period have a potential to be extended except in cases of heavy wear between a fishplate and rail.

抄録全体を表示

In order to clarify the strength and deformation properties of ballast during the abrasion process, a series of abraded ballast particle shape evaluations, as well as large triaxial compression and cyclic loading tests with a large-scale track model using abraded ballast particles were performed. Based on the test results, this paper investigates the degree of abrasion of ballast particles, their shape properties, their strength and deformation properties and settlement characteristics under cyclic train loads. It was found that the shape evaluation method using a normalized argument function is an effective method to evaluate the abraded state of ballast particles.

抄録全体を表示

We built two degradation models to estimate alignment irregularity growth on ballasted track. One was a model to evaluate plans, such as track structure improvements or changes to transportation conditions, and the other was to decide on a daily/monthly track maintenance schedule. To confirm the efficiency of each model, we compared the actual and estimated irregularity growth data with a statistical modeling approach. Moreover, we applied the models to the analysis of railway track renewal and optimal tamping scheduling.

抄録全体を表示