We have been conducting research into the derailment and overturning of railway vehicles caused by earthquakes. Up until now, numerical simulation has been shedding light on the dynamic behavior and running safety limits of vehicles on a vibrating track, the results of the simulation now being effectively used in the design of railway structures. To confirm the validity of the simulation analysis, we carried out an experiment using a full-scale half-carbody mounted on a Shinkansen bogie, which was placed on a tri-axial structural vibration test rig. During the test, the carbody, bogie and wheels could be observed jumping from the rails, demonstrating behavior against the vibration. The results of the experiment agreed with those obtained from the simulation analysis.

View full abstract

The running safety of railway vehicles on structures subjected to earthquake motion has been studied using a computer simulation program “DIASTARS” to analyze the dynamic interaction problem between vehicle and structure. In the simulation program, not only the nonlinearity of primary and secondary suspensions of vehicle but also the hysteretic characteristics of structure are taken into consideration. Through the analysis, several running safety boundary diagrams with respect to the frequency of applied sinusoidal motion and the natural period of structure are obtained. The influence of nonlinear behavior of structure on the running safety boundary diagram is also discussed.

View full abstract

The authors discuss methods to predict future earthquake damage and assess actual one to RC structures using numerical simulations and vibration measurement. First, suitability of the Applied Element Method (AEM) is examined as a tool for measuring the seismic performance of RC structures with and without retrofit. AEM can simulate the damage behavior of RC columns, jacketed RC columns and real railway viaducts. Next, a method to improve the accuracy of vibration diagnoses of earthquake-damaged RC structures is discussed using damage assessment criteria calculated by AEM. The changes to natural frequencies caused by damage to RC columns and an actual railway viaduct with steel jacket were also correctly estimated.

View full abstract

Understanding the vehicle/track interaction excited by a vehicle negotiating a sharp curve is of great importance when analyzing vehicle stability and material integrity such as wheel flange and rail gauge corner wear and track component deterioration. The wheel set angle of attack and lateral forces interacting between wheel and rail have been particularly focused on as parameters governing vehicle/track interaction. Contact geometry can be determined easily by worn flange profiles and gauge corners, but the wheel/rail interface such as the coefficient of friction related to lubrication and/or contamination also effects vehicle/track interaction. For this study, some track site measurement was carried out on sharp curves at a Railway Technical Research Institute (RTRI) test track and on operational sections of the West Japan Railway Company to investigate the effect of lubrication on vehicle/track interaction. This paper describes the detailed setup and results of these track site measurements.

View full abstract

A mathematical model that predicts the vibration of wheel/rail systems excited by multiple wheels has been developed. A track is modeled as an Euler beam of infinite length, periodically supported by a system comprised of two springs and a mass. In this system the components represent the following: the two springs, rail pad and ballast stiffness; the mass, a sleeper. A wheel is represented by a single mass. Two sources of vibration are taken into account in the model: the varying stiffness of track between the sleepers and an irregularity on the railhead. On the assumption that any response would be repeated at sleeper intervals, a solution is derived by first equating the value of Fourier coefficients of the wheel locus and that of the rail displacement. The method is applied to the analysis of the vibration of a rail excited by two bogie wheels passing in succession. A sinusoidal irregularity with the wavelength of the sleeper spacing or higher is supposed to exist on the railhead. The results show the basic characteristics of rail vibration such as Doppler shift due to wheel movement, response variations with the irregularity wavelengths and vibration amplitude distribution that is strongly affected by the interference of the two wheels.

View full abstract

In this study, the authors use parametric models to predict the track geometry-induced dynamic motion of a vehicle. The characteristics of vehicle dynamics in these models are directly identified through the spatial as opposed to the frequency domain. One of the former's merits is that we can identify the characteristics of vehicle dynamics with fewer observed signals than when we use spectral analysis, making it easier to obtain signals for identification. Another is that we can determine the parameters to represent dynamic behavior of a vehicle using statistical criteria. With these models, we can predict vertical acceleration of a vehicle and its wheel load as well as estimate track conditions by taking into account both ride comfort and operating safety.

View full abstract

The floating ladder track was developed as a next generation non-ballasted track. Its structural concept is small-mass soft-suspended system so that it can reduce structure-borne noise with a very lightweight construction. A frequency analysis of the measured concrete track-bed vertical vibration proves that the floating ladder track can reduce the vibration by approximately 13 dB compared with that of an adjacent non-ballasted crosstie track. This paper reports on the structural design of ladder sleeper, taking into account the dynamic response against a severe impulsive load due to wheel flat and/or rail-surface defects, and describes the environmental performance of floating ladder track.

View full abstract

This paper discusses the effect of sleeper size on the cyclic deformation properties of railway ballast under cyclic loading. A series of full-scale cyclic loading tests were performed using sleepers of different lengths and heights, from which it is discovered that the sleeper support setup is basically a center support for 2.0m-long and supports at both-ends for 2.6m-long, though the transit pattern in the deflection shape of sleeper has some variation depending on sleeper length and height. In addition, differential settlement tends to increase depending upon the sleeper shape, indicating the center support state under cyclic loading.

View full abstract

For the purposes of an introductory study into performance-based design methods for asphalt concrete-reinforced roadbeds, the deformation characteristics of roadbeds were investigated by means of scale model tests. A fixed-point loading test applying repeated loads to the same point of a rail, which is the conventional loading test method, has an inevitable problem in that the settlement of the sleeper just beneath the loading point becomes greater than that of adjacent sleepers. To avoid this problem, a moving-wheel loading method was adopted for this study. This paper discusses the differences between the deformation characteristics of reinforced roadbeds under fixed-point and moving-wheel loads.

View full abstract

An Aeolian tone suppression mechanism of a perforated pantograph horn has been experimentally studied with an anechoic wind tunnel. Three types of horn models — a simple cylinder, a cylinder perforated with periodic holes and one with a continuous slit — were used to compare aerodynamic noise characteristics and the flow field around them. Experimental results showed that the wake shear layers of the perforated cylinder become stable due to the jets emitted from the holes at regular intervals, thus providing the optimal way of suppressing the Aeolian tone. In the case of the cylinder with a continuous slit, the Aeolian tone was also suppressed, but the interaction between the continuous jet and the shear layer caused another narrow-band noise.

View full abstract