At present, in case of earthquakes with tremors exceeding the operational control threshold, walking patrols must inspect seismographs for each relevant track section, to ensure safety. In order to resume train operations more rapidly after restrictions have been imposed on train operations due to an earthquake, a working model system was developed which can accurately estimate seismic motion just after the earthquake. This system makes facilitates decision making for earlier resumption of traffic following the earthquake. By obtaining seismic information not only from railway operator's seismographs but also from public data sources in quasi-real-time, this system estimates the distribution of the shake over meshed planes and extracts the seismic motion at any given chainage point along the target railway section being evaluated.

抄録全体を表示

Many aftershocks followed the 2011 off the Pacific coast of Tohoku earthquake after the main shock. There is a need to assess the seismic stability of railway facilities against large earthquakes in consideration of aftershocks. To this end prediction of aftershocks is necessary. This paper proposes a prediction method, which can calculate the magnitude and time lapses between aftershocks after a main shock, based on statistical processing on past earthquakes including aftershocks. Using the proposed method, preliminary calculations were conducted to obtain the time history for a main shock of magnitude 7.0, and its aftershocks. The effect of the aftershock on the damage to the structures was investigated using these waveform groups.

抄録全体を表示

In recent years, railways have suffered frequent damage from landslides due to natural slopes adjoining tracks. Checking the stability of all trackside slopes however would be immensely time consuming and expensive. Developing a practicable and viable method to manage such natural slopes is therefore important. This paper quantified the factors relating to landslides such as geomorphologic features and vegetation, using a digital elevation model and a digital surface model. These evaluation factors were then applied to identify potential landslide locations.

抄録全体を表示

An obstruction-warning signal is an important piece of signalling equipment used at level crossings in Japan. However, it is not possible to check the visibility of such equipment during train operating hours, because this would require service disruption. This paper therefore proposes a method which employs near infrared LEDs, and can check the visibility of obstruction-warning signals during in-service hours. It has been proved that the developed image processing method, using a near infrared camera and a pan-tilt camera by feedback control installed on a vehicle, can correctly detect specific signal blinking. The paper then gives results from functional field tests.

抄録全体を表示

A high level of safety is required for train control systems. It is important to apply all required safety measures to train control systems without any omissions. As many more functions are required in recent train control systems than before, it is necessary to divide the design phase into the conceptual design phase and the detailed design phase, in order to avoid system design complexity. In this paper, in order to conduct this appropriately, the template of safety requirements and a method of verifying the specifications of the system requirements with this template are proposed. The procedures are illustrated by applying the proposed method to CARAT (Computer And Radio Aided Train control system) as an example. Moreover, to apply this method efficiently, a support tool was built to verify safety requirements, and which displays safety verification items to be checked in the system requirement specifications automatically.

抄録全体を表示

High speed data transmission systems using metallic telecommunication lines such as xDSL (Digital Subscriber Line) are being introduced into railway systems as a substitute to analog systems where adoption of optical carrier is not cost effective and to supplement optical carrier systems between a station with optical terminal equipment, and a station without optical terminal equipment. Research carried out so far has produced a method for assessing the suitability of coupling high speed data transmission systems for railways with normal-state telecommunication lines. This study proposes an improved evaluation method, which considers the influence of the line disturbances on the electrical characteristics of telecommunication lines, and delay time and jitter when transmission systems are connected in tandem.

抄録全体を表示

Research has been carried out on the safety of ballasted track with a view to minimizing damage during earthquakes. There remains however a lack of insight into the dynamic behavior of ballasted track itself during earthquakes. Consequently the authors of this paper first carried out static analyses to evaluate stability of straight track resistance to buckling when using continuous welded rails. Secondly the authors carried out dynamic analyses of ballasted track behavior laid directly on the ground or on a structure, under earthquake conditions, based on parameters such as lateral peak resistance of ballast and scale of earthquake, inter alia.

抄録全体を表示

The dynamic motion of a train set will be affected by the change in running resistance as the wheels run over sleepers or ballast. It is therefore important to determine the motion of vehicles in such situations both experimentally and theoretically. A 1 to 10 scale model vehicle was used to perform running tests during which the vehicle was made to collide against model iron sleepers. Further running tests were carried out involving a real single bogie falling onto ballast or a concrete sleeper. These experiments were used as a basis to develop a numerical simulation program, capable of calculating the dynamic motion of a train after its derailment, and computed dynamic behavior of 5 cars after their derailment.

抄録全体を表示

This paper proposes a newly developed method, which measures absolute axial stress of continuous welded rails (CWR), based on the change of resonant frequency of standing wave mode of rails in the periodic infinite railway track structure. First, the authors theoretically derived dominant simultaneous equations regarding the vibration motions of a three-dimensional Timoshenko-beam under compressive or tensional axial-loadings. By applying the Floquet's theorem to dominant equations of the unit cell, which is an irreducible sub-structure with periodicity of the infinite track structure, the equations are simplified into Eigen-value problems in the frequency domain. Numerical dispersion analyses of wave modes propagating in a track made clear the relation among axial-loadings, wavenumber and natural frequency and provided an evaluation of the feasibility of the proposed method for the measurement of the absolute axial stress. Furthermore, in-situ measurements in the existing CWR track experimentally confirmed the linearity between the axial stress and the resonant frequency.

抄録全体を表示