The adverse effects of earthquake-related structural vibration displacement on the running safety of railway vehicles makes it essential to establish a sound method of assessing these effects while designing railway structures seismically. This paper examines the seismic behavior of running railway vehicles, and proposes a code-type provision for the Running Safety Assessment (RSA) of vehicles based on the results of comparing the assessment indices of Spectral Intensity (SI) and Peak Velocity (PV). Moreover, to enable simple assessment of the running safety of a common seismic design, a nomogram based on the SI assessment index without the use of any calculation has been prepared.

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Since mountain tunnels are generally surrounded by stable ground, their displacement during seismic activity tends to be minimized, making such structures less susceptible to seismic damage. Despite this, many railway mountain tunnels have sustained damage, from the 1923 Kanto Earthquake to the 2004 Niigataken-Chuetsu Earthquake. This paper provides an outline of the historical damage to mountain tunnels in Japan and outlines the results of case studies on damage sustained in mountain tunnels. Also outlined here is a classification of the damage patterns and the conditions of damage based on the results of the case studies, and we refer to the estimated causes of damage to tunnels in the 2004 Niigataken-Chuetsu-Earthquake.

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In severely cold regions of Japan, a conventional countermeasure against frost heaving is to replace the silt and loam layers with a non-frost material. The depth for replacement is determined by the frost penetration depth obtained from one-dimensional analysis using only the freezing index based on the annual average air temperature. This means that the thermal characteristics of the materials comprising the railway track-bed are not taken into consideration. This paper examines the applicability of advanced Berggren's method as a new technique to determine the freezing penetration depth. This method makes it possible to take into account the thermal characteristics of multilayer materials. We also introduce experiments for the determination of thermal characteristics.

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We studied a method of quantitatively evaluating safety levels by train operational control in gale conditions. For the purpose of the evaluation, we estimated the functions of distribution of wind velocity occurrence and wind temporal fluctuations. Using these functions, we calculated the probability of a gale occurring in a given section during train operation. The authors compared the calculated probability with the relative frequency observed at the site. A model section for wind velocity observation was assumed, and several different train operation methods were compared with the safety level evaluation of each method in the section by calculating the probability.

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Bridge pier foundations occasionally become unstable due to scouring around piers in flood conditions, and operational restrictions imposed according to the water level are practical for maintaining safe train operation. However, when such restrictions are lifted, it is quite difficult to verify the condition of the bridge pier foundation. It is therefore necessary to develop a practical method of quantitatively evaluating and assessing the structural integrity of bridge pier foundations in flood conditions. This paper reports the results of analysis of long-term microtremor measurements made on existing bridge piers and a method to define the natural frequencies of bridges using microtremors.

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In this report, we propose an analytic model for masonry walls, the validity of which was then verified by applying the model to a simplified deformation analysis method obtained from the results of shaking table tests with models. Furthermore, we discuss the method's applicability to quakeproof reinforcement works. The analytical results corresponded well to the results obtained from experiments; therefore this method can be reliably applied to the design of quakeproof masonry. We will continue an in-depth study to enable this method to be applied to the quakeproof design of real masonry walls.

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In this paper the author proposes a hypothesis to explain a wavelength-fixing mechanism for rail corrugation. Corrugation growth was predicted using a theoretical model that took into account multiple-wheel interaction and the Doppler effect of rail vibration caused by wheel movement. The wheel-rail contact forces due to virtual sinusoidal irregularities on the rail head were calculated, and the corrugation growth at an arbitrary wavelength was predicted. To verify the hypothesis, the author conducted a precise investigation into the corrugation wavelengths on various track sections using vertical acceleration of the axle box. Even on a specific section of track, large-amplitude corrugation was not generally found at a specific wavelength but rather in a few wide-band ranges. Moreover, in each range where significant corrugation occurred, several sharp peaks were observed at constant frequency intervals. These peaks were found to appear at regular intervals approximately equal to fractions of a wheelbase length, and the theoretical prediction showed good agreement with measured corrugation characteristics. It was concluded that various kinds of corrugation are the result of rail vibration interference excited by multiple wheels.

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The contact force of pantograph is one of the most important indexes in evaluating current-collection performance. Quality of contact wires maintenance will be more improved by use of observed contact force. However, specific methods for applying the contact force have yet to be proposed. This paper discusses possibility of estimation of wear and strain of contact wire using the contact force data. For this purpose, the learning capability of an artificial neural network is used. A complex number version of a backpropagation algorithm is used for a learning weight. As the result of this study, the author verified that estimation of the wear and the strain of contact wire using the contact force is valid.

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Track transitions such as slab track to ballasted track, level crossings and bridge abutments are common locations of accelerated track geometry degradation (differential settlement). In this paper, we study the mechanism of wheel load variation caused by changes in track stiffness and loose sleepers using a track dynamic model based on the results of measurement. We then evaluate countermeasures such as larger sleepers, resilient sleepers and a track-lifting technique.

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Due to their higher bridge piers and massive girder loads, long span bridges over rivers tend to have a longer natural period of equivalence. Therefore, during seismicity, train-running quality is impaired on the foregoing bridges. In this study, the authors analyzed numerically dynamic behavior of the train-running quality on a long span bridge, and clarified the following items: Firstly, the train-running quality on the bridge becomes lower on girders in the middle of the bridge. Secondly, folding displacement at edges of the bridge did not largely affect the train-running quality. In addition, the authors studied on improvement measures by taking rigidity of piers and bearing as a parameter, and clarified that the train-running quality be improved with provisions of a large-size caisson or a sliding bearing.

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