A great earthquake of magnitude M9.0, occurred around 14:46 pm on March 11, 2011, at an epicenter at an undersea depth of 24 km off the Sanriku coast line, an area in the northeastern part of the main island of Japan. The earthquake was named as "2011 off the Pacific Coast of Tohoku Earthquake." A large-scale fault slide occurred at the plate boundary stretching from the offshore area of Iwate to Ibaraki, and caused heavy tremors of level 7 Japanese Seismic Intensity at Kurihara City in Miyagi Prefecture, and of level 6+ in wider areas in Miyagi, Fukushima, Ibaraki and Tochigi prefectures. This article outlines the outline of the earthquake, and gives an overview of RTRI activities to support the recovery of railway networks damaged by the earthquake. The comparisons of the actual shaking waves of this earthquake with design waves in the Design Standards for Railway Structures: Volume of Seismic Design is also described.

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In Japan, the frequency of the concentrated downpour has increased lately, and further there occur large earthquakes frequently. Quite recently, a massive earthquake occurred on 11th March, off the Pacific coast of the Tohoku area, causing devastating damages. On account of such natural disasters, damage scale along railways has become large and its damage modes have been diversifying at the same time. Therefore, at first, this paper explains about circumstances of climate change, and introduces features of natural disasters corresponding to such changes. Moreover, this paper shows the recent state and the future prospects of the research and development in the Japanese disaster prevention technological field.

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The earthquake early warning system was put into operation in Japan in order to stop Shinkansen trains as rapidly as possible before the strike of large tremors, in the case of an earthquake. The present paper overviews current earthquake early warning system configuration and functions and evaluates the accuracy of epicenter estimation by that same system by using the latest datasets. The estimation error (rms) of epicentral distance in the present system is 0.324 on a logarithmic scale. By re-determination of the coefficients of correlation equation for estimation, it was confirmed that the estimation error was reduced by 13%.

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In this study, the authors performed model tests and numerical analyses to clarify the quantitative effect of seismic countermeasures for existing mountain tunnels in poor geological conditions. It has become apparent that inner reinforcement can control the initiation of cracks and prevent spalling; backfill grouting can improve deformation performance of the tunnel and control compressive failure in arch crowns; and rock bolts can control heaving of the roadbed. Even though there are many restrictions associated with construction of inverts, it has become apparent that inverts are a fundamental countermeasure to control tunnel deformation and heaving of the roadbed.

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The study presented in this paper verifies the seismic retrofitting effects of reinforcing over-track buildings with knee-brace dampers. Firstly shaking table tests were carried out on large-scale test models, to simulate over-track buildings reinforced with knee-brace dampers. Resulting responses or hysteresis loops, confirmed the seismic retrofitting effects of knee-brace dampers. In addition, natural frequencies and damping factors of the models were estimated by ARX model. Furthermore, analytical study of over-track building models simulating true structures confirmed the seismic retrofitting effects of knee-brace dampers.

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The use of low-grade material sheath grouting for PC girders has resulted in some PC girders initially constructed in the 1950s having insufficiently filled sheaths. The exposure of PC tendons in the sheath generates corrosion and rupture of the PC tendons, reducing the load-bearing capacity of PC girders. This research focused on the interface bond between PC tendons and grout in the sheath through loading tests in order to explain the loading capacity of deteriorated PC girders.

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One of the most important issues in Shinkansen high-speed operation is current collection performance. The installation accuracy of overhead contact lines has a considerable influence on the contact force fluctuation between overhead contact lines and the pantograph. However, there are no concrete installation guidelines for putting into place overhead contact lines specifying the acceptable range of installation errors. This paper proposes a procedure for establishing installation guidelines, which are derived from the results of dynamic simulation based on the state of actual installations. Construction guidelines compiled in accordance with the above mentioned approach are therefore set out herein for Shinkansen operations at 300 or 320 km/h. Installation error indices and guideline ranges are also introduced. It is hoped that the installation guidelines will contribute to an improvement in performance, reliability, safety and maintenance efficiency of overhead contact lines.

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Certain factors such as arcing between the contact wire and pantograph contact strip cause contact strips wear. Once local wear occurs, step-shaped wear patterns are highly likely developed. A contact strip with this step-shaped wear may lead to accidents such as contact wire breakage. To prevent such accidents, the authors have developed a method for detecting step-shaped wear on contact strips by measuring the vibration of the contact wire. This paper describes this new method and some results of experimental testing.

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Correct analysis of feeding circuits requires correct line constants of overhead lines and rails. Consideration of the frequency response of self-impedances and mutual impedances on steady state analysis is necessary because they affect calculation results. However, there are only a few reports on transient analysis of feeding circuits which take frequency response into account. This paper suggests a transient analysis model of overhead lines and rails with approximated frequency response, and shows the results of transient analysis on a simplified DC feeding circuit.

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