Although we have been pointing out the danger of ceiling collapse since the “South Hyogo Prefecture Earthquake” in 1995, a lot of ceiling collapse occurred in large enclosures during the “2016 Kumamoto Earthquake”, which consecutively measured a maximum of 7 on the JMA seismic intensity scale. We investigated two large enclosures: a cultural facility which has a public hall with a heavy ceiling ensuring the acoustic performance and a public indoor athletic facility which has an important role of an evacuation center. In this report, the investigation results of them are described.
The ceiling fall occurs one after another, so we must take measures against it. Fall prevention nets are effective measures as a fail-safe, but there are some problems, such as the difficulty of calculation about impact force and how to lighten the load of cables. In this review, we suggest that the shock absorbers which are attached to the ends of cables and lighten the axial force of them are introduced into fall prevention nets for ceilings. We also show the result of numerical analysis of cable nets with shock absorbers in order to reveal the effect of them.
To clarify the damage to the 2016 Kumamoto earthquake on the traditional timber houses, the damage investigations were performed. The Mashiki town and its nearby area were hit the most serious damages. In the Mashiki town, main failure modes of timber houses were totally collapse and collapse at the first floor. In the Kumamoto city, there are many of collapse house and large deformation at the first floor. On the two damaged traditional timber townhouses, there are large deformation of east and south direction. They have few bearing walls at short direction, however they did not destroyed. In the future, we need to analyze the cause of the fact.
To investigate liquefaction characteristics of undisturbed and remolded samples with same density and shear wave velocity, undrained cyclic triaxial tests were performed. High quality undisturbed samples were collected by Gel-Push sampling. Remolded samples were prepared by dry/wet tamping adjusting the specimen densities and the shear wave velocities almost same as the undisturbed sample. The results show, even though they have same density and shear wave velocity, the liquefaction behavior was different between the undisturbed and the remolded samples. The difference may be caused by a cementation effect by aging and/or an inherent anisotropy of the specimens.
On March 11th, 2011, a gigantic earthquake of moment magnitude Mw 9.0, which is officially named “The 2011 Off the Pacific Coast of Tohoku Earthquake”, caused severe liquefaction damage over the long stretch of reclaimed lands along the coast of the Tokyo Bay. In response to this earthquake, liquefaction-induced soil subsidence map for the eastern part of Tokyo Bay area was immediately prepared by comparing a set of Digital Surface Models before and after the earthquake, and subtracting tectonic displacement. In this study, soil subsidence map is further extended to cover the coastal part of Kawasaki city. The spatial pattern of ground subsidence shown in subsidence map is consistent on the whole with that described in the damage investigation report.
On 16th of April 2016, the Kumamoto earthquake (Mw 7.0) hit the Central Kyushu Region, Japan, following a Mw 6.2 shock on 14th of April. The earthquake sequences caused severe damage in Kumamoto Prefecture, for example, Kumamoto city, Mashiki Town and Aso Caldera area. This report presents quick reconnaissance results focusing on geotechnical damage features, especially of residential land and earth structures which were observed during field investigations after the main shock. In Mashiki Town, residential houses seem to have been structurally damaged by seismic motion. On the other hand, in a developed land in Aso Caldera area, there were a lot of houses damaged by large deformation of sub soil due to ground motion. The cause of collapse of embankment of Kyushu Highway can be liquefaction of the foundation composed of loosely deposit soil, since the site is located at the old river channel.
This study investigates the effects of drained and undrained cyclic loading history on anisotropy of small strain shear moduli and liquefaction resistance of Toyoura sand. The test results show that the anisotropy of the specimen increase with increase in the number of drained cyclic loading history, and there is a good correlation between the small strain shear moduli and liquefaction resistance. In addition, the anisotropy of soil structure was lowered due to the undrained cyclic loading history, and re-liquefaction strength tends to decrease significantly. On the other hand, we discussed the development of strain and excess pore pressure of specimens with different relative density.
This paper describes an overview of proposal, from a mid- and long-term“ academia” perspective, for the planning, design methodology, operational technologies and supporting social norms, systems and other nontechnology related conditions for the functions and performance that should be provided by infrastructure such as road and other mobility space, taking into consideration a future in which there will be dramatic changes in the performance and functions of diverse transport modes ranging from automobiles to pedestrians. The authors hope that this paper will serve as guidelines for the promotion of intelligent transport systems （ITS）that enable important matters and issues to be shared and considered when studying the approach to ITS and the future vision of ITS, in order to enable people from various perspectives including government, the private sector and research institutions to promote research and development, practical application and introduction based on a common frame of reference.
This research reports results of the disaster drill in Ishinomaki city by the disaster evacuation information support system “COCOA” in November 15, 2015. COCOA is developed by the Numada laboratory of the University of Tokyo. COCOA can perform the real time information gathering and sharing of evacuee with staffs of Ishinomaki city. Then, the staffs can respond effectively based on the collecting information by COCOA with name lists at each evacuation facility to understand the situation of vulnerable people.