Time filter

Source Type

Ikeda T.,Chiba Institute of Technology | Takase Y.,Chiba Institute of Technology | Senoo Y.,TOBISHIMA Corporation
COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering | Year: 2015

A steel frame reinforced concrete building completed in 1965 was seismically retrofitted using seismic isolation braces with amplification mechanism. The building was subjected to shaking with a seismic intensity of upper 5 during the 2011 off the Pacific coast of Tohoku Earthquake. The seismic retrofit applied, however, minimized damage. The seismic retrofit performance was then examined based on the ground motions recorded in the building and the results of seismic response analysis using the records. As a result, it was revealed that the retrofit design goal was met and that the deformation of the building was controlled considerably as compared with the case with no retrofit.


Takase Y.,Chiba Institute of Technology | Ikeda T.,Chiba Institute of Technology | Suzumura T.,TOBISHIMA Corporation
COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering | Year: 2015

In Japan many buildings that were designed by the old code have been retrofitted structurally because lots of buildings designed by the old code were collapsed in the Southern Hyogo prefecture earthquake in 1995. Moreover many retrofitted structures were subject to strong seismic motion in the 2011 off the Pacific coast of Tohoku Earthquake. It was found that seismic retrofitting was very useful for seismically weak structures. In Sendai city, there is the 10-story residential building that was retrofitted using a passive seismic control system with an amplifier mechanism. The nonstructural members (partial walls) of the building had been damaged when Tohoku Earthquake, though their structural members had not been damaged. In order to evaluate the effect of the seismic retrofitting, we investigated the damage of the building after the 2011 off the Pacific coast of Tohoku earthquake. In addition we calculated the story drift angle by seismic response analysis to evaluate from the analytical viewpoint. As a result of the damage investigation of this building, it was obvious that the building was safe structurally. Furthermore, we verified when nonstructural members had been in failure using the modified compression field theory(Vecchio, F.J. and Collins, M.P, 1986). The nonstructural members were in failure before the peak acceleration. Thus, we concluded that the effect of the partial walls on structural performance was very small.


Kumagai K.,Tobishima Corporation Head Office | Terashima Y.,Tobishima Corporation | Kanematsu K.,Tobishima Corporation Head Office
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

In soft or squeezing ground, early section closers by means of invert shotcrete and invert concrete are often carried out to restrain deformation and stabilize the ground around the tunnel. However, while advancing the terrestrial face, there is a risk of damage, such as cracking, occurring in the invert due to redistribution of plastic ground pressure and the intrinsic characteristics of the ground. During excavation of the Ozaso Tunnel on the Tohoku Chuo Expressway, ground deformation caused the propagation of numerous cracks in the invert. This paper presents an outline of the investigation into the cracks, the major cause, and the design and construction management of the countermeasure work. © 2014 by Japanese Committee for Rock Mechanics.


Sattar A.,University of Tokyo | Konagai K.,University of Tokyo | Kiyota T.,University of Tokyo | Ikeda T.,Tobishima Corporation | Johansson J.,Norwegian Geotechnical Institute
Landslides | Year: 2011

The Hattian landslide, which was triggered by the 2005 Kashmir earthquake, formed one of largest landslide dams in the world and it has posed a serious threat of flooding to people living in the lower reach of the Jhelum River. In order to understand deformation occurring in the body of the dam, physical measurements using a Differential Global Positioning System (DGPS) were conducted. Gradual deformation and slowly developing backward erosion initially were observed, leading eventually to a sudden creation of a deep hollow on the downstream slope of the landslide dam. The dimensions of this eroded gully were determined by laser scanning, and the results showed a significant loss of soil volume and a large change in the body of the dam. A breach formation model was used to predict the outflow hydrograph generated by constant downcutting of dam during a breaching event. A run-off analysis of the outflow hydrograph was conducted to evaluate inundation levels of flood waves in case the dam is breached. Hazardous downstream locations were identified near the junction of the Karli and Jhelum Rivers, suggesting a need for early warning system in order to avoid loss of lives. © 2010 Springer-Verlag.


Ueno H.,Tobishima Corporation | Ueno H.,Transport and Technology Agency | Hisada K.-I.,University of Tsukuba | Ogawa Y.,University of Tsukuba
Special Paper of the Geological Society of America | Year: 2011

Two types of thrust duplex structures were identified in excellent exposures of the deep level of the Jurassic to Cretaceous accretionary complex in the Kanto Mountains, central Japan, and the thickening ratio and shortening ratio were calculated. Simple (S type) and composite (C type) duplexes are mapped in an excavation site 100 × 40 m in extent. The beds of the S type and C type duplexes were thickened by factors of 5.8 and 6.0, respectively; however, the C type duplex includes four orders of smaller duplexes within it that underwent their own shortening. Thus the total thickening factor may attain at least 6-13, indicating a comparable degree of thickening at the level of greenschist facies conditions (approximately10 km or more in depth) in the accretionary prism. © 2011 The Geological Society of America.


Kiyota T.,University of Tokyo | Sattar A.,University of Tokyo | Konagai K.,University of Tokyo | Kazmi Z.A.,University of Tokyo | And 2 more authors.
Soils and Foundations | Year: 2011

On February 9 2010, the landslide dam formed in the Kashmir earthquake that occurred on Oct 8 2005 at Hattian Bala in Pakistan was breached after incessant rains. The authors had been involved in a research project to monitor the long-lasting change of the landslide mass at regular 6 monthly intervals since June 2008, and they noticed that air-exposed pieces of sandstones and mudstones of the landslide mass had disintegrated and crumbled due to slaking that dated back to the breach. The change in the landslide mass shape observed between June 2008 and November 2009, did not seem so significant except for a 300 m-long gulley that appeared all of a sudden at the toe of the mass during winter time from 2008 to 2009. Displacements from GPS-measurements conducted in June and November 2009 showed that the crest part subsided by about 10 cm while the toe part heaved slightly up where the overflowed water fell into the eroded gully. A field survey was conducted over the breached landslide dam in April 2010, two months after the breaching event. A severely eroded breach channel was observed along the spillway, which was excavated immediately after the formation of the dam. Given the chronological change in precipitation of the catchment area of Hattian Bala obtained from the TRMM (Tropical Rainfall Measuring Mission) satellite data, the dam is considered to have been breached due to the overtopping of water over the landslide mass of slakable nature. The slakable nature of the material is discussed through both standard slaking tests and advanced unconventional direct shear tests on prepared specimens. Significant creep deformation and a reduction in their peak strength were observed as the slaking developed in the specimens, suggesting that the slakable nature of the mudstones might have been responsible for the breach of the landslide dam.


Shiotani T.,Kyoto University | Osawa S.,Kyoto University | Momoki S.,Tobishima Corporation | Ohtsu H.,Kyoto University
Springer Proceedings in Physics | Year: 2015

In recent years, a lot of accidents associated with infrastructures occur in Japan because of the remarkable deterioration of the infrastructures. Considering the expected reduction of construction investment year after year, it is important to repair and reinforce those structures with the limited budget as well as to extend their service life in the future. From the viewpoint of management and maintenance for those ageing infrastructures, preventive maintenance shall be taken rather than the reactive maintenance. In the preventive maintenance, repairing and reinforcing structures shall be implemented before any fatal deterioration to the structures. However, the reasonable diagnostic method for preventive maintenance has not been established so far. NDT approaches to diagnose the early internal damage of structures is thus in high demand. To solve these issues, the authors had proposed “AE tomography” which executes both AE monitoring and elastic wave tomography. The AE tomography enables to provide accurate AE source locations as well as velocity distribution with the tomography simultaneously. In this paper, in order to verify this proposed AE tomography for in situ infrastructures, deteriorated RC bridge deck for bullet trains was investigated. © Springer Science+Business Media New York 2015.


Matsumoto K.,Tobishima Corporation | Momoki S.,Tobishima Corporation | Shiotani T.,Kyoko University | Kobayashi Y.,Nihon University
Emerging Technologies in Non-Destructive Testing VI - Proceedings of the 6th International Conference on Emerging Technologies in Nondestructive Testing, ETNDT 2016 | Year: 2016

Establishing a method for health evaluation of infrastructure is an urgent issue. The authors have been studying on practical implementation of elastic wave tomography that is capable of making comprehensive health evaluation of civil structures. The elastic wave tomography integrates numerous scanning line data. For collecting scanning line data, installing sensors at sending and receiving points is essential. It was therefore necessary to allocate and reallocate sensors numerous times. In this study, a new tomography measurement method is developed, which requires no sensors at wave generation points. Properties of wave made at random locations on the measured target surface by the inspector are estimated based on the receiving data at specific points. A large amount of scanning line data can be collected by allocating a minimum number of sensors. Then, efficient tomography measurement of elastic waves is possible, enabling the use of hammering tests that are conducted in various types of structures. © 2016 Taylor & Francis Group, London.


Behnia A.,University of Malaya | Chai H.K.,University of Malaya | Yorikawa M.,Tobishima Corporation | Momoki S.,Chiba Institute of Technology | And 2 more authors.
Construction and Building Materials | Year: 2014

Elastic stress wave methods are attracting increasing attention from researchers and practitioners for real time monitoring of structures as well as quantitative evaluation of damage. The acoustic emission (AE) and travel time tomography (TTT) techniques are promising elastic waves-based diagnosis approaches for condition assessment of structures. In this research, fiber reinforced concrete beams loaded under flexure were monitored using both the AE and TTT techniques. The primary aim was to evaluate the development of fracture in beams in a non-destructive manner, with the two adopted techniques complementing each other to provide a more reliable assessment. There was satisfactory agreement between the results of AE parametric analysis and tomographic reconstruction, suggesting the feasibility of integrating the two techniques for a more comprehensive and effective condition assessment of structures. © 2014 Elsevier Ltd. All rights reserved.


Kazmi Z.A.,COMSATS Institute of Information Technology | Konagai K.,Yokohama National University | Ikeda T.,Tobishima Corporation
Journal of Earthquake Engineering | Year: 2014

A devastating earthquake occurred in Kashmir, Pakistan on October 8, 2005. This earthquake resulted from reactivation of a known active fault later defined as the Balakot-Bagh fault, which caused widespread slope failure throughout its stretch, particularly around Muzaffarabad, the provincial capital of Azad Jammu and Kashmir. This slope failure resulted in a huge amount of debris material which flows in deeply incised creeks during monsoon and hits the inhabitants along the valley in Muzaffarabad. Two GPS measurements are carried out along with channel morphometric parameters and observed changes to investigate the effect of debris flows along these creeks during monsoon. Other than the physical measurements, actual debris flow is simulated using the Depth Average Material Point Method (DAMPM) after carrying out parametric study and calibrating the model for subject topographical and geological settings. The generalized effect of different input parameters of the model on debris flow runout features is studied and discussed in detail. After ensuring validation of the numerical tool, the contribution of a single closed-type check dam to decrease runout intensity to its downstream reach is also investigated for different locations to obtain optimized selection. © A. S. Elnashai.

Loading TOBISHIMA Corporation collaborators
Loading TOBISHIMA Corporation collaborators