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Noda A.,Kozo Keikaku Eng. Inc. | Hashimoto C.,Nagoya University | Fukahata Y.,Kyoto University | Matsu'ura M.,The Institute of Statistical Mathematics of Tokyo
Geophysical Journal International | Year: 2013

We developed an inversion method to estimate unbiased interseismic slip-deficit rates at plate interfaces from observed GPS velocity data with an elastic dislocation model. In this method, first, we subtract theoretical surface velocities due to known steady relative plate motion from the observedGPS data, and presume the residuals to be caused by slip deficit at plate interfaces. However, the observed GPS data always include rigid block translation and rotation, which cannot be explained by the elastic dislocation model.We treated the rigid block translation and rotation as systematic errors in the analysis, and removed them by transforming the velocity data into the average strain rates of triangle elements composed of adjacent GPS stations. By this transformation, original information about intrinsic deformation is preserved. Applying a unified Bayesian inversion formula to the GPS strain data, we can obtain unbiased slip-deficit rate distribution.We demonstrated the applicability of the method of GPS strain data inversion through the analysis of interseismic GPS velocity data (1996-2000) in the Kanto region, central Japan, where the North American (NAM), Pacific (PAC) and Philippine Sea (PHS) plates are interacting with each other in a complicated way. From this analysis we found a broad and high slip-deficit rate zone on the NAM-PHS plate interface, extending from southeast off the Boso peninsula to the Tokai region through the Izu-Mainland collision zone. Two high slip-deficit rate zones along the Sagami and Suruga troughs correspond to the source regions of the 1923 Kanto earthquake (M7.9) and a potential Tokai earthquake. On the PHS-PAC plate interface, though the estimation errors are large, we found a moderate slip-deficit rate zone far southeast off the Boso peninsula, where an M7.4 earthquake has occurred in 1953. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.


Miyamoto A.,Yamaguchi University | Yabe A.,Kozo Keikaku Eng. Inc.
Journal of Physics: Conference Series | Year: 2011

In this paper, we propose a new method of assessing the condition of existing short- and medium-span reinforced/prestressed concrete bridges based on vibration monitoring data obtained from a public bus. This paper not only describes details of a prototype monitoring system that uses information technology and sensors capable of providing more accurate knowledge of bridge performance than conventional ways but also shows a few specific examples of bridge condition assessment based on vehicle vibrations measured by using an in-service public bus equipped with vibration measurement instrumentation. This paper also describes a sensitivity analysis of deteriorating bridges based on simulation of the acceleration response of buses conducted by the "substructure method" employing a finite element model to verify the above bridge performance results. The main conclusions obtained in this study can be summarized as follows: (1) Because the vibration responses of passenger vehicles, such as buses, have a good linear relationship with the vibration responses of the target bridges, the proposed system can be used as a practical monitoring system for bridge condition assessment. (2) The results of sensitivity analysis performed by the substructure method show that bus vibration responses are useful for evaluating target bridge performance. (3) The proposed method was applied to a network of real bridges in a local area to evaluate its effectiveness. The results indicate that the proposed method can be used to prioritize the repair/strengthening works of existing bridges based on various vibration information in order to help bridge administrators establish rational maintenance strategies. © 2011 Published under licence by IOP Publishing Ltd.


Yabe A.,Kozo Keikaku Eng. Inc. | Miyamoto A.,Yamaguchi University
Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Management | Year: 2012

Bridges as one of the important infrastructures are suffering from many defects during their service lives. In our country, because there are a huge amount of existing short and medium span bridges in service, it is becoming one of major social concern how those bridges can be maintained in good condition during their whole lifetime. In this paper, a method of the condition assessment is proposed newly for existing medium & short span RC bridges based on monitoring data from public bus vibration. This paper describes the details of not only a prototype monitoring system using information technology and sensors which is capable of providing more accurate knowledge of bridge performance than traditional ways but also a few specific examples of bridge condition assessment by public bus vibration measured in operating on the bridge based on the data from the system. This paper also describes a sensitivity analysis for deteriorating bridges using the city bus acceleration response by using "substructure method" based on finite element model for verification of the above mentioned results of bridge performance. © 2012 Taylor & Francis Group.


Miyamoto A.,Yamaguchi University | Yabe A.,Kozo Keikaku Eng. Inc.
Journal of Civil Structural Health Monitoring | Year: 2012

This paper proposes a new method of assessing the condition of existing short- and medium-span bridges based on monitoring data obtained from public bus vibration. This paper not only describes details of a prototype monitoring system that uses information technology and sensors capable of providing more accurate knowledge of bridge performance than conventional ways but also shows a few specific examples of bridge condition assessment based on public bus vibration measured by using an in-service public bus instrumented for vibration measurement. This paper also describes a sensitivity analysis of deteriorating bridges based on city bus acceleration response conducted by the "substructure method" based on a finite element model to verify the above mentioned results regarding bridge performance. The main conclusions obtained in this study can be summarized as follows: (1) because the vibration responses of a passenger vehicle such as a city bus has a good linear relationship with the vibration responses of the target bridges, the proposed system can be used as a practical monitoring system for bridge condition assessment; (2) the results of sensitivity analysis performed by the substructure method show that public bus vibration responses are useful for the evaluation of target bridge performance; (3) the proposed method was applied to a network of real bridges in a local area to evaluate its effectiveness. The results indicate that the proposed method can be used to prioritize the repair/strengthening works of existing bridges based on various vibration information in order to help bridge administrators establish rational maintenance strategies. © 2012 Springer-Verlag.


Patent
Kozo Keikaku Eng. Inc. and Sanwa Tekki Corporation | Date: 2013-12-27

A device for damping a transmitted vibration by the moment of inertia of a fly wheel and the adjustable resistance force of a viscous magnetic fluid to allow the viscous magnetic fluid exerts its property even under no external power source. A sleeve with an attached ball nut is disposed in a first cylinder so as to reciprocate. The reciprocating motion of the sleeve is converted into a rotational motion by a ball screw to rotate a fly wheel in a second cylinder and a generator rotating shaft. Between the fly wheel and the inner surface of the second cylinder, a sealed space is formed in which a viscous magnetic fluid is sealed. A magnetic field generating unit which generates a magnetic field running across the sealed space with the fly wheel serving as a part of a magnetic circuit is disposed on the inner circumference of the second cylinder.

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