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Araki Y.,Kyoto University | Asai T.,University of Illinois at Urbana - Champaign | Kimura K.,Kyoto University | Maezawa K.,Hojo Structure Research Institute | Masui T.,Kansai University
Journal of Sound and Vibration | Year: 2013

This paper presents a vertical quasi-zero stiffness (QZS) vibration isolator with a mechanism for adjusting restoring force. QZS vibration isolators have high initial stiffness and QZS around the static equilibrium position. This way, excessive deformation due to self-weight can be avoided while having enough vibration reduction capability to dynamic excitations. One of the main issues left for QZS vibration isolators is the difficulty in keeping the vibration reduction capability when the vibration isolated object is replaced. In such a case, adjustment of its restoring force becomes necessary in accordance with the self-weight of the newly placed vibration isolated object. This paper attempts to address this issue by proposing a mechanism that enables quick and easy adjustment of the restoring force of a QZS vibration isolator. The proposed mechanism consists of cranks and a screw jack. With the present mechanism, the restoring force provided by horizontally placed springs can be converted into the vertical restoring force of the vibration isolator. In the conversion, the vertical resisting force can be adjusted simply by applying and removing torque to the screw jack to change and hold the angle of inclined bars placed in the cranks. In this study, a prototype of a class of QZS vibration isolator having the proposed mechanism is produced. Shaking table tests are performed to demonstrate the efficacy of the present mechanism, where the produced prototype is subjected to various sinusoidal and earthquake ground motions. It is demonstrated through the shaking table tests that the produced prototype can reduce the response acceleration within the same tolerance even when the mass of the vibration isolated object is changed. © 2013 Elsevier Ltd. Source

Hojo T.,Hojo Structure Research Institute | Hashimoto M.,Hojo Structure Research Institute | Yahmasaki J.,Technical Research Institute | Tanaka T.,Kobe University
AIJ Journal of Technology and Design | Year: 2011

For global environment to be preserved, existing underground structure must be reused actively, because domolishment of it demands enormous energy compared with that of above ground. This papers shows a rebuilding project of 38-year-old bulding in which new structure was rebuilt on the reused basement ln reusing underground structure much attention was paid to balance of architectural planning and structural planing, structural continuance in the connection floor sefety of rebuiklt building which had much floors than the original one and quality control of reused structure in construction. As a result, effective reduction in construction cost and environmental impact was achieved. Source

Hojo T.,Hojo Structure Research Institute | Tabuchi M.,Otemae University | Sun Y.,Koba University | Tanaka O.,Koba University | Okuyama T.,Hojo Structure Research Institute
AIJ Journal of Technology and Design | Year: 2011

For reuse of existing underground structure, we have so far carried out experimental research on reinforcement of existing RC beam by increasing section. As a part of this research, anchorage performance of reinforcing bar, anchored horizontally into existing structure by the same way as post install anchor, needs to be confirmed. This report illustrates the pull out test on post installed reinforcing bar anchored to drilled concrete hole with shear keys, with non-shrinkage cement as filler. Test results show the effects of diameter of reinforcing bar, place and number of shear key and anchor plate. Source

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