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Sadakane S.,University of Tokyo | Kawaguchi K.,University of Tokyo | Taguchi T.,Okabe Corporation
Journal of Structural and Construction Engineering | Year: 2013

Devises using the rolling of viscoelastic materials such as rubber is proposed, and a practical procedure for easy evaluation of the rolling resistance of them is required. This kind of research has been already established in the field of tire technology, and many patents are submitted. One of the approaches to simulate the rolling resistance of viscoelastic materials is to calculate the energy dissipation of a rolling model from the strain and stress obtained from a finite element-based method of an elastic model, and the loss factors of the material determined separately. In this paper, a new devise using the rolling of O-ring rubber is proposed and the method of simulating the rolling resistance of viscoelastic materials is applied. Compared with an experiment and dynamic finite element analysis, the validity and the qualitative aspects of the proposed method are discussed.

Taguchi T.,Okabe Corporation | Kawaguchi K.,University of Tokyo | Ohya S.,University of Tokyo
AIJ Journal of Technology and Design | Year: 2016

A New base-isolation system, Hybrid-Rocking Column, is proposed and described. Several prototype scaled models are manufactured and tested. Shaking table tests are carried out and the behavior of the models was observed. The results of the tests and considerations especially on the effect of friction are reported.

Nakaya K.,Hokkaido University | Nakaya K.,Okinawa Churashima Research Center | Tomita T.,Okinawa Churashima Research Center | Tomita T.,Hokkaido University | And 7 more authors.
Scientific Reports | Year: 2016

Five striking and prey capture events of two goblin sharks were videotaped at sea for the first time, showing their extraordinary biting process. The goblin sharks swung their lower jaw downward and backward to attain a huge gape and then rapidly protruded the jaws forward a considerable distance. The jaws were projected at a maximum velocity of 3.1 m/s to 8.6-9.4% of the total length of the shark, which is by far the fastest and greatest jaw protrusion among sharks. While the jaws were being retracted, the mouth opened and closed again, which was considered a novel feeding event for sharks. Phylogenetic evidence suggested that their feeding behavior has evolved as an adaptation to food-poor deep-sea environments, possibly as a trade-off for the loss of strong swimming ability.

Fujii S.,Okabe Corporation | Tagawa H.,Nagoya University
Journal of Structural and Construction Engineering | Year: 2011

In the previous research by the authors, the buckling restrained braces (BRBs) using round steel bar cores and double steel tubes were developed and some loading tests revealed that the BRBs have sufficient capability as hysteretic dampers. However the test specimens were relatively small and limited to the rigid connection type. The present paper firstly presents evaluation of the rotation characteristics of the outer tube end and loading tests using the element specimens. Then some full-scale tests are conducted using rather large test specimens in which the pin connection type BRBs are employed in addition to the rigid connection type ones. The test results reveal the behavior of the inner tubes, influence of the number of contraction allowance parts, energy dissipation capacity and behavior characteristics of the pin connection type BRBs. Finally, the design conditions of the outer tubes are discussed considering the evaluation results of the rotation characteristics of the outer tube end.

Fujii S.,Okabe Corporation | Tagawa H.,Nagoya University
Journal of Structural and Construction Engineering | Year: 2010

This paper presents an experimental study on the buckling-restrained brace (BRB), in which round steel bars and double steel tubes are employed for core members and buckling-restraining members, respectively. The inner tube restrains buckling of the core members directly and the outer tube restrains buckling of the inner tube through the spacers. The core member of round steel is divided into two bars, and they are connected with a central coupler. The outer tube is connected to the central coupler by welding for preventing the outer tube from falling by self-weight. This bracing system has plural contraction allowance parts permitting the plasticity contraction of the core member. The authors carried out the element tests of the core member, and also carried out the full-scale cyclic loading tests of the brace. The test results revealed that the proposed BRB has sufficient capability as a hysteretie damper under the control of the compressive axial force by the number of contraction allowance parts and the fixing methods of inner tubes.

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