Yoichi Shiozaki

Development of 400kN magnetorheological damper for a real base-isolated building

A 400kN magnetorheological damper (MR damper) for a real base-isolated building was developed and its dynamic characteristics were verified by experimental tests. The MR damper has 950mm (+/-475mm) stroke and by-pass flow potion. A new type of Magneorheological fluid is also developed in order to apply to the MR damper. MR fluid had a property of the settlement of particles in dampers. Authors developed a new MR fluid, which keeps the particles in the fluid adequately enough for usual use of MR damper. Analytical model was discussed in this paper. The force by the bingham visco-plastic model was compared with the results of experimental tests. It was found that this analytical model is useful to predict the capacity of the MR damper.

Application of MR damper to base-isolated structures

This paper presents a comprehensive study on the application of the MR damper to base-isolated building structures. It first proposes a simple semi-active control algorithm for a base-isolated structure with an MR damper. The algorithm, in which the MR dampers hysteresis shape is controlled, aims to reduce the isolators displacement without increasing the acceleration responses of the upper structures. The second part of this paper covers the properties of an MR fluid and an MR damper developed for a base-isolated model structure. The damper has a nominal capacity of 40kN, which can be adjusted in accordance with the applied magnetic fields. In the test, the damper is subjected to cyclic sinusoidal displacements with different amplitudes, velocities and magnetic field intensities. The last part describes shaking table tests carried out using the MR damper and the base-isolated model structure. It is confirmed that the proposed semi-active control method is effective in reducing the isolators displacement without increasing the acceleration responses.

Application of Magnetorheological Fluid to Semi-Active Control of Building Structures by BRI and Partners

This study was aimed at developing an application technology of magnetorhological (MR) fluid with improving the stability of MR fluid. Variable damper using MR fluid (MR damper) has been expected to control the response of building structures in recent years, because of its large force capacity and variable force characteristics. The MR damper changes the controlling force by adjusting the magnetic field with electric current, and can control the damping forces simply. The semi-active control using MR damper stabilizes the response of the building in earthquake better than the conventional passive control. Authors developed some MR dampers and conducted shaking table tests for the research to improve the performance of building structures against earthquake. A 40kN MR damper with 500mm (+/-250mm) stroke was constructed. Authors conducted a shaking table test of the three-story large-scale structure that has an isolated base using MR damper, and the effectiveness of MR damper was verified. Finally, a 400kN MR damper was constructed and installed in an actual base-isolated residential building in order to improve the performance of the building. Introduction The Building Research Institute (BRI) of Japan and the U.S. National Science Foundation (NSF) initiated the U.S.-Japan Cooperative Research Program on Auto-adaptive Media (Smart Structural Systems) in 1998 [1], under the aegis of the U.S.-Japan Panel on Wind and Seismic Effects of the U.S.-Japan Cooperative Program in Natural Resources. At the Joint Technical Coordinating Committee (JTCC) meeting, research items and plans were discussed in detail for three research thrusts: (1) structural systems, (2) sensing and monitoring technology, and (3) effecter technology. BRI conducted a series of large-scale tests to verify some smart systems developed in this project [2]. The effectiveness of “Semi-active control by MR dampers”, “Damage detection system” and “Rocking energy dissipation system” was confirmed. This paper outlines the development of MR fluid and MR damper, the large-scale test results of response control of base-isolated building by MR damper and the implementation of an MR damper to an actual residential building. Some researchers worked on semi-active control by MR damper [3, 4]. But such a large-scale test has not been conducted. Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 2126-2133 doi:10.4028/www.scientific.net/KEM.270-273.2126

Shaking table tests on semi-active base-isolation system by magnetorheological fluid damper

Recent study is to the performance of variable dampers for reducing earthquake response of buildings or wind induced sway. The variable damper using magnetorheological fluid (MR damper) changes its damping force by changing the magnetic field acting on the MR fluid according to an electric current. MR dampers have a simple mechanism and don’t need a large amount of energy. Semi-active control using such a variable damper stabilizes building responses in an earthquake better than the conventional passive control. Basic characteristics of the MR damper have been clarified. This time, authors proposed control algorithm of base-isolated structure, which carried out semi-active control by optimal regulator theory. This control algorithm reduces response displacement and response acceleration for the purpose of, and aims at enhancements, such as safety and amenity. This paper presents a comprehensive study on the performance of the MR damper to base-isolated structure. Its describes shaking table tests on a three-story large-scale test frame with base-isolated structure. The test results verify the controlling system and the control effect as a semi-active device of the MR damper.