Magnetorheological fluid damper (MR damper) has been expected to control the response of civil and building structures
in recent years, because of its large force capacity and variable force characteristics. At first, a series of real-time hybrid
tests was conducted. The important objective of this paper is to verify the validity of real-time hybrid tests by
comparison with the test results of shaking table tests by using the same MR damper. The maximum damping force of
the MR damper is 10 (kN), the stroke is 600(p-p) (mm), and the maximum piston velocity is 1(m/s). To determine the
control force of the MR damper, optimal control theory and skyhook control were employed. The capability of the MR
damper to control the response displacements and accelerations of base isolation system was verified by both shaking
table tests and real-time hybrid tests.
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. It's 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.
This study deals with a shake table test on a three-story base-isolated steel frame. The frame rests on four roller bearings for isolation and is equipped with four laminated rubbers as shear spring. An MR damper is used in the test to perform semi-active seismic response control. The basic control algorithm applied in the study is to simulate the load-deflection of an origin-restoring friction damper (ORFD) which is a sort of friction damper that looses its resistance when it moves toward the origin, making sure for the base-isolated system to minimize residual displacement even after an extremely strong ground motion. Also attempted is a hybrid type control that superposes viscous damping on the ORFD when the damper moves from the peak displacement toward the origin.
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.
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 damper's hysteresis shape is controlled, aims to reduce the isolator's 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 isolator's displacement without increasing the acceleration responses.
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