Realization of Semi-active Control by MR dampers in Multi-Story Building Structures

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In the first year, a small MR damper with the maximum resistance of nearly 300N was designed and manufactured. Through a series of sinusoidal loading test, the stability of mechanical behavior of the damper was confirmed. It was also confirmed that the analytical model of the damper could be represented by a simple combination of a dashpot and a variable Coulomb slider, which is called a Bingham model. The exact ness of the model was confirmed by comparing the two load-deflection relations, experimental and simulated ones, obtained by a random loading test. Prior to the shake table test of a scaled steel frame subject to semi-active-control, damping property of the frame alone and the one with passive viscous dampers are studied. Then, the MR damper was installed into the frame and the effectiveness of semi-active control, simulating origin-restoring friction damper, was confirmed. It was found that the only negative point with the damper was that the resistance of the damper tends to be delayed to the input signal to control the capacity of the damper.In the following year, another small MR damper to perform semi-active control on base-isolated building model was manufactured. Mechanical behaviors of the damper were again represented by the Bingham model. In the case of base-isolated building model with the natural period of 2-3 seconds, the time lag of the resistance with regard to input control signal was found almost negligible. In this case, two types of semi-active control algorithms were made use of and compared. One is an instantaneous optimum control algorithm and the other is based on the balance between the half-cycle input seismic energy into the building and the hysteretic energy absorbed in the damper.