Iemura - Professor, Graduate School of Civil Engineering, Kyoto University, Kyoto ۶۱۵-۸۵۴۰, Japan
Toyooka - Assistant Professor, Graduate School of Civil Engineering, Kyoto University, Kyoto ۶۱۵-۸۵۴۰, Japan
Pradono - ۳Post-doctoral Researcher, Graduate School of Civil Engineering, Kyoto University, Kyoto ۶۱۵-۸۵۴۰, Japan
Higuchi - Doctor Student, Graduate School of Civil Engineering, Kyoto University, Kyoto ۶۱۵-۸۵۴۰, Japan

Recently, a simple control method for seismic safety enhancement of civil structures using magneto-rheological (MR) dampers is developed. The simple control method is easy to quantify since it is based on earthquake engineering field in which hysteretic loops play an important role in seismic response reduction. A numerical example employing MR dampers with the simple control method under seismic excitation was carried out to portray the characteristics of the control method. The MR dampers are applied to the benchmark structural control problem for the seismically excited highway bridge. The bridge is isolated both at the abutments and at the central pier location. The MR dampers controlled with the simple method are installed at the isolation levels. The MR dampers are controlled based on displacement and motion’s directions only. Depending on the direction, the input voltage is always from a larger value to a smaller one. The MR damper with the simple control method shows the characteristics of negative stiffness friction damping. Combination of these hysteretic loops with those of the bearing results in virtually rigid-perfectly plastic force-deformation characteristics. The characteristics have large damping ratio while keeping low force transmitted to other structural members. Experimental tests on an MR damper are now on the way. The experimental results are expected to be presented in the onference.