Experimental Study on Overall Flexural Deformation Response Control for Smart High-Rise Structures

Abstract eng:
This paper discusses seismic response control of high-rise building utilizing magneto-rheological fluid damper (MR damper). Generally, during earthquake, high-rise buildings show not only shear deflection which occurs in inter-story must be taken into account, also the flexural deformation which is caused by column elongation must be considered. Some previous researches have proposed of protective system for such high-rise buildings based on a flexural deformation using some passive viscous dampers set in vertical direction of the building. Our challenges discuss the seismic response control for such high-rise buildings base on the flexural deformation using a variable damper. As a feasible study, we have conducted shaking table tests for a scaled bending-shear model with one mass system and scaled MR damper model set in vertical directions of the model. In this study, ON/OFF control algorithm that switched by damper response is adopted, and the reduction of response acceleration is discussed. A mechanical bending-shear model, which shows a behavior of bending vibration of a high-rise building is considered in this study. A cantilever (bending spring) is a principal member for the model. A suppress spring restricts rotational movement of the top of the model. A variable damper has been set into the vertical direction to control rotational motions of the system. The variable damper is switched ON or OFF during earthquake response. Damper becomes “stiff” when damper is switched ON. And the damper becomes “soft” when damper is switched OFF. We have conducted shaking table tests of our scaled bending-shear model inputted several observed ground motions. The variable damper force nine times larger than the force without magnetic field when 1.5 amps exciting currents is applied. As a result of tests, it is clear that ON/OFF control can reduce the maximum response well at the view point of acceleration response. In the case of passive ON, slightly larger response vibration continues under shorter period after maximum response. This control method is not cause of shortened natural period of the system and suppresses the increase of response acceleration. It shows that ON/OFF control has high efficacy to reduce mean average response acceleration and displacement during earthquake. It is expected that proposed control method would be a useful technique to control vibration of high-rise buildings where bending deformation is dominant.

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