Vertical vibration control of suspension bridges subjected to earthquake by Semi-active MR dampers

In this paper, a semi-active control technique is presented to mitigate the seismic vertical response of suspension bridges using magneto-rheological (MR) dampers. MR dampers, as semi-active control devices, have received significant attention in recent years because of their adaptability of working as active control devices without requiring large power of sources. The most challenging problem in this study is that: how to install the dampers at the degrees along the bridge span far from the towers? In the present paper, to solve this problem, a «rigid truss» which is attached to the bottom of the bridge deck is proposed. The MR damper can be installed between the bridge deck and free-end of the truss. For numerical study, the Vincent-Thomas suspension bridge is chosen and different schemes, in point of number and location of the dampers view, have been proposed to get optimal performance of the dampers in reducing the bridge vertical responses. To reach this goal, all of the schemes are optimized, as well as the controlled and uncontrolled responses of the bridge are calculated under application of 15 major world-wide earthquake accelerogrames. The results indicate that the proposed models can effectively reduce the vertical responses of the example bridge.