Seismic response control of multi-story base-isolated buildings using a smart electromagnetic friction damper with smooth hysteretic behavior.

• A novel friction damper is presented for seismic response control of buildings. • The damper force can be controlled by an electromagnetic mechanism. • A semi-active controller is proposed to smooth the hysteretic behavior of the damper. • A current driver is designed to modify the control current, reducing the time delay. • Numerical results demonstrate the energy dissipation capability of the damper. This paper studies the use of a smart/semi-active electromagnetic friction damper (SEMFD) for the control of seismic response of multi-story base-isolated buildings. The SEMFD consists of a ferromagnetic plate and two similar arrays of thick rectangular ferromagnetic-core coils (FCs) connected in series. The FCs are attached to the two sides of the ferromagnetic plate through two non-magnetic friction pads. The force in the damper is developed because of the friction between the friction pads and the ferromagnetic plate when the FCs moves relative to ferromagnetic plate. The normal force between the friction pad and the ferromagnetic plate is caused by the attractive magnetic interactions between the FCs arrays and the ferromagnetic plate. The magnitude of this force is controlled by a proposed semi-active controller that is capable of varying the current flowing through the FCs in such a way that it is able to avoid stick-slip motion by smoothing the nonlinear hysteretic behavior of the SEMFD. The capability of the SEMFD and the proposed semi-active controller to control the seismic response of base-isolated buildings is demonstrated by implementing them into the dynamic model of a six-story base-isolated building supported on lead-rubber bearings (LRBs). The numerical results show that the SEMFD and its semi-active controller are capable of limiting the displacement of the base floor without noticeably increasing the inter-story drifts and absolute accelerations of the floors. It is demonstrated that the parallel actions of the LRBs and the SEMFD in the base floor create a smart base isolation system that is capable of fully protecting a multi-story building from ground motions with intensities at a level as that of the ASCE 7–10 Maximum Considered Earthquake (MCE). [ABSTRACT FROM AUTHOR]