Feasibility study of using a semiactive electromagnetic friction damper for seismic response control of horizontally curved bridges

Semiactive control systems have been found to be more effective than passive and active control systems for seismic protection of bridges because of their reliable and adaptable characteristics. This paper presents a comprehensive investigation on the modeling and design of a semiactive electromagnetic friction damper (SEMFD) for the seismic response control of horizontally curved bridges. The proposed SEMFD possesses a simple configuration consisting of a ferromagnetic plate and two arrays of ferromagnetic core coils (FCs) attached to the two sides of the ferromagnetic plate through two friction pads. The attractive magnetic interaction between the FCs arrays and the ferromagnetic plate creates the normal force, which generates friction force as the friction pads and the ferromagnetic plate move relative to each other. The magnitude of this force can be controlled by varying the control current passing through the FCs. This semiactive controller, designed based on the optimal linear quadratic Gaussian control method, is capable of reducing the undesirable effects of stick-slip motion in the damper, while restoring the piston of the SEMFD to its initial position at the end of the excitation. The capability of the proposed SEMFD to mitigate the rigid-body motion of decks of horizontally curved bridges is demonstrated by implementing it into the dynamic model of a horizontally curved bridge prototype. The numerical results indicate that the proposed SEMFD is effective in limiting the motion of the deck and thereby preventing it from unseating, which is one of the most common modes of failure among horizontally curved bridges.