Consideration of a hardening phenomenon of rubber bearings against seismic motions stronger than a design seismic motion is important for seismic isolated bridges. When the hardening phenomenon occurs, bearing stiffness suddenly increases and a large inertia force acts on the pier. This study investigated an active vibration control method using fuzzy control for the seismic isolated bridge to prevent the hardening phenomenon. The results showed that the controlled bridge prevented the rubber bearing from hardening in the event of an earthquake motion stronger than the design seismic motion.
