Bridge Life Extension Using Semiactive Vibration Control

This paper focuses on the use of a control system to extend the life of a highway bridge. The safe life of a bridge can be more than tripled if the peak strain levels it experiences are reduced by just 33%. As of 2012, over 5000 bridges in the country have been deemed to be structurally deficient. Hence, the use of a vibration control system to extend the lives of bridges can be of tremendous societal impact. This paper utilizes a dynamic model of the Cedar Avenue tied arch steel bridge in Minnesota to investigate avenues for peak strain reduction. Simulations show that the use of passive structural modification devices such as stiffeners and dampers is inadequate to reduce the key resonant peaks in the frequency response of the bridge. Both active and semiactive vibration control strategies are then pursued. Active vibration control can effectively reduce all resonant peaks of interest, but is practically difficult to implement on a bridge due to power, size, and cost considerations. Semiactive control with a variable orifice damper in which the damping coefficient is changed in realtime using bridge vibration feedback can be practically implemented. Simulation results show that, when employed with multiple devices, the proposed semiactive control system can reduce the response at all critical resonant frequencies. Further analysis reveals that the location and number of actuators on the bridge is critical for controlling these specific resonant frequencies.