Effect of the time delay on the magnitude of the onset galloping wind speed in semiactive controlled suspension bridges

To increase the onset galloping wind speed, after which galloping of the flexible suspension bridges occurs, resulting in the failure of these bridges due to wind, semiactive control mechanisms could be installed in the bridge to increase its damping. The time delay in processing the active control force and the actuator's dynamics are, however, major practical problems, which may affect the dynamic stability of the semiactive controlled structure. This paper shows the effect of the time delay on the magnitude of the onset galloping wind speed for a suspension bridge controlled by a semiactive control mechanism. It is shown that the time delay decreases the magnitude of the onset galloping wind speed. This makes the suspended cables in the suspension bridge susceptible for galloping, which may cause progressive collapse for the bridge at low mean wind speeds. This could be avoided if the active control force is designed considering the time delay effect.