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

Abstract

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, semi-active control mechanisms are installed in the bridge in order to increase the damping. The time delay in generating the active control force due to the actuator’s dynamics is, however, a major practical problem, which may effect on the dynamic stability and the controlled response of the semi-active 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 semi-active control mechanism. It is shown that the time delay decreases the magnitude of the onset galloping wind speed and the suspended cables in the bridge become susceptible for galloping and progressive collapse at low mean wind speeds. If the active control force is not designed properly, taking the time delay effect into consideration, the semi-active controlled suspension bridge might gallop and collapse at mean wind speed much smaller than the onset galloping wind speed.