Vibration Reduction Performance of an Active Damping Control System for a Scaled System of a Cable-Stayed Bridge

The main objective of this work is to develop an active damping system that can be used to reduce the vibrations of cables in stayed bridges. As a first stage, a laboratory physical scale model of a prestressed cable was used to characterize and test the dynamic performance of the damping system that comprises accelerometers to measure cable vibrations, an electromagnetic actuator which interacts with the cable to compensate for externally induced vibrations, and a digital controller in which control strategies and algorithms are defined. In the experiment, an additional actuator was used to excite vibration disturbances on the cable modifying its frequency and amplitude, and the location for the accelerometers was defined from simulations with a linear model of the cable to optimize the damping control method. Two different system identification approaches were used to calculate the frequency response function of the whole system (cable, accelerometers and actuators); the first approach used the spectral analysis to get initial dynamic results of the cable system, while the second employed the parametric identification to obtain the transfer function of the system, by which different models were assessed. Model reduction techniques and the direct synthesis approach were selected to get a second-order model for the controller. The active damping system was first evaluated with simulation studies and then, in the laboratory. Results show that the damping system reduces the vibration amplitude up to 50% for the resonance frequency. Complementary simulations using a full scale cable model of the stayed bridge with an equivalent active damping system, showed the same damping efficiency as for that in the laboratory experiment; however, a practical application must consider the scaling factor and the limitations of possible locations and orientations of the damping actuator to get the best dynamic performance.