Active Control of Cable-Stayed Bridge with Close Modes during Construction

Nowadays, a great number of long span cable-stayed and suspension bridges are being constructed in China. As the length of the main span increases, vibrations of these long span bridges are becoming more serious and sometimes unacceptable during the construction period. In this connection, control devices should be installed to mitigate the vibration of the pylon and the cantilever girders. Compared with the passive damper system, the AMD system has significant advantages in terms of the control of various modes of the structures, especially for close modes of the bridge at cantilever construction stage. To control the multiple modes of the structure by using multiple AMD system, the design and placements of AMD is critical. The following two issues are studied for the vibration control of the bridge at cantilever stage under seismic excitations: (a) the design and the parameter optimization of the AMD system; and (b) the optimal placements of the AMD system. Simulation procedure is carried out to evaluate the effectiveness of the designed AMD systems for the vibration control, based on the model of the 3^rd Nanjing Yangtze River Bridge. The adaptabilities of the multiple AMD system are presented and the possibilities of applying multiple AMD systems to the long span bridges under construction are investigated.