STUDY ON REDUCTION OF VIBRATION CONTROL DEVICESFOR AKASHI-KAIKYO BRIDGE

摘要

The Akashi-Kaikyo Bridge is a suspension bridge with a main span of 1,991m. Since thetowers have the height of 287m, they could suffer out-of-plane deformation due to vortexinduced oscillation even after completion of the bridge. Therefore, cruciform cross-sectionwhich had excellent aerodynamic stability was selected for the tower shafts and tunedmass dampers were installed in each tower shaft as vibration control devices. Furthermore,additional dampers were installed between the tower and the girder for double safety,because the towers are the most important structure of the suspension bridge. Accordingto the monitoring data, it has been found that recorded vibration amplitudes of the towershafts were very small compared with design values. It indicated that some of the vibrationcontrol devices may be unnecessary. Although the vibration control devices have to bemaintained in good condition, it has been demanded to reduce expenses for theirmaintenance. Therefore we started to study on damping performance and allowablevibration amplitude of the tower, in order to make some of the devices unnecessary. Aftersafety of the bridge will be confirmed without some devices, maintenance cost will bereduced.