Progress in the application of active vibration control technologies to long-span bridges in Japan

摘要

Vibration of long-span bridges can be caused by various types of dynamic excitation, wind-induced vibration may be the most critical for long-span bridges such as suspension bridges and cable-stayed bridges. Typical example are pylons, and wind induced vibration of these during erection affects the safety serviceability of the structure. Formerly, sliding-block dampers using wires were installed to reduce wind-induced vibration of pylons, but these had the defects of requiring large space for installation, and there were difficulties with evaluation of damping effects. For the past 15 years, passive-type tuned mass dampers or tuned liquid dampers have become popular in japan, but as natural frequencies of pylons vary widely according to the height of pylons during erection, several sets of mass dampers of different naturat frequencies have to be prepared. To overcome these drawbacks of passive type mass dampers, actively controlled mass dampers have been developed to reduce the vibration of various modes of structures. The pylons of the Rainbow Suspension Bridge in Tokyo incorportated the first application of the active control system in the world in 1991. The results of active control were found to be very effective, and its technologies have already been applied to more than 10 pylons of long-span bridges in Japan. This paper reviews progress in the application of active vibration control technologies to long-span bridges in Japan.