WIND RESISTANT DESIGN FOR LONG-SPAN SUSPENSION BRIDGES

Considering the trend of longer bridges in the future, aerodynamic ins tability plays a major role in their design. In this paper, the aerody namic characteristics and the efficiency of the structural countermeas ures for aerodynamic instability of long span suspension bridges are d iscussed using the newly developed direct flutter analysis method for longer spans than the Akashi Kaikyo Bridge (main span 1990 m). For sus pension bridges longer than the 2000 m-class the aerodynamic character istics become worse as shown by the drop in flutter wind speed and the coupled torsional-vertical flutter response. The efficiency of the st ructural countermeasures for long span suspension bridges decreases fo r spans longer than 2000 m. Finally, the mode-control countermeasure ( strengthening of deck rigidity in some region) was proved to be effici ent in gaining stability against flutter.