In this study, twin box girder is applied to the super long multi-span suspension bridges with center span length of 3000-meter to improve the flutter wind speed. Next, center stay cables and X-type rigid frames are attached to gain higher flutter wind speed. The flutter wind speed of twin box girder type is improved compared to that of single box girder type. Furthermore, by analyzing the flutter vibration characteristics of the bridge and applying appropriate measures, it is possible to obtain a higher flutter wind speed. It is also found that flutter wind speed does not depends on number of spans.
