이순신대교 이상진동 원인 규명

Huge vertical vibration(maximum double amplitude: 52cm) was observed for about 2 hours and 20 minutes on the Yi Sun-sin Bridge in October 26th, 2014. This vibration exceeded the serviceability criteria(25cm) that is defined in design guidelines for steel cable-supported bridges (2008). While traffic was controlled and when the screens was removed which was applied to girder for epoxy coating, the vibration was vanished. Because the vibration was occurred in spite of aerodynamic stability evaluation for vortex-induced vibration(VIV) and flutter instability already check up before the construction, the wind tunnel test was accomplished with similar shape of the bridge at that time to find out the cause of an unexpected vibration. The tests were executed with original section and screens applied section at various scruton number situation to know the relationship between vibration amplitude and damping ratio. Also, using the relationship between amplitude and damping ratio, the damping ratio of real bridge at the 4th vertical vibration mode was estimated.