The 356m-high SEG Plaza first began shaking on Tuesday afternoon (May 18), causing an evacuation of people inside while pedestrians looked on in horror run outside building. SEG Plaza is a skyscraper in Shenzhen, Guangdong Province, China. Completed in 2000 and located at the junction of Shennan Road and Huaqiangbei Electronics Market, it stands 356 meters tall when the antenna (masts) height is included.
The vibration of SEG Plaza was caused by winds, according to preliminary findings reported by local media. At that time, there were no earthquakes in the area and local authorities said engineers had not found any safety abnormalities in the building or surrounding environment. Nor did the level of movement exceed building code limits.
SEG Plaza experienced sudden high frequency vibrations. Prof. Ahsan Karem said that , The building fundamental frequency of 0.17 Hz is far removed from the vibration frequency of nearly 2 Hz.
The city’s meteorological station reported a maximum wind speed of around 20 mph (8.9 m/s) at midday Tuesday, a rate of motion described as a “fresh breeze” by the US National Weather Service. The building has two masts with frequency around 2 Hz. Based on the meteorological station reported that wind speed appears at 20 mph, the masts were have the possibility of being exposed vibration due to vortex shedding possibly locking with its higher mode. This set the forced vibration of the building that possibly locked to higher modes of the building vibration. Vortex induced vibration is likely to be the cause of vibration in the building. If the Masts had 12′ diameter cylinders, and the wind speed is 8.9 m/s, with the cylinder strouhal number we can calculate the vortex shedding frequency is 2 Hz. Vortex induced vibration occurred when the vortex shedding frequency resonance with the natural frequency of the masts, then the masts starts driving vibration on building.
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