Shuddering Shenzhen Tower to Lose Masts, as Authorities Rule It’s Safe

Aging masts and wind-related “vortex-induced vibration” were responsible for the shaking of the 75-floor SEG Plaza in southern China’s Shenzhen in May, experts said Thursday, insisting that the building is safe.

They said removing the masts can “effectively” solve the vibration problem and suggested rearranging the masts’ lightning protection and rooftop flight beacon functions, according to a statement (link in Chinese) issued by local authorities.

The statement confirmed that the building was structurally safe under normal conditions and can “continue to be used,” following a two-month investigation. It comes after the 356-meter (1,168 feet) landmark skyscraper wobbled several times between May 18 and 20, leading to the evacuation of thousands. The U.S. consulate in Guangdong issued a safety alert warning Americans to avoid the building.

An earlier investigation by the Guangdong provincial government’s safety watchdog had suggested various factors that might have caused the shaking, including wind, railway operations and temperature.

However, the experts ruled out railway operation, construction work or rock blasting in the surrounding area, and the operation of air conditioning units, the statement said.

Monitoring data show the SEG Plaza in the renowned Huaqiangbei electronics shopping area shook 21 times from May 18 to 20, according to the statement. After testing and analyzing the rooftop masts, experts found that they experienced 21 periods of vortex-induced vibration over the two days, as did the building.

The experts said the building, which is more than 20 years old, had suffered “cumulative damage,” especially at points connected to the masts. However, they also said the damage only affected certain dynamic features and had no influence on structural safety as a whole.

Following the investigation, the city’s housing authority said they’re planning to demolish the aging masts and repair damaged areas in the near future. The building and its surrounding areas will be sealed off during the demolition, the authority said.

Caixin has learned that the May incident was not the first time SEG Plaza was rocked. In 1999, the building wobbled on the day after its antenna was installed, said Jin Dianqi, who studied the project for his master’s degree thesis in 2001.

According to Jin’s 2001 paper, the 1999 shaking happened during fine weather and mild wind. A miscalculation in antenna design was found to have caused the extreme resonance.

Contact reporter Wang Xintong (xintongwang@caixin.com) and editor Heather Mowbray (heathermowbray@caixin.com)

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