Shenzhen Skyscraper Wobbles Again Following Evacuation

The 75-story skyscraper in Shenzhen that mysteriously shook and caused a panicked evacuation Tuesday wobbled again in the following two days, although authorities said no major abnormality was detected.

The Shenzhen urban construction authority said late Thursday that renewed shaking was detected in the SEG Plaza tower in the city's renowned Huaqiangbei electronics shopping area, though it said the tremors were within an acceptable range.

It was the third consecutive day that the iconic building in Shenzhen was reported wobbling. Thousands of people evacuated the structure Tuesday, and the U.S. consulate in Guangdong warned Americans to avoid the building and the nearby area.

The 356-meter building was put into use in 2000 and hosts Asia’s largest electronics market. Authorities closed the building for investigation after the incident but allowed vendors who had shops there to enter and move their assets.

On Wednesday, vendors in the building said they felt shaking again in the early afternoon. The urban construction authority later said vibration acceleration on the top floor, a measure of the building’s vibration, peaked at 0.044–0.045 meters per second per second (m/s2) Wednesday afternoon, according to two professional inspection institutions.

According to China’s national standards for high-rise buildings, the maximum vibration acceleration for the top of office and hotel buildings is 0.25 m/s², meaning the shaking of the SEG Plaza was within the regulatory limit. The building’s vibration acceleration Thursday was 0.037 m/s², and the main structure of the building was secure, Shenzhen’s urban construction authority said.

City authorities have yet to release official conclusions on the vibrations. An initial investigation indicated that various factors might cause the shaking, including wind, railway operation and temperature, the Guangdong provincial government’s safety watchdog said late Tuesday, citing experts on an inspection team. The building was vibrating vertically rather than swaying side to side, according to an internal report circulated online.

In a separate report, Huang Mingfeng, an architectural engineering professor at Zhejiang University, said the shaking of the SEG Plaza is very likely linked to its antenna producing resonance under certain wind conditions.

Huang suggested the installation of a spoiler to reduce the chance of resonance. Huang told Caixin that the report was an analysis based on public materials without giving more details.

In 1999, the SEG Plaza building wobbled the day after its antenna was installed, according to Jin Dianqi, who studied the project for his master's degree thesis in 2001. Jin, who is the chief operating officer of the Shenzhen Urban Public Safety and Technology Institute, is a member of the expert team studying the latest incident.

According to Jin’s 2001 paper, the 1999 shaking happened during a day with fine weather and mild wind. It was caused by a miscalculation in the antenna design that caused resonance. The construction team cut off part of the antenna to fix the issue, according to Jin.

Contact editor Han Wei (weihan@caixin.com) and editor Bob Simison (bobsimison@caixin.com)

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