Leaning tower

Shenzhen’s wobbly skyscraper

Skyscrapers are designed to sway on their foundations during earthquakes. But if a tower starts shaking for no apparent reason, is there might be a justification to panic.

That was the situation on Tuesday when the 350-metre SEG Plaza in Shenzhen started to vibrate, according to witnesses and videos later posted online.

The 71-storey building was evacuated and did not reopen until the following day.

Part of the problem is that no one can explain the sudden shifting. No seismic activity was recorded and local wind speeds were no more than breezy. There were no signs of damage in an initial structural review conducted by the city authorities. Officials said that engineers monitoring the building since Tuesday night had not reported any movements greater than the building code limits for skyscrapers.

The mystery was an immediate topic of conversation online, with local media quoting people working inside the building as saying that minor vibrations started to be felt at 11am, causing ripples on the surfaces of drinks.

By 1pm the vibrations were getting stronger. The furniture started to shake and the order was given to leave the premises.

Footage from the scene shows thousands of people running out of the building, some screaming in panic or losing their shoes in the rush to get out.

The Shenzhen Emergency Management Bureau announced it was investigating the incident, although SEG – the owner of the tower, which is the 18th tallest in Shenzhen – advised the public “not to listen to rumours” about what had happened.

SEG Plaza was built in 2000 and was designed by architect Chen Shimin, who was also responsible for Shenzhen’s old railway station and the Architecture Cultural Centre in Beijing.

The tower was constructed by a branch of China Construction’s Second Engineering Bureau, which also built the FAST radio telescope in Guizhou (see WiC314) and the Daya Bay nuclear power plant near Shenzhen.

Building collapses are becoming less common in China (se WiC23) but a five-storey hotel gave way last March, killing 29 people (it was being used as a Covid-19 quarantine centre). In another case in 2013, a 50-floor office building in Nanjing was evacuated because it was rocking to and fro. The cause was later discovered as a road-rolling machine working nearby, which had generated ‘resonance’ or amplified vibrations in the structure.

The building reopened a week later and is still in use today.

SEG Plaza is a mixed-use building, incorporating offices and a large electronics mall. The Chinese authorities banned the construction of skyscrapers taller than 500 metres last year, adding to height restrictions already enforced in leading cities such as Beijing.

Five of the world’s tallest skyscrapers are located in China, including the world’s second-highest building, the Shanghai Tower, which stands at 632 metres.

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