Originally published 2020-11-12.
Photo: Yahoo
In October 2020, engineers in Shanghai moved the five-storey Lagena Primary School, a building from 1935 weighing about 7,600 tonnes, to a new spot in the city’s Huangpu district. They did it with 198 computer-controlled supports that lifted the structure and shuffled it forward in small steps, a method nicknamed the “walking machine.” Over about 18 days the building travelled roughly 62 metres (around 203 feet) and turned about 21 degrees, clearing its old plot for a new commercial and office development while saving the historic school.
Here is how the move worked, why cities relocate old buildings instead of demolishing them, and what the viral video did and did not show.
The school and why it was moved
The Lagena school was built in the mid-1930s, when much of central Shanghai was being reshaped by foreign concessions and fast commercial growth. Buildings from that era are now treasured as part of the city’s architectural heritage, and many are protected by law.
The site was needed for a new commercial and office complex. Instead of knocking the school down, city planners chose to shift it to one side so both could exist. According to CNN, the building was meant to be protected at its new position and given a new use once the surrounding development was finished.
How the “walking” method works
The job was carried out by Shanghai Evolution Shift, a firm that specialises in relocating buildings. The process went roughly like this:
- Prepare the base. Engineers dug around the foundations and installed a strong frame of beams beneath the building so it could be carried as one unit.
- Fit the supports. Nearly 200 hydraulic jacks with moving bases were placed under the frame.
- Step forward. The supports were divided into two groups. One group lifted and carried the load while the other lowered, moved forward and set down again; then they swapped. Repeated over and over, this made the whole building inch along, much like someone walking with two pairs of legs.
- Monitor everything. Sensors and a central control system kept every support at the right height and pace, so the building was not twisted or strained.
The project’s chief technical supervisor, Lan Wuji, gave CNN a memorable image for this: “It’s like giving the building crutches so it can stand up and then walk.”
Watch the building move
The time-lapse below shows the school creeping across its site. Played at speed, it looks smooth and almost effortless.
What the clip does not show is the preparation that came first: surveys of the old structure, strengthening work, excavation around the foundations, planning the route and testing the control system. In most relocation projects that preparation takes far longer than the move itself.
What made this project unusual
Moving whole buildings is not new. Engineers have done it for well over a century using rollers, rails and later large jacks and self-propelled transporters. A famous example is the Cape Hatteras Lighthouse in North Carolina, moved about 2,900 feet inland in 1999 to protect it from beach erosion. Shanghai itself moved its 1930 Shanghai Concert Hall about 66 metres to make way for the Yan’an Elevated Road, raising it several metres at the same time.
Two features made the Lagena move stand out:
- Turning, not just sliding. Older methods using fixed rails work best in straight lines. The walking supports let the building rotate as it moved, so it could end up facing a new direction on a tight urban site. Lan Wuji told CNN that in his 23 years in the field he had not seen another company move structures along a curve, though that is his own claim rather than an independent assessment.
- Less temporary infrastructure. Because the supports carry the building themselves, there is less need to lay long tracks across a crowded city plot.
Is it really damage-free?
Early reports claimed the technology could move old buildings without any damage to them or their surroundings. That is too strong. Careful planning and constant monitoring keep the risk low, and many relocations finish with little or no harm, but every building is different. Old brick and timber can crack under uneven stress, and some structures are too fragile, too large or too awkwardly placed to move at all. Engineers decide case by case, and repairs after a move are common.
The reported 7,600-tonne weight also deserves context. It is heavy for a school, but not a record: much heavier buildings have been relocated in China and elsewhere, using similar hydraulic principles.
Relocation as a heritage choice
Moving a building saves the structure, its materials and its craftsmanship, but it changes the building’s relationship with the streets around it. Heritage specialists usually prefer to keep historic buildings where they stand, and see relocation as a compromise when the only alternative is demolition.
In fast-growing cities, that compromise can still be a good deal. China’s building boom since the 1990s has replaced vast numbers of older neighbourhoods, and the loss of historic fabric has been widely criticised. Projects like the Lagena move show a different approach: keeping meaningful old buildings while still making room for new ones.
A note on the economic claims
The original viral post linked the move to sweeping claims that China’s economy was growing far faster than the West’s despite the pandemic, and that China could build a city the size of Rome every two weeks. China’s economy did grow in 2020, by about 2.3 per cent according to official data, while most large economies shrank. But the Rome comparison is a loose talking point rather than a measured statistic, and it has nothing to do with this particular engineering feat. The story is impressive enough on its own terms.
Sources: CNN on the Lagena Primary School relocation; The Drive; Informed Infrastructure; Wikipedia: Structure relocation; Wikipedia: Cape Hatteras Light; Wikipedia: Shanghai Concert Hall. Lead photo via Yahoo.
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