Expected to open later this year, the Shanghai Tower will soon become the tallest building in China—second worldwide only to the Burj Khalifa in Dubai.
A 2006 competition first brought the building’s designers together. As director of design for a Gensler team led by Jun Xia, Marshall Strabala—who later left to start his own firm, 2DEFINE Architecture—worked with architects at Gensler on the project, as well as Thornton Tomasetti, Cosentini, PHA, Tongji University and Edgett Williams Consulting Group.
...
How did the structure and form for Shanghai Tower come to be?
We had to come up with the smallest amount of skin possible. Simple geometry tells you that’s a circle. But a circle is the worst shape for wind engineering because no matter which way the wind comes the building feels the same force. So the inside is a circle, the outside is a triangle. A triangle is not a really great shape for wind, but a twisted triangle is very good. We learned that from Santiago Calatrava’s Chicago Spire, and his building in Malmö, Sweden. Twisting these buildings actually reduces wind loads considerably.
The idea was to do something very simple and repetitive—a series of stacked cylindrical volumes that get smaller as they go up—and make the image taper with this outer skin.
So the twisting form arose out of the engineering solutions?
The building started as an expression of the Chinese building code. Once you’re above 100 meters, which is about 30 stories, the code changes. You have to start adding what are called “areas of refuge” every 15 stories. This is just for safety. Someone determined in China that that’s about how many flights an old person can walk during an emergency without having to rest. So it had to be divided up into 15-story segments.
The offices are a series of cylinders, but that’s a very nasty form for the wind. So the outside skin confuses the wind, the inside is what we sell. It’s very rational how this thing developed. When we were designing, we could never get it to work starting at the bottom and going up, so instead we had the shape, and we started at the top of each zone and took that straight down so that it fits within the envelope.
