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.
AN‘s Midwest Editor Chris Bentley met with Strabala while the architect was home in Chicago (these days Strabala, who recently rebranded his firm STRABALA+, spends much of his time in East Asia). A former associate partner at SOM, Strabala was the studio head under Adrian Smith, in charge of design for projects including the Burj Khalifa and the 450-meter Greenland Square Zifeng Tower in Nanjing, China.
They started off by chatting about sustainability:
Marshall Strabala: I think sustainability is using the least amount of energy possible over a given time. Buildings are machines that last 50 to 100 years. So our mantra is try to make every building better performing than the last. It’s an incremental problem. We’re not going to find a golden pill that’s going to solve everything.
Bentley: Is it more difficult to be net-zero, or even “green” in any sense, with a building this size?
It’s actually much easier in a big building than in a small building. I think you can get closer to net-zero. A single-family home has five sides open to the elements, whereas a high-rise building is a collection of small cells that only have one facade to the environment. And we can right-size the mechanical system for a big building in a way we can’t for a small building.
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.
What about the notch going up the side, the v-shaped cut along the building’s facade?
This is called a strake. Some engineer in Europe figured this out working on brick chimneys. They corbelled like a little tiny staircase around the chimney because the wind would blow it over otherwise. But if they had this spiraling step going up, the wind wouldn’t blow over the chimney. It would create what’s called disorganized vortex shedding. So this notch is called the V-strake—it makes it asymmetrical no matter which way the wind’s going. And we actually put an LED screen going all the way up it.
There was an aesthetic component, there was a structural component, and there was a functional component. The more twist, the less load, but it sort of plateaued—the more twist the busier it became when you looked up.
What place does the building occupy in Shanghai’s skyline?
Jin Mao is China’s past—a stainless steel pagoda—the Shanghai World Financial Center is China’s present, which is accepting foreign investment. It’s a Japanese developer. So our building is about the future of China—something that’s more transparent. This idea of seeing from one skin into the next—China is now opening up to the world, and what goes on in China is very visible to the world.
