Talk about lofty ideas. Chicago-based Shankar Nair, senior vice president at exp US Services, and former chairman at the Council on Tall Buildings and Urban Habitat, has spent his career looking up—that is, working as a structural engineer, researcher, author, and lecturer with an expertise in skyscrapers and, in recent years, super skyscrapers. As towering buildings like Dubai’s Burj Khalifa keep climbing toward the sky, Gwendolyn Purdom caught up with Nair to talk about where architecture has left to go if it turns out the sky’s not the limit after all.
Gwendolyn Purdom: How would you say skyscraper design specifically has changed in your more than 40 years in this field?
Shankar Nair: In the 60s and 70s, any building more than about 30 stories was a very big deal. Now, buildings up to 60 to 70 are quite routine. In fact, it used to be that the structural engineer was the central player in the design of skyscrapers because getting the building to stand up at that height was something that was fairly difficult with the technology of the time. It’s not that the technology didn’t exist, it’s just that it hadn’t been done very much. Now anything the architect and the owner want to do, we can make it work.
You have given lectures on findings you’ve calculated on what is possible, though not necessarily plausible, in skyscraper design and construction. Tell me a little about that and how that research came about.
Research may be too strong a word for what I’ve done, but I have brought some analogies and I have enough experience in this area that I can make some fairly good predictions and projections. But I use that knowledge, and those silly, brief calculations, to find out how tall could we go in a building with today’s technology. That means, with today’s massive analysis and design, and today’s materials, and with enough space left inside for things other than the columns and walls, for the building to be useful.
So with all that, I was able to come up with some fairly approximate limits to how tall we could go in steel and concrete, again, using today’s materials, not some exotic material that no one has invented yet. And the different shapes: the building going straight up and down is the most challenging, because that puts the biggest loads on the base of the building. And then if it’s tapered, then we can go even taller. Because as you go up, the area that gets exposed to the wind gets to be less, which helps, and also the weight to be supported gets less as you go up because the floors are getting smaller. And with all that I found you can go several miles tall, in both steel and concrete. But again, this is with today’s technology.
But you’ve said that’s probably not plausible.
That is right for several reasons. One is, will there ever be a demand for something like that? I’ve found that a building at the limit of what can be done structurally would have some 60 billion square feet of floor area, and would cost much more than the GDP of this country. So, no one would want to put that investment in one building anytime soon, so there’s certainly not going to be a demand for it. And then, when I say that this kind of building is possible structurally, that doesn’t mean that it’s possible from other points of view. Getting in and out, evacuation, mechanical systems—you’d need pressurization providing air to people up there, of course, because this is up above the range that aircraft fly. All kinds of technologies get involved. So the point is the structure is not the limit. The structure is the simplest thing to design in something that tall.
It seems like buildings keep getting taller and taller. Where do you think the cut off would be and why?
Let us assume that we stay with our way of living, meaning people don’t spend their whole lives in a building. They go in and out every day, because they don’t live and work and shop and play and all that in the same building. They use a building only for one of those uses. That means at least once a day you have to go in and out. And, given that constraint, and given the fact that elevators cannot go faster than a certain speed, that’s going to limit height to not much taller than where we are today. A few years ago, I thought the limit might have been well below Burj Khalifa, I thought it would have been around 2000 feet, but a building like Burj stretches the limit. Because, for one thing, it is so sharply tapered. There’s so little space at the top that the elevator demand becomes much less.
Now if it went straight up and down, so that whatever the size was at the base carried that all the way up to the 2,600 feet or so that that building is, then to serve all that space you would need a huge amount of elevator capacity. The building would be pretty much full of elevators which wouldn’t make sense. And, in fact, in these large buildings a large part of the top is both very skinny and often unoccupied, it might be just decorative. The other limit right now I would say is usefulness.
How did these calculations come about?
I got interested in this when I was chairman of the Council on Tall Buildings in 1997 to 2001. In fact, my term ended just before 9/11. But one of the questions people asked the chairman of the council was how tall can buildings go. So, I did some numbers then and I’ve kept them updated over the years.
What do you think fascinates people so much about supertall skyscrapers?
It’s just the idea of size and height. People like records, which can be good and bad. And people like to make a statement—owners, designers, and maybe even countries. There was a time when some people and companies in the U.S. tried to show their power and strength by building tall. Like the Sears Tower had the company’s name on it when it was the tallest in the world. But then, in the 1970s and 80s, the style here changed where the companies were no longer making big statements like that. They wanted to show that they treaded more lightly on the earth, and they weren’t that oppressive. So, for instance, Sears moved into the suburbs into low-rise buildings. And so that’s been the passing in the U.S. In Asia, on the other hand, they are where we might have been a generation ago, where some of the newly developing countries there still using their ability to build very tall skyscrapers as a calling card. They have arrived.
Once we do reach this height limit, how do you think skyscrapers will evolve? How will they out-do each other when they can’t go higher?
They might try to get greener. In the U.S., we don’t make any serious effort, for instance, towards having tall buildings be naturally ventilated. And in Europe, there are some tall buildings that are naturally ventilated for at least part of the year. I can see more progress in that direction, toward being more environmentally friendly, and more livable. And the limits that I talked about of around 3,000 feet, again, that assumes that each building is stand-alone. If you had a whole cluster of buildings with connections at different levels and so on, then the limit gets a little higher, as you wouldn’t have to come all the way to the ground everyday. You might live on the 200th floor and work on the 200th floor of a different building and go directly across from one to the other.