John Ochsendorf is a professor at the Massachusetts Institute of Technology whose work is devoted to understanding buildings of the past. An expert in masonry vaulting, he’s made a career of studying a style of construction that began millennia ago and practically disappeared with the Industrial Revolution.
I met Ochsendorf in a nondescript lab on campus where a model of Rome’s Pantheon rested on a table. “I think the Pantheon is probably the greatest building of all time,” he says, and he hopes to use the model to demonstrate that the real building is stable enough as it is—even though it’s weathered and cracked—without the need for modern-day interventions like steel reinforcing.
Ochsendorf, a MacArthur “Genius” Fellow, isn’t entirely comfortable in the spotlight; he says he’d rather ask me questions than talk about himself. His humility stems from his upbringing in a small town in West Virginia, where he was raised in a household with no TV and shelves of books, surrounded by artisans who built their own houses, fiddles, and banjos.
While so many scientists and engineers want to talk about the future, Ochsendorf advocates looking back. It’s not that he’s nostalgic about ancient builders. Rather, he says, “I’m in awe. I think they accomplished things that we would struggle to accomplish today.”
In conversation, Ochsendorf is eloquent and passionate. Our talk ranged from his view that great engineering should be viewed with the same reverence as art, to his conviction that today’s engineers are subjecting ancient structures to needless fixes. As we spoke it became clear he is bent on changing the status quo.
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Explain what this model is behind you.
Yes, this is a 3D-printed model of the Pantheon. I think the Pantheon is probably the greatest building of all time. It was an incredible leap forward at the time in construction, and the clear span on the interior wasn’t surpassed for around 19 centuries, so this was an incredible achievement in construction in its day. There’s an open question today about how safe the Pantheon is, particularly with earthquakes. So here, we’ve made the world’s first 3D-printed structural model of the Pantheon. This is a 1:100 scale model, which allows us to study the collapse conditions and to really estimate the limits of stability so that we can have greater confidence in the safety of the Pantheon. It’s been there for 2,000 years; we don’t think it’s going anywhere but we want to be able to prove it.
What’s the difference between a great ancient building and a modern one?
Well, traditional buildings and stone and brick and masonry, they stand because of their geometry; and the way builders conceived them was really through their geometry. When we design structures today we really rely on the strength of the material to a huge extent. So when we design structures of steel or reinforced concrete, we’re working the material much, much harder; so we’re stressing it up to much closer to its safety limits.
Old masonry buildings are stressed very low, and so the fundamental issue is that we had knowledge accumulated over centuries, or even millennia, which with the Industrial Revolution was essentially thrown out and we don’t really build like that anymore. Engineers are taught today in universities that there are really two dominant materials—steel and concrete—and so when they come to an old structure, too often we’re trying to make old structures conform to the theories that we learned for steel and concrete; whereas it’s more useful generally to think of them as problems of stability and geometry, because the stresses in these monuments are very, very low. At root, the fundamental issue is that we’ve lost centuries of knowledge, which has been replaced by other knowledge about how to build in steel and concrete. But today’s knowledge doesn’t necessarily map easily onto those older structures. And if we try to make them conform to our theories, it’s very easy to say that these older structures don’t work. It’s a curious concept for an engineer to come along to a building that’s been standing for 500 years and to say this building is not safe.
What’s wrong with strengthening a historical building with steel beams?
We could put a bunch of steel in and make an old structure behave in a new way, and in fact we do it all the time. Engineers do it all the time. But I would argue that that’s not our role as engineers working in the context of preservation, and that we diminish the work of engineering if we change its behavior. So as much as possible, we try to remain true to the original constructive intent and that means that an arch made out of bricks should work as an arch made out of bricks—it shouldn’t have carbon fiber or epoxy hidden inside of it with bricks glued on to the outside of it, right? And obviously that’s a philosophy of preservation and people can have different philosophies, but what I most want is for us to have a debate about what is appropriate for an engineer to do when approaching a structure that’s more than a century old and where we have an obligation to think beyond our own lifetimes when we intervene.
Why do you think engineers are so quick to intervene in historical buildings?
There are a couple of things. I think one is that in engineering education today we’re not really taught about history. We’re only looking forward and so we have a very progressivist view and almost, a progress ideology of engineering, so something old doesn’t inherently have value to us as a profession. Something new, something hi-tech has value. That’s part of it.
But a major part of it is that the motivators to intervene are very strong and one is fear. We’re liable for public safety and if a structure falls down and people get hurt, we have a responsibility. So that is a driver to intervene. And there are other drivers, like you make more money if you do a big intervention than if you don’t do anything at all. And another driver is you think it stands up but you can’t really prove it with a calculation because you’ve never really learned how to calculate a masonry dome for example, and therefore it’s easier to calculate if you add steel to it because then it conforms to your calculation methods that you’re comfortable with. And so, all of these drivers make it very easy for engineers to say we’d better add some steel. Not adding steel or not intervening is a really difficult thing to do. You have to have confidence in the structure; you have to have confidence in the calculations; you have to have the ability to say I’ve seen that crack, it doesn’t worry me—I think the building is safe. And so there are many things that drive us to intervene but the problem with a lot of interventions is that they may last for a few decades only, whereas when we’re dealing with a monument that’s been around for centuries we have an obligation to think in terms of centuries.
So should a Roman temple actually be analyzed differently than, say, a steel and concrete office tower?
Yes. We have a major problem right now: If you take the computer software that’s on the desk of every structural engineer and you apply that to an old masonry structure—so a Roman vault, a Roman dome, or a brick arch from 1930—the software says it doesn’t stand up. It says it’s not safe and it needs to be strengthened. I have a very simple philosophy that is, if the structure’s been standing for decades or centuries or millennia and you’re computer says the structure does not stand up, it’s not the structure that’s wrong—it’s the software that’s wrong. What’s required is the development of better software, a better understanding of the particular mechanics of these older structures, and the easiest thing in the world is to arrive at an old structure and to say it’s not safe, it needs steel.
Why should engineering students think about history?
We have a problem in engineering: that it’s difficult for us to name our mentors or heroes or people we look up to. It’s really hard to imagine someone studying literature or music and not being able to name the great composers or the great writers of the past. It’s almost inconceivable that someone would try to compose music without studying the great composers of the past and yet, that’s what we’re asking our engineers to do because we have this notion that we’re at the pinnacle of all time and that most of the great knowledge of what it means to be a successful engineer can be captured in building codes and in equations. There’s so much more to engineering than that—both the individuals as well as the objects they produced. So the Pantheon is like a great work of Mozart, and we should study it from every different perspective so that we can try to create more Mozarts in the future.
What are the best reasons to study historical buildings?
As an undergraduate, I had an epiphany when I went on an archeological dig. I realized I had been missing more cultural aspects of the world around me and what people had achieved, so I began to study anthropology and archeology together with structural engineering. I think it’s really critically important that we have various perspectives on any field, so in my case it was structural engineering combined with archeology.
Having said that, having a historical view is really important today. If we think about the United States in the 19th century, most of the cities were being built and most of the work of engineers was working on new structures. About half of all spending on construction today in the U.S. is on existing infrastructure, existing structures, and so you could argue that in some ways our mission has changed and our mission now is to both maintain what we’ve inherited as well as to build new. That means the education of the engineer needs to evolve to address that reality—in many cases now we’re talking about trying to get longer life out of existing bridges or existing subway tunnels and that requires a different set of knowledge and a different set of skills than only designing new structures.
How did engineers in Rome figure out how to build something like the Pantheon?
The short answer is that we don’t know. We don’t have a document that says, “this is exactly how we calculated the width of buttresses required to support a Roman arch.” What we can find are relationships—geometrical relationships—that are encoded within the buildings, which show some of the rules that the builders had. And as an example, many Roman domes have a supporting wall which is about one-seventh of the span of the dome, and that meant that the builders through experimental means or working with models—they may have even built small scale models like this—were able to devise ratios and proportions that were stable. And those ratios and proportions are largely independent of scale in traditional buildings because as you get larger the stresses get bigger but we’re still an order of magnitude below the crushing stress of the material, even in the largest buildings. That meant that using scale geometry and proportions was appropriate and that if you made a building twice as big, the stresses would go up significantly, but they were still far below the failure stress of the material. So often, Roman builders and builders in the Gothic period were looking at example or precedent structures, which were built a generation before, a few years before—taking the same principles and proportions and applying them at a different scale. And this is why I say that they were not … It wasn’t trial and error. You know, they were carefully studying the greatest works of the past. There were encoded ratios and proportions that were passed down through the generations, and unfortunately, in the industrial revolution, a lot of this knowledge was lost. In particular, we don’t often build arches or domes today. It’s very common if you tried to build a structure in steel or brick today that the building code and the engineers involved will insist that it requires steel.
Architecture is viewed as an art, while engineering a trade. Does that do engineering a disservice?
You know when we think of great engineering, the great works of engineering are also great works of art. So if you look at John Roebling’s Brooklyn Bridge or the Eiffel Tower, or the Pantheon, these are masterpieces. I was very fortunate to study with an exceptional engineering professor at Princeton named David Billington who devoted his life to really celebrating exceptional engineering, identifying the masters of structural engineering, and studying their individual works like we do in art or the humanities. So why is the Eiffel Tower great? Why is the Brooklyn Bridge great? For Billington, the Industrial Revolution marked the beginning of engineering. So his studies focused primarily on works from the Industrial Revolution.
I personally believe that the great buildings of the pre-Industrial era are also engineering and even though they weren’t calculating the projects in quite the same way, they’re still works of engineering that deserve to be studied. In order to become better engineers and in order to deliver better buildings, better bridges for society, we as engineers need to have the ability to debate the merits of different solutions. I’ve had the benefit of teaching not only engineers, but also architects; and in architecture, you could argue the solutions are often dramatically under-constrained so it’s often treated more like an art with an open exploration of ideas.
In engineering, conversely, I would say our solutions are too often over-constrained. In engineering education, for years and years and years we’re often given problems that have one answer. I’d like to be able to create engineers who, when you give them a blank sheet of paper, or you give them a view of a mountain valley and say design a bridge, grab a pencil and start sketching 10 different ideas, because they’re founts of creativity.
When we are not seen as creative designers, I think our role in society is diminished; when we are reduced to crunching numbers, you know, technocrats who make other people’s visions real. And of course, that’s not what engineering is! The greatest tradition of engineering is just as rich as literature and music and architecture. So I see engineering as part of a centuries-long continuum where we’re not at the peak of a mountain; we’re at the side of a river. We can look backward at where the river came from and we can look forward at where the river is going but there’s a great benefit to doing both—to looking forward and looking backward simultaneously; which is what the great writers, the great composers, and the great designers are doing.
So I’m adamant that engineering is an art and perhaps it’s even more of an art than a science. Our education often doesn’t reflect that but I’m excited about the future of engineering in part because we have such a rich past. If our future is remotely as rich as our past, you know, it’s going to be good to be an engineer in the 21st century.
You did research on woven suspension bridges in Peru. What makes them special?
You know, I first really discovered and fell in love with the nexus of engineering and archeology working in Peru and studying incredible suspension bridges that were built during the Inca period, that really were essential to creating the Inca empire. They stitched together the Inca road system; they spanned very deep and difficult canyons all throughout the Andes Mountains.
These bridges are the exact opposite of the Roman arch and when the Spanish arrived in the 16th century in what is now Peru, they were completely terrified by the suspension bridges and I’ve argued that in part, it was because the technology was unknown. They came from a Roman tradition of construction. They had a certain idea of what a bridge should be and the Inca bridges were a completely different worldview but these Inca suspension bridges of lightweight fibers woven together to span very long distances were a really appropriate solution to that site, and in many cases, the Inca period suspension bridges survived for several centuries after the collapse of the Inca empire. In some of the most important examples, the Spanish and the colonial era tried to build Roman scale arches on the site of the Inca bridges and failed. Essentially the Inca solutions weren’t surpassed until the Industrial Revolution.
Let’s say you have all the resources you need to build your dream building. What does it look like?
First of all, I’m a little unusual in that my dream building would be an existing building that needs to be renovated and they exist all over the world. They exist all over the United States. We have beautiful old buildings that have been neglected and are being run down and we’re losing them. In fact, one of the best things you can do from a cultural and economic standpoint, but also an environmental standpoint, is to refurbish an older building. So I’m sorry, but my dream house is a house that already exists, but [that] needs some TLC maybe to be fixed up! But it’s true that I would like to live in a building with vaults or arches, and that there’s something very, very special about an arch or a vault. The longevity, the simplicity. Leonardo da Vinci said that an arch is nothing more than two weaknesses that make a whole; and there’s an Arab proverb that says that the arch never sleeps.
What would you be if you weren’t a scientist?
Gosh. You know, I always wanted to be a writer when I was kid. I thought I’d be a writer. And I even thought about journalism because you’re always learning constantly; and so I remember as a child wanting to write but at the same time, enjoying building things and working with my hands and so I think probably as an engineering professor I found the right mix, because in academia they say, “Publish or publish!” So I’m writing all the time. I’m also building things.
I also didn’t get to travel much when I was a child and so I always had a dream that I would one day get to travel the world and see great sights, great buildings; learn about different cultures. And I always had a dream that maybe I could live a life where I would get a telephone call that said, “We really need you to come to Egypt because there’s a structure that we’re not sure how it’s standing up,” or “We need your help!”
And so if I were to relive my life 10,000 times over again I don’t think I would be able to hit the one that I’ve hit in this lifetime but it’s been really, really fun to try to combine a love of engineering with a love for the humanities and culture, and I think there’s great value for both sides of what Charles Percy Snow termed the two cultures. So yes, to be culturally literate we should know Shakespeare; but we should also know Hooke’s Law, and thermodynamics, and that engineering has much to offer the world and that too often, we are not sharing the beauty of engineering and science with the world. We should do that more.
Courtney Humphries is a writer in Boston who covers science, medicine, architecture, and urban planning.