Carbon Fiber Future

Can a prototype skyscraper made entirely of composite materials survive the post-9/11 mania for safety?

In October of last year Peter Testa—a 50-year-old architect who has worked for Alvaro Siza, taught at MIT and Columbia, and now runs a small firm in Southern California—headed back east to take part in an invitation-only conference in Cambridge, Massachusetts. Sponsored by Cap Gemini Ernst & Young’s Center for Business Innovation, the two-day gathering brought together 30 corporate leaders, academics, and scientists from around the country. Their charge, as the no-nonsense conference materials put it, was to “sense, capture, and communicate signals that point to imminent change and to examine nascent shifts that will come to transform all aspects of economic activity.”

It seemed a perfect forum—freewheeling, speculative, and full of very smart people—for Testa to talk about a project that first seized his imagination about three years ago and has not let go since. The project is a prototype 40-story skyscraper made entirely of composite materials, mostly carbon fiber. Such man-made composites, which also include better-known materials like fiberglass and Kevlar, are increasingly used in industry and for consumer goods—in everything from airplane fuselages to tennis rackets—because they are strong, lightweight, and easily molded into an almost endless variety of shapes. They’re also slowly making their way into highway bridges and other civil-engineering projects.

Although the materials seem well suited for architecture—in tension, carbon fiber is five times stronger than steel—their use in buildings has been rare. Testa, though, is convinced that composites will radically transform architecture during the next decade or two. His carbon skyscraper, which he likes to describe as a “woven building,” is designed to be not just less muscle-bound than the skyscrapers in which Americans work today but also more beautiful, environmentally friendly, and cheap to build.

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At the conference Testa gave a short presentation that included renderings of the tower. He told the group about the preliminary computer testing he’s done of the building’s structure and materials with help from the New York office of the engineering firm Arup & Partners and from CTEK, a Santa Ana, California-based prototyping company. When Testa turned to the audience he was expecting to field general questions about the design and properties of the materials. He got something else.

“Everybody started asking, ‘What if a plane flies into it?’” Testa recalls. “At first I was resistant to frame the project entirely relative to the World Trade Center. After all, we began it long before September 11, and here we were more than a year after. But people really thought I should be ready to explain what would happen in that kind of situation. And the more I thought about that, the more I agreed.”

Before his trip to Cambridge Testa wasn’t exactly naïve about the profound changes the September 11 attacks had brought about in the way Americans think about skyscrapers. He understood that he’d chosen an odd time to be peddling a revolutionary new design for a tall building. But he never guessed that a group of specialists gathered specifically for their talent in looking boldly forward would focus on the collapse of the Twin Towers at the expense, it seemed, of all other issues.

The comments also reminded Testa of a more general trend he found disturbing. “There’s been a real backlash,” he argues, against new approaches to structural engineering since September 11. “Everybody in the press seems to be calling for very strong and robust-looking construction, like the Empire State Building, with tight structural grids and thick, heavy columns. I haven’t read anything to suggest that maybe what we need instead is new materials that will behave differently and better.”

All of which leaves Testa in an odd position. The good news for him is that during the last year and a half the public has developed strong, even passionate, ideas about how skyscrapers ought to look in the future. The bad news is that Testa’s open and airy design is precisely not the sort of thing they have in mind.

Testa’s carbon tower is the product of ongoing research in computer-aided engineering and material science; as a result, its design seems to change on a weekly basis. But the basic form is not especially complex. Imagine, first of all, a cylindrical building 40 stories high. Then picture that cylinder strung together by 40 carbon-fiber strands, about 1 inch wide and nearly 650 feet long, that are arrayed in a helicoidal, or crosshatch, pattern. Filling in the structure between floors is an advanced glass substitute (Testa’s current favorite is called ETFE, a kind of transparent foil). A pair of ramps on the exterior of the building offers circulation and further stabilizes the structure.

That, in simplified form, is the carbon tower. Perhaps the most striking thing about it is that every major element in the building, including the floors and the exterior ramps, is made of some kind of composite material—there is no steel, concrete (apart from the foundations), or conventional glass. Yet just as important is the structural use of continuous carbon strands, which are woven to form a structure that distributes its loads over its entire surface. (Most contemporary skyscrapers use steel or concrete, or both, in compression.) Taken together, the building’s innovations open up the potential for what Testa calls a new “organic minimalist aesthetic”—a building whose surface and structure are one and the same.

The 24 strands will be fixed into shape by something called a robotic pultrusion machine, which Testa envisions climbing up the structure like a spider and weaving the strands on the side of the tower as it’s built. “You just bring a bundle of fibers and some plastic to the site, and then you manufacture the building right there,” he says. “Each of the strands will have its own machine.”

That method would offer obvious energy-saving advantages over traditional construction techniques, but there is another dramatic benefit as well. As Testa envisions it, this 40-story skyscraper won’t need any vertical structural elements: no columns between floors, no central core. Air circulation would be handled through a pair of continuous open cylinders, or “virtual ducts,” that run from the top of the building to the bottom and operate on the kind of displacement ventilation system that is already appearing in some European buildings. Three groups of elevators are distributed throughout the floor plan, instead of being crowded together at the core.

The tower aims to reconfigure all three central elements of contemporary skyscraper design: structure, circulation, and heating-and-cooling systems. “It’s time we faced the fact that skyscrapers don’t work well from almost any vantage point,” Testa says. “They don’t work well from the standpoint of the organization of the workplace, urbanistically, or environmentally.” Indeed the combination of the growing sustainable-design movement and the World Trade Center’s collapse has made skyscrapers a target for double-edged critique: Not only do they treat the earth horribly on a day-to-day basis, but they’re not reliable for humans in a structural crisis, either.

At the same time there’s been a realization, underscored by the way people have developed a nostalgia for the architecture of the Twin Towers, that Americans will continue to build towers that stretch the limits of engineering and imagination. That kind of ambition seems deeply rooted in the national psyche. As Matthew Dockery wrote in City Journal last fall, “In a culture whose creed is Liberty through Capital, the speculative office building is the Cathedral, whose height is the measure of its sanctity. The Twin Towers were to us what the Pyramids were to the Pharaohs: testaments of civilization designed to challenge the limits of time and space.”

The alternative skyscraper that Testa has developed is part of a movement trying to bridge that divide—to acknowledge the indestructible allure of tall buildings while harnessing new technologies to make those buildings more environmentally responsible. The movement is having a coming-out party of sorts this year with an exhibition at the National Building Museum, in Washington, called Big and Green: Toward Sustainable Architecture in the 21st Century. Running through June 22, it includes only projects that are both green and large-scale. The carbon tower is among its featured designs.

Testa is adamant that his tower can be built within five to ten years. In his push toward real-world feasibility, he’s relying heavily on an association with his two institutional collaborators. Arup is a giant firm whose status in the design world is evident by the fact that it is working with four of the six teams of finalists on the redesign of Ground Zero. CTEK, which Testa describes as a “heterogeneous workshop,” is best known for building a custom futuristic Lexus for Steven Spielberg’s film Minority Report and the curving glass panels of Frank Gehry’s Condé Nast cafeteria, in New York.

At Arup, Testa’s carbon tower has caught the eye of structural engineer Markus Schulte. In addition to his work for clients including Richard Meier and David Childs, Schulte spends about one day a week, as he puts it, “trying to be a facilitator in making architectural dreams a reality.” For example, he helped Diller + Scofidio fine-tune its winning entry in a much publicized competition to design a building for the Eyebeam Atelier, in Manhattan (see “Measuring the Competion,” November 2002, p. 96).

This sort of pro-bono research-and-development work is rare in the industry. “One of the big dilemmas we’re facing is how younger or smaller firms get access to advanced engineering,” Testa says. “How do you bridge that gap without huge resources? Often the smaller practices in architecture have the benefit of really advanced computing, but there’s no engineering and material science to back them up.” He adds, “Somehow engineers are not finding their way into these kinds of associations with architects, especially not in this country. And I don’t think architecture is going to advance without them.” Isn’t that what major research universities, like the ones where he used to teach, are for? “Well, that’s exactly what I tried to do at MIT,” Testa says, “and I found it to be very difficult, if not impossible, to create a kind of interdisciplinary environment where design is at the center.”

Schulte says he’s impressed with the prospects for the carbon tower so far. Tests run at Arup have suggested, among other findings, that the building would use about 50 percent less energy for heating and cooling than most skyscrapers of its size. And Schulte is impatient with any suggestion that this is a pie-in-the-sky project. “I don’t like the idea of it as a sort of experiment that Peter works on for a while and then puts on his shelf,” he says. “For me as an engineer that’s not good enough.” He is connected to the project, he stresses, primarily because he thinks it is buildable.

Howard Decker, chief curator at the National Building Museum and an organizer of the Big and Green exhibition, thinks the building may change the way green-building advocates look at cities. Urban settings have long prompted ambivalence among environmentalists, because while city-dwellers make efficient use of infrastructure and transportation networks, they also put tremendous strains on resources. Tall buildings have been among the worst offenders in that regard. “But once we figure out how to build a skyscraper sustainably,” Decker says, “then urban density begins to look more attractive than ever.”

Still, a lot of things would have to happen for even a single example of the tower to be built in the next decade. The biggest hurdle is the cost of carbon fiber and its resin coating, which continues to be prohibitively high compared to steel or concrete. Then there’s the issue of building codes for skyscrapers, which are tightening around the country after the World Trade Center collapse. There’s also the question of whether using carbon fiber at this scale will be safe for the people who use the building every day. (In the past materials that were heralded as breakthroughs—like asbestos—have sometimes turned out to be dangerous to our health.) And even if all of those barriers are somehow cleared, Testa will need to find a risk-taking first client, suggests Henry Petroski, a civil-engineering professor at Duke University. “It’s not surprising to see substantial research in this direction in the wake of 9/11. The question is how these materials will behave in the long run at this scale, and there you always have reason to be wary.” Even a force as seemingly innocent as sunshine, Petroski says, “can have a deleterious effect on some of the plastics that are used in composites and cause them to wear down over time.”

Another concern is fireproofing. “Carbon-fiber materials are not exactly known for being able to carry high temperatures,” says Leslie Robertson, who was lead structural engineer on the World Trade Center and is now working on a design for a tower in Shanghai that would be the world’s tallest. But Robertson also suggests that the public still might be open to a new kind of skyscraper. While building department officials will be a harder sell, he says, “The man on the street doesn’t give a damn what the tower is made of, as long as he can see it standing up and it’s comfortable to work in. He already drives a car made of carbon fibers, rides in airplanes using them. Why should an office tower be any different?”

Even if the tower can’t be built, or if it evolves into some less radical form, it holds the potential to be an important step in twenty-first-century architecture. Testa, who for a while held a rather inflexible attitude about the tower’s development, has a new way of thinking after his experience in Cambridge. First of all, he’s realized that he may have to make changes in the design even if they’re not necessary structurally. “I’ve now come to feel, okay, we’ll change the design, we’ll build some redundancies in. We’ll put some stairs on the inside, even if I don’t think we need them, to help people’s psychological well-being. There’s no reason to be absolutist about it.”

Testa also appreciates the symbolic and rhetorical value of his design more than he used to. “It’s kind of a critical passage we’re going through right now. The challenge for us as designers is to be ready with clear ways to explain the issues and options when it comes to tall buildings. Architects and engineers need to work together to step up with information, with ways to make new technology tangible and accessible.” Skyscraper design, Testa says, is now “highly contested terrain in this culture. But it becomes a question of how we channel that energy—whether we can push the discussion toward innovation, and not toward retrenchment.”

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