Architects had begun to worry about terrorist attacks on buildings well before September 11, 2001. Their concern dated from April 19, 1995, when a bomb hidden inside a rental truck exploded outside the Murrah Federal Building in Oklahoma City, blowing half of the nine-story structure into oblivion. It has been estimated that 80% of the 168 people who died weren't killed by the blast itself but by shards of glass or falling debris. That fact stirred a storm of controversy -- which in the years since has led to the adoption of building codes for federal structures that make them less vulnerable to collapse and that shrink the killing zone from an explosion.
The World Trade Center disaster delivered the same wakeup call to commercial builders. They're suddenly facing a variety of new guidelines -- though most of them aren't mandated -- for terrorist-resistant construction. In April, the National Institute for Occupational Safety & Health issued air-filtration recommendations aimed at protecting against chemical and biological attacks.
Most changes are driven more by fear than by law, however. "Almost every client out there is interested in this, because it's a concern of their tenants," says James McKenna, a senior vice-president at Turner Construction in New York, the nation's largest commercial builder.
MATERIAL ADVANCES. So great is the concern that many building owners don't mind the extra cost. That can amount to 5% of the outlay for a new building -- higher, in relative terms, for older buildings that are retrofitted, says Paul Williams, a principal who specializes in homeland security for hospitals at NBBJ in Columbus, Ohio, the world's fifth-largest architectural firm. That money goes for special filters; reinforced columns, windows, walls and floors; and landscaping that helps restrict access.
Today, every major architectural firm has a staff dedicated to such anti-terrorism measures. And many technology companies are gearing up to meet the rising demand for new equipment and materials that can help mitigate the terrorist threat.
Particular attention is being paid to protecting building occupants from flying glass. Last October, materials maker DuPont (DD) introduced SentryGlas Secure, which sandwiches a special polymer between two layers of glass. The polymer sticks to the glass so that it doesn't so easily fracture when hit by a blast: While the glass may break, SentryGlas will keep it in one piece (car windshields work the same way). The product has been tested by the State Diplomatic Security Service Dept. and proven to withstand blasts of up to 30 PSI (pounds of pressure per square inch), roughly equivalent to winds of more than 500 mph.
WINDOW CATCHERS. While this technology can keep broken glass from spraying all over, it doesn't eliminate the threat to human life: A blast could catapult an entire window into a room -- creating a huge projectile weighing several hundred pounds. The answer to that is so-called window-catcher technology from Composite Solutions, a privately held startup affiliated with the University of California in San Diego. Installed at several U.S. embassies abroad over the past six months and due to become commercially available this year, the system contains windows that are dislodged by bomb blasts.
The strongest of Composite's two systems -- to be used in first-story windows -- looks like a regular vertical shade. When a blast occurs, its reactive system automatically closes the shade, which is made of special carbon-based materials that are 15 times stronger than steel. If the window flies out of its frame, it's caught and simply collapses onto the floor, says Allan Mangold, Composite's director of business development.
The shade, which costs $30 per square foot and ultimately should come in a dozen colors, will withstand impacts of up to 400 PSI, he says. For windows less likely to be at a blast's epicenter, Composite sells special cords of the same material for $20 a square foot that run either horizontally or vertically behind the window (inside a room) to protect against shocks of up to 50 PSI.
WRAPPING COLUMNS. CSI has also developed a special system that helps keep bullets and debris from flying into a room through a wall. About 1/8-in. thick, it consists of the carbon fabric that's glued to a layer of Kevlar, the material used in bulletproof vests. This combination is both attached to the wall and anchored at the base. It's expensive -- $20 to $50 per square foot, depending on how many layers of it are used -- but it helps keep walls from collapsing. It can protect a room's occupants from blasts of more than 10,000 PSI, when wrapped six layers thick, says Mangold. He adds that the cost is about the same as for buttressing walls with a five-foot-thick concrete reinforced with steel.
Support columns of buildings can be strengthened with what looks deceptively like thick wallpaper, says John Crawford, president of Karagozian & Case, a structural engineering firm in Burbank, Calif. Bomb blasts can make concrete columns crack and crumble. But if the column is wrapped with three to five layers of the special carbon fabric, which is similar to the kind used in Composite's shades, it will retain its shape even if damaged. Crawford has done tests showing that a wrapped column can survive typical car-bomb blasts from as close as 10 to 20 feet. Such wraps cost about $4,000 a column, Crawford says.
More new materials are in the works: University of California at San Diego scientists are developing wraps made of special carbon nano-materials that will be more than 30 times tougher than steel, says Gill Hegemier, professor at the university's department of structural engineering in La Jolla, Calif. They're also working on a blast simulator, to be finished in 18 months, that will allow for testing of bomb impacts on buildings in a lab -- instead of at a special facility in New Mexico, he says. That should significantly speed up time to market for new terror-resistant building materials.
OUTSIDE SHOWERS. Architects are also altering entire building designs to account for terrorism-related emergencies. Today, every hospital emergency room has a decontamination area, equipped with showers, that's used to treat victims of chemical and biological accidents, says Williams of NBBJ. But the contamination can spread through the air. So in new hospitals, he now often extends the roof above the emergency room entrance to 50 feet or so. He puts electrical and water outlets at the outside wall so that victims can be decontaminated before coming into the hospital.
Better filters should eliminate other threats. Health-care products maker 3M (MMM) has developed a filter that captures 99.97% of particles of 0.3 microns and larger (anthrax spores are about 5 microns) more efficiently -- using less electricity while pumping more air through. Today, many building filters catch only 30% of such particles, and the cost of maintaining the devices is 50 cents per cubic foot of air pumped through per year.
Until now, maintaining higher-efficiency filters would have cost three times as much. But 3M's new product, due out in the second half of this year, should cost less in maintenance while allowing for up to a 50% reduction in fan energy use, says Cory Erickson, business development manager at 3M. Some versions of the filter have already been tested at the Fairview-University Medical Center in Minneapolis to protect transplant patients, whose immune systems are suppressed, from air-born fungus, says Andrew Streifel, a hospital environment specialist at the University of Minnesota, which is affiliated with the center.
SMALLER WINDOWS. Office-building owners are looking at other ways of making air more secure. Instead of installing air-intake systems 12 feet from street level, they're moving them closer to the eighth floor to make terrorist attacks less likely, says Chris Jahrling, a vice-president and director of homeland security at Turner Construction, which is erecting five buildings in New York City.
Builders are also taking other, commonsense steps: Instead of installing 15-foot storefront windows, they're increasingly opting for smaller panels reinforced with 4-inch aluminum rods in between the panels, says McKenna, of Turner. More bolting is used to secure the connections holding up the frame, and new buildings' columns are often reinforced with steel plates, he says. Turnstiles added at entrances also help elevate security.
Special landscaping can also help. As the Washington Monument grounds in the nation's capital are reconstructed over the next two years, the landscape will be layered to create a 400-foot-long wall that would stop approaching vehicles, says Kathleen John-Alder, an associate partner with Olin Partnership, the landscape architects in charge of the project. Reinforced benches -- which can stop a 5,000-pound car moving at slow speeds -- will be added in front of the White House, whose grounds are also expected to be redesigned.
NEW DEBATES. All these measures can be pricey, with the final tab depending on how far a building owner wants to go. "You can always take a risk factor and double or even quadruple it -- and double the building's cost," says James Ingo Freed, a partner at architecture firm Pei Cobb Freed & Partners, which built the U.S. Holocaust Memorial Museum in Washington. He jokes that the most secure building would have no windows -- "and be a tomb."
At the moment, it still isn't clear where to strike a balance. "Building owners aren't sure what to do," says Crawford. "The technology is really there, but the [threats] aren't defined." A prime example is fire safety. In the wake of the World Trade Center disaster, it's clear that buildings need to be more fire-resistant. But how much more so -- and how to achieve that -- is the subject of debates that are just beginning.
What to do likely will become clearer over the next two years, as governments at every level begin to tighten the rules for commercial construction, says Maria Armstrong, an associate at Bricker & Eckler, a construction-law practice in Columbus, Ohio. That's when innovation in new building techniques and materials could really start taking off. By Olga Kharif in Portland, Ore.