Mass Amoring of America
When Ken Hays, former executive vice president of MasonryArts in Bessemer, Ala., switched on the news the morning of Sept. 11, 2001, he was faced with two pieces of information that would’ve been hard enough to process individually. The United States had been the victim of a terrorist attack, and one of those attacks had zeroed-in on his company’s highest profile site: the Pentagon.
For two years, MasonryArts had been working on a $13 million contract to replace the Pentagon’s windows with blast-resistant glass. Sept. 11 put the company’s protective windows to the test and accelerated a worldwide race to “harden” thousands of government and private-sector buildings against future attacks, a move that began with the bombing of the Alfred P. Murrah Building in Oklahoma City in 1995.
Several U.S. agencies have, over the years, collectively developed strict guidelines for glass and other building materials designed to minimize loss of life in the event of an attack (see sidebar). Today, glaziers and glass manufacturers are dealing with challenges and learning the tricks that come with the mass armoring of America.
The Pentagon and beyond
Shortly after American Airlines Flight 77 crashed into the west side of the Pentagon, Hays managed to track down his workers, who had been assigned to the Defense Department project, by phone from his Alabama home. Earlier that morning they headed out to pick up supplies, which saved their lives. The MasonryArts project was part of a sweeping, long-term renovation of the headquarters of the U.S. Department of Defense that began in the 1990s and is expected to be completed in 2010.
A few days after the attack, Hays arrived at the disaster site to find that a few feet above the point of impact, the blast-mitigation windows had held fast.
“You’ve got a 300,000-pound plane flying 600 miles an hour; you’ve got to believe something worked,” says Hays, now vice-president of pre-construction for Physical Security LLC in Bessemer, the glazing unit spun off by MasonryArts in January 2006. The non-reinforced windows about 100 feet away from the point of impact were obliterated.
In any bomb attack, about 75 percent of injuries are attributable to flying glass from windows, according to a 2005 report from the National Institute of Building Sciences in Washington, D.C. Glass shattered in hundreds of buildings near the Alfred P. Murrah Federal Building in Oklahoma City. Blast-mitigation glaziers and manufacturers such as Hays’ company utilize different methods to neutralize the amount and trajectory of airborne shards, from transparent polyester films that hold shattered window glass together to systems that back up the window’s framing system with steel cables or rods.
Hays declines to share the specifications of the Pentagon’s blast-mitigation glass, but the Economic Development Partnership of Alabama in 2002 reported that the company had installed more than three-quarters of a million pounds of reinforcing steel that the windows fit into, and that the windows themselves were mounted into the steel matrix and not into the limestone walls of the Pentagon itself.
By Sept. 11, 2002, MasonryArts had completed its repairs on the damaged area. Since then, the company has completed the original renovations in Wedges 2 and 3 of the Pentagon, and Physical Security is continuing that work in Wedge 4 now, Hays says. Work on Wedge 5 will probably start late next year.
In addition to the Pentagon, Hays’ company has designed and manufactured blast-mitigation glass for the federal campus that replaced the Murrah Building in Oklahoma. Presently, protective glazing makes up about 30 percent of Physical Security’s work, Hays says, but that changes from year to year.
One of the biggest challenges in protective-glass installation is hardening buildings against attack without making them look as visually unappealing as fallout shelters, Hays says. “Buildings, not bunkers,” is an aphorism his company uses to express its aim.
“More and more architects are learning how to produce a project that is architecturally pleasing and blast-resistant,” he says. “It’s been a slow process because of the lack of knowledge in blast-resistance, but it’s getting better.”
Buildings not bunkers
What makes this particularly challenging is that at least half of the projects a glazier is likely to encounter involve courthouses and other federal buildings that also must retain their looks as part of state or national historical-preservation requirements.
“With buildings of the ’50s and ’60s, you can take a standard [glass] shape and apply it to that building’s window and not be worried about it being of a little larger dimension,” says Rick Jones, blast-mitigation manager at Graham Architectural Products in York, Pa. “But with buildings that are historic, you have to match [the windows] exactly.”
About 70 percent of his company’s blast-mitigation jobs fall into the historic category, Jones estimates. In August, the company tackled 43 jobs for the Defense Department and six or seven for GSA.
Often these assignments require some good old-fashioned ingenuity, especially on military bases, where many of the buildings are both historically significant and in need of “hardening” against potential attacks. One such location is the Fort Sam Houston U.S. Army base in San Antonio.
First staffed by U.S. troops who had served at the Alamo in 1876, it was the birthplace of American military aviation in 1910, and has grown from a 92-acre post to a nearly 3,000-acre base. In August, Graham Architectural Products was completing blast-window installations on one of its many buildings.
“Some of these buildings we’re working on were built in the late 1800s or early 1900s, and most are in the national historic registry,” Jones says. Case in point is the most recent focus of the company’s efforts, Building 2791, which required Jones and his crew to match the window sightlines exactly with blast-mitigation glass. “We had to take every piece apart and replicate its exact dimensions,” Jones says.
The problem arises from the divided-lite style of window found in many older buildings, with individual lites glazed into small square mullions, he explains. “You can’t do that on a blast window because the smaller the glass, the higher the [blast] load on it,” Jones says. Add to that the fact that a smaller piece of glass is more rigid and therefore easier to break, and that there usually isn’t enough bite to hold the thicker blast-mitigation product in place, and the challenge becomes clear.
To replicate the look of the older windows, Graham Architectural Products uses an applied mullion on both sides of a window-size, blast-resistant unit.
However, when it comes to safeguarding people’s lives, you can never compromise performance for aesthetics, Jones says.
After Sept. 11, 2001
Matching protective windows to historic architecture is not the only challenge facing glaziers today. Fortunately, the protective-glazing industry has learned a great deal since the terrorist attacks in 2001.
One of the biggest changes is the availability of software that offers dynamic analysis for the engineering of protective framing systems, says John Myers, technical director at Harmon Inc. in Glen Burnie, Md. In the Washington, D.C., metropolitan area, in terms of dollars, at least 25 percent of Harmon’s business is in blast-mitigation.
Before software such as AT-Blast, an application developed by Applied Research Associates Inc. in Albuquerque that estimates blast loads during an explosion, calculations often were based on an equivalent static load on the entire window, Myers says. “It’s really not a linear analysis. If you look at the dynamics of the framing system, it’s not necessarily going to be the case.
“The software gives you a more accurate design tool so you don’t over-design the elements of a framing system,” Myers says. “Otherwise, the framing ends up being designed for a higher load than your glass. And that ends up increasing the cost of the framing system and anchorage to the structure.”
Viracon Inc. in Owatonna, Minn., supplies Harmon with most of the glass used for this type of work. However, many companies that manufacture protective glass are insisting on installing it themselves.
Graham Architectural Products does all of the drawings, calculations, cutting and prefabrication work before installation, Jones says. “It does no good for a manufacturer to sell windows and then not have them installed properly. The last thing we want to happen is that, if there’s an event, the window becomes a projectile,” Jones says. He admits glaziers can install the special window systems correctly, but says, “I see quite a bit putting in glass with No. 12 sheet metal screws.”
Physical Security manufactures and installs most of its security glass as well. “The higher the glass load, the less forgiving the support systems,” Hays says.
Since Sept. 11, 2001, government and military sites aren’t the only facilities seeking protection. Private-sector building owners have been installing lower-level blast resistance, Myers says. “Largely it’s developers who are trying to attract clients who are interested in some level of security,” he says, particularly in the Washington, D.C., area.
Banks in New York and petrochemical companies in other large cities are also beefing up their protection, Jones says. In the latter industry’s case, this has less to do with guarding against attack from outside than safeguarding their employees from internal explosions and mishaps, he says.
Whatever his company’s products are used for, the blast-mitigation-glass professional’s responsibility doesn’t end when the invoice is paid, Myers says. Every calculation must be correct and every system must function perfectly. “It’s not just about selling a truckload of windows,” Jones says.