For nearly three months, Mike Biscotte, a Roanoke engineer, has focused on one main job: Analyze what happened to the Pentagon on Sept. 11 when Flight 77 slammed into it. He’s crawled all through the four-story, 35-foot-wide gash in the southwest wall, where the hijacked jetliner penetrated four of the building’s five concentric rings. His firm, Hayes, Seay, Mattern & Mattern, had nearly completed its work on a massive renovation and strengthening of the military headquarters. Biscotte’s mission: Determine which of the new design features were effective and which need to be improved.

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Although 189 people died in the terror attack, project engineers regard their handicraft with grim satisfaction. The loss of human life could have been far worse. Though hardly as tall as the World Trade Towers, the Pentagon is still the world’s largest office building. Its 6.5 million square feet make it the equivalent of three Empire State Buildings. The hardened military structure contained the damage to the immediate area of impact, in contrast to the twin civilian towers, which collapsed in a spectacular heap.

HSMM played a significant role in the three-year, $258 million renovation program to strengthen the first of the Pentagon’s five chevron-shaped wedges, an area encompassing 1.1 million square feet. Fortunately, the jetliner struck the renovated area, where workers were still putting on the finishing touches. About 4,600 workers had yet to move back to their offices or were just preparing to move out of Wedge 2 in preparation of the next renovation phase.

Now, Biscotte and others are engaged in a post-mortem on how the venerable headquarters of the U.S. military survived the worst attack in the Washington area since the War of 1812. The Boeing 757, hijacked after taking off from Dulles International Airport, smashed through four of the Pentagon’s five rings at 460 miles per hour. It ripped open a gaping hole, plowing through Wedge 1 and boring deep into the unrenovated Wedge 2. Much of the surrounding structure collapsed, but not before dozens of Defense Department workers could escape safely. The blast and fireball from the fully fueled airliner was contained by blast-proof windows, steel supports and concrete-reinforced walls.

"Some of the things that were utilized were certainly successful," says Biscotte, a vice president at HSMM. "We’re looking at what happened and extracting what lessons can be learned for not only that building but other buildings."

If there’s any silver lining, it is this: The lessons of the Pentagon and the World Trade Center are likely to be incorporated into a new generation of stronger office buildings. Already, architects and engineers are looking at incorporating blast proof windows or reinforcing walls to harden existing buildings. "It’s not cheap and it’s not easy, but it can be done," Biscotte says.

Perhaps the best examples of retrofitting are on the West Coast, where skyscrapers and run-of-the mill buildings have been renovated to give them more sway to withstand earthquakes. In the war against terrorism, window glazing probably provides the most bang — or defense against the bang — for the buck. These coatings, which use materials such as polycarbonate laminates and thermally tempered glass, make windows resistant, though not impervious, to bullets, blasts and other forces. At the Pentagon, thick windows costing $10,000 each were surrounded by reinforced steel construction and fragment-and fire-resistant, Kevlar-like fabric between the walls.

Engineering and security experts say people shouldn’t expect miracles. The terms "blast proof" and "blast resistant" have been thrown around liberally since the Sept. 11 crash. "No building can be perfectly safe. We all know that," says Lee Evey, manager of the Pentagon’s renovation program. "There’s no such thing as blast-proof windows, and there’s no such thing as a blast-proof facility. It can’t be built."

Even so, building owners can take prudent steps and incorporate some of these techniques in existing buildings. Glazing is easy to incorporate. Adding stronger window frames, however, could require significant structural changes.

As they study how to shore up buildings with the Pentagon example in mind, engineers need to strike a balance between strength, flexibility and breathing room. Masonry walls tend to be brittle and break up, while hard materials like concrete may not absorb enough of a blast. "If they are not designed to protect against the specific threat, they can become projectiles," says Biscotte. Lighter materials and metals such as gypsum wallboard can provide necessary venting.

One of the best measures for mitigating a terrorist attack remains distance. Building owners can help keep potential threats away by altering traffic patterns and using barriers. Still, it becomes impractical to protect against every conceivable threat. "It’s not going to be cost effective," Biscotte says. "It’s not going to be friendly. It’s just not going to [create] places we’re going to want to visit."