Architects Have a Blast Testing Freedom Tower

In a hillside bunker in a New Mexico desert two weeks ago, a New York architect peered through a periscope as, about 1,300 feet away, a simulacrum of the Freedom Tower’s exterior was blown up.

“Once the charge was detonated, even from a quarter of a mile away, the entire bunker shook,” said Carl Galioto, a partner at Skidmore, Owings & Merrill, the architecture firm that designed One World Trade Center. The 1,776-foot-tall, spire-topped skyscraper, formerly known as the Freedom Tower, is slated to rise at the northwest corner of Ground Zero by 2012.

“The specimen performed beautifully, far exceeding our expectations,” Mr. Galioto said.

Which is to say that only portions, and not all, of the so-called specimen—a three-story mock-up of the building’s glass-and-aluminum facade—shattered in the isolated desert 90 minutes south of Albuquerque.

Mr. Galioto wouldn’t reveal the strength of the explosive device for security reasons, but said that a Port Authority security consultant and New York City law enforcement officials determined the criteria for the test.

“It is something that, having seen it, having participated in it, certainly raises my confidence in the project,” he said.

“Dynamic” testing—i.e., blowing up materials destined for building exteriors—is not standard operating procedure for skyscrapers. The technique, developed about a decade ago, is generally reserved for the construction of highly sensitive government buildings in foreign countries, like the American embassy that Skidmore, Owings & Merrill built in Beijing.

“But it’s now being applied to [other] buildings,” Mr. Galioto said. In fact, materials intended for another New York City tower—Mr. Galioto wouldn’t name the project, though he did say that his firm wasn’t designing it—were tested at the same laboratory days before the tests for One World Trade Center.

Thankfully, rainstorms and high winds are more commonplace than bombs in New York City, so Benson Industries, the contractor building the glass exterior for the architect, had to make sure the material could handle those environmental pressures, too.

Testing of another mock-up of the glass, which will cover one million square feet of the tower, took months and spanned a continent—wind tunnel tests outside of Toronto; thermal tests in Ontario, Calif.—all to ensure that the future tower can withstand apocalyptic wind speeds of up to 150 miles per hour, deluges of rain the likes of which New York has rarely seen, a low-level earthquake and rapidly changing temperatures.

But none of that compared to the drama of the blast test.

“The only way to reach the exact site was drive by four-wheel-drive vehicles for a number of miles,” Mr. Galioto said. “There was a dirt-and-rock road.”

Architects Have a Blast Testing Freedom Tower