Comcast Center, skyscrapers use post-9/11 safety features

At just under 1,000 feet, the Comcast Center in downtown Philadelphia will be the tallest building in the city and the highest skyscraper between New York and Chicago when construction is completed early next year.

The unfinished building has already muscled its way to the top of the city skyline.

But what's less apparent is that within its walls, the tower will contain many safety features that reflect the lessons of Sept. 11 and that are making their way into new skyscrapers in cities across the nation.

Still visible is the upper portion of the huge concrete core that will rise to the top of the 975-foot tower. Embedded within it will be elevators and stairwells as well as sprinkler, electrical and communication lines.

The skyscraper will also have a pressurization system to keep smoke on any one floor from traveling to other floors. Steps in the tower's stairwells will be 10 inches wider than what building codes require, so more people can evacuate at once, and a system will be in place to keep smoke out of them.

The project's structural engineering firm, Thornton Tomasetti in New York, oversaw the rescue efforts and cleanup of the World Trade Center.

"We were able to take the benefit of the work they had done to make very significant modifications in the design of the building," said John Gattuso, senior vice president of urban and national development at Liberty Property Trust in Malvern, Comcast Center's developer.

The new features address weaknesses found by an investigation of the World Trade Center disaster on the part of the U.S. Commerce Department's National Institute of Standards and Technology.

When hijacked planes hit the twin towers, they took out the elevators and several stairwells, the October 2005 report said. The impact of the planes alone could not have caused the collapse, but they also significantly dislodged fireproofing insulation and damaged sprinkler lines. Red hot fires from burning jet fuel weakened the steel frame and the towers buckled.

Across the country, skyscraper developers are voluntarily installing safety features similar to those at Comcast Center, with an eye to making buildings better able to withstand any number of different kinds of shocks. They're also shoring up floors to prevent a progressive collapse and fine-tuning emergency procedures to better aid firefighters.

"Following Sept. 11, there has been a worldwide reevaluation of safety in tall buildings," said David Scott, chairman of the Council on Tall Buildings and Urban Habitat in Chicago. "Iconic skyscrapers are more interested in it than other buildings."

One Bayfront Plaza, a tower in Miami slated to rise more than 1,000 feet high, will be built to withstand heavier shear forces from wind or even plane crashes. The two-tower complex will be using a strap system that interconnects floors with high-tensile steel for strength.

"A plane slamming into the building can only damage two levels," said Tibor Hollo, president of Florida East Coast Realty in Miami, which is developing the project. Plans were submitted to the city last September and construction is expected to start in 2012.

Though Miami might not be as likely a terrorist target as Washington or New York, Hollo said, it's better to be prepared.

"It's the sign of the times," he said.

In New York, 7 World Trade Center boasts a core made of thick concrete, rather than steel. The 741-foot tower, completed last year, has beams protected by five times the fireproofing required by code. Redundant water pipes feed the sprinkler system in case one line is destroyed. Evacuation stairwells are pressurized to keep out smoke and are 20 percent wider than required by law.

Similar features also will be found in the 1,776-foot Freedom Tower, which is being built at the site of the collapsed World Trade Center in lower Manhattan.

Solit Interests Group in Orinda, Calif., will be developing two 1,200-foot towers at First and Mission streets in San Francisco. The company said the skyscrapers will incorporate similar safety features as other tall buildings but deemed it too early to discuss any details. The project's plans were filed with the city in December.

"These are high-profile buildings that need to be protected beyond code," said Curtis Massey, chief executive of Massey Enterprises Inc., a high-rise safety and disaster planning firm in Virginia Beach, Va., that has had talks with Liberty Property Trust.

Hardening the core and adding other safety features likely will add less than 5 percent to construction costs, Massey said.

Changes don't have to be expensive. For instance, one federal recommendation is for fireproofing inspections to be done after other contractor work is completed, said Shyam Sunder, lead investigator of the World Trade Center collapse. Workers sometimes knock off fireproofing, so it's better to have an inspection after all work is done, he said.

But adding safety features does reduce the amount of leasable space. At Comcast Center, the wider stairs decreased leasable space by nearly 4,500 square feet throughout the tower. The concrete core will take nearly 13,500 square feet away from tenants, but Liberty said the lack of steel outrigging and fewer columns make up for that loss of space.

Comcast Center will have 1.2 million square feet of office and retail space.

Amid all the extra precautions, building industry officials are debating whether they're being overprotective.

"The Freedom Tower is potentially a target. A residential, 25-story condo is probably not a target," Scott said. And the risk of another attack on the scale of Sept. 11, he said, is "very, very low."