M. Spencer Green, Associated Press
CHICAGO — What if it happens again?
A decade after 9/11, could any of the nation's 21,000 high-rises withstand an attack like those that caused New York's twin towers to collapse? Could the thousands of people inside find a way to safety?
At Chicago's Willis Tower, like other skyscrapers around the country, much has changed since two hijacked jets slammed into the World Trade Center. North America's tallest building now has concrete barriers, metal detectors and sophisticated security cameras that trace every nearby movement.
But those measures might do little to prevent a calamity on the scale of Sept. 11. Despite proposals for major structural changes over the last decade, thousands of buildings remain vulnerable, experts say, because the cost to retrofit them is too high, and cities and states have been slow to adopt tougher building codes for new construction.
Less sweeping improvements, such as equipping elevators for use in evacuations, are lagging behind other countries, too.
"You only can do as much as lobbyists, politicians, and the agencies you're dealing with will let you do," said Monica Gabrielle, whose husband died in the 9/11 attacks and who co-chairs the Skyscraper Safety Campaign that sprang up afterward. "The further away you get from events, then you become more complacent."
And for all the talk about beefed-up security, there is only so much that can be done to protect buildings that stand 1,000 feet or more above the ground — something Donald Trump implicitly acknowledged when he decided his new Chicago skyscraper would not climb as high as the Willis Tower because he did not want it to become a target.
While there was talk after 9/11 about making skyscrapers sturdier and easier to escape in an emergency, the structural work that would have been necessary was either too expensive or just impossible.
"I don't know of any buildings that have gone through a structural retrofit for the purpose of withstanding a major attack like 9/11," said Adrian Smith, an architect who designed the Trump International Hotel and Tower in Chicago and the Burj Khalifa in Dubai, which is now the world's tallest building.
At the same time, building industry groups have taken some steps to make new structures safer and more secure. They've proposed 40 construction code changes such as wider stairways to ensure firefighters can climb up while occupants are coming down.
Municipalities can adopt the changes as they see fit, but they are not mandatory, said Steve Daggers, a spokesman for the International Code Council.
Chicago, for example, adopted an ordinance that requires high-rises to have an emergency evacuation plan on file with the city. And the tallest buildings must provide the fire department with their floor plans so crews know the exact layout of the buildings when they walk in.
People who live and work in high-rises around the city say evacuation drills are now routine, something many say never or rarely happened before 9/11.
Many high-rises are also tougher to enter. In the immediate aftermath of the attack, Willis Tower installed airport-style security, complete with officers searching bags.
That has been scaled back, said David Milberg, a spokesman for the Schiff Hardin law firm, which has offices a little more than halfway up the 110-story building.
"Now we have key-card access for tenants. Nontenants must produce photo IDs, and we have to register guests in advance," he said.
"It's not as conspicuous as it was, (but) you don't get in here unless you're vetted," he said.
Not surprisingly, new buildings, those under construction and those on the drawing board have a number of features that older buildings did not.
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