High-rises remain vulnerable after 9/11
More than a year after terrorists destroyed two of the tallest skyscrapers in the world, few physical or structural changes have been made to strengthen tens of thousands of other high-rises in America.
Cities, developers and building owners have focused on safety measures such as evacuating people more quickly, but the nation's high-rises remain largely as vulnerable to catastrophic attack as they were on Sept. 11, 2001.
Major changes in design and construction that would retard fire and help evacuations — two critical issues in the disaster at New York's World Trade Center — won't show up soon, if at all, as requirements for new tall buildings. That's because revisions in building codes, which are controlled by state and local governments, could take years to draft. Major physical alterations of the same sort to existing high-rises might be impossible, impractical or prohibitively expensive.
Of course, none of the nation's tall buildings was designed to survive what was unthinkable until the twin towers were attacked: Hijacked jetliners, loaded with fuel, intentionally exploding into them at 500 mph, igniting 2,000-degree fires that twist and melt the structure into catastrophic collapse.
"After Pearl Harbor, people didn't say, 'Ships are unsafe (so) you have to build unsinkable ships,' " says David Maola, executive director of the Council on Tall Buildings and Urban Habitat, which promotes better design and construction of high-rises. "No, you have to keep airplanes away from ships — and you have to keep airplanes away from buildings."
An initial investigation completed last spring by civil engineers and federal emergency managers (www.fema.gov/library/wtcstudy.shtm) explored likely causes of the Trade Center collapse. Investigators found that the twin towers withstood the initial impacts of the two airliners, but centrally clustered escape stairwells and fire sprinkler supply lines, which were encased in lightweight walls, were knocked out instantly. Fire was a bigger factor: The impact and flying debris probably jarred loose spray-on fireproofing from beams and trusses both in the twin towers and in a neighboring high-rise that also collapsed. The structural steel was softened to the point of collapse by intense blazes that were fed and spread by the jets' aviation fuel.
Even though building code changes may be years away, some of those early conclusions are beginning to influence the design and construction of high-rise projects. Among measures being added or considered:
Locating stairwells farther apart, widening them for faster evacuation and encasing them in concrete.
Strengthening connections and joints in structural steel framing.
Using fireproofing that clings better to beams and girders, and applying it more thickly.
Installing backup water supplies for fire sprinkler systems.
Some high-rises thought to be vulnerable to terrorism, either as targets or as neighbors of other high-profile buildings, also are being "hardened" against bombs and other attacks with structural reinforcements, shatterproof windows and other measures. New York's 59-story Citigroup Center is undergoing work to strengthen a leg-like support column thought to be exposed to potential attack where it faces busy 53rd Street in midtown Manhattan.
New York set up a building code task force to examine many issues after the twin towers' collapse. It is expected to report its findings in December.
But most local governments are not rushing to revise codes and procedures. Nor will the federal government step in to order changes. Except for federal jurisdiction in areas such as workplace safety and accessibility for the disabled, codes for building design, construction and operation remain local or state responsibilities.
Focus on safety
Just as aviation security was tightened to unprecedented levels in the hijackings' aftermath, so too was security in tall buildings: More guards and cameras, metal and X-ray screening, more elaborate access-control systems, concrete barricades on sidewalks, even bomb-sniffing dogs at loading docks. Now, safety measures are also under review. Skyscrapers in some cities are providing fire and rescue agencies with critical details about their layout and systems so crews can respond more quickly and safely.
Here in Chicago, an ordinance since the terror attacks requires the city's 56 tallest buildings to provide such data twice a year on CD-ROM so fire commanders can check the data instantly via computer at the scene.
Evacuation. From New York to Honolulu, city fire and emergency agencies are rethinking how, when, whether and whom to evacuate. The traditional philosophy has been to keep high-rise occupants at their desks unless their floor or one near it is at immediate risk. But on Sept. 11, workers who fled the upper floors of the World Trade Center's south tower immediately after seeing the first jet hit the other tower were more likely to survive. Those who obeyed announcements to stay put or go back did not, once the second airliner had struck and crippled their building 16 1/2 minutes later.
Today, many tenants "self-evacuate" in any high-rise alarm, regardless of what building managers tell them. In some cases since Sept. 11, authorities in New York, Boston, Los Angeles and elsewhere have cleared out entire buildings in emergencies. But safety experts still caution against wholesale evacuations: "There's no sense in emptying a building with 7,000 or 8,000 people in it if you have a garbage can on fire," says Robert Solomon of the National Fire Protection Association, which drafts safety and fire standards.
Drills and alarms. From Chicago's 110-story Sears Tower to New York's 50-story W.R. Grace Building, owners and managers voluntarily perform more frequent fire and escape drills, sometimes at the urging of tenants who once considered them a nuisance. Most cities don't require extensive or buildingwide drills, but that's changing, too. This month, Pittsburgh's mayor proposed requiring twice-yearly drills in the city's 300 high-rises. In Los Angeles, the city attorney has proposed mandatory evacuation tests and emergency plans for all high-rises.
Some workers, companies and residents even insist on practice evacuations all the way to the ground, not just to exit doors or down a floor or two as before. "Nobody trusts the structural integrity of buildings any more to save them or protect them," says Judith Telingator, who lives in Chicago's One Magnificent Mile, a 57-story office and condominium tower whose occupants now drill monthly, floor by floor. "Now we're much more confident about what to do."
Stairs. Some high-rises are upgrading signs and equipment in exit stairwells, the only escape route in most emergencies. In Chicago, the 65-story 311 South Wacker Drive building installed glow-in-the-dark signs, arrows and striping to guide evacuees in case backup lights fail. Experts also are scrutinizing the standard 44-inch stair width for future high-rises, a norm that some critics say is too narrow to accommodate occupants fleeing downstairs and firefighters going up. The evacuation of an estimated 50,000 people after the 1993 bombing at the World Trade Center took nearly four hours, precious time that Sept. 11 victims never had. But lighting and sign improvements made after the 1993 attack did help evacuees nine years later. So did having three evacuation stairs in each tower (one of them 56 inches wide) rather than the two required by building codes.
Equipment. Some high-rises, including the Sears Tower, are equipping stairwells with two-wheeled escape chairs to help carry disabled or injured occupants. Because of tragic 9/11 stories of doomed firefighters overburdened with gear and out of radio contact, Chicago and other cities are reviewing emergency communications and requiring or recommending that skyscrapers install lockers or closets with hoses, axes and oxygen tanks on upper floors so firefighters don't have to carry them. Also gaining renewed interest: "evac kits," often in red fanny packs, that workers keep at their desks with escape essentials such as glow sticks and water.
"It always takes disaster to bring about change," says Curtis Massey, a high-rise safety consultant from Virginia Beach. A former firefighter, Massey has written quick-read, color guides for fire departments to hundreds of skyscrapers, including the tallest in 30 of the nation's 34 largest cities.
Thousands of buildings
As a practical matter, only a few major skyscrapers rise to "icon" status and thus qualify as potential targets of terror. But the fiery deaths of so many occupants and rescuers — 2,803 victims in the New York towers — set off alarms about safety against any disaster in buildings with floors beyond the reach of conventional fire ladders.
That means anything taller than about 75 feet, a common definition of "high-rise."
Skyscrapers.com, which compiles building statistics worldwide, uses a higher definition: At least 115 feet or 12 stories tall. By either yardstick, thousands of buildings (more than 16,500 nationally and at least 4,448 in New York City alone, by Skyscrapers.com's count) face potential review.
Safety consultants are doing brisk business since 9/11. Disaster-planner Massey has taken on 40 to 50 more buildings, and three major property management firms ordered his guides for all their New York buildings.
Engineers who specialize in armoring embassies and other potential terror targets now do similar jobs for high-rises and other commercial structures.
"Our existing clients are coming back and saying, 'Do I have something to worry about?' " says Robert Underwood, vice president of facilities security for Carter & Burgess Inc., a design and engineering firm based in Fort Worth.
"It's not for everybody," says Tod Rittenhouse, a blast-resistance expert for New York-based Weidlinger Associates Inc., whose clients often seek protection against hits on nearby targets such as federal buildings or foreign consulates.
Even safety-minded investors have jumped in to market an array of evacuation ideas — from a high-tech hovering rescue platform to rescue slides and quick-pop personal parachutes.
Professional groups also are pushing safety.
The Council on Tall Buildings and Urban Habitat (www.ctbuh.org) has published twin guidebooks since Sept. 11 — one on recommended safety enhancements for building owners and designers, the other to help people who live and work in high-rises assess how safe they are. The National Fire Protection Association (www.nfpa.org) is holding one-day seminars this fall in 19 cities from California to Florida to help high-rise managers draft emergency plans.
The Skyscraper Safety Campaign (www.skyscrapersafety.org), founded by families of Trade Center victims, advocates numerous code reforms in New York and pushes for a more critical probe of how the city handled the disaster.
Industry groups from cement and steel manufacturers to engineering and architectural associations help draft model codes that states, cities, counties and townships adopt or modify for local needs. If dramatic design or construction flaws are found in disasters such as major fires and building collapses, "the model code system can react responsibly and quickly — within a year — to identify a solution," says Paul Heilstedt, chief executive officer of Building Officials and Code Administrators International, a trade group. But he says "the jury's still out" regarding the World Trade Center.
"People may be impatient, but the studies aren't done yet," adds Jonathan Barnett, a fire-engineering professor at Worcester (Mass.) Polytechnic Institute.
Last month, the federal government's National Institute of Standards and Technology (NIST) began a two-year, $23 million study of the towers' collapse. Its findings could lead to tougher building and safety codes for tall buildings. But they would be recommendations, not edicts.
The same goes for an initial study by the Federal Emergency Management Agency and the American Society of Civil Engineers, in which Barnett participated. Among other things, that report suggested constructing emergency stairways farther apart and "hardening" them to resist outside impacts.
Safety vs. livability
When they do come, code changes could cost developers and owners millions of dollars in added expense for constructing buildings or adding safety improvements to older ones.
"You can make a building that's fireproof and airplane-proof," says Larry Soehren, president of Building Owners and Managers Association International (www.boma.org), the industry's trade group. "But nobody's going to want to live or work in it" because it would be a windowless concrete bunker, not a soaring architectural gem. "Let's do science and research first."
In New York, the building-code task force is considering a proposal that fire safety directors recommended more than 25 years ago: Mandatory fire sprinklers in all older high-rises, a requirement only for structures built since the 1970s. Many older buildings have gradually been retrofitted, but hundreds have not.
Also under review are design tradeoffs that came with the advent of sprinklers as the principal tool against high-rise fire. Stairwells and building cores, once walled with concrete or masonry, went to lighter, fire-resistant drywall after sprinklers became common. But in the Trade Center attacks, the jets sliced easily through that lightweight construction, fatally severing the towers' central cores of elevators, stairs and water lines to the sprinklers.
Improved fireproofing is another area of scrutiny. "There already exist some materials that will stick better," says Gene Corley, a Chicago structural engineer who led the initial Trade Center study. "Nothing is foolproof, of course, but you also have to look at the safety of high-rise buildings in the last 100 years. They are extremely safe buildings."
In normal conditions, anyway. But after 9/11, almost every aspect of high-rise safety is under scrutiny. "I'm calling for reform, reform, reform," says Sally Regenhard of the Skyscraper Safety Campaign, whose firefighter son, Christian, died in the Trade Center collapse. "We have to legislate so that economic interests and greed do not take precedence over the sanctity and safety of human life.