The Unforgettable Fire- Part 2
Continued from the magazine, our group of leading fire-protection engineers discuss issues stemming from the events of September 11.
Editor' s note: The following is a transcript of a special panel of some of the leading fire-protection engineers in the community, assembled to discuss the fire that consumed the World Trade Center Sept. 11, 2001 and the impact the event may have on the design and maintenance of high-rise buildings from a life safety aspect. The story appeared in our October issue.
Gerry Schultz , president, Fire Protection International, Woodridge, Ill.
Tom Jaeger , president of Gage Babcock & Associates, Fairfax, Va.
Rob Sedlak , senior vice president, Flack + Kurtz, New York, and the fire protection designer of Petronas Towers in Malaysia.
Les Strull , RJA, Chicago, and also a member of the Chicago City Council on High-Rise Buildings
CSE : The fires that consumed the World Trade Center Sept. 11, were certainly shocking and beyond anything we' ve ever seen. Was the buildings' collapse a failure of the fire protection design?
Jaeger: No. The major difference between a 'normal' high-rise fire and the World Trade Center fire was that this was really a bomb.
Sedlak: The amount of jet fuel on board was the real cause. The fire was also taking place on multiple floors, something fire-protection systems are not designed to handle.
Strull: In fact, most fire-protection systems are designed for one fire at a time and usually to only to contain a fire that starts out small, In other words, the fire activates a few sprinklers and hopefully extinguishes the fire. In the case of the planes crashing into the buildings, they were jumbo jets and certainly more than 1 story tall. They probably hit at least two floors, undoubtedly scraped off any fireproofing on the columns and beams and ruptured sprinkler lines, making them totally ineffective.
CSE: I read that the fireproofing was CAFCO Type D. Did that make any difference compared to current fireproofing?
Strull: It's similar to what' s used today. It's a low-density material that's easily scraped off. You can take your hand and knock it off.
Schultz: Actually, one of the positives in the tragedy was that this building did not use any asbestos-type fireproofing, which we are seeing today. So at least there wasn't an asbestos problem in the clean up.
CSE: Speaking of modern technology, the WTC was based on technology and systems more than three decades old. Would today s systems and equipment make any difference in stopping the fire? What if this incident happened at Petronas Towers?
Sedlak: The technology we used in Petronas was similar because the codes were similar. Most of the advances in fire-protection technology have been in labor savings. Perhaps the exception is quick-response sprinkler heads that were not available in the 70s when the towers were built.
Strull: If the building was opened the day before the attack it wouldn't have made a difference. A plane that size, with that fuel load, would have ruptured any sprinkler lines so they would not have operated. If anything you would have a ruptured pipe with water all over the place.
Sedlak: I agree. If the building was in no danger of collapse, and firefighters could have been able to get up there, there's likely not a lot they could have done, as the risers would have been ruptured so they would have got up there and had no water.
Schultz: Speaking of structural stability, I think it's remarkable that the buildings stood for as long as they did, subject to a jet fuel fire, a much more severe than any fireproofing was designed to withstand.
Sedlak: The building really performed how you would have expected it. Fireproofing is good for typically two hours for a normal office load fire. And the heat given off by the jet fuel was more than half the fuel load it was rated to withstand.
CSE : WTC was unusual structural design (a tube concept). Would a more traditionally framed building have made any difference, particularly if it was concrete or reinforced with concrete?
Jaeger: How much concrete are you talking about? Enough to make the plane bounce off the building?
Sedlak : I'm not sure it would have mattered. When we evaluate buildings as to whether they should be steel or concrete, it still is a 2-hour-rated building, so a concrete building would have failed as well.
Strull: One of the things I read was the buildings were designed to withstand the impact of a 707. And when you think about it, they did. What it wasn t designed for was to withstand the fuel load of jet.
CSE: Would more modern insulation materials in the curtainwall itself make any difference? Or a more sturdy skin for that matter?
Jaeger: One of the big considerations for a curtain wall is aesthetics and cost. I don't think there's anything in the codes that require any impact guidelines other than meeting certain wind loads.
Sedlak: That's true. In South Florida there are codes that make sure building exteriors can withstand hurricanes, but certainly not a 767.
CSE: But will the WTC incident make the codes change? How do you forecast how the event will change building life safety design?
Schultz: I think we'll have to start looking at minimum egress and stairwell width. Especially if you're trying to move firemen up 43-in. stairwells. But the real question is how do you fight fires in a building like this? Do we really expect firemen to climb 80 stories?
CSE: What about special egress needs? There were reports that many people with disabilities were simply trapped and unable to get down stairs.
Sedlak: Some buildings are designed with an area of refuge, which can be a fire-rated vestibule people can go to until someone can rescue them. But in this type of incident it probably was destroyed.
Jaeger: Current thinking is that you try to ride the fire out or proceed with a slow evacuation down the stairs. You could design a scheme with your elevator banks, with smoke compartments, where you designate one bank to be safe and usable in event of fire.
CSE : How about damper and fire and smoke-control schemes?
Schultz: In the case of the towers so much was happening that no one thought probably even thought about shutting down the fire floors. And again, in a normal office fire the idea or hope is that sprinklers will be able to extinguish the fire when its small and we really put a high degree of reliance on such a scheme.
Strull: For most fires, sprinklers will control the fire and there's no need to evacuate.
Sedlak: And you'll typically have a smoke exhaust system with pressurization on the floor above and below the affected area, so you'll be able to push the smoke to the fire floor and then exhaust it.
CSE: Are more passive measures necessary?
Schultz: No. We do include passive measures, such as compartmentalizing the building by providing separations at the floor and enclosure in the stairwells.
Sedlak: I agree. Beyond normal office fires, buildings are safe. It's when we get into catastrophes like this that they fail.
Strull: I don't think anything you could have done, unless you designed it like a WW II concrete bunker, would have done any good [preventing the WTC fire]. And of course it's too expensive to do that and not practical to build it. You have to balance between making a building functional, usable and affordable.
CSE : But will we see an upgrade in fire-protection equipment and systems in the wake of this tragedy? In other words, will owners be more open to using more expensive equipment?
Sedlak : I wouldn't be surprised to see that happen even as a marketing strategy to get people into their buildings.
Jaeger: I think you have to look at the cost. For example, as the result of the terrorist bombing of the Murrah Building in Oklahoma, the government certainly has upgraded its blast-resistance capabilities (the Pentagon for instance) at a huge cost. But I'm not sure private industry is prepared to do that. The same for the average building tenant. I don't think they're prepared to pay for that. Making a building more blast resistant than it is today could increase the rental space by as much as 50% or even a 100%.
Strull: I think the real issue lies beyond better-protected buildings. I heard the FAA saw these planes go off course at a low attitude and didn't know who to call. I think that's part of the problem. Perhaps they could have been intercepted if there was a plan in place to deal with these kinds of threats. I don't know that we can design a building to survive the impact of a plane fully loaded with jet fuel.
Jaeger: Without question the cheapest fix is to upgrade the wall between the cockpit and the passengers and then have a policy that that door never be opened.
Strull: And then you depressurize the cabin to knock everybody out.
Jaeger: But that's not a building code or fire protection fix.
CSE: Then how about the idea of simply not building high-rises or super high-rises anymore?
Strull: I'm not sure the buildings were attacked because of their height so much as they were the symbol of American economic might. If they had been a cluster of 20-story buildings, it still would have been a symbol and still might have invited an attack of this kind.
Schultz: I think the public will still have a large say of what gets built, it's always been that way and always will be. If the public starts complaining about these high-rises, and businesses start looking for new rental space, the market will dictate the situation, not what we say.
CSE: But what about in cases like Manhattan where real estate is scarce and high-rises may be the only practical solution?
Strull: It's a matter of reassuring the public. Some 6,000 people were killed in this one incident. But 6,000 people die every year from fires. And the majority of fire deaths occur in single-family dwellings. In the city of Chicago, we had about 80 fire deaths last year. About 60 or 70 were in buildings less than three stories in height. So if you extrapolate that to the rest of the country you end up with about 6,000 or 7,000 fire deaths a year, mostly in low-rise buildings. So what I'm trying to say is that you're not unsafe in a high-rise building. You're not going to have an incident like this happening day after day or even year after year. Things are being put in place to prevent this from happening. But it's going to take an education program for the public to realize they're not unsafe.
Jaeger: You also have to put this in perspective. It was an act of war, not an ordinary fire or accident. And it probably shouldn't even be lumped in with fire or accidental deaths.
Strull: That's true. I heard in the news that some of the terrorists were considering renting a crop-dusting plane and considering a biological attack. So how can you prepare yourself against something like that?
Jaeger: It harkens back to the incident in Japan's subways a few years ago. It prompted federal agencies to look at biological and chemical protection for their buildings. But they're having trouble finding a reasonable solution, how much more would it be trying to stop a 767 from plowing into a building.
CSE: Still, will building owners ask designers to provide more defensive measures ?
Strull: You can add such measures and still do it in an aesthetically pleasing way. The Social Security Building in Chicago was retrofitted so you can't get past the curb, for example. But can you put bollards 1,300 feet up in the air?
Jaeger: And strong enough to stop a plane vs. a vehicle?
CSE: While it sounds like there's not much that can be practically done, this incident does not mean it's the last. Is there anything that can be done on the design side?
Strull: I don't think its possible to make such a building that at the same time would be desirable to work or live in and have it be functional or economical.
Jaeger: You could make buildings with better resistance, but like Les said, you have to balance to economics and functionality. We already make that trade off with our cars. We could build them much more capable of withstanding collision, but economically and fuel-wise, we don't do it.
Strull: We do build them, they're called tanks and generating plants on the building side.
CSE: How will this incident affect construction in general?
Strull: If developers can get insurance at a reasonable cost they will build.
Sedlak: It's going to be purely driven by the economy. If the companies need space, they're gong to build buildings. They may not build landmark buildings that you'll know on the other side of the ocean, but they're going to build the office space if business warrants it.
CSE: How about on the international front? Will we see any more marquee structures like Petronas Towers?
Strull: I think so. The same reasons they were built before will still apply, mainly ego stroking.
Schultz: Has this incident affected plans for the proposed Trump Tower in Chicago?
Strull: I don't think it's going to stop the project. 1) Trump's ego needs stroking, and 2) this will be more of a residential project and won't be the same kind of a symbol of the World Trade Center.
CSE: What should be done about the towers themselves' should they be rebuilt?
Sedlak: I think they should be rebuilt (1 ft. higher even) as a symbol, thumbing our noses at terrorists, that they can't intimidate us. We are going to keep building and building higher. We need to not be afraid of them, but get rid of them. As far as the costs for making airplanes safer. They say it will cost $2 billion to put marshals on every plane. If you calculate that out at 30-40,000 flights per day, and multiply that by 365, it comes to a $3 surcharge per passenger. I would certainly be willing to pay $6 more on a roundtrip ticket.
Strull: I'll give you $10.
Jaeger: We also know that of those flights you mentioned, a good majority are flown with smaller commuter aircraft that are not the same threat as fully fueled 767s.
Strull: A question we should really ask did they [the terrorists] think the building was going to come down. They may have just wanted to create panic and burn up a few floors. Ultimately, all they've done is tick off Americans. They thought we'd be afraid and give into whatever they would demand, but I think just the opposite has happened.