First Draft: 11/08/01
Certainly there is great discussion and debate about what to do with the World Trade Center site. (Which I feel has been dehumanized by the term "Ground Zero") Although at the moment, we are certainly years away from doing anything with the site, I wanted to give my opinion on the matter of rebuilding.
I doubt the site will ever be turned solely into a memorial. Comparing it to other disaster sites is not a fair comparison. This land is of the most valuable in the world, not only just in dollar value but in what it means to the people and economy of the whole world. The site was already a memorial: it was a memorial to hard work, to prosperity, to looking toward the future with optimism It was an icon whether you liked it or hated it. Although from my perspective those buildings were always there, but I can imagine what it must have meant to the teenagers and college kids in the 70's, as they watched those towers rise over the decaying city of the 50's and 60's with hope for the future. Yes, they were gray concrete columns- but they were more than that. But, I think there are far better reasons for rebuilding than just a personal sense of macroscopic homeopathy. I think I'll leave my waxing to another document- for now lets get on to the details of the new Trade Center.
From an engineering perspective, although the towers did collapse in the end, the structures behaved exactly as expected. I think its a safe assumption that the vast majority of buildings in the world would not have even survived the initial impact of the 757. The fact that the buildings were able to survive the initial impact and not collapse saved tens of thousands of lives, including my own. And, when the steel of the building finally did succumb to the intense fire, it collapsed straight down. Indeed causing significant damage to the area, but consider what would have happened if a "stronger" building had simply toppled over, crushing many more buildings for blocks around. Many more lives would have been lost in that event. The structure was not at fault, and in fact it behaved exactly as it should have- thanks to the engineers who designed it.
The Twin Towers concept has indeed proven its worthiness from a structural engineering perspective. Additionally, by having two structures instead of one large one, there are other means to improve redundancy and save lives in the event of a future disaster. I believe by splitting building services and a few minor modifications, a new Twin Towers could set the pace for future high rise structures the world over.
One problem with high rise structures, is, was, and will always be a simple one: fire. The problem with major fires is that they have a potential to cut off the escape from floors above the fire site, as we saw in the disaster of 9/11. Traditional wisdom held that the people on floors above the fire should sit tight with their fire doors closed and wait for rescue. In today's reality, though, people would be likely to panic. So, how to escape? Well, the most obvious means of escape is the redundant tower right next door. Certainly, aside from a risky helicopter airlift reminiscent of the flight from Saigon or keeping thousands of parachutes on the roof, there's little to do to escape in the traditional sense. Consider that having a fire on two floors of two entirely different buildings is extremely unlikely, so two or three skybridges between the two buildings would be a simple and effective means of providing escape to those who may be trapped on floors above a major fire. I think that it would also appease people's minds to know that if they had to, they could in the worst case go up to the next lobby and walk across to safety. In addition it would, of course, reduce traffic in the ground lobby and improve travel between the two buildings. The Petronas Towers have one of these bridges, but there should be at least two, maybe one every 25-35 floors.
(You can view a somewhat crude (32k) diagram of this arrangement here. Visio does not have a "Skyscraper" template so I had to build it from scratch!)
Other safety improvements would be wider and more numerous stairwells, with positive airflow from top to bottom to try and force smoke down and out. Separate HVAC, power, and communications lines for each tower would be very good ideas- especially separate HVAC, which would hopefully prevent smoke and fumes (and maybe terrorist bio/chemical agents) from spreading between the two buildings.
I think to prevent a repeat of what happened on 9/11 is not to build a hardened bunker that could actually survive an airplane impact. Although the likelihood of a repeat of that type of attack is very small, instead of contemplating strengthening the structure, we should improve its ability to defend itself and the city of New York from another terror attack. One unique feature of the Twin Towers was that unlike many other signature New York skyscrapers, it has a flat roof and no spire. So, aside from its use as an observation deck, why not build an air defense platform up there? One Phalanx radar controlled cannon, one Patriot-like missile launcher, and one attack helicopter sitting on top of the highest point in the metropolitan area would serve as a deterrent to any future plans of an air or missile assault on the city. It would of course improve the mood of anyone working in the building or in the city to know that there is an active form of defense protecting them.
Architecturally, although the original structures were often accused of being "uninspired" and "bland", I think that the structures are by design simple and visually appealing. The only thing I would consider is maybe adding colored floodlights to the top of the building to light it up at night, something like the Empire State Building has. How tall? I think anything below 100 floors would be wasteful. Anything over 120 floors though would probably be impractical.
The courtyard between and behind the structures should be built as a memorial, utilizing the old walls that stood after the collapse. Also should be a monument to the police, fire, and EMS workers that were killed in the collapses, and perhaps either on the ground or a wall similar to the Vietnam Vets memorial, a listing of the lives lost in the disaster.
Would people return to work in the towers? I think people would need some convincing. New safety features aside, in the 8 to 10 years it would take to rebuild the structures, I think the fear will fade somewhat. (assuming of course we are able to protect ourselves from future terrorist attacks) I remember the droves of people who said they would never go back to the Trade Center after the bombing in 1993- obviously untrue. Yes, I'd work there. Hopefully they'll have the air defense platform on the top though!
In all, I hope to see the return of the towers in the years to come. I would be proud to work there- hell, I may even help build them.
What's your opinion?