posted on September 11, 2001 11:46:58 PM
Why Did the World Trade Center Towers Collapse?'
By Dahlia Lithwick
Posted Tuesday, Sept. 11, 2001, at 1:28 p.m. PT
Why did the World Trade Center towers collapse? Weren't they designed to be earthquake-proof and impact-proof?
The 110-story twin towers of the World Trade Center, which stood at a height of 1,353 feet, were designed to withstand earthquakes as well as impacts like that of a plane. This was evidenced by the fact that the buildings did not fall over on impact, says Brian Markham, a structural engineer with the Ove Arup & Partners engineering firm. The more likely cause of the buildings' collapse was the resulting fire, exacerbated by the huge quantities of jet fuel present.
When a fire ignites in a large building, its steel core does not melt, but over time it weakens. As the steel supporting the floors collapses, a "pancaking" effect will result, with each of the upper floors collapsing onto the floor below. This is why the disintegration of the towers was not limited to the top floors. With the accumulated weight of each collapsed floor, the stacked floors continued to fall. This explains why the building collapsed vertically, rather than tipping over.
Big buildings are structurally designed to withstand a blaze for between 2 to 3 hours--time enough to put out the fire and evacuate occupants. Both World Trade Center towers collapsed in about an hour, probably because the jet fuel caused the fire to burn hotter and faster than any would have anticipated.
Markham, while unaware of the fire rating for the World Trade Center buildings, suggests that even with a standard 2- to 3-hour burn time, it would have been extremely difficult to evacuate the 50,000 people estimated possibly to have been inside the buildings. He adds that the tragedy would have been compounded because, while many of the buildings' occupants could not have been evacuated via the exits, they would have been moved to ostensibly "safer floors." As it turned out, there were no safer floors.
posted on September 12, 2001 10:35:01 AM
From what building engineers said last night... The buildings withstood the impact of the planes. They stood from quit awhile after impact. Hitting the buildgs in the middle was intentional. if they hit the very top, they would have stood. If they hit the very bottom, the sttel is so strong they may have stayed up, plus it would have been easier for fire fighters. But hitting in the middle, with full fuel tanks, the fire was hot enough to weaken the steel supports. 1000+ degrees. The upper floors fell, this weight caused a domino effect.
posted on September 12, 2001 10:53:07 AM
Not to be insensitive to the loss of life of those in the WTC, but could you even begin to imagine what would have happened had those towers fell over, instead of compacting?
All of Manhattan would have been in ruins. It could have been much worse than what it is. Not that what happened wasn't disastrous enough.
posted on September 12, 2001 11:19:05 AM
I can't imagine what all the smoke, dust and debris was like. It's too horrifying.
A couple of years back the Hudson's Bldg., a downtown Detroit icon, was gutted and imploded. We watched from the top of a building about 3 miles out. The dust (no smoke with this one) was so bad that you could hardly see the person next to you and that was after it traveled out as far as we were.
The next day we ventured down near the site and the area looked like it had been hit by a nuclear winter.
That building was only 13 floors and as I said was gutted and if I recall one side had been removed before the charges were set. It was really only part of the building.
This is 100's of times worse in a structural sense. I can't fathom it and I am absolutely sure that the news feed we get can't begin to convey the reality of being in the area.
War has come to America, kicked the door in, and boldly ravaged us. I hope we find out who did this and have no mercy on them or their associates.
Our hearts go out to all those involved in the original attacks, their families, and now those who are diligently working to pick up the pieces. To them we wish god-speed and protect.
posted on September 12, 2001 01:06:40 PM
my question is about all of that dust. Since the center was built between 1965 and 1972, didn't they use Asbestos insulation? If they did, isn't all of that dust dangerous?
posted on September 12, 2001 01:09:18 PM
Ann Curry from NBC, speaking from close to the site about an hour ago said it was confirmed there was asbestos used in the buildings. She spoke about how difficult it is to breath at the site, and the plain medical masks many are wearing are not giving near enough protection.
edited for spelling
[ edited by Meya on Sep 12, 2001 01:10 PM ]
posted on September 12, 2001 01:10:42 PM
Asbestos has been mentioned as a concern, I have heard. As well as other types of lung and eye damage from the dust & debris.
posted on September 12, 2001 01:33:08 PM
One thing they've mentioned is a lot of eye damage. The concrete gets pulverized into a fine dust which get trapped in eyes under the lid. This is like rubbing Ajax over your eyeball...they are recommending a LOT of cleaning of eyes from the dust.
posted on September 12, 2001 07:50:55 PM
When several floors collapsed onto the one below, that floor could not hold the weight -- each floor in turn fell on the one below. We have seen this in the past during building construction accidents and the term "pancaking" is appropriate.
Now for the question of loss... the building owners and tenants have suffered severe financial loss, and you may think this is insured against. But the standard insurance policy excludes coverage for "acts of war." And President Bush declared this an act of war.... What do you think the insurance company's positions will be?
posted on September 12, 2001 08:10:50 PM" But the standard insurance policy excludes coverage for "acts of war." And President Bush declared this an act of war.... What do you think the insurance company's positions will be?"
Vinnie, this is an incredibly interesting point!
I had already considered the possibility that the airlines whose planes were involved would probably be sued out of existence, as some will contend (whether rightly or wrongly) that their security was at fault.
Wonder if Dubya's words will hold up in court as a legal defense?
posted on September 12, 2001 08:22:12 PM
In addition to the insurance issue, one thing occupying a lot of NY financial minds is whether deals have to close. Stock/bond offerings price on Day 1 and close 3 business days later. The underwriting agreement commiting to close contains a "market out" clause, which regularly includes war-type language, allowing the underwriters to back away from the deal if certain events occur. Back in '90, this "war" provision was reworked into more fuzzy language -- "escalation of hostilities", etc. Friends of mind in the business have been burning up the phone lines today to figure out what the industry position is going to be. Especially hard to determine, with the markets closed.
posted on September 12, 2001 08:28:51 PM
Not to come across as insensitive to the devastation, but I can't help thinking what the replacement will be. I think I speak for all of us that it hurts on many levels and looking at the skyline feels like we went back in time. They were the crowning jewels and the empty site will be a sad reminder after more time passes. I think part of the healing process to an extent will be parrelled with the construction and completion of a new structure.
What do you think they will do? Replicate the same look or design an entirely new look?
posted on September 12, 2001 08:32:01 PM
I was wondering the same thing(about insurance). I've never seen an insurance policy that didn't have that disclaimer in them! I wanted to ask about it this morning, but didn't want to appear calloused. Same with the airlines. If it is declared an "act of war", I don't know if they can be held liable either.
posted on September 13, 2001 01:28:23 AM
From the coverage that we have seen on MSNBC and CNN the insurance companies came out and said that this event would absolutely be covered. Sorry that I can't remember the names and companies involved but it read like the Who's Who list of the insurance world and I am sure it included Lloyd's of London.
posted on September 13, 2001 02:28:40 AM
Theres a Rider in my Life Insurance Policy that states if I ever get caught in a War Situation and die, they have to cough up the dough. Terrorism...uh, that's a grey area, gotta re-look at my Rider...
:\\\\\\\"Crystalline Sliver cannot be the target of spells or abilities.
posted on September 13, 2001 04:43:50 AM
"I wanted to ask about it this morning, but didn't want to appear calloused. "
I also hesitated to bring up the insurance issue... there are those who will scold any action or discussion other than praying for the victims. But life must go on. This includes buying and selling on ebay, as crass as it may sound - many make their living at that, and while a moment of silence is appropriate, a week or two is not.
posted on September 13, 2001 08:05:46 AM
We were having a discussion here about the insurance issue yesterday since they were bringing up insurance figures. Most policies do have a statement regarding act of war or terrorism. There are policies and coverages specifically for terrorism and I imagine the WTC and the surrounding buildings all had coverage. On the other hand, I doubt that most of the companies occupying the buildings have it on their contents or death benefits for the employees. I would imagine that the huge companies may have had it for their contents but with the economy of recent probably few of the smaller ones did.
posted on September 13, 2001 10:17:33 AM
I think if only one building was hit all 3 would have stood. The Entire complex was shaken but I think it was the second hit and the tremor above and below ground that did all 3 of those buildings in.
Even if they retro-fitted those buildings the codes were not the same as California style retro-fitting today........even the California codes were a different 25 years ago due to simple technology and building techniques.
Someone mentioned asbestos.......the twin towers didn't have any......it was the much older building #7 that they weren't sure about. Newscasters speculated, guessing upon the age of the building that it probably had asbestos. Yet when the EPA came to do their study they didn't not find any traceable amounts of Asbestos in the environment.
Hopefully building #5 will stand.
On a good note......5 firefighters have just been found alive and well.
