Posted on 09/11/2001 8:50:45 PM PDT by zeugma
The '45 Empire State Building crash is oft studied in architectural and structural engineering to learn why the building withstood the hit. The plane was a B-24, I believe, but in any case a much smaller craft than the ones which hit the WTC and the Pentagon. The '45 plane's engines did penetrate the building, shooting out the far side and falling to the ground and killing passersby, but most of the plane remained inside the structure for it was made of far more fragile materials than a building. A relative small amount of damage was done to the structure of the building though fire was devastating, especially from flaming gasoline cascading inside.
The fireball that shot from the second WTC tower hit, opposite where the jetliner penetrated, blew out windows and perhaps part of the latticework exterior structure. Flaming fuel probably cascaded down the shafts of elevators and ductwork and stairwells whose fire-protection enclosures would have been destroyed by the explosive crash and ballistic heavy plane parts. These fuel flames, and fires started from them, would have weakened interior structural support beyond protection provided by code-required fireproofing. Once the interior structural supports were weakened, and the exterior lattice lost its integrity collapse was inevitable.
I modify my first evaluation to speculate that the interior supports appear to have given way before the exterior lattice (whose girdle of closely-space columns and thin vertical windows between gave the buildings a unique look compared to use of large panes of glass elswhere) The lattice amazingly contained the interior collapse and the whole mess dropped vertically, almost, as newscasters report, as if executed by a demo expert.
I did not expect the Twin Towers to collapse. To suffer terrible fires and localized interior damage but not total collapse. The first was unbelievable, and as I said, I thought only the portion above the crash fell. Then the smoke cleared momentarily to show the totality. Then the second tower, collapsing in a near-perfect copy of the first. The sudden dropping of the floors above the crash, that impacting load overpowering the remaining system, and the straight drop collapse, neither tower falling much to the side, indicated what had happened.
Close-ups of the exterior show the latticework bridging the crash penetrations, reminding of sales pitches from the 19th Century when cast-iron manufacturers promoted their architecture with structural compoments missing with no apparent destabilization -- the load automatically shifting to remaining components. Their prognostications failed at the first intense fire which overheated and cracked the cast iron, sometimes collapsing more quickly than predecessor masonry bearing wall and wood floor system composites.
Humbling news: My daughter is safe and sound. She heard the first crash and saw the tower blazing on the way to work and thought it was merely (!) a fire. Her office remained at work unaware of what had happened, and was happening, without TV or radio, until telephoned from overseas headquarters which ordered everyone home. At first the office dismissed the alarm, saying, hey, this is New York, no problema, we have work to do, our customers come first, sure that would impress the venal bastards. Then someone was sent outside to check reality.
Nor did I expect it to collapse. It seems the WTC was a government subsidised building, subsidised by the port authority of New York. Thus it was exempt from many building codes such as sprinklers, which would have saved it.
Your remark about the Port Authority was partially true. The PA is a quasi-public agency in which the board of directors is appointed by the governor of New Jersey and the executive director is appointed by the governor of New York. It functions, however, as a private business and as far as I know it does not receive government funding for any of its major projects.
The City of New York gave up the land and gave permission for the PA to build the World Trade Center according to the PA's own building standards. In exchange, the PA agreed to take over the bankrupt Trans-Hudson Railroad (now called the Port Authority Trans-Hudson, or PATH).
Yeah, it shocked the hell out of me, too - and I'm guessing Bin Ladin or whoever it was were equally shocked - and that's really, really, *really* bad news - now they know they can take down a skyscraper with a single flying firebomb.
They got their goblins onto the plane and committed the hijackings without firearms, and succeeded beyond their wildest dreams. They're bound to try again.
I note that the building that was hit by the plane at the lower point collapsed first, even though it was the second one hit. If both terrorist pilots had aimed for lower impact points on the buildings, or had dived into the buildings at sharper angles of attack, they might have collapsed much sooner, causing more loss of life.
So we should be grateful for that, I suppose.
Whoever did this probably had a really good idea that the towers would collapse. I'm sure bin Laden thought that the '93 bomb in the garage would bring it down, but of course that was a scattershot approach... taking down a building like that would require much more structural damage than they did then.
Some twisted nut must have estimated that if you crash a large enough object, you don't even need explosives... the structural damage itself would force structural failure. I think that even without the fires weaking the building, it probably would have given in anyway, albeit much later than it did.
I also think the reason they hijacked cross-continent flights was that they would have much more fuel on board, resulting in a larger explosion. So I'm sure that was a consideration, or why wouldn't they have just hijacked a flight headed for NY anyway, and avoid a bit more suspicion at first?
I also think that they were HOPING for both planes to crash into the towers much closer in time to each other, but we may have had a MAJOR break thanks to airlines typical delays. Fortunately the first plane hit and people in the other building had more time to evacuate. I haven't checked, but I wonder if the flights that hit the towers were scheduled to leave about the same time, and one or the other was late?
Fire pumps shooting tons of water to non-existent lines and gravity tanks on the roof may have indeed contributed to the buildings collapse.
During the explosion and fire and the prolonged evacuation, six people died and 1042 people were injured, though there was a real potential for many more deaths and severe injuries. Many of the injured occupants suffered from smoke inhalation but, remarkably, none died from the exposure. This occurred primarily because there was a limited amount of combustibles that were initially ignited, and because of the basement floor collapse, there was limited fire spread to adjacent materials. Because of the limited burning there was a significant dilution of the products of combustion as they moved through this massive building complex. Had there been a more continuous burning or less dilution of the smoke, it is likely that the loss of life in this tragedy would have been far greater than the six casualties who were directly exposed to the force of the explosion.
The facts of the World Trade Center incident and the lessons learned should serve as an impetus for the fire safety community to re-examine the current design philosophies and future directions for high-rise fire technology. Prior to the incident there was no attempt to treat "mega-high-rises" such as the World Trade Center differently from other high-rise buildings with regard to reliability of fire protection system design. However, since such mega-high-rises can simultaneously expose tens of thousands of people to life-threatening conditions from a "single event," more reliable performance of fire protection components may be appropriate. Further warranting consideration is where the structures contain critical, private enterprises or government agencies, as was the case in the World Trade Center. Although fire protection designers normally would include a "single event" scenario in their performance criteria of fire protection systems, this single event at the World Trade Center complex has initiated an active discussion as to what a "single event" scenario should include.
The NFPA believes fire protection designers and code officials should perhaps broaden their responsibilities to include security issues or other such subtle changes in our society in achieving dependable and reliable fire protection system performance for such critical occupancies.
The complexity of this incident also demonstrates the importance of compliance with fundamental fire protection requirements for high-rise buildings. The growing inventory of high-rise buildings in this country should be reviewed to ensure that minimum levels of fire protection are present. Further, recent fatal high-rise building fires have demonstrated the importance of inspection and maintenance of these systems. One of the more recent high-rise fires resulted in three fire fighters losing their lives, further underscoring the importance of fire safety requirements for these buildings. Finally, owners, insurers, security, fire protection professionals, and code developers may want to re-examine fire protection designs in high-rise structures, especially where those structures accommodate large numbers of people and the economic impact is great, to ensure that the protection systems achieve a high degree of reliability during a "single event" occurrence. The NFPA's Life Safety Code® addresses occupant safety in both new and existing buildings; an important consideration in fundamental fire safety principles in the built environment.
Most steel members were sprayed with fireproofing that wasn't going to last much more than that.
All of the PA engineers and architects were housed in the towers, must have been unable to comunicate with officials in time.
I doubt it...seriously.
Tons of ignited jet fuel vs. sprinklers?
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