RG, Here's the NIST's final report on the World Trade Towers 1 & 2:
https://www.nist.gov/publications/final ... ter-towers
You could get real lost here:
https://www.nist.gov/el/final-reports-n ... estigation
The final report on WTC7 is separate. If like me you ever thought the WTC7 collapse was suspect - this report helps:
https://www.nist.gov/publications/final ... e-safety-0
One conclusion is that Towers came down due to fire and not plane impact. About 58,000 people were inside of the Towers when the planes hit. The fact that about 3,000 died is striking. Most deaths occurred at point of plane impact and on floors above. Had the stair towers been stronger the death count might have been even less. Very impressive engineering.
Confession: I was an early "9/11 Truther" I had a very hard time believing those buildings could come down so cleanly without pre-meditated assistance.
NIST Final Reports on WTC1, WTC2, and WTC7
NIST Final Reports on WTC1, WTC2, and WTC7
Last edited by Tom on Tue Sep 28, 2021 10:18 am, edited 4 times in total.
Re: NIST Final Report on WTC1 and WTC2
I wouldn't mention that if I were you. Next you'll acknowledge being an anti-vaxxer . . .!
Osama and whoever else were just extraordinarily lucky---from their perspective---on 9/11, I think. I doubt very much that any of them studied the buildings to assess their structural vulnerabilities and aimed accordingly; the total collapses were a surprise to everyone including the perpetrators. Without going over the reports again, my recollection of the conclusions is that the joists were not adequately connected to the core and/or the exterior walls, and pulled away from them when softened by the heat of the fires, resulting in the pancaking of the floor plates..
In any event, damaged as they initially were, I suspect that the towers would have been demolished in any event. Fewer would have died absent the collapses, perhaps---though not by much, according to the numbers cited above.
An attendant tragedy, more preventable, was the lack of preparation for a response, including especially, as it turned out, an understanding that face masks are a necessity when dealing with heavily polluted air. There is just no excuse for allowing responders to do what they did, without the necessary protection. Numerous heroes are suffering today as a result.
S
Osama and whoever else were just extraordinarily lucky---from their perspective---on 9/11, I think. I doubt very much that any of them studied the buildings to assess their structural vulnerabilities and aimed accordingly; the total collapses were a surprise to everyone including the perpetrators. Without going over the reports again, my recollection of the conclusions is that the joists were not adequately connected to the core and/or the exterior walls, and pulled away from them when softened by the heat of the fires, resulting in the pancaking of the floor plates..
In any event, damaged as they initially were, I suspect that the towers would have been demolished in any event. Fewer would have died absent the collapses, perhaps---though not by much, according to the numbers cited above.
An attendant tragedy, more preventable, was the lack of preparation for a response, including especially, as it turned out, an understanding that face masks are a necessity when dealing with heavily polluted air. There is just no excuse for allowing responders to do what they did, without the necessary protection. Numerous heroes are suffering today as a result.
S
Re: NIST Final Report on WTC1 and WTC2
Yeah, at least I can say for myself that I wasn't a "Truther" for very long. But the WTC7 building bugged me for a longer time until the NIST report.
... and I've got my shots.
... and I've got my shots.
-
Roderick Grant
- Posts: 11815
- Joined: Wed Mar 29, 2006 7:48 am
Re: NIST Final Report on WTC1 and WTC2
911 and 9/11 are two different things.
Re: NIST Final Report on WTC1 and WTC2
Correction noted and made.
Re: NIST Final Reports on WTC1, WTC2, and WTC7
Just learned about this.
Their conclusions disagree with the NIST report on WTC7:
https://ine.uaf.edu/wtc7
Their conclusions disagree with the NIST report on WTC7:
https://ine.uaf.edu/wtc7
-
Roderick Grant
- Posts: 11815
- Joined: Wed Mar 29, 2006 7:48 am
Re: NIST Final Reports on WTC1, WTC2, and WTC7
I'm not an engineer, but I have always doubted that the towers collapsed exclusively because of the impact and fire. The construction of the towers was shoddy. For such immense buildings to have been built on the cheap is a failure of everyone involved in its construction, design and permission.
There is little comparison between 9/11 and the 1945 crash of a B-25 bomber into the Empire State Building, but for the outcomes. We all know about the WTC, but did you know that Empire was up and operating 2 days after the crash? The building was so solidly built that the plane did minimal damage to it. Of course, there was a difference of size of planes and amount of fuel, but if the 9/11 target had been Empire, it probably would not have collapsed.
There is little comparison between 9/11 and the 1945 crash of a B-25 bomber into the Empire State Building, but for the outcomes. We all know about the WTC, but did you know that Empire was up and operating 2 days after the crash? The building was so solidly built that the plane did minimal damage to it. Of course, there was a difference of size of planes and amount of fuel, but if the 9/11 target had been Empire, it probably would not have collapsed.
Re: NIST Final Reports on WTC1, WTC2, and WTC7
Yes, I'm just old enough to remember seeing newsreels of the Empire State Bldg crash ... and early-on initially assumed that the WTC would survive, too., but then I was hearing about the first crash on the radio, early in the morning, AZ time.
We can only wonder what might have happened had a plane hit the Mile High
We can only wonder what might have happened had a plane hit the Mile High
-
Roderick Grant
- Posts: 11815
- Joined: Wed Mar 29, 2006 7:48 am
Re: NIST Final Reports on WTC1, WTC2, and WTC7
As Illinois was designed to be a longsword pointing skyward, with its hilt firmly implanted in the ground, it would have sliced the plane in two.
Re: NIST Final Reports on WTC1, WTC2, and WTC7
"I'm not an engineer, but I have always doubted that the . . ."
Words to remember ?
Words to remember ?
Re: NIST Final Reports on WTC1, WTC2, and WTC7
Comparing a 250mph B-25 striking the gridded steel frame Empire State Building and the 560 mph 767s piercings of the WTCs structural tube are akin to comparing apples and oranges.
The Empire State Building is a 3D cage of redundancy. Its grid of relatively close spaced and similarly sized steel beams and columns enabled it to transfer load from the damaged elements to undamaged ones. The smaller amount of fuel on the B25 reduced the intensity of the fire, and again the nature of the steel grid allowed localized failure without total collapse.
The WTC was constructed as a perimeter “wall” of steel tube columns and spandrel beams with long span bar joists clear spanning from the outer wall to an analogous tube of columns and beams forming a central core that was encased in drywall. The design was predicated on flexibly planned office spaces with no pesky columns with which to contend.
The planes tore through the outer lattice of steel, bent the bar joists of the floors and scoured their spray applied fireproofing off. The hundreds of gallons of kerosene soaked and fueled a fire of paper and fabric unstoppable because the sprinkler risers were cut on impact. The relatively low mass bar joists buckled in the heat, broke loose and when enough had done so, dropped a floor onto one below, overloading it. The domino-like failure of the floors peeled the perimeter wall of steel away like a banana skin...watch the video. The WTC buildings were sound, but they were not capable of withstanding this type of incident due to the lack of redundancy of the structure.
As to the Illinois withstanding an airliner strike: the blade like concrete core walls were to be stout hearted, but the cable stays at the extremities might be the weak tendons.
The Empire State Building is a 3D cage of redundancy. Its grid of relatively close spaced and similarly sized steel beams and columns enabled it to transfer load from the damaged elements to undamaged ones. The smaller amount of fuel on the B25 reduced the intensity of the fire, and again the nature of the steel grid allowed localized failure without total collapse.
The WTC was constructed as a perimeter “wall” of steel tube columns and spandrel beams with long span bar joists clear spanning from the outer wall to an analogous tube of columns and beams forming a central core that was encased in drywall. The design was predicated on flexibly planned office spaces with no pesky columns with which to contend.
The planes tore through the outer lattice of steel, bent the bar joists of the floors and scoured their spray applied fireproofing off. The hundreds of gallons of kerosene soaked and fueled a fire of paper and fabric unstoppable because the sprinkler risers were cut on impact. The relatively low mass bar joists buckled in the heat, broke loose and when enough had done so, dropped a floor onto one below, overloading it. The domino-like failure of the floors peeled the perimeter wall of steel away like a banana skin...watch the video. The WTC buildings were sound, but they were not capable of withstanding this type of incident due to the lack of redundancy of the structure.
As to the Illinois withstanding an airliner strike: the blade like concrete core walls were to be stout hearted, but the cable stays at the extremities might be the weak tendons.
Re: NIST Final Reports on WTC1, WTC2, and WTC7
Back to reality - alas.
You got a view on WTC7?
I lean toward the Hulsey Report out of Fairbanks.
You got a view on WTC7?
I lean toward the Hulsey Report out of Fairbanks.
Re: NIST Final Reports on WTC1, WTC2, and WTC7
WTC7?
Tons of burning debris from the collapse of the 1&2 towers pierced the envelope of WTC7 and started it on fire, particularly on its lower floors. The combination of the broken sprinkler risers in the main towers and the ruptured water lines due to the collapse of WTC1&2 caused the sprinkler system in WTC7 to be ineffective due to low water pressure. The evacuation of the site due to the collapse and the loss of life of those would have otherwise fought the fire, allowed a fire to burn unabated for over 6 hours.
Fireproofing applied to structural steel framing has its limits...4 to 6 hours tops in a raging fire. It is assumed by the designers and engineers that the sprinkler system will work and that a fire will be fought by the fire department. No one could have imagined that 40-some story building in NYC would be left to burn from 10AM to after 5PM with little or no intervention. The fireproofing eventually baked off, the steel softened, and it gave way.
WTC7 was in effect the largest and most costly UL burn test of the steel framed building.
A 40 story building here in Philadelphia suffered a fire on several upper floors in the 1990's due to improper disposal of linseed oil soaked rags at the end of a work week on the construction of a large law office interior. The sprinklers had been shut down on the construction floors to allow for repositioning of heads. The fire raged for almost 10 hours with significant loss of life of firefighters. The fire was brought under control only when the fire breached the upper most floor of the construction area and triggered the operable sprinklers above the construction floors. The building sat empty for several years while the insurance companies duked it out. In the meantime, the building had to be braced due to damage to the structural steel. The building was eventually demolished entirely and replaced.
Tons of burning debris from the collapse of the 1&2 towers pierced the envelope of WTC7 and started it on fire, particularly on its lower floors. The combination of the broken sprinkler risers in the main towers and the ruptured water lines due to the collapse of WTC1&2 caused the sprinkler system in WTC7 to be ineffective due to low water pressure. The evacuation of the site due to the collapse and the loss of life of those would have otherwise fought the fire, allowed a fire to burn unabated for over 6 hours.
Fireproofing applied to structural steel framing has its limits...4 to 6 hours tops in a raging fire. It is assumed by the designers and engineers that the sprinkler system will work and that a fire will be fought by the fire department. No one could have imagined that 40-some story building in NYC would be left to burn from 10AM to after 5PM with little or no intervention. The fireproofing eventually baked off, the steel softened, and it gave way.
WTC7 was in effect the largest and most costly UL burn test of the steel framed building.
A 40 story building here in Philadelphia suffered a fire on several upper floors in the 1990's due to improper disposal of linseed oil soaked rags at the end of a work week on the construction of a large law office interior. The sprinklers had been shut down on the construction floors to allow for repositioning of heads. The fire raged for almost 10 hours with significant loss of life of firefighters. The fire was brought under control only when the fire breached the upper most floor of the construction area and triggered the operable sprinklers above the construction floors. The building sat empty for several years while the insurance companies duked it out. In the meantime, the building had to be braced due to damage to the structural steel. The building was eventually demolished entirely and replaced.
Re: NIST Final Reports on WTC1, WTC2, and WTC7
I accept the official reports from NIST on the failure of WTC1 and WTC2.
... I also accept that an unattended 4-6 hour fire could bring down a 44 story tall building (although in the immediate moment I can't remember how hot the temperature needs to be and for how long it needs to maintain in order to bend steel). What seems unintuitive about the WTC7 collapse and that explanation, however, is just how precisely the tower fell: into its footprint in 7 seconds no tipping, no gradual elastic stretching or bending - just boom.
... I also accept that an unattended 4-6 hour fire could bring down a 44 story tall building (although in the immediate moment I can't remember how hot the temperature needs to be and for how long it needs to maintain in order to bend steel). What seems unintuitive about the WTC7 collapse and that explanation, however, is just how precisely the tower fell: into its footprint in 7 seconds no tipping, no gradual elastic stretching or bending - just boom.