Posted on 10/21/2004 6:38:52 PM PDT by snopercod
Structural steel of the twin 110-story towers of the World Trade Center was stripped of its fireproofing by debris from the aircraft impact and weakened by the resulting fires, eventually causing the towers to collapse, according to an interim report by the National Institute of Standards & Technology. The report says the region of dislodged fireproofing was determined from the predicted path of the debris.
“Had the fireproofing not been dislodged, the temperature rise of the structural components would likely have been insufficient to cause the global collapse of the towers,” says NIST in the Oct. 19 release of another interim report of its $16-million study of the WTC destruction on Sept. 11, 2001, by terrorists. “Fireproofing dislodged by debris left the components more sensitive to heat than any areas where there was missing or thin fireproofing before the aircraft impacts,” says the report.
Many experts familiar with the twin towers design are not surprised by the findings. But they are worth noting, say sources, because there are others, both structural engineers and fire experts, who have questioned whether the design by Skilling Helle Christiansen Robertson in some way contributed to the collapse.
According to S. Shyam Sunder, NIST’s lead investigator for the study, an ordinary office fire would likely have resulted in burn-out, not collapse. advertisement ...
In addition, NIST has determined that the majority of the steel was stronger than minimum requirements. “The safety of the towers was most likely not affected by the small percentage of steel below the minimum,” says the report. “Building designs routinely allow structures to withstand greater loads than are expected by including significant factors of safety. Moreover, the structural loads on Sept. 11, 2001, were well below this design level. “
In fire tests in August, NIST also determined that the floor systems in the towers met the New York City building code of the time (ENR 9/13 p. 16).
The findings include an explanation for the time delay between the collapses of the two towers. (The south tower, Two WTC, survived for 56 minutes; the north tower, One WTC, for 103 minutes). NIST says the difference was primarily due to five items: the asymmetrical structural damage of the aircraft impact to Two WTC compared to the aircraft damage to One WTC; the time it took for heat to soften, buckle and shorten core columns that had fireproofing dislodged by debris impact; the structure’s ability to redistribute loads as the core columns shortened; the time it took for fires to traverse from their initial location to the face of the towers where perimeter columns were bowing inward (as seen only minutes before the collapse of each tower); and the time it took for heat to soften and buckle those columns.
NIST plans to release its final draft of the twin towers’ report in December or January. A four to six-week public comment period will follow. The final release is expected in May. The draft report on Seven WTC is set to be released in May. The final report is expected out in July.
This was the initial findings of the 2002 investigation as well. Makes sense.
Relatively few ordinary office fires are ignited by Boeing 757s crashing at 500 MPH.
While they were designed against fire, nobody could have thought about what the buildings would do when soaked in jet fuel burning for hours.
The trial lawyers say that the architects should have forseen this possiblity and therefore were negligent.
The World Trade Center's support columns were destroyed by the airplane crash and the resulting fire, which further damaged the building. No building cannot survive both an airplane crash and the resulting fire from jet fuel. It burns at a high temperature. Sadly, the World Trade Center is gone.
I wish they would rebuild them exactly as before. The replacement is a monstrosity.
Same here.
Even though the Boeing 757 did not exist when the WTC was designed. Trial lawyers are criminals and everybody else is the victim.
I saw a show on the History Channel which dealt with the building of the towers, and, if memory serves me correctly, impact from a 737 was included in the design parameters.
Good catch. The loss of the space shuttle Challenger (as well as several military Titan rockets) is directly attributable to the removal of Asbestos from the SRB joint putty.
Exactly. Trail lawyers do as much damage to this country as any enemy. They are the enemy within. I despise all trial lawyers -- they have NO soul. There arrogance is only exceeded by their evilness.
Another problem was that when the second tower was hit, the water demand from the sprinkler systems in the two buildings kept either sprinkler system from working properly.
Elect John Edwards and get more sensible thinking like this into higher places! /sarcasm
Yet another problem was that the drywall which surrounded the stairwells was breached by the impact of debris from the crash, allowing smoke and flames into the stairwells which prevented people above the impact from getting out.
I don't know what the thickness or type of drywall used in the WTC was, but I do know that the standard today is two 1" thick pieces of drywall, which provide a 2-hour fire rating. This type of construction is also used for elevator shafts and is now (since the early 80s at least) used for the party wall in townhouses, as opposed to the masonry walls that were used prior.
Who would have ever considered that both towers would need water at the same time?
The fires they actually encountered were, obviously, far beyond that. Furthermore, it was expected that the water would have been spraying out through the sprinkler nozzles; instead, it was most likely gushing torrentially out through mains that had been "rent asunder" by the impact.
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