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      02-11-2017, 08:01 PM   #37
zx10guy
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Quote:
Originally Posted by insanecoder View Post
Most of the jet fuel blew out..
Besides jet fuel is essentially kerosene.. no kerosene cannot cause steel to melt kerosene burns at 700C max whereas steels melts at double that.

That said temperatures found at WTC exceeded the temperatures of kerosene burn for some strange reason.. which is why many believe it was some other accelerant involved.

Besides, WTC 7 was never doused with jet fuel and it simply completely collapsed in freefall all at once..
http://www.popularmechanics.com/mili...-trade-center/

'"MELTED" STEEL

Claim: "We have been lied to," announces the Web site AttackOnAmerica.net. "The first lie was that the load of fuel from the aircraft was the cause of structural failure. No kerosene fire can burn hot enough to melt steel." The posting is entitled "Proof Of Controlled Demolition At The WTC."

FACT: Jet fuel burns at 800° to 1500°F, not hot enough to melt steel (2750°F). However, experts agree that for the towers to collapse, their steel frames didn't need to melt, they just had to lose some of their structural strength—and that required exposure to much less heat. "I have never seen melted steel in a building fire," says retired New York deputy fire chief Vincent Dunn, author of The Collapse Of Burning Buildings: A Guide To Fireground Safety. "But I've seen a lot of twisted, warped, bent and sagging steel. What happens is that the steel tries to expand at both ends, but when it can no longer expand, it sags and the surrounding concrete cracks."

"Steel loses about 50 percent of its strength at 1100°F," notes senior engineer Farid Alfawak-hiri of the American Institute of Steel Construction. "And at 1800° it is probably at less than 10 percent." NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.

But jet fuel wasn't the only thing burning, notes Forman Williams, a professor of engineering at the University of California, San Diego, and one of seven structural engineers and fire experts that PM consulted. He says that while the jet fuel was the catalyst for the WTC fires, the resulting inferno was intensified by the combustible material inside the buildings, including rugs, curtains, furniture and paper. NIST reports that pockets of fire hit 1832°F.

"The jet fuel was the ignition source," Williams tells PM. "It burned for maybe 10 minutes, and [the towers] were still standing in 10 minutes. It was the rest of the stuff burning afterward that was responsible for the heat transfer that eventually brought them down."
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'WTC 7 COLLAPSE

Claim: Seven hours after the two towers fell, the 47-story WTC 7 collapsed. According to 911review.org: "The video clearly shows that it was not a collapse subsequent to a fire, but rather a controlled demolition: amongst the Internet investigators, the jury is in on this one."


Fire Storm: WTC 7 stands amid the rubble of the recently collapsed Twin Towers. Damaged by falling debris, the building then endures a fire that rages for hours. Experts say this combination, not a demolition-style implosion, led to the roofline "kink" that signals WTC 7's progressive collapse. (Photograph by New York Office of Emergency Management)

FACT: Many conspiracy theorists point to FEMA's preliminary report, which said there was relatively light damage to WTC 7 prior to its collapse. With the benefit of more time and resources, NIST researchers now support the working hypothesis that WTC 7 was far more compromised by falling debris than the FEMA report indicated. "The most important thing we found was that there was, in fact, physical damage to the south face of building 7," NIST's Sunder tells PM. "On about a third of the face to the center and to the bottom—approximately 10 stories—about 25 percent of the depth of the building was scooped out." NIST also discovered previously undocumented damage to WTC 7's upper stories and its southwest corner.

NIST investigators believe a combination of intense fire and severe structural damage contributed to the collapse, though assigning the exact proportion requires more research. But NIST's analysis suggests the fall of WTC 7 was an example of "progressive collapse," a process in which the failure of parts of a structure ultimately creates strains that cause the entire building to come down. Videos of the fall of WTC 7 show cracks, or "kinks," in the building's facade just before the two penthouses disappeared into the structure, one after the other. The entire building fell in on itself, with the slumping east side of the structure pulling down the west side in a diagonal collapse.

According to NIST, there was one primary reason for the building's failure: In an unusual design, the columns near the visible kinks were carrying exceptionally large loads, roughly 2000 sq. ft. of floor area for each floor. "What our preliminary analysis has shown is that if you take out just one column on one of the lower floors," Sunder notes, "it could cause a vertical progression of collapse so that the entire section comes down."

There are two other possible contributing factors still under investigation: First, trusses on the fifth and seventh floors were designed to transfer loads from one set of columns to another. With columns on the south face apparently damaged, high stresses would likely have been communicated to columns on the building's other faces, thereby exceeding their load-bearing capacities.

Second, a fifth-floor fire burned for up to 7 hours. "There was no firefighting in WTC 7," Sunder says. Investigators believe the fire was fed by tanks of diesel fuel that many tenants used to run emergency generators. Most tanks throughout the building were fairly small, but a generator on the fifth floor was connected to a large tank in the basement via a pressurized line. Says Sunder: "Our current working hypothesis is that this pressurized line was supplying fuel [to the fire] for a long period of time."

WTC 7 might have withstood the physical damage it received, or the fire that burned for hours, but those combined factors—along with the building's unusual construction—were enough to set off the chain-reaction collapse.
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