Originally posted by zeeblebotJust outta curiosity I looked up the melting point of steel, which is 1370 C (http://education.jlab.org/qa/meltingpoint_01.html) and the maximun burning temperature for jet fuel, the kind used in the airplanes that his the WTC, is 980 C (http://en.wikipedia.org/wiki/Jet_fuel). Just wondering what the deal is with that.
if they could only find "75 top professors", the probabibility of it's being true is nil.
Originally posted by pizzinteait didn't have to melt. it just had to get soft enough to not be able to support the structure. and it was a huge structure.
Just outta curiosity I looked up the melting point of steel, which is 1370 C (http://education.jlab.org/qa/meltingpoint_01.html) and the maximun burning temperature for jet fuel, the kind used in the airplanes that his the WTC, is 980 C (http://en.wikipedia.org/wiki/Jet_fuel). Just wondering what the deal is with that.
http://en.wikipedia.org/wiki/Jet_engine#Cooling_systems
"Cooling systems
All jet engines require high temperature gas for good efficiency, typically achieved by combusting hydrocarbon or hydrogen fuel. Combustion temperatures can be as high as 3500K (5000F), above the melting point of most materials.
Cooling systems are employed to keep the temperature of the solid parts below the failure temperature.
"
One fact left untouched by the conspiracy theorists is this: The failure of the outer supports was caused by the horizontal struts not pancaking but drooping because of the heat, causing the outer struts to bend inward about 5 feet and finally snapped. That is what triggered the downfall. The first theory from the safety people is the pancake thing but they found out the horizontal struts were still connected, they did not break, they caused the outer struts to break by bending them way in. That was caught on detailed analysis of the video's obtained from the scene.
Originally posted by zeeblebotNot only that but the blown on insulation was inferior quality to what could have been used. It blew off and exposed bare steel. If the insulation had stayed intact (there are kinds that are much more robust), the metal supports would not have melted.
it didn't have to melt. it just had to get soft enough to not be able to support the structure. and it was a huge structure.
Originally posted by sonhouseThey didn't melt.
Not only that but the blown on insulation was inferior quality to what could have been used. It blew off and exposed bare steel. If the insulation had stayed intact (there are kinds that are much more robust), the metal supports would not have melted.
I found this site helpful here are some quotes.
http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html
" However, it is highly unlikely that the steel at the WTC experienced temperatures above the 750–800°C range. All reports that the steel melted at 1,500°C are using imprecise terminology at best"
"It is known that structural steel begins to soften around 425°C and loses about half of its strength at 650°C.4 This is why steel is stress relieved in this temperature range. But even a 50% loss of strength is still insufficient, by itself, to explain the WTC collapse. It was noted above that the wind load controlled the design allowables. The WTC, on this low-wind day, was likely not stressed more than a third of the design allowable, which is roughly one-fifth of the yield strength of the steel. Even with its strength halved, the steel could still support two to three times the stresses imposed by a 650°C fire."
"Thus, the failure of the steel was due to two factors: loss of strength due to the temperature of the fire, and loss of structural integrity due to distortion of the steel from the non-uniform temperatures in the fire."
if the FAQ is not enough, there are 43 volumes in the report to look through ...
http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm
"National Institute of Standards and Technology (NIST) Federal Building and Fire Safety Investigation of the World Trade Center Disaster
Answers to Frequently Asked Questions
(NIST NCSTAR throughout this document refers to one of the 43 volumes that comprise NIST’s final report on the WTC Towers issued in October 2005. All sections of the report listed in this document are available at http://wtc.nist.gov.)
1. If the World Trade Center (WTC) towers were designed to withstand multiple impacts by Boeing 707 aircraft, why did the impact of individual 767s cause so much damage?
..."
" ...
NIST conducted an extremely thorough three-year investigation into what caused the WTC towers to collapse, as explained in NIST’s dedicated Web site, http://wtc.nist.gov. This included consideration of a number of hypotheses for the collapses of the towers.
Some 200 technical experts—including about 85 career NIST experts and 125 leading experts from the private sector and academia—reviewed tens of thousands of documents, interviewed more than 1,000 people, reviewed 7,000 segments of video footage and 7,000 photographs, analyzed 236 pieces of steel from the wreckage, performed laboratory tests and sophisticated computer simulations of the sequence of events that occurred from the moment the aircraft struck the towers until they began to collapse. "
"Based on this comprehensive investigation, NIST concluded that the WTC towers collapsed because: (1) the impact of the planes severed and damaged support columns, dislodged fireproofing insulation coating the steel floor trusses and steel columns, and widely dispersed jet fuel over multiple floors; and (2) the subsequent unusually large jet-fuel ignited multi-floor fires (which reached temperatures as high as 1,000 degrees Celsius) significantly weakened the floors and columns with dislodged fireproofing to the point where floors sagged and pulled inward on the perimeter columns. This led to the inward bowing of the perimeter columns and failure of the south face of WTC 1 and the east face of WTC 2, initiating the collapse of each of the towers. Both photographic and video evidence—as well as accounts from the New York Police Department aviation unit during a half-hour period prior to collapse—support this sequence for each tower.
NIST’s findings do not support the “pancake theory” of collapse, which is premised on a progressive failure of the floor systems in the WTC towers (the composite floor system—that connected the core columns and the perimeter columns—consisted of a grid of steel “trusses” integrated with a concrete slab; see diagram below). Instead, the NIST investigation showed conclusively that the failure of the inwardly bowed perimeter columns initiated collapse and that the occurrence of this inward bowing required the sagging floors to remain connected to the columns and pull the columns inwards. Thus, the floors did not fail progressively to cause a pancaking phenomenon.
"
"NIST’s findings also do not support the “controlled demolition” theory since there is conclusive evidence that:
the collapse was initiated in the impact and fire floors of the WTC towers and nowhere else, and;
the time it took for the collapse to initiate (56 minutes for WTC 2 and 102 minutes for WTC 1) was dictated by (1) the extent of damage caused by the aircraft impact, and (2) the time it took for the fires to reach critical locations and weaken the structure to the point that the towers could not resist the tremendous energy released by the downward movement of the massive top section of the building at and above the fire and impact floors.
Video evidence also showed unambiguously that the collapse progressed from the top to the bottom, and there was no evidence (collected by NIST, or by the New York Police Department, the Port Authority Police Department or the Fire Department of New York) of any blast or explosions in the region below the impact and fire floors as the top building sections (including and above the 98th floor in WTC 1 and the 82nd floor in WTC 2) began their downward movement upon collapse initiation.
In summary, NIST found no corroborating evidence for alternative hypotheses suggesting that the WTC towers were brought down by controlled demolition using explosives planted prior to Sept. 11, 2001. NIST also did not find any evidence that missiles were fired at or hit the towers. Instead, photographs and videos from several angles clearly show that the collapse initiated at the fire and impact floors and that the collapse progressed from the initiating floors downward until the dust clouds obscured the view.
3. How could the WTC towers have collapsed without a controlled demolition since no steel-frame, high-rise buildings have ever before or since been brought down due to fires? Temperatures due to fire don't get hot enough for buildings to collapse.
The collapse of the WTC towers was not caused either by a conventional building fire or even solely by the concurrent multi-floor fires that day. Instead, NIST concluded that the WTC towers collapsed because: (1) the impact of the planes severed and damaged support columns, dislodged fireproofing insulation coating the steel floor trusses and steel columns, and widely dispersed jet fuel over multiple floors; and (2) the subsequent unusually large, jet-fuel ignited multi-floor fires weakened the now susceptible structural steel. No building in the United States has ever been subjected to the massive structural damage and concurrent multi-floor fires that the towers experienced on Sept. 11, 2001.
4. Weren't the puffs of smoke that were seen, as the collapse of each WTC tower starts, evidence of controlled demolition explosions?
No. As stated in Section 6.14.4 of NIST NCSTAR 1, the falling mass of the building compressed the air ahead of it—much like the action of a piston—forcing smoke and debris out the windows as the stories below failed sequentially.
These puffs were observed at many locations as the towers collapsed. In all cases, they had the appearance of jets of gas being pushed from the building through windows or between columns on the mechanical floors. Such jets are expected since the air inside the building is compressed as the tower falls and must flow somewhere as the pressure builds. It is significant that similar “puffs” were observed numerous times on the fire floors in both towers prior to their collapses, perhaps due to falling walls or portions of a floor. Puffs from WTC 1 were even observed when WTC 2 was struck by the aircraft. These observations confirm that even minor overpressures were transmitted through the towers and forced smoke and debris from the building.
5. Why were two distinct spikes—one for each tower—seen in seismic records before the towers collapsed? Isn't this indicative of an explosion occurring in each tower?
The seismic spikes for the collapse of the WTC Towers are the result of debris from the collapsing towers impacting the ground. The spikes began approximately 10 seconds after the times for the start of each building’s collapse and continued for approximately 15 seconds. There were no seismic signals that occurred prior to the initiation of the collapse of either tower. The seismic record contains no evidence that would indicate explosions occurring prior to the collapse of the towers.
"