Kills On Site wrote:Well IIRC I believe the steel beams were fire proofed with a spray on substance that when the plane hit the force blew the fire proofing away.
Nightshade wrote:I've read engineering analyses that say the same. Seen metallurgists state that the examined samples of the structural steel that was thinned by fire so hot it VAPORIZED metal away.
The big problem with the "woman standing in the hole" bit is that it doesn't prove anything. The structural steel was all near the center of the building, so she wasn't touching any of it. Also what floor was she on? Was it purported to be that same floor as the collapse began?
No, there was definitely fireproofing on all the steel beams. I'm talking about the flammable material between floors in the plenum/conduit areas where cables were run with no fireproofing. Also, there weren't any sprinklers installed at the time.
I was drastically wrong about the time the first fire burned though - it burned for 3 hours:
This 110-story steel-framed office building suffered a fire on the 11th floor on February 13, 1975. The loss was estimated at over $2,000,000. The building is one of a pair of towers, 412 m in height. The fire started at approximately 11:45 P.M. in a furnished office on the 11th floor and spread through the corridors toward the main open office area. A porter saw flames under the door and sounded the alarm. It was later that the smoke detector in the air-conditioning plenum on the 11th floor was activated. The delay was probably because the air-conditioning system was turned off at night. The building engineers placed the ventilation system in the purge mode, to blow fresh air into the core area and to draw air from all the offices on the 11th floor so as to prevent further smoke spread. The fire department on arrival found a very intense fire. It was not immediately known that the fire was spreading vertically from floor to floor through openings in the floor slab. These 300-mm x 450-mm (12-in. x 18-in.) openings in the slab provided access for telephone cables. Subsidiary fires on the 9th to the 19th floors were discovered and readily extinguished. The only occupants of the building at the time of fire were cleaning and service personnel. They were evacuated without any fatalities. However, there were 125 firemen involved in fighting this fire and 28 sustained injuries from the intense heat and smoke. The cause of the fire is unknown.
Also, from the New York Times (Saturday 15th February 1975):
Fire Commissioner John T. O'Hagan said yesterday that he would make a vigorous effort to have a sprinkler system installed in the World Trade Center towers as a consequence of the fire that burned for three hours in one of them early yesterday morning.
The towers, each 110 stories tall and the highest structures in the city, are owned and operated by the Port Authority of New York and New Jersey, which is not subject to local safety codes.
As Commissioner O'Hagan stood in the sooty puddles of the North Towers's 11th floor hallway, he told reporters that the fire would not have spread as far as it did if sprinklers had been installed there.
The fire spread throughout about half of the offices of the floor and ignited the insulation of telephone cables in a cable shaft that runs vertically between floors. Commissioner O'Hagan said that the absence of fire-stopper material in gaps around the telephone cables had allowed the blaze to spread to other floors within the cable shaft. Inside the shaft, it spread down to the 9th floor and up to the 16th floor, but the blaze did not escape from the shaft out into room or hallways on the other floors.
........
Only the 11th floor office area was burned, but extensive water damage occurred on the 9th and 10th floors, and smoke damage extended as far as the 15th floor, the spokesman said.
Although there were no direct casualties, 28 of the 150 firemen called to the scene suffered minor injuries.
More from the New York Times (Saturday 14th February 1975):
"It was like fighting a blow torch" according to Captain Harold Kull of Engine Co. 6,
As far as your comment that only the center beams needed to get hot on those floors in order for the collapse to happen, I don't really see how that's possible with the pancake theory. If the floors were still strongly attached to the outer perimeter beams, then only the centers of 2 or 3 floors would have fallen to the floors below. Having them still sturdily attached to the outer beams would have prevented a complete floor collapse. That, added to the resistance of the floors below, surely would have allowed the entire building to collapse. The center core was definitely where a majority of the structural support came from, but all the steel in the perimeter of the building was also tested and rated to support 5 times the weight it needed to in normal circumstances.
