![]() I understand the dynamics of a building "pancaking" very well and that is exactly what occurred. If the water mains in the street had not been broken by falling parts of the WTC 1 building then maybe the sprinkler Pressurized tanks in the basement feeding the generators on the fifth floor.They were found empty when the debris was cleared. There was over 43,000 gal of diesel fuel inside the building to power a number of emergency generators,with 12,000 gal in two It does not have to melt to be unable to support its load ,550 C reduces strength by 50%.The fires had been raging for six hours,plenty of time to cause steel failure. #18 You are hopeless and evidently know nothing of how steel loses its strength when subjected to high heat. Finally, the entire façade collapsed.Īccording to the NIST report, a key factor leading to the eventual collapse of WTC 7 was thermal expansion of long-span floor systems which are no longer used in buildings because of this incident. Then, progressing from east to west across WTC 7, all of the columns in the core of the building failed. Failure first occurred all the way to the roof line involving all three interior columns on the most eastern side of the building. What followed in rapid succession was a progression of structural failures. When this critical column buckled due to lack of floor supports, it was the first domino in the chain. This collapse of floors left the critical column unsupported over nine stories. Many of these floors had already been at least partially weakened by the fires in the vicinity of the critical column. The displaced girder and other local fire-induced damage caused Floor 13 to collapse, beginning a cascade of floor failures down to the fifth floor. ![]() Eventually, a girder on Floor 13 lost its connection to a critical interior column that provided support for the long floor spans on the east side of the building. The heat from these uncontrolled fires caused thermal expansion of the steel beams on the lower floors of the east side of WTC 7, damaging the floor framing on multiple floors. #12 OK, Determining the probable collapse sequence for WTC 7, NIST found that the impact of debris from the collapse of WTC 1 ignited fires on at least 10 floors of WTC 7, and the fires burned out of control on six lower floors. ![]()
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