Why the second tower collapsed so long after the first.
The National Institute for Standards and Technology (NIST) is investigating the destruction of the World Trade Center towers during the 9/11 unwarned massacre of civilians. (*)
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.
The full NIST report will be released in the coming months. (†)