A preliminary report by the Commerce Departmentís National Institute of Standards and Technology (NIST) on the technical reasons why the World Trade Center towers collapsed so quickly has dramatic police photos of the floors buckling two minutes before the collapse.
The report notes that the buildings could have withstood the impacts and subsequent burning of jet fuel (which was exhausted in a few minutes). However, the office fixture fire fed by roaring winds from the holes in the wall was so hot that it melted the supports on the impacted floors as some of the fire retardant covering on the steel was ripped off by the impact.
Perimeter columns were pulled inward by the sagging floors and buckled. A report in June will make specific recommendations which may dramatically how skyscrapers are built (including requirements that steel not melt as easily).
The above photo shows the columns buckling inward two minutes before the collapse.
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