NIST didn't say that they weren't compromised, they said that it wasn't a contributing factor. The building was brought down by the fires that were already burning in there. And it makes me when people say that thermal expansion is bull shit. When you heat something, it expanRAB. Heating up steel support beams or girders can cause them to expand and screw up their connections.
Why are you putting burned in "" marks? It really was on fire
Also, I recant my previous statement about WTC7 fire resistance being rated at 4. It was rated at 2 hours for steel beams, girders, and trusses and 3 hours for columns.
Also, the building was showing signs of collapse the entire day.
http://www.firehouse.com/stateprovince/new-york/captain-chris-boyle
http://www.firehouse.com/stateprovince/new-york/deputy-chief-peter-hayden
The NIST report states that fires were burning pretty much the entire day on floors 6-14, 19-22, and 29-30 with fires on floors 7-9 and 11-13 burning out of control for most of the afternoon. Burning occurred for far longer than the buildings fire sprays were rated for, which was 3 hours for columns. However, in the scheme of fire protection, your building is only as fireproof as the weakest point. After 2 hours for the beams, trusses and girders, the building was fucked.