The unusual design of WTC7 is also crucial to the discussion, in that key columns supported extreme loadsas much as 2000 sq. ft. of floor area for each flooras the building straddled an electrical substation. What our preliminary analysis has shown is that if you take out just one column on one of the lower floors, NIST lead investigator Shyam Sunder told
Popular Mechanics, it could cause a vertical progression of collapse so that the entire section comes down. The tower wasnt hit by a plane, but it was severely wounded by the collapse of the North Tower. Which is when the fires started.
2. The North and South Towers of the World Trade Center werent knocked down by planesthey both stood for more than a half-hour after the impacts. But the crashes destroyed support columns and ignited infernos that ultimately weakenednot meltedthe steel structures until the towers could no longer support their own weights (NIST offers a primer
here). Ms. ODonnell fundamentally misstates the case with her use of the word melted: Evidence currently points to WTC7 also collapsing because fires weakened its ravaged steel structure.
Tower 7 housed the citys emergency command center, so there were a number of fuel tanks located throughout the buildingincluding two 6000-gal. tanks in the basement that fed some generators in the building by pressurized lines. Our working hypothesis is that this pressurized line was supplying fuel [to the fire] for a long period of time, according to Sunder. Steel melts at about 2,750 degrees Fahrenheitbut it loses strength at temperatures as low as 400 F. When temperatures break 1000 degrees F, steel loses nearly 50 percent of its strength. It is unknown what temperatures were reached inside WTC7, but fires in the building raged for seven hours before the collapse.
I hardly think what Rosie said comes anywhere close to racism. Much ado over nothing.
