Myth No. 2: The “official story” concludes that fires set off by the jet fuel and initial explosions of the aircraft entering the World Trade Center towers caused the steel structure to weaken and eventually fail. But “no large, steel-frame, fire-protected building had ever collapsed before due solely to fire,” is how the book “Debunking 9/11 Myths” restates the idea. Theorists conclude it must have been controlled demolition that led to collapse.
Fact: Each plane was carrying thousands of pounds of jet fuel, which burns at 2,190 degrees Fahrenheit, a great deal lower than the temperature required to melt steel (2,750).
Experts and investigations conclude that steel didn’t have to melt to cause collapse. Instead, the planes entering the buildings at 750 feet per second caused significant damage. They were banked at an angle that took out multiple floors upon impact and likely stripped the fireproofing from the core load-bearing structures on those floors. Jet fuel then ignited everything inside the buildings.
Steel weakens at as low as 400 degrees. At 980, it’s at only 10 percent strength, according to industry experts. As the core steel columns weakened, load-bearing was transferred to the building’s shell. As the fires continued to burn, multiple floors weakened, sagged, and pulled on the outside structure causing total collapse.
The jet fuel followed the path of least resistance, incidentally, which means some of it flowed down the elevator shafts from the top of the building, causing explosions and fireballs on lower floors, which conspiracy theorists sometimes cite as evidence of bombs.
Myth No. 3: World Trade Center 7 could not possibly have collapsed due only to collateral damage sustained from the Towers’ collapse. That was controlled demolition, too.
Fact: An early FEMA report puzzled over the collapse of WTC 7 because it appeared to have sustained little structural damage and been brought down by fire alone. Truthers latch onto the early FEMA report as proof, but further investigation has found that one face of the building had damage to 10 lower stories. That damage was obscured by smoke in most photographic evidence.
There are also a number of idiosyncrasies in the building’s design that contributed. It was built over a power substation, which meant the relatively few columns on the lower floors were designed to carry extremely large loads. Taking out just one would have caused serious problems. WTC 7 was designed to stay operational during power outages, so several fuel tanks for generators inside the building are thought to have supplied the fires with fuel for up to seven hours.