OK TM..
Let's put it simply...because I'm a simple guy..
Steel melts at 2700 F, but for a building to collapse, it need not get anywhere near that heat. Steel starts to get a red glow at about 800F..and is already less than
half it's strength. Like everything else, habitable buildings are designed with certain load capacities..with the original qualities of the steel intact. When the steel glowing
red it is obviously not considered as a "habitable" building. Heat was probably much higher than 800F, since a fire will generate it's own "draft" simply by the vast amount of
air it will draw into the conflagration, just ask any fireman !
As the burning fuel from the crashed planes flooded the floors, obviously the center of the I-beams will start to sag, dumping remaining fuel down the center of
the structure, starting the heating process centrally on each lower floor. When the first engaged floor finally collapsed, it dropped onto the next, immediately overloading
that floor .etc, gaining speed on the way down. Since each of these floors dropped center first, followed by the outer edges, each floor acted like a giant bellows,
blasting the smoke & fumes out through the windows..explains the puffs at each floor..
These were the tallest buildings in the world, standing among dozens of other super tall class buildings. Actually, the buildings performed exactly as designed, since
from what I have read by architects, such buildings are designed to go straight down is such a conflagration (makes sense and code laws INSIST upon the feature).
The sensational videos featured by conspiracists are a joke..let's use our heads..when I fell a tree, I don't cut it every 4" all the way up the trunk..NO; I just cut
one place down near the base. If I were going to fell a giant building, I would just destroy a floor or two at the base..it would HAVE to come down !
Before you reply..the bright, firey spots the conspiracists point out in their videos, could easily be the "bellows effect " I mentioned, with the blast of air superheating elements within the building..
And yes, when we see professionals destroy a stadium or reasonably large structure, they plant explosives on more than one floor..because most are not built under the "skyscraper code" and they want to MAKE SURE the structure falls inward upon itself.
The one thing not adequately explained by conspiracists..is the Airliners seen to crash by so many thousands in both New York city and Washington, DC..