Originally posted by bsbray11
Come on, just admit it. The exterior walls were buckling inward.
Uh, no? Come on, Howard: just admit the sky is green.
All I see in those pics are aluminum, lol. I don't know how you can tell what's behind those coverings or in which direction the columns behind them
are leaning. Really, Howard, this is kind of weak to use as evidence against us, don't you think? All you can even freaking see is the
Well, since the aluminum is attached to the columns, it isn't hard to understand that if we see the aluminum bending inward, the columns behind them
must be bending inward also.
Originally posted by bsbray11
And isn't aluminum supposed to melt at 600 degrees Celsius? Oh yeah, wait, since it was on the outside, the air was cooling the aluminum and
preventing it from heating that much. Funny how that apparently did not effect the columns behind the aluminum, right Howie? The columns themselves
apparently must've been heated beyond 1000 degrees nevertheless. And those core columns, despite what must have been a really unhealthy air
circulation within the building, must've been under some extreme office fires as well. And golly gee whiz how those those concrete slabs in between
pulverized so thoroughly into fine powder! And all those magic jets of compressed air, blowing out random windows and spewing forth concrete dust
In spite of your sarcastic tone, that is actually a valid point.
The thing is, those columns are not buckling inward because of the heat applied to them, they are buckling inward because of the heat applied to the
floor slabs. The floor slabs were sagging and falling causing loss of rigidity to the external walls.
You see the floors were a vital part of the structural system. Not only were they floors, but they also provided structural rigidity to the external
walls. Due to the damage to these floors slabs from the impact and the subsequent fires, the floors were no longer providing that rigidity.
In addition, the floor trusses were the most vulnerable to the heat of the fires. Fire proofing is easily knocked off those thin cross sections
allowing the thin truss sections to heat rapidly.
Furthermore, an understanding of how a composite floor works is important. A composite floor is comprised of two parts, the concrete slab and the
truss system underneath. Each material has its own strengths and weaknesses. Steel performs better under tension then it does under compression.
The trusses were designed to maximize this. Concrete, on the other hand is extremely poor at resisting tension forces, but much better at resisting
compressive forces. That is why the composite floor with the concrete on top and the steel on the bottom works so well.
Unfortunately, under fire conditions, this relationship starts to break down. Steel starts to lose its strength and begins to yield and creep (i.e.
it stretches and bends). While concrete loses much of its strength as the water trapped within its matrix turns to steam and starts to spall out.
While steel will regain some of its strength when it cools, concrete will not and will in-fact continue to loose strength.
The issue is not how hot the fire got in any one particular location, but how the structure as a whole responded to the stresses put on it.
of the external walls was due to a number of factors. To some
degree the external columns were affected by the temperature inside the building, but more importantly it was due to the changing structural
conditions inside the building. Yes the fire temperature is related to the collapse, but it is important to understand how this happened. How the
various structural components are related to each other and how when one starts to fail, that effects the others.
Have you found a structural engineer that will support your contentions yet?