Quote:
Originally Posted by biskoppen
9/11, what is the official explantion for the molten steel found in all 3 buildings?
The conspiracy guys and their "experts" says that no normal fire could have done it, and the most likely explanation is the socalled nanothermite found on site did it.
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Read up on the difference between tube-frame construction (WTC 1&2) and box-frame construction (very common; ie. Empire State building) ...
In tube-frame construction, trusses span large distances between the core and outer wall. Great for open floor plans, but substantially reduces structural redundancy.
More to the point, steel loses much of its strength well below its melting point. In tube-frame construction, even relatively little bending can cause the trusses to pull away from the outer wall.
With the loss of even a few truss connections, entire floors can collapse adding to the load on the floor below, which in turn gives away, eventually leading to a cascading failure; pancaking of floors on top of each other leaving only the shell remaining (as documented in the pictures / video of the collapse of WTC 1&2).
While one can debate whether the attacks were by the government, terrorists, or whoever ...
the fact is that steel loses much of its strength well below its melting point, which is why in all large commercial structures, the steel is covered in fire retardant insulating material (ie. foams, asbestos, concrete, etc) to keep the steel cool for as long as possible during a fire; critically important in tube-frame construction, because the tolerances and redundancy is far less than that of box-frame construction.
Ron