Quote:
Originally Posted by strvs
That was simply not enough to make them collapse. the fires were not hot enough to melt the frames
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The fire doesn't need to be a melting temperature to make the steel
fail. It is a know fenomena that heat makes the steel weaker and it
buckles in consequence. If that happens, the steel columns just bend out of plane. Some WTC pics shown that. When that happens, the remaining load of several dozens of floors up to the impact level suddently begins to be applied to the concrete core columns, way beyond their resistance limit, thus collapsing in a brittle way (i.e. explosivelly).
To be precise, what killed the WTC was the heat that make the
trusses that support the floor system to bucke, thus moving out of their supports, and collapsing like pankakes, accelerating the load into the remaining columns make them fail in a brittle way. Like the firefighters saying
Don't truss on trusses applies here, but no one realized that until very late, maybe because they thought the fire retardant material was still there.
This is all on record. Sorry, no explosive charges or magic melting rays.