Mick
Here is some logic for you.
Temperature required to produce significant strength reduction in steel is about 600C (check it out)
That equates to cherry red.
Can you raise a large mass of steel and concrete to that temperature using the fuel sources available.
An opinion from a fire investigation expert would be most helpful.
He who provides the most links doesn't win the war.
You will probably reject any information that does not confirm your entrenched viewpoint. That is human nature.
Perhaps I'm not human.
I like to modify my viewpoint as information comes to hand.
Most of the websites have a one eyed view pro or anti.
It is your right to accept or reject the information.
I do not question your ancestry or intelligence because you see things from a different perspective to me.