I am not an architect but I have a few questions. Maybe you can answer it since you are one.
If steel is affected by fire, how come we have not seen this before? Haven't there been other fires in sky scrapers? What about the steel below the fire area that was not affected by heat?
If the rest of the building comes down from a "pancaking" effect, would it be so even? Why use so much well placed explosives to demolish buildings if this "pancaking" effect is so consistent as evidenced by the three buildings that went down.
If the "pancaking" effect is well known, why not build buildings to withstand it? I am assuming when you say "pancaking" you are saying that everything below is only being barely held up and a sufficient force from above would collapse the building. In other words, if a plane, instead of flying into a building, somehow landed on top of the building, we would have a similar "pancaking" result.