Why is it that no highrise steel building had ever collapsed due to fire damage before and after 9/11?

Ohi hasn't a clue. Those miscreants flying the three airplanes, had taken hours of flight training before doing their cowardly deeds. In fact, that's one of the several indicators our so-called intelligence community failed to pick up on; otherwise, the 9/11 events might have been prevented.

As a retired Naval Aviator, I can assert that it does not take much skill and training to simply guide an airplane; and that's all the terrorists had to do.... guide them. The intense heat of aviation fuel, all the planes were topped off as they had just taken off, buckled the supporting steel frame of the towers and allowed the rebar cement slabs of each floor to drop through onto the floors below. So the aviation fuel fire started the collapse when the steel girders expanded and warped under that heat.

Remember jet fuel (JP4 or JP5) has a high heat content; it's developed that way to propel the big jets. The more the heat content, the more the thrust. That started a chain reaction of floors dropping on floors below, which undermined each of the two towers.

If you pay attention to the many videos of their collapse, you can clearly see the floors dropping one on top of the other so the floors below had more load than they could handle. And they, too, collapsed, from the load, not from the fire. As you have rejected every report by several agencies and private investigations, why bother to ask this question except to start an argument.

And that's not the purpose of the physics category of Answers.

It is called a jack-hammer effect. When the floors directly affected by the heat collapsed, the full weight of all of the floors above the fire rammed downward with so much force, that it collapsed the next floor, then the next, then the next. The structure of each floor is much more than is needed to support the building above it, but not when that structure is already moving and accelerating under the force of gravity.

Remember that it was not just the floors affected that were moving down. It was all of the floors above them too.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.