The floors were each an acre of 4" thick concrete. That may have made a dent? There was more concrete in a WTC floor than there was in the block in the phantom test - and the plane must have hit at least two of them.
110 floors, 4" thick so around 36 acre feet of concrete. And wasn't there some steel in there, too?
What did hold the building up? The steel box sections were made out of 5" thick steel at the base.
The outer walls were load-bearing and so WERE essential to the structure.
The other point about "physics" is that, presumably, this is a well-understood and well-known effect? Can you find another instance anywhere in the world where a steel-framed, high-rise building collapsed into its own footprint at free-fall speed due to a fire?
I recall the floors as concrete-clad steel trusses. The acted as blades to slice up the airplane as it penetrated into the building. So also with the columns. I've seen a rather appalling computer simulation of the 767 heading into the building as though it were a potato being diced.
The airplane did not encounter 110 floors, so I don't know what that has to do with the situation.
The vertical columns held the building up. Loss of strength would mean catastrophic collapse.
Yes, there were columns in the exterior wall, but between the columns was mostly window. It wasn't at all like a thick reinforced concrete wall. You really ought to read up on the 1945 B-25 / Empire State Building collision, only suggestive of the greater damage caused by a high speed 767. https://en.wikipedia.org/wiki/1945_Empire_State_Building_B-25_crash
The exterior walls were mostly glass. That is the style of modern skyscrapers. They were not significantly concrete. The exterior wall had steel columns...among all the others in the core, which were holding up all that weight. There is utterly no mystery about this and I don't understand why I have to explain this to you like you are a child. Did I not give you the reference to the B-25 collision with the Empire State Building?---which was a much less serious event.
As for the building "still standing," I didn't catch that except on second reading. What possibly can that prove? We normally expect (for example) that automotive head-on collisions are terrible affairs with loss of life and mangled vehicles. But I was in one where I was essentially unhurt and my car had mainly cosmetic damage. So also, the other party. You can't draw rules from discrete events. There was nothing else like the Twin Towers event so far as I am aware. And the "still standing" building was only about 20-25 stories. The photo shows the fire department working to abate the fire. No possibility of that at the height of the Twin Towers collision. You are not making a logical comparison. The majority of professional opinion was that the collapse was understandable. As an engineer, I find it understandable. What more do you want? You don't seem to be approaching this as an engineer, or as one familiar with structures.
WTC7 also collapsed from columnar failure from an internal fire (innards first and walls last).
The floors were each an acre of 4" thick concrete. That may have made a dent? There was more concrete in a WTC floor than there was in the block in the phantom test - and the plane must have hit at least two of them.
110 floors, 4" thick so around 36 acre feet of concrete. And wasn't there some steel in there, too?
What did hold the building up? The steel box sections were made out of 5" thick steel at the base.
The outer walls were load-bearing and so WERE essential to the structure.
The other point about "physics" is that, presumably, this is a well-understood and well-known effect? Can you find another instance anywhere in the world where a steel-framed, high-rise building collapsed into its own footprint at free-fall speed due to a fire?
This one, for instance, is still standing.
I recall the floors as concrete-clad steel trusses. The acted as blades to slice up the airplane as it penetrated into the building. So also with the columns. I've seen a rather appalling computer simulation of the 767 heading into the building as though it were a potato being diced.
The airplane did not encounter 110 floors, so I don't know what that has to do with the situation.
The vertical columns held the building up. Loss of strength would mean catastrophic collapse.
Yes, there were columns in the exterior wall, but between the columns was mostly window. It wasn't at all like a thick reinforced concrete wall. You really ought to read up on the 1945 B-25 / Empire State Building collision, only suggestive of the greater damage caused by a high speed 767. https://en.wikipedia.org/wiki/1945_Empire_State_Building_B-25_crash
Have you looked at the vast expanse of glass in WTC1 and WTC2?
Thought not.
As for the 110 floors, something was holding up all that weight. Whatever it was was not trivial in the strength department.
The exterior walls were mostly glass. That is the style of modern skyscrapers. They were not significantly concrete. The exterior wall had steel columns...among all the others in the core, which were holding up all that weight. There is utterly no mystery about this and I don't understand why I have to explain this to you like you are a child. Did I not give you the reference to the B-25 collision with the Empire State Building?---which was a much less serious event.
As for the building "still standing," I didn't catch that except on second reading. What possibly can that prove? We normally expect (for example) that automotive head-on collisions are terrible affairs with loss of life and mangled vehicles. But I was in one where I was essentially unhurt and my car had mainly cosmetic damage. So also, the other party. You can't draw rules from discrete events. There was nothing else like the Twin Towers event so far as I am aware. And the "still standing" building was only about 20-25 stories. The photo shows the fire department working to abate the fire. No possibility of that at the height of the Twin Towers collision. You are not making a logical comparison. The majority of professional opinion was that the collapse was understandable. As an engineer, I find it understandable. What more do you want? You don't seem to be approaching this as an engineer, or as one familiar with structures.
WTC7 also collapsed from columnar failure from an internal fire (innards first and walls last).
But you also said:
Sounds mysterious to me. Structural or not structural?
I am still trying to find all that glass: https://en.wikipedia.org/wiki/File:WTC-Perspektive.jpg