Where did those core columns go then? Just like the original posts asked?
Did the bend and buckle inward? Did the telescope down into themselves?
Read my post above.
In slightly more detail yes, columns broke and they did so at the weld splices every 30 feet in each core column. There were NO continuous steel columns that were 1000 feet tall. During construction 30 foot, maximum, sections were brought to the job site and hoisted up when needed and welded to the section below eventually creating the 1000 foot tall core columns. Although in some aspects a weld is actually stronger than the column itself it is also the most ridgid part of such a column. Thus when such a column is bent it will do so smoothly only along the 30 foot sections, the welds cannot bend as easily and they fail.
Just give it up. You will never understand.
You need to retake physics.
You see, everyone here assumes the inner core columns and outer perimeter
columns magically disappeared, and the top section had several feet to
drop onto the lower structure.
Read my post above.
In more detail of the initial collapse; some core columns suffered damage or complete severing at the initial impact. Many of those damaged columns and some which had escaped significant damage had their fire insulation abraded.
Many of those were subjected to high temps that lowered the strength of them. This caused the core columns to creep as the load was transfered to columns that were reaching their limit. As floor spans failed lateral support of the core and perimeter columns was lost. We can see that the perimeter columns were bowing outward and that illustrates that the upper section was creeping downward which in turn illustrates that the core columns were sagging as well. The hat truss worked to keep distributing the load throughout the core and perimeter but at some point there was simply no more reserve to left in the building. One more failure, floor truss loss of lateral support, perimeter column or core column failure and the structure as a whole at that level could no longer hold the mass of the upper block. When that occured the columns all buckled/bent in very quick succession and at that point the gravitational force of the upper block would never be transmitted to the ground via the columns. If the columns no longer line up at the collapse zone the mass above the collapse zone is impacting the next lower floorspace which is only designed to transmit the gravitational force of ONE floor to the columns via the span to column connections.
NOPE!
There were only certain columns damaged, or broken.
Initially yes. Then others suffered weakening due to the heat. If I understand where you wish to go with this then you are assuming that if some columns remained in pristine condition then the building must still stand. This is pure folly. Do you then argue that if all perimeter columns were in pristine condition and only one core column that the building must still stand? If so then you have a severe misunderstanding of the physics, and engineering principles involved.
Normally, in the real world...when an object is in motion and strikes another object you expect to see at least one remain. If nothing else, the top
section of the tower should have stayed intact to crush the lower section. It did not.
It blew apart first.
Well it indeed did come apart sooner than the lower 80+ floors but I would really like to see some calculations that illustrate that the upper block should be riding down on top of the collapse zone like some hellish surfer.
Obviously as the upper block impacted the lower floors there would be severe stresses on the lower structure of the upper block. The upper block columns are striking the floor spans of the lower sections, but at the same time the lower section columns are spearing up through the upper section's floor spans. Once again we note that the floor spans supplied lateral support to the columns without which the columns cannot remain standing. After a few floors of collapse the upper block is much less intact as its columns have less and less connectivity to the floor spans.
