I am a structural engineer specialized in shipbuilding. I have inspected many ships built of steel damaged by fire and overload of various kinds. None of these ships or their structures has ever collapsed by fire. Deformed, yes. I have some observations regarding the WTC2 collapse that may be of interest:
The NIST NCSTAR 1-6D report suggests that the WTC2 collapse was due to the following:
"Buckling of East Wall and Collapse Initiation
With continuously increased (sic) bowing and axial loads, the entire width of the east wall buckled inward. The instability started at the center of the wall and rapidly progressed horizontally towards the sides. As a result of the buckling of the east wall, the east wall significantly unloaded, redistributing its load to the softened core through the hat truss and to the south and north walls through the spandrels ( …). The section of the tower above the buckled wall suddenly moved downward, and the building tilted to the east ( …).
The section of the building above the impact zone tilted to the east and south (observed at about 7° to 8° to east and about 3° to 4° to south, …) as column instability progressed from the east wall to the adjacent south and north walls. The release of potential energy due to downward movement of the building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse ensued (sic)."
According to other NIST reports the total mass above was supported as follows:
50% - by the 47 core columns.
12.5 % - by the south wall columns (abt 80)
12.5% - by the east wall columns (abt 80)
12.5% - by the north wall columns (abt 80)
12.5% - by the west wall columns (abt 80).
About 80% of the wall and core columns were intact after first impact according NIST and the tower structure carried the mass above. Then there were fires in the office spaces between the core and the outer walls. The outer wall columns were always cooled by fresh air so they were unaffected by the heat.
We are told that the east wall, that carried 12.5% of the mass above, buckled inward due to axial loads some minutes before the collapse, which BTW are constant and not increasing, as suggested. The buckling deformation is not big as there is still some support from floors inside.
We are then told that the east wall significantly unloaded but not how much. Let's say that 50% of the load on the east wall that originally carried 12.5% of the total mass above, i.e. 6.25% of the total mass above is now redistributed to (i) the core, and to the (ii) south and (iii) north walls through connecting structure.
So 6.25% of the total mass above is redistributed. What happens?
Say that 50% of that or 3.125% of the total mass above is redistributed to the core; it will then carry 53.125% of the total mass above. Thus the load on the core increases 6.25% after the alleged redistribution.
We are told that the core is 'softened' which is not scientific but maybe it was affected by heat. However, half of the core columns were far away from any fires so they could hardly have been affected. But as the core columns had resisted the fire so far, a load increase of 6.25% due to redistribution could not make the core collapse!
25% of the redistributed load or 1.5625% of the total mass went into the south and north walls respectively that now each carries 14.0625% of the total mass above. Thus the load on the south and north walls increased 12.5%. These walls were not affected by fire as they were cooled by fresh air. There were some damage to the south wall, but again it did not collapse at impact, so a load increase of 12.5% will make little difference. No deformation of any kind is seen on the north and south walls after redistribution.
Global collapse could therefore not ensue due to such load distributions because there were too much redundancy and safety factors built into the outer wall columns (wind, lateral loads, etc) and also in the core columns. You could maybe expect further deformations of structure finding a new equilibrium and the tower may have tilted a little and stopped in that position but sudden global collapse is impossible due to the alleged load distribution!
Actually there is no evidence of any sort for the statement "Global collapse ensued". It is only wishful thinking by incompetent and/or complacent NIST engineers. They know that no steel skyscraper has ever collapsed due to fire!!
So what happened? Controlled demolition, CD, from top down? It seems that WCT 2 47 off core columns were damaged first, as the tower actually falls in its own footprint. The outer wall columns break afterwards like spaghetti by the floors being pulled down by the core columns. It seems that the core columns were broken by CD at every 10th floor, or so. NYFD staff noted these explosions, bang, bang, bang just before collapse ensued.
It would have been very easy to recover all the bits of the core columns from the rubble and assemble them on a 400 meter long field to verify (a) in how many parts each column split during collapse and (b) how the surface of the broken areas looked like. CD would probably have cut of the core columns sideways to dislocate them so that they could just drop down pulling other structure with them. Alternatively complete pieces of core columns were blown away. In either case a forensic examination of the core columns would have explained the collapse. If the collapse was due to release of potential energy overstraining the core pillars, the broken areas would look completely different. But as no complete forensic examinations were done for unknown reasons we must find other means to establish the real cause of the collapse. Easiest is of course a complete re-hearing of the case by a competent law court.
I messaged all of the admins of the group and all of them said they didn't delete the thread...so the only other person who could have deleted it is the person who originally made the post, unless the admins lied.
