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Old 24th November 2015, 05:47 PM   #102
Tony Szamboti
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Join Date: Jun 2007
Posts: 4,976
Originally Posted by Oystein View Post
Good and valid points.
Now c79 was not a corner column, and thus the framing from west and south was not necessarily dimensioned to be sufficient in the anbsence of the northern girder and the eastern beams - it was, or perhaps wasn't, I can't tell.


I am indeed not aware that "NIST had to do some additional juggling to get the west side girders to fail". Can you direct me to the sub-section that explains this juggling?

So the 11th floor girder to the west did not fail in their model?
But all of the north girders from f13 down to f6 did, right?

There is another effect that I think played a role: The collapse of 8 floors adjacent to c79 wasn't clean and trouble free - no doubt some of their mass kicked laterally into c79 with large force.


May all these factors be as they are - in the end, the NIST-model ran, and it resulted in the buckling of c79.
And perhaps it is unfortunate that we don't have the details of the model input to scrutinze (frankly, I would very much lack the ability and capacity to do scrutinizing on that level anyway).


Now as for the UAF study - what would we expect them to model to resolve these questions?
Column 79 was a corner column of the central core in WTC 7.

You may not know that the lateral support at each story to keep a column from buckling only needs to be about 0.6% of the axial load on the column. So the east and west girders were more than sufficient to laterally support column 79 and keep it from buckling.

You may also not know that the NIST model was manually manipulated by removing things when they felt the item would have failed.

Last edited by Tony Szamboti; 24th November 2015 at 06:06 PM.
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