10-08-2013, 11:38 PM
(This post was last modified: 11-08-2013, 01:25 AM by Jeffrey Orling.)
Lauren Johnson Wrote:Assume that for some unknown reason, every one of the core columns of WTC 1 or 2 vanished in x number of floors. (Of course, we assume that they are still standing.) This eliminates the speculation about how many core columns remain and how strong they are.
If the core columns of one floor are removed what happens? Two? Three?
I assume, Jeffrey, you would say the whole building comes down with the removal of the core columns of even one floor. Correct. Tony, I am guessing you will say that the whole building does not collapse with the removal of only one floor's worth of core columns.
First, the columns were 3 stories tall. The were spliced one to the other at about 4 feet above the floor slab. So it's hard to imagine how a single floor of core columns could be removed. See attached diagram of the facade damage of north face of WTC 1 with the row 500 core columns shown in red and blue... Notice how they BEGIN above the floor level and end 3 stories up again 4' above the slab.
If by magic you removed JUST the 24 core columns the floors outside the core would collapse and the ROOSD would begin and the tower would come down. You could do this with magic removal of as few as 12 core columns.... the 4 corner ones and the two center ones on each side... My guess. I think perhaps as few as 8 as shown in the attached slide could cascade into a top drop and then ROOSD and global failure. Note in the top diagram the relative area of floor outside-the-core load percentages carried by each column.
The 23 columns in the center of the core were not required to support the floors outside the core... they supported inside the core floor (little area) and defined all the elevator shafts. Their size is markedly smaller.
Note in the FLOOR 1 COLUMN STUDY the relative areas of each column... the area is DIRECTLY PROPORTIONAL to the load that the column supports. These ratios are similar all through the height of the tower, though the columns all decrease in cross sectional area.