#### Oystein

##### Senior Member

Doesn't change the argument significantly - whether 98% or 99.75%, nearly 100% of the floor area is floor, and so the floors would bear almost all of the impact of chaotically falling debris and distorted structure.I don't what building and what floor you are calculating the percentage of area of the steel columns compared to the entire foot print.... but for flor 2 where the column size was max... the columns were 0.748% of the foot print. ..les than 1% and higher up it would have been probably about 1/3 of that so it the columns at floor 78 would be about 0.25% of the total footprint. (twin towers)

My calculation was quick and dirty, let me see if I can reproduce it:

- Total area is 209 ft x209 ft = 43681 ft^2 (that's ignoring the oblique corners)

- Each perimeter column was 1'2" x 1'1.5" = 1.31 fr^2; we have 240 of these -> 315 ft^2. That's 0.72% of floor area

- Add a bit for spandrels: Spandrels are 2/3 of the total perimeter of 4X209 ft, and, say, 1/2 inch thick, that's 23 ft^2 - almost negligible

- The core columns are fewer (47) but bigger; I have assumed that their total area would not exceed that of the perimeter columns, but also would not be far less. Make that anywhere between 0.5% and 0.7% of total area. Of course that depends much on the height.

So hmm yeah, 2% was a bit of an overestimate, but not wildly so. I like to err on the conservative side.