Hey, I'm just a dumb retired industrial chemist, not a structural engineer, but it seems to me that if, hypothetically, one were to cut 20% of the perimeter columns supporting a structure, one would get very different results depending on whether it was done to every fifth column on all four sides, or to cut mostly on one side.
Throw in a large fire, and.....
That goes to the main principle. It depends entirely on which columns -- where they are located in the floor plan.
This is my explanation of the principle involved. If members get their heads around
the principle at this simple level they will have some understanding of why Tony et all are wrong.
(My usual apology for the poor drawing in this graphic from about 2009 - I really should make a better drawing but....)
Take the drawing on the left. It shows an extremely simplified "model"
similar to WTC 1 or 2. Note "similar" - we are explaining a principle not detailing the WTC real mechanism for collapse initiation.
Point by point:
1)The weight of the "top block" is 400
2) It is carried on three rows of columns A, B and C;
3) The initial load distribution is 100, 200, 100 respectively;
Are we happy so far?
4) Cut out the row of columns C;
5) The load carried by C becomes ZERO;
What happens. This is where the foggy thinking comes in.
The answer is not intuitive for non-engineers and sadly for quite few engineers. No names - I'll point you look.
The correct answer is as shown in the middle drawing:
6) The load on row A becomes ZERO;
7) The load on the central row B doubles from 200 to 400; AND
8) Framing it in percentages (the way T Sz et al do) a 30% removal of columns causes a 100% increase in loading of row B. AND
That explains the principle. Simply. Trust me it is 100% correct. I don't sell used cars.
If anyone wants it translated into a multiple column scenario I can do it BUT be warned it very quickly becomes a few grades harder to comprehend.
For most non-engineers/architects/physicists reading this it may be enough to understand that arguments based on "percentage of columns removed" >>> redistributes load uniformly ARE WRONG. If anyone wants to get more understanding of what is RIGHT...follow up the post.
The most complex aspect of WTC Twin Towers collapse to explain IMO is the cascade failure process of collapse initiation. It has scarcely been touched on in forum discussions. Too hard for truthers. Hard for most engineers. And the engineers and academics would mostly accept that "it was a cascade - we cannot know the details and so what?' Of course truthers want to argue "If you cannot explain it it means CD."
Comments welcomed.
PS - Ignore the drawing on the right for now. It takes the next couple of steps towards explaining WTC cascade failure