Christo conveniently ignores the links to the structural engineer who actually designed the towers, and instead imagines seeing things in the collapsing videos. Here are a few facts:
1. the towers were designed and built to be flexible, without concrete shear walls. As proof we have the engineer's own words calling them "shaftwalls". Which are firewalls, not shearwalls that start at the base. The steel columns in the center hold only vertical load, the perimeter walls take all lateral load..
LERA | World Trade Center
2. Here is a good article on the WTC in wiki. Lots of details. OMG, No mention of concrete shear walls?? Because there were none.
Construction of the World Trade Center - Wikipedia, the free encyclopedia
3. Here is a typical floor layout. Look only steel columns, no concrete walls. WOW it looks just like the see-thru photos!! look at all those air ducts and elevators and stairwells. Looks like there is no room for concrete walls. Notice how the steel columns are continuous and go all the way from the base to the roof. Only the "shaftwall" locations change which are architectural firewalls.
File:Nistncstar1-1-fig2-4.png - Wikipedia, the free encyclopedia
4. This USC engineering article does not mention concrete walls, because there weren't any...
illumin : printable : Why The World Trade Center Towers Collapsed
5. If there were any concrete shear walls, the WTC would not have had to place 20,000 sway dampers to reduce the 6' sway that occurred after construction. A concrete wall could not sway 6' therefore there was no concrete wall. Also, the towers would not have been so lightweight:
World Trade Center - Devwiki
In addition, 10,000 dampers were included in the structure. With the large core and high load-bearing perimeter for structural integrity, Robertson created a tower that was extremely light for its size.
SNs flew huge jet liners into the towers at very high speed, which damaged the towers, and created fires that eventually led to the collapse.
The hijacked planes caused the WTC to collapse. There is no other realistic explanation.