If they did, how did design flaws in the Twin Towers make them collapse?
The design of the Towers was a fairly new design at the time, it was called framed tube design. The major load-bearing walls were the four outside walls. The framed-tube design actually is what made the towers stand as long as they did after the fires started. It was also the reason the towers fell the way they did, straight down, one floor on top of the other. Framed tubed design is used on skyscrappers because it offers more support from lateral wind loads, and there are less interior columns, which opens up more office floor space. If you ever saw how they do a controlled demolition, you would know that it takes weeks to install the demolitions. They also gut the building first, they take out all windows, they cut notches in the steel beams to help them fall (just like a tree is notched before it is cut down), and they take out many columns and interior walls prior to installing the explosives, that is how they control the demolition.
