Was there a design flaw or would any building of that height have failed?
In: Engineering
There was no design flaw.
The planes that hit the towers took out a good few of the beams supporting the part of the tower above the crash site. The remaining supports were perfectly strong enough to keep the building above supported. The towers stayed up for a good while after the crash.
The damage caused by the crash also damaged the fire proofing on the building’s structure around the crash site.
However there was a lot of jet fuel on board those aircraft which promptly caught fire in the crash. All that burning jet fuel caused high temperatures. These high temperatures combined with the damaged fire proofing caused the steel structure to heat up a lot. Steel gets weaker when it gets hot. The temperature at which it starts to weaken is a lot lower than the melting temperature.
Eventually the steel structure at the crash site was weakened enough that the remaining supports could not hold up the weight of the building above the crash site. They failed and the top of the building started to fall.
Now it fell on the part of the building below the crash site. Buildings are not designed to withstand the forces caused by the top half being dropped onto the lower half. This caused the entire building to collapse.
If there was no fire the towers would have stayed up at least for time to evacuate.
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