Reply #103: I was wondering how long it would take for you to ask that question

[anigbrowl]

So here are some examples

First, two examples of blowing up steel-framed sports arenas. These are nothing like the WTC of course, they're just illustrative of ideal cases and their unusual construction makes it easy to see the approach: http://www.youtube.com/watch?v=OZkr0A9633Q&feature=related and http://www.youtube.com/watch?v=lwtbhqt9L84&feature=related

Now, what we're actually interested in are the failure modes of box-like steel framed buildings. The WTC buildings are unusual insofar as they're built around a central core so we can't get something exactly the same, but this video offers a good example of how steel-framed structures deform radically under stress, and might yield some insight into why the top of the tower disintegrated as it was falling rather than when it hit the ground: http://www.youtube.com/watch?v=PsQSGZ__jAY&feature=related You'll want to advance to (or wait for) 0:55 to 1:13.

Enjoy!