I am not a physicist at all, and nor are you at least from what I know. We are both google searching these subjects as we argue. <img src="/forums/images/graemlins/lol.gif" alt="" /> But I was watching a show on the History channel about after people are gone. Two had building collapses explaining that the buildings collapsing from structural failures from halfway up or greater are collapsing becoming greater in mass and weight pancaking and putting more weight on the next floor breaking it faster and faster all the way down.

Also, here is a forum that might better explain it than me. Link

I am trying my ass off to find sources that aren't biased one way or the other. Try it sometime. <img src="/forums/images/graemlins/smile.gif" alt="" />