Reply #221: wait, hang on a second

[OnTheOtherHand]

Are you saying that there are "lots of cases" in which a large section of a building has fallen onto the lower section? If so, then indeed we ought to have a useful baseline.

If not, then even the phrase "section... falling" strongly suggests to me that "rigid cube" (or cuboid) is a reasonable starting point. And, for heaven's sake, practically every physics problem I've ever done (the introductory ones, of course!) has made much that sort of simplifying assumption. Of course the question immediately arises: what makes the falling section more like a rigid cuboid than the section it is falling on? I think Bazant has answers to that (which include "look, if you don't like that model, here's a more complicated one that gives similar results"). Of course those answers are subject to debate.

It may not be facially obvious -- especially to non-engineers, but in some cases even to engineers -- whether a simple model is fatally flawed. But the mere assertion that the simple model might be fatally flawed isn't enough to render the model utterly unpersuasive.