Originally Posted by ElMondoHummus
Actually, the problem with Dr. Kurttila's approach is different. His estimate of the "resistance factor" is credible, but he completely blows the interpretation of what it means.
The reason is that a structure, during collapse, does not exert a constant force on the parts that are falling. Each individual member may (at best) exert a resistive force approximately equal to the strength of that member, but only until the member buckles or suffers compressive failure. This strain limit is generally only a few percent of the length of the member. Therefore, for the majority of the collapse, the descending parts are in "free-fall."
If you compute an average of this over distance (e.g. work), you're averaging zero times the free-fall distance plus the actual strength over a much shorter strain distance, and naturally you get a "resistance factor" that is far below the actual strength of the building. Therefore, a result of 0.14 or whatever he gets is really quite credible for a perfectly ordinary building, without any explosives at all.
See my whitepaper, esp. Appendix B, for more details.