Reply #4: I don't think it is a particularly good analogy. [View All]

[AZCat]

It seems your source hasn't thought this through. The primary difference I see between your example (a tree toppling) and the WTC collapse is that there is a significant difference in the relative strengths of the materials when compared to the forces involved. While the modulus of elasticity is not the only property that affects the behavior of a structure it is useful for comparison.

E of white oak = 8,600 MPa
E of 304 stainless steel = 193,000 MPa

Mass of white oak tree = 24m high with 3m Dia and a density of 0.725 kg/m^3 = 123 kg

Mass of WTC 1 = approx 500,000,000 kg

Ratio(tree) = 123/8600 = 0.014

Ratio(WTC) = 500000000/193000 = 2590 (about six orders of maginitude greater)

I'll let you draw your own conclusions.