> rolled metal has something that is called a 'benign mode
> of failure'!

Not on Google it isn't.
6 hits for that phrase, and none use it as a descriptive 
phrase in its own right as implied above.

The closest is arguably this NASA paper related to 
transverse matrix cracking in wood composites.

In order to be able to comment with any credibility on the 
WTC failure modes you need, at least, to have acquainted 
yourself with the nearly unique construction methods used - 
common to only a very few other buildings - all also pushing 
the limits of conventional design capability. Conspiracy 
theories are sometimes correct, but, right or wrong, they 
have a more convincing ring when based on a demonstrably 
factual foundation.


        Russell.




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