I read the report that beardedbruce is referencing. It doesn't say that the core failed. It said that some of the structural steel became distorted and as a result the crosspieces holding up the floors slipped off their brackets, resulting in a pancaking of the floors.


From the report...

The perimeter tube design of the WTC was highly redundant. It survived the loss of several exterior columns due to aircraft impact, but the ensuing fire led to other steel failures. Many structural engineers believe that the weak points—the limiting factors on design allowables—were the angle clips that held the floor joists between the columns on the perimeter wall and the core structure (see Figure 5). With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t.

As the joists on one or two of the most heavily burned floors gave way and the outer box columns began to bow outward, the floors above them also fell. The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above.

"crashing down on these angle clips"

This report is saying that the floors fell independently of the core. It also says that the buildings collapsed, but it doesn't in any way show how the core could have collapsed using this theory.

http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html


BTW, even the NIST has rejected this theory.