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Global Collapse

NIST's report on the Twin Towers employs a new term for total collapse: global collapse

NIST uses "global collapse" multiple times without clarifying its relationship to total progressive collapse.
It also uses the term "progressive collapse" 16 times.

The procedures and practices used in the fire resistance design of structures should be enhanced by requiring an objective that uncontrolled fires result in burnout without local or global collapse.

Removal of thermal expansion from the spandrels and equivalent slabs in the tenant area to avoid local buckling that affected convergence but had little influence on global collapse initiation

This further increased the gravity loads on the core columns. Once the upper building section began to move downwards, the weakened structure in the impact and fire zone was not able to absorb the tremendous energy of the falling building section and global collapse ensued.

As with WTC 1, once the upper building section began to move downwards, the weakened structure in the impact and fire zone was not able to absorb the tremendous energy of the falling building section and global collapse ensued.

The downward movement of this structural block was more than the damaged structure could resist, and global collapse began.

The downward movement of this structural block was more than the damaged structure could resist, and the global collapse began.

Recommendation 8. NIST recommends that the fire resistance of structures should be enhanced by requiring a performance objective that uncontrolled building fires result in burnout without local or global collapse.
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