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Steel Analysis

Failed to disclose sulfidated steel described in Appendix C of FEMA's Report.

Used paint deformation analysis to infer maximum temperatures steel exposed to in fire zones.

Observations of paint cracking due to thermal expansion. Of the more than 170 areas examined on 16 perimeter column panels, only three columns had evidence that the steel reached temperatures above 250 ºC: east face, floor 98, inner web; east face, floor 92, inner web; and north face, floor 98, floor truss connector. Only two core column specimens had sufficient paint remaining to make such an analysis, and their temperatures did not reach 250 ºC. ... Using metallographic analysis, NIST determined that there was no evidence that any of the samples had reached temperatures above 600 ºC.

-- NIST's Final Report on the Twin Towers (p 90/140)
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