12. Problems in the NIST Report: Inadequate Steel Temperatures and Tweaked Models
I have read through the hundreds of pages of the Final NIST report on the collapses of the WTC Towers. (NIST, 2005) It is interesting to note that NIST “decoupled” and delayed their final report on WTC 7, which is overdue as of this writing (NIST, 2005; NISTb, 2005). I agree with some of the NIST report; for example:
Both WTC 1 and WTC 2 were stable after the aircraft impact, standing for 102 min and 56 min, respectively. The global analyses with structural impact damage showed that both towers had considerable reserve capacity. This was confirmed by analysis of the post-impact vibration of WTC 2… where the damaged tower oscillated at a period nearly equal to the first mode period calculated for the undamaged structure. (NIST, 2005, p. 144; emphasis added.)
At any given location, the duration of [air, not steel] temperatures near 1,000oC was about 15 min to 20 min. The rest of the time, the calculated temperatures were near 500oC or below.” (NIST, 2005, p. 127, emphasis added.)
NIST contracted with Underwriters Laboratories, Inc. to conduct tests to obtain information on the fire endurance of trusses like those in the WTC towers… All four test specimens sustained the maximum design load for approximately 2 hours without collapsing.” (NIST, 2005, p. 140, emphasis added.)
However, I along with others challenge NIST’s collapse theory. NIST maintains that all three building collapses were fire-initiated despite the observations above, particularly the fact that fire endurance tests with actual models did not result in collapse. In a paper by fire-engineering experts in the UK, we find:
The basis of NIST’s collapse theory is… column behaviour in fire... However, we believe that a considerable difference in downward displace between the [47] core and [240] perimeter columns, much greater than the 300 mm proposed, is required for the collapse theory to hold true… [Our] lower reliance on passive fire protection is in contrast to the NIST work where the amount of fire protection on the truss elements is believed to be a significant factor in defining the time to collapse… The [proposed effect] is swamped by thermal expansion … Thermal expansion and the response of the whole frame to this effect has NOT been described as yet [by NIST]. (Lane and Lamont, 2005.)