am new here (not an engineer) and registered to ask the below question. If this breaks any forum rules/guidelines, apologies and obviously it can be removed. Currently in a debate surrounding WTC 7 (47 story building that fell during 911) and have one question (have also asked this question on Reddit engineers). I thought it would be interesting to see what a structural engineers take on the issue
It's related to this article "On the physics of high rise buildings" submitted to Europhysics magazine by several authors who believe WTC 7 may not have fallen due to fire.
The question is specifically about the below highlighted part taken from the article (NIST refers to the official investigation and findings on the WTC 7 collapse)
NIST acknowledge a 2.25-second period of free fall in its final report. Yet NIST’s computer model shows no such period of free fall, nor did NIST attempt to explain how WTC 7 could have had “no structural components below it” for eight stories. Instead, NIST’s final report provides an elaborate scenario involving an unprecedented failure mechanism: the thermal expansion of floor beams pushing an adjoining girder off its seat. The alleged walk-off of this girder then supposedly caused an eight-floor cascade of floor failures, which, combined with the failure of two other girder connections—also due to thermal expansion—left a key column unsupported over nine stories, causing it to buckle. This single column failure allegedly precipitated the collapse of the entire interior structure, leaving the exterior unsupported as a hollow shell. The exterior columns then allegedly buckled over a two-second period and the entire exterior fell simultaneously as a unit . NIST was able to arrive at this scenario only by omitting or misrepresenting critical structural features in its computer modelling. Correcting just one of these errors renders NIST’s collapse initiation indis*****bly impossible
Question to engineers here. Is the bolded part a correct assertion or not? If yes/no, please explain why
Thanks very much (I understand this may be a touchy subject, but this is meant in good faith as part of a discussion surrounding WTC 7)