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This and the next 14 slides pertain to collapse on September 11, 2001 of three World Trade Center buildings (WTC1, WTC2 and WTC7).
This slide is from:
http://en.wikipedia.org/wiki/Collapse_of_the_World_Trade_Center
“Both buildings collapsed symmetrically and more or less straight down, though there was some tilting of the tops of the towers and a significant amount of fallout to the sides. In both cases, the portion of the building that had been damaged by the airplanes failed, which allowed the section above the airplane impacts to fall onto the undamaged structure below. As the collapse progressed, dust and debris could be seen shooting out of the windows several floors below the advancing destruction, caused by the sudden rush of air from the upper levels. The first fragments of the outer walls of the collapsed North Tower [WTC1] struck the ground 11 seconds after the collapse started, and parts of the South Tower [WTC2] after 9 seconds. The lower portions of both buildings' cores (60 stories of WTC 1 and 40 stories of WTC 2) remained standing for up to 25 seconds after the start of the initial collapse before they too collapsed.[13]”
(For a diagram of the building core see three slides hence.)
Text from:
http://www.globalresearch.ca/mechanisms-of-destruction-and-collapse-of-the-world-trade-center-wtc-buildings-on-911/5333553
Mechanisms of Destruction and Collapse of the World Trade Center (WTC) Buildings on 9/11, “An Analysis of Peer Reviewed Technical Literature 2001 - 2012”, by Timothy E. Eastman and Jonathan H. Cole,
Global Research, May 06, 2013
Journal of 9/11 Studies Volume 37, April 2013.
Eastman and Cole write:
“What is most striking about our results is the fact that there is serious disagreement as to how the WTC structures fell on September 11, 2001. While precise sequences of every building component failure cannot be determined, the overall basic mechanism of destruction (i.e. some type of fire-induced natural gravitational collapse (PC), or some type of planned demolition CD) is clearly in dispute. There is no consensus. At this point, almost 12 years later, there should not be any significant disagreement about such a fundamental issue as to how three buildings were destroyed so completely given the magnitude of the event, the implications of the event, and repercussions for existing and future structural design.”
Text from:
https://911inacademia.files.wordpress.com/2011/01/preview-some-misunderstandings-of-wtc-collapse-analysis.pdf
“Some Misunderstandings Related to WTC Collapse Analysis”, by Gregory Szuladzinski, Anthony Szamboti, and Richard Johns, International Journal of Protective Structures, Vol. 4, No. 2, 2013.
ABSTRACT: This article elaborates on variables associated with the collapse of the North Tower [WTC1] of the World Trade Center. The previously published quantifications of inertia, column capacity, and the assumptions related to the beginning of downward motion, are examined and corrected. The reasons for false conclusions reached in several previous analyses are presented.
INTRODUCTION: This presentation is not so much about how the WTC towers failed, but about how they could not fail. The objective is to eliminate erroneous concepts supported by false assumptions and by the use of incorrect values for velocity, mass, and column resistance. The only complete hypothesis of the global collapse mechanism of the Towers is a successive flattening of stories associated with compressive column failure and referred to as a Progressive Column Failure mode or PCF in brief. (In the past this mode was often referred to as pancaking, but this term is not used here to avoid ambiguities). It is explained here why PCF could not be the mode of the ultimate destruction.
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