Home › Forums › DISCUSS › Current News & Events › Book Review: The Mysterious Collapse of World Trade Center 7 › Chris Martenson
I have previously pointed that:
-Intermittent free fall as a portion of the total building collapse is compatible with elementary physics, and engineering theory allows this through at least one (non-detonation) failure theory- which is buckling mechanics. Your rebuttal has been:
a.) To deny that sufficiently large fires were present to allow this.
b.) To imply that simply because there is little or no historical evidence of this, that this well understood engineering theory is not valid.
c.) That the observed symmetric collapse renders impossible the buckling collapse mechanism.
I find these “rebuttals” to be inadequate.You have failed to support your contention that “laws of physics” have been violated, you have provided no meaningful reason why free fall, near free fall, and progressive collapse cannot occur in the same event, other than as claimed above which I interpret broadly as simple skepticism.
There still is a discrepancy to the actual free fall duration, I have chosen, deliberately, to argue in support of your accounting of this at ~2.25 seconds, because this allows us to introduce, discuss and comment on the specific characteristic of buckling failures, which provides near instantaneous release of load in a catastrophic event. This is an important concept, and worthy of detailed discussion.
Presenting skepticism in and of itself not science, unless acted on to prove or disprove a claim or theory. Where is the proof?
An argument that focuses on the time discrepancy by necessity requires the discussion of a very different failure mode, that of progressive collapse. And I am happy to have that discussion as well. So let's move on, as this contains more detailed discussion of complex physics- relevant to Tower 7 collapse.
I discovered this paper (link below) during a search last night. I think you’ll find a novel and scientifically rigorous discussion of the progressive collapse mechanics of multi-story buildings, with a good framework of the physics involved. The work is primarily directed at the collapse of Tower 1 and 2, but the physics and math is relevant to the progressive collapse component of Tower 7.
In this case, Tower 7, I would suggest that the initiator event is the buckling induced failure previously discussed causing a cascading collapse event.
This free body represents the snap through buckling trigger:
For the discussion we turn to the document itself:
Here are some excerpts:
However, a theory describing the progressive collapse dynamicsbeyond the initial trigger, with the WTC as a paradigm, couldnevertheless be very useful for other purposes, especially forlearning from demolitions.It could also help to clear up misunderstanding and thus to dispel the myth of planted explosives.Its formulation is the main objective of what follows.
Some critics have been under the mistaken impression thatcollapse cannot occur if because of safety factors used in designthe weight mg of the upper part is less than the load capacity F 0of the ﬂoor.This led them to postulate various strange ideas suchas “fracture wave” and planted explosives .However, the criterion in Eq. 5 makes it clear that this impression is erroneous. If Eq. 5 is violated, there is regardless of F 0 no way to deny the inevitability of progressive collapse driven only by gravity.
If the total internal energy loss during the crushing of onestory representing the energy dissipated by the completecrushing and compaction of one story, minus the loss ofgravity potential during the crushing of that story exceeds the kinetic energy impacted to that story, collapse will continue to the next story.This is the criterion of progressive collapse trigger Eq. 5. If it is satisﬁed, there is no way to deny the inevitability of progressive collapse driven by gravity alone regardless of by how much the combined strength of columns of one ﬂoor may exceed the weight of the part oft he tower above that ﬂoor. What matters is energy, not the strength, nor stiffness.
Interestingly, I note on the very first paragraph reference to the Tacoma Narrow bridge (!) as a comparative event. It seems that I am not the only one to use this reference….