Basquearch writes: "Major Tom still misses the big picture as previously explained, by not dividing the collapses into two phases."
BZ describes 5 stages. From the paper::
"The 110-story towers of the World Trade Center were designed to
withstand as a whole the forces caused by a horizontal impact of
a large commercial aircraft (Appendix I). So why did a total collapse
occur? The cause was the dynamic consequence of the prolonged
heating of the steel columns to very high temperature. The
heating lowered the yield strength and caused viscoplastic (creep)
buckling of the columns of the framed tube along the perimeter of
the tower and of the columns in the building core. The likely
scenario of failure is approximately as follows.
In stage 1 (Fig. 1), the conflagration, caused by the aircraft fuel
spilled into the structure, causes the steel of the columns to be
exposed to sustained temperatures apparently exceeding 800°C.
The heating is probably accelerated by a loss of the protective
thermal insulation of steel during the initial blast. At such temperatures,
structural steel suffers a decrease of yield strength and
exhibits significant viscoplastic deformation (i.e., creep—an increase
of deformation under sustained load). This leads to creep
buckling of columns (Bazant and Cedolin 1991, Sec. 9), which
consequently lose their load carrying capacity (stage 2). Once
more than half of the columns in the critical floor that is heated
most suffer buckling (stage 3), the weight of the upper part of the
structure above this floor can no longer be supported, and so the
upper part starts falling down onto the lower part below the critical
floor, gathering speed until it impacts the lower part. At that
moment, the upper part has acquired an enormous kinetic energy
and a significant downward velocity. The vertical impact of the
mass of the upper part onto the lower part (stage 4) applies enormous
vertical dynamic load on the underlying structure, far exceeding
its load capacity, even though it is not heated. This causes
failure of an underlying multifloor segment of the tower (stage 4),
in which the failure of the connections of the floor-carrying
trusses to the columns is either accompanied or quickly followed
by buckling of the core columns and overall buckling of the
framed tube, with the buckles probably spanning the height of
many floors (stage 5, at right), and the upper part possibly getting
wedged inside an emptied lower part of the framed tube (stage 5,
at left). The buckling is initially plastic but quickly leads to fracture
in the plastic hinges. The part of building lying beneath is
then impacted again by an even larger mass falling with a greater
velocity, and the series of impacts and failures then proceeds all
the way down (stage 5)."
So do I.
Basquearch writes: "Bazant’s three papers and response to comments thoroughly explains actual global collapse of a building where the impact forces go into the columns and are distributed among them equally."
This is false. There are many arguments given in the papers. Only the argument in BZ and later repeated in BLGB in the section titled "Inabsorbable Kinetic Energy" uses such an initial impact.
He also says: "Both NIST and Bazant’s papers complement each other as the gravity only explanation of the collapse of all three Towers."
Bazant offers nothing about collapse initiation in any of his papers except his own personal opinions about what initiated collapse. He discusses many arguments concerning collapse progression, but they cannot be used to distinguish between natural collapse and a CD which exploits structurally weaker seams within a building, such as the OOS regions or a line of bolted column to column connections located along the 98th floor.
From the BLGB review:
"Review of first paragraph:
BLGB: "To explain the collapse, it was proposed (on September 13, 2001; Bazant 2001; Bazant and Zhou 2002) that viscoplastic buckling of heated and overloaded columns caused the top part of tower to fall through the height of at least one story, and then shown that the kinetic energy of the impact on the lower part must have exceeded the energy absorption capacity of the lower part by an order of magnitude."
Dr Bazant gave an unsubstantiated opinion that the early deformation and initial buckling sequence was caused by viscoplastic buckling of heated and overloaded columns in 2001. Only 2 core columns from the WTC1, 2 collapse initiation zones were recovered, so there is no proof that collective viscoplastic buckling of heated and overloaded columns. It is just his opinion but he presents it is fact.
BLGB: "A meticulous investigation of unprecedented scope and detail,
conducted by S. Shyam Sunder’s team at the National Institute of Standards and Technology (NIST 2005), supports this explanation."
Dr Bazant's opinion (2001) of the cause of WTC1, 2 collapse initiation was "confirmed" in 2005 by "a meticulous investigation of unprecedented scope and detail" conducted by S. Shyam Sunder’s team at the National Institute of Standards and Technology.
Many people believe that Dr Bazant has "proven" that both collapse initiation and collapse progression for WTC1 and 2 were natural. The reality is that Dr Bazant only stated his opinion of what he thinks happened during collapse initiation without any proof. His "proof" is the NIST report on the WTC1, 2 collapse initiation scenarios and the famous sagging floors. This is the final "proof"."
Everything Bazant says about the cause of collapse initiation is his own personal opinion presented as fact. The only supposed "proof" is in the "meticulous investigation of unprecedented scope and detail, conducted by S. Shyam Sunder’s team at the National Institute of Standards and Technology (NIST 2005).
This "proof" depends on many questionable claims by the NIST. The NIST provides the only known "proof" while Dr Bazant just narrates his opinion.
This "proof" of the cause of inward bowing and the claim that perimeter destabilization caused the collapses will be addressed in an upcoming paper.
So to be very clear concerning collapse initiation: NIST supplies the "proof" while Bazant just narrates his opinion.
Archebasque writes: "Review of Verinage demolitions indicate the validity of the crush down crush up phases of homogenous collapse propagation."
You are clearly making up opinions as you go. Bazant never mentions Verinage style CD. "crush down, then crush up" doesn't actually exist, for WTC1 or in the case of verinage style demolitions. My comment in the review meant that if he had bothered to compare his crush down, crush up assumption with actual demolitions using crushing as a means of destruction like the verinage style demolitions, he would have seen that his assumption is wrong.
From the BV review:
"Conclusions:
The crush down (eq 12) and crush up (eq 17) equations of motion for progressive collapse cannot be applied to WTC1. "Crush down, then crush up" has no application for WTC1 whatsoever. IT also cannot be observed in many Verinage style demolitions, where the top part of a building is intentionally dropped on the bottom part. While "crush up, then crush down" seems mathematically sound, we can find no consistent examples of buildings that behave that way. So why do some people, including Dr Bazant, believe in "crush down, then crush up"? The concept "crush down, then crush up" seems only the brain-child of a mathematical calculation in BV that the author and many of his readers began to take literally. Many people considered the process of "crush-down, then crush-up" to exist and be applicable to WTC1 without any supporting visual evidence. It is clearly not."
"Crush down, then crush up" came from a 1-D mathematical calculation which Dr Bazant believed represented something real. He applies this to WTC1 in 2008.
Many of the posters here probably believe that crush down, then crush up" actually happens with buildings because "Dr Bazant said so".
Basquearch continues: "The literature is replete with structural engineers analyzing the mechanics of falling buildings and structural failures"
Please think about what you are saying. If this is true, why is Bazant introducing these basic crush down and crush up equations in 2008?
Can you cite any equations of motion derived to describe the movement of the crush zone of buildings before 2008? If so, why doesn't Bazant just reference the work already done?
Basquearch writes: "Major Tom believes CD occurred in NIST's Phase 1, Initial Collapse. Bazant is the wrong venue. The proper venue for Major Tom's CD claims is the NIST report. Analyze that instead."
Collapse initiation and early deformation are certainly the most important places to look. I agree with you that the Bazant papers are the wrong place to look. So when Bazant writes in BLGB:
"Previous analysis of progressive collapse showed that gravity alone suffices to explain the overall collapse of the World Trade Center (WTC) towers. However, it remains to be checked whether the recent allegations of controlled demolition have any scientific merit. The present analysis proves that they do not."
you will agree that this is false. Bazant is not the right venue for studying the central CD questions, though he claims his analysis proves CD didn't happen.
Or in BV when he writes:
"However, a theory describing the progressive collapse dynamics
beyond the initial trigger, with the WTC as a paradigm, could
nevertheless be very useful for other purposes, especially for
learning from demolitions. It could also help to clear up misunderstanding
(and thus to dispel the myth of planted explosives)."
You would agree with me that Bazant cannot expel the accusation of planted explosives by describing collapse dynamics beyond the initial trigger as he claims. It is not the place to look.
We seem to agree with each other that Bazant is not the right venue. BLGB cannot possibly be used to determine "whether the recent allegations of controlled demolition have any scientific merit." When he claims to disprove CD in BLGB, he is wrong.
