a) It is inconsistent and contradictory in the way it treats the tipping of the upper section of each tower
b) It assumes that global collapse ensues without modeling the collapse
c) Its fire simulations generate such a wide array of temperature profiles as to be essentially useless
d) Its assumptions about the loss of thermal insulation are mere speculation
e) It ignores the important effects of massive releases of corrosive gases in the fires
f) Its metallurgical analysis of the steel is perfunctory
g) It ignores evidence
(micron sized spheres) for the presence of molten iron in the towers prior to collapse
h) It mentions sulfidation, which it does not explain, while ignoring chlorination
i) And finally, NIST still cannot explain the collapse of WTC 7 after 6 years of trying
About 2 years after my early retirement I began researching 9/11 and became fascinated by the collapse of WTC 1 & 2. I realized that it would be of great interest to calculate the collapse times for a gravity driven collapse and compare the result with observations. This I did, and wrote up my findings in the ?Energy Transfer? article that was subsequently posted on the 911Myths website. I was quite surprised at the response to my work: the calculations were well received by some but scorned by others.
The model I based my calculation on was indeed quite crude
, so I have endeavored to improve it by including the effects of variable column strength and mass shedding. I tested the improved model and found that the towers always exhibited a self-sustaining collapse for realistic values of the various input parameters. Nevertheless, while my model appeared to show that a gravity driven collapse of the Twin Towers was physically possible, I still had some doubts about collapse initiation.
These doubts stemmed from the fact that my model assumes that the upper block of floors above the impact zone descends one story under free fall, thereby providing more than enough energy to destroy the columns supporting the floor below and initiate a progressive collapse.
But did the collapse of each tower really begin with such a single floor failure? I studied the appropriate sections of the NIST Report seeking an answer to this question. It soon became apparent that the tipping of the upper section of each tower was a key feature of the collapse. Thus I began studying the tipping of WTC 1 & 2 and ultimately wrote two articles on this topic that were posted on 911Myths.
The research described in these articles showed that WTC 1 required almost 2 meters of downward displacement in the upper section of the building to initiate collapse. This is about two times the downward displacement required for the collapse of WTC 2, and six times NIST?s estimate of Dd(WTC 2) of about 30 cm based on its finite element computer model. In contrast, a simple energy analysis of the collapse shows that NIST?s small downward displacements lead to inferred collapse energies that are too low to be acceptable
? we know the Twin Towers would not collapse that easily.
Further, the geometry of a ?Leaning WTC Tower? with an asymmetric downward displacement of 30 cm implies a tilt angle of less than ? degree. Remarkably, however, NIST suggest that tilt angles before collapse initiation were more than 4? for WTC 1 & 2. Thus the NIST Final Report first underestimates the downward displacements within the Twin Towers, only to later overestimate the initial tilt angles to justify the collapse.
A close look at the failure of WTC 2 shows that the collapse began with a tilting or rotational motion of the upper section of the Tower about a ?hinge? at the 80th floor. This rotational motion, which commenced at a tilt angle ~ 2?, was caused by an almost instantaneous multi-column failure that eliminated the structural support on one side of WTC 2 near the impact zone
. Once set in motion, the upper block moved with a nearly ?free? rotational trajectory of a body pivoting under the constant force of gravity. This behavior was sustained at tilt angles up to about 20?. Thereafter the motion of the block changed somewhat although the suggestion that the tilting suddenly stopped is not correct. What appears to happen is that the upper section was continuously crushed near the 80th floor by its own momentum so that the rotation was no longer that of a rigid body. Eventually the "hinge" at the northeast corner failed and the descending block took on a more vertical motion. Interestingly, once the hinge failed, and the pivot became frictionless, the motion of the center of gravity is predicted to become vertical, causing a shift in the rotational axis, as observed.
For most of 2006 I switched my attention to two important aspects of the collapse of WTC 1 & 2:
i) the pulverization of concrete and
ii) the sustained high temperatures of the rubble pile.
First, I carried out an energy balance analysis of the collapse of WTC 1 that included the energy consumed in crushing concrete on one floor (234 MJ) and compared this to other contributions to the energy dissipated by the collapse. As expected, the plastic strain energy dissipated by the buckling of columns (284 MJ) was confirmed to be the largest drain on the kinetic energy driving the collapse, but the energy to pulverize the concrete was clearly an important additional energy sink. However, I also concluded that such energy sinks should be summed over two WTC floors per impact to allow for the simultaneous destruction of the uppermost floor of the lower fixed section, and the lowest floor of the descending section. Such an assumption leads to an energy decrement that still assures a self-sustaining progressive collapse of WTC 1 if the input kinetic energy is derived from a one-storey free fall of the upper block- a condition that must be modified in a tipping scenario.
The sustained high temperatures of the rubble pile proved to be more problematic. The NIST Report indicates that about 100 tonnes of burning material and smoldering ?embers?, at 500 - 700? C, fell into the rubble pile when the Twin Towers collapsed. Propagation of smoldering combustion within the rubble pile was sustained by the indigenous supply of live load ?fuel?- consisting of office furniture, paper, textiles and plastic materials - and oxygen.
Setting aside the issue of oxygen availability, let us consider how long the available fuel could last. The heat flux of a smoldering fire is typically ~ 8 kW/m2 from which we may calculate the average fuel consumption rate within the rubble pile. NIST estimate that there was initially about 50,000 kg of combustible material on each floor of WTC 1 & 2. If we assume that material from about 5 floors was consumed before the Towers collapsed, about 5,250,000 kg of ?fuel? was initially available within the rubble from each Tower. It is a simple matter to show that this fuel would be able to sustain the rubble pile fires for no more than about 30 days
. However, it was not until December 19th 2001, or 100 days after 9/11, that the Governor of New York, George Pataki, officially declared the WTC fires to be totally extinguished. We are left wondering what ?stoked? the rubble pile fires beyond the expected 30 days.
Thus, by the start of 2007, I still had plenty of questions about the official version of the collapse of the Twin Towers. And this is essentially where I stand today...I remain a 9/11 agnostic
. And as a scientist I believe there is always room for doubt and for more research. In fact, that?s how I see research ? a process of re-searching, of looking again. The NIST Report is a great start, but only that. It leaves some unanswered questions...And my work experience in the Canadian nuclear industry has taught me to be skeptical of the ?official? view - the consensus view - because it is usually politically motivated!