Originally posted by pteridine
Originally posted by Yankee451
So is that a fancy and pompous way of saying you don't want to address the reasons why your report is inaccurate, and that it didn't even address
the question of the wing slicing the columns?
Care to comment on my comments? You can even use big words.
First, it is not my report. It is a paper byTomasz Wierzbicki, Professor of Applied Mechanics at MIT and two of his colleagues. I provided this
reference because you asked about the impact damage.
Second, it does address the wing slicing the columns. Possibly, you haven't read it or misunderstood it. It describes the methodology used in the
model and states: "According to the calculation performed by Teng and Wierzbicki  the mass ratio is 0.0783, which means 7.83% of the initial
kinetic energy of the wings (96MJ or 2.6% of the total initial kinetic energy) is lost in cutting the exterior columns."
If you need something more satisfying than this paper, you can get the address of Professor Wierzbicki and ask him your questions. You might even want
to critique his failure to properly address the wings cutting the columns and possibly correct his calculations if you think they are in error.
edit on 3/16/2011 by pteridine because: (no reason given)
It is the report you gave me...therefore to me it is your report, but I don't blame you for not wanting to take credit for it.
No, they did not calculate it, they created a model to explain it.
The “post-September 11th” structural engineer, while feeling the remorse and confusion that every other American has dealt with, is also
privileged with the immense education an analysis of the WTC collapse can provide.
Why are they mentioning remorse in a scientific paper? I am angry about 911, not remorseful…who is remorseful? NORAD? Are they trying to appeal
to our emotions or our logic?
As the fuselage and wings cut through the steel facade of the Towers, the affected portions of the column sheared off.
Where do they get this premise? Why would anyone suspect the wings could shear steel columns and not the reverse ? They seem to place a lot of
importance on momentum, but don’t consider the density of materials, why?
Is the image in Figure 2 the same image published by Wolfgang Staehl, Tina Cart and Robert Clark? How can all three have captured the same
perspective and if so, why would they use a fraudulent photo?
The exact position of the longitudinal axis of symmetry of the plane with respect to a floor is unknown.
The above text is directly below Figure 5 which is a close up of the damage. Why didn’t they try to at least get close to the real impact point
based on the measurements available from the photo directly above? Were they afraid if they were more exact they’d find that the fuselage impacted
directly with a floor, and not between floors?
At the same time, the 3m diameter engines and the wings could easily fit between office floors. This will be most probably the case with the North
Tower impact, which occurred with less roll angle.
Why will this be most probably the case with the North Tower? Would it throw their model off if the engines connected with a floor behind an exterior
wall? Did they see the video of the impact? It is very hard to tell what it is that hit the tower, much less the roll angle. How do they know there
was less roll angle? Based on the slice marks? If they can tell roll angle why can’t they tell the exact impact point by measuring the hole and
the position on the wall?
Upon impact into high-rise buildings, the situation is different. The framework of beams, columns, and trusses could deform plastically and
If they “could” deform plastically and fracture, that means they also may not plastically fracture. Are they trying to build a model to suit a
Because the contact area is small, these members, which are relatively narrow compared to the fuselage diameter, can cut and slice into main
elements of the airframe before being broken themselves. Thus there is a complex iterative failure sequence between the two “opponents”, building
and airplane, that are of comparable strength.
The building beams, columns and spandrels can slice and dice the jet, presumably before being broken themselves. By what? The jet it’s slicing and
dicing? Why do they state a jet’s strength is comparable to the building’s strength? Momentum? Is that a fair comparison? Wouldn’t they need
to compare a jet’s engine to an external column backed by a spandrel plate, backed by a concrete floor, backed by tubular floor joists, backed by
the central column or the opposite wall? With kinetic energy being equally shared, why would the whole plane enter the building instead of just the
more massive parts entering the building while less massive parts bounced off? Can momentum explain this all the way down to the tail section?
The main structural part of the wing is the spar – a continuous beam that extends from one tip of the wing to the other. For modeling purposes,
we assumed that the mass of the wings (excluding engine) was approximately 21300kg wing M . This mass does not include the mass of the fuel in
the wing tanks. Assuming that this mass is now uniformly distributed over the whole wing span and the wing is modeled as a thin-walled square
section cross section ...the equivalent thickness becomes 34.5mm.
So the wing mass, most of which is between the engine and the fuselage has now been equally distributed to the whole wing. All of the material used
for support is now used to create a 34.5 mm thick wing-shaped box of aluminum for the sake of their model. Is this an accurate and fair
representation to begin this test with?
The wings are swept at approximately 35o so that upon impact, external columns are contacted sequentially, one by one. However, the problem of a
hollow beam striking another hollow column at a right angle and a speed of 240 m/s has not been analyzed in the literature. Therefore it is not
possible, at this point in time, to give any detailed account on this interaction, between the wings and outer column, with a higher degree of
accuracy than our approximate engineering analysis.
Even with making a wing into an aluminum machete, they don’t quite have enough modeling power to give a detailed account on this interaction? Why
do they talk about their aluminum machete wing striking the columns at right angles? Wouldn’t a swept wing contact the corner of the column first,
and isn’t the corner of the column the sturdiest part? With the wing striking the corner like that, would not the corner act like a more massive
knife than even the massive machete-wing? Is this why they chose not to press this argument, settling instead with their lame approximated
The equivalent thickness of the hollow wing beam is approximately four times larger than the thickness of the exterior columns, 9.5mm ext t
. It is therefore reasonable to treat wings as rigid bodies upon impact with exterior columns.
They made a wing four times the thickness of the beam of a skyscraper...how is this reasonable?
In actuality the wings are constructed as a 3-dimensional lattice of open section beams, ribs and sheet metal skin that maybe of comparable
strength to the floor trusses. However, interaction between two 3-dimensional space frames impacting each other is too difficult to carry out
analytically at the present level of approximation.
First they make a machete-wing, and then they want it to be a 3 dimensional lattice work as strong as the floor trusses. How many trusses are they
using for this estimate? It’s too difficult to carry out analytically at the present level of approximation? Is that a fancy way of admitting
they’re talking out their bung holes?
Let me know if we need to continue.