Apols Atilla but as I pointed out many pages ago . . .
PWNED :innocent:
Hi DB,
I have already started reading two of these reports.
Could not open the first few links. Did a search google search and came up with this
Why Did the World Trade Center Collapse?—Simple Analysis1
Zdeneˇk P. Bazˇant, F.ASCE,2 and Yong Zhou3 PDF
However, it is grossly flawed and over simplified. All the formula and sigmas make it look as if these people know what they are talking about but's it's a lot of blinding formulas which doesn't stand to physical scrutiny.
Their document is summarised as [IAbstract: This paper presents a simplified approximate analysis of the overall collapse of the towers ofWorld Trade Center in New York
on September 11, 2001. The analysis shows that
if prolonged heating (what is prolonged heating? Time is not specified. Spanish building burnt for 24 hours and stood up. WTC towers burnt for approx 1 hour) caused the majority of columns of
a single floor (just one single floor? No way. Pretty big assumption) to lose their load
carrying capacity, the whole tower was doomed.
DOI: 10.1061/~[/I]
I've heard this before. Supporting horizontal beams bend and the corrugated light steel floors give way. collapsing onto the ones below. However, steel below is much cooler if not normal temperature and so unless the outer and core columns are taken out in total synchronised blow outs their theory as well as other copy analysis is fundamentally flawed.
If you open the PDF and look at figures FIG3. & FIG4 their analysis fails to a fundamental factor.
FIG3. b - gains inertia and momentum to one side as it buckles on one side and then corrects it self nad falls flat.
Appendix II. Why Didn’t the Upper Part Pivot About
Its Base?
Since the top part of the South Tower tilted @Fig. 3~a!#, many
people wonder: Why didn’t the upper part of the tower fall to the
side like a tree, pivoting about the center of the critical floor?
@Fig. 3~b!#. To demonstrate why, and thus to justify our previous
neglect of tilting, is an elementary exercise in dynamics.
Far from elementary. The authors dismiss this with the solution -
The moment
equilibrium condition for the column as a free body shows that
each column can at most sustain the shear force F152Mp /h1
where h1'2.5m5effective height of column, and Mp'0.3MN
m5estimated yield bending moment of one column, if cold. Assuming
that the resisting columns are only those at the sides of
the framed tube normal to the axis of rotation, which number
about 130, we get Fp'130F1'31 MN. So, the maximum horizontal
reaction to pivoting would cause the overload ratio
Fmax /Fp'10.3 (6)if the resisting columns were cold. Since they are hot, the horizontal
reaction to pivoting would exceed the shear capacity of the
heated floor still much more ~and even more if fracture were
considered!. (See FIG 5.)
Essentially what they are saying is that cold metal acts with greater resistance than hot metal to correct this fall.
THIS IS UTTER NONSENSE. Think about their diagram FIG 3 again. Not all the columns on the outside and the core will be at equal temperatures as aircraft hit from one side. (There is a comment on the Fire Chiefs report saying there were no fire walls, hence smoke spread quickly. But this doesn't explain fire spreading as heat and flames rises and oxygen likely to be less at ground level than ceiling). Anyway of all the columns the side which is hotter (assuming their theory) would buckle whlist side which is cold would stand erect. HENCE, how can the column correct itself.
ESPECIALLY SO AS THOSE FLOORS WILL HAVE GAINED SIDEWAYS MOMENTUM FALLING TO THE OUTSIDE.
Ok lets say as in FIG 4 a, then FIG 4 b, then FIG4 c, we accept their theory - what they are saying is that cold metal on lower floors held the wait of the pivot point of the building forcing the peripheral columns to buckle and bend. We are now talking cold metal bending as in FIG D.
Cold metal will not bend in free fall. Hence to suggest building fell with accellerating velocity is simply does not hold up to Newtons laws of physics.
This papers analysis is fundamentaly flawed even within their own assumptions.
1. THEY CAN'T SUGGEST HOT METAL BENDS AND BUCKLE TO EXPLAIN BENDING / TILTING OF BUILDING ON ONE SIDE and then
2. WEIGHT OF BUILDING IS HELD UP ON PIVOT POINT BY COLD METAL COLUMNS ON THE COLLAPSING SIDE BY COLDER FLOORS
3. AND THEN STATE COLD METAL COLUMNS COLLAPSES AT FREE FALL ON OPPOSITE SIDE CORRECTING THE BUILDINGS TILT.
Here it is in their words again.
So, the maximum horizontal
reaction to pivoting would cause the overload ratio
Fmax /Fp'10.3 (6)
if the resisting columns were cold. Since they are hot, the horizontal
reaction to pivoting would exceed the shear capacity of the
heated floor still much more ~and even more if fracture were
considered!.
LET ME POSE THIS QUESTION.
1. YOU HAVE FOUR METAL COLUMNS.
2. ONE SIDE BENDS WITH HEAT
3. OK ASSUME TWO CORNERS BENDS WITH HEAT
4. TOP HALF GAINS SIDEWARD MOMENTUM AND INERTIA AND WE ARE TALKING TONS
5. WHAT KIND OF RESISTANCE FROM COLD METAL COLUMNS WILL YOU NEED TO STOP THE PIVOT POINT FROM FALLING IN?
6. WHAT KIND OF PULL OR HOLDING FORCE WOULD YOU NEED TO STOP BUILDING FROM BRAKING AWAY FROM IT'S OPPISSITE SIDE.
7. ALTERNATIVELY SOMETHING MUST HAVE EITHER CAUSED COLD CORE AND PERIPHERAL COLUMN METALS TO GIVE WAY OR BEND.
HOT AND COLD METAL STRENGTH DOES NOT ANSWER THE QUESTION. (Also debatable as to what max heat can be reached by aircraft fuel but we won't complicate the physics here).
Questions 6 & 7 are fundamental imho.
Ok, if you also look at the basic fundamentals of their descripting diagram FIG4 D.
They have arrow at the top to the Left.
Arrow at the collapsing floors to the Right.
Big arrow centre of gravity which has already shifted from the centre as heading down.
STUPID OR WHAT -
FIG4 E
They have collapsing columns with big Arrow down as summary of two arrows. THIS IS SCIENTIFIC BS.
It is laughable. imho.
HAVE YOU SERIOUSLY SAT DOWN AND READ THERE ANALYSIS??? I BEG YOU, I IMPLORE YOU PLEASE LOOK AT THEIR DIAGRAMS AND READ THEIR TOSH.
Here are some lines from their report.
1. Columns exposed to temperatures
apparently exceeding 800C? Do they know this or not??? Apparently doesn't suit the gravity of event. Metal needs to be around 2500C before it starts melting.
2. Corrugated floors may bend but their collapse is debatable? Assuming they have collapsed does not explain the dissapearance of peripheral or core columns. To suggest whole building vapourised is DAFT BEYOND BELIEF.
3. Floors collapse gathering speed. NO WAY. Look imagine two parachuters free falling to the ground. Their parachutes have failed. One hits the ground unimpeded.
The other hits the ground falling through trees.
WHICH PARACHUTIST IS GOING TO HIT THE GROUND FIRST and
WHAT SPEED WILL EACH PARACHUTIST WILL HIT THE GROUND AT?
How can these idiots use hot and cold metal and different strengths to justify the whole building wait being supported FIG3. a - due to support of cold metal structure and then say building falls at free fall speed gathering speed on the other.
4. These IDIOTS talk about equilibrium weight of the building but THIS IS SIMPLY NOT THE CASE THE MOMENT TOWER LEANS 23 DEGREES. CENTRE OF GRAVITY HAS NOW SHIFTED AND EQUILIBRIUM IS NO MORE.
So how can they talk about
For our purpose, we may assume that all the impact forces go
into the columns and are distributed among them equally(STUPID ASSUMPTION AS YOU CAN'T GET AS THIS IS OBVIOUSLY NOT THE CASE AS BUILDING HAS TWISTED OUT 23 DEGREES. Unlikely
though such a distribution may be, (TOO DAMN RIGHT!) it is nevertheless the
most optimistic hypothesis to make because the resistance of the
building to the impact is, for such a distribution, the highest. (UTTER IDIOTS. YES COLUMN RESISTANCE STRONGEST AND SHOULD EXPLAIN SOME CORRUGATED FLOORS GIVING WAY OR BENDING TO HEAT BUT NOT COLUMNS COLLAPSING If the
building is found to fail under a uniform distribution of the impact
forces, it would fail under any other distribution (WHAT A LOAD OF DRIBBLE. YOU CAN'T SAY THIS FULL STOP. According to
this hypothesis, one may estimate (IS THIS THE EXTENT OF THEIR SCIENTIFIC ESTIMATION that C'71 GN/m ~due to unavailability
of precise data, an approximate design of column
cross sections had to be carried out for this purpose!.WHY DOES THE WHITE HOUSE FEEL WE DO NOT NEED TO HAVE THIS INFORMATION???
I have really studied this article and gone over several readings and you can tear it apart.
My economics dissertation was more thorough than this... And I got torn to pieces by my Professor Dunning asking me to explain and justify my assumptions and figures and where I had obtained them and what due dilligence I applied in determining if the figures I was reading were not error prone and whether there were related stats from other countries I could refer to to collobrate my findings.
OK FINALLY - THERE ADDENDUM
Didn’t Plastic Deformations ‘‘Cushion’’ the Vertical
Impact?
It has been suggested that the inelastic deformations of columns,
analyzed in Appendix II of Bazˇant and Zhou ~2002!, might have
significantly ‘‘cushioned’’ the initial descent of the upper part,
making it almost static. However, this is impossible because, for
gravity loading, a softening of the load-deflection diagram @Fig. 5
in Bazˇant and Zhou ~2002!# always causes instability that precludes
static response ~Bazˇant and Cedolin 1991, Chapters 10 and
13!. The downward acceleration of the upper part is u¨5N@P1 0
2P1(u)#/m where N5number of buckling columns in the floor
and, necessarily, P1 0 5mg/N. This represents a differential equation
for u as a function of time t. Its integration shows that the
time that the upper part takes to fall through the height of one
story is, for cold columns, only about 6% longer than the duration
of a free fall from that height, which is 0.87 s. For hot columns,
the difference is of course much less than 6%. So there is hardly
any ‘‘cushioning.’’ It is essentially a free fall.[/I]
They are in their own addendum pointing out my primary objection to their analysis between hot and cold metal resistance as well as strength of those columns and dismiss it off hand by a mere factor of 6%. ABSOLUTELY STUPID COMMENT TO MAKE! NO WAY.
Calming down now but essentially having been heavily absorbed in some of these documents the crux of their argument is the heat caused the corrugated floors to bend and collapse. Other than this I am absolutely flabberghasted as to how any decent individual with any scientific logic can take their article as having any merit at all.
Even economists make more plausible assumptions than these nit twits.
I reckon at best these people wrote this article to gain some free advertising for their experteese in explaining the collapse and failing to do so miserably.
I've read their article three times - pondering over it. I do hope you provide me the courtesy to open up the PDF and study diagrams and what exactly they are putting to you with same serious approach.
I've had a really good time too. Nice to tax the grey cells. :cheesy:
Can you please watch the 9/11 Mysteries with due respect and provide me your thoughts in turn.