Twin Towers-Mechanical Physics

[timeparticle]

On 911, The Twin Towers in New York, each fell directly and exactly down, as if they were imploded due to precise demolition.

Without accusing anyone of sabotage, is it possible that two random jets that strike each building, in different areas and different angles, can bring these buildings down as they did with quick burning jet fuel?

This is merely a scientific question and has no political basis.


You can demolish a stone wall with a sledgehammer, and it's fairly easy to level a five-story building using excavators and wrecking balls. But when you need to bring down a massive structure, say a 20-story skyscraper, you have to haul out the big guns. Explosive demolition is the preferred method for safely and efficiently demolishing larger structures. When a building is surrounded by other buildings, it may be necessary to "implode" the building, that is, make it collapse down into its footprint.

Demolition blasters load explosives on several different levels of the building so that the building structure falls down on itself at multiple points. When everything is planned and executed correctly, the total damage of the explosives and falling building material is sufficient to collapse the structure entirely, so cleanup crews are left with only a pile of rubble.

In order to demolish a building safely, blasters must map out each element of the implosion ahead of time. The first step is to examine architectural blueprints of the building, if they can be located, to determine how the building is put together. Next, the blaster crew tours the building (several times), jotting down notes about the support structure on each floor. Once they have gathered all the raw data they need, the blasters hammer out a plan of attack. Drawing from past experiences with similar buildings, they decide what explosives to use, where to position them in the building and how to time their detonations. In some cases, the blasters may develop 3-D computer models of the structure so they can test out their plan ahead of time in a virtual world.

The main challenge in bringing a building down is controlling which way it falls. Ideally, a blasting crew will be able to tumble the building over on one side, into a parking lot or other open area. This sort of blast is the easiest to execute, and it is generally the safest way to go. Tipping a building over is something like felling a tree. To topple the building to the north, the blasters detonate explosives on the north side of the building first, in the same way you would chop into a tree from the north side if you wanted it to fall in that direction. Blasters may also secure steel cables to support columns in the building, so that they are pulled a certain way as they crumble.

Sometimes, though, a building is surrounded by structures that must be preserved. In this case, the blasters proceed with a true implosion, demolishing the building so that it collapses straight down into its own footprint (the total area at the base of the building). This feat requires such skill that only a handful of demolition companies in the world will attempt it.

Blasters approach each project a little differently, but the basic idea is to think of the building as a collection of separate towers. The blasters set the explosives so that each "tower" falls toward the center of the building, in roughly the same way that they would set the explosives to topple a single structure to the side. When the explosives are detonated in the right order, the toppling towers crash against each other, and all of the rubble collects at the center of the building. Another option is to detonate the columns at the center of the building before the other columns so that the building's sides fall inward.

Intense heat can bend and distort metal into amazing shapes as in the aftermath of an atomic blast. It has been determined that jet fuel created the intense heat to bring the towers down.

My question to you is, is this possible in the realm of mechanical physics?

[timeparticle]

This is a picture of a building melted by intense thermal nuclear heat. The metal is twisted and bent in odd shapes. This is what I would expect the Towers to look like after the metal structure melted. I wouldn't think they would perfectly implode.

[timeparticle]

PRISON PLANET.com Copyright � 2002-2004 Alex Jones All rights reserved.



The following letter was sent today by Kevin Ryan of Underwriters Laboratories to Frank Gayle of the National Institute of Standards and Technology (NIST). Underwriters Laboratories is the company that certified the steel componets used in the constuction of the World Trade Center towers. The information in this letter is of great importance.

Dr. Gayle,

Having recently reviewed your team's report of 10/19/04, I felt the need to contact you directly.

As I'm sure you know, the company I work for certified the steel components used in the construction of the WTC buildings. In requesting information from both our CEO and Fire Protection business manager last year, I learned that they did not agree on the essential aspects of the story, except for one thing - that the samples we certified met all requirements. They suggested we all be patient and understand that UL was working with your team, and that tests would continue through this year. I'm aware of UL's attempts to help, including performing tests on models of the floor assemblies. But the results of these tests appear to indicate that the buildings should have easily withstood the thermal stress caused by pools of burning jet fuel.

There continues to be a number of "experts" making public claims about how the WTC buildings fell. One such person, Dr. Hyman Brown from the WTC construction crew, claims that the buildings collapsed due to fires at 2000F melting the steel (1). He states "What caused the building to collapse is the airplane fuel…burning at 2,000 degrees Fahrenheit. The steel in that five-floor area melts." Additionally, the newspaper that quotes him says "Just-released preliminary findings from a National Institute of Standards and Technology study of the World Trade Center collapse support Brown’s theory."

We know that the steel components were certified to ASTM E119. The time temperature curves for this standard require the samples to be exposed to temperatures around 2000F for several hours. And as we all agree, the steel applied met those specifications. Additionally, I think we can all agree that even un-fireproofed steel will not melt until reaching red-hot temperatures of nearly 3000F (2). Why Dr. Brown would imply that 2000F would melt the high-grade steel used in those buildings makes no sense at all.

The results of your recently published metallurgical tests seem to clear things up (3), and support your team's August 2003 update as detailed by the Associated Press (4), in which you were ready to "rule out weak steel as a contributing factor in the collapse." The evaluation of paint deformation and spheroidization seem very straightforward, and you noted that the samples available were adequate for the investigation. Your comments suggest that the steel was probably exposed to temperatures of only about 500F (250C), which is what one might expect from a thermodynamic analysis of the situation.

However the summary of the new NIST report seems to ignore your findings, as it suggests that these low temperatures caused exposed bits of the building’s steel core to "soften and buckle." (5) Additionally this summary states that the perimeter columns softened, yet your findings make clear that "most perimeter panels (157 of 160) saw no temperature above 250C." To soften steel for the purposes of forging, normally temperatures need to be above1100C (6). However, this new summary report suggests that much lower temperatures were be able to not only soften the steel in a matter of minutes, but lead to rapid structural collapse.

This story just does not add up. If steel from those buildings did soften or melt, I’m sure we can all agree that this was certainly not due to jet fuel fires of any kind, let alone the briefly burning fires in those towers. That fact should be of great concern to all Americans. Alternatively, the contention that this steel did fail at temperatures around 250C suggests that the majority of deaths on 9/11 were due to a safety-related failure. That suggestion should be of great concern to my company.




Popular Mechanics says it is possible...

Debunking the 9/11 Myths: Special Report
Popular Mechanics examines the evidence and consults the experts to refute the most persistent conspiracy theories of September 11.

FACT: Jet fuel burns at 800° to 1500°F, not hot enough to melt steel (2750°F). However, experts agree that for the towers to collapse, their steel frames didn't need to melt, they just had to lose some of their structural strength — and that required exposure to much less heat. "I have never seen melted steel in a building fire," says retired New York deputy fire chief Vincent Dunn, author of The Collapse Of Burning Buildings: A Guide To Fireground Safety. "But I've seen a lot of twisted, warped, bent and sagging steel. What happens is that the steel tries to expand at both ends, but when it can no longer expand, it sags and the surrounding concrete cracks."

"Steel loses about 50 percent of its strength at 1100°F," notes senior engineer Farid Alfawak-hiri of the American Institute of Steel Construction. "And at 1800° it is probably at less than 10 percent." NIST also believes that a great deal of the spray-on fireproofing insulation was likely knocked off the steel beams that were in the path of the crashing jets, leaving the metal more vulnerable to the heat.

But jet fuel wasn't the only thing burning, notes Forman Williams, a professor of engineering at the University of California, San Diego, and one of seven structural engineers and fire experts that PM consulted. He says that while the jet fuel was the catalyst for the WTC fires, the resulting inferno was intensified by the combustible material inside the buildings, including rugs, curtains, furniture and paper. NIST reports that pockets of fire hit 1832°F.

"The jet fuel was the ignition source," Williams tells PM. "It burned for maybe 10 minutes, and [the towers] were still standing in 10 minutes. It was the rest of the stuff burning afterward that was responsible for the heat transfer that eventually brought them down."

FACT: Once each tower began to collapse, the weight of all the floors above the collapsed zone bore down with pulverizing force on the highest intact floor. Unable to absorb the massive energy, that floor would fail, transmitting the forces to the floor below, allowing the collapse to progress downward through the building in a chain reaction. Engineers call the process "pancaking," and it does not require an explosion to begin, according to David Biggs, a structural engineer at Ryan-Biggs Associates and a member of the American Society of Civil Engineers (ASCE) team that worked on the FEMA report.

I did not see that, PM. The collapse began at the base. There was no "pancake" effect.

Like all office buildings, the WTC towers contained a huge volume of air. As they pancaked, all that air — along with the concrete and other debris pulverized by the force of the collapse — was ejected with enormous energy. "When you have a significant portion of a floor collapsing, it's going to shoot air and concrete dust out the window," NIST lead investigator Shyam Sunder tells PM. Those clouds of dust may create the impression of a controlled demolition, Sunder adds, "but it is the floor pancaking that leads to that perception."

This is interesting. There was no cloud of dust before the towers collapsed to impinge our view. The smoke from the fire was rising.

Demolition expert Romero regrets that his comments to the Albuquerque Journal became fodder for conspiracy theorists. "I was misquoted in saying that I thought it was explosives that brought down the building," he tells PM. "I only said that that's what it looked like."

And it looked like that to me, too.

U.L seems to find that the high grade metal structure couldn't have melted.

[neutralino]

Without accusing anyone of sabotage, is it possible that two random jets that strike each building, in different areas and different angles, can bring these buildings down as they did with quick burning jet fuel?

Yes, as we saw on 9/11.

Seriously, I'm amazed* that people are still debating this!

* Well, I'm not amazed, since some people are obsessed with conspiracy theories, but I'd imagine that these people would have listened to the professionals by now!

[timeparticle]

Yes, as we saw on 9/11.

Seriously, I'm amazed* that people are still debating this!

* Well, I'm not amazed, since some people are obsessed with conspiracy theories, but I'd imagine that these people would have listened to the professionals by now!

The reason why I asked this on a TOE site is to get an intelligent explanation of how this can occur under the normal laws of Physics. I am not debating on a conspiracy theory.
Conspiracy theories are being debated on other sites.

This is purely a scientific question of mechanical physics on how two massive structures can be brought down without careful and systematic demolition dynamics.

[PoPpAScience]

It amazes me also Neuralino, to see anyone question what was so absolutely obvious, watching the buildings fall live. Then to watch the replay's and see the most basic of logical conclusion of what happen.

For those who did not see the obvious, here is what happen: The floors that were impacted by the planes were weakened by damage to the supporting metal beams that hold the weight of the upper floors. Some support beams were damaged from impact and others where weakened by the heat of burning jet fuel and other materials on the floors. The beams were not melted, only weakened.

What happen next is absolute, except for those who have a hard time witnessing reality. The upper mass of the buildings, above the weakened floors, fell straight downwards, when the damaged floors collapsed from impact and heat damaged. The mass of the upper floors propelled by gravity spilt and demolished the lower floors as they fell to the ground. As each floor was gathered up by the falling mass, the falling mass became more massive and destructive as it fell, pulverizing the towers into dust and bent steel.

"The towers were devoured by mass, propelled by gravity."

All replays show the towers being destroyed from the top down.

Those who question the absolute obvious of what happen to the towers, prove my point that I have stated a few times in this web site and others, that there are minds of some individuals that can exist in a state of absolute delusion. That no matter how much information is put before their eyes, their minds will not be able to absorb the information because of restrictions of thought. Unfortunately, these restrictive minds dominate our society this days.

[austintorn@aol.com]

In the failed attempt in the early 90's, by putting explosives in the parking garage, the terrorists were trying to fell the building like a tree, perhaps to cause even more damage to the surrounding buildings.

The ideas from the mythic age linger on, unfortunately, as they are deeply ingrained.

[Mikal]

Wow....there is some pretty strong judgement calls here about TP, strong assumptions and rather unfair if you read the first post correctly to see that TP would like to discuss this phenomenon in relation to the Laws of Physics.

Its just my opinion guys but some sincere apologies might be in order!



Mikal

[timeparticle]

A Pancake Collapse would look like a stack of pancakes as an end result, like this earthquake scene.

Now, let's talk science...


Momentum Transfer Analysis of the Collapse of the Upper Storeys of WTC 1

Author:
The author of this work, Gordon Ross, was born in Dundee, Scotland. He holds degrees in
both Mechanical and Manufacturing Engineering, graduating from Liverpool John
Moores University, in 1984. He can be contacted at gordonjross@yahoo.com.

Summary:
This paper examines the elastic loading and plastic shortening phases of the columns of WTC 1
after impact of the upper 16 storeys of the building upon the lower storeys and its effect on the
momentum transfer after the collision. An energy balance is derived showing that there is an energy
deficit before completion of the plastic shortening phase that would not allow the collapse to continue
under the constraints of this paper.

Introduction:
Previous analysis of the momentum transfer in the collapse of the towers has viewed
them as being floors suspended in space and have examined the momentum transfer as a series of
elastic or inelastic collisions, which are independent of each other. This type of analysis takes the
momentum transfer out of the context given by the other effects of the collisions. This is because
this type of analysis assumes that the impacts have an effect upon only the topmost storey of the
impacted section. The reality of the situation is that the impacts would have an effect upon
several storeys in the lower section and for a valid analysis all of these momentum transfers must
be included.

If we assume that the upper section comprising 16 storeys falls under a full gravitational
acceleration through a height of one (removed) storey, a distance of 3.7 metres we can calculate
that its velocity upon impact will be 8.52 metres per second and have a kinetic energy due to its
mass and velocity of 2.105 GJ. (Using the figure of 58000 tonnes as detailed in the report by
Bazant & Zhou.[1]) In reality there would be some losses of energy due to residual strength
within the failing columns of the removed section, but these are ignored for the purposes of this
analysis.

Upon impact with the lower section the falling mass would deliver a force which would
grow from zero, up to the failure load of the impacted storey columns, over a finite period of
time and distance.

This force would also be felt by the columns below the storey which was first impacted.

Analysis:
The falling upper section with a velocity of no more than 8.5 metres per second at impact
would meet resistance from the impacted columns and have as its first task the necessity to load
these columns through their elastic range and thereafter through the plastic shortening phase. We
shall firstly examine this incremental time period.

Bazant/Zhou [1] show in their analysis that elastic and plastic behaviour of a steel column
under a dynamic buckling load can be shown to consist of three distinct phases. These can be
shown on a load against vertical deflection graph and consist of an initial elastic phase, a
shortening phase and a rapid plastic deformation phase.

1/ The elastic phase shows a linear relationship between load and deflection up to the
elastic limit. The load at this point is the failure load and the deflection at the elastic
limit for steel is generally 0.2% of the initial length.
2/ The shortening phase allows for the same failure load to be applied until the vertical
deformation reaches 3% at which point the column begins to form buckle points.
3/ The third phase shows a rapid decrease in the load requirement to continue
deformation, this load necessarily being less than the failure load. This phase lasts until
the total vertical deformation equals the original length. In other words the column is
bent in two.
To shorten the columns of the first impacted storey by 3%, sufficient to complete the
plastic shortening phase, a distance of about 0.111 metres, and allowing a constant speed of 8.5
metres per second, would take a minimum of 0.013 seconds.

The speed of the propagation wave through a medium is given by the general formula for
wave propagation
Velocity = Square root ( Bulk modulus / Density ),
and for structural steel is of the order of 4500 metres per second.
The propagation wave of the impact force would therefore travel a distance of 58.7 metres in a
time of 0.013 seconds. This means that during the time taken in the plastic shortening of the
impacted columns, the same force would be felt at a minimum distance of 58.7 metres, or
approximately 16 storeys, from the impact. These storeys would thus suffer an elastic deflection
in response to, and proportional to, the failure load applied at the impacted floor. These
deflections would themselves take time and allow the propagation wave to move further
downwards again affecting more storeys.
We can estimate the elastic deflection of these 16 storey columns as being in the range 0
to 7mm. The full elastic deflection of a 3.7m column, using the generally accepted figure of
0.2% of its original length is 7.4mm. The columns in the uppermost of these storeys would suffer
almost their full elastic deflection since their failure load is similar though slightly greater than
that of the first impacted storey. Those storey columns more distant from the impact would be of
a larger cross section, requiring higher loads to cause full elastic deflection. Using only half of
the maximum elastic deflection, 56mm (16 * 7 / 2), is, again, an assumption in favour of collapse
continuation.

The elastic deflection of lower storeys would increase the distance through which the
falling section would have to move in order to load the impacted column and complete its 3%
plastic shortening. The time taken, again using a constant velocity of 8.5 m/sec would increase to
about 0.02 seconds, and thus allow the propagation wave to move through and affect a further 8
storeys.





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[timeparticle]

Because these columns suffer a vertical deflection, the attached floors move downwards
and they will therefore have a velocity and momentum.
Energy Losses:
A simple conservation of momentum calculation, ignoring these movements, would have,
16 falling storeys moving at 8.5 m/sec before impact, changing to 17 storeys moving at (8.5 *
(16/17)) = 8 m/sec after impact. This does not reflect the fact that a minimum of 24 further
storeys will be caused to move downwards at varying speeds.

To estimate and illustrate the further momentum changes we can assume that the storey
which is 25 storeys from the impact remains static and the velocity of the 24 affected storeys will
vary linearly from the velocity of the falling section to zero.


Momentum before impact = 16 storeys moving at 8.5 m/sec
Momentum after impact = 17 storeys moving at V2 m/sec + 1 storey moving at 23/24*V2 m/sec
+ 1 storey moving at 22/24*V2m/sec +……+ 1 storey moving at 2/24*V2 m/sec + 1 storey
moving at 1/24*V2m/sec 16*8.5 = V2 (17 + 11.5)

V2 = 16 * 8.5 / 28.5 = 4.8 metres per second.

The speed of the upper section would be reduced by the collision from
8.5 m/sec to a speed of less than 4.8 m/sec rather than the 8 m/sec derived from a momentum
calculation which does not include this factor. Note also that this reduction in speed would again
give more time for the propagation wave to travel downwards through the tower columns and
allow that more and more storeys are so affected.
The kinetic energy of the falling section would be similarly affected, but because of the
velocity squared relationship, the reduction in kinetic energy would be more pronounced.

K. E. of falling section before impact = 16 floors moving at (8.5 m/sec)

K. E. of falling section after impact = 17 floors moving at (4.8 m/sec)

Percentage loss of K.E. = 1-(17 * 4.8/ (16 *8.5) * 100% = 66%

This is an underestimation of the energy loss, since the deceleration would allow more
time for travel of the propagation wave and so allow more floors to be affected but even this
shows an energy absorption of some 66% of the total kinetic energy of the falling section.

Energy Balance:
Since there was only some 2.1 GJ available at the point of impact of the first collision, a
loss of 66% would reduce this figure to 714 MJ.
The kinetic energy would be augmented by potential energy released in the further downward
movement of the falling mass and if we assume that this falls through the full distance of the 3%
shortening phase of the impacted floor and the elastic deflection of the lower storeys, then the
additional potential energy is
58*10* g * (0.111 + .056) = + 95MJ.
The strain energy consumed by the impacted storey columns in the elastic phase and
plastic shortening phase can be calculated using the failure load. The failure load used
throughout this analysis is derived using the mass above the impact, 58 000 tonnes, and a safety
factor of 4. Examination of the column geometry with reference to the Euler equations show that
this is an underestimation both of the failure load and the distance over which it would have to
act before failure, and this gives a gross assumption in favour of collapse continuation. A factor
of 0.029 is included to reflect the load profile over the 3% plastic shortening phase. The load
profile exhibits a linear rise from zero to failure load at 0.2% of the length, followed by a
constant failure load over the next 2.8% of the length.

Plastic strain energy:
58*10kg*4*g*3.7m*0.029= -244MJ.
A similar though slightly smaller figure would be required for the first impacting storey
in the upper falling section. Because this storey carried a lower load, 15 storeys, than the
impacted storey, 17 storeys, its designed capabilities would be proportionately smaller.
Using this knowledge an estimation can be made that the energy consumed by this storey would
be,
(244 MJ * 15 / 17) = -215MJ .
The elastic response of the lower storey columns within their elastic range would make
further demands on the energy available by absorption of energy in the form of strain energy.
This can be estimated, using a safety factor of 4, a mass of 58000 tonnes, a distance of
0.056metres, and a factor of 0.5 to reflect the load profile

58*10kg*4*g*0.056metres*0.5= -64MJ.
The downward movement of these floors in response to the impact will release additional
potential energy due to their compression and using the same deflections as above and a value
for mass proportionate to the number of storeys, this will release
58*10kg * 24/16 * g * 0.056metres / 2 = + 24 MJ.
Further energy losses are evident in an analysis of the compression of storeys within the
upper falling section. These storeys manufactured from columns with a smaller cross section
than those at the impact, would be unable to withstand the failure load present at the impact front
and would suffer plastic deformation beyond their elastic limit, but for simplicity, it is assumed
that they suffer only their full elastic deflection. This is another large assumption in favour of
collapse continuation.

The total deflection would be 15 storeys multiplied by the elastic deflection of 7.4mm,
and strain energy consumed can be estimated as,
15*7.4*10*4*58*10*g/2= -126MJ.
Movement of the storeys within the upper section will release additional potential energy
due to their compression and consequent movement. It is likely that this energy would manifest
itself as failures within the upper section, but has nevertheless been added as an energy available
for collapse continuation. The uppermost storey will move downwards by 15 times the elastic
deflection whereas the lowest will remain static, both in relation to the impact point, giving
additional potential energy as,
15*0.0074*58*10*g/2= +32MJ
A considerable amount of energy would be required to pulverise the concrete into the fine
dust which was evident from the photographic and other evidence. To quantify this energy it is
necessary to use the fracture energy value, but this has a variable value dependent on, among
other factors, the size of the concrete piece, and its constituents, most notably, aggregate size.
There is no typical value.

In order to assess the energy consumed I will refer to the work of Dr. Frank Greening [2].
It should be noted that Dr. Greening, like Dr. Bazant, does not, as yet, support the contention that
the tower collapse was caused by anything other than the damage caused by aircraft impact and
subsequent and consequent fires.