To add comments or start new threads please go to the full version of: The Physics Behind 9/11's 3 Towers 'collapse'
PhysForum Science, Physics and Technology Discussion Forums > Physics > Physics General

Fizical
A resource presenting evidence showing the 3 towers were brought down by internally placed explosives:

worldarchitecturenews [dot] com/index.php?fuseaction=wanappln.commentview&comment_id=158

A Resource giving evidence for the offical story that the 3 buildings came down by damage sustained by the 2 planes and subsequent fires:

debunking911 [dot] com

Please note - I'm trying to stick to the physical evidence here, not theories.
Sorry about not being able to link... can someonw else link for me? smile.gif
Fizical
One KEY PIECE OF EVIDENCE is the admition by NIST (in August 2008) that the WTC7 Building did fall at freefall speed for 2.25 seconds.

The only way this can happen is if the structure below the freefalling part has been 'removed'
rpenner
Nope. It just would have had to fallen first, which is practically the definition of collapse predicated on structural failure.

How shocking that your whole conspiracy plot vanishes when confronted with the least bit of physics, economics or psychological analysis. Just because CNN won't call you crazy to your face doesn't mean your position isn't crazy, ignorant and deceitful.
Fizical
QUOTE (rpenner+Sep 11 2009, 02:25 PM)
Nope. It just would have had to fallen first, which is practically the definition of collapse predicated on structural failure

Where would the lower structure "fallen" to? why would it not have gotten in the way of the building above it?

If the lower florrs had suddenly collapsed - there would still be huge amounts of debris in the path of the upper floors. this debris would have slowed the upper floors down, not just allowed them to fall at free fall speed. How else could you explain the freefall speed of the building.

(google video / youtube "WTC7" to see it for yourself at real time speed)
flyingbuttressman
QUOTE (Fizical+Sep 11 2009, 10:37 AM)
Where would the lower structure "fallen" to? why would it not have gotten in the way of the building above it?

If the lower florrs had suddenly collapsed - there would still be huge amounts of debris in the path of the upper floors. this debris would have slowed the upper floors down, not just allowed them to fall at free fall speed. How else could you explain the freefall speed of the building.

Do you think it was magically "beamed up" by space aliens?

Buildings are mostly empty space, as anyone who has been inside one should know.

Freefall is defined as 9.8 m/s^2. Nothing can fall faster or slower than that unless it is acted upon by another force.
Fizical
QUOTE (flyingbuttressman+Sep 11 2009, 02:42 PM)
Do you think it was magically "beamed up" by space aliens?

Buildings are mostly empty space, as anyone who has been inside one should know.

Freefall is defined as 9.8 m/s^2. Nothing can fall faster or slower than that unless it is acted upon by another force.

haha, not sure about the aliens, I havent seen any yet.

exaclty - "9.8 m/s^2 Nothing can fall faster or slower than that unless it is acted upon by another force"

If the building collapsed downwards due to gravity alone, there is still a force stopping the building falling to the cente of the earth - namely that of the ground and subsequent build up of debris.

How do you explain the lack of complete resistance and freefall for 2.25 seconds?? Surely you are not suggesting *all* inheriant strength of a building is *completely* lost when a collapse begins?
flyingbuttressman
QUOTE (Fizical+Sep 11 2009, 10:54 AM)
If the building collapsed downwards due to gravity alone, there is still a force stopping the building falling to the cente of the earth - namely that of the ground and subsequent build up of debris.

How do you explain the lack of complete resistance and freefall for 2.25 seconds?? Surely you are not suggesting *all* inheriant strength of a building is *completely* lost when a collapse begins?

Once the structural support fails at a point where the kinetic energy of the above stories falling 15 feet cannot be resisted by the supports below, there is a chain reaction of structural failure. Since concrete has 0 ability to bend under pressure, it practically explodes when it fails. The resistance against falling is present, but it is shattered too quickly to really slow down the majority of falling mass.

In short, the collapsing velocity of a building increases at less than 9.8 m/s^2, but there is not enough of a difference to be immediately visible to the naked eye.
Fizical
QUOTE (flyingbuttressman+Sep 11 2009, 03:17 PM)
Once the structural support fails at a point where the kinetic energy of the above stories falling 15 feet cannot be resisted by the supports below, there is a chain reaction of structural failure. Since concrete has 0 ability to bend under pressure, it practically explodes when it fails.

interesting. The same cannot be true for the "steel beams, girders and trusses" that were also used in the construction of the WTC7 building.

Steel doesn't explode when put under pressure like you say concrete does... Well, not of it's own accord anyway.
flyingbuttressman
QUOTE (Fizical+Sep 11 2009, 12:35 PM)
interesting. The same cannot be true for the "steel beams, girders and trusses" that were also used in the construction of the WTC7 building.

Steel doesn't explode when put under pressure like you say concrete does... Well, not of it's own accord anyway.

There was a visible bulge in the side of WTC 7 before it collapsed. That's a sign of the steel frame bending and buckling. Obviously not explosives. Why is it so hard to believe that fire can collapse a building?
Fizical
QUOTE (flyingbuttressman+Sep 11 2009, 04:50 PM)
There was a visible bulge in the side of WTC 7 before it collapsed. That's a sign of the steel frame bending and buckling. Obviously not explosives. Why is it so hard to believe that fire can collapse a building?

So you do not have any reasonable explanation as to why the strong steel parts of the building suddenly dissapeared, fooled the laws of physics and allowed the building to fall at freefall speed?

Where is this "visiable buldge"? Do you have a picture? a video? I would be very interested to see some evidence as I'm interested in the truth, provable by facts.

Official story "evidence" has always been noted for it's lack of substance. eg. on the alleged 'de-bunker' site the text will say 'check out this video to see the massive hole in th building.. (wtc7) and when u watch it there it is noot visable.

It is perfectly believable that a fire CAN cause a buildings collapse. evidence inthe 9/11 case does not suggest this. by the way these are the only steel framed buildings ever to have been alledged to have collapsed due to fire. Other examples exsist of these buildings on fire for days... parts have collapsed buth the steel remains.
flyingbuttressman
QUOTE (Fizical+Sep 11 2009, 01:54 PM)
Where is this "visiable buldge"? Do you have a picture? a video? I would be very interested to see some evidence as I'm interested in the truth, provable by facts.

Official story "evidence" has always been noted for it's lack of substance. eg. on the alleged 'de-bunker' site the text will say 'check out this video to see the massive hole in th building.. (wtc7) and when u watch it there it is noot visable.

Yes, all the firefighters carried around video cameras so that idiots like you would believe their stories 8 years later. /sarcasm

You're not looking for the truth, you're looking for a conspiracy.

Conspiracy theorists have very little interest in facts; their own opinions come first.
RobDegraves
QUOTE
by the way these are the only steel framed buildings ever to have been alledged to have collapsed due to fire. Other examples exsist of these buildings on fire for days... parts have collapsed buth the steel remains.


Nope.

QUOTE (->
QUOTE
by the way these are the only steel framed buildings ever to have been alledged to have collapsed due to fire. Other examples exsist of these buildings on fire for days... parts have collapsed buth the steel remains.


Nope.

Two large department store fires in Athens, Greece, in 1980 are documented in the paper by Kyriakos Papaioannoa, 1986.4 These fires began at 3 a.m. on Dec. 19, 1980, with arson being suspected as the cause. The Katrantzos Sport Department Store was an 8-story reinforced concrete building. Its fire started at the 7th floor and rapidly spread throughout the building, due to lack of vertical or horizontal compartmentation and the absence of sprinklers. Collected evidence indicated that the fire temperatures reached 1000°C over the 2- to 3-hour fire duration, and the firefighters concentrated on containing the fire spread to the adjacent buildings. Upon termination of these fires, it was discovered that a major part of the 5th to 8th floors had collapsed. Various other floor and column failures throughout the Katrantzos Building were also observed (see Figure 1). The cause of these failures was considered to be restraint of the differential thermal expansion of the structure that overloaded its specific elements or connections. On May 21, 1987, Sao Paulo had one of the biggest fires in Brazil, which precipitated a substantial partial collapse of the central core of the tall CESP Building 2.5 This was a 21-story office building, headquarters of the Sao Paulo Power Company (CESP), after whom the building was named. Buildings 1 and 2 of this office complex were both of reinforced concrete framing, with ribbed slab floors. These two buildings had several unique internal features and contents. Both buildings still retained their original wood forms used for pouring the concrete floor slabs, which were never removed. Low-height plywood partition walls were also used in the interiors. Approximately two hours after the beginning of the fire in CESP 2, its structural core area throughout the full building height collapsed. This collapse was attributed to the thermal expansion of the horizontal concrete T-beam frames under the elevated fire temperatures, which led to the fracture of the vertical framing elements and their connections in the middle of the building, and the consequent progressive loss of gravity load-carrying capacity (see Figure 2).

A fire-initiated full collapse of a textile factory occurred in Alexandria, Egypt, on July 19, 2000.6 This 6-story building was built of reinforced concrete, and its fire started at about 9 a.m. in the storage room at the ground floor. Fire extinguishers were nonfunctional, and the fire spread quickly before the firefighters could arrive. An electrical short-circuit accelerated the fire spread. At about 6 p.m., nine hours after the start of the fire, when the blaze seemingly was under control and subsiding, the building suddenly collapsed, killing 27 people. Figure 3 shows a photograph of this collapse.


Fire Protection Engineering


The official story has piles of evidence.

Your conspiracy theory has none.

It might also help if you learned to spell.... just as a bonus. That way people might not come to the immediate conclusion that you are too ignorant to take seriously. Just a hint, assuming that you do want people to take you seriously.

Fizical
I say again - the WTC buildings are the only STEEL FRAME buildings ever to have aledgely collpased due to fire. The comment you posted never mentions steel and clearly states "This collapse was attributed to the thermal expansion of the horizontal concrete T-beam frames"

My comment still stand un-disputed - There are no other steelframe buildings to have collapsed due to fire.

Absolutely I want to be taken serisously. You claim I have presented no evidence. Did you read any of the link I presented? It's called evidence.

If you want to be taken seriously then please present everyone with some evidence to actually prove my evidence wrong. Iwant it not to be an inside job.

Please present me some accurate mathematics (or even a solid argument) of how a building can fall at freefall for 2.25 seconds without 'removing' the lower floors.
flyingbuttressman
QUOTE (Fizical+Sep 11 2009, 04:37 PM)
Absolutely I want to be taken serisously. You claim I have presented no evidence. Did you read any of the link I presented? It's called evidence.

HAHAHAHAHAHAHAHAHAHHAHHAHHAHAHHA
RobDegraves
Sigh...

QUOTE
This 6-story building was built of reinforced concrete,


QUOTE (->
QUOTE
This 6-story building was built of reinforced concrete,


Reinforced concrete is concrete in which steel reinforcement bars ("rebars"), plates or fibers have been incorporated to strengthen a material that would otherwise be brittle.


And...

QUOTE
Three physical characteristics give reinforced concrete its special properties. First, the coefficient of thermal expansion of concrete is similar to that of steel, eliminating internal stresses due to differences in thermal expansion or contraction. Second, when the cement paste within the concrete hardens this conforms to the surface details of the steel, permitting any stress to be transmitted efficiently between the different materials. Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel. Third, the alkaline chemical environment provided by calcium carbonate (lime) causes a passivating film to form on the surface of the steel, making it much more resistant to corrosion than it would be in neutral or acidic conditions.



Here is a question to answer your question...


How many steel frame building were ever hit by 747's?


Edited to add...


QUOTE (->
QUOTE
Three physical characteristics give reinforced concrete its special properties. First, the coefficient of thermal expansion of concrete is similar to that of steel, eliminating internal stresses due to differences in thermal expansion or contraction. Second, when the cement paste within the concrete hardens this conforms to the surface details of the steel, permitting any stress to be transmitted efficiently between the different materials. Usually steel bars are roughened or corrugated to further improve the bond or cohesion between the concrete and steel. Third, the alkaline chemical environment provided by calcium carbonate (lime) causes a passivating film to form on the surface of the steel, making it much more resistant to corrosion than it would be in neutral or acidic conditions.



Here is a question to answer your question...


How many steel frame building were ever hit by 747's?


Edited to add...


Steel frame usually refers to a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.


QUOTE
The frame needs to be protected from fire because steel softens at high temperature and this can cause the building to partially collapse. In the case of the columns this is usually done by encasing it in some form of fire resistant structure such as masonry, concrete or plasterboard. The beams may be cased in concrete, plasterboard or sprayed with a coating to insulate it from the heat of the fire or it can be protected by a fire resistant ceiling construction.
buttershug
Why would you expect none of the collapse to be at free fall?

During part of the collapse there could be lower structure failing. The steel could have been bending and got to the point where it was not offering resistance.

And there is going to be errors involved with accelation calculations. They have only so many frames.
Capracus
Fizical,

We have a thread in this forum full of dissected 9/11 assertions such as yours, so instead of beating a dead horse here, I suggest that you dive into this thread and see how long you can swim.
http://www.physforum.com/index.php?showtopic=12383
Fizical
QUOTE (RobDegraves+Sep 11 2009, 09:46 PM)
Here is a question to answer your question...


How many steel frame building were ever hit by 747's?


Edited to add...





okay, umm. double sigh...
So there are still zero examples of STEEL FRAMED buildings collapsing due to fires.

You kindly quote the explanation of what a concrete re-inforced building is made of whch clearly states 3 options, one of whic is concrete mixed with steel fibres (which the exmaple sited MAY have been?). While this obviously increases the strength of the concrete it dones't consititute a steel frame building.




How many steel frame building were ever hit by 747's?
Unless anything happened recently there have been 2 cases of 747's being flown in to buildings, both on 9/11. There was the famous case of the 707 (I think?) that flew in to the empire state building in the black and white tv days... which handled impact impecably.

I'm not sure where you're going with that

(Thanks I'll check th eother thread for some evidence proving the official story too)
RobDegraves
QUOTE
I'm not sure where you're going with that


Easy.

The Towers were not brought down by a fire... they were brought down by jets hitting them and thousands of gallons of fuel igniting... and a fire.
Fizical
QUOTE (RobDegraves+Sep 11 2009, 11:44 PM)

Easy.

The Towers were not brought down by a fire... they were brought down by jets hitting them and thousands of gallons of fuel igniting... and a fire.

sorry, yes - so the story goes.. I was merely pointing out my earlier claim about no other steel framed buildings colapsing due to fire has not been 'de-bunked' NIST report blames the fires, not damage caused by falling debris as the primary source of collapse, later staing it only has a "low probabilty" of actually being correct. not too confident ;o) perhaps they should have considered the internaly placed explosives hypothesis...

the fire balls were over in just a few minutes. I recall seeing someone standing in the ewing hole before on of the twin towers collapsed. (nearly where the alledged deforming of the steel stucture happed in the. fires. You'd need a sustained fire to increase the temps to the high levels required to buckle the steel sufficiently. (not present)
Yo'd also expect to see slow onset of deformation (not present) if the steel was gradually loosing it's rigidity.

You'd also expect to see deformation and collapse in line with the angled destruction from th eplane (again, not present) The collapse was unifrom accross the floors on all the video's you see.
RobDegraves
I have nearly no idea about what you are talking about because you can't seem to write legibly.

In addition you don't prove nearly any of the statements you make.

QUOTE
later staing it only has a "low probabilty" of actually being correct.


Link or quote would be nice.

QUOTE (->
QUOTE
later staing it only has a "low probabilty" of actually being correct.


Link or quote would be nice.

the fire balls were over in just a few minutes


Same

QUOTE
I recall seeing someone standing in the ewing hole before on of the twin towers collapsed.


What's an "ewing" hole?

Also.. what are you talking about?

QUOTE (->
QUOTE
I recall seeing someone standing in the ewing hole before on of the twin towers collapsed.


What's an "ewing" hole?

Also.. what are you talking about?

You'd need a sustained fire to increase the temps to the high levels required to buckle the steel sufficiently.


Link or proof would be nice.

QUOTE
(again, not present)


Same

QUOTE (->
QUOTE
(again, not present)


Same

Yo'd also expect to see slow onset of deformation (not present) if the steel was gradually loosing it's rigidity.


Same

QUOTE
You'd also expect to see deformation and collapse in line with the angled destruction from th eplane


Same.


Seriously... are you just repeating what other people say on conspiracy websites or do you have any kind of actual knowledge?

Honestly... it does not seem like you do.

buttershug
QUOTE (RobDegraves+Sep 11 2009, 11:44 PM)

Easy.

The Towers were not brought down by a fire... they were brought down by jets hitting them and thousands of gallons of fuel igniting... and a fire.

And gravity, don't forget gravity.

All the fire did was buckle the supports out of true vertical.
Fizical
QUOTE (RobDegraves+Sep 12 2009, 12:07 AM)

Seriously... are you just repeating what other people say on conspiracy websites or do you have any kind of actual knowledge?

Honestly... it does not seem like you do.

Okay fact fans, buckle your seat belts: [NOTE - this site doesnt not (currently) give me permission to post links - change the [DOT] for a real .

Admition of "low probability that fires cause the collapse of WTC7:
fema[DOT]gov/pdf/library/fema403_ch5.pdf
Last sentence before section 5.7 states "The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence. Further research, investigation, and analyses are needed to resolve this issue. "

then Section 5.7 at the end of the 3rd para "Although tth total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence"

Fireballs in WTC 1 and 2 were out in just a few minutes - a) watctgh any footage! cool.gif ask Jeff King (MIT Engineer) c) the offical investigation by FEMA d) the north tower collapsed less that an hour after planes impact (MIUNTES) e) f) g) h) i) and more see 911research[DOT]wtc7.net/wtc/analysis/fires/severity.html

next -
there was an extra e in my typing, sorry - a typo should have read:
I recall seeing someone standing in the wing hole before on of the twin towers collapsed. The inference being that a human can live just a few feet away from where the alleged hot fires that bent the steel were.

You'd need a sustained fire to increase the temps to the high levels required to buckle the steel sufficiently. [in WTC 1 and 2] For the steel to have buckled, and collapsed due to heat there must be a heat source. this heat sources must be sustained in order to reach the desired temperatures (the exat temp hotly debated) but the bottom line is that the initial fires went out fast, black smoke indicates a fire without enough oxygen to burn efficiently. there was not a sustained high heat present, therfore it is unlikely to be the cause of the collapse.

neeeeeeeeeeext
You'd also expect to see slow onset of deformation (not present) if the steel was gradually loosing it's rigidity.
Steel bends and buckles as it looses rigidity, as it softens due to heat. Should I put a link in to your school books here?

Next pleeeeeeease
You'd also expect to see deformation and collapse in line with the angled destruction from th eplane [and subsequent fires]
Correct - I thought this was the physics forum, not the magic circle?!?!!? the planes collision clearly made some structural damage tot he buildings. this damage was not uniforms accross the floors as you see in the video evidence - showing perfectly uniform explosive forces outwards around the whole building (not just one area or side)


It seems like I'm repeating what other people are saying? Have you considered you would hear the same information becuase it is true? I am no doubt repeating what others have also researched and concluded, becuase I have followed some course of logic on the same scenario.
Capracus
QUOTE (Fizical+Sep 12 2009, 09:02 AM)
Okay fact fans, buckle your seat belts: [NOTE - this site doesnt not (currently) give me permission to post links - change the [DOT] for a real .

Admition of "low probability that fires cause the collapse of WTC7:
fema[DOT]gov/pdf/library/fema403_ch5.pdf
Last sentence before section 5.7 states "The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence. Further research, investigation, and analyses are needed to resolve this issue. "

then Section 5.7 at the end of the 3rd para "Although tth total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence"

Fizical,

Go the to Physics Of 9/11 Events - Part 3, continued from: 9/11 Events- New thread for my response to your questions. Here is the link.
http://www.physforum.com/index.php?showtop...ndpost&p=428568
Fizical
Your post in the link quotes that all scenarios were explored....

ALL SCENRIOS's were NOT addressed, particularly mutilpe explsive devices.

From the link you posted on NIST's final report:

"Attention focused on a single hypothetical blast scenario explosive location. This involved preliminary cutting of Column 79 and the use of 4kg (9lb) of RDX explosives in linear shaped charges. The other scenarios would have required more explosives, or were considered infeasible to carry out without detection."

The key failure in this report is that don't even investigate the possibility of multiple explovies because it's "unfeasable" i.e. They are dismissing it immediately based on the assumtion that a conspiracy is not possible.

That is not scientific, that is a cover up.

[Moderator: Suspended 7 days to free poster from all but his scientific duty (see below). ]
rpenner
That's not a scientific rebuttal -- you have to provide a model where such a conspiracy is feasible.


Waiting. Here -- I'll help. You are suspended one week during which you can compose your model of a conspiracy theory in detail and have it ready for posting when the ban lifts. Of course, if you fail in this, then you will be assumed to be full of crap whenever you talk about conspiracies OR science.
buttershug
And I think no 9/11 conspiracy theory is complete without an exlaination as to why they did not find WMD in Iraq. That ended up being more important to any overall plan. And would have been easy in comparison.
H2O
RobDegraves

I like the article you quoted about various fires in multistory building. However a careful read yields something they all have in common.

Progressive, non-uniform and partial collapse.

The biggest issue that "truthers" have is that the WTC did not have these very common and expected characteristics.

The collapse was very sudden. Or else rescuers would have not been completely caught by surprise and would have pulled out.

The collapse was uniform as any video clearly shows

Collapse was total as any video and pic once again clearly shows.

Sorry but before hairs are split, a half second difference between one corner going and another corner does not count as non-uniform. As any video of an actual demolition will show there will be small but existing delays.

"Now the other building didn't get hit by planes".

Very true but...

Do you think the floors would be weakest at point of impact?
Do you think the floors would be weakest where the fires burned the longest?

Where the planes hit would be your weakest point. It's where the damage was done by impact. It's where the fires started. Then how is it tower 2 didn't topple over? Only that corner of the building was struck and would have received the most damage. It also would have had fires burning there the longest. Then those floors at that location would have collapse. With that corner collapsing the tower (provided the core couldn't make up the lack of support) would have buckled there and toppled over.
PhysOrg scientific forums are totally dedicated to science, physics, and technology. Besides topical forums such as nanotechnology, quantum physics, silicon and III-V technology, applied physics, materials, space and others, you can also join our news and publications discussions. We also provide an off-topic forum category. If you need specific help on a scientific problem or have a question related to physics or technology, visit the PhysOrg Forums. Here you’ll find experts from various fields online every day.
To quit out of "lo-fi" mode and return to the regular forums, please click here.