WTC: Rate of Fall (rate of crush)

[Ron J]

Fantasy. These contortions are equal to the 'building within a building' stuff. The guy made an effort to actually do the maths - and the maths is right, no matter your protestations, if not a perfect representation. He doesn't claim perfection. But basically it's correct - and you know it. Don't you? How long should the building have taken to reach the ground? - let's see your maths in his terms and based on my calculation of the total weight of one tower which is 280,000 tonnes including furniture. If what we're told is true, then how long for 'The Crusher' (ie. the top 15 floors - which actually weighed about 38,000 tonnes) to hit the ground after crushing the building and then itself, leaving nothing recognizable as a building, and likewise its contents (yes, that's the story, I feel sullied just repeating it). Can we see that from you in the terms I propose?

How long should the building have taken to reach the ground? The amount of time that it did.

15 floors crushing the building, then itself. One has to assume that the top 15 floors fell all the way to the ground as a unit, instead of breaking up just as the floors below broke up in its initial wake. Smoke and pulverized debris obscured any observation of the top 15 floors after a certain point. People survived in stairwell A on the lowest floors. Would that have been the case if the top 15 floors had crashed into the lobby as one unit?

The TV antenna was wobbling as the top 15 floors began to fall. How long did the roof remain intact?

Debris was shooting out windows on floors before column sections fell away in video i have seen of the South Tower. Internal collapse was leading external collapse, regardless that the top 30 floors collapsed down onto the the remaining 80. Obviously we are talking about the North Tower here, but i think the dynamics are more complicated than some math formula would suggest.

I saw a Youtube video accompanied with some physics experiments, which the author claimed that the only way that the top 15 floors could have fallen into the rest of the building in the manner it did, was if the support below was blown out. The problem with that being no evidence of explosions to blow out support at the 94th? floor.

Critics have decried that the collapse of the Towers defied the laws of physics, but no laws of physics could have been broken.

How long it took the top 38,000 tons to reach the ground depends on which pieces of the 38,000 tons one is talking about. Some column sections of the top 15 floors may have hit the ground before column sections at the 20th floor did.

[Jazzy]

I saw a Youtube video accompanied with some physics experiments, which the author claimed that the only way that the top 15 floors could have fallen into the rest of the building in the manner it did, was if the support below was blown out. The problem with that being no evidence of explosions to blow out support at the 94th? floor.

That is only because no truther appears to understand buckling instability. It doesn't feature as part of their vocabulary.

http://en.wikipedia.org/wiki/Structu...heory#Buckling

Read it. In twelve years no truther, even the ones that call themselves engineers, has discovered it. They haven't done so because it immediately answers the question of how can something begin silently and progress towards a downward acceleration approaching G. Had they found it they would have forgotten it, because they would have received an unwelcome answer.

A careful balance between ignorance and dishonesty has to be maintained...

There are some wonderful YouTube college structural engineering videos on slender column buckling instability. I recommend them.

[Oxymoron]

That is only because no truther appears to understand buckling instability. It doesn't feature as part of their vocabulary.

http://en.wikipedia.org/wiki/Structu...heory#Buckling

Read it. In twelve years no truther, even the ones that call themselves engineers, has discovered it. They haven't done so because it immediately answers the question of how can something begin silently and progress towards a downward acceleration approaching G. Had they found it they would have forgotten it, because they would have received an unwelcome answer.

A careful balance between ignorance and dishonesty has to be maintained...

There are some wonderful YouTube college structural engineering videos on slender column buckling instability. I recommend them.

Strange assertion to make that the general public are unaware of buckling... everyone I know is well aware of the process. To suggest that 'truther' engineers do not know and understand it seems highly improbable to say the least, as they would have to factor it in their day to day work.

Further, it is well known that buckling is very often a precurser to shearing/fracture and collapse.

It seems far more likely that your assertion is dishonest Jazzy. It also fails to take into account many documented instances where buckling leads to shearing which leads to sections falling off whilst leaving the main structure standing.... especially if the buckling and shearing are asymmetric as was the case in question. But it appears you wouldn't really want to go there because that would contradict your argument would it not? Careful balances must be maintained eh

[Jazzy]

Strange assertion to make that the general public are unaware of buckling... everyone I know is well aware of the process.

So why is it called instability? No peeking.

To suggest that 'truther' engineers do not know and understand it seems highly improbable to say the least, as they would have to factor it in their day to day work.

They never mention it. The NIST Report does.

Further, it is well known that buckling is very often a precurser to shearing/fracture and collapse.

No. It is a precursor only to collapse.

many documented instances where buckling leads to shearing

Name one.

which leads to

Gibberish from then on. No surprise there.

This is why all the buildings fell:



As soon as floors detached (and in all cases they were observed detaching) the columns, though strong enough to withstand their vertical loads, were no longer stable.

This is a complete answer to the observed silent initial stage of all three collapses, and the observed downward acceleration of close to G.

It is a complete answer, without ifs, buts and maybes.

Here it is before your eyes.

[Oxymoron]

So why is it called instability? No peeking.

Ok, no peeking... Because something which has buckled is unstable and likely to collapse. It is one of the factors which is taken into account in determining the effects of stresses and strains on structures to ensure their fitness for use and safety.

They never mention it. The NIST Report does.

I agree it is under mentioned. It appears to me surprising that the top section which broke loose did not continue, (it started), in it's lateral movement which would have led to it detatching and falling on it's own, (obviously with more damage incurred on the side which it fell toward.

No. It is a precursor only to collapse.

Around 4 mins is the most interesting and demonstrative part

[Jazzy]

Ok, no peeking... Because something which has buckled is unstable and likely to collapse.

NO.

A vertical slender column which buckles IS collapsing. The only thing to follow it is its meeting ground zero.

It is one of the factors which is taken into account in determining the effects of stresses and strains on structures to ensure their fitness for use and safety.

NO.

Each vertical slender column is normally ten times more capable of resisting buckling instability within its position in the structure than it need be.

It is when the structure is compromised that an erstwhile perfectly strong column fails.

I agree it is under mentioned.

Hah.

It appears to me surprising that the top section which broke loose did not continue

It never fully broke loose of either its inner or outer columns.

Once impacting random pieces of the lower structure there was no way it could maintain its own cohesion, which faded to nothing within seconds.

NONE of the videos you offer here are relevant to compression loads on a slender vertical column. You immediately reveal your er, weakness in this department.



Notice that L, the effective column length, is underneath and squared. Lose a floor, a quarter as stable, lose two floors, a ninth as stable, three floors, a sixteenth as stable, and thar she blows...

Hardly any of the internal and external columns were in any way crushed or damaged. They lost their lateral connections and became too unstable to remain erect.

The buckling of slender columns is a process which needn't damage the column in any way.

Check the the second case model in my previous post: the structure failed without damaging the columns. With a wriggle.

Do you have a steel measuring tape at home? That fails by buckling all the time without damage. Think about it.

[Oxymoron]

NO.

A vertical slender column which buckles IS collapsing. The only thing to follow it is its meeting ground zero.

Check the the second case model in my previous post: the structure failed without damaging the columns. With a wriggle.

Do you have a steel measuring tape at home? That fails by buckling all the time without damage. Think about it.

It is not hard Jazzy, 'buckling' is 'bending'... girders can buckle without collapsing, I have seen it many times. If the forces stabilise or decrease the beam will simply remain buckled or 'bent' as below. If the forces increase the buckle will continue to a point where connections sheer or the weight drags it over.



As for your yt example (face palm).

Are you suggesting the floors dropped in 1 and 2, the same way as is alleged in 7, (internally and unseen leaving a facade to collapse straight down)?

Also, you did notice when the tinsy little model 'collapses', (around 1.30)... it tips over!

[Cairenn]

But NONE of the facades collapsed 'straight down'. I have to wonder why you keep insisting they did.

[Jazzy]

It is not hard Jazzy, 'buckling' is 'bending'

No, it [...] isn't.

Content from external source:

Buckling
In science, buckling is a mathematical instability, leading to a failure mode. Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium. At a certain stage under an increasing load, further load is able to be sustained in one of two states of equilibrium: an undeformed state or a laterally-deformed state.
In practice, buckling is characterized by a sudden failure of a structural member subjected to high compressive stress, where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding. For example, during earthquakes, reinforced concrete members may experience lateral deformation of the longitudinal reinforcing bars. This mode of failure is also described as failure due to elastic instability. Mathematical analysis of buckling makes use of an axial load eccentricity that introduces a moment, which does not form part of the primary forces to which the member is subjected. When load is constantly being applied on a member, such as column, it will ultimately become large enough to cause the member to become unstable. Further load will cause significant and somewhat unpredictable deformations, possibly leading to complete loss of load-carrying capacity. The member is said to have buckled, to have deformed.

http://en.wikipedia.org/wiki/Buckling

Content from external source:

The most significant mathematician of all time, Leonhard Euler was born in Basel in 1707. He contributed to areas of both pure and applied mathematics, including calculus, analysis, number theory, topology, algebra, geometry, trigonometry, analytical mechanics, hydrodynamics, and the theory of the moon’s motion.
By means of his numerous books and memoirs that he submitted to the academy, Euler carried integral calculus to a higher degree of perfection, developed the theory of trigonometric and logarithmic functions, reduced analytical operations to a greater simplicity, and threw new light on nearly all parts of pure mathematics. Overtaxing himself, Euler in 1735 lost the sight of one eye. Then, invited by Frederick the Great in 1741, he became a member of the Berlin Academy, where for 25 years he produced a steady stream of publications, many of which he contributed to the St. Petersburg Academy, which granted him a pension. In 1748, in his Introductio in analysin infinitorum, he developed the concept of function in mathematical analysis, through which variables are related to each other and in which he advanced the use of infinitesimals and infinite quantities. He did for modern analytic geometry and trigonometry what the Elements of Euclid had done for ancient geometry, and the resulting tendency to render mathematics and physics in arithmetical terms has continued ever since. He is known for familiar results in elementary geometry; for example, the Euler line through the orthocentre (the intersection of the altitudes in a triangle), the circumcentre (the centre of the circumscribed circle of a triangle), and the barycentre (the “centre of gravity,” or centroid) of a triangle. He was responsible for treating trigonometric functions--i.e., the relationship of an angle to two sides of a triangle--as numerical ratios rather than as lengths of geometric lines and for relating them, through the so-called Euler identity (eix = cos x + i sin x) , with complex numbers (e.g., 1 + −1 ). He discovered the imaginary logarithms of negative numbers and showed that each complex number has an infinite number of logarithms.

http://maji.utsi.edu/courses/02_flui...y_01_euler.pdf

the beam

The COLUMN.

As for your yt example (face palm), are you suggesting the floors dropped in 1 and 2, the same way as is alleged in 7, (internally and unseen leaving a facade to collapse straight down)?

Except that the collapse wasn't "straight down", yes. And there are pictures of dropped floors (immediately before collapse) in the NIST Report. Have you read it yet?

Also, you did notice when the tinsy little model 'collapses', (around 1.30)... it tips over!

That WAS the buckling. Didn't WTC 2 "tip over"?

[...]

[Oxymoron]

No, it [...] isn't.

Yes, it [...] is.

Content from external source:

Buckling
In science, buckling is a mathematical instability, leading to a failure mode. Theoretically, buckling is caused by a bifurcation in the solution to the equations of static equilibrium. At a certain stage under an increasing load, further load is able to be sustained in one of two states of equilibrium: an undeformed state or a laterally-deformed state.
In practice, buckling is characterized by a sudden failure of a structural member subjected to high compressive stress, where the actual compressive stress at the point of failure is less than the ultimate compressive stresses that the material is capable of withstanding. For example, during earthquakes, reinforced concrete members may experience lateral deformation of the longitudinal reinforcing bars. This mode of failure is also described as failure due to elastic instability. Mathematical analysis of buckling makes use of an axial load eccentricity that introduces a moment, which does not form part of the primary forces to which the member is subjected. When load is constantly being applied on a member, such as column, it will ultimately become large enough to cause the member to become unstable. Further load will cause significant and somewhat unpredictable deformations, possibly leading to complete loss of load-carrying capacity. The member is said to have buckled, to have deformed.

http://en.wikipedia.org/wiki/Buckling[...]

Leading to failure mode or to have deformed. Things do buckle (get bent) without collapsing although more often than not they do collapse but the collapse may be immediate and spectacular or it may collapse quite some time after, gradually, or not at all.

http://publish.ucc.ie/boolean/2010/00/dePaor/11/en



This is buckled, (bent). It is all a question of degree. A beam can bend and then spring back.... or it can bend and remain bent, (buckled) or it can bend too far, leading to a catastrophic failure. Yes if a beam or something is bent, then obviously it is (in a structural sense) unfit for service and will need replacing but things DO buckle without catastrophic collapse... just to clear up the bunk.

Except that the collapse wasn't "straight down", yes. And there are pictures of dropped floors (immediately before collapse) in the NIST Report. Have you read it yet?

As for the buildings not 'coming straight down'... to most normal people that is exactly what they did. If you want to faff around some convoluted argument that they didn't... be my guest. Perhaps you may like to start a thread on how they didn't comee down straight and ridicule the ignorance of 99% of the worlds population?

That WAS the buckling. Didn't WTC 2 "tip over"?

The top of wtc 2 could have been a partial collapse, (as it was part of the whole), To many people it looked as if it should have carried on sliding until it fell off the main body but instead of a partial collapse it very quickly changed to a total collapse.

Anyway you must obviously be a far better engineer than Astineh, who was admittedly shocked that the towers collapsed; but you have oft stated that 'you knew straight way as soon as the planes hit, that the towers were coming down', which is pretty amazing really when you consider it had never happened before or since.

[tjohnson_nb]

There is no way in hell the WTC buildings collapsed - these structures were severely compromised somehow. Maybe someday we will know how and by whom. At this point I don't even believe they were hit by airplanes. The video makes no sense.

[Cairenn]

Thousands of folks SAW the planes fly into them. There were cameras running when the second plane hit. HOW in blazes can you say that they weren't hit by planes?

I will ask you, Are you a structural engineer? A materials engineer? Or someone that has a lot of experience working with steel or iron, when it is hot?

My hubby was home that day, since I had day surgery. We had already discussed if they could survive. He is geophysical engineer, by area is physics/geology. Neither of us have a structural background, and we had no information about how they were built. In spite of that, we had discussed what might happen if the damage was so intense that the top collapsed. Our guess was a total collapse.

[Jazzy]

Things do buckle (get bent) without collapsing

Vertically-loaded slender columns FAIL. They fail due to elastic instability. It still doesn't feature in your discussion. Because you don't know what you are talking about.

As for the buildings not 'coming straight down'

How was WTC 7 hit?

The top of wtc 2 could have been a partial collapse

It was already out of line. The civil engineering calculations rely on such buildings being horizontal and vertical. Even lined up, there was too much momentum in the falling structure for the intact structure beneath not to be crushed.

To many people it looked as if it should have carried on sliding until it fell off the main body

At that angle it would fail immediately as soon as it reacted with anything stationary. It could only hold its shape in near free fall.

you have oft stated that 'you knew straight way as soon as the planes hit, that the towers were coming down', which is pretty amazing really when you consider it had never happened before or since.

I knew how thin those floors were, and how important that their underside be insulated. I also knew the thermobaric effects consequent to vaporizing ten tons of kerosine, and mixing it with air, and igniting it. I knew it would blow off the foam, blast down the partitions and reach both to the roof and the basement via the lift shafts.

That is because I'm an aeroengineer, and have been for a long time. I enjoy seeing everything via science, thanks. What's your discipline? Obviously NOT science...

[Oxymoron]

Example of Buckling... I trust this will be an end to the argument that 'Buckling' is : "A vertical slender column which buckles IS collapsing. The only thing to follow it is its meeting ground zero."

As can clearly be seen, no collapse happened here and it certainly did NOT meet ground zero.

If we cannot trust the Cardington fire research project to use the correct terminology, who can we trust?
http://911research.wtc7.net/mirrors/...2/fire/SCI.htm

Content from external source:

Buckling occurred in the proximity of some of the beam-to-column connections but unlike Test 2, bolts in the connections did not suffer shear failure. This might indicate either that the high tensile forces did not develop or that the connection had adequate ductility to cope with the tensile displacements.

[Jazzy]

Example of Buckling

You are pointing out the buckling of a beam.

I have always been talking about the buckling, by elastic instability, of a slender vertical column.

Kindly desist from your persistent straw man argument.

I have pointed to you many times now the research conducted by Leonhard Euler in the mid-eighteenth century into slender vertical column elastic instability. Please read it and attempt to understand it.

For the nth time, the stability in question is demonstrated by this video:



Until you understand what has happened here, you are going to continue to permit yourself your fallacies.

You seem to be stuck. I no longer care.

[Oxymoron]

You are pointing out the buckling of a beam.

I have always been talking about the buckling, by elastic instability, of a slender vertical column.

Kindly desist from your persistent straw man argument.

I have pointed to you many times now the research conducted by Leonhard Euler in the mid-eighteenth century into slender vertical column elastic instability. Please read it and attempt to understand it.

For the nth time, the stability in question is demonstrated by this video:



Until you understand what has happened here, you are going to continue to permit yourself your fallacies.

You seem to be stuck. I no longer care.

Except it is not 4 flimsy columns that we are talking about is it?

Nor did the towers rotate around, tip over, release the load and then spring back again. They collapsed straight down....The video is garbage. It is not even clear what the '4 columns' in the video are made of! Rubber? Slinky 'spring' (high tensile) Steel? Certainly not your commonal garden steel as used in columns and beams.

Is that not fraudulent? Gross Misrepresentation? Bunk?

Slinky was originally priced at $1, but many paid much more due to price increases of spring steel



Not only that, they didn't even really 'buckle' in the true sense because a buckled steel column does not spring back after such massive deformation.

We are talking about very many columns all needing to buckle together and a huge structural core, (which dwarfed the Eiffel Tower AND remained after the collapse until it mysteriously 'disappeared' in a puff of smoke)

More like this, I suggest.



Again... Buckled but no total collapse. What does Euler say about this?



Or this?



Apples and oranges are not even in the same universe!

[Jazzy]

Except < bullshit > universe!

I am not going to repeat myself.

[Oxymoron]

Re the Windsor Madrid Fire and partial collapse of unprotected, (no fire protection applied (SFRM)), lightweight steel mullions, (load bearing columns)

See http://metabunk.org/threads/1552-WTC...ll=1#post43044

http://www.newsteelconstruction.com/...adrid/?print=1

Content from external source:

A view has previously been expressed that the collapses were caused by failure of perimeter steel mullion columns which were directly exposed to fire and this has been contrasted unfavourably with the perception that the concrete structure performed extraordinarily well.

Now that a report has been published by the Spanish authorities(1) it is possible to see that the situation is not as simple as the view expressed above. This article reviews some the information contained in this report and develops one important hypothesis.
First it must be made absolutely clear that the steel mullion columns should have had applied fire protection. Reference to BS 5950-8(2) or the Eurocodes would confirm this as they were relatively light load bearing multi-storey columns with high section factors (A/V between 100 and 200 m^-¹).

In the course of refurbishment, fire protection had already been applied to these mullion columns on all levels below the 17th with the exception of the 9th. None of the fire protected mullions failed and the Spanish report concludes that, although it cannot be stated with absolute certainty, the collapse of the upper storeys would not have occurred had this fire protection already been in place throughout.

That is the end of the report’s specific conclusions about the contribution of the steel mullions to the collapse. If you do not protect light steel members they will fail in a prolonged fire. Hardly rocket science!

However, it is interesting to see what happened on the 9th level. The picture shows that the unprotected steel mullions buckled as they were restrained against thermal expansion. But collapse did not ensue. Why? The answer is that the loads were taken by multiple alternative load paths – a classic robustness provision. Mullions above from level 10 to 17 and below from level 8 down were able to distribute and share the loads as the 9th level mullions failed. The fact that there were 60 mullions per floor level added to the number of alternative load paths available.




Why was it that although these alternative load paths existed above the 17th level they did not apparently prevent the collapses?

There are two answers to this – firstly because there was no effective fire compartmentation of the building; secondly because of the failure of two internal concrete columns. Yes, a portalised pair of 1200 x 500 concrete columns did collapse.



Buckling of 9th floor mullions...(NB note buckled light steel mullions in background)

Dr Roger Pope analyses the Spanish report into the causes of the Windsor building fire in Madrid. Unprotected steel mullions were not the sole cause of the collapse, he suggests.

On 12 February 2005, fire broke out in the 30 storey Windsor Building in Madrid.

The fire started on the 21st floor level. As shown in the picture taken from the east after the fire, the serviced storey between 16th and 17th levels arrested all the progressive collapse that occurred to the upper superstructure. Such “strong floors” in multi-storey buildings are another classic robustness provision.

NB.. Classic means, old, well known, tried and tested. And yes The WTC's had them.

This is a simple but effective demonstration of the effect of alternate load pathways.



It would be interesting if someone could work out the likely critical forces available from the 20 odd floors which collapsed onto the structurally sound floors below, (taking into account the large amount of debris overspill) and compare that with the combined resistance of the structure below, (taking into account alternate load pathways and bearing in mind the preference for pathways of least resistance, (being overspill to the sides).

[Jazzy]

Re the Windsor Madrid Fire and partial

no, Oxy, complete

collapse of unprotected lightweight steel mullions

the effect of alternate load pathways

Can be completely overcome by creep.

By settling due to heat-induced creep, columns can transfer their loads via interconnected truss structures.

In the case of WTC 2, the transferred loads appeared to help cause the external face buckle (once floors dropped away) in the direction of lean, whereas with WTC 1 it appeared that the internal columns failed first.

In both cases, creep loads were transferred by the towers' top hat trusses.

Content from external source:

In materials science, creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. It occurs as a result of long-term exposure to high levels of stress that are below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and near their melting point. Creep always increases with temperature.
The rate of this deformation is a function of the material properties, exposure time, exposure temperature and the applied structural load. Depending on the magnitude of the applied stress and its duration, the deformation may become so large that a component can no longer perform its function — for example creep of a turbine blade will cause the blade to contact the casing, resulting in the failure of the blade. Creep is usually of concern to engineers and metallurgists when evaluating components that operate under high stresses or high temperatures. Creep is a deformation mechanism that may or may not constitute a failure mode. Moderate creep in concrete is sometimes welcomed because it relieves tensile stresses that might otherwise lead to cracking.

http://en.wikipedia.org/wiki/Creep_(deformation)

You must be seriously invested in your pseudoscience, Oxy, to so permanently set your face against the truth. You have my sympathy. So has my old, blind, deaf dog. But she smells, too.

[Ron J]

There is no way in hell the WTC buildings collapsed - these structures were severely compromised somehow. Maybe someday we will know how and by whom. At this point I don't even believe they were hit by airplanes. The video makes no sense.

If there was no way that the WTC buildings collapsed, they would still be standing. The structures were severely compromised by the planes that flew into them and the fires that ensued. You should view video of the bowed in columns on the east wall of WTC2 where the fire was burning. It might give you an understanding of why a fire compromised building would collapse.

There are numerous videos of the second jetliner crashing into WTC2 and a French documentarian shot video of the the jetliner striking WTC1, while recording a documentary on an NYFD fire house. That the Towers were struck by jetliners was well documented.

[Ron J]

The top of wtc 2 could have been a partial collapse, (as it was part of the whole), To many people it looked as if it should have carried on sliding until it fell off the main body but instead of a partial collapse it very quickly changed to a total collapse.

The collapse of WTC2 was a total collapse from the start. Once it began, there was no stopping it. It never could have been a partial collapse, as floors began collapsing below the break immediately after the break occurred. Debris burst out windows just below the break moments after the east wall failed. Debris was bursting out those lower windows as floor trusses fell down to those floors, then causing more floor trusses to collapse in chain reaction.

The top 30 floors could not simply slide off or tip over off the rest of the building, leaving it unscathed.

[hiper]

Ron J you talk about the floors and conveniently leave out the massive steel core that somehow disintegrated along with the floors.
Not very credible.
What do you think was the reason for the disintegration of the steel core?

[Mick]

Ron J you talk about the floors and conveniently leave out the massive steel core that somehow disintegrated along with the floors.
Not very credible.
What do you think was the reason for the disintegration of the steel core?

When it no longer had the lateral support of the floors it collapsed from the thousands of tons of steel and concrete falling on it. Even when nothing was falling on it, with enough lateral support removed it could not be stable under its own weight. In the image below half the height of the core is still standing.

Buckling is the key here.