If "partial collapse" is POSSIBLE why is "complete collapse" IMPOSSIBLE?

[1337m4n]

If "partial collapse" is POSSIBLE why is "complete collapse" IMPOSSIBLE?

From my other thread:

Collapse zones around high rise fires are standard. They are not put in place in case the building implodes, they are created in case of partial collapses or things falling off the building.

These zones happen in all high rise fires.

Truthers seem to acknowledge that it is fully reasonable for buildings to experience "partial collapses" due to fire. They even acknowledge this with regards to the Windsor building:

This building experienced a "partial collapse" due to nothing more than a really hot fire.

So logically one would assume that the WTC collapses are perfectly reasonable, right?

Not to the Truthers. According to them, the fact that Windsor only suffered "partial collapse" while WTC suffered "complete collapse" is somehow a critical distinction.





Anyone? Does this make sense to you? Anyone at all? Can someone explain to me how this is supposed to make sense?

If fire can destroy PART of a building why can it not destroy ALL of a building?

 

[Unfit4Command]

According to Truther logic, the Windsor Tower was partially demolished by explosives because I don't see all of the floor assemblies (aside from a few portions still attached to the concrete core) in a neat stack anywhere. The only explanation for this is explosives pulverizing them.

 

[Sizzler]

Let me try to explain from a laymen's point of view.

In the Windsor building the core remained. Now I know the core of the WTC and the Windsor are very different. One was enclosed in concrete and the other was not, and quite probably had some of its fireproofing removed.

On that note;

I can easily imagine the horizontal floor structure at initiation point falling at free-fall to hit the next floor below it. However, I find it difficult to imagine that the vertical core also fell the length of one floor at near-freefall to hit the next floor below it. Fire ultimetely caused the core to fail, but how would that account for the near-freefall decent?

This summarizes exactly what I am trying to express;

The fire has to heat the steel, which takes time. Eventually the steel gets hot enough that it cannot carry the load in the initiating storey. It starts to sag. At this point there has been no disruption of the columns, other than that caused by the plane impact, hence most of the columns are still attached to the floors above and below and are continuous, passing up and down into other storeys, giving the columns rigidity. The length of the columns between attachments is too short for buckling to occur. 8 Failure must therefore be by compression.

As the steel sags two things will happen: the columns, as they shorten, will become wider, which is obvious; and the inherent strength of the steel will increase, which is not obvious. It is well established however that the yield strength of steel increases as the degree of distortion increases. This tendency increases with rising temperature and is pronounced at the temperatures required for collapse, as can be seen in the graph below. 9 For both of these reasons the initial sag cannot be catastrophic but will be very slow and the rate will depend on the rate of heat input. A rising temperature will be needed to offset both the significant increase in yield strength and the slight increase in cross-section area, if collapse is to progress.

It is clear therefore that the upper section should only have moved down slowly and only continued to do so if additional heat was supplied. A slow, protracted, and sagging collapse was not observed however with either tower. As observed in videos of both tower collapses, the upper sections suddenly start to fall and disintegrate.10 In the case of the south tower, initially a lean of the upper section developed but within the first second this turned into a rapid collapse with upper section disintegration, just as was observed with the north tower.

http://www.journalof911studies.com/volume/200703/Sudden_collapse_initiation_impossible.pdf

The above seems intuitive to me while the sudden failure of the core and near free-fall decent seems counter-intuitive.

 

[R.Mackey]

As the steel sags two things will happen: the columns, as they shorten, will become wider, which is obvious; and the inherent strength of the steel will increase, which is not obvious. It is well established however that the yield strength of steel increases as the degree of distortion increases. This tendency increases with rising temperature and is pronounced at the temperatures required for collapse, as can be seen in the graph below. 9 For both of these reasons the initial sag cannot be catastrophic but will be very slow and the rate will depend on the rate of heat input. A rising temperature will be needed to offset both the significant increase in yield strength and the slight increase in cross-section area, if collapse is to progress.

This is 100% crap, that's why.

Most of the failure will be buckling or fracture, not sheer compression. And I have never in my life heard anything so retarded as "the column gets stronger as it sags." Even assuming the columns are failing in compression -- which implies a very stout and well-pinned column -- the fact that it's sagging means it's gone plastic, and it has very, very little material strength left.

Do yourself a favor and don't go anywhere near a structure built by this moron.

ETA: Ah, this is the Legge/Szamboti paper. We've commented on it before. He's talking about strain hardening, and there is a slight increase in Young's modulus as strain approaches critical, but that is NOT where you want your structure to be. This also happens at a few percent strain (0.5%? memory fails), not nearly enough to give you a graceful, gentle flow down to the next floor...

 

[1337m4n]

Let me try to explain from a laymen's point of view.

In the Windsor building the core remained. Now I know the core of the WTC and the Windsor are very different. One was enclosed in concrete and the other was not, and quite probably had some of its fireproofing removed.

On that note;

I can easily imagine the horizontal floor structure at initiation point falling at free-fall to hit the next floor below it. However, I find it difficult to imagine that the vertical core also fell the length of one floor at near-freefall to hit the next floor below it. Fire ultimetely caused the core to fail, but how would that account for the near-freefall decent?

This summarizes exactly what I am trying to express;


http://www.journalof911studies.com/volume/200703/Sudden_collapse_initiation_impossible.pdf

The above seems intuitive to me while the sudden failure of the core and near free-fall decent seems counter-intuitive.

But Sizzler, the "near freefall" claim is just a silly lie the Truth Movement made up (to borrow pomeroo's rhetoric).

How about you stop repeating lies and answer the question. The claim is that "complete collapse" due to fire is unexpected, unprecedented, implausible, etc. And the question regarding that is:

If fire can destroy PART of a building why can it not destroy ALL of a building?

 

[Sizzler]

But Sizzler, the "near freefall" claim is just a silly lie the Truth Movement made up (to borrow pomeroo's rhetoric).

How about you stop repeating lies and answer the question. The claim is that "complete collapse" due to fire is unexpected, unprecedented, implausible, etc. And the question regarding that is:

If fire can destroy PART of a building why can it not destroy ALL of a building?

But collapse initiation is observed to decend at near free-fall. Collapse initiation was sudden.

Dr. Greening has even pointed this out in some of his recent posts.

 

[Sizzler]

Apollo wrote:

Then, for an effectively constant accelerating force, and a tower roof line starting from rest:

9.6 = 1/2 acc (1.4)^2,

or acc = 9.8 m/s^2.

In other words, the collapse started at free fall!

This is a very important, if unexpected, result and I thank NIST for it......

Some said this is not unexpected. But to me, it seems counter-intuitive for the reasons I posted in my first post.

 

[Sizzler]

This is 100% crap, that's why.

Most of the failure will be buckling or fracture, not sheer compression. And I have never in my life heard anything so retarded as "the column gets stronger as it sags." Even assuming the columns are failing in compression -- which implies a very stout and well-pinned column -- the fact that it's sagging means it's gone plastic, and it has very, very little material strength left.

Do yourself a favor and don't go anywhere near a structure built by this moron.

ETA: Ah, this is the Legge/Szamboti paper. We've commented on it before. He's talking about strain hardening, and there is a slight increase in Young's modulus as strain approaches critical, but that is NOT where you want your structure to be. This also happens at a few percent strain (0.5%? memory fails), not nearly enough to give you a graceful, gentle flow down to the next floor...

Mackey; as a laymen, the sudden failure of the core seems counter-intuitive to me. How fire can cause a sudden failure of 47 vertical core columns is something I will never understand.

Humour me here for a second (stundie this if you want )

Imagine I took 47 dry spaghetti strands and stood them up vertically. Now I apply pressure on the top with my hand. Then I spray hot steam on one section of the 47 dry strands. Eventually the strands will lose strength but certainly not suddenly. It will be gradual, not sudden.

As laymen, I cannot, for the life of me understand the sudden failure of the core......

 

[einsteen]

Your picture shows it, a partial (local) collapse was possible but complete collapse was not possible!

 

[Architect]

Mackey; as a laymen, the sudden failure of the core seems counter-intuitive to me. How fire can cause a sudden failure of 47 vertical core columns is something I will never understand.

Humour me here for a second (stundie this if you want )

Imagine I took 47 dry spaghetti strands and stood them up vertically. Now I apply pressure on the top with my hand. Then I spray hot steam on one section of the 47 dry strands. Eventually the strands will lose strength but certainly not suddenly. It will be gradual, not sudden.

As laymen, I cannot, for the life of me understand the sudden failure of the core......

[sigh]

The core is not designed to act as a free standing structure. It relies upon the bracing effect of the floors to stiffen the overall composite structure. In the absence of floors, the core becomes unstable and fails.

 

[Dave Rogers]

In the Windsor building the core remained. Now I know the core of the WTC and the Windsor are very different. One was enclosed in concrete and the other was not, and quite probably had some of its fireproofing removed.

They're very much more different than that. The core of the Windsor wasn't enclosed in concrete, it was made of concrete. Concrete doesn't lose compressive strength in a fire the same way steel does. That's the crucial difference, and the Windsor shows it very clearly; all of the steel framed parts collapsed, and none of the concrete framed parts.

But collapse initiation is observed to decend at near free-fall. Collapse initiation was sudden.

Dr. Greening has even pointed this out in some of his recent posts.

Over a very short initial part of the drop, parts of the structure accelerated downwards at 1g. That suggests that, when the columns supporting them broke, they fell until they hit something that slowed them down. Averaging over the entire collapse of the entire building, however, the structure accelerated downwards at 2g/3. That suggests that there was a regular distribution of somethings to slow down the falling block. Both of these results are exactly what would be expected.

Dave

 

[Architect]

Your picture shows it, a partial (local) collapse was possible but complete collapse was not possible!

I hope you're being sarcastic.

 

[MRC_Hans]

Mackey; as a laymen, the sudden failure of the core seems counter-intuitive to me. How fire can cause a sudden failure of 47 vertical core columns is something I will never understand.

Humour me here for a second (stundie this if you want )

Imagine I took 47 dry spaghetti strands and stood them up vertically. Now I apply pressure on the top with my hand. Then I spray hot steam on one section of the 47 dry strands. Eventually the strands will lose strength but certainly not suddenly. It will be gradual, not sudden.

As laymen, I cannot, for the life of me understand the sudden failure of the core......

OK, fair enough. This has been explained before, but by all means:

Assume a structure held up by something, why not spaghetti? (you could actually try this at home) And let's use 47 strands, if you prefer.

The initial situation is this: The supports (spaghetti strands) are stiff, relatively brittle, and they share the weight of the structure above. Ideally, they each carry 1/47 of the weight. We need one more information: The maximum weight each support can carry. Let us assume that each strand of spaghetti can at most carry 1/30 of the weight.

Now you start to soften strands, one at a time, with steam:

First strand softens and bends. It now no longer participates in supporting the weight. The weight of the structure is re-distributed to the remaining 46 strands, which now each have to carry 1/46.

Now, you direct the steam at a second strand. It softens and bends. Now each of the remaining strands must carry 1/45 of the weight.

.
.

Fast forward to:

Now you apply steam to a 17th strand. It softens and bends. Now each of the remaining strands must carry 1/30 of the weight.

Now you apply steam to an 18th strand. It softens and bends. Now each of the remaining strands must carry 1/29 of the weight.

This, however, is above the carrying capacity of a strand of spaghetti (remember, they could at most carry 1/30)! Of course, the load is not quite evenly distributed, and all of the stands don't have exactly the same strenght, so let's assume one is overloaded and breaks. Unlike the slow heating and softening, this is a sudden failure of a stiff and brittle support.

Now each of the remaining strands is loaded with 1/28 of the weight, so more strands are overloaded to the breaking point and suffer sudden failure.

As more and more overload is redistributed to the remaining supports, they all fail in rapid succession. We have a progressive collapse.

I'm sure you can actually make this experiment. Take some strands of spaghetti (for simplicity, I suggest a lower number than 47) and two blocks of clay. Stick the spaghetti strands in one of the clay blocks, in a reasonable pattern. Lay the block on its side on a table and press the other block onto the other end of the strands. Leave the whole thing till the clay has dried (may take a few days). Turn it so it stands on one block, and the other is held up by the spaghetti. For safety (hot steam can give you nasty burns), use a lighter flame to soften strands.

I predict you will experience the following: As you take out strands little will happen first, except that the structure may shift and twist a bit. Suddenly, however, the whole thing will break down and the upper block of clay will fall down at free fall speed.

Hans

 

[Sizzler]

OK, fair enough. This has been explained before, but by all means:

Assume a structure held up by something, why not spaghetti? (you could actually try this at home) And let's use 47 strands, if you prefer.

The initial situation is this: The supports (spaghetti strands) are stiff, relatively brittle, and they share the weight of the structure above. Ideally, they each carry 1/47 of the weight. We need one more information: The maximum weight each support can carry. Let us assume that each strand of spaghetti can at most carry 1/30 of the weight.

Now you start to soften strands, one at a time, with steam:

First strand softens and bends. It now no longer participates in supporting the weight. The weight of the structure is re-distributed to the remaining 46 strands, which now each have to carry 1/46.

Now, you direct the steam at a second strand. It softens and bends. Now each of the remaining strands must carry 1/45 of the weight.

.
.

Fast forward to:

Now you apply steam to a 17th strand. It softens and bends. Now each of the remaining strands must carry 1/30 of the weight.

Now you apply steam to an 18th strand. It softens and bends. Now each of the remaining strands must carry 1/29 of the weight.

This, however, is above the carrying capacity of a strand of spaghetti (remember, they could at most carry 1/30)! Of course, the load is not quite evenly distributed, and all of the stands don't have exactly the same strenght, so let's assume one is overloaded and breaks. Unlike the slow heating and softening, this is a sudden failure of a stiff and brittle support.

Now each of the remaining strands is loaded with 1/28 of the weight, so more strands are overloaded to the breaking point and suffer sudden failure.

As more and more overload is redistributed to the remaining supports, they all fail in rapid succession. We have a progressive collapse.

I'm sure you can actually make this experiment. Take some strands of spaghetti (for simplicity, I suggest a lower number than 47) and two blocks of clay. Stick the spaghetti strands in one of the clay blocks, in a reasonable pattern. Lay the block on its side on a table and press the other block onto the other end of the strands. Leave the whole thing till the clay has dried (may take a few days). Turn it so it stands on one block, and the other is held up by the spaghetti. For safety (hot steam can give you nasty burns), use a lighter flame to soften strands.

I predict you will experience the following: As you take out strands little will happen first, except that the structure may shift and twist a bit. Suddenly, however, the whole thing will break down and the upper block of clay will fall down at free fall speed.

Hans

great explanation!

I'm gonna try it.

thanks for taking the time

 

[1337m4n]

Your picture shows it, a partial (local) collapse was possible but complete collapse was not possible!

Congratulations, you can repeat the very claim that I am challenging without elaborating.




Stop dodging the question: If fire can destroy PART of a building why can it not destroy ALL of a building?

 

[1337m4n]

But collapse initiation is observed to decend at near free-fall. Collapse initiation was sudden.

Ah, the INITIATION. I thought you were referring to the collapse as a whole.

In which case, see Dave Rogers's and MRC_Hans's posts.




Once again, the question is: If fire can destroy PART of a building why can it not destroy ALL of a building?

 

[cisco]

Sizzler have you ever done the trick where you stand on a coke can and it holds you up just fine, and then you lightly tap the sides and it instantly collapses? Think about that.

MRC_Hans' spaghetti is a better analogy but this one is simpler and may be something you've already done.

 

[JHarrow]

From my other thread:



Truthers seem to acknowledge that it is fully reasonable for buildings to experience "partial collapses" due to fire. They even acknowledge this with regards to the Windsor building:

[qimg]http://www.debunking911.com/madrid.jpg[/qimg]

This building experienced a "partial collapse" due to nothing more than a really hot fire.

So logically one would assume that the WTC collapses are perfectly reasonable, right?

Not to the Truthers. According to them, the fact that Windsor only suffered "partial collapse" while WTC suffered "complete collapse" is somehow a critical distinction.





Anyone? Does this make sense to you? Anyone at all? Can someone explain to me how this is supposed to make sense?

If fire can destroy PART of a building why can it not destroy ALL of a building?

As usual, you have completely missed the point of what you quoted.

Debunkers keep arguing that the zone created around 7 showed that they knew it would collapse. This is untrue since collapse zones are standard round all high rise fires.

Why did you not address that point before using my quote for this thread? Could you please address it now?

 

[Unfit4Command]

As usual, you have completely missed the point of what you quoted.

Debunkers keep arguing that the zone created around 7 showed that they knew it would collapse. This is untrue since collapse zones are standard round all high rise fires.

Why did you not address that point before using my quote for this thread? Could you please address it now?

Not many debunkers say that "they (the fire fighters) knew" WTC 7 was going to collapse. Most (from what I've seen) just say that the fire fighters were fearful that the stability of the building had been severely compromised, the building might collapse, and that keeping fire fighters in the area wasn't worth the risk.

"The biggest decision we had to make on the first day was to clear the area and create a collapse zone around the severely damaged 7 World Trade Center, a 47-story building heavily involved in fire. A number of fire officers and companies assessed the damage to the building. The appraisals indicated that the building's integrity was in serious doubt.

I issued the orders to pull back the firefighters and define the collapse zone. It was a critical decision; we could not lose any more firefighters. It took a lot of time to pull everyone out, given the emotionalism of the day, communications difficulties, and the collapse terrain."
~~Daniel Nigro

 

[leftysergeant]

To quickly address JHarrow's comments, the collapse zone is an area from which all non-essential personnel are excluded while the fire fighting operation is in progress. What made this instance unique is that fire fighters were excluded and fire fighting operations ceased due to the imminent collapse.

As to the failure of the columns in the towers, everyone seems to be concntrating too much on the strength and failure of the columns themselves. More attention should be directed to the joints between structural elements. The heating was uneven on all floors, thus the expansion and contraction of structural elements was unequal. This has to have placed a far grerater than planned for stress on all joints. It is quite probable, in my view, that the failure of the joints played fully as important a role as the failure of the columns in initiation of the collapse.