1200 Architects And Engineers

Originally posted by GenRadek
Did you forget those lovely little floor trusses? You remember those right? The ones that helped initiate the collapse by sagging, pulling in the exterior columns prior to the global failure? Yeah those trusses. The very light steel trusses that are very susceptable to fires when fireproofing is dislodged.

Nice of you to join us again, "Gen."

You say the trusses initiated collapse by sagging, pulling in the exterior columns.

Can you show me the experiments where NIST verified this, or else admit the fact that you are offering an unsubstantiated hypothesis as if it has already been proven?

Originally posted by bsbray11
Originally you were arguing that they WERE a valid comparison.

Now you're saying they're NOT a valid comparison because of the core structures differing.

Consider this proof that your argument has been defeated. You are now arguing AGAINST their comparison while earlier you were arguing FOR their comparison. This is hilarious.

Why is it that I've had to ask you to re read previous posts of mine in two threads now? It's not that hard to spend the time to understand what I'm actually arguing, instead of just assuming i'm arguing against you at all times.

Here is an important post to read. That is why I pointed out the fact that any comparison made would need to take into account these factors. This is why you're ignoring these factors in trying to compare the two buildings, because they are the major factors in determining what fire will do to a building. If the steel is unprotected, it hardly matters how thick it is, as steel is an excellent conductor of heat. It requires fireproofing. This is why building codes require it. This is why the WTC was fireproofed.

What about this is so hard?

edit:

Can you show me the experiments where NIST verified this, or else admit the fact that you are offering an unsubstantiated hypothesis as if it has already been proven?

You just quoted a post of mine with a picture of it occuring. There is a video of the failure initiating. What exactly is it you want NIST to do? Please post it in my 'State of the Truth Movement' thread as a potential experiment.

reply to post by exponent

Sure, but deceleration is a result of any impact, so that force is exerted in all impacts.

So if the impacts are significantly lessened with controlled demolition techniques the decelerations are also lessened.

It's even more annoying than that if we deal with energy because we have to estimate how much energy was expended in destruction too. This has been done in the Bazant series of papers though.

Which is why I prefer to deal with accelerations. Conservation of energy requires a lot of estimation which can be biased towards a predetermined conclusion.

Not disagreeing here, but the next paragraph seems to contradict your view on this?

The first paragraph explained how a tilting top section would not be immune to the expected decelerations. The second paragraph explained that I don't have a problem with collapse initiating, just with the rate it maintained through undamaged structure. I don't see the contradiction?

In the previous paragraph, you agree that the momentum transfer is identical, and this is what determines the collapse rate primarily,

I agree that the momentum transfer would be the same for a leaning and non-leaning top section to crush the lower structure, however I never said that is the primary factor in determining collapse rate. Yielding of steel structural elements and crushing of concrete would also be large factors requiring large forces.

as even if the lower sections provide significantly more force, if the energy required to decelerate the object is significant, the results become relatively insensitive to the force applied.

Which is why I'm primarily concerned with the difference (or lack of) between the top section acceleration through the initiation zone and when it first meets undamaged structure.

Plus, lets face it, the measurements of descent acceleration are not hugely accurate as they are based off video records which are several metres per pixel. Deceleration by a fraction of this would simply not be detectable in the data we have.

About three meters per pixel at 480p resolution. I would expect some sort of measurable deceleration, or at the very least, a smaller uniform rate of acceleration through undamaged structure than the initiation zone. Can you explain how the undamaged structure provided the same resistance to collapse as the heavily damaged initiation zone?

Well those columns previous held 50% of the mass of the towers, so it's not hugely surprising they didn't fail in compression. They did actually fail at the bottom, but we don't know whether this was due to moment or shear or what exactly.

The columns around the top half failed during collapse, probably in compression, only at the bottom did they remain and form a spire. This spire was unlikely to have failed due to moment, as it remained straight and didn't topple over (as if something blew the bottom out).

That's definitely not what happened, the internal structure was destroyed horizontally across the building, until it could not hold up its own self weight. At this point failure is extremely rapid and will be progressive. An analogy I've used before is taking a weight, tying it to a hook with three strings under equal tension, where the load is 80% of the maximum load of all three strings. If you were to then cut one string, the other two would fail almost instantaneously. This is the mechanism behind progressive collapse.

The weight with three strings would fail asymmetrically (not straight down).

If it starts out like this: \|/

Then you cut the right hand one to end up with this: \|

As soon as you do that the weight will begin to swing to the left, wanting to make this shape: \/

But before that shape is made the middle string will fail because it is carrying more tension than the left hand string due to its dimensions. This causes it to swing even more to the left, leaving: \ which is swinging to the left like a pendulum and also quickly breaks, leaving the weight on a downwards-left trajectory. This is similar to what I would expect from a horizontal failure occurring across WTC7. By the time horizontal failure progressed across to the opposite side of the structure to where it started, the side of the structure where horizontal collapse started should have already been well and truly underway (collapsing). If it was legitimately weakened to the point where it was providing the same resistance to collapse as a structure made of marshmallows then what was it waiting for?

Who said that if the force was less than the static force, then it must be suspicious.

Is it not suspicious if the structure is suddenly unable to provide an equal force to when it was holding itself up?

However, the equations he uses to determine this only equal static force in one condition: the building doesn't collapse.

What? No, he measures it on buildings as they collapse.

Using his logic, any collapse is suspicious, because the resultant force calculations taking into account only acceleration over a large period result in less force than the self weight.

No, the only suspicious gravitational collapses are those which experience no deceleration once undamaged structure is being destroyed. David has done the same analysis on gravitational explosiveless demolitions and the results were as expected:

To initiate and onset collapse a weakened section (a few levels) of the structure is artificially destroyed. The top section accelerates through this section and picks up momentum to destroy the lower structure. Once the top section meets the lower structure, measurable and significant deceleration of the top section takes place as it applies a large amount of force to destroy the bottom section. Nothing suspicious there.

There are three noticable things about this gif:
1. It ignores the collapse of the east penthouse, which occured 6 seconds before this begins. This was asymmetric, caused by the failure of a single column, and is what caused the damage that resulted in the collapse
2. The central penthouse began to collapse before the western penthouse, and before the exterior of the building.

The purpose of the gif was to highlight the highly symmetrical manor in which the exterior structure collapsed, as this is important for reasons outlined above.

I'm not that familiar with the OS version of what happened during 7s collapse. If the internal structure had already collapsed, then why would the outer structure even collapse at all, and how could it come down at and near free fall? If it is not supporting the inner structure, then it is very minimally loaded. It would be like a birdcage. Sorry if I've missed something.

3. The period at which it reached free fall occurs a couple of seconds after the global initiation. If this was caused by explosives taking out all of the columns, what structural element resisted the collapse for so long?

Above I'm asking you the same thing for your version of events. My answer is the explosives were timed that way - drop the inner before the outer to ensure a nice tidy collapse.

reply to post by bsbray11


Oh boy, you know, I thought that after all these years, after all these discussions, you would have at LEAST read the NIST report in full, instead of looking on the TM websites that do nothing but mock it and ignore it. Well anyways since you obviously missed a lot from NIST, I'll give you the direct paper on it:

wtc.nist.gov...

Go down to pages 54-72 of the PDS document and be sure to go through it all on what happened prior to collapse. It was observed, and recorded. Oh and then go on lower and go to the fire tests on the floor trusses from pages 167 onward and then from pages 181 onward of the exterior columns. And then be sure to combine everything you have read and understand that this was a multi-area of failure where all of these things were all happening at the same time together. THAT is the key to understanding what happened. Oooh and page 186 has some REAL fascinating comments on the the failures of column buckling from the loss of support at floor truss seats

But before i go on, I have to say this. I've noticed that you and many of the TM supporters like to have selective amnesia when it comes to 9/11 and the events. For example, talking about how fires cannot bring down the Twin Towers while ignoring (forgetting) the airplane impacts. Or saying how the towers were suppose to survive multiple hits and therefore should not have collapsed while ignoring the fires afterward. Then we have that the steel could not have failed when there are quite a few instances where steel structures did fail from fire alone. The exterior columns could not have been seriously compromised by the fires and therefore it should not have collapsed, while ignoring the floor trusses that helped pull in the exterior columns prior to collapse. And then we have those that forget everything that happened and forget to include everything and only focus on one thing. The thing to remember is that everything was happening at the same time and to take it all together. The plane impact caused the initial severe damage to the buildings, helped start the fires which spread causing a loss of structural integrity where the steel softened from the fires AND from the additional loads and stresses placed on the surviving members. Remember, heat and heavy loads together are not steel's friends.

So you have some reading to do, get started. You wanted an answer, you got it, go read it. I'm surprised you havent gotten this far yet into the NIST report. I mean really, there is quite a bit of information you have missed, now be it purposely, or genuinely never getting around to it, whichever, you should have at least researched this before challenging others about something you dont fully understand or know about it yourself. Well I just gave you all the answers, its up to you how you want to proceed. The observed and tested behavior of the floor trusses and the exterior columns when exposed to the fires and subsequent sagging of the floor trusses and inward pulling and failure of the exterior columns leading to global failure. All in the link provided. Enjoy.

OK, so this reply to Azp420 is going to be difficult, as it encompasses two videos and several points he's made. What i'll do is start by commenting on the videos primarily used as a reference:

There are a few problems with this video. The first will be dealt with in reference to the second video.

The second is the comparison with a known demolition. Here Chandler makes several mistakes. The first is that the initial descent stage is drastically different. The world trade centres were fully occupied, and at 'live load'. What damage had been done affected only load carrying capacity, and not the mass of the floors in question. However, in the demolition it's compared to, there is a large manufactured gap in the building, where mass and load carrying capacity was removed. This results in a much higher initial acceleration for the known controlled demolition, and means that any subsequent changes are going to be more visible.

The next problem is the construction of the buildings, they are not comparable in any way, and we have no information on the safety factor involved. As it was such a short and small building in comparison, self weight would not have been a great issue in construction, and so it's hard to compare the two buildings directly in terms of energy transfer. These problems are ignored and not even mentioned, as if they do not factor in to the physics at all. This is not true.


This is the original video I had seen and contains the most egregious mistake that people appear to be repeating. At about 1:30 into the video Chandler claims two things.
1. The force applied by the upper block, and the force applied by the lower block are identical
2. If this were a natural collapse, then the downward acceleration would not be linear

Both of these are incorrect, so I will start with the first one. Force is mass times acceleration, and it's true that Newton's third law does state in simplistic form that the two forces are equal. However, this is not to be applied in a general sense between two complex bodies, it applies purely to the molecules the substance is made from. An easy way to show how this is wrong is to assume for a second the forces balance as Chandler says. In that case we know that net force would be 0, and as mass is positive, the only other variable is acceleration, which must be 0 in this case. However this is a collapsing building, and Chandler also provides values for the acceleration of the collapse. These two are mutually exclusive. The forces between the various impacting parts certainly can be stated to be equal, but a force represents only a potential to do work, this is why an energy analysis is required to see just how much of the kinetic energy of the upper block the lower one can resist.

The second point is even more incorrect, because no evidence is presented for it at all. It is simply stated that it must be true due to Chandler's understanding of the mechanics of a falling building. It is not true however, in fact it is perfectly possible for the acceleration to increase during the period of collapse. If the mass is high enough and the energy expended in breaking objects low enough then the following will happen. As each floor is impacted, some energy will be consumed and removed from the upper block's kinetic energy, however, the resultant mass which has been added will then be accelerated under gravity before it impacts the next floor. If the mass gain is great enough to offset the energy loss, then the rate of acceleration will increase as the building collapses.

Chandler addresses none of this, and his presentation of the physics involved is far too simplistic and involves too short a measurement period to make predictions about the whole collapse.

Now, on to the substance of Azp420's post.

Originally posted by Azp420
So if the impacts are significantly lessened with controlled demolition techniques the decelerations are also lessened.

This is definitely true, but you'll not find any buildings of the size of the WTCs being demolished, and those that are demolished using a similar method show a higher acceleration than the WTC, indicating the WTC is still doing more work than these buildings.

Which is why I prefer to deal with accelerations. Conservation of energy requires a lot of estimation which can be biased towards a predetermined conclusion.

That's true, but it is very easy to be convinced by incorrect logic. The estimation for conservation of energy has already been done though, with the various variables biased towards collapse survival. It's not like this information doesn't exist, it's just that it is highly technical to read and rarely challenged with any substance.

The first paragraph explained how a tilting top section would not be immune to the expected decelerations. The second paragraph explained that I don't have a problem with collapse initiating, just with the rate it maintained through undamaged structure. I don't see the contradiction?
...
I agree that the momentum transfer would be the same for a leaning and non-leaning top section to crush the lower structure, however I never said that is the primary factor in determining collapse rate. Yielding of steel structural elements and crushing of concrete would also be large factors requiring large forces.

Ok so we have momentum transfer (accelerating the various objects which are minimally destroyed), concrete crushing (mostly identical floor by floor with some minor differences) and yielding of steel structural elements (increasing strength as the building collapses)

The only differences we have between damaged and undamaged sections is a reduction by about 50% (safety factor was around 2 for WTC columns) of the static load carrying capacity. The rest of the energy sinks should remain pretty similar.

The problem again here is that this is an energy analysis, and to know how the WTC should have accelerated we need to do this. Now, it has been done, by Bazant etc, but I don't expect you to take that at face value, I just don't understand why you think that this would be a dominant energy sink, as structural steel is not designed in any way to be impacted, it is considerably more brittle than many people would expect.

The columns around the top half failed during collapse, probably in compression, only at the bottom did they remain and form a spire. This spire was unlikely to have failed due to moment, as it remained straight and didn't topple over (as if something blew the bottom out).

It wasn't particularly straight, it was only one corner of the building survived, and bear in mind that they were not continuous sections, it's not particularly surprising that they would fail at a lower level, the lower on the structure, the more force being exerted.

The weight with three strings would fail asymmetrically (not straight down).

This is true, and vector addition can be used to determine the tension forces on the strings, but you would find that the closer they are to vertical and the more equal the tension, the faster the failure would occur. In WTC7, all columns were vertical and so this analogy doesn't really hold up that far, although we do see the effects in that the penthouse collapses prior to the outer walls.

If it was legitimately weakened to the point where it was providing the same resistance to collapse as a structure made of marshmallows then what was it waiting for?

There's always going to be a point that weight overcomes carrying capacity, it took only a few seconds once the east penthouse collapsed into the building for the global collapse to begin, and it does quickly progress. I'm not understanding the criticism here.

No, the only suspicious gravitational collapses are those which experience no deceleration once undamaged structure is being destroyed. David has done the same analysis on gravitational explosiveless demolitions and the results were as expected:

Let us take the collapse that is illustrated in the first video I linked. In this he graphs the downward velocity of the building and draws an acceleration curve on it. The part that he forgets to mention is that shortly after the 'free fall portion' has completed, the building impacts and still accelerates for a few sample periods. According to his logic, because the building is not decelerating in this period, this section of the building is also being destroyed by something other than the weight of the above section.

But we know this not to be true, we know that the demolition mechanism was to knock out a couple of floors worth of support, yet the criteria you both seem to be applying 'acceleration during collapse = controlled demolition' seems to mean that there were secret extra demolitions going on here too.

I'm not that familiar with the OS version of what happened during 7s collapse. If the internal structure had already collapsed, then why would the outer structure even collapse at all, and how could it come down at and near free fall? If it is not supporting the inner structure, then it is very minimally loaded. It would be like a birdcage. Sorry if I've missed something.

In WTC7 the outer structure was not a significant load bearing structure, it was the inner frame that carried the majority of the loads. The 'official story' goes briefly like this:

1. Beam seat failure due to thermal expansion at around floor #12
2. Bay contents collapse and cause a vertical progressive collapse down to around floor #7
3. Column #79 fails in compression due to unrestrained vertical length
4. East penthouse collapses down to around the floor 7-12 range
5. In doing so it does significant damage to the moment frame structure in the core, quickly weakening its vertical carrying capacity and progressing westwards
6. The central section of the internal structure begins to collapse, the central penthouse is seen to descend
7. The progressive failure reaches the west side of the building, the west penthouse begins to descend and a fraction of a second later, the global collapse begins.

It is because the internal frame has already failed that the acceleration is so great, the building at that point was being held up by the minimal strength of the external walls and what structural elements did not fail due to the east penthouse collapse.

Above I'm asking you the same thing for your version of events. My answer is the explosives were timed that way - drop the inner before the outer to ensure a nice tidy collapse.

If this is the case, why did the east penthouse collapse 6 seconds before the start of the global collapse, and why do microphones that clearly pick up the collapse, not pick up any explosive sounds? Indeed some of the quotes referenced by 'truthers' say that there was an extremely loud noise approximately a second or so before the global collapse begins. While this is interpreted as evidence for explosives by truthers, it occurs 4-5 seconds after the east penthouse has already begun collapsing. If the explosives produce loud noises, why did the east penthouse fail without such noises.

Anyway there's an awful lot to talk about here, and I am sure I will have made many grammar/spelling and probably some logical mistakes too. Feel free to point them out.

Force is mass times acceleration, and it's true that Newton's third law does state in simplistic form that the two forces are equal. However, this is not to be applied in a general sense between two complex bodies, it applies purely to the molecules the substance is made from.

Clearly Newton was talking about molecules, because Newton was around in 1794.

en.wikipedia.org...

According to Merriam-Webster and the Online Etymology Dictionary, the word "molecule" derives from the Latin "moles" or small unit of mass.
Molecule (1794) – "extremely minute particle," from Fr. molécule (1678), from Mod.L. molecula, dim. of L. moles "mass, barrier". A vague meaning at first; the vogue for the word (used until late 18th century only in Latin form) can be traced to the philosophy of Descartes.

Further, this quote from Newton himself in his third law obviously says the forces are not equal between the bodies:

If a body impinges upon another, and by its force changes the motion of the other, that body also (because of the equality of the mutual pressure) will undergo an equal change, in its own motion, toward the contrary part.

Oh wait, they are equal?

Stop talking out your butt and spreading lies.

Originally posted by mnemeth1
Oh wait, they are equal?

Stop talking out your butt and spreading lies.

If you don't know what you're talking about, it's not a good idea to try and burn someone else. Do you think that only discovered objects at the time of a theory's construction can be applied? That is just silly.

Nothing I've said in my post contradicts newton's third law, it is just that Chandler tries to aggregate all collisions together and measure them as a whole, and then claim that this proves something that it does not. Care to explain the criticisms I have made?

Originally posted by exponent

Originally posted by mnemeth1
Oh wait, they are equal?

Stop talking out your butt and spreading lies.

If you don't know what you're talking about, it's not a good idea to try and burn someone else. Do you think that only discovered objects at the time of a theory's construction can be applied? That is just silly.

Nothing I've said in my post contradicts newton's third law, it is just that Chandler tries to aggregate all collisions together and measure them as a whole, and then claim that this proves something that it does not. Care to explain the criticisms I have made?

Chandler is specifically discrediting the State official conspiracy of PANCAKE COLLAPSE

This requires large bodies (ie floors) smashing into each other as the cause of destructive force.

This official conspiracy theory is what Chandler is debunking in his videos.

Why you are trying to drag molecular physics in to this debate is beyond me.

Originally posted by mnemeth1
Chandler is specifically discrediting the State official conspiracy of PANCAKE COLLAPSE

This requires large bodies (ie floors) smashing into each other as the cause of destructive force.

This official conspiracy theory is what Chandler is debunking in his videos.

Why you are trying to drag molecular physics in to this debate is beyond me.

I know what he's trying to debunk, but he uses the principles in the video incorrectly. By measuring the aggregated acceleration, he ignores any energy transfer, and proudly proclaims that there should be a jolt, by comparing it to a building of completely different construction and with a different collapse method.

I'm not trying to drag molecular physics into the debate, i'm pointing out that forces are not applied universally and instantaneously. A common place this is demonstrable is in suspension design. Suspension has what's called compression damping, which is a resistance to the forces applied when compressing the spring. This resistance however will not stop massive instantaneous forces being felt by the end of the suspension, even though the two are connected the forces do not transfer instantaneously. This is why many modern suspension systems have seperate high speed and low speed compression, to deal with different criteria.

By ignoring the fact that these collisions are independent, and that the analysis must be carried out on them, Chandler ignores the reality of the collapse, and tries to provide a superficial case which favours some unnamed alternate hypothesis. Let's remember that the acceleration remains constant, so if the logic being used is correct, the conspirators either allowed the impact zone to collapse normally and calibrated their explosives to do the same damage to each subsequent floor, or they added extra damage to the impacted floors and matched that damage further down.

Seems rather unlikely doesn't it. In no way does his theory make sense, it's just superficially plausible if you don't fully grasp the physical interactions he's discussing.

Originally posted by exponent
I know what he's trying to debunk, but he uses the principles in the video incorrectly. By measuring the aggregated acceleration, he ignores any energy transfer, and proudly proclaims that there should be a jolt, by comparing it to a building of completely different construction and with a different collapse method.

I'm not trying to drag molecular physics into the debate, i'm pointing out that forces are not applied universally and instantaneously. A common place this is demonstrable is in suspension design. Suspension has what's called compression damping, which is a resistance to the forces applied when compressing the spring. This resistance however will not stop massive instantaneous forces being felt by the end of the suspension, even though the two are connected the forces do not transfer instantaneously. This is why many modern suspension systems have seperate high speed and low speed compression, to deal with different criteria.

By ignoring the fact that these collisions are independent, and that the analysis must be carried out on them, Chandler ignores the reality of the collapse, and tries to provide a superficial case which favours some unnamed alternate hypothesis. Let's remember that the acceleration remains constant, so if the logic being used is correct, the conspirators either allowed the impact zone to collapse normally and calibrated their explosives to do the same damage to each subsequent floor, or they added extra damage to the impacted floors and matched that damage further down.

Seems rather unlikely doesn't it. In no way does his theory make sense, it's just superficially plausible if you don't fully grasp the physical interactions he's discussing.

Chandler is applying the physics correctly, it is you who are obfuscating the matter.

Continuous acceleration through the path of highest resistance is IMPOSSIBLE, we should see DECELERATION as energy is bled off in each sequential impact of floors.

Chandler is not aggregating this, he is demonstrating on a frame by frame basis that we see no deceleration in the collapse sequence.

Chandler also points out correctly that, at most, only the top 24 floors could possibly be destroyed in such a manner before all of the energy would have been dissipated.

I am not choosing sides in this. I am only offering my personal thoughts.

If these buildings were pre-wired to collapse, then how were the impact points of the planes into the buildings taken into account when the detonation timing was planned?

Would the impact points of the planes not have an effect on the planned collapse?

From watching the video of the towers falling, it appears to me that none of the lower parts of the towers start to fall untill they are impacted from above.

All of the videos of buildings brought down by explosives that I have seen, appear to collapse from the ground up.

This is just my personal opinion. I am not saying what happened, one way or another.

Originally posted by mnemeth1
Chandler is applying the physics correctly, it is you who are obfuscating the matter.

Continuous acceleration through the path of highest resistance is IMPOSSIBLE, we should see DECELERATION as energy is bled off in each sequential impact of floors.

What about the massive amounts of gravitational potential energy that is converted into kinetic energy? You seem to forget it exists:

Chandler also points out correctly that, at most, only the top 24 floors could possibly be destroyed in such a manner before all of the energy would have been dissipated.

Gravitational energy is = mgh, it's not limited by the number of floors involved. Perhaps this is where your confusion is arising from

Originally posted by exponent

Originally posted by mnemeth1
Chandler is applying the physics correctly, it is you who are obfuscating the matter.

Continuous acceleration through the path of highest resistance is IMPOSSIBLE, we should see DECELERATION as energy is bled off in each sequential impact of floors.

What about the massive amounts of gravitational potential energy that is converted into kinetic energy? You seem to forget it exists:

Chandler also points out correctly that, at most, only the top 24 floors could possibly be destroyed in such a manner before all of the energy would have been dissipated.

Gravitational energy is = mgh, it's not limited by the number of floors involved. Perhaps this is where your confusion is arising from

I'm not the one who is confused here. You are essentially making the claim there is no kinetic energy lost in the impacting of floors.

What we should see is a neat stack of pancaked floors tightly packed into each other about 12 floors below the impact point if "pancaking" was to blame.

Originally posted by mnemeth1
I'm not the one who is confused here. You are essentially making the claim there is no kinetic energy lost in the impacting of floors.

Where exactly am I making this claim? I put together a list of the primary elements we should consider in energy loss:

Originally posted by exponent
momentum transfer (accelerating the various objects which are minimally destroyed), concrete crushing (mostly identical floor by floor with some minor differences) and yielding of steel structural elements (increasing strength as the building collapses)

Did I miss any important ones?

What we should see is a neat stack of pancaked floors tightly packed into each other about 12 floors below the impact point if "pancaking" was to blame.

It's not like the floors were particularly strong, they were a few inches of lightweight concrete. They were almost certainly rapidly destroyed. However, Chandler uses the word 'consumed' which is not accurate, their mass was not converted into energy, and it was continuously accelerated by gravity, adding energy to the system.

The question is, does the energy addition through gravity come to more than was taken in crushing, damaging and accelerating? The answer is yes, by a significant margin. See the Bazant series of papers for details, you can find the most appropriate one here

reply to post by exponent


The paper is demonstrably wrong for several reasons.

www.ae911truth.org...

Originally posted by mnemeth1
The paper is demonstrably wrong for several reasons.

www.ae911truth.org...

Anders Bjorkman has said before that the towers would not collapse if you were to drop a section on top of another from miles up. He has been repeatedly debunked on JREF and in all manner of papers. He just doesn't listen to anything you say. I've debated him a few times but it just ends up being tedious.

Which of his criticisms do you understand, and can you explain how they are valid?

Originally posted by exponent

Originally posted by mnemeth1
The paper is demonstrably wrong for several reasons.

www.ae911truth.org...

Anders Bjorkman has said before that the towers would not collapse if you were to drop a section on top of another from miles up. He has been repeatedly debunked on JREF and in all manner of papers. He just doesn't listen to anything you say. I've debated him a few times but it just ends up being tedious.

Which of his criticisms do you understand, and can you explain how they are valid?

The floors of the upper portion must necessarily collapse together as each successive floor beneath them is destroyed. - this is the only mechanism by which additional kinetic energy can be applied to the keep the collapse going.

What you are claiming is that the above statement is not true, and that kinetic energy is not dissipated and does not need to be applied through the collapsing of the "pile driver".

Apparently it just magically comes from space aliens - right?

Originally posted by mnemeth1
The floors of the upper portion must necessarily collapse together as each successive floor beneath them is destroyed. - this is the only mechanism by which additional kinetic energy can be applied to the keep the collapse going.

What you are claiming is that the above statement is not true, and that kinetic energy is not dissipated and does not need to be applied through the collapsing of the upper floors.

Not at all. For every floor destroyed, a certain amount of energy is removed, then, the debris accelerates through 12 feet under gravity. This adds more energy than was taken away, that's what Bazant et al have repeatedly proven.

Apparently it just magically comes from space aliens - right?

It comes from the stored potential energy due to gravity.

Originally posted by exponent
Not at all. For every floor destroyed, a certain amount of energy is removed, then, the debris accelerates through 12 feet under gravity. This adds more energy than was taken away, that's what Bazant et al have repeatedly proven.

It comes from the stored potential energy due to gravity.

And Bazant was just demonstrated to be utterly wrong in his assumptions that this could destroy the entire building because as each impact occurs, it must necessarily collapse one floor of the pile driver itself until there is no more collapse energy available.

This would, in a perfect pancake scenario, run out of steam 12 floors beneath the impact point.

Further, no matter how you slice it, constant acceleration through the path of most resistance would never occur.

reply to post by exponent


Debris is the same mass as the building, so it would not add any acceleration to the collapse. What would hurt more, a ton of bricks thrown at you or a ton of pulverized bricks? You might die either way but I'd choose the pulverized bricks over the compact bricks any day.