Would the WTC Twin Towers have collapsed from fire alone, without plane impact?

[benthamitemetric]

If you're looking for me to concede some kind of point I think you'll have to give me some time. I still don't understand (to my own satisfaction) how the buildings collapsed.

That's fine. If you cannot articulate specific reasons why you disagree (and I think you see the inherently unpersuasiveness of the vague assertions that (i) somehow the unbroken columns at the edge of the floor failure line could meaningfully retard the collapse by catching the floor pans that had already been sheared off the truss connectors or (ii) somehow the tower was expelling more than a floors' assembly's worth of debris (in addition to any columns that were ejected) for every floor that failed), you should realize your disagreement is just cognitive dissonance at this point, however. The top blocks contained too much mass for the floors to stop after the initial failure and that really is the end of it.

I guess I just don't understand this emphasis on the floor trusses, as if they were what was holding up the building.

As has been explained to you many times, the floors were providing lateral support for the columns, which support was required for the columns to stand. After the initial collapses, which we can all watch to our satisfaction up close and in slow motion, the columns were no longer supporting the top blocks. As a result, the top blocks moved down and impacted the floor systems. The columns below the initial failure point had no way of "catching" any of that debris. The weight of that debris alone is so far in excess of what any floor could bear, that no floor below the initial failure point could survive, triggering a runaway collapse wherein each successive floor failure *added* to the problem.

And the core was very robust, which is why much of it withstood the collapses of the floors in both towers, which has been shown to you several times in this very thread. But they could not stand long without lateral support, which, again has been explained to you, and they ultimately toppled except for a few stories of height. In any case, the only survivors who were inside the buildings during the collapses were in one of the stairwells within the core, again illustrating the the floors were the reason for the runaway failure and there were no controlled demolition devices acting on the columns to assist the floor collapses.

So now we have two "competing" theories:

1. That the floors could arrest the collapses, which relies on no maths or coherent logic and which then requires the existence of unspecified devices that were neither observed in the debris of the towers (though the NYPD bomb squad and expert engineers were at the site for the duration of the clean-up) nor actually seen or heard acting during the collapse.

2. That the floors could not arrest the collapses, which is consistent with easily understood and easily verifiable realities of their construction and the mass of the top blocks of the building, is consistent with the physical evidence in the debris pile and the video evidence of the collapses themselves, as well as the testimony of the witnesses who survived the collapsed within a stairwell, and which requires no additional unspecified devices.

Obviously, no. 2 is the only reasonable choice, but cognitive dissonance is a helluva drug.

Given that we've also moved well beyond the initiation question, I'd say that brings this thread to a close. Yes, fires could conceivably have caused the collapses without the airplane crashes, but such a fire scenario was highly unlikely and the towers were likely robust enough to survive many very extreme fire scenarios, and, if there was a collapse initiated from fires alone akin to the collapses initiated on 9/11, such collapse would proceed to a total collapse just the collapses on 9/11 did because the forces driving the progressive collapse through each floor would be the same.

 

[Efftup]

I guess I just don't understand this emphasis on the floor trusses, as if they were what was holding up the building. In my mind, the entire weight of the upper block wouldn't be applied to the floor below, because the core columns would be providing resistance. It reminds me of this 3D animation that I believe was presented in a 2002 documentary purporting to explain the collapses. They animated the floors "pancaking", but just left the core standing there, strangely:

I'm sure somebody with more knowledge can chime in on this to correct me but my basic understanding is this:
The core is very strong and can take a lot of load vertically but is weaker in respect to lateral or twisting forces so needs something to keep it straight.
The facade is strong but not as strong as the core but likewise is strong vertically and weaker laterally.
The floors are relatively weak in comparison and are connected to the core and the facade by these trusses. They are held up by the core and the facade, BUT they also provide the lateral support that the core and facade need to stay straight.
When the floor collapses, it is basically the comparitively super weak connections between the floor and the core and facade that are breaking.
so the floor falls down without the core or facade breaking. This then impacts the next floor with enough force to break that floors connections. and we have a progressive collapse.
THEN, because the floors are no longer there, neither the core or the facade have the lateral support they need and so they will then break.
The core is not made of 415m long steel beams, it is made of many 3 story high beams which are bolted together and again, the bolts are the weakest point.
So FIRST, the floors all collapse, then the facade peels away and lastly the core will break into pieces also.
This is exactly what we see happen when the towers collapse, the floors collapse and then the facade peels away and if you see after the main tower has fallen, a good deal of the core is actually still standing at the end.

 

[deirdre]

That's fine. If you cannot articulate specific reasons why you disagree (and I think you see the inherently unpersuasiveness of the vague assertions that (i) somehow the unbroken columns at the edge of the floor failure line could meaningfully retard the collapse by catching the floor pans that had already been sheared off the truss connectors or (ii) somehow the tower was expelling more than a floors' assembly's worth of debris (in addition to any columns that were ejected) for every floor that failed), you should realize your disagreement is just cognitive dissonance at this point, however.

i'm not sure that is a fair thing to say. there were several topics Mick and others spent alot of time explaining to me that i just didnt get because i wasn't visualizing the correct thing. and then that night or days or weeks later i'd be falling asleep and "OH! i get it!"

one problem with 911 threads is alot of people throw alot of info in all at once (and sometimes contradictory info), and that makes processing very confusing for most people. If me and my co-workers in my field started bombarding you with a ton of information that seems counterintuitive to you, you'd need time to step back and process too.

 

[Henkka]

As has been explained to you many times, the floors were providing lateral support for the columns, which support was required for the columns to stand.

So you could do a controlled demolition of the tower just by attacking these flimsy little things with explosives?



That doesn't look like it would take a powerful explosive to take out the connection. Cut the trusses on a couple floors to get the unstoppable cascade going, columns lose lateral support, and it's RIP World Trade Center. Doable?

 

[benthamitemetric]

So you could do a controlled demolition of the tower just by attacking these flimsy little things with explosives?



That doesn't look like it would take a powerful explosive to take out the connection. Cut the trusses on a couple floors to get the unstoppable cascade going, columns lose lateral support, and it's RIP World Trade Center. Doable?

Why not? Of course, as with the real collapses, it wouldn't be meaningfully "controlled"; but it would all collapse if you got a sufficiently larger top block moving by destroying lateral support of the columns below it sufficiently to allow those columns to buckle. Of course, the truss connections breaking is not why collapse *initiated* in the case of the towers (it's why the collapse progressed), so you seem to be conflating things somewhat in attempt to play the incredulity card here again, but there is an infinite number of ways to destroy a building and that's one of them.

 

[Henkka]

Why not? Of course, as with the real collapses, it wouldn't be meaningfully "controlled"; but it would all collapse if you got a sufficiently larger top block moving by destroying lateral support of the columns below it sufficiently to allow those columns to buckle. Of course, the truss connections breaking is not why collapse *initiated* in the case of the towers (it's why the collapse progressed), so you seem to be conflating things somewhat in attempt to play the incredulity card here again, but there is an infinite number of ways to destroy a building and that's one of them.

Because it's absurd... That these were some of the strongest buildings ever made, but could also be demolished rather simply with this "one weird trick" of cutting those flimsy trusses. How long would it take for a CD company to set that up, and how much would it cost? Probably not that long, not that much. You could even probably cut most of them with a cutting torch, and then set tiny explosives on the last ones to deliver the final blow. Is this what Skilling was referring to when he said shaped explosives could do massive damage, he knew all you needed to do was take out the trusses on a few floors and the tower was history? No need to cut the much thicker steel in the core at all? Which looked like this, btw:



Now those might look impressive, but in reality it was these bad boys doing all the hard work:

 

[benthamitemetric]

Because it's absurd... That these were some of the strongest buildings ever made, but could also be demolished rather simply with this "one weird trick" of cutting those flimsy trusses. How long would it take for a CD company to set that up, and how much would it cost? Probably not that long, not that much. You could even probably cut most of them with a cutting torch, and then set tiny explosives on the last ones to deliver the final blow. Is this what Skilling was referring to when he said shaped explosives could do massive damage, he knew all you needed to do was take out the trusses on a few floors and the tower was history? No need to cut the much thicker steel in the core at all? Which looked like this, btw:

[image omitted]

Now those might look impressive, but in reality it was these bad boys doing all the hard work:

[image omitted]

All you have is incredulity. In reality, the building was an interdependent system. All buildings are. Without sufficient lateral support, its columns would buckle, as all columns do without sufficient lateral support. Anyway, at this point, you're not even making any argument relevant to this thread. You can't come up with any reason why any floor system could support the falling top blocks (and we know from rudimentary calculations that they could not), and now you are merely asserting, without any basis beyond "but look at those things, they look strong to me!," that the columns would not buckle if they lacked lateral support.

Here's a great primer on buckling. It is a very well understood phenomena:




(And, by the way, if the towers were only 8 stories tall, as in your construction photo, I'm sure the core columns would have be fine without the lateral support from the floor system, as they are in the photo. But you are missing 100+ floors. Think about it.)

 

[Gamolon]

No need to cut the much thicker steel in the core at all? Which looked like this, btw:

Just an FYI...

Those core box columns did not go all the way up the towers.

 

[Henkka]

All you have is incredulity. In reality, the building was an interdependent system. All buildings are. Without sufficient lateral support, its columns would buckle, as all columns do without sufficient lateral support. Anyway, at this point, you're not even making any argument relevant to this thread. You can't come up with any reason why any floor system could support the falling top blocks (and we know from rudimentary calculations that they could not), and now you are merely asserting, without any basis beyond "but look at those things, they look strong to me!," that the columns would not buckle if they lacked lateral support.

(And, by the way, if the towers were only 8 stories tall, as in your construction photo, I'm sure the core columns would have be fine without the lateral support from the floor system, as they are in the photo. But you are missing 100+ floors. Think about it.)

Well, I'm just pointing out a necessary conclusion from what you believe about the collapse. You believe the building collapsed because a plane flew into it, and it did some impact damage, but mostly the building was done in by the fires that ensued. A plane flying into the building is bad, sure, but it's not going to do the type of focused damage that you can accomplish with controlled demolition. The impact damage and fires went all over the place in a haphazard fashion, it could not be focused on only the things that had to be destroyed in order for the building collapse... But demolition charges could be. So if a plane was able to destroy the building, it logically follows that a demolition crew could have done the same with incredibly little effort and resources. Specifically in this case, they would supposedly only have to cut enough trusses to start a cascade of the floors.

Now you can say I'm just being incredulous, but I'm unsure what proof or evidence has been presented that a collapse of the floors would also destroy the core in the manner that was observed. This has been asserted, sure, but I don't think NIST says anything about it in the FAQ at least. Btw, as you can see in the picture and in the earlier 3D model, the core columns were laterally braced between themselves. They were not spaghettis jutting out from the earth that had to be braced by the floors. I'm unsure what would happen to the core if it was just standing on its own, but I'm not buying that it would collapse in a matter of seconds.

 

[benthamitemetric]

Well, I'm just pointing out a necessary conclusion from what you believe about the collapse. You believe the building collapsed because a plane flew into it, and it did some impact damage, but mostly the building was done in by the fires that ensued. A plane flying into the building is bad, sure, but it's not going to do the type of focused damage that you can accomplish with controlled demolition. The impact damage and fires went all over the place in a haphazard fashion, it could not be focused on only the things that had to be destroyed in order for the building collapse... But demolition charges could be. So if a plane was able to destroy the building, it logically follows that a demolition crew could have done the same with incredibly little effort and resources. Specifically in this case, they would supposedly only have to cut enough trusses to start a cascade of the floors.

Now you can say I'm just being incredulous, but I'm unsure what proof or evidence has been presented that a collapse of the floors would also destroy the core in the manner that was observed. This has been asserted, sure, but I don't think NIST says anything about it in the FAQ at least. Btw, as you can see in the picture and in the earlier 3D model, the core columns were laterally braced between themselves. They were not spaghettis jutting out from the earth that had to be braced by the floors. I'm unsure what would happen to the core if it was just standing on its own, but I'm not buying that it would collapse in a matter of seconds.

So your argument now is that, while the floors would have collapsed all the way to the ground from the mass of top blocks that was set in motion by the initial collapses, the core columns would nonetheless have remained standing indefinitely unless they were demolished by some external force?

 

[econ41]

Isn't this the entire point of this thread though? The OP question is whether it would collapse JUST from the fire (if you could magic the fuel into the those floors) without the plane impact. I always assumed that the damage from the airliner was important as it caused beams to buckle and therefore the loads are not distributed as designed even before fire further weakened the structure.

Thank you. AND it was the specific reason I OPed the thread - to break the cycle of evasive answers derailng the previous threads by changing topics, "moving the goalposts", to avoid soundly presented arguments.

That said - at least the thread has seen some intensive debate despite a lot of the same circling evasions. And some members are still ignoring my often repeated advice to understand the mechanism of the Twin Towers collapses. Most of the points raised are easily resolved if the actual collapse mechanism is understood. Diversions into false analogies do not help.

And that actual collapse is what happened whether or not it was triggered by fire or by CD. Both "sides" should agree on the mechanism which, for the Twin Towers, is clearly understandable from the video record. It's not so easy for WTC7.

( I am also surpsrised as this is the first time I have heard anyone calculating a 707 at 600mph hitting the WTC. I have previously seen Robertson's calculations of 180mph and that is a HUGE difference)

And recognise that the towers both withstood the impact and initial damage. It was the resulting fires that caused the collapses. (OR fires helped by a bit of CD if ever a truther can prove CD. )

 

[econ41]

Has anyone mentioned the 500mph tsunami from the fuel tanks that washed away the insulation?
NCSTAR 1-2B

I deliberately left the factor out of my OP explanation because:
1) The topic is open to dispute by truthers looking to evade reasoned arguments - I was trying to reduce the opportunities for off topic evasions; AND
2) The four factors I did identify in the OP were sufficient to prove the initial point for debate.

I dont think it has been raised by other members. And most of the recent discussion has been off the OP topic and circling the usual partial understandings of the forensic aspect of structural analysis.

 

[econ41]

but I'm not buying that it would collapse in a matter of seconds.

It did. The problem is that you claim you cannot understand why AND you ignore posted explanations.

 

[Henkka]

So your argument now is that, while the floors would have collapsed all the way to the ground from the mass of top blocks that was set in motion by the initial collapses, the core columns would nonetheless have remained standing indefinitely unless they were demolished by some external force?

Indefinitely? I'm not sure. The core standing on its own would be incredibly slim, it would likely sway and possibly topple over or something. But would it collapse smoothly straight down, as seen in the Sauret footage? I don't see how that could happen. It should probably be noted the core was tied to the perimeter through the hat truss as well, not just the floors.

Also, your argument seems to be that the WTC towers could have been demolished all the way to the ground by the tiniest of explosives taking out some trusses, so I don't really agree with your implication here that I'm the one making unbelievable claims.

 

[benthamitemetric]

Indefinitely? I'm not sure. The core standing on its own would be incredibly slim, it would likely sway and possibly topple over or something. But would it collapse smoothly straight down, as seen in the Sauret footage? I don't see how that could happen. It should probably be noted the core was tied to the perimeter through the hat truss as well, not just the floors.

Also, your argument seems to be that the WTC towers could have been demolished all the way to the ground by the tiniest of explosives taking out some trusses, so I don't really agree with your implication here that I'm the one making unbelievable claims.

What do you mean the tiniest explosives? You are talking about destroying 120 significant and multifaceted connections per floor over the span of 3 or 4 floors (at least). How tiny of an explosive can do that in your fantasy?

 

[econ41]

So your argument now is that, while the floors would have collapsed all the way to the ground from the mass of top blocks that was set in motion by the initial collapses, the core columns would nonetheless have remained standing indefinitely unless they were demolished by some external force?

A bit of history of debate of that issue - I don't know if it has been discussed on Metabunk.

The process which, after some controversial history, is now described as "ROOSD" focussed initially on the shearing of the OOS floor joists from the perimeter columns. The debate at that time (2007 - 2009 and following) was responding to claims led by truther D Chandler that "sqibs" - small explosive charges - were used to shear off the joists from the perimeter. Hence the focus of my 2007 diagram on the joist to perimeter situation.

I subsequently extended the explanation into a "Three sub-processes" explanation of the Twin Towers progression stage collapse mechanism. That would be 2011 or 2012 - I referred to it in 2013 on another forum and long before I became aware of or joined Metabunk.

Those "three sub-processes" are:
(a) "ROOSD" Which sheared off the OOS floor joists allowing;
(b) the perimeter columns sheets to peel off, topple and break up without needing separation by explosive squibs; WHILST
(c) there was concurrent "Core Strip Down" as the process analogous to ROOSD sheared off the floor beams in the core area. The "spires" left standing are proof of that process.

We could benefit from an agreed outline expansion of the four stages of the Twin Towers collapse mechanisms. It could save a lot of this persistent recycling of basics. Especially when the main features of collapse should be agreed upon by both sides of the CD or No CD "argument". Those main features of the Twin Towers collapse are undeniable from the video record. Or, to be more pedantic, they cannot be validly denied.

 

[Henkka]

What do you mean the tiniest explosives? You are talking about destroying 120 significant and multifaceted connections per floor over the span of 3 or 4 floors (at least). How tiny of an explosive can do that in your fantasy?

Well, I just mean replicating the minimum required lethal damage you believe the buildings suffered, but with targeted explosives. If a plane impact and fires can destroy the South Tower in a mere 56 minutes, it should be trivial to replicate the damage with demolition charges. That's because in a fire, a lot of the energy is wasted on heating up things that weren't necessary for the building to collapse. With explosives, you can focus all the energy to do the bare minimum required to trigger the collapse. You can't say that it would take tons and tons of large explosives, if you believe the same thing was accomplished by a fire.

 

[benthamitemetric]

Well, I just mean replicating the minimum required lethal damage you believe the buildings suffered, but with targeted explosives. If a plane impact and fires can destroy the South Tower in a mere 56 minutes, it should be trivial to replicate the damage with demolition charges. That's because in a fire, a lot of the energy is wasted on heating up things that weren't necessary for the building to collapse. With explosives, you can focus all the energy to do the bare minimum required to trigger the collapse. You can't say that it would take tons and tons of large explosives, if you believe the same thing was accomplished by a fire.

Newsflash: Someone who puts explosives in the right places could cause a building to fail. Obviously someone could use their brain + explosives to concentrate destructive energy in critical places, whereas an unthinking fire could not. As we've said from the outset of this thread, it is difficult to imagine how a fire significant enough to cause a collapse could occur without additional fuel such as from a plane or missile strike and extreme circumstances (such as burning on at least 3 floors at once), but it is of course theoretically possible. Just as it is theoretically possible to destroy the building in an infinite number of other ways. What point are you trying to make?

 

[econ41]

It should probably be noted the core was tied to the perimeter through the hat truss as well, not just the floors.

??? You are referring to the later stages of collapse. The Top Block was disconnected from the lower tower by Stage #1 - the "initiation stage" AND the same Top Block was demolished during Stage #3 = the stage of "early progression" Both long before the later 4th stage of "established progression" you are refering to.

Also, your argument seems to be that the WTC towers could have been demolished all the way to the ground by the tiniest of explosives taking out some trusses, so I don't really agree with your implication here that I'm the one making unbelievable claims.

There is a David Chandler video circa 2009 origin which he uses to support claims for "squibs". It may have been withdrawn because it actually self-rebuts. I'll see if I can locate it. The reality of course is that there was no need for explosives in the progression stage. That is true independent of any claim for CD in triggering the initiation stage of collapse.

 

[econ41]

Well, I just mean replicating the minimum required lethal damage you believe the buildings suffered, but with targeted explosives. If a plane impact and fires can destroy the South Tower in a mere 56 minutes, it should be trivial to replicate the damage with demolition charges.

Of course causing collapse by explosives is trivial. It was one of my first thought challenge exercises when, in 2007, I first joined the online debate of WTC collapses. (I am trained as a military engineer.) Simply load masses of explosives against the basement level columns. Lots of them. BUT it won't mimic the actual collapse(s).

"replicating the damage" i.e. mimicking the actual collapses is a more challenging task. I have proposed hypotheses - twice back about 2009 or 2010. Two old-style genuine honest truthers were trying to formulate a valid pro CD hypothesis. I offered to help. Two separate interactions about a year apart. The goal was to cause the collapse mechanism actually observed on 9/11 but by using CD. Preferably without leaving evidence behind. A fun exercise on each occasion. I may be the only Military Engineer debunker who has posted an hypothesis for CD of the Twin Towers.

That's because in a fire, a lot of the energy is wasted on heating up things that weren't necessary for the building to collapse. With explosives, you can focus all the energy to do the bare minimum required to trigger the collapse. You can't say that it would take tons and tons of large explosives, if you believe the same thing was accomplished by a fire.

it is good to see you starting to think through the challenges. Remember my advice to understand the mechanism?? And, since you are attempting to prove that it was plausible for the 9/11 collapses to be triggered by CD you MUST mimic those actual mechanisms.

Have you identified where the key components for your CD hypothesis are? HINT - consider the trigger event of the NIST hypothesis. THEN work out how you marry the collaboration between fire damage and explosive help.

 

[Henkka]

Newsflash: Someone who puts explosives in the right places could cause a building to fail. Obviously someone could use their brain + explosives to concentrate destructive energy in critical places, whereas an unthinking fire could not. But the fire isn't destroying the building by magic--it is burning a significant amount of fuel to create a significant amount of heat. As we've said from the outset of this thread, it is difficult to imagine how a fire significant enough to cause a collapse could occur without additional fuel such as from a plane or missile strike and extreme circumstances (such as burning on at least 3 floors at once), but it is of course theoretically possible. What point are you trying to make?

I'm attempting to do a kind of "reductio ad absurdum" type argument. It seems absurd that the WTC towers could be reduced to a smouldering pile of rubble in a few seconds, by a relatively tiny amount of explosives directly targeting the floor trusses on a few floors. But it follows logically from thinking that a plane hitting the building did the same thing. What one finds absurd is subjective though, so it's more like something to think about than some kind of QED argument.

 

[Henkka]

"replicating the damage" i.e. mimicking the actual collapses is a more challenging task.

Why would it be challenging? Just use explosives to do the same amount of damage you believe the plane impact and fires did. Or I mean, do only the amount of damage that was necessary to collapse the building. How much explosives would you need?

 

[econ41]

Why would it be challenging? Just use explosives to do the same amount of damage you believe the plane impact and fires did. Or I mean, do only the amount of damage that was necessary to collapse the building. How much explosives would you need?

OK. So OP the thread making that claim and let's see if you and I can work through the reasoning.

 

[benthamitemetric]

I'm attempting to do a kind of "reductio ad absurdum" type argument. It seems absurd that the WTC towers could be reduced to a smouldering pile of rubble in a few seconds, by a relatively tiny amount of explosives directly targeting the floor trusses on a few floors. But it follows logically from thinking that a plane hitting the building did the same thing. What one finds absurd is subjective though, so it's more like something to think about than some kind of QED argument.

Do you understand that floor truss connection failures were not the reason for the initiation of the the fire induced collapse that followed the plane impacts? It seems like you do not, even though I pointed it out just a few posts ago. And that's probably why you are fixated on what it would take to destroy the truss connections. Note that I never said it would be easy to destroy a sufficient number of trusses to induce a collapse, but it is of course theoretically possible. As I said, you are likely looking at destroying 3-4 floors worth of truss connections, which is 120 connections per floor. Maybe if you took half as much time to read the NIST reports and understand the structure of the building as you do to post here, you could come up with an even more efficient way to induce a collapse with explosives. In any case, it's not going to be easy to do so in any meaningful sense. Just ask Ramzi Yousef. And none of this has anything to do with the collapse that actually occurred.

 

[deirdre]

And some members are still ignoring my often repeated advice to understand the mechanism of the Twin Towers collapses. Most of the points raised are easily resolved if the actual collapse mechanism is understood. Diversions into false analogies do not help.

if we understood what you are talking about, we wouldn't need you to remind us to understand what you are talking about.

 

[econ41]

It seems absurd that the WTC towers could be reduced to a smouldering pile of rubble in a few seconds, by a relatively tiny amount of explosives directly targeting the floor trusses on a few floors.

You need to drop the Top Block first.

But it follows logically from thinking that a plane hitting the building did the same thing. What one finds absurd is subjective though, so it's more like something to think about than some kind of QED argument.

The plane did not "target the floor trusses on a few floors. It started humongous fires which....

1) Triggered the failure of a few columns >> starting a "cascading sequence" of column failures which >> caused load redistribution >> which overloaded more columns >> until not enough left to support the Top Block Top Block dropped << THAT is Stage #1 - "Initiation" AND if you want to use explosives in the real event or in a collapse that looks like the real event you MUST cause that cascading failure.

THEN

2) Transition stage as the Top Blocks started tilting and dropping with the bottom ends of broken columns missing the lower tower columns and falling onto floors - setting the scene for "ROOSD"


3) Progressive collapse starts- early progression saw the Top Block and the upper levels of the lower tower in mutual destruction - look again at that graphic - the two yellow arrows show where the falling top block perimeter (left side) would dismantle the top of upper tower. Same thing in reverse on the right side - dismantling the Top Block from the bottom going "upwards".

THEN

4) Established ROOSD. Top Block demolished into debris and the debris falling down the OOS missing the columns.



If you still think explosives are needed to shear off the floor joists they need to be at the point labelled "It Fails Here".

AND that stage is far too late to have any effect in causing the initiation storage with Top Block starting to fall.

 

[deirdre]

The plane did not "target the floor trusses on a few floors. It started humongous fires which....

aw i just had found an article i thought spelled it all out nicely, but then you spelled it out nicely.

you should save that post to repost often as it's one of the most clear things you've ever written.

but i do still like one line in my link so ill quote it

Article:

The World Trade Center was not defectively designed. No designer of the WTC anticipated, nor should have anticipated, a 90,000 L Molotov cocktail on one of the building floors.

Source: https://www.tms.org/pubs/journals/jom/0112/eagar/eagar-0112.html

i also like the article uses the word redundant alot... something Henkka seems to not know ex:

Article:

The egg-crate construction made a redundant structure (i.e., if one or two columns were lost, the loads would shift into adjacent columns and the building would remain standing). Prior to the World Trade Center with its lightweight perimeter tube design, most tall buildings contained huge columns on 5 m centers and contained massive amounts of masonry carrying some of the structural load. The WTC was primarily a lightweight steel structure; however, its 244 perimeter columns made it “one of the most redundant and one of the most resilient” skyscrapers.1

Source: https://www.tms.org/pubs/journals/jom/0112/eagar/eagar-0112.html

 

[econ41]

aw i just had found an article i thought spelled it all out nicely, but then you spelled it out nicely.

you should save that post to repost often as it's one of the most clear things you've ever written.

Thanks - I can do it if I try.

but i do still like one line in my link so ill quote it

Article:

The World Trade Center was not defectively designed. No designer of the WTC anticipated, nor should have anticipated, a 90,000 L Molotov cocktail on one of the building floors.

Source: https://www.tms.org/pubs/journals/jom/0112/eagar/eagar-0112.html

Any building has to be designed to resist possible and predictable traumatic events. What hit the Twin Towers was way beyond what they were designed for.

i also like the article uses the word redundant alot... something Henkka seems to not know ex:

Article:

The egg-crate construction made a redundant structure (i.e., if one or two columns were lost, the loads would shift into adjacent columns and the building would remain standing). Prior to the World Trade Center with its lightweight perimeter tube design, most tall buildings contained huge columns on 5 m centers and contained massive amounts of masonry carrying some of the structural load. The WTC was primarily a lightweight steel structure; however, its 244 perimeter columns made it “one of the most redundant and one of the most resilient” skyscrapers.1

Source: https://www.tms.org/pubs/journals/jom/0112/eagar/eagar-0112.html

Yes. redundancy was a big part of the reason why it took a cascading failure with load redistribution to start the collapse.. It took me a couple of years involvement in these discussions before I got my head around the initiation stage.

 

[Abdullah]

Why are we talking about pancaking??

Consider the case of a 5 storey exterior column heated.
-At 100°C restrained expansion causes a stress increase of 200MPa.
-At 200°C 500MPa increase and the colum starrs buckling..
-At 300°C the buckling has localized on one floor where the interstorry displacement exceeds 2inches, and the stress has dropped to the initial value.
From NCSTAR 1-6C

 

[Thomas B]

(And, by the way, if the towers were only 8 stories tall, as in your construction photo, I'm sure the core columns would have be fine without the lateral support from the floor system, as they are in the photo. But you are missing 100+ floors. Think about it.)

This is where math would be useful. We had an interesting work session on another thread trying to work out the self-buckling height for a core column. (Start with @Jeffrey Orling's very useful illustration in post #181 of "WTC Collapse Using Unity/Besiege".)

At one point (post #195) I arrived at an estimate of about 115 meters or about 35 stories. That's for a single column (and one that was somewhat weaker than the strongest core columns at the bottom of the towers). Also it wasn't tapered. So I take it as a very safe lower bound.

That's a single, free-standing column.

Putting together 47 columns in a structural system with mutual lateral bracing would seem to easily let us buid 4 times higher than that. It seems to confirm the engineer (Leslie Robertson?) in the video @Henkka linked to. He described the perimeter as a "box":



Like I say, it's a math problem. If you want to get beyond "incredulity" we really just have to do the math for the core. And again for the perimeter. Both without the lateral support of the floors. The thing I want to point out is that both of these structures are built by connecting the columns laterally within each system: spandrel beams in the perimeter and (apparently) traditional beams in the core. If a single column could stand on its own up to some height, a square formation of some number of them, internally braced every 3 meters or so, could stand much higher. The question is what those heights are.

I'm going to keep working on it.

 

[econ41]

Why are we talking about pancaking??

"We" are not talking about it BUT @Henkka made a legitimate reference a couple of posts back. There are no other references to "pancaking" in the thread.

@Henkka's reference was legitimate in that he used it in the context of the "progression" stage - where the dominating process was "ROOSD" but can be legitimately described as "pancaking". However the term "pancaking" has historically caused confusion so IMO it is best not used.

HOWEVER your topic refers to the "initiation stage" of the Twin Towers collapses. We are not discussing that stage in these recent posts - the last few pages of discuission.

Consider the case of a 5 storey exterior column heated.
-At 100°C restrained expansion causes a stress increase of 200MPa.
-At 200°C 500MPa increase and the colum starrs buckling..
-At 300°C the buckling has localized on one floor where the interstorry displacement exceeds 2inches, and the stress has dropped to the initial value.
From NCSTAR 1-6C

What are you trying to say or ask? And is it on the OP topic or relevant to recent discussions.

 

[econ41]

Well, I'm just pointing out a necessary conclusion from what you believe about the collapse. You believe the building collapsed because a plane flew into it, and it did some impact damage,

Yes. Yes

but mostly the building was done in by the fires that ensued.

Yes - the fires caused the collapse(s) by the mechanisms that have been explained. Many times.

A plane flying into the building is bad, sure, but it's not going to do the type of focused damage that you can accomplish with controlled demolition.

It simply focuses differently. Like the first columns to fail were probably the ones which caused the inward bowing of the perimeter. Just where the fire's effects were focused. And, yes, the fires were not sufficiently intelligent to focus their heat where a demolition person would focus. The fires still achieved the objective. Clearly fires need more training to think like terrorists or inside jobbers. (<< That is a joke! )

The impact damage and fires went all over the place in a haphazard fashion, it could not be focused on only the things that had to be destroyed in order for the building collapse...

The fire damage was focused in the way that caused collapse. Why do you refuse to understand the collapse mechanism? It would make understanding a lot easier and clearer.

But demolition charges could be. So if a plane was able to destroy the building, it logically follows that a demolition crew could have done the same with incredibly little effort and resources.

Of course and especially with 20/20 hindsight. Remember nobody on 9/11 had hindsight. Without the benefit of hindsight I, as a Military Engieer, would not even have attempted demolition from top down. But with hind sight I was able to help a couple of truthers formulate a couple of hypotheses. Many years ago.

Specifically in this case, they would supposedly only have to cut enough trusses to start a cascade of the floors.

WRONG. Unless you cause the Top Block to drop there is no mechanism to start the failure of floors.

Now you can say I'm just being incredulous, but I'm unsure what proof or evidence has been presented that a collapse of the floors would also destroy the core in the manner that was observed.

Again - if you want reasoned explanations leading to proof - OP the thread and I will provide it.

This has been asserted, sure, but I don't think NIST says anything about it in the FAQ at least.

Well we are not discussing the shortcomings of NIST's explanations. I dont even accept that NIST's decision to not explain progression was wrong. BUT WE are discussing what actually happened. NOT whether or not NIST was right. So, if you dont understand why the core would ROOSD - OP the thread and make the claim.

Btw, as you can see in the picture and in the earlier 3D model, the core columns were laterally braced between themselves. They were not spaghettis jutting out from the earth that had to be braced by the floors.

Yes. Known and should be agreed facts.

I'm unsure what would happen to the core if it was just standing on its own, but I'm not buying that it would collapse in a matter of seconds.

"We" (or at least "I") understand both. Why don't you want to move forward and learn? The ball is in your court.

 

[Henkka]

Like I say, it's a math problem. If you want to get beyond "incredulity" we really just have to do the math for the core. And again for the perimeter. Both without the lateral support of the floors. The thing I want to point out is that both of these structures are built by connecting the columns laterally within each system: spandrel beams in the perimeter and (apparently) traditional beams in the core. If a single column could stand on its own up to some height, a square formation of some number of them, internally braced every 3 meters or so, could stand much higher. The question is what those heights are.

I'm going to keep working on it.

This might be totally off, but could the core be basically modelled as a single, giant column? Like I could understand why the entire core might buckle or topple over if it stood on its own, but I don't understand how any of the individual 47 columns could buckle independently, since they were laterally braced between each other.

We could also think about the first second or two of the collapse, where let's say 10% of the floors at the top have failed and are bearing down on the rest. But at this point, the core would still be laterally supported at 90% of its length. So why would the antenna start moving down already, since it's sitting on the hat truss, which is sitting on the core columns?

 

[econ41]

.... I don't understand how any of the individual 47 columns could buckle independently, ....

They didn't. have you not seen the pictures of the "spires"? I've already offered to discuss core failure with you is you OIP a thread.

since they were laterally braced between each other.

We could also think about the first second or two of the collapse, where let's say 10% of the floors at the top have failed and are bearing down on the rest. But at this point, the core would still be laterally supported at 90% of its length. So why would the antenna start moving down already, since it's sitting on the hat truss, which is sitting on the core columns?

You are confusing and conflating the first stage - "Initiation" with the fourth stage "established progression".

You should know what my next comment will be...

 

[econ41]

So why would the antenna start moving down already, since it's sitting on the hat truss, which is sitting on the core columns?

The antenna movement occurred in the first stage - "initiation" which DISCONNECTED the top block from the lower tower. So "antenna moment" is irrelevant to core column failure in the "lower tower" which is Stage 3 and 4.

And you should know what my next comment will be...

 

[Henkka]

Of course and especially with 20/20 hindsight. Remember nobody on 9/11 had hindsight. Without the benefit of hindsight I, as a Military Engieer, would not even have attempted demolition from top down. But with hind sight I was able to help a couple of truthers formulate a couple of hypotheses. Many years ago.

The only point of the argument is whether or not it's absurd that the WTC towers could be destroyed by relatively few explosives that would replicate the impact and fire damage. Like when you ask truthers, they think much of the core was laced with nanothermite charges or whatever, along with other incendiaries used to pre-weaken the structure. Now whether or not that's realistic, you can understand that if you did that, the building would surely be destroyed. But according to the official theory, all that nanothermite stuff would be completely unnecessary, you would only need to put a few explosives on the impacted floors to replicate whatever lethal damage you believe the plane did. And btw, when I say "few", I'm more so talking of the energy contained in these explosives, not the literal number of individual charges. Maybe cutting all the trusses would take hundreds of charges, but you wouldn't need that much explosive material in each charge, since the trusses were pretty flimsy.

The antenna movement occurred in the first stage - "initiation" which DISCONNECTED the top block from the lower tower. So "antenna moment" is irrelevant to core column failure in the "lower tower" which is Stage 3 and 4.

I guess I'm struggling with what is causing the top block of the core to be disconnected from what's below it.

 

[econ41]

The only point of the argument is whether or not it's absurd that the WTC towers could be destroyed by relatively few explosives that would replicate the impact and fire damage.

A good point. I've already offered to discuss it if you OP the thread (and "tag" me.)

Like when you ask truthers, they think much of the core was laced with nanothermite charges or whatever, along with other incendiaries used to pre-weaken the structure. Now whether or not that's realistic, you can understand that if you did that, the building would surely be destroyed. But according to the official theory, all that nanothermite stuff would be completely unnecessary,

Remember no truther has ever explained how collapse could be cause by explosives AND mimic the actual 9/11 collapse.

you would only need to put a few explosives on the impacted floors to replicate whatever lethal damage you believe the plane did. And btw, when I say "few", I'm more so talking of the energy contained in these explosives, not the literal number of individual charges.

Understood and agreed. Remember I think I'm the only "debunker" (sceptic actually) who has ever attempted to show how CD could be performed.

Maybe cutting all the trusses would take hundreds of charges, but you wouldn't need that much explosive material in each charge, since the trusses were pretty flimsy.

Agreed on the flimsiness and the minimal size of the needed charge. But take care - you are still not separating the "stages" of collapse.

I guess I'm struggling with what is causing the top block of the core to be disconnected from what's below it.

Understood. It's not a simple topic BUT the clues are in this clip I've posted many times. At the time the clip shows all direct structural connections of Top Block To Lower Tower were disconnected.


It is the worst case of the four pairs of views BUT the situation with the other three was similar - Top End columns missing Botton Ends. The difference with the other three pairs is that the columns are missed by a smaller distance. But they still missed/

 

[Henkka]

It is the worst case of the four pairs of views BUT the situation with the other three was similar - Top End columns missing Botton Ends. The difference with the other three pairs is that the columns are missed by a smaller distance. But they still missed/

I can understand that the columns missing would cause a far worse collapse than if they hit head-on. But you need to get the columns disconnected and moving in the first place, so the missing can take place, no?

 

[Thomas B]

This might be totally off, but could the core be basically modelled as a single, giant column?

I've had the same thought. Imagine using the steel to make a single round, hollow mast with 2-foot thick walls and a 32-foot radius. That's just scaling up the text-book example I referred to in a post on another thread, in a way that approximates the WTC proportions. (The cores were 87 feet on the narrow side and the columns at the base were almost solid steel blocks 22"x52".)

Source: https://ocw.mit.edu/courses/2-080j-structural-mechanics-fall-2013/resources/mit2_080jf13_lecture10/

Note the walls in the example are a tenth of an inch, so more than 200 hundred times thinner than the walls in the one-column core we're imagining. I'll get to work on the math later today, but if anyone beats me to it, that's just a good thing.

 

[econ41]

But you need to get the columns disconnected and moving in the first place, so the missing can take place, no?

Yes, And, surprisingly, that is the key issue that few people have looked at or considered seriously.