For a few months, I have collected the opinion of laypeople and self-proclaimed experts on the cause for the demise of the WTC Twin Towers.
I am sharing them, seemingly without context, because I am preparing to make an argument; in a sense, this is a strategic post and only part of the foundation of the #towerchallenge architecture that will be built upon it. The next post will introduce the #towerchallenge itself (if you want to spoil your surprise, take a sneak peek @ /r/towerchallenge).
Most obviously, this one serves to dispel the notion that there is wide agreement, consensus and understanding on the cause(s) of the "collapses".
Previously,
- The scientific consensus on the cause of total progressive collapse
has shown, by aggregating most notable and official expert opinion on the topic, that another common myth, namely, that all experts agree on the basic, underlying principle, and that the science is clear on this issue, is simply objectively false.
In my personal view the most interesting take-away however is that "Jet fuel can't melt steel beams" is not merely a "dank meme", or even the rebuttal to a strawman argument: actually, multiple experts, among them Matthys Levi (Why Buildings Fall Down) and Prof. Astaneh-Asl even, initially did claim in the first days and as late as five years later that the Twins fell because the jet fuel melted the steel! - An (incomplete) list of building collapses and demolitions
compares many modes of failure of mid- to large-sized structures - showing that slender things tend to fall over, that natural collapses are assymmetrical, that the center of mass usually moves sideways, that the progression of the collapse front usually decelerates in gravitational collapses and how buildings behave in different types of demolition methods. Particularly the botched demolitions attempts demonstrate that square-cube law - IOW, their sheer size - is no explanation for the behaviour of the Twin Towers: not only small Jenga towers, but also big things tend to damp, cushion and eventually arrest collapse.
The following quotes will go without much comment. Please note, however,
- attempts to explain why there is no experimental model demonstrating the alleged principle behind the gravity-collapse
- appeals to authority
- appeals to complexity (big bang, black holes)
- speculation that that is how steel skyscrapers are purposefully built by genius engineers to mitigate the risk of horizontal domino chain reactions
- speculation that that is how steel skyscrapers automatically turn out, simply by virtue of being so tall.
Structural engineer here. Some brief points for anyone that cares: steel doesn't need to melt to cause a failure. Elevated temperatures slowly reduce the strength of the steel as they continue to rise. Somewhere around 1000 degrees F you are looking at nearly a 50% strength reduction. Also, while jet fuel doesn't burn higher than 1500 degrees F, there was plenty of other combustible material in the building that would have caused temperatures to exceed 1500 degrees F. Once you get up in that range you are approaching a 90% reduction in strength.
"The 'explosions' are not isolated and few, they are continuous and widespread. They move progressively down the faces of the building, keeping pace with falling debris. Perhaps you can imagine a natural cause, but I can't."
That's because you're an idiot.
When those floors were collapsing onto each other, where do you think the ejections would go? It's like... put some peanut butter or pudding into your hand, then squeeze it into a tight fist. It's really that simple.
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Structural steel and reinforced concrete are like pudding? That's a new one. Are you, by chance, a structural engineer?
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The mass being eating by a black hole isn't like pudding either, and yet, we see the same effect.
Give me a fuckin' break, man. Are you incapable of conceptualizing?
In some sense, the buildings were mostly air, just thin frameworks of steel. Not too surprising that they collapsed straight down. And 99% or more of experts (in universities, construction companies, insurance companies, govts all over the world) seem to find little surprising about it. Only a small fringe is disagreeing.
No tower the size of the WTC had ever been collapsed in human history. The fact that a few things happened that seem to be anomalous is actually to be expected.
The physics of a building that size collapsing on itself are complex and don't yield well to an "everyday understanding" of what's "supposed to happen".
I can't comprehend how people seriously think there was any chance of the collapse stopping at all once it had started.
Gravity.
My favourite simple explanation is from Nutty 9/11 Physics.
Basically if you assume the top section of the building essentially fell one floor then the floor immediately below that would have had to resist a force of around 8g to stop the collapse. That means in the South Tower that it would have needed to support the weight of about 200-floors of the tower, in the North Tower it would have been equivalent to the weight of about 80-floors.
Of course it can't support that load, so it fails, the falling mass continues, accelerating further to be exerting even more force on the next level. And so on. It was never going to stop.
It seems so very simple.
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Yeah, I'm incredibly confused by the idea that a falling object, including collapsing buildings, can decelerate. Gravity just starts to misbehave or something? I just can't follow the whacky logic, and I try, because I love conspiracy theories.
But 9.8 m/s² !!!
WTC was constructed to collapse downward rather than topple over. In that sense it was planned, but just because it's a huge liability to have a downtown full of potential dominoes knocking each other down.
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Sure, all-star brainiacs deploy that degree of forethought. Safer cars crumple to absorb impact, etc... but I would think that anti-domino safety for any skyscraper comes for free if you can get the thing to stand up in the first place.
My (admittedly gorilla level) understanding of how the buildings collapsed is that it happened more or less in 3 stages. The descending load from above caused the connections holding the floor trusses to fail first, one floor after the other all the way to the ground.
While this was happening, the pre-fabricated perimeter panels peeled away from the structure in large pieces when they lost lateral bracing, like peeling a banana.
The core held up the longest (standing 10 or 15 seconds after the floors finished falling), but eventually failed from being unbraced and heavily battered.
Once the internal supports were gone, there was little to no resistance,
Exactly that is the point, though. There is supposed to be lots of resistance, namely that of the structure keeping all the weight UP against the acceleration of gravity.
And if there isn't, the building falls down....which is exactly the situation being discussed. the building fell down because the 'resistance' (oooh, technical jargon!) keeping it up was gone.
Also truthers always insist that building never collapse on themselves unless it's a controlled demo, obviously they've never heard of the collapse of the Lian Yak building in Singapore.
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Or the sampoong department store. Which in actuality was a conspiracy, a conspiracy to save money on construction costs, and to avoid having to deal with pesky building codes, approvals and safey checks.
Heck, the aftermath of the disaster revealed that there had been massive ammounts of corruption in the korean building industry during the economic boom of the 80s and 90s.
Comparing a steel framed high rise to a spring is dumber than dogshit. Just saying...
The irony that is it's even explained in the movie "Loose Change", it's just that the filmmaker is too stupid to understand basic physics and construction engineering.
The first time someone tried to show me that movie, I had no idea what it was and remarked how the design (which is explained towards the beginning of the movie) was brilliant, as it's what allowed the towers to fall as they did. That's when I learned just how willfully stupid conspiracy theorists can actually be.
Fire needs three things: Heat, fuel and oxygen. We all learned this at school.
Why is the concept of burning jet fuel (and office equipment/supplies etc fueled by the 60/70/80MPH winds that will be found that high up) creating temperatures that would be hot enough to structurally weaken steel that has many hundreds of tons of weight on it such a hard one for some people to grasp?
You can melt many metal in a home made furnace with little more than a couple of cans and a hair drier.
I don't know why more people don't get this. When you crash a freaking plane into the building, its going to break/highly weaken the support beams.
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I don't get this either. What would the point if explosives even be? The buildings are destroyed, why bother blowing then up when they'll just be eaten away by the fire and structural damage? For that matter, why bother going further than just hitting it with planes? If they wanna pin terrorists on it, isn't that enough? Why complicate it with planes AND explosives?
The twin towers were explicitly designed to fail exactly like they did on 9/11 after a prolonged fire. The original architects have mentioned this fact. Heated long enough and hot enough structural steel will fail. The twin towers were designed so that the floors would fall vertically pancake style over the concrete / elevator shaft core. They did not want what were the tallest buildings in the wod falling sideways. They were explicitly built to fail the way they did. To stand as long as possible for evacuation then collapse in a controlled manner if a fire could not be controlled.
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This. This is exactly what I was looking for. I have heard so many times that the way they fell meant it must have been controlled demolition. what you said makes perfect sense too.
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In essence, that is a controlled demolition. In the sense that the building was designed to fall like that if the fire was uncontrollable.
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Can you source this? Primarily for my own use against conspiracy theories.
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Every doc about the towers collapsing. You are wasting your time trying to convince a person with any kind of conspiracy theory. The facts are out there they just refuse to believe anything that goes against what they have already decided happened.
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Holy shit I never knew that. I mean, I didn't buy into any conspiracy theories, but I did think it was a giant coincidence that such tall buildings would fall straight down on themselves like that. It makes perfect sense though. Of course the architects would account for this, in such a densely packed building area... thanks!
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Np, same with the John Hancock building. If that were to fall it would dome straight down.
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I don't have a source, but any documentary on the building of the towers, even pre 9/11 explains the way the structure was built. The main structure is the exterior. That's why it isn't an all glass exterior like many other buildings. The interior had only the stairwells and elevator shafts. This allowed for the floors to be made with trusses and have open floor plans with no columns.
The collapse happened because the exterior main structure was damaged, and the stairs/elevator in center was destroyed. As the fire raged, and as a former professional aviation refueled I can confirm that jet fuel can't melt steel IN THE OPEN AIR. In a confined space trapping the heat it will definitely soften steel though. I am now an aircraft mechanic, and the turbine blades in a jet engine cannot be made of steel because they will soften, deform, and destroy the engine. The heat softened the floors and exterior structure. Without a center support the floors started collapsing, putting further strain on the exterior structure. Finally the point was reached that the exterior buckled. Now here is why the exterior structure is important to know. Below the fire it was still full strength. When the collapse started it fell into the bottom, where the exterior contained it from tipping over. The interior was quite weak, not meant to hold the weight of the building, and the stairs/elevator column was crushed. A domino effect began as all the weight of everything above fell through the floors below, while the exterior contained it inside. As the floors tore away and blew outwards, there was nothing left to support the exterior beams and they were shredded away. This explains why you saw so much of the exterior "intact" in the rubble. The explosions heard was all the air in the floors below blowing out the windows. When the collapse first started it was slow, so the first few floors to be blown out could be differentiated from all the other commotion going on and could easily be mistaken for explosives detonating.
I am measly an aircraft mechanic with only a year of engineering school and I figured this all out just be seeing old documentaries on how the towers were built. I have no idea how a group comprised of architects and engineers could delude themselves of the truth that aircraft alone took down the towers.
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The twin towers were vulnerable. Their structure wasn't a traditional 3d grid of beams, but instead a load-bearing shell and a load-bearing core. Connecting the shell to the core were open web steel joists (the things you see in the ceiling of a big-box store). It doesn't take much heat to weaken the joist webbing.
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In researching for a thesis paper on structural design, I came across several papers regarding the construction of the World Trade Center twin towers.
What \u_____ is saying is supported the two following articles. One written by Zdeněk Bažant, a civil engineering and material science professor at Northwestern University. Bažant This paper describes the collapse of the building to be inevitable once the exterior supports to the building were severely damaged. Without the load bearing exterior walls, the stress of the upper floors transferred or to the interior elevator shaft. Along with the weakening of the steel beams, the added stress proved to be too much for the supports to handle. After the initial drop of the upper floors, the building began what Bažant describes as a perpetual collapse.1 The impulse of the upper floors falling the distance of a single floor was enough to cause the subsequent floors to buckle one after the other.
The second paper, by Thomas W. Eagar and Christopher Musso, Eagar2 supports the research of Bažant and the comments above. Specifically, the authors discuss the impact of even relatively low heat fires on the strength of load bearing steel.
There are many more reasons for the collapse, including the weakness to the trusses holding the walls of the building together. When the trusses in the floors holding the exterior walls are removed, the effectiveness of the walls to bear loads is diminished. Flint There is a lot of maths to this. Enjoy.
I've seen other comments regarding quotes from the builders stating that they designed the building was designed to collapse in this manner. I can neither confirm or deny this statement. I remember watching an interview with the designer of the towers in which he stated that never foresaw an event like this occurring. However, if I were to guess, I would go as far to say that no builder designs a building such that it would collapse sideways in the state of a disaster. The method of construction found in the twin towers is similar to that of buildings found in earthquake prone areas of the world, see the Patronas Towers in Kuala Lumpur. The load bearing design of these two buildings is remarkably similar to the twin towers, despite their differing aesthetics.
Again, I'm by no means an expert... so don't go quoting me. I hope this helped though.
- Bažant wrote a separate article on this in 2007, if my memory serves me right.
- I know, this article looks super sketchy. The first time I read it, it was in a legitimate journal, this is the copy that I was able to find on google.
... thank goodness for google
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The buildings you helped design incur the worst terrorist attack in human history, but failed and collapsed in the safe way that it was intended to. How would you feel as that architect? I'd imagine mostly horror and grief at the event, then afterwards look back and feel a slight twinge of relief/pleasure that it did what it should've done? I can't describe it.
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Another fun fact: Many engineers theorize that the concrete used in the building, based on common materials at the time of construction, had explosive elements. They weren't necessarily intentional, just a defect with the concrete used. this is why when the fire heated them and they fell it pulverized the concrete. It happened from the inside out.
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Structural engineer here.
The amount of effort it would take to control this would be incredible. Keep in mind, that I am in no way an expert in fire engineering, but I think I understand what kind of concepts are involved.
If you knew what grade steel was used for all of the elements, carefully chose member sizes, and had a lot of test data on your fasteners, I could see a way to control the succession of failure in your system. It would be tedious, but theoretically possible.
And from what I've learned of my field, if I kinda sorta get it, then there's somebody out there that knows how to do it well.
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The engineers behind the Twin Towers construction may have been miserable or in shock like the rest of the world when they collapsed, but they should harbour some pride at this fact.
Their designs worked. Perfectly. And the careful design and implementation of this safety feature saved many lives.
How would you explain the collapse of WTC-7?
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How would explain dark matter? It's not explainable. Making up a ridiculous explanation isn't useful. It's possible part of a building fell on it and it collapsed. It is much much much much less possible that a massive government conspiracy put demolitions in it. It's much more likely that it collapsed unintentionally. That's about all you can say. There is nothing wrong with uncertainty.
Any structural/material engineer worth their salt can explain and counter every point they make. Steel loses its structural integrity (up to 70% loss) within less than half of its melting temp. Combine that with the impact of a 400 ton plane (live load it wasn't supposed to take) and the fact it smouldered for almost four hours before going down, there's no conspiracy.
My 'feeling' of it not sounding correct is my way of saying without overstepping into fields I am not qualified in, that-from what I have read and seen there are a lot of inconsistencies and unknowns that could change what we know about the event. I yield that it completely possible that the event was solely and originally caused by the planes, but maintain that it is also possible that there were other circumstances that made the buildings' downfalls more easy.
From explosives, to construction flaws, either or even something else could have contributed or been the main reason for their collapse and their said collapse could have still looked the same.
Stupid little experiments prove nothing at all.
Buckled columns offer very little resistance. You don't need a model to know that.
How would you build a model of the towers (or a section of) to investigate the collapse mechanism?
A simple model is what a floor can hold. A simple model we can do in our heads. A floor of the WTC can hold 11 more floors of debris, and the 12th floor of debris results in instant failure, then there are 12+i, and the mass grows. This simple momentum model gives a collapse time of 12.08 seconds. A model for collapse that matches close the initial collapse, based on momentum of what happened on 911. As an engineer, this is a simple model matches the collapse front exactly until you can't see due to dust. Anyone can take excel and model the WTC with momentum to get these results - and it matches the official collapse theory, NO, it matches what happened. In my story of 911 there is no official theory, I have the video which show the official reality, a gravity collapse due to fire. And we find that CD uses gravity as the primary energy source for collapse in CD, E=mgh is the majority source of energy used to destroy building in CD. Thus, CD looks like gravity collapse
you do realize engineers don't use 'physical models' when building. They don't "build a bridge" to prove whether they can build a bridge.
They use mathematics and known physics stuff. And they can calculate collapses the same way.
There's quite a difference between modeling a construction to see how it behaves as a corporeal structure, versus modeling a significantly damaged structure to see if it will fail by modeling further damage.
But lets say you want to create a similar 1/10 model of some of the WTC, to investigate if the "official story" was accurate? How much of it would you need to build?
I don't need a physical model to know how the WTC collapse goes. I have video. Already modeled and proved to fail in fire, and gravity.
The chief structural engineer said the WTC collapsed as he expected.
"Why" wouldn't the actual footage of the collapses be "evidence" of the (at least theoretical) mechanisms?
So, how big of a model would you have to build? To what scale? And how many times would you have to build it?
3D printing is interesting, but it's only going to make a very small model, and it's not going to be made from the actual steel and concrete that's relevant to the discussion. And you won't be able to get the mass in there.
If one really thinking about the weight and size of a scale model, the reason for the collapse becomes less and less surprising. The smaller the model, the more it would have to weigh.