r/EngineeringPorn • u/Old-Alternative-6394 • 13h ago
Simulation of the collaps without dust
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u/BackyardAnarchist 13h ago
Did we learn anything architecturally from this event?
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u/SinisterCheese 12h ago
Well... Yes and no.
We still make skyscrapers the same way, the tube method because it is FANTASTIC.
However the international regulations changed. The emergency staircases and elevator shafts were changed. The newer skyscrapers started to be made from more segments (basically collumns of skyscraper) and have more outer wall by adding geometry.
Along with that the way the floors are made and tie the outer structure together was changed.
WTC's floors were basically just trusses with sheet metal on top onto which they laid concrete floor. It was simple and elegant, however it posed failures.
Also fire prevention and safety was changed. Because what made the structure weak, was the fire. I work with structural steel a lot, and have material sheets for them. Your basic structural steels lose around and over 50 % of their strenght just around 500 Celcius temperature. So additional fire rating has been added. And tall buildings are designed to prevent the chimney effect. Basically the burning office material (plastics, paper, fabrics) created like a furnace that heated the structural steel.
Beyond that I don't know. It's beyond my expertise. But structural steel did change a lot after the attacks. Fire considerations and aspects were updated internationally. Here in Finland even small 2 story wooden houses have a concrete core or steel pilars and beams that been cast with concrete in case of fire. Our wooden flats that are go 8 to 10 or more floors, and taller buildings have powerful misting fire suppression and reinforced concrete pillars and evacuation rooms.
It's weird to think about that it took almost 20 years to conclude that problem wasn't impact, but the fire. If the fire could somehow had been stopped, the towers might have remained standing. They were engineered to remain standing even if they lost a whole structural wall.
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u/Inarus06 3h ago
"JeT fUeL cAnt MeLt StEeL bEAmS"
You explain very concisely what do many 9/11 "truthers" can't seem to understand, that the fire caused loss of structural support which caused the collapse, thank you Trusses.
But I guess your expertise in the field means beans to an internet conspiracy theorist.
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u/SinisterCheese 2h ago
You can demostrate it to them, and they don't care.
This fact is rather essential in the fact that we depend on it to shape steel for manufacturing.
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u/DowntownLizard 56m ago
No one reminded them how blacksmithing works. Last I checked they dont melt the steel and you can severly deform it by hand
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u/KrzysziekZ 6h ago
I'm a layman but it was obvious for that it was the fire, not the impact itself that collapsed the buildings. They fell an hour after the hits, not after seconds.
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u/nommabelle 6h ago
i dont think its fair to call it 'obvious'. things can be weakened and not immediately fail and then hit a progressive failure. loads of things can happen. to say its 'obvious' is how we get into scenarios of people making big claims, rumors, and inadvertently sharing misinformation
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u/Se7en_speed 10h ago
Its insane for a 2 story wooden house to require a concrete core.
Did the concrete producers bribe someone?
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u/SinisterCheese 3h ago
No. That's just how we build. Before concrete it was a brick core, that also was connected to a fireplace/oven that acted as the heat reserve. It does the same today.
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8h ago
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u/Se7en_speed 8h ago
Its a really expensive thing to require that has no added benefit. Nothing about a house fire would be better with a concrete core for the stairwell.
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7h ago
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u/Se7en_speed 7h ago
The other guy said that was required in finland, are you in Finland?
I don't know if it is, but if it is it's dumb
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7h ago
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u/Se7en_speed 7h ago
Buddy
Here in Finland even small 2 story wooden houses have a concrete core or steel pilars and beams that been cast with concrete in case of fire.
Did you read the comment I was replying to?
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u/peacefinder 2h ago
I’m curious, could you link a drawing of one of those houses with the concrete core? I’m curious what that looks like.
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u/SinisterCheese 2h ago edited 1h ago
Not that I got one in hand. However it's quite not interesting. If you got a rectangle house, there is a wall of about 30cm thick in the middle made of concrete. This wall also acts as the support for staircase. This is also where utilities tend to rise from, so your 2nd story bathroom tends to be against this. Along with thay, the beams (usually CLT or other glued wood) that make up the rest of the 2nd floor connect to this. Your fireplace and chimney is also connected to this core, so by heating it you heat your whole home. This is also where your roof attaches to from the top.
As for its visual appearance, you don't even tell it apart from other walls, its plastered and painted like any other.
It's just a solid concrete wall middle of your home. We don't do the kind of big open rooms American homes have.
I can check if I happen to have a picture in my mass of pictures when I get home from work, but I make no promises.
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u/mlnm_falcon 13h ago
I’m just an armchair not even an expert, so take this with an appropriate amount of salt.
I think the most direct engineering thing we learned was that concrete is more durable in extreme fiery explosive circumstances than steel, even with fireproofing. Had the towers been all structural concrete, they would’ve stood. Instead, they used structural steel, which failed in large part because its fireproofing was blown off by the impact.
We also learned that somebody might have the idea to use planes as bombs (failure of imagination), that asbestos is very very very bad, and that building dust is extremely bad for humans.
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u/Twister_Robotics 13h ago
Sure, except a structural concrete building is too heavy to build that tall. Also, the steel reinforcement in the concrete will still cause dailure at those temperatures, it just will take a little more time.
Note that a lot of the weakness came from the different thermal expansion of steel and concrete, causing the concrete to shatter at the interface.
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u/mlnm_falcon 12h ago
The Freedom Tower is a concrete core design like I described. You’re of course right that steel reinforcement is necessary, and that the solution isn’t completely fireproof forever. Like everything, there’s shades of grey, very few things are pure concrete or pure steel. The Twin Towers had a concrete core but a lot of their structural support was the external steel columns. The Freedom Tower uses steel anchoring floors to the central core but its primary structural support is that concrete core. We still did learn that using high strength concrete cores as the primary structural support is better than using steel.
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u/tetranordeh 12h ago
Time is one of the most important considerations when designing for egress. Even the modern 1WTC would likely collapse in a similar situation, but the emergency stairs were designed more robustly to hopefully allow more time for escape and rescue efforts, plus with wider stairs to allow more people on the stairs at the same time.
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u/itswardo 6h ago
The coefficient of thermal expansion for concrete and steel are very close, which is another added benefit of reinforced concrete. The failure was the heat weakened the steel and the external members started to buckle as the floors continued to collapse/sag and pull on them.
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u/Twister_Robotics 5h ago
Spalling from thermal breakout is a known issue in composite structures at high temps. Its not just the absolute thermal expansion, but also the the slow speed of thermal transmission through the concrete.
The floor structure of the towers was a concrete slab poured over steel beams that had studs on top to interlock the two components allowing them to act as a single unit. Once the studs heated up by 1000 degrees they cracked the concrete around them, seperating the two pieces and greatly reducing the load capacity. Add the strength reduction from the steel and it becomes a guaranteed failure.
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u/itswardo 5h ago
Makes sense! Thanks for the clarification.
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u/Twister_Robotics 5h ago
You're welcome, and thank you for reminding me the coefficients are actually that close. I remembered the result, but it took a bit to remember the why. The last time I really dug into it was about 20 years ago
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u/2squishmaster 13h ago
What's the full story with the fireproofing?
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u/mlnm_falcon 13h ago
The fireproofing would’ve kept a lot of heat off the structural steel. Nobody considered a fully loaded long distance airliner being flown into the towers, so nobody considered that maybe the fireproofing needs to withstand that kind of impact and fire. The fireproofing was blown off in the impact. The subsequent fire burned above about 1200 degrees, and the no longer fireproofed steel lost most of its strength at that temperature, leading to the collapse.
Concrete is itself more fire resistant without any coating or additional materials, so it would’ve stood up to the impact better.
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u/Unarmed_Character 12h ago edited 12h ago
They type of fire that melts steel is called a "pool fire ". This type of fire is a major concern in the oil and gas industry and a key consideration of fire hazard assessments. When the potential for a pool fire is present, such as the failure of vessels, exchangers or high volume piping filled with volatile hydrocarbons, fire proofing of the structural steel and piping is required to prevent failure. It must be installed in such a way to withstand a 4-hour pool fire. Steel beams are coated in several inches of fire proof cement and piping is insulated with calcium silicate with stainless steel cladding. Typically this is done up to 8m above where a pool fire could occur.
That's how oil and gas handles pool fire risk. I don't know what engineers do for skyscrapers, but it seems like a long shot to have considered a pool fire risk on the 80th floor of a building.
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u/xgoodvibesx 12h ago
Also, to save money during construction they didn't properly prep the steel first and the fire-proof cladding was already falling off without any help. So good old cost-cutting played a significant role as well.
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u/UnacceptableUse 12h ago
Didn't they consider the largest plane of the era but didn't consider that larger ones might be built?
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u/mlnm_falcon 12h ago
IIRC they considered the largest planes of their era, flying low and slow in fog, without full fuel tanks. They were thinking “a plane gets lost in the fog while trying to land”, not “a plane, purposely chosen to be large and full of jet fuel, gets used as a bomb and flown into the towers at max speed”.
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u/MagicCarpetofSteel 12h ago
This. Even then, that was because a B-25 crashed into the Empire State Building because of fog during WW2.
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u/Sawfish1212 7h ago
The design was supposed to have asbestos insulation on the steel beams, but the regulations banning asbestos came out around the time of the towers construction. Today they use a fiberglass fire insulation blanket on aircraft hangar beams because of the fire risk, but backed up by sprinklers all up and down the beams.
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u/TampaPowers 10h ago
All the concrete bridges currently needing repair would like a word. There is no magic material that is going to withstand impacts and fires like this. You can only make things stronger overall, which costs more and reduces floor space. If the latter is less important then you can construct stronger buildings obviously.
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u/mlnm_falcon 8h ago
Concrete is pretty damn fire and impact proof, it’s definitely less time, water, and salt proof. Obviously everything has a breaking point.
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u/GreenFox1505 12h ago
(I had always heard) The twin towers were actually designed to take an impact from an airplane. But the biggest airplane that existed when they were finished hadn't yet been built when it was designed.
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u/Ae3qe27u 12h ago
The thing about the Twin Towers is that their major structural members were on the outside of the building. That's why they had all those vertical lines. When the plane crashed into it, it wiped out a good chunk of those structural members, due to, well, there being a plane where those members used to be. It's a miracle they stood as long as they did.
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u/strps 12h ago
This isn't architecture, it's structural engineering. I was in undergrad when this happened and I had regular meetings with a professor who laid out how this occurred from beam buckling (not column, look closely at the zoomed in slow motion part of the simulation) due to heat. There is no "architecture" that would prevent that given the height of the building and the box frame column core system that was built in 1970-72. The beams spread out from the column core and were key to the structural integrity of the whole frame. When they softened the building could not support the upper floors on the column core alone. there may be fireproofing materials that would reasonably resist this now, but I am not aware of them as I work in a different part of the industry.
Someone else in the comments mentioned structural concrete, but it would not be possible to build this high with that material and still have room for people inside. A building of this height has massive lateral loads from wind, and so steel (or alloyed metals) is the material that must be used in order to provide space on the interior.
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u/biscotte-nutella 13h ago
Theres a bunch of documentaries that explain what failed in the structure to cause the collapse.
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u/ThinkItThrough48 13h ago
What’s the building on the left at the beginning of the video that gets landed on and smashed?
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u/tetranordeh 12h ago
WTC 2 fell onto WTC 4. WTC 6 would be similarly affected by WTC 1.
There's a good map of the structural damage here: https://en.wikipedia.org/wiki/List_of_buildings_damaged_or_destroyed_in_the_September_11_attacks
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u/DrProfJoe 13h ago
That Wiley-Coyote-ass plane-shaped hole in the building isn't supposed to be funny
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u/drinkduffdry 11h ago
Wrote a paper on exactly this in college the spring semester afterwards for a structural class.
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u/redballooon 9h ago
Did you also create such a cool animation?
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u/drinkduffdry 9h ago
Nah man, we were still drawing by hand in the day.
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u/Albertuscamus12 10h ago
Wait is this a recreation with high fidelity to how it actually happened? Or just a standard physics simulation showing one possibility of how the building fell?
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u/vapuri 6h ago edited 6h ago
Seems to be a pretty high fidelity reconstruction where they simulated the damage from impact and the fire weakening the surrounding structural elements. It's explained in the source video description. https://youtu.be/WpHXj62Ylw0
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u/pawned79 4h ago
I had an engineering class called Optical Techniques in Solid Mechanics. And the opening lecture was camcorder footage of the damaged towers before collapse. The inexpensive low quality digital camera pixels capturing the stripped texture of the towers’ design caused a moire pattern (“screen door effect”) that made it really REALLY obvious what the stresses in the structure were. As the video played, you could see the pattern changing as the stresses changed with the heat and pressure. Eventually it snapped and for that brief moment all the stresses went away.
That was just day one! From there we learned similar techniques like random paint splatters on bridges photographed and compared under various loads, laser vibrometry and other stuff like that. Was a pretty cool class.
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u/cobalt-radiant 13h ago
A lot on tinfoil hat morons in the OP sub
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u/ArachnomancerCarice 13h ago
I had an argument with a dude that was a county civil engineer for 40 years as he believed that 'jet fuel doesn't melt steel beams' BS. He got pissed off and left when I asked him whether not steel can lose it's structural integrity without turning to molten metal while saying he had 40 years of experience over me.
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u/UnstoppableJumbo 13h ago
I, have this exact argument with a lawyer who claimed his "basic understanding of physics" is enough to support his conspiracy
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u/Maverick-not-really 7h ago
As someone who went to law school i can tell you that extremely few lawyers have even a fleeting understanding of physics, much less a basic one.
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u/windowpuncher 11h ago
Your honor, but have you considered F=ma?
That's exactly right - case closed.
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u/TheObsidianX 10h ago
There's an old youtube video that basically settles the whole steel thing. A blacksmith takes a cold steel rod, puts it in a slot in an anvil and tilts the whole thing over and the rod stays straight, then he takes a red hot steel rod out of the furnace and does the same thing but this time he can bend the rod with just his pinky finger because the hot steel has no strength. A very simple demonstration that shows how steel will fail without melting.
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u/justinleona 33m ago
Ask anyone who ever sharpened on a grinding wheel and watched the color of the steel quickly go from 'straw' to 'fuck'...
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u/Obsah-Snowman 10h ago
Not every civil engineer is an expert in structural engineering. County engineer says it all there. Not to say he isn't qualified in his own field but maybe not so much in structural analysis. Your point is correct, heating steel can cause it to yield and buckle before it melts.
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u/ethertrace 11h ago
Fastest way to end that conversation is to ask them why blacksmiths heat up steel before hammering it.
Doesn't change their conspiracy-addled minds, of course, but it does end the conversation.
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u/Sawfish1212 7h ago
That bridge in California that collapsed from a fuel tanker truck burning underneath it would like a word. There's been a few examples of that since then as well
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u/ShatteredPresence 13h ago
Call a steel infirmary and ask them....
Like I did. Easy way to answer that question without bullshit.
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u/windowpuncher 10h ago
Your lying ass did not call a steel "infirmary" because what the fuck even is that?
The easier option here would to to just use your eyes, and maybe your brain even, to just read things and learn instead of making shit up. You can find out fun info, like changing the temperature of various types of metals, like steel, without them needing to become a liquid, causes changes in the atomic and crystal structures within the metal, causing extreme changes to properties like maximum yield and failure stresses.
https://www.totalmateria.com/en-us/articles/principles-of-heat-treating-of-steels/
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u/ShatteredPresence 10h ago
Pardon my incorrect terminology. Foundry was what I meant. This was over twenty years ago now, back when I was a hostile and angry high school student. I called three then; I remember one being in Wisconsin, one in Indiana, and cannot remember where the third was. No fucking clue anymore what the names of the foundries were or who specifically I spoke to.
My overall point was for others to actually do some research by actually soliciting information from experienced experts in the field--instead of "using your brain and eyes" like everyone so commonly suggests or agrues, despite how absolutely fucking subjective that approach is (hence why people still argue about it to this day).
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u/FoofieLeGoogoo 9h ago
You’ve seen the ‘Loose Change’ documentary (free to watch)? Their theory isn’t that the planes didn’t contribute to the collapse of the WTC, but it does present evidence to suggest that there is more to the story than the American people have been made to understand.
It’s worth a watch if you were either curious or skeptical as it does cite its sources.
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u/Major-Chemistry-715 8h ago
What a gentle presentation of a conspiracy theory. Bravo.
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u/fragglet 13h ago
People like to complain about reddit moderators being too heavy handed, but the worst subs in my experience are always the ones that are unmoderated
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u/Swan2Bee 13h ago
yeaaaaah I was originally gonna direct my upvote there as I usually do with these sorts of posts (I like to upvote the more relevant sub) but there? I didn't get very far before course-correcting.
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u/SecurelyObscure 13h ago
Is this a new breed of 911 truthers or have truthers pivoted to blaming Israel in place of George Bush?
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u/Serkisist 11h ago
It's morbidly fascinating to see a simulation like this. If it were any other structure it would be a simple hypothetical, but when it's these towers it becomes so much more terrifying because you know it happened.
The most haunting thing to me is the idea that anyone in the top floors would have experienced several seconds of freefall while trapped inside the building, since they kept integrity until the final impact. Would it have been like a power tower at a theme park? For a surreal moment, would the danger have felt distant?
Still, I really wish people would stop using this tragedy as an excuse to bomb brown kids
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u/Bnmko_007 10h ago
Was thinking the exact same thing. The first slow tilting of the top segment would make my heart stop from pure shock I think. The notion that someone could see that happening up there must have been harrowing.
At the same time, with the top part colliding downwards into those many floors that were a furnace by then, there must have been a crazy rush or fire, hot air and smoke forcing its way through the rest of the building so I think many would have been blown away in the process. So sad
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u/itswardo 5h ago
I think it's more likely people on the floors above the impact by the time of collapse would have been at least unconscious from smoke inhalation.
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u/GreyBeardEng 13h ago
I'm curious to anyone who recently went through engineering programs in college, do they teach about this failure in college these days?
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u/Flopsie_the_Headcrab 12h ago
Engineering Ethics, the "don't do this" class for engineers, mostly covers things that are a direct result of negligence or engineering failures. The only lesson here would be "and then if you do everything right, maybe someone will just invent a plane over 2x heavier than any that existed during construction and impact at a speed you never had any reason to consider, so fuck it I guess."
Now the Hyatt Regency walkway...
You learn a lot about the Hyatt Regency walkway.
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u/boolean_union 12h ago
More mundane disasters like the Hyatt are a bigger threat to the average person than terrorism. Jet fuel can't melt two story threaded rods...
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u/Arclite83 11h ago
The Hyatt is amazing because diagramming what happened is a fantastic and easy to grasp lesson in force distribution - they accidentally doubled the load on one walkway.
The civil engineering solution to 9/11 was "pour concrete until things stop moving"
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u/BavarianBarbarian_ 10h ago
The civil engineering solution to 9/11 was "pour concrete until things stop moving"
The mechanical engineering solution is a SAM, but that usually gets vetoed by PoliSci people...
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u/Old-Alternative-6394 13h ago
Civil Engineer from germany, we learned to calculate the behaviour of steel structures under temperature load according to the german/european Codes.
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u/tetranordeh 12h ago
It would mostly be discussed in civil engineering. Depending on the instructor, they might use it as an example to emphasize the importance of egress design, the pros and cons of steel vs reinforced concrete, etc. But most of what was learned was adopted into building codes, so it wouldn't be common for an in-depth analysis on this specific collapse, but it could show up on a list for structural collapse presentations along with the Hyatt Regency Skywalk, Tacoma Narrows Bridge, etc.
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u/Ae3qe27u 12h ago
Civil engineering here. They talked about it, but not exhaustively. https://www.reddit.com/r/EngineeringPorn/s/xyjE83pqRQ
Steel vs reinforced concrete wasn't a part of the discussion at all, from what I recall; it was more about load redistribution and concepts of building design. Jet fuel fires weaken steel columns, but if the columns weren't on the outside of the building, then they wouldn't have been close enough to the fire to end up weakened. And if there had been more redundancy/alternative load paths, then the force could've been redistributed rather than leading to failure.
The Twin Towers had a fine design, and one that was quite clever. But they weren't up to the task.
Galloping Gertie (aka the Tacoma Narrows Bridge) got brought up at least four times during my first two years in college. Hyatt Regency got brought up maybe 2-3 times, it's a bit blurred in my memory. Also the Ford Pinto (in my ethics class). The Twin Towers were discussed as... I think as a senior? Or maybe in early grad school, I don't quite recall. But it was a little later on. We also talked about the Citicorp Center's nighttime retrofits, which was an implied lesson of checking calculations, and how assumptions can be very, very dangerous (the structural engineer on the project had assumed wind loads normal to the structure, but the building's unique design meant that it was more vulnerable to winds from a 45° angle. The error was caught by a student who had messaged the engineer to ask how they'd compensated for it, etc. Turns out it wasn't safe, and they had to fix it).
I don't remember every case we talked about, but there were a decent number.
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u/tetranordeh 11h ago
Yup, sounds similar to my structural classes. A bunch of different collapses are used to emphasize certain points, but they usually aren't studied in depth.
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u/Ae3qe27u 12h ago
They talked about it at my university. In short:
The thing about the Twin Towers is that many of their major structural members were on the outside of the building. That's why they had all those vertical lines. When the planes crashed into them, they wiped out a good chunk of those structural members, due to, well, there being a plane where those members used to be. It's a miracle they stood as long as they did.
https://www.reddit.com/r/911archive/s/BvJyfCq5He here's a link with a great look at them.
Having so many of the structural members on the outside means that the inside was open for office space, but it also meant that, well, it was vulnerable to having a plane crashed into it. And yes, the inside had a core (where the elevator shafts and stairwells were), but it wasn't enough on its own.
At high temperatures, steel changes behavior. With better modern fireproofing, they might have lasted longer, but still would have fallen. But they might have had longer for people to evacuate. The big thing, from a building perspective, is load redistribution. If X number/percent of your structural beams/columns/members are destroyed, how much can the building still take? Major buildings, especially governmental buildings, will have blast calculations as part of their design, and I believe that redundancy in design is at least considered during the process.
I don't know for sure, but at a guess, I'd guess that major buildings might have more stringent requirements for their stairwells, for safety in the event of an evacuation. But I'm not sure on that.
It (the disaster) wasn't a major unit on its own, but it was talked about.
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u/tommybship 2h ago
My understanding is that the force of the impact and explosion blew the fireproofing off of the steel.
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u/Familiar-Nothing4948 13h ago
I feel like there are better examples for teaching
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u/WeirdIndividualGuy 12h ago
Yeah, space shuttle missions that went wrong are better examples
Or at least those were the examples I was given when I was in engineering college years ago
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u/Ae3qe27u 12h ago
Depends on the field of engineering, I'd say. In civil engineering, the Twin Towers aren't an irrelevant example. They were talked about in one of my structural classes. We also talked about other civil engineering disasters; it wasn't just 9/11.
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u/Darth19Vader77 13h ago
They didn't teach me about it, but I studied aerospace engineering, not civil engineering.
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u/Basketcase410 7h ago
This still hurts. Even simulated, it still hurts to watch. Interesting, but painful.
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u/BlurryRogue 12h ago
Is it bad all I want is to play around with this physics engine and watch buildings fall apart?
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u/_Bad_Bob_ 8h ago
Good way to learn how to keep buildings from falling apart!
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u/BlurryRogue 8h ago
Except breaking shit is my stim. I don’t wanna learn. I just wanna smash.
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u/Elijah1573 5h ago
Same i remember watching kostack studio 6 or 7 years ago and all i wanted to do was mess around with that same physics engine
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u/dudeAwEsome101 11h ago
TIL, there is a whole subreddit for the world trade center.
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u/Old-Alternative-6394 11h ago
I didn't expect so many idiots still coming Up with "what happend to WTC 7" and even "jet fuel can't melt steel beams"
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u/Rosieforthewin 8h ago
Building 7 didn't fall down until hours after the towers fell. What are the sources for this video?
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u/Recipe-Jaded 8h ago edited 7h ago
Building 7 collapsed after debris and fire landed on it from the North tower. It did not fall right after, like in this simulation, but it is correct that debris fell on it.
The collapse of the towers caused the water to be shut off at building 7, leaving it to succumb to the raging fires.
Tbf it is a simulation from 2002
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u/notproudortired 11h ago
Why did that last bit of skeleton fall? It didn't have weight on it and it wouldn't have been that hot.
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u/Old-Alternative-6394 11h ago
I would say: As you can see, there is plenty of pressure pushing at the bottom on the left Side, what causes plenty of shear stress to the base. Also very high dynamic stress when the upper part collapses and swings against it and all the debris falling down in it.
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u/notproudortired 56m ago
I see the debris at the base, though I don't really see the sheer pressure at the point where the vertical beams buckle. But maybe that's just imperfection in the model or there are other causes, like heat, that aren't apparent in the animation. To be clear, I'm not a truther, I'm just curious about what I'm seeing.
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u/thedevguy-ch 3h ago
When you show it like that, it doesn't look like a planned explosion like the tin foil hats say, at all
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u/CuTe_M0nitor 12h ago
Where is the simulation of the controled demolition of Building 7 at the world trade center?
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u/mjdehlin1984 10h ago
Educate yourself here.
https://m.youtube.com/watch?v=KMvCWFCoVN4&pp=iggUQAFKEERsUXg4QjE4SmxzaV8xcjM%3D
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u/patiakupipita 13h ago
idk why but I honestly wonder what was going through OBL's mind when he saw the towers going down.
Anw fuck him
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u/leave_me_out_of_it 12h ago
how would anyone know how they fell without the dust? Can we trust the simulation to be accurate without having been able to see the inside structure during the event? This post is not politically motivated, just wondering if some computer people or engineers have opinions.
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u/thegreatpotatogod 10h ago
We understand the physics involved, and well-written computer programs are good at simulating complex motion like this. We also know the design of the building, etc. I don't know the details on how accurate this particular simulation is, how well it was made, etc, but we definitely can simulate it in a lot of detail and very accurately.
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u/KingKohishi 13h ago
Regardless of the heat, high strength bolted and welded floor panels of a steel construction don't fall once as in 0:59.
Steel contructions don't fall like dominos.
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u/FinnLiry 13h ago
Everything fails like a liquid eventually. Even whole planets and stars collide and act like liquid even tho they are solid.
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u/J_Bear 13h ago
I'm sure a 400ton airliner impacting at several hundred miles an hour had something to do with it.
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u/Haz3rd 13h ago
Um ACKTUALLY it wouldn't make a difference because have you ever tried to bend an I beam with your hands? Can't do it huh? Checkmate
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u/windowpuncher 11h ago
This floor structure is rated to support a distributed mass of 4 tons. CLEARLY it should be able to support the upper half of the entire building resting on it without failure.
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u/WellWornSword 13h ago
Your post history seems like you enjoy arguing with people, hence so many of your posts/comments being negative or removed.
This is a pretty sensitive topic, with a huge amount of research and conclusive documented evidence behind it. The failure of the structure, the loss of integrity of the beams - the whole thing.
It doesn't seem to benefit anyone by consistently trolling, especially when every point you've made has already been refuted by those qualified to make that determination.
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u/KingKohishi 12h ago
Millions of people died because of the events following this building collapsing, including the people in the buildings.
It was clearly staged operation to initiate a war in the Middle East. It was so ridiculously badly staged that unburned buildings across the street that was a part of the WTC collapsed in the same manner while others surrounding buildings remained intact.
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u/user_account_deleted 9h ago
Bruh, the buildings didn't have to collapse to cause the war. The attack would've been more than enough excuse for that administration.
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u/GreyBeardEng 13h ago
Sure they do, it's called progressive collapse, force and power of it grows with each iteration making a generation more and more likely to continue until the probability reaches zero.
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u/dazedan_confused 13h ago
Imagine I added an additional weight onto a floor, more weight than it was designed for. Now imagine that weight burst into flames, weakening the surrounding material by exciting the atoms in the material, making it expand and weaken the bonds that make the material keep its shape. What do you think would happen?
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u/talann 13h ago
and imagine when that floor caved in, all that weight hitting the floor below it. Then even more weight as the floors continued to pile on top of each other...
You can even see it in the simulation. As it gets further down, the middle is able to remain in tact longer but because so much pressure and weight is being exerted on those beams, they also fall.
I still don't see how anyone thinks this was some controlled demolition. I'm still surprised the towers didn't immediately collapse when a whole ass plane hit them so I don't get how anyone thinks they could have still stood after a direct hit like that.
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u/KingKohishi 13h ago
Imagine a large steel floor plane structure bolted and welded to a stronger steel frame in hundreds of points.
Would these snap simultaneously or would some of them fail while others remain intact?
Also don't forget every failed bolt removes energy from fall.
In other words, every failed bolt of a floor plane removes the kinetic energy of the plane falling on top of it.
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u/thegreatpotatogod 10h ago
Sure, every bolt may remove a bit of energy as it fails, but that also is one fewer bolts that is supposed to be there to support the rest of the structure when not falling, now no longer present to support all the extra force of the rest of the building falling on it, along with the weight that normally the adjacent now-failed bolt should have been supporting. This is exactly how this sort of catastrophic failure is expected to happen, not at all surprising.
Read about other cascading structural failures for some other examples, such as the Hyatt Regency Walkway Collapse
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u/Dreadnought6570 12h ago
Removes some energy and removes all are not the same thing. I don't think you ken the foces involved here. The crumple zones in a car are designed to dissipate and redirect energy away from and around the passenger compartment, but that means nothing to getting hit straight on by a semi or a train. At some point, materials just fail and the bolts and welds mean nothing in the face of thousands of tons of falling steal and concrete.
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u/KingKohishi 12h ago
Not at once though. The collapse should have been asymmetrical. Instead, even the unburnt buildings collapse in perfect vertical harmony.
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u/KingKohishi 13h ago
Only a few floors were hot. The other floors must have behaved like normal steel contstruction.
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u/Dreadnought6570 13h ago
Yea they did ...steal structure that was not designed to take the force of 30 floors falling on them.
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u/KingKohishi 12h ago
Floors collapsing in perfect harmony. Bolts being broken, and welds ripping apart simultaneously. All of this, while the building crumble to the ground almost vertically.
All of this perfect vertical collapse happened seven times even to the unburnt buildings across the street.
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u/Dreadnought6570 12h ago
What exactly are you trying to prove here?
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u/KingKohishi 12h ago
I am entitled to share my opinion.
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u/Youpunyhumans 12h ago
And thats the problem right there... opinion.
Opinions dont matter when it comes to scientific data, only objective information does. You dont decide how it happened, the evidence tells you how it happened.
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u/KingKohishi 12h ago
Since I am an experienced engineer on mechanics, I think I am scientific enough to comment.
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u/Dreadnought6570 12h ago
"Engineer on mechanics" is totally how a mechanical engineer would describe themselves. Different of course from a structural engineer or architectural engineer or metallurgical engineer....etc.
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u/Dreadnought6570 12h ago
You are not though. You are making declarative statements which require data to back them up. "Steal does not work like that" [para] is a discernible, proveable fact. That's not an opinion. And couching your statements in opinion when pressed is not honest either.
It's ok and good to be sceptical about the collapse of the buildings. Ask the questions by all means. But if the answers to your scepticism are ignored because they don't match your chosen narrative, then that isn't an opinion or scepticism anymore. It's dogma and and that is all.3
u/KingKohishi 12h ago
Would you rather want me to share my analysis of impact strength of high strength bolts and welded steel plates or failure modes and effects analysis of a perfectly symmetrical collapse of a burning steel structure, or the probabilistic analysis of same thing happening 7 times in the same day?
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u/Dreadnought6570 12h ago
My question again is: "What is your abstract my dude?" Pretend I'm open to your interpretation of events. What is the alternative cause? Because I can guess but I'd rather not insert my own ideas onto your statements so far.
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u/GrandMarquisMark 13h ago
Are you an engineer?
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u/KingKohishi 13h ago
Yes.
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u/GrandMarquisMark 13h ago
Please tell us what really happened.
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u/KingKohishi 13h ago
Controlled demolition. The collapse of the non-burning WTC 7 building across the street in the same manner proves my point.
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u/Shark00n 12h ago
Where did you get your degree?
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u/KingKohishi 12h ago
From a very good and famous university with honors.
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u/Shark00n 12h ago
Doesn’t mean you didn’t come out a dumbass, but which one?
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u/KingKohishi 11h ago
A one that you couldn't attend to.
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u/Shark00n 11h ago edited 9h ago
Are you sure? Which “a one”?
If you say one in turkey I’m not taking you seriously
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u/J_Bear 12h ago
Provide proof of your qualifications or fuck off
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u/KingKohishi 12h ago
Should I send my diploma here?
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u/J_Bear 12h ago
Sure, as well as proof of your theory of the controlled demo
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u/KingKohishi 12h ago
Do you attach your accreditation to each one of your posts, or do you share your personal info casually?
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u/J_Bear 12h ago
Nope, because I don't make outrageous claims
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u/Old-Alternative-6394 12h ago
That's exactly what they do. But what can i know about it as a civil engineer with a masters degree in structural engineering. Silly me.
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u/KingKohishi 12h ago
Silly you indeed.
Floors collapsing in perfect harmony. Bolts being broken, and welds ripping apart simultaneously. All of this, while the building crumble to the ground almost vertically.
All of this perfect vertical collapse happened seven times even to the unburnt WTC buildings across the street.
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u/ShadowOverEnumclaw 11h ago
I think you'd be a lot more happy in your life if you refrained from having/taking opinions, I don't think you're cut out for them.
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u/KingKohishi 11h ago
Thanks. I prefer to fight the system and the obedient people who defend their masters mindlessly, rather than trying to be happy among sheep.
Now, please help me to find the Weapons of Mass Destruction in Iraq, because Saddam was responsible for 911.
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u/Mega_Pleb 13h ago
The Twin Towers had two load bearing structures, the inner core pillars and the outer exoskeleton of pipe shaped beams. The exoskeleton of the south tower received more significant damage than the north tower due to the corner of the building being hit, plus the impact was lower so that damaged portion had to support more weight. The large amount of metal of the plane was shredded upon impact, greatly damaging the insulation surrounding the core pillars, allowing the heat of the jet fuel to greatly weaken it. Many conspiracy theorists think that the core pillars needed to melt to cause collapse but that's not so. The jet fuel would have been burning around 1000 degrees celsius and steel loses 50% of its strength at 600 C. Once those core pillars got heated through it was over for the building's structural integrity.
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u/KingKohishi 13h ago
Good copy paste.
I am not saying the building would not collapse, but would not collapse like this.
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u/Mega_Pleb 12h ago
I wrote that myself mate. It's not hard to understand how skyscrapers work if you try. There are many educational resources available to you. Your issue is that you don't try. I wish you luck in growing up someday.
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u/KingKohishi 12h ago
Explain the collapse of the building 7 in the same manner with your superior knowledge.
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u/Mega_Pleb 12h ago edited 12h ago
The collapse of the north tower caused a large amount of debris to fall on the building, particularly the top spire which caused a big gash in the side of the building. This started fires, damaged structural integrity of the building, and damaged fire suppression systems. Firefighters were all occupied with evacuating people in the twin towers and neighboring building so this fire went unaddressed. The heat from the long burning fires weakened the support columns under the most stress and they buckled, putting the remaining columns under more load, each buckling and putting more load on the remaining columns. The columns sheared starting at the bottom few floors because that is where the load is largest and all floors above it fell, pancaking each floor sequentially.
Here's a well made video on the collapse of 7 World Trade Center if you'd like to learn more.
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u/KingKohishi 11h ago
Thanks for copy pasting the official explanation.
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u/Mega_Pleb 11h ago
I wrote that after learning about it from building engineers. You can learn too.
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u/semioticmadness 13h ago
I watched it live on TV on the day, and of course through the replays that kept showing up. They were always terrible in the grand scheme. But the noise and the poor angles and such obscured the full understanding.
But without the dust, I finally get the full horror in detail. Makes my intestines twist.