Author Topic: Berlin AquaDom explosion - what went wrong?  (Read 12316 times)

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Offline rdl

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #75 on: December 19, 2022, 04:23:35 pm »
I'm not exactly sure why, but this seems a little odd to me.

The interview stresses a couple of times that there was a risk of the 20 cm thick acrylic drying out if it is no longer in contact with water from the inside, which could cause cracks. They applied adhesive foils to the acrylic to avoid this.
 

Offline ebastler

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #76 on: December 19, 2022, 05:20:41 pm »
I'm not exactly sure why, but this seems a little odd to me.

The interview stresses a couple of times that there was a risk of the 20 cm thick acrylic drying out if it is no longer in contact with water from the inside, which could cause cracks. They applied adhesive foils to the acrylic to avoid this.

Yes, that surprised me too, and is counterintuitive. But despite being hydrophobic, PMMA (= acrylic) can absorb water, up to 2% by weight: https://pubmed.ncbi.nlm.nih.gov/22799564/

Surprising that thin adhesive foils should be enough to prevent the PMMA drying out. But the application of these foils was nicely visible in the refurbishment video someone share earlier in this thread. Maybe they only need to slow down the evaporation, so it happens slowly and without causing excessive stress in the material.
 

Offline ebastler

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #77 on: December 19, 2022, 05:26:55 pm »
This kind of funny stuff like the AquaDom shall be designed and constructed such way that in case of a failure the water has the free way to escape without causing catastrophic damages or dead bodies. An assumption such that specific construction will last forever would be pretty naive one, imho..

Right. Just like it's good practice to design towers, bridges and cranes in a way where they gently sink down in case of a collapse, provide an emergency exit to the occupants, and sort the rubble into neat piles in the process.  ::)
 

Offline AndyBeez

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #78 on: December 19, 2022, 05:27:38 pm »
I wonder if "modernize" is a poor translation.  I have heard other Europeans use that word when they mean "refurbish". As far as I know they didn't replace the actual panels themselves.  That would require the roof structure to be removed (at the very least) and would be extremely disruptive.
During refurb, the panels were wrapped in plastic film and shrouded in a giant curtain; maybe to ensure the acrylic didn't dry out or go out out of geometry. Modernized; in the UK we say, "in need of updating", so what was updated? Someone clearly felt the need to rearrange the rocks on the bottom of the ocean, but was there a more fundamental motivation? Was the Aqaudom out of it's OEM guarantee? And was the 'modernizing contractor' the same firm as the OEM installer? Until someone puts the broken pieces together like an air crash investigation, no-one will know where the fail started.

Either way, this spectacular fail will be a memorable case study for structural engineering students for decades to come.
« Last Edit: December 19, 2022, 05:31:01 pm by AndyBeez »
 

Offline tooki

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #79 on: December 19, 2022, 05:54:49 pm »
FYI to our German-speaking friends, in English, “folie” translates to “film” for plastics, while “foil” is for metals. We never say “plastic foil”, while “metal film” is possible, but then means a thin layer on some substrate (i.e. “Metallbeschichtung”).

What I wondered from the start is whether they use scratch-resistant films on acrylic aquaria. Many of the public transit vehicles here in Switzerland are now having films applied to the windows to stop vandals from scratching the glass. The film is essentially sacrificial.
 
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Online tom66Topic starter

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #80 on: December 19, 2022, 06:03:35 pm »
The slides linked in a prior post indicate pedestrian scratches and impacts are just something that has to be accounted for in the design, but it's amazing how little damage is needed to weaken the structure. The indication (chart on slide 27) is that the entire material strength is reduced by around 5x for a 2.5mm deep scratch, which seems utterly mad to me, but material physics is weird.  I am not sure whether this is just for the 'wet' side (with the greatest pressure) or if any part of the material could be susceptible.
 

Offline AVGresponding

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #81 on: December 19, 2022, 06:06:04 pm »
The slides linked in a prior post indicate pedestrian scratches and impacts are just something that has to be accounted for in the design, but it's amazing how little damage is needed to weaken the structure. The indication (chart on slide 27) is that the entire material strength is reduced by around 5x for a 2.5mm deep scratch, which seems utterly mad to me, but material physics is weird.  I am not sure whether this is just for the 'wet' side (with the greatest pressure) or if any part of the material could be susceptible.

The dry side would be the critical one in this case, as it's under tension, while the wet side is under compression.
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Offline ebastler

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #82 on: December 19, 2022, 06:57:17 pm »
FYI to our German-speaking friends, in English, “folie” translates to “film” for plastics, while “foil” is for metals. We never say “plastic foil”, while “metal film” is possible, but then means a thin layer on some substrate (i.e. “Metallbeschichtung”).

Aha, thank you! I have used "foil" in various contexts, and it always felt wrong. But "film" didn't come to mind, although I must have read it many times -- and I never realized that English uses different words depending on the material. Learnt something new today! :)
 
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Offline pcprogrammer

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #83 on: December 19, 2022, 07:47:54 pm »
... so what was updated? ...

In the article eblaster provided, they state that near the base it was leaking water and needed attention. They replaced the silicone seal between the concrete base and the acrylic cylinders.

Quote
With a million liters of water, i.e. a weight of 1,000 tons, there is enormous pressure at the bottom of the aquarium, which is made more difficult by the salt content of the water of 3.5 percent. After 15 years of continuous operation, a certain amount of material fatigue is completely normal. In the lower area, slight leaks actually formed and moisture escaped. So there was a need for action.


Offline rf-messkopf

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #84 on: December 19, 2022, 10:31:34 pm »
The slides linked in a prior post indicate pedestrian scratches and impacts are just something that has to be accounted for in the design, but it's amazing how little damage is needed to weaken the structure. The indication (chart on slide 27) is that the entire material strength is reduced by around 5x for a 2.5mm deep scratch, which seems utterly mad to me, but material physics is weird.  I am not sure whether this is just for the 'wet' side (with the greatest pressure) or if any part of the material could be susceptible.

On German TV a guy from Deutsches Meeresmuseum Stralsund was interviewed who said that in large aquariums it is general practice to regularly check polymer panes for scratches from visitors, and to polish them out as soon as possible. Happens easily when people scrape their backpacks along the pane.
 
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Offline james_s

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #85 on: December 19, 2022, 10:40:51 pm »
On German TV a guy from Deutsches Meeresmuseum Stralsund was interviewed who said that in large aquariums it is general practice to regularly check polymer panes for scratches from visitors, and to polish them out as soon as possible. Happens easily when people scrape their backpacks along the pane.

I'm surprised there isn't a non-structural protective layer on the outside for that reason. Something similar to the adhesive film used to protect car headlights.
 
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Online tom66Topic starter

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #86 on: December 19, 2022, 10:55:24 pm »
Of course, in this case it's unlikely that the aquarium was scratched by a normal member of the public, except if someone climbed onto it... which is probably something you'd notice.  But, could divers accidentally damage it during the routine feeding and cleaning that was performed?  A heavy SCUBA tank hitting the walls of the tank accidentally could damage it - and if you weren't paying attention, maybe it would go unnoticed?  I can't see how you could spot the kind of damage that leads to unexpected failure unless you vigorously inspect the tank regularly.  The safety factor is around 11x for these types of tanks, so if the scratch/fracture damage is beyond about 5mm deep (out of a total of 200mm) it sounds like you lose that factor altogether and unzipping is all but guaranteed.  How many acrylic aquaria are there out there where divers regularly have access to the interior space?  I can think of larger ones, but they are only part acrylic, like around viewing windows and so on.
 

Offline rf-messkopf

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #87 on: December 19, 2022, 10:56:12 pm »
I'm surprised there isn't a non-structural protective layer on the outside for that reason. Something similar to the adhesive film used to protect car headlights.

I can only guess but a protective layer would surely degrade the optical properties of the pane and distort. Maybe the visual impression is supposed to be particularly spectacular. However, scratches from visitors probably weren't a problem in the case of the AquaDom, because it seems that the public had no way to touch the panels.

I have walked past that building countless times, but I never knew that tank inside even existed. From the pictures it does not look too aesthetically pleasing though, but more like a hydrodynamic test facility. :)
 

Offline tooki

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #88 on: December 19, 2022, 11:49:45 pm »
The slides linked in a prior post indicate pedestrian scratches and impacts are just something that has to be accounted for in the design, but it's amazing how little damage is needed to weaken the structure. The indication (chart on slide 27) is that the entire material strength is reduced by around 5x for a 2.5mm deep scratch, which seems utterly mad to me, but material physics is weird.  I am not sure whether this is just for the 'wet' side (with the greatest pressure) or if any part of the material could be susceptible.

On German TV a guy from Deutsches Meeresmuseum Stralsund was interviewed who said that in large aquariums it is general practice to regularly check polymer panes for scratches from visitors, and to polish them out as soon as possible. Happens easily when people scrape their backpacks along the pane.
Sure. But in this case the aquarium was 8m off the ground, so no contact with visitors.
 

Offline james_s

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #89 on: December 20, 2022, 12:28:07 am »
This is exactly why I refuse to fly in an airplane.

Most failure modes of an aircraft is to fall out of the sky and bury itself into the ground.

In a car at least you can jump for your life or slam on the brakes or give the finger to whoever is crashing into you.

You cannot do that to a wasp, a ground mechanic thousands of kms away who decided to be incompetent that day, or a design flaw.

Some things were just not meant to be built, the commercial aircraft is one such thing.

i'm not lucky enough to roll that dice. I was born into a family of luddite schitzoaffective parents and every single thing in my life which would affect my career has had a catch 22.

In other words you either lack an understanding of math and statistics, or you are more driven by emotional feeling than by logic.

Yes if a crash occurs you are more likely to survive in a car, however per mile driven you are many times more likely to get into a crash in a car. Per mile traveled, flying is much safer, that is not an opinion, it is an objectively true fact. Commercial aircraft are extremely safe, there are thousands of them in the air at any given time and crashes are so incredibly rare that they make front page news any time they happen. Fatal car accidents happen every single day, they are so common that they don't even make the local news most of the time.
 
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Online EEVblog

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #90 on: December 20, 2022, 02:30:44 am »
This thread is good for months of idle speculation, until the insurance experts release their actual assessment of the fault. Has anyone looked into the position of the planets yet, or the effect of 5G networks?  :horse:

We cant rule out a directed beam energy weapon. Or aliens.
 

Offline james_s

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #91 on: December 20, 2022, 05:00:55 am »
We cant rule out a directed beam energy weapon. Or aliens.

That might not be quite as absurd as it first sounds, well, the first part anyway. I have some small diode lasers that are capable of >1W of optical power output and can be run from batteries. I really doubt it is what happened here, but an invisible IR diode laser of a few watts might be enough to damage the acrylic, they certainly will set cardboard on fire from across the room. I'm not seriously suggesting that's what happened but it is technically plausible.
 

Offline Sal Ammoniac

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #92 on: December 20, 2022, 05:02:43 pm »
That's a good point. Also a lot of that water will have gone into sewers and underground.  It could easily corrode parts of the structure for the hotel and adjacent buildings if it is not cleaned up promptly.
I've heard too much sodium chloride can create other problems in the treatment plant, as the microbes used aren't the right type to deal with it.
I don't think that's too much of a problem. My water softener uses about 50 pounds of salt a week and all of that goes into a septic tank and it doesn't seem to have any effect on the bacteria that break down the waste.
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Offline tooki

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #93 on: December 20, 2022, 05:25:14 pm »
This is exactly why I refuse to fly in an airplane.
Well I’m sorry to be so blunt, but that attitude is just stupid.


Most failure modes of an aircraft is to fall out of the sky and bury itself into the ground.
Nope, absolutely incorrect. Most failure modes result in “the passengers didn’t even realize anything went wrong because the 3-4 layers of safety design completely prevented a failure from causing a catastrophe.” Commercial aviation is THE model of how to perform safety engineering, with every incident being thoroughly analyzed and effective countermeasures taken by actually doing skilled root cause analysis.

I don’t know of any other industry that even comes close to commercial aviation’s level of safety engineering. (No, it’s not perfect in the Boolean sense. Do not list exceptions to “educate” me, folks, I am well versed in this industry.)

And on the other hand, by design, airplanes want to fly. Things have to go insanely wrong for a plane to literally fall (i.e. complete unrecoverable aerodynamic stall) from the sky. It’s possible to glide a jumbo jet to the ground unpowered, and it’s been done more than once.

I highly urge you to deep dive into the YouTube channel called “Mentour Pilot”. He, a commercial airline pilot and trainer, goes into the hows and whys of aviation, including doing FAR more in-depth explanations of aviation incidents, but with the explanations of an aviation insider needed to give the proper context to what happened.

You cannot do that to a wasp, a ground mechanic thousands of kms away who decided to be incompetent that day, or a design flaw.
And this is the root problem with skeptical flyers: loss of control. We know from research that a) people are insanely bad at weighing risk, and b) vastly underestimate risk when they’re in control (and overestimate it when they’re not). You need to be honest and recognize that this psychological bias is why you don’t fly, and not facts.

Some things were just not meant to be built, the commercial aircraft is one such thing.
What an obnoxiously arrogant thing to say.
 
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Online SiliconWizard

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #94 on: December 20, 2022, 09:09:28 pm »
This thread is good for months of idle speculation, until the insurance experts release their actual assessment of the fault. Has anyone looked into the position of the planets yet, or the effect of 5G networks?  :horse:

We cant rule out a directed beam energy weapon. Or aliens.

Or maybe it's Elon's fault too. Who knows!
 

Online NiHaoMike

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #95 on: December 20, 2022, 11:07:28 pm »
One detail that hasn't been mentioned is that while the water would keep most of the tank at basically the same temperature, the part above the water line would be closer to ambient and thus thermal stress is still a possibility.
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Offline HighVoltage

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #96 on: December 21, 2022, 09:58:00 am »
Isn't the cross stress in a cylindrical shape always twice as high as the stress in direction of the axis?
(This might only apply to closed systems like a pressurized tank)
But in any case the cross stress should be higher.

If so, one could easily measure the circumference of such cylinder and monitor it at the AquaDom bottom, where the static load is the highest. This way there would be an alarm system go off if the diameter gets too large.

I wonder if there was any monitoring for mechanical stress in the cylinder.
It could have easily be applied and the cost would be minimal compared to the overall construction cost.
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Online EEVblog

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #97 on: December 21, 2022, 11:15:50 pm »
 

Online SiliconWizard

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #98 on: December 21, 2022, 11:38:28 pm »
Interesting, especially about the responsibilities, but he says "nobody was hurt", and I beg to differ. Poor fish.

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Offline Bud

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Re: Berlin AquaDom explosion - what went wrong?
« Reply #99 on: December 21, 2022, 11:49:30 pm »
I am guessing the elevator went kaput as well ?
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