[ChuckNorris89]

Fatigue from what? It's a stationary object housed indoors, not a car or plane that goes through several climatical, temperature and environmental changes to cause fatigue.

Unless they were subjecting the tank to draining and filling cycles often, it seems more like a design/build fault that was a ticking time bomb from the start.

[Mikeb85]

The fact an object is stationary doesn't mean forces aren't continuously being applied... Same goes for bridges and every load bearing object.

[ChuckNorris89]

Bridges are outdoor subject to weather the forces of wind and the weight and harmonics of vehicles and people crossing them constantly.

A fish tank a relatively constant by comparison.

[gsatic]

The fish were having a race.

[danwee]

Gravity.

[ChuckNorris89]

Edited due to incorrect assumption.

[zimpenfish]

I'm no engineer but this would be static fatigue[1], no?

"[S]tatic fatigue occurs during prolonged and constant application of stress" (my emphasis) - much like the glass/acrylic at the bottom of a 14m high, 1M litre water column, say.

[1] https://en.wikipedia.org/wiki/Static_fatigue

[ChuckNorris89]

Interesting I didn't know that. Thanks for sharing.

[sidlls]

Settlement of the building it's housed in, temperature variations (things contract and expand as temperature changes), random impacts and vibrations (e.g., road traffic, heavy construction nearby), and so on. All of these contribute to fatigue.

[pvaldes]

A tropical aquarium is keep at the same temperature. Unless somebody would disconnect it to save energy or the termostat[s] would fall, shouldn't have experienced a lot of changes in their volume by this.

[sidlls]

It’s unlikely a structure this size has a temperature uniform enough consistently over time to avoid thermal fatigue.

[pvaldes]

Not so much. A big mass of water act as a temperature buffer and air pumps and filters are mixing the water column all the time. It takes several hours to cool.

The event does not seemed truly random to me. If it was, the probability of breaking in the 90% of the time when there was people around would be much higher than breaking in the 10% small time interval without people. Extreme luck is rare. Looking for an external trigger seems appropriate

But the only surface really accessible to people was the escalator, and now we know that it didn't broke. The outer surface is mounted over the escalator door, can't be scratched purposely without taking a lot of troubles. Can't be shoot without leaving evident marks of a crime

If we assume that the thermostat didn't broke and that material fatigue is not an optimum explanation (it was checked and maintained in 2020), then temperature differences seem a good candidate. It broke in winter, in the hour where day/night differences should be maximum. The outer temperatures that night were -10C if I'm not wrong.

[fwungy]

The hotel was required to reduce its lobby heating due to energy sanctions.

[petre]

Maybe the insurance companies could sue the government if this was indeed the case. I would really like to see the bad policy makers go to jail or get hit with huge fines.

[pvaldes]

Hum, A graph of the aquarium water temperatures by time would be interesting to examine...

[jacquesm]

The aquarium was likely very constant (otherwise the fish would die, they tend to be extremely sensitive to variations, especially rate of change), but the surrounding air likely was not.

[pvaldes]

Those fishes can stand an interval of temperature if changed slowly. A main question to check would be if the thermostat was deliberately lowered by the owner in the previous weeks to save energy

[jacquesm]

Thermal cycling is one option.

[fwungy]

Building temperatures were mandated reduced due to energy sanctions. This put stress on an already sensitive structure and caused it to fail.

[jacquesm]

This is speculation, not established fact.

[pvaldes]

Of course it is. At this moment everything is speculation.

[rzzzt]

Buildings move.

[pixl97]

This here.

The earth you live on is not solid, more like a squishy orange. When you build a heavy building on it, the building can sink further.

Buildings themselves are subject to the dynamic loads of temperature, wind, their occupants square dancing, and more.

Sometimes unexpected loads are added. A new highway or building built into a rock layer near it can subject the previous building to vibration and other forces and cause damages.

[DemocracyFTW2]

This, and it's in particular true for this very part of Berlin, a city that is well known for literally having been "built on sand", see https://de.wikipedia.org/wiki/Palast_der_Republik#Abriss_zwi... which is about the demolition of the comparatively big building of the Palast der Republik which was just across the street on the other side of the river. That building had to be carefully and slowly dismantled to avoid sudden changes in the hydrogeological (?) equilibrium of the load-bearing layers.

Given that amateur seismic stations located 8 and 14 km away from the location were able to pick up a signal from the event[1] of a 1000 tons of water falling to the ground from a height of ~ 2 to 15m, one should image the building itself should have had some sort of influence to its immediate surroundings.

[1] https://twitter.com/ErdbebenDE/status/1603654695293263873?re...

[jacquesm]

Sand is - strangely enough - quite stable. Clay, peat and lots of other substrates are a lot less stable than sand and when building on them you need to take all kinds of precautions to ensure your foundation doesn't one day go for a walk.