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Comment by q3k | Hacker News Reader

Testing in production with good enough metrics is fine unless it's AN ACTUAL BRIDGE.

I agree, but the bridge design appears to be extremelly robust (i.e., extraordinarily oversized) and it will be subjected to foot traffic, which has a negligible service load.

It's a pretty sculpture that people can walk on. That's it.

Robust aka oversized does not counter brittle fracture, though, which is the main concern with 3D-printed artifacts. It depends on the material / the alloy but also on the technological process we generally call printing.

It actually does, since it reduces the local stress. Risk of fracture due to defects and repetitive loading is dramatically reduced (by order of magnitude or more) by increasing the material margins.

It's a short foot bridge, so it's pretty easy to design it with significant enough margin.

That said, it's not a very good idea nor a scalable solution to, like, anything. More like an art project.

Yes, you are basically saying that this particular artifact is just like a bridge-shaped pancake made of polystyrene and hosting very few ants at any given time. Which is actually an art project.

I think that's overstating it. This bridge is plenty strong, just very inefficient and expensive.

> Risk of fracture due to defects and repetitive loading is dramatically reduced

In this case I believe the design is due to concerns regarding the additive manufacturing process, which is prone to introduce a lot more defects than standard steel sections, and ina way that are hard to spot and to track.

>It's a pretty sculpture that people can walk on. That's it.

Famous last words.

https://www.miamiherald.com/news/local/community/miami-dade/...

Bridges are supposed to be boring and functional. Fluffing them up with all sorts of over engineering to make them pretty tends to introduce unnecessary variables that are less well understood or less easy to account for or may be "unknown unknowns" which have the potential to reduce the strength of the structure.

https://www.nytimes.com/2018/08/14/world/europe/italy-genoa-...

If you want to make a pretty art piece then make a fancy ornate bridge deck and slap it on top of your boring but functional steel I-beams that reliably carry rail, road and foot traffic worldwide.

Walked on it last weekend. No more than 10 ppl were allowed on it at the same time. Guess they are still gathering data

Its not uncommon to leave stress strain sensors on bridges to know the state of the bridge even as it ages. Testing doesnt end when it goes into production for actual bridges. The best metric for measuring the bridges safety is strain under actual loading.

https://vimeo.com/239238204

Video shows physical material tests and simulated structural tests. What else would you suggest?

Well the bridge is approved and will be placed in Amsterdam

"Approved and placed" is hardly the same thing as "safe".

Case in point: https://www.miamiherald.com/news/local/community/miami-dade/...

Yeah, exactly. https://www.dw.com/en/prague-bridge-collapse-leaves-4-injure...

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