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https://en.wikipedia.org/wiki/Tretten_Bridge https://en.wikipedia.org/wiki/Tretten_Bridge The ironic part is "The bridge replaced a steel truss bridge built in

by rdtsc 3y ago

https://en.wikipedia.org/wiki/Tretten_Bridge https://en.wikipedia.org/wiki/Tretten_Bridge The ironic part is "The bridge replaced a steel truss bridge built in 1895 at the same location". Engineers in 1895 knew how to use steel trusses and built a bridge that lasted 100+ years, and in 2012 they decided to use glued wooden beams and it fell apart in 10 years. Well perhaps Plan Arkitekter and Norconsult can take a trip to the archives and see what the engineers in 1895 knew before building any more structures.

loeg 3y ago
> Engineers in 1895 knew how to use steel trusses and built a bridge that lasted 100+ years It's a little too strong of a claim. Plenty of poorly designed steel bridges from the 19th century have collapsed as well, despite the superior material.
- rdtsc 3y ago
  > Plenty of poorly designed steel bridges from the 19th century have collapsed as well That's true. But I only meant that particular bridge, which did last for 100+ years. So, when the architects and the engineers go to the archives to relearn a few things, they can focus on the ones which haven't collapsed.
  - hellofellows 3y ago
    + why even remove the steel bridge in the first place?
    - speedgoose 3y ago
      You have more pictures on the Norwegian Wikipedia page: https://no.m.wikipedia.org/wiki/Tretten_bru#/media/Fil%3ATretten_bro_(1895).jpg https://no.m.wikipedia.org/wiki/Tretten_bru#/media/Fil%3ATre... The old one wasn’t wide while the new one had two lanes and a normal sized sidewalk.
    - TylerE 3y ago
      Moisture causes corrosion. Rivers produce lots of moisture. Corrosion weakens the steel. It's literally the metal flaking away. All steel corrodes. Even stainless. Once corrosion sets in and the outside of the metal starts to pit, the corrosion speeds up drastically. (The old area vs volume thing, same thing that makes lump coal difficult to ignite while aerosolized coal dust is practically an explosive). Here's a modern US bridge - all steel - that collapsed in Pittsburgh two years ago. In some areas over 80% of the original steel thinkness was gone after 49 years. https://www.youtube.com/watch?v=J-VnWB4fiFk https://www.youtube.com/watch?v=J-VnWB4fiFk
      - Gare 3y ago
        Paint protects steel. A frequently painted steel bridge can last centuries. As always, lack of maintenance and poor design choices (use of corten steel) are the culprit.
        TylerE 3y ago
        Something like 20% of the bridges in this country are 10 years or more past their design lifetime and mostly not due to be replaced any time soon. You think they're keeping on top of painting every one? Saying preventing corrosion is as easy as slapping on paint is like saying computer security is as easy as not leaking your password. There are a million things that could happen, many of which are outside what any single person could control.
        Gare 3y ago
        I don't know in what poor country you live, but in my country bridges are well maintained and I don't recall a single critical failure. Even though we're one of the poorest EU countries.
        tharkun__ 3y ago
        I don't know in what rich poor EU country you live, but in my "rich country" bridges are basically left to their own devices until a critical problem occurs and then they hastily start repairing it. In some cases they've been repairing bridges for decades that way. Some have recently finally actually been replaced or are being replaced. But nobody is going out and replacing a bridge that isn't on the brink of collapse and held up by "essentially duct tape".
  - x3n0ph3n3 3y ago
    To be fair, there have been a lot of advancements in timber and glue -- They just didn't take into account their weaknesses when designing (e.g. Stress that would pull laminated beams apart).
    - Gare 3y ago
      There are always unknown unknowns in trying new designs and/or materials. Even with all the simulations and calculations, nothing beats experience. Sure, novel things should be tried, but in a conservative manner. Overdesign first, then optimize iteratively. Because failure costs lives.
      - mcphage 3y ago
        Glulam isn’t a new material, it’s over 100 years old.
        Gare 3y ago
        How many 70 m span glulam road bridges have been built in those 100 years?
        ikekkdcjkfke 3y ago
        Yeah, exposing load bearing wood and glue to the elements requires some extra caution and engineering intuition
      - ikekkdcjkfke 3y ago
        I believe the failure happened in the joint between the wood and steel. The joint was a sandwich with very thin slices and with many nails. Anyone with materials intuition knows that puncturing a material to such a degree weakens it. Mix in constant moisture and single points of failure.. Should have been a couple of big old bolts and some bracings, alternately thicker slices in the sandwich
  - ajross 3y ago
    Isn't that basically arguing "Don't talk to me about statistics, I want to talk about this one specific data point"? Bridges on the whole are pretty clearly better built and safer today then they were 130 years ago. I don't think there's any significant argument to the contrary. There are outliers in both directions, obviously. The old one at this site looks like it was pretty great. The new one sucked. That doesn't say much about why that was true, just that it was.
    - rdtsc 3y ago
      > Isn't that basically arguing "Don't talk to me about statistics, I want to talk about this one specific data point"? For sure, we can each talk about different things. I can talk about ironic things and you can talk about statistics, and we can still be friends! > That doesn't say much about why that was true, just that it was. Well, why do you think it sucked?
    - mannykannot 3y ago
      > Isn't that basically arguing "Don't talk to me about statistics, I want to talk about this one specific data point"? And why not? In this particular case, the statistics did not justify the expectation that this bridge would be at least as robust as the one it replaced. There's a general point to be made about engineering progress, but here we have a case which bucks the trend. Speaking in generalities when the topic is a specific incident is a way of missing the point.
    - Aeolun 3y ago
      On the whole they may be better built, but the same design in steel would likely not have failed? I guess that’s what they’re going for when they say aesthetics had too much of a focus?
      - ajross 3y ago
        > On the whole they may be better built, but the same design in steel would likely not have failed? I don't see how that follows? Lots of steel bridges have failed over the past 130 years. The overwhelming majority of new-built bridges or any material don't fail. People really, really want this to be about "aesthetics" because it confirms their priors about being smarter than the rest of the world or whatever. I'm just saying that's 100% bunk and that there's zero evidence for that hypothesis. Architecture has had a "strong focus on aesthetics" since the very first stones were piled up to make a temple. Let's not get ahead of ourselves here.
- Gare 3y ago
  > Plenty of poorly designed steel bridges from the 19th century have collapsed as well, despite the superior material. Disagree. In late 19th century steel girder bridges were well understood and many of them survive to this day. They were usually replaced due to changed demands (wider roads, heavier loads), not because of failure.
  - loeg 3y ago
    Is this late enough in the 19th century for you? https://en.wikipedia.org/wiki/Tay_Bridge_disaster https://en.wikipedia.org/wiki/Tay_Bridge_disaster
    - tremon 3y ago
      So your convincing evidence for the claim that "plenty of poorly designed steel bridges from the 19th century have collapsed" is a single example of a bridge that collapsed because it was designed "less extensive and robust than [..] previous similar designs"? Or is your claim a mere circular argument, since we can deduce that a steel bridge was poorly designed if it has since collapsed?
      - KptMarchewa 3y ago
        Have a second one. https://en.m.wikipedia.org/wiki/M%C3%BCnchenstein_rail_disaster https://en.m.wikipedia.org/wiki/M%C3%BCnchenstein_rail_disas...
    - throwaway3563 3y ago
      “Plenty”?
im3w1l 3y ago
Well to paraphrase a common saying, it's easy to build a bridge that stands, but it's difficult to make sure that is so optimized that it's on the verge of failing but still somehow stands.
- VelesDude 3y ago
  A good engineer can make a bridge that stands 1,000 years. A great one makes one that can stand 100 years.
  - avery17 3y ago
    These guys must be the best engineers in the world then!
    - VelesDude 3y ago
      Well I... umm... hmmmm...
INTPenis 3y ago
The bridge was built during a trend to build wooden apartment houses here in Sweden, and probably all over Scandinavia. This fad has now passed and there have been several news stories about what a bad idea it was. I guess they were trying to get back to using more natural materials.
- hnbad 3y ago
  There's nothing wrong with wood frame construction, if it's done right. It sounds like they didn't do it right, though.
- sorenjan 3y ago
  There were 250% more apartments built from wood built in 2022 than in 2012. In total 14.4% of all new apartments finished in 2022 used wood. https://www.di.se/hallbart-naringsliv/trahustrenden-nar-nya-hojder-i-staderna/ https://www.di.se/hallbart-naringsliv/trahustrenden-nar-nya-... https://www.tmf.se/bransch-naringspolitik/branschutveckling/statistik/trahus/flerbostadshus/ https://www.tmf.se/bransch-naringspolitik/branschutveckling/...
  - INTPenis 3y ago
    That's true, I had missed how popular they had become. My brother briefly lived in a wooden apartment building around 2017 and after they moved out I noticed a few criticism of the new wooden trend. Then I just lost track of it. The trend goes back to 2014 even, so it wouldn't surprise me if this wooden bridge built in 2012 was part of that whole wave.
bdjsiqoocwk 3y ago
But just think how beautiful it is. Well, was. Sarcasm aside, I see more beauty in doing something well than whatever this was. Are they hiring art students to build bridges now?
boxed 3y ago
Survivor bias.
Sakos 3y ago
Am I the only one who thinks it's strange there isn't a single picture of the bridge pre-collapse on that page?
- ch_sm 3y ago
  there is one though!
twobitshifter 3y ago
You will see wooden covered bridges from 1895 that last a long time too. It is not a material choice problem here, it’s the design and how the members are laid out.

by rdtsc 3y ago

loeg 3y ago

> Engineers in 1895 knew how to use steel trusses and built a bridge that lasted 100+ years It's a little too strong of a claim. Plenty of poorly designed steel bridges from the 19th century have collapsed as well, despite the superior material.

rdtsc 3y ago
> Plenty of poorly designed steel bridges from the 19th century have collapsed as well That's true. But I only meant that particular bridge, which did last for 100+ years. So, when the architects and the engineers go to the archives to relearn a few things, they can focus on the ones which haven't collapsed.
- hellofellows 3y ago
  + why even remove the steel bridge in the first place?
  - speedgoose 3y ago
    You have more pictures on the Norwegian Wikipedia page: https://no.m.wikipedia.org/wiki/Tretten_bru#/media/Fil%3ATretten_bro_(1895).jpg https://no.m.wikipedia.org/wiki/Tretten_bru#/media/Fil%3ATre... The old one wasn’t wide while the new one had two lanes and a normal sized sidewalk.
  - TylerE 3y ago
    Moisture causes corrosion. Rivers produce lots of moisture. Corrosion weakens the steel. It's literally the metal flaking away. All steel corrodes. Even stainless. Once corrosion sets in and the outside of the metal starts to pit, the corrosion speeds up drastically. (The old area vs volume thing, same thing that makes lump coal difficult to ignite while aerosolized coal dust is practically an explosive). Here's a modern US bridge - all steel - that collapsed in Pittsburgh two years ago. In some areas over 80% of the original steel thinkness was gone after 49 years. https://www.youtube.com/watch?v=J-VnWB4fiFk https://www.youtube.com/watch?v=J-VnWB4fiFk
    - Gare 3y ago
      Paint protects steel. A frequently painted steel bridge can last centuries. As always, lack of maintenance and poor design choices (use of corten steel) are the culprit.
      - TylerE 3y ago
        Something like 20% of the bridges in this country are 10 years or more past their design lifetime and mostly not due to be replaced any time soon. You think they're keeping on top of painting every one? Saying preventing corrosion is as easy as slapping on paint is like saying computer security is as easy as not leaking your password. There are a million things that could happen, many of which are outside what any single person could control.
        Gare 3y ago
        I don't know in what poor country you live, but in my country bridges are well maintained and I don't recall a single critical failure. Even though we're one of the poorest EU countries.
        tharkun__ 3y ago
        I don't know in what rich poor EU country you live, but in my "rich country" bridges are basically left to their own devices until a critical problem occurs and then they hastily start repairing it. In some cases they've been repairing bridges for decades that way. Some have recently finally actually been replaced or are being replaced. But nobody is going out and replacing a bridge that isn't on the brink of collapse and held up by "essentially duct tape".
- x3n0ph3n3 3y ago
  To be fair, there have been a lot of advancements in timber and glue -- They just didn't take into account their weaknesses when designing (e.g. Stress that would pull laminated beams apart).
  - Gare 3y ago
    There are always unknown unknowns in trying new designs and/or materials. Even with all the simulations and calculations, nothing beats experience. Sure, novel things should be tried, but in a conservative manner. Overdesign first, then optimize iteratively. Because failure costs lives.
    - mcphage 3y ago
      Glulam isn’t a new material, it’s over 100 years old.
      - Gare 3y ago
        How many 70 m span glulam road bridges have been built in those 100 years?
        ikekkdcjkfke 3y ago
        Yeah, exposing load bearing wood and glue to the elements requires some extra caution and engineering intuition
    - ikekkdcjkfke 3y ago
      I believe the failure happened in the joint between the wood and steel. The joint was a sandwich with very thin slices and with many nails. Anyone with materials intuition knows that puncturing a material to such a degree weakens it. Mix in constant moisture and single points of failure.. Should have been a couple of big old bolts and some bracings, alternately thicker slices in the sandwich
- ajross 3y ago
  Isn't that basically arguing "Don't talk to me about statistics, I want to talk about this one specific data point"? Bridges on the whole are pretty clearly better built and safer today then they were 130 years ago. I don't think there's any significant argument to the contrary. There are outliers in both directions, obviously. The old one at this site looks like it was pretty great. The new one sucked. That doesn't say much about why that was true, just that it was.
  - rdtsc 3y ago
    > Isn't that basically arguing "Don't talk to me about statistics, I want to talk about this one specific data point"? For sure, we can each talk about different things. I can talk about ironic things and you can talk about statistics, and we can still be friends! > That doesn't say much about why that was true, just that it was. Well, why do you think it sucked?
  - mannykannot 3y ago
    > Isn't that basically arguing "Don't talk to me about statistics, I want to talk about this one specific data point"? And why not? In this particular case, the statistics did not justify the expectation that this bridge would be at least as robust as the one it replaced. There's a general point to be made about engineering progress, but here we have a case which bucks the trend. Speaking in generalities when the topic is a specific incident is a way of missing the point.
  - Aeolun 3y ago
    On the whole they may be better built, but the same design in steel would likely not have failed? I guess that’s what they’re going for when they say aesthetics had too much of a focus?
    - ajross 3y ago
      > On the whole they may be better built, but the same design in steel would likely not have failed? I don't see how that follows? Lots of steel bridges have failed over the past 130 years. The overwhelming majority of new-built bridges or any material don't fail. People really, really want this to be about "aesthetics" because it confirms their priors about being smarter than the rest of the world or whatever. I'm just saying that's 100% bunk and that there's zero evidence for that hypothesis. Architecture has had a "strong focus on aesthetics" since the very first stones were piled up to make a temple. Let's not get ahead of ourselves here.
Gare 3y ago
> Plenty of poorly designed steel bridges from the 19th century have collapsed as well, despite the superior material. Disagree. In late 19th century steel girder bridges were well understood and many of them survive to this day. They were usually replaced due to changed demands (wider roads, heavier loads), not because of failure.
- loeg 3y ago
  Is this late enough in the 19th century for you? https://en.wikipedia.org/wiki/Tay_Bridge_disaster https://en.wikipedia.org/wiki/Tay_Bridge_disaster
  - tremon 3y ago
    So your convincing evidence for the claim that "plenty of poorly designed steel bridges from the 19th century have collapsed" is a single example of a bridge that collapsed because it was designed "less extensive and robust than [..] previous similar designs"? Or is your claim a mere circular argument, since we can deduce that a steel bridge was poorly designed if it has since collapsed?
    - KptMarchewa 3y ago
      Have a second one. https://en.m.wikipedia.org/wiki/M%C3%BCnchenstein_rail_disaster https://en.m.wikipedia.org/wiki/M%C3%BCnchenstein_rail_disas...
  - throwaway3563 3y ago
    “Plenty”?

im3w1l 3y ago

Well to paraphrase a common saying, it's easy to build a bridge that stands, but it's difficult to make sure that is so optimized that it's on the verge of failing but still somehow stands.

VelesDude 3y ago
A good engineer can make a bridge that stands 1,000 years. A great one makes one that can stand 100 years.
- avery17 3y ago
  These guys must be the best engineers in the world then!
  - VelesDude 3y ago
    Well I... umm... hmmmm...

INTPenis 3y ago

The bridge was built during a trend to build wooden apartment houses here in Sweden, and probably all over Scandinavia. This fad has now passed and there have been several news stories about what a bad idea it was. I guess they were trying to get back to using more natural materials.

hnbad 3y ago
There's nothing wrong with wood frame construction, if it's done right. It sounds like they didn't do it right, though.
sorenjan 3y ago
There were 250% more apartments built from wood built in 2022 than in 2012. In total 14.4% of all new apartments finished in 2022 used wood. https://www.di.se/hallbart-naringsliv/trahustrenden-nar-nya-hojder-i-staderna/ https://www.di.se/hallbart-naringsliv/trahustrenden-nar-nya-... https://www.tmf.se/bransch-naringspolitik/branschutveckling/statistik/trahus/flerbostadshus/ https://www.tmf.se/bransch-naringspolitik/branschutveckling/...
- INTPenis 3y ago
  That's true, I had missed how popular they had become. My brother briefly lived in a wooden apartment building around 2017 and after they moved out I noticed a few criticism of the new wooden trend. Then I just lost track of it. The trend goes back to 2014 even, so it wouldn't surprise me if this wooden bridge built in 2012 was part of that whole wave.

bdjsiqoocwk 3y ago

But just think how beautiful it is. Well, was. Sarcasm aside, I see more beauty in doing something well than whatever this was. Are they hiring art students to build bridges now?

boxed 3y ago

Survivor bias.

Sakos 3y ago

Am I the only one who thinks it's strange there isn't a single picture of the bridge pre-collapse on that page?

ch_sm 3y ago
there is one though!

twobitshifter 3y ago

You will see wooden covered bridges from 1895 that last a long time too. It is not a material choice problem here, it’s the design and how the members are laid out.