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> Bridges only last for roughly 50 years. https://en.wikipedia.org/wiki/The_Iron_Bridge https://en.wikipedia.org/wiki/The_Iron_Bridge Opened in 1781, still in

> Bridges only last for roughly 50 years. https://en.wikipedia.org/wiki/The_Iron_Bridge https://en.wikipedia.org/wiki/The_Iron_Bridge Opened in 1781, still in service and perfectly safe. Of course, there are no container ships nearby. But I reckon you could sail a container ship under it, given enough water; and to damage the bridge supports, the container ship would need climbing equipment. 1781 isn't many years after the Declaration of Independence.

throwaway48476 3y ago
Notice it's a pedestrian and not a vehicle bridge as well.
notahacker 3y ago
If there was enough water for the 48m beam, 24m airdraft container ship that just collapsed the Baltimore bridge to attempt to navigate under the 30m span, 16m high Iron Bridge I don't think the bridge would stand a chance...
- denton-scratch 3y ago
  Heh! OK, so I'm wrong about being able to sail a container ship under the Iron Bridge. It didn't take motor traffic, because when it was built, there was no motor traffic. But the claim I replied to was about all bridges. But it used to take vehicle traffic: the WP article says "In 1934 it was designated a scheduled monument and closed to vehicular traffic."
  - Retric 3y ago
    And all bridges do last roughly 50 years. Look at all bridges and figure out the average, median, or mode lifespan is reasonably close to 50 years +/- depends on where you draw the lines. A tiny fraction reach 500 and so far none that we know of have hit 5,000 though there’s a few possibilities.
    - ClumsyPilot 3y ago
      This is really bad math, your calculation is not about bridge strength / longevity but about how many bridges we built recently. For example, if tomorrow we decided to build a new bridge next to every old bridge, average lifespan would half.
      - Retric 3y ago
        current age != lifespan https://en.wikipedia.org/wiki/Life_expectancy https://en.wikipedia.org/wiki/Life_expectancy > if tomorrow we decided to build a new bridge next to every old bridge, average lifespan would half. The only way building a bunch of new bridges changes lifespan is if we changed how they where built. Figuring out lifespan rather than age is at best an approximation after looking at the bridges that didn't survive and the condition of bridges that do, but the uncertainty is low.
Retric 3y ago
I'll raise you: https://en.wikipedia.org/wiki/Arkadiko_Bridge https://en.wikipedia.org/wiki/Arkadiko_Bridge But that's talking about the tail end of the bell curve not it's center.
- vikingerik 3y ago
  That's also a much smaller scale. 22 ft long, 13 ft high, and carries only foot traffic or maybe horses. Much less is demanded of that structure than of a river-spanning mile-long truck-carrying bridge.

throwaway48476 3y ago

Notice it's a pedestrian and not a vehicle bridge as well.

notahacker 3y ago

If there was enough water for the 48m beam, 24m airdraft container ship that just collapsed the Baltimore bridge to attempt to navigate under the 30m span, 16m high Iron Bridge I don't think the bridge would stand a chance...

denton-scratch 3y ago
Heh! OK, so I'm wrong about being able to sail a container ship under the Iron Bridge. It didn't take motor traffic, because when it was built, there was no motor traffic. But the claim I replied to was about all bridges. But it used to take vehicle traffic: the WP article says "In 1934 it was designated a scheduled monument and closed to vehicular traffic."
- Retric 3y ago
  And all bridges do last roughly 50 years. Look at all bridges and figure out the average, median, or mode lifespan is reasonably close to 50 years +/- depends on where you draw the lines. A tiny fraction reach 500 and so far none that we know of have hit 5,000 though there’s a few possibilities.
  - ClumsyPilot 3y ago
    This is really bad math, your calculation is not about bridge strength / longevity but about how many bridges we built recently. For example, if tomorrow we decided to build a new bridge next to every old bridge, average lifespan would half.
    - Retric 3y ago
      current age != lifespan https://en.wikipedia.org/wiki/Life_expectancy https://en.wikipedia.org/wiki/Life_expectancy > if tomorrow we decided to build a new bridge next to every old bridge, average lifespan would half. The only way building a bunch of new bridges changes lifespan is if we changed how they where built. Figuring out lifespan rather than age is at best an approximation after looking at the bridges that didn't survive and the condition of bridges that do, but the uncertainty is low.

Retric 3y ago

I'll raise you: https://en.wikipedia.org/wiki/Arkadiko_Bridge https://en.wikipedia.org/wiki/Arkadiko_Bridge But that's talking about the tail end of the bell curve not it's center.

vikingerik 3y ago
That's also a much smaller scale. 22 ft long, 13 ft high, and carries only foot traffic or maybe horses. Much less is demanded of that structure than of a river-spanning mile-long truck-carrying bridge.