6 ms·

On a long enough timeline we all get rammed by a container ship. I would be interested to know some calculations with factors like: expected bridge lifetime, c

• Retric 3y ago
  Bridges only last for roughly 50 years. Considering such collisions are rare enough to make the news as a memorable event you can workout for yourself that the odds are quite low over a bridges lifespan. They are designed to withstand smaller boat impacts because they occur relatively frequently, but cost vs benefit on rare events that are difficult to mitigate is quite different.
  • yosame 3y ago
    Do you mean 50 years without maintenance? I would be shocked if major bridges weren't designed to last indefinitely.
    • mango7283 3y ago
      I can think of at least 5 famous bridges that are way older than 50 years...
      • Retric 3y ago
        Sure, and there's 100's of thousands of replaced bridges that don't immediately spring to mind. Though to be clear designed to last 50 years isn't the same as saying it will only last exactly 50 years, or that theirs nothing you can do to extend a bridges lifespan if it's replacement is running a little late.
      • bee_rider 3y ago
        If it is a famous bridge, it seems possible that they’ve done some special extra maintenance, replace more wear-and-tear bits that would normally fail. Eventually you probably get the tourist attraction of Theseus.
    • deleted 3y ago
      [deleted]
    • onlyrealcuzzo 3y ago
      Nothing lasts indefinitely...
    • 0xbadcafebee 3y ago
      Depends on the bridge. Steel and concrete bridges can last for at least 100 years. But it depends on the environment, its expected use, the construction, design. Some famous major bridges failed early due to poor design or poor construction, but many still fail due to lack of maintenance. The average age of a bridge in the USA is 43 years. But we also have an epidemic of unmaintained bridges. No bridge made today is designed to last indefinitely. Many different forces will degrade the bridge over time, even with maintenance. Steel stresses weaken it over time. Concrete weathers over time due to salt, chemicals, water, wind, and the steel reinforcements tend to corrode eventually. Stone bridges may last for an exceptionally long time, but their weight and expense makes them only useful in limited applications, typically as small rail overpasses. Ones that were designed for horse and buggy end up slowly failing as heavier trucks and cars in traffic weaken them. The same fate lies for timber bridges. When well maintained they can last for 75 years, but it's expensive and requires certain skills. They were also mostly designed before heavier cars and trucks, and for less traffic. Most famous covered bridges today are being closed to traffic due to increased wear.
      • btilly 3y ago
        According to https://www.fhwa.dot.gov/bridge/ https://www.fhwa.dot.gov/bridge/, the federal government oversees more than 610,000 bridges in the USA. There are a lot of unmaintained small bridges. But I'd hope that the major ones get more attention.
        • 0xbadcafebee 3y ago
          Here's a list of major bridges that need attention (& aren't getting it): https://artbabridgereport.org/state/ranking/top-bridges https://artbabridgereport.org/state/ranking/top-bridges FHWA provides up to $7 Billion in assistance in maintaining bridges. But it would take at least $125 Billion to begin dealing with the structurally deficient bridges in the USA, according to the ASCE Infrastructure Report Card[1]. Add to this the fact that many bridges in the US are privately owned, and it's the responsibility of the bridge owner to maintain them. But guess what's not profitable for a private enterprise? Maintaining bridges. Despite this, train derailments and property damage continue every year due to unmaintained bridge and train infrastructure. The executive has proposed funding for repairs, but as usual, it's not enough[2]. So far they've gotten almost half that number of bridges repaired, and pledged another $300M,[3] which is still just a drop in the bucket of what's needed of the backlog; it doesn't address all the new maintenance that will be needed each year. According to the American Road & Transportation Builders Association, there are 167 million crossings on 42,400 bridges rated in poor condition. [4] [1] https://infrastructurereportcard.org/cat-item/bridges-infrastructure/ https://infrastructurereportcard.org/cat-item/bridges-infras... [2] https://www.nbcnews.com/news/us-news/biden-has-plan-fix-america-s-broken-bridges-it-may-n1267445 https://www.nbcnews.com/news/us-news/biden-has-plan-fix-amer... [3] https://www.whitehouse.gov/briefing-room/statements-releases/2023/04/13/biden-harris-administration-announces-new-investments-repairing-bridges-across-america/ https://www.whitehouse.gov/briefing-room/statements-releases... [4] https://artbabridgereport.org/congressional/map https://artbabridgereport.org/congressional/map
  • b33j0r 3y ago
    Interested in this claim, because it sounds about right, except that I can’t name a bridge constructed in the past 50 years. The bridges we can all name are pushing 100+ right?
    • rrdharan 3y ago
      New York City has had two major recent new bridge replacements that probably about 20M people can name: the Mario Cuomo (formerly Tappan Zee) and the Kosciuszko bridge. I’d argue the Bayonne Bridge raising kinda counts since it was almost a rebuild and more impressive in many ways since it stayed open the whole time. Meanwhile in the San Francisco Bay Area they replaced the Bay Bridge…
      • mannykannot 3y ago
        The Tappan Zee bridge certainly wasn't built with the intention of replacing it after 65 years. Nor, fortunately, was the George Washington bridge.
        • rrdharan 3y ago
          Agreed I was just addressing the parent poster question of whether anyone can name a major bridge built in the last fifty years…
        • 0110101001 3y ago
          > Started on the cheap during the Korean War, the Tappan Zee was deliberately built to last just 50 years. https://www.nytimes.com/2006/01/17/nyregion/a-bridge-that-has-nowhere-left-to-go.html https://www.nytimes.com/2006/01/17/nyregion/a-bridge-that-ha...
          • mannykannot 3y ago
            I can't argue with that!
        • colatkinson 3y ago
  • Hamuko 3y ago
    Doesn't the US have a problem with bridges exceeding their expected service lives?
    • Retric 3y ago
      The boom of bridges after automobiles became common are all running out of time. Yet, paying for a replacement early is also wasteful. So it's an issue, but those bridges where also constructed by a far poorer nation so it's not that big a deal.
      • _heimdall 3y ago
        > but those bridges where also constructed by a far poorer nation That's a must more interesting question when discussing the topic of infrastructure. Sure we've created a lot more money in the last 50 years, but we've also lost a lot of domestic manufacturing. When it comes to something as vital as roads and bridges are we poorer when we have less paper money or when we are less independent in the manufacturing and maintenance of them?
        • lotsofpulp 3y ago
          Money is just a proxy for power, so “poorer” means not able to do something. Note that you are referring to “we” being poorer, and a country’s ability to do (or get) something is not the same as an individual within the country’s ability to do something.
        • Retric 3y ago
          Money is a side issue people are generally a lot more productive than we where 50 years ago and the US population is 50% larger. That means the government has a lot more resources to work with though how it spends them is another question. I think people feel poorer because income inequality increased so much. New homes are huge because new home buyers are the upper end of the wealth curve. Same deal with cars etc. Stuff that targets everyone like normal sized TV's ends up being extremely cheap because revealed preferences show people buy cheap when it's an option.
  • SECProto 3y ago
    > Bridges only last for roughly 50 years. The bridge projects I've been on spec 75 or 100 years. Main difference is better protection/sacrificial depth on ferrous members.
    • LeonB 3y ago
      I remember one of my engineering lecturers giving a good rule of thumb as “your retirement date, plus 10 years”
  • denton-scratch 3y ago
    > 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
  • mannykannot 3y ago
    An obsolete or worn-out bridge is likely to be replaced by another, and in such cases, a risk analysis which potentially comes to different conclusions depending on how often such a replacement occurs is missing the point.