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Holy Shit! I-5 Bridge over Skagit River (near Mount Vernon, Washington) Collapses

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Posts

  • RankenphileRankenphile Passersby were amazed by the unusually large amounts of blood.Registered User, Moderator mod
    Blake T wrote: »
    Well, local news is saying there were no fatalities. And the collapse was caused in part by a oversize load truck hitting part of the bridge while crossing.
    That'll do it alright.
    It shouldn't have.

    This bridge was built in the late 1950s and was known for being pretty much a giant piece of shit with very little structural redundancy. It had been rated functionally obsolete by, shit, whatever organization is responsible for rating bridges, I forget now. It was deemed safe enough, but did not get particularly high marks.

    About 200 yards to the east, the Riverside Drive bridge had been replaced about eight years ago, as the previous bridge was deemed very unsafe. The replacement project took years of surveys and work.

    This should go much, much faster, as the pylons themselves have been consistently rated structurally sound and are well maintained (they were built incredibly tough, as it is pretty common for the river to have log jambs building up and hitting the concrete pylons, and the river frequently floods). All they need to do is replace the roadway and steelwork and hopefully install a better-engineered bridge itself, they don't need to put in whole new groundwork for it. That, plus the fact that it is essentially the main route for ground goods coming to and from Canada, means that it should be replaced relatively quickly.

    8406wWN.png
  • RankenphileRankenphile Passersby were amazed by the unusually large amounts of blood.Registered User, Moderator mod
    Also it is so fucking weird seeing this happen. I grew up very, very near here and worked for like six years at a little shop less than a mile from where this took place. Lots of friends and family still in the area. Glad everyone is safe.

    8406wWN.png
  • DruhimDruhim Registered User, ClubPA regular
    Keep in mind the "functionally obsolete" rating doesn't necessarily mean it was unsound as a structure.

    http://en.wikipedia.org/wiki/National_Bridge_Inventory#Structural_evaluation_scale
    It also classifies bridges as either "structurally deficient" or "functionally obsolete". Neither necessarily implies lack of safety, though that could be a concern as well. "Structurally deficient" means that the condition of the bridge includes a significant defect, which often means that speed or weight limits must be put on the bridge to ensure safety; a structural evaluation of 4 or lower qualifies a bridge as "structurally deficient". The designation can also apply if the approaches flood regularly. "Functionally obsolete" means that the design of a bridge is not suitable for its current use, such as lack of safety shoulders or the inability to handle current traffic volume, speed, size, or weight.

    belruelotterav-1.jpg
  • bloatedhippobloatedhippo Registered User regular
    Whoa, I think I'm taking this bridge up into Canada in a few months.

  • DarmakDarmak RAGE vympyvvhyc vyctyvyRegistered User regular
    Whoa, I think I'm taking this bridge up into Canada in a few months.

    Not now, you aren't

    JtgVX0H.png
  • Blake TBlake T Do you have enemies then? Good. That means you’ve stood up for something, sometime in your life.Registered User regular
    Blake T wrote: »
    Well, local news is saying there were no fatalities. And the collapse was caused in part by a oversize load truck hitting part of the bridge while crossing.
    That'll do it alright.
    It shouldn't have.

    This bridge was built in the late 1950s and was known for being pretty much a giant piece of shit with very little structural redundancy. It had been rated functionally obsolete by, shit, whatever organization is responsible for rating bridges, I forget now. It was deemed safe enough, but did not get particularly high marks.

    About 200 yards to the east, the Riverside Drive bridge had been replaced about eight years ago, as the previous bridge was deemed very unsafe. The replacement project took years of surveys and work.

    This should go much, much faster, as the pylons themselves have been consistently rated structurally sound and are well maintained (they were built incredibly tough, as it is pretty common for the river to have log jambs building up and hitting the concrete pylons, and the river frequently floods). All they need to do is replace the roadway and steelwork and hopefully install a better-engineered bridge itself, they don't need to put in whole new groundwork for it. That, plus the fact that it is essentially the main route for ground goods coming to and from Canada, means that it should be replaced relatively quickly.
    I'm assuming they hit the structural steel not the pylons. Is that what they hit?

    If the hit the steel at the collapse point is a truss style construction which while massively efficient it has very little redundancy.

    Truss construction means that the design moment is turned into compression and tensile loads and the top and bottom respectively.

    Removing a vertical post by running into it will make the members carry moments which they are under designed to do and will collapse in the manner shown in the picture (at the crash site)

    Unless it ran into a different part of the bridge.

  • WeaverWeaver Who are you? What do you want?Registered User regular
    Some of the I5 corridor rail line has similar designed bridges. Luckily trains don't swerve, much.

  • Blake TBlake T Do you have enemies then? Good. That means you’ve stood up for something, sometime in your life.Registered User regular
    Here is a diagram showing what happens if you remove (or damage the beam so it can no longer support its required loads.

    586EE4C4-76D5-41ED-86D3-FD63411C17D8-2101-000000B46F85180E_zps1da9ebcc.jpg

  • Blake TBlake T Do you have enemies then? Good. That means you’ve stood up for something, sometime in your life.Registered User regular
    That plot shows bending moment. Which is best described as the force required to resist rotation. (How it is hard to hold a stick at one end versus supporting it at either end) increasing your moment is one way to increase stress.

  • Donovan PuppyfuckerDonovan Puppyfucker A dagger in the dark is worth a thousand swords in the morningRegistered User regular
    You need to put a little hat on your Dalek for when you're educating people.

  • DarmakDarmak RAGE vympyvvhyc vyctyvyRegistered User regular
    You need to put a little hat on your Dalek for when you're educating people.

    Don't forget an596n0.gif

    JtgVX0H.png
  • The GeekThe Geek Oh-Two Crew, Omeganaut Registered User, ClubPA regular
    I'm in Georgia right now.

    BLM - ACAB
  • knitdanknitdan In ur base Killin ur guysRegistered User regular
    edited May 2013
    Wrong thread

    knitdan on
    “I was quick when I came in here, I’m twice as quick now”
    -Indiana Solo, runner of blades
  • BucketmanBucketman Call me SkraggRegistered User regular
    The Geek wrote: »
    I'm in Georgia right now.

    America or USSR?

  • JoeUserJoeUser Forum Santa Registered User regular
    The Geek wrote: »
    I'm in Georgia right now.

    I guess that rules you out as a suspect ... for now.

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