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  1. #1
    Lanterne Rouge More Cowbell's Avatar
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    Does your bike bridge have earrings?

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  2. #2
    Senior Member Retro Grouch's Avatar
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    Might that have been designed by the same guy who did the I-35 bridge?
    My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.

  3. #3
    Lanterne Rouge More Cowbell's Avatar
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    I think they used the same engineering consultant out of San Francisco.

    Here is a clip of the cable prior to the collapse.
    1982 Ciocc World 77
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  4. #4
    Senior Member Northwestrider's Avatar
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    The video surprised me, wow.

  5. #5
    coprolite fietsbob's Avatar
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    On June 8, 2012, a summary report[13] of the investigation was released in which the failure was attributed to wind-induced "cable vibrations that induce damaging stress range cycles at fatigue sensitive details in the cable diaphragm plates." The effect of cable vibrations caused by wind was not included in the original design package for the bridge.[14]
    background : http://en.wikipedia.org/wiki/Martin_Olav_Sabo_Bridge

    the bridges here is a truss, 1, and center lift, 2.. not cable suspension , and its for cars and trucks and not a bike bridge ,

    though cyclists can ride across the river1, and the bay2, on the right side of the 2 lanes. on US 101.


    but then again it does not fall below ZeroC more than a week or 2 here either
    Last edited by fietsbob; 04-16-14 at 11:03 AM.

  6. #6
    Senior Member MEversbergII's Avatar
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    A Stockbridge damper. Neat little things.

    M.

  7. #7
    coprolite fietsbob's Avatar
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    Stockbridge damper - Wikipedia, the free encyclopedia.. not exactly, there is just a weight hanging from a shackle..
    as I see the design tha 2 weights in mr Stockbridges design have a different damping effect ,

    as the short cable connecting them can be tuned , by length if that crossbar, to have a frequency of it's own

    & Inertia .. counteracting out of phase perhaps?

    Napkin engineering level .. the inertial mass of the weight , i suspect is benefitting from the wooden rather than a metal clamping block ..
    Last edited by fietsbob; 04-16-14 at 03:20 PM.

  8. #8
    The Recumbent Quant cplager's Avatar
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    Quote Originally Posted by More Cowbell View Post
    I think they used the same engineering consultant out of San Francisco.

    Here is a clip of the cable prior to the collapse.
    Do you have a video of the cable afterwards? I wouldn't have guessed the weight would change it that much...
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  9. #9
    Senior Member delcrossv's Avatar
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    Quote Originally Posted by cplager View Post
    Do you have a video of the cable afterwards? I wouldn't have guessed the weight would change it that much...
    It's probably the attachment point that raises the resonant frequency of the cable- a "false/virtual endpoint".
    Lightning P-38 / M5 M-Racer/Ryan Vanguard

  10. #10
    coprolite fietsbob's Avatar
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    The light rail resumed service on February 24, 2012,
    there a metro rail track on the bridge too?

  11. #11
    The Recumbent Quant cplager's Avatar
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    Quote Originally Posted by delcrossv View Post
    It's probably the attachment point that raises the resonant frequency of the cable- a "false/virtual endpoint".
    I would assume the effectiveness of that depends on the weight being added. My non-skilled eye thinks the size of the weight was relatively small compared to three mass of the cable..

    All that being said, I'm guessing my eye is wrong as they bothered to add it to the cable.
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  12. #12
    Senior Member
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    i wonder how long they think that untreated piece of wood will last... i know i do.

    or maybe it's just part of some school kid's science project. IDK.

  13. #13
    Senior Member wahoonc's Avatar
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    Quote Originally Posted by hueyhoolihan View Post
    i wonder how long they think that untreated piece of wood will last... i know i do.

    or maybe it's just part of some school kid's science project. IDK.
    Looked like ACQ treated to me, that stuff is a light lighter in color than the old stuff. I was more concerned with what would happen if the shackle pin comes loose. Needs to be wired (moused).

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  14. #14
    Senior Member rydabent's Avatar
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    In Omaha there is a hiker biker bridge over the Missouri river that is a suspension bridge. Even in light winds it is amazing how much the suspension cables vibrate and buzz. As of yet anyway the cables on this bridge do not have dampeners like those shown. Considering the vibration tho, it might be a good idea.

  15. #15
    Lanterne Rouge More Cowbell's Avatar
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    Quote Originally Posted by cplager View Post
    Do you have a video of the cable afterwards? I wouldn't have guessed the weight would change it that much...
    I didn't notice the vibration in the stay when I took the picture. There was a pretty good wind that day (15 - 20mph)
    1982 Ciocc World 77
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  16. #16
    Lanterne Rouge More Cowbell's Avatar
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    Quote Originally Posted by fietsbob View Post
    there a metro rail track on the bridge too?
    This bridge is strickly bike and pedestrian. It bridges a divided 4 lane and a light rail line.
    1982 Ciocc World 77
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  17. #17
    Lanterne Rouge More Cowbell's Avatar
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    Quote Originally Posted by hueyhoolihan View Post
    i wonder how long they think that untreated piece of wood will last... i know i do.

    or maybe it's just part of some school kid's science project. IDK.
    The wood was treated. This didn't have a secondary attachment point so is a risk for the weight being dropped onto the highway if the wood attachnment fails.
    1982 Ciocc World 77
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  18. #18
    Senior Member RPK79's Avatar
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    We have a fancy new $130,000,000 bridge down here in Hastings that was finished last December and the cosmetic finish on the concrete is flaking off. A mark of fine craftsmanship if I ever saw one.

  19. #19
    Lanterne Rouge More Cowbell's Avatar
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    Quote Originally Posted by RPK79 View Post
    We have a fancy new $130,000,000 bridge down here in Hastings that was finished last December and the cosmetic finish on the concrete is flaking off. A mark of fine craftsmanship if I ever saw one.
    Minnesota sure knows how to build bridges.
    1982 Ciocc World 77
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