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post #21 of 28 Old 07-12-2018
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Re: Heatwaves and Drawbridges, Etc

Article in this week's paper mentioned that a critical Amtrak swing bridge (over the Hackensack Rivier, IIRC) just west of NYC literally carries 450 trains per day. And that when it has to be opened, it gets stuck literally one in seven times, and has to be nudged closed again with a sledgehammer.

And this is considered normal daily operations.

Everyone seems to think that when it finally gets stuck for good, then they'll be able to get public funding and leave it closed for five or ten years while they are replacing it.
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post #22 of 28 Old 07-12-2018
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I like Minnewaska's subtle and repeated attempt to remind everyone that climate change is not involved here -- even though I don't think anyone suggested that it was.
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post #23 of 28 Old 07-12-2018
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Re: Heatwaves and Drawbridges, Etc

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I like Minnewaska's subtle and repeated attempt to remind everyone that climate change is not involved here -- even though I don't think anyone suggested that it was.
That's exactly what the article says.

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Climate change can pose some unexpected challenges to infrastructure.


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post #24 of 28 Old 07-12-2018
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Re: Heatwaves and Drawbridges, Etc

Railroads are sensitive to temperature change. Back when you had 39’ sections of “stick” rail bolted together they each had a wee bit of expansion. But even back then a heat wave would cause the rail to buckle (famous derailment in PA killed quite a few) or a cold snap would cause the rail to “pull apart”. Continuously welded rail eliminates the joints and makes the rail more susceptible to temperature change. For this reason welded is heated when it is laid to get it to a specific temperature before it is finally spiked down. Some other measures are also taken but not being a rail engineer and not paying sufficient attention I forget. I recall expansion joints every mile or so.

Lift and swing bridges are a PITA. There are various safety measures, The but joints have “point detectors” to assure the rail aligns correctly, as donswitches. There is additional (guard) rail between the running rails so that if the damn thing jumps the track it will stay near the track.

Electrified railroad has one of two types of overhead wire systems. The newer is “constant tension” where the wire has weights on one end which raise and lower with temperature change. This is great till the wire breaks and you dump a mile of wire. Then there is the fixed placement type which most of the NEC uses. The wire is fixed at each pole, tension goes up and down with temperature. Cold snaps make the wire brittle and it can snap with high tension. Excessive heat is worse, the wire sags and the locomotive contact can rip the wire down. During excessive heat trains were issued “slow orders” to avoid this mess. Bridges typically fail during heat as they are an obvious place for the elongation of rail or wire to manifest alignment problems.

I once worked on a proposed people mover using ski lift technology. The wire mechanisms have a gismo, a weight on a wire, that pulls on a bull wheel, so as to keep a constant tension on the traction wire. So if the temperature gets too hot the skin-lifts won’t operate, but I guess by then it’s moot anyway.

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post #25 of 28 Old 07-12-2018
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Re: Heatwaves and Drawbridges, Etc

If the asphalt is collapsing all the way to the truck axles I think the roadbed beneath the paving is at fault. Most asphalt roads are rarely more than 4" thick with the base beneath it being compacted rock or road base which actually provides the support for the paving. Asphalt getting soft from heat is not a new phenomenon and the grooves from the traffic in asphalt surfaces is caused by trying to make the paving last too long. In the land of freeze and thaw you are lucky to get 4 or 5 years from an asphalt road without rotomilling and a new layer of pavement. I think politics has more to do with road problems than does climate change, whether natural or man caused.

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post #26 of 28 Old 07-13-2018
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Re: Heatwaves and Drawbridges, Etc

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Originally Posted by SeaStar58 View Post
Why are some changing heat bound hinges on the draw bridge into an expansion joint issue? The problem being reported on the bridge was the hinges binding from the heat making it so the bridge would lock up. They mentioned that there had not been enough thought giving to swelling sideways in the hinges.


Ahh, that makes sense! The reason I conflated it is simply because I designed bridges for a living and we never considered side to side expansion on any of my projects. It was always longitudinal. But what you say makes perfect sense. In that case, I suppose those designers, like me never accounted for it.

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Last edited by Sal Paradise; 07-13-2018 at 10:05 AM.
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post #27 of 28 Old 07-13-2018
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Re: Heatwaves and Drawbridges, Etc

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That's exactly what the article says.
The way some of your comments read, it sounded like you were responding to what other people in this discussion had said (or, had not said) regarding climate change, instead of a statement from the article. But anyway, at least I wasn't misunderstanding your subtle rejection of climate change.
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post #28 of 28 Old 07-13-2018
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Re: Heatwaves and Drawbridges, Etc

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.....But anyway, at least I wasn't misunderstanding your subtle rejection of climate change.
Yes you are. I'm not rejecting climate change, which is probably why you keep referring to it as subtle. I'm rejecting that this bridge issue has anything to do with it. I'm rejecting that the article doesn't make the case for it. Chicago has been hotter and for longer than this episode and the bridge has stuck before. Perhaps it will start to happen more frequently, but the article doesn't touch that point. It solely plays to those that will latch onto anything climate related, so they can sell advertising.

Climate change is real. What we're doing about it, which amounts to a waste of time and money, is the problem.
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