Green Line Expansion Beyond Lechmere

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Re: Green Line Expansion Beyond Lechmere

Postby orange1234 » Tue Sep 25, 2018 5:37 pm

Arlington wrote:Do we happen to know yet whether they will be using concrete sleepers or wooden ones on the GLX?

As we speculate on whether today's commuter rail tracks could become the future GLX tracks 1 limiting question could be as simple as the weight of the rail and the choice of sleeper material.


I have a feeling it'll all be wooden as concrete ties amplify the noise of wheels.
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Re: Green Line Expansion Beyond Lechmere

Postby BandA » Wed Sep 26, 2018 7:33 pm

Didn't MBTA (or Amtrak) have a bad experience with cement ties? And the cement slabs used on the Red Line Alewife extension?

My limited understanding is that wood does better with freeze/thaw cycles, and cement is needed to retain the gauge precisely for high-speed rail (NEC).
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Re: Green Line Expansion Beyond Lechmere

Postby MBTA3247 » Wed Sep 26, 2018 8:45 pm

Several railroads have had bad experiences with concrete ties. As I recall, the Braintree Line had a major problem with them around 20 years ago. My understanding is that it's an issue with bad batches of concrete.
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Re: Green Line Expansion Beyond Lechmere

Postby CRail » Thu Sep 27, 2018 12:37 am

The T seems to have abandoned them. Old Colony had a major tie replacement project relatively recently (and those lines are relatively new anyways), and any time there's a track replacement where concrete ties are involved, at least on the transit side, wooden ties are being placed.

It was once explained to me by a civil engineer that concrete performs well under compression but terribly under tension. Concrete ties are enforced with rebar, which expands and contracts with the temperature. Steel also expands when it rusts, creating tension on the concrete causing it to crumble.
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Re: Green Line Expansion Beyond Lechmere

Postby l008com » Thu Sep 27, 2018 12:56 am

With all the plastic we throw away and recycle, you'd think they'd come up with some useable plastic ties or something like that
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Re: Green Line Expansion Beyond Lechmere

Postby Arlington » Thu Sep 27, 2018 9:33 am

The only choice for GLX is wood or concrete, and it sounds like the MBTA system-wide answer is "wood" (making it theoretically possible that the temporary CR wood ties and CWR rails could MAYBE be repurposed for GLX outbound, if they can grind the rail to transit specs)

OFF TOPIC: Plastic/Composite ties are available, and have been slowly moving to market since 2011 made from car-bumper plastic scrap. It looks like they're too expensive to use in regular running track applications(like the CR & GLX through Somerville), and cost-limited to uses where the expense of changing ties is the real life cycle cost (tunnels, bridges, crossings, embedded, turnouts, and diamonds)
Last edited by CRail on Thu Sep 27, 2018 11:38 pm, edited 1 time in total.
Reason: Unnecessary quote removed.
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Re: Green Line Expansion Beyond Lechmere

Postby troffey » Mon Oct 01, 2018 2:51 pm

CRail wrote:The T seems to have abandoned them. Old Colony had a major tie replacement project relatively recently (and those lines are relatively new anyways), and any time there's a track replacement where concrete ties are involved, at least on the transit side, wooden ties are being placed.

It was once explained to me by a civil engineer that concrete performs well under compression but terribly under tension. Concrete ties are enforced with rebar, which expands and contracts with the temperature. Steel also expands when it rusts, creating tension on the concrete causing it to crumble.



The Old Colony lines concrete ties failed after about ten years, which the T blamed on manufacturer error:
https://cdn.mbta.com/uploadedfiles/Abou ... tation.pdf

I believe they've gone strictly with wood ties since.
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Re: Green Line Expansion Beyond Lechmere

Postby jonnhrr » Thu Oct 04, 2018 4:20 pm

Seems that just about every country in the world outside the US is able to use concrete ties without issues. I wonder why.

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Re: Green Line Expansion Beyond Lechmere

Postby Bramdeisroberts » Thu Oct 04, 2018 5:33 pm

Concrete inevitably fractures and spalls in any situation where it's exposed to moisture and frequent freeze/thaw cycles, whereas wood is far more resilient under those same conditions.

Most countries where concrete ties are the standard have neither the harsh, wet, and cold winters of the Northeast and Canada nor the ample access to cheap wood, and so instead they go with concrete. Here, we have far harsher winters than most of Europe does, and far better access to cheap lumber, and so wooden ties are the standard.

It's not just the northern US and Canada, though, as JR Hokkaido and the Swedish/Norwegian railway systems all seem to also use wooden ties extensively on their main lines for the exact same reasons.
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Re: Green Line Expansion Beyond Lechmere

Postby jwhite07 » Fri Oct 05, 2018 7:04 am

There is such a thing as a steel crosstie. In fact, there are some in use in our area - the west end of the yard lead into CSX's intermodal yard in Worcester has steel ties installed a few years ago during the yard's expansion. I suppose they'd require some kind of insulating pads under the rail in signalized or electrified territory, not clear on how that works.
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Re: Green Line Expansion Beyond Lechmere

Postby Bolo42 » Fri Oct 05, 2018 9:37 am

I've actually done some research on this.
Concrete ties have difficulty in the Northeast due to rail-seat deterioration (the area of the tie directly under the rail). When fine particles infiltrate this area, the moisture, friction and freeze/thaw cycle causes the concrete to crumble, ultimately exposing the pre-stressed reinforcing wires causing them to rust and loose tension, etc. Otherwise concrete ties would be more economical in the Northeast due to their increased durability over wood.
Some current research is looking at using higher grade concrete for the top portion of the ties for one solution. Otherwise, unless the issue is caught and fixed with epoxy before the tie deteriorates too much (the deformations in track geometry caused by rail-seat deterioration can be caught with track geometry cars) the tie needs to be replaced.
Of course, it doesn't help that when concrete ties were first designed in the US, they were done from a manufacturing perspective to make them easier to manufacture, rather than an engineering perspective to be able to adequately withstand the forces that act upon them.
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Re: Green Line Expansion Beyond Lechmere

Postby artman » Tue Oct 09, 2018 1:41 pm

jonnhrr wrote:Seems that just about every country in the world outside the US is able to use concrete ties without issues. I wonder why.

Jon


Wood is generally unavailable for many purposes in many western European countries due to forests having been cut down centuries ago.
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Re: Green Line Expansion Beyond Lechmere

Postby Arlington » Tue Oct 09, 2018 2:27 pm

^ Exactly. Europeans don't have the forests, and so tend not to use wood where we would: telephone poles, rail ties, housing-framing. And North America has gotten good at growing, pressure-treating, and engineering wood products as a result.
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Re: Green Line Expansion Beyond Lechmere

Postby EuroStar » Wed Oct 10, 2018 7:23 am

We also abuse our ties (and rails) more and generally do less maintenance on the right of way than what is typically done in Europe. European cars, both passenger and freight are substantially lighter than ours. Their train consists are shorter, with freight trains rarely exceeding 40 cars in length. They also pay much more attention to good drainage there. The ballast typically consists of larger aggregates than what we use here and gets cleaned by ballast cleaners that remove broken down stones every so many years. In the US most railroads have never heard of ballast cleaners, much less used one. As Bolo42 points out water is the enemy of the concrete ties and in order to achieve their claimed 50 years life those ties need good drainage.
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Re: Green Line Expansion Beyond Lechmere

Postby Arlington » Tue Oct 16, 2018 4:29 pm

Complete GLX Construction Update (FMCB Oct 15) Mostly shows the phases of moving the CR south/west so that the ROW can be widened and walled on the future CR side (and then subsequent phases on the GLX side).
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