Mention was made of steel ties in tunnels. It is hard to keep a tunnel dry, road bed and ties suffer so steel ties overcome part of the challenge. Steel ties are a little like an upside down baking tray and help to hold their support under them. The rail is insulated by hard pads but if the ballast is wet there can be some current leakage. Concrete ties have insulating pads also as the rail fixing is tied into the reinforcing steel. As well these pads are under the clip where it holds the foot of the rail down.
MC’s comment on subgrades brings up a point: it really isn’t wise to just slip a concrete tie in in place of a wooden one, or even relay a section of track with concrete, without considering the whole track structure. The track structure starts well down in the subgrade, and continues right up through the rail head, and it all must work together as a system. The wood tie system has been around a long time, and a lot has been learned (mostly by experience) about how to make the whole thing work well, to hold alignment as well as support the loads. Concrete ties are stil – in my humble opinion – somewhat in the experimental stage of this (which is not to say they don’t do a good job; they do!). In fact, the track structure has to work together with the car or engine – trucks, bolsters, the whole bit – to give good tracking and a good ride. One place this interaction can be seen is that if the track structure is made less flexible, then you have two choices: either the track geometry must be very much better, or the car/engine suspension must be more forgiving. But if the car/engine suspension is more forgiving, then you have to add in damping to prevent car roll and probably truck hunting… and so on! 'tain’t quite as simple as it looks…
I’m actually surprised there isn’t more concrete used in the US by now. When I went through all of Canada in the early 80’s, there was already a large portion of mainline using concrete. I figured the US would be right behind, but it doesn’t seem to have caught on here as much. Then on the other hand, I’ve seen them used in really odd places… There’s some very small yards that aren’t even used in the L.A./Long Beach Harbor, that were redone with concrete during the big overhaul.
Dave
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CP used steel ties when they improved the clearance in the Spiral Tunnels and uses them where they need to reduce the amount of a track raise on new bridges. Haven’t heard the S&C people swearing too much, yet.
FEC was an early pioneer of concrete ties. they design and made their own for many years and now purchase commercially.
As an offshoot of this discussion, a recent article in Machine Design magazine talked about composite rebar which will be used in road bridge decks to reduce corrosion, lenghtening life spans. This technique could be utilized in
concrete ties at grade crossings and ocean front property further enhancing the ties.
Lots of concrete ties used out west. The mainline over the Techapi is cement except for switches and sidings. Also The Cajon Pass. I’ve talked to track crews who say they’re fine on the straight but don’t think they last as long on curves. Also they are twice as heavy as timber.
In UK and places in Europe, there is the development of the concrete sleeper. It’s called slab trtack, where a “runway” of concrete is used, with the rails bedded in on fastners, allowing rails to be replaced, whilst the track-bed remains. This is very expensive, but has a very long life. It tends to be used in special cases such as tunnels, where there is a lot of water-logging and/or where track repairs would cause repeated delays. As maintainence is less, the benefits are obvious and that benefit must be off-set against the additional cost.
Eric Stuart
Eric - slab track is NOT the panacea you think it is. It has drawbacks and works best in confined areas. See remarks about Pac-Trak in another thread…Notably, the huge failure on the US Army COE/ ATSF project in Kansas at the Eldorado Line Change.
Speaking of Concrete and Wooden Ties I read in Trains a while back (sorry don’t remember which issue) that Plastic Ties are starting to come into play. They are suposed (spelling) to overtake both the Wooden, and Concrete Ties in certain design aspects, and locations. I do wonder whats next…Ceramic Ties?
Last few times chasing trains I discovered that both the UP mainline thru Pomona (from the 73 out to near Mountain Ave, all lines) and the BNSF mainlines thru Yorba Linda (from Imperial Hwy east to ?) were both being replaced with concrete ties. I suspect that as all older mainlines are upgraded all wooden ties will eventually end up in your local gardening supply store waiting to become planters and walkways.
mudchicken Posted: Today, 11:21:02
QUOTE: Originally posted by Eric Stuart
In UK and places in Europe, there is the development of the concrete sleeper. It’s called slab trtack, where a “runway” of concrete is used, with the rails bedded in on fastners, allowing rails to be replaced, whilst the track-bed remains. This is very expensive, but has a very long life. It tends to be used in special cases such as tunnels, where there is a lot of water-logging and/or where track repairs would cause repeated delays. As maintainence is less, the benefits are obvious and that benefit must be off-set against the additional cost.
Eric Stuart
Eric - slab track is NOT the panacea you think it is. It has drawbacks and works best in confined areas. See remarks about Pac-Trak in another thread…Notably, the huge failure on the US Army COE/ ATSF project in Kansas at the Eldorado Line Change
Mudchicken:
Several times in the last year or so, I have noticed in photos of "ne
Sam:
(1)The asphalt underlayment has been a work in progress, primarilly pioneered by University of Kentucky’s Dr. Jerry Rose and others through AREMA as a way of minimizing the capilary actions of water in the ballst and the subballast. (Get rid of mud pumping in the ballast and below) along with spreading out the loading in the foundation fill. In answer to your question, it would be yes (partially, the asphalt underlayment has other possible advantages beyond keeping the mudmonster at bay)…
(2) In the late 1970’s, USACE built a dam that required re-locating the ATSF Transcon at ElDorado KS…The fill has been rebuilt at least three times after failure and the track structure has been rebuilt at least 4 times (below the rail) since then. Among other things, during the second rebuilding, a fly-ash and grout injection system were used to try and stabilize the fill. Concrete ties came along later and broke the cap severely and some of the stabilized material was pulverized to dust. After the fill was rebuilt for the third time (with imported material that did not have the high organic content of the native local soil), it was dictated by the Chief Engineer that wood ties would only be used here.
Before this all happened, PacTrack/Slab track was tried twice with disaastrous results. Whats left of the PacTrac is the suitable rip-rap fill material now found on the sides of the base of the excavation fill.
USACE and AREMA (www.AREMA.org) have well documented what happened here over the years.
[banghead][banghead][banghead]
I shot a bunch of green UP mow cars in Ogden with steel formed ties on them. I think them odd but there they were. They look, from the roadside to be punched by a massive press and the splay ( the sides are not square like wood or cement ) helps to hold them into the application. The ends are funky however and got a laugh out for me . . .
From what has been said after my previous note, it would seem that the problem is not slab track per se but what was put down as the foundation. If the foundation under the track is poor, no track will be a success! True, slab track does seem most successful in limited spaces like tunnels. I imagine tunnel applications may be more stable underneath, as well.
But we must never forget low-tech solutions. It seems much easier to change a single or a few wooden sleepers, whereas normally at least a complete panel is replaced with concrete sleepers. The London Underground remained faithful to wooden sleepers for a long time after other railways moved on, as the limited space often available available and the limited time for manouvering heavy equipment meant that men could change the odd sleeper by hand more efficiently. I think this is still true in many cases. What is the situation on US subway lines?
E Stuart
The greatest amount of subway track in the is on the New York City Transit System’s subway lines, and most of this appears to be treated highest quality wood stub ties installed in place and held off the concreter tunnel floor by cribbing, and then formed concreted is poured under and around them, the cribbing removed, and then concrete poured to fill the voides left by the cribbing. The poured concrete leaves and contiuous dranage ditch in the center, which is deep enough for anyone caught by an on-coming train to simply fall down into the center ditch and have the entire train pass over him/her. And emerge alive The rails are attached to the ties by screw fasteners. Not much resilience in this construction, which can be considered a form of slab track and has been in use for over 50 years. And it lasts about 50 years, ties and all. Where vibration abatement is required, the underlying slab itself, reinforced, is “floated” and very, very dense glass fiber or neoprene mounts. The NYCTA has has a long-range program of replacing all original ballested track in tunnels with this “concrete roadbed.”
I used to live in Cartersville, GA (now in Marietta, GA, near Atlanta). All my life I have grown up watching the main line that runs from Atlanta to Chattanooga (operated by CSX). It is completely concrete now, except many of the sidings in all the small towns are still mostly wood. (I remember several years back when I was younger being at a car show in downtown cartesville and watching the MOW guys replacing the wood w/ concrete ties, needless to say I was much more into the seeing this than the cars !)
I think they are making him put up his toys and clean up his flight deck…something about protecting democracy and freedom on the high seas!
Ed
The ElDorado situation is, of course, the classic example to illustrate the point which I made in my previous post: the ties/slab/whatever are only part of the equation. Eric is partly right in his comment ‘if the foundation under the track…’ – but only partly. Most subgrades and ballast systems are designed, quite deliberately, to flex. Perhaps not a great deal, but they do flex. If they are clean material, they won’t be affected by the mudmonster, as MC puts it (if they are, well…!). If the subgrade can flex, then the rail can be a little lighter and the car suspensions a little stiffer and have somewhat shorter travel. If the subgrade is rigid enough to support a slab, and the slab is strong enough to support the stress of distributing a load, then a slab will work well enough – hence in tunnels, where it is not uncommon to have rock (pretty rigid) not far below the track, slabs work well – at the expense of more shock on the equipment. However, placing slab trackwork on a ballast and subgrade intended for ties (concrete or otherwise) will surely result in the slab cracking, unless it is a real monster.
Track is a system, not an item. The track system extends from the native ground to the rail head, and must interface properly with the suspension system intended to ride on it. Failure to treat the track as a system will result in… failure.
Concrete ties vs. wood ties? Concrete ties are great on tangent track. On curves they are murder on the rails. The rail wears out a lot faster because there is no flex with concrete. Of course they (Concrete) are also a source of job security if you happen to work on a curve gang.[:D] It’s also mind numbingly boring if you’re forced to work in a concrete tie plant.
I, myself, prefer cement ties over wooden ties because wood gets eaten more easily than Cement and the cement ties look better and hold a better strength than the wooden ones.
Rob