RETAINING WALL DESIGN FOR RAILWAY LOADS 3

Your capslock key is stuck.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

I TYPE LIKE I WRITE...BLOCK LETTERS ALL CAPS. ACQUIRED HABIT FROM UNIVERSITY HOMEWORK REQUIREMENTS.

I would treat them as a series of point loads with the effects possibly overlapping. As far as all caps go, with internet and fidonet or others that preceded it, CAPS are considered as shouting (internet etiquette).

Dik

Draw your assumed situation, including loads. It is not clear from your limited text.

Why do you assume just one engine? Or are the multiple "loads" (wheel assemblies?) in your text multiple cars?
What weight engine at max fuel and with a second locomotive behind it?
What speed, what likely vibration/moment through the railbed and sleepers/track?
What do you mean by "perpendicular" loads? Perpendicular to the end of the siding? Parallel to the track but perpendicular to the retaining wall?

you are not in school anymore.

Typing in all caps is considered shouting and is hard to read. Suggest you consider that when posting.

As for your question, rail loading should be treated as a distributed load. The Union Pacific Railroad and the BNSF have produced a joint document for temporary shoring that has a good discussion of how to treat the loads. The included method is applicable for permanent loads as well as temporary loads.

Document Name: Guidelines for Temporary Shoring
Published October 25, 2004

Mike Lambert

TRY THIS

Alright guys....small letters for you. No one is shouting here. Thanks for the heads up on the Temp Shoring Guide. I'll chase it down. See attached sketch for your information. Thanks.

Thanks for the small letters.

alumpkin said:

Looking for some confirmation that railway loads for Cooper E-80...
I see almost no information for loads perpendicular to the retaining wall or abutment...
Thanks for the heads up (to GeoPaveTraffic) on the Temp Shoring Guide. I'll chase it down.

Click to expand...

I've done quite a bit of work with and around heavily loaded coal railcar unloaders.

Despite the label on your sketch, the loads shown are Cooper E-60, not Cooper E-80.

I'll help you chase down the Guidelines For Temporary Shoring. Suggest downloading immediately and going to "Figure 2"... which solves your problem. (A little purple star to GPT, from me). Here it is, in part:



I agree with the added allowance for impact load you mentioned. Don't fool around with assumed loading "short cuts" - the loads are real and they are very high.

Alumpkin:
GeoPaveTraffic is right on the money with his last two paras. above, on that ref. document. I’ve heard of it, but never really used/seen it yet. I would talk with the servicing RR or RR’s at your site, they may have some of their own special requirements that they want you to consider. You might look at a detail where the last 10-20’ of rail, before the abutment wall, are on a large grade beam (or wide, thick slab), supported on the wall at the pit and supported by soil or foundation/ftg. at the free end. This would give you a much better transition btwn. the pit abutment wall and regular rail/soil structure, and relieve the concentrated lateral loading on the wall too. Your current detail will develop a relative soil settlement issue right near the wall before you even get it fully detailed. The vibrations from those engines is incredible, as a soil compactor, etc. If the engines are pulling a unit train, or some such, over that pit, you may want to pay some attention to the tractive forces also, they are pretty substantial.

I'd check on what the loads are these days for freight. In 2005 I did some checking of the effect of standing and moving loads from a railroad as they affected a corrugated culvert type pedestrian passage under a railroad in an embankment. I measured deflection of the corrugated steel liner directly under the center of the track. I used dial gauges affixed to an extendible "pipe" measuring length to the thousandth of an inch. Both vertical and horizontal distortion were measured. The reason for the study was the municipality was concerned about the distortion the "culvert" had in handling before the installation, leaving it significantly different from the oval it was supposed to be. The locomotive was directed to different positions via radio from the conductor who was in the passage with me. Both static and moving loads were "checked" for the locomotive, since we figured that would be controlling. The train was ore cars carrying iron ore. It turned out the distortion was elastic and returned to original position after loads were gone. In summary the locomotive effect on the passageway liner was much less than the ore cars. I did not get to read ore cars in static position since we thought the locomotive would be the worst. Moving loads of the locomotive had significantly less effect than the moving ore cars. I'd conclude static loads or ore cars would be much more than those of the locomotive. I'd suppose the old steam engines were used for design and setting the guides and that current locomotives spread out the loads better, maybe.

Guys,

Thanks for all of the input and I'll followup on all recommendations. FYI.....see attached spreadhseet for lateral load called "wallpres" from Alex Tomonovich. You may already have this but thought I would include if you need it. Appreciate the heads up on the soil settlement issue as I will examine this closely. One option would be backfill with stone for an area 20' x 20' x 40' to minimize settlement at this location. Using the grade beam or thick mat this location would certainly help both settlement and remove the large lateral surcharge from the engine. Currently looking at approximately a 5'-0" thick retaining wall with #10 @ 6" c/c. Soil moment is about 80 k-ft using Ka=0.5 (conservative)then add the locamotive loads. Depending on your approach....add up 5 or 6 point loads and resulting moments or using the 8 klf strip load you can end up with 170 k-ft from the locomotive. Then multiply by 1.5 for impact and then by 1.6 to get to ultimate loads and you end up with 408 k-ft from the locomotive. Then add 80 k-ft x 1.6 = 128 k-ft for the soil. Total is 536 k-ft......so 536/(4* 57) = 2.35 in2/ft....or #10 @6" c/c. You are right.....loads are massive.


Again, thanks for your input. This is a good discussion.

Just for your information......this inquiry is for a new glass factory and the rail cars will be loaded with sand. Don't know the loads yet for these material cars.....awaiting information.

Howdy Mr. Lumpkin.....long time no see.

Looking at your sketch, that's an E-60 load (you are calling it a "E-80"). The Cooper load spacing is the same regardless of magnitude. But the magnitude will vary. For example a E-10 loading:


You see the rule for obtaining any Cooper load you want.

As far as your lateral pressure goes.....I've always thought AASHTO had some good help for transforming point loads into lateral pressure: see Figure 5.5.2C (in the 16th Edition of the bridge specification, p. 120).

For AASHTO, if highway traffic can come within a horizontal distance from the top of the structure equal to one-half it's height, they cover the additional pressure with a 2' surcharge of soil against the wall. In your case however, you have loads well in excess of the 32k axial loads for highways.....so that would probably not cover you.

Can you use counterforts and a thinner wall... maybe something in the order of 18" - 24"?

Dik

By the way, another good source for this is Bowles's foundation book. In the 5th edition, on p.630, there is a fairly useful equation for lateral pressure from vertical point loads at any location relative to the point of application. (Based on Boussinesq's equation.)

One thing to remember (if you are getting some outrageous sizes and forces) is: the load spreads out against the wall like a pyramid. If you are doing it on a per linear foot basis (as many do) at the point of peak pressure......you may get a outrageous situation. But considering a whole section of wall may get things more reasonable.

Something else I'd like to note.....you mentioned you are using a impact factor. Looking at your sketch of the wall.....I'm not sure if you are talking loads from the beam that sits on it or loads from the retained soil.....but if it's the latter: you don't need a impact factor. AASHTO specifically says that (and I would think it would be applicable here unless a code I am not aware of says different).

Guys,

That's right no impact factor on the soil load only on the locomotive loads. Yes, I was spreading the load out over the face of the wall but no more than 5'-0" since the loads from the next track would overlap. Loads would be coming from both sides of the wall depending where the locomotive sits....then add backfill loads and any further loads from the train on the ground side of the wall too.

Alan L. Lumpkin, MS, PE
Greenville, SC

[blue](alumpkin)[/blue]

That's right no impact factor on the soil load only on the locomotive loads.

Click to expand...

Just so I am clear (because looking back at my last post, I don't think I am): you shouldn't apply a impact factor to any active soil pressure increase (from the train loads) either. If it's train load applied by the beam: yes. Train load from the rails on the ground? No.

Anyway.....good to see you again Alan.

alumpkin said:

alumpkin (Structural)(OP)5 Jun 18 19:32
Alright guys....small letters for you. No one is shouting here. Thanks for the heads up on the Temp Shoring Guide. I'll chase it down. See attached sketch for your information. Thanks.

Click to expand...

I truly read this in a quieter voice compared to your earlier posts. It's ridiculous that I would do that but I guess the innernets have trained me