How to reduce loads from train

[rte4563]

I have been given loads from train that needs to be reduced so that what is beneath the train (short reinforced concrete columns under railway track) experiences lower loading. The reason they can be reduced is because the loads are given for a train when its operating under normal conditions with appropriate speed to get a number of passengers from A to B etc. However, I need to reduce the loads to when the train comes into a station where it gets repaired/serviced. Meaning there will be almost no passengers, and it will have to come into repair station with what I assume must be a very low speed. How can I best argue that the both the vertical and horizontal loads will be lower than under normal conditions? Not sure which angles to attack this problem from. I assume the train operates outdoors with all the 4 seasons and inside tunnels.

Vertical loads for a train in normal conditions (can ignore dynamic effects):

Horizontal loads for a train in normal conditions (can ignore dynamic effects):

 

[rb1957]

is this an interview question ?

you (if a graduate engineer) really should be able to answer "How can I best argue that the both the vertical and horizontal loads will be lower than under normal conditions?", well the "both vertical and horizontal loads" part.

you are already talking about the two (as I in my uninformed state) primary factors on loads ... speed and weight.
how does the weight of the empty carriage compare to the weight of a full one ? how do you think load is affected by weight ? (eg directly proportional ?, inversely proportional ??)
how does speed affect load ? makes sense that it does.
but why mention "inside tunnels" ? if you know where this is, and it is a specific question/problem. That's why I think this is an interview question.
and if a specific problem you'd know I need to reduce load by a factor of X.

a different side to the question ... how do you ensure that your revised loading isn't exceeded in service ? In my business we'd placard the train, and the operation manual, etc.
another angle ... how do you ensure that some other engineer doesn't miss use your "relieved loads" and use them as "full loads" ? or at least make it difficult for them to do this.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[JStructsteel]

Keep in mind that usually the heaviest load in a train load is the locomotive. Usually not a lot of people on a locomotive. Reducing the dynamic impact I can buy into, but not the DL of the train.

 

[centondollar]

I was under the impression that railway loading is standardized in most countries (at least across Europe) and that size of rails and minimum spacing of concrete sleepers (what you call "short columns", which technically are more like short beams) is similarly standardized. You post a loading diagram (seems to be from a European national standard); if you claim that it is for a passenger train, you can quite easily estimate the reduction in weight by multiplying the number of seats in one train cart with the weight of an average passenger (say, 100kg in a western country to be on the safe side) and subtracting that from the load given in your diagram.

There really is not much of a weight saving to be had for a passenger train as you'll find out by doing the above calculation.

 

[3DDave]

It may be a self-propelled passenger car.

I don't see anything on a train that would present a uniform load to a piece of track and no way that all loads go unreacted in a loads diagram.

The tilt diagram is for a higher speed line, so that would not be near a repair facility.

A photograph of the exact same structure that is being evaluated (not a picture of something that is supposedly just like it) would be helpful.

There's also the following problem - what appears to be the task is to justify the lowering of the factor of safety by claiming the load is less by some amount. That's a great way to have a dramatic failure when some assumption turns out to be wrong.

 

[JStructsteel]

3DDave, if you look at AREMA loading (Cooper E80), the load is 2 locomotives pulling a infinite 8000lb/ft train. I believe its derived from each locomotive having a coal car too.

The first 2 locomotives make up about 100' of the train, then the uniform loading as designer sees fit for the spans that you are designing.

Alternately, there is a 4 axle 100K/axle load that can be used.

 

[JStephen]

I would think whoever builds the railroad facilities has very extensive standards on how everything is to be built, and your problem is getting them to change one standard for your situation. Which makes it more of an internal-political issue and not so much engineering.

 

[Just Some Nerd]

I was under the impression that railway loading is standardized in most countries (at least across Europe)

Certainly have a standard loading here in Australia, this question reads like someone trying to avoid an inconvenient answer

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Why yes, I do in fact have no idea what I'm talking about

 

[3DDave]

If that's a locomotive it's about 18 feet long.

 

[HTURKAK]

Er.rte4563 (Mechanical),

The first picture that you have posted is from EC-2 ( EN 1991-2 )

Figure 6.1 - Load Model 71 and characteristic values for vertical loads

Pls look Clause 6.3.4 ; Load Model “unloaded train”

Copy and pasted below ;

6.3.4 Load Model “unloaded train”
(1) For some specific verifications (see EN 1990 A2, § 2.2.4(2)) a particular load model is
used, called "unloaded train". The Load Model “unloaded train” consists of a vertical
uniformly distributed load with a characteristic value of 10,0 kN/m.


the UDL q=80 kN/m is for freight wagon..



Pls check the standard for other limitations for the Load Model “unloaded train” and you may provide more details to get better responds..










Tim was so learned that he could name a
horse in nine languages: so ignorant that he bought a cow to ride on.
(BENJAMIN FRANKLIN )

 

[JStructsteel]

3DDave, not sure where the standard they are showing is from. But the Cooper E80 alternate loading is only 16' long. It could just be a service vehicle, yard loco, etc. Look at the HL93 for AASHTO, if you dont know what you are looking at, you would see a tandem load thats only 4 feet long. But it represents a different thing.

 

[MotorCity]

If your design is teetering on whether or not the train is loaded with people, it is most likely near 100% capacity and should be re-designed or reinforced.