Rail to concrete slab loading 1

[onnophris]

Hi,

New to the board but looking at some other posts i can see that i came to the right place.

Assuming the load on a rail is 2000kN (YES 2000kN) from a wheel, how is the load then transferred on to the concrete slab? The rail has no sleepers but is placed straight onto the concrete slab. I've done smaller works but this is the first time that i've ever had to consider rails.

:S

 

[cap4000]

Explain the 450 kip wheel load!! WOW!!. The wheels, how many feet on center and how far apart is the other rail?

 

[onnophris]

I'm not sure how the loading to the wheel was arrived at since i don't know what the crago been carried is. However what i'd like to know is whether the load then gets spread across the rail or if the load is transferred straight down via the contact area. Hope that makes sense. Thx for any input.

 

[dicksewerrat]

That has to be a big wheel. The load will go directly to the slab spread only by the width of the rail. But you can design the slab to take any load. Look real hard at the soil under the slab. That is where the real problems will take place.

 

[onnophris]

Yeah i thought as much. Just wanted to get some more input.
The soil isn't that great either... Reclaimed swamp land. Mixture of gravel and sandy soil was used to reclaim.

 

[cap4000]

I would only use the wheel imprint area on the rail. Your situation sounds like a "train wreck waiting to happen". To put your slab thickness in a similar perspective: Airport runways based on a 100 kip wheel loads under optimum soil conditions go around 24 inches thick +/- . What does your slab construction joints look like?? Good Luck!!

 

[Focht3]

Where is the site?



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[letrab]

Would you find rails capable of transmitting this load? It sems likely that you have to design purpose made rails for your 200T load before you start on the track slab.
Are you sure about the wheel loading? 2 military tanks per wheel is quite a load and it may be cheaper to look at different bogeys to spread the load to more wheels.

 

[onnophris]

Yes those load numbers were as stated. However, modifications have been made now, and the number of wheels and rails increased to help redistribute the cargo load.
Subsequently the load was reduced to 800kN imposed onto the concrete.

 

[dicksewerrat]

Now its down to one 18 wheeler per contact. 4000 psi concrete will need to have the wheel/rail contact equal to 20 sq. inches. And garbage for soils? preload the soils with 2o feet of granular and wauit a year to see what the settlement is. Then hire a Geotech. engr, a P.E well versed in reinforced concrete and foundations. Good luck

 

[Ron]

The load transferred to the slab depends on the stiffness of the rail. Ultimately all the load goes to the slab, but the stiffness of the rail will dictate the area over which the load is applied.

Assume the rail acts as a beam. Decide on some spacing for the "beam" supports (start with a guess.. you can refine by iteration)....this will be the contact points on the concrete. Compute the reactions for a continuous beam with 3 supports. This will give you a starting point for your load distribution on the concrete.

Another approach is to assume the load is spread at a 45 degree angle in both directions from the center of load to the bottom of the rail. This will give you the contact stress on the concrete. From there, it is a pavement design problem for the concrete.

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[onnophris]

Thanks Ron, that was the information i was after.

 

[unclesyd]

Just for curiosity is this for a shipyard or cargo gantry?

I am acquainted with recent job for a shipyard where there were two trucks on each leg of the tower for a total of four trucks and if my memory serves me right there were 6-8 wheels in each truck. The only thing that I remember about the rail system was a very tight call-out on the straightness and flatness of the rails. I saw no call-out for the rail weight.
After my part was over I thought about the problems they are facing on this job. This area of the yard is all delta, muck, and fill and first consolidated area is around 200 ft deep.

 

[ACtrafficengr]

Cement stabilization of the base course might help.