UIC Load 71 or S1950 Rail Load Distribution 1

[chaos13]

Hi Everyone,
I have a problem about load distribution of railway load. For underpass and culverts of railway , UIC Load 71 or S1950 loads are distribute on 1m width for modelling. But during converting loads to Kn/m to Kn/m2 angle of 45 degress is used. In the attachment figure it is shown how the load is converted.
My problem is 45 degrees is a very high value and makes it very hard for 8-10 meter span of underpasses.
My question is can this angle be lesser?? Or According which specification this value is true or wrong??
(Note: This angle is not related with soil or slope of fill- This angle is used for load distribuiton on culverts and underpasses)
Link:

http://www.4shared.com/file/114026817/2dbc6938/Distribution_angle.html

 

[ishvaaag]

Do you mean that the railway with the ballast zone becomes necessarily too wide by using a 45 deg surface? The question in such case, I think is more constructive than of distribution of loads. Some amount of ballast helps to damp the mechanical vibrations induced by trains, and using steeper than 45 deg slopes for the ballast would cause it to fail under the vibrations. So a section of ballast able to oppose such effects is used. Then, within the ballast section you might consider a narrower band taking the load of the rail, but always then checking that you remain within a stable ballast shape, and this is not easy to prove above 45 deg.

 

[chaos13]

Thank you ishvaaag ,
But consultants here does not agree that ballast helps to damps the mechanical vibrations.. As a result uic load model 71 or s1950 train load is is multiplied by dynamic coefficient and divided by base fill width to find distributed load..
For ex.. P2 = 104 Kn/m (part of train load)
104 x 1,3 /3,9 = 34,67 kn/m2

But when the alfa angle decresead to 30 degrees
104 x 1,3 / 4,78 = 28,29 Kn/m2

If you have any tech. specs and standarts about loads and design of railway culverts and underpasses can you post links?? (To prove 45 angle is correct for instance)
Thank you again..

 

[ishvaaag]

In the old
Instrucción Relativa a las Acciones a considerar en el proyecto de Puentes de Ferrocarril, that stood around 50 years in force, distribution was mandated 1:1 on the wood blocks, and 1:1 or 1H:2V through the ballast, the worse of them ... son not wider area to distribute load by that code.

Have also downloaded the modern IAPF 2007

http://www.concretonline.com/pdf/07construcciones/legislacion/IAPF2007.pdf

article 2.3.1.4.2 states that distribution through ballast will be 1H:4V.

Hence the evolution is to less and less area on which to distribute the load, as to disregard any damping of ballast (surely with good reason if only of not being worth the ffecto of the weight).

So no help from Spain's railway codes.