arema longitudinal force bridge design

[reklawmot]

I am designing a two-span, cip/ps box girder bridge to carry two RR tracks. Regarding the longitudinal force:

a) do i double the braking or traction force because there are two tracks or is there a reduction allowed?
b) do i have to consider a combination of braking and traction forces for two trains traveling in opposite directions on the two tracks?

Thank you!

 

[civilperson]

a) Yes
b) Yes, a twisting action will be produced. (Usually not controlling)