Retaining LRFD Design Considerations

[Jean_Wong]

Good Day!

I am designing retaining walls to be used on a railway project. AASHTO LRFD is required for the design.
Which parts of the code should I read & apply to my design?

For the retaining wall, I have already considered active soil pressure, seismic soil pressure using mononobe-okabe method, (passive to be neglected), surcharge(vertical & horizontal), cohesion, wind (have to confirm if needed).

For the 1st type, the train runs on the heel side of the wall and the soil to be retained is on the other side. How do I apply the load from the train? Do I just apply as uniform surcharge or concentrated load? Dead or live?

For the 2nd type, the soil and the train tracks are both on the heel side.

 

[TehMightyEngineer]

If it was per AREMA I believe they had soil surcharge pressures for train loadings given in the code. For AASHTO you probably have to calculate the actual pressure based on a strip load per 3.11.6.2 in AASHTO. Don't forget the AASHTO eccentricity check for retaining walls and AASHTO also requires you to calculate both strength level and service level soil bearing pressures.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[bridgebuster]

The attached graph may be of help. It shows surcharge loading due to Coopers E80 loading; keep in mind this is for one track only. If you have multiple tracks you have to account for the additional surcharge. Also, some railroads have specific requirements for the surcharge.

One question: In your Type 1, did you mean to write that the train runs over the toe instead of heel because the retained fill on a wall is over the heel?

 

[Jean_Wong]

Thank you very much!

Yes. It has no heel but has a toe. Imagine a rectangular tunnel without the top part. There's 2 retaining walls whose toes are connected, & the trains run through them. On the other side is 2+ metres of soil. I figured that the only use of the train loading and everything inside the wall would be for bearing capacity check and footing design. The active, seismic, dead & live surcharge would be used for stem design.