AASHTO pedestrian rail loading 2

[jdarr002]

Sorry if this is a dumb question, but I'm reviewing some calcs for a pedestrian rail on the top of a retaining wall, and I wanted to see how others interpret AASHTO's Live Loads (see the attached scan).

Specifically, I'm looking at the connection of the rail to the CIP coping at the top of the MSE wall. So to get the design moment, I was going to use the post design. The text (highlighted) seems to imply that you only need to provide a single concentrated load at the top of the post, but the figures they provide below show loads at each longitudinal member. The designer whose work I'm checking used the 0.2+0.05*L load at the top, but also put .2 on the lower members. This seems wrong to me - if anything, I would have thought they'd use the 0.05*L since the figure calls that load "w".

I appreciate any comments! Thanks in advance!
-Jdarr02

 

[txeng91]

The language on this topic seems vague, but it seems like the longitudinal elements should be designed for 50 plf in any direction + 200 lb point load at any point in any direction, and the post should be designed for that load at the elevation of top longitudinal element or at 5', whichever is less. To do otherwise would suggest that the loading on the post is a function of the number of longitudinal elements, which doesn't seem to make sense.

 

[bridgebuster]

dnlv's assessment is correct. Post loads are independent of rail loads. Sometimes AASHTO is vague for two reasons: 1) they don't have an answer; 2) you're supposed to know this is how we've always done it.

 

[jdarr002]

Thanks for confirming my suspicions guys! I agree, too.