Design of 42" concrete parapet barrier rail

[actengr]

I have designed a 15' reinforced concrete cantilever retaining wall adjacent to a roadway. The client desires to extend the wall an additional 42" to create a rigid concrete barrier rail. The aluminum railing will then be attached at the termination of the concrete rail. How should the additional 42" be analyzed and designed considering LRFD and TL-2 requirements? It doesn't seem correct to consider yield line analysis in this situation. Or would beam theory be applicable if a 42" cantilevered beam is considered?

 

[msquared48]

So the retaining wall is probably 8" thick at the top with a mimimum of #7 @6 at the bottom and droppping to #7 @6 @ midheight, carrying to the top.

I find it hard to believe that #7@12 carried an additional 42" or so will not win against a car. I also think that the car will be crushed snd stopped before the tow of the wall sees any additional load, if any.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[bridgebuster]

I agree with Mike. Typically we don't add the impact force to the wall because the backfill will resist sliding and overturning. Just design the parapet and connection per AASHTO

 

[actengr]

Thanks for the replies. The problem is that AASHTO requires yield line analysis for the design of barrier railings. Don't think this is applicable since the wall is conitnuous. So, should beam theory be considered for the 42" extension resulting in larger As for that extension due to impact LL?

 

[bridgebuster]

Here's an out: Your state DOT should have a standard parapet design for all of the TL loadings and a standard for connecting it to a retaining wall. NYSDOT does. Nothing to design.