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top mounted Guardrail to culvert attachments

Question
State KS
Description Text I’ve attached KDOT’s current Standard Drawing (RD617E) for attaching MGS to low fill culverts as well as a sketch (Attachment to Low Fill Culverts) from a project currently being constructed. The design engineer on the project has run into an issue where the steel plate that rests on the ceiling of the box is conflicting with the fillet in the waterway opening (this is occurring at several locations). The sketch in the second attachment depicts the issue. We’ve investigated shifting the guardrail installation to avoid the conflict with the fillets, but unfortunately we are unable to avoid them given the needed post spacing. I’d like to discuss whether or not we could include washers between the steel plate and the culvert ceiling to shim the plate down an inch or so to avoid the conflict. I marked on the second attachment where the washers would be included. 
Keywords
  • Guardrail
Other Keywords culvert top slab
Date July 22, 2015
Attachment Attachment to Low Fill Culverts.pdf
Attachment rd617e.pdf


Response
Response

.  I do not see a problem with utilizing washers underneath the culvert top slab.  In fact, a similar attachment scheme was full-scale crash tested back with the original evaluation of this system – see report no. TRP-03-114-02 page 111 (available on MwRSF website/research hub).  The tested configuration utilized only rectangular plate washers in the attachment of the through bolts to the underside of the culver slab. You could use this concept too, if desired.  If you utilize washers of a similar size, you would not need to include the full-size washer plate in addition to the enlarged washers.  The individual washers alone would suffice. 

Date July 22, 2015


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