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weak-post guardrail attached to (small) headwalls

Question
State IL
Description Text We had a question about the weak-post guardrail attached to culvert headwalls that MwRSF designed. Is the 12 inch headwall width,
highlighted in the attached photo, a requirement or can we reduce that to lets say 8 or 10 inches? We have existing culverts that don’t
meet that min requirement.

So our following questions are as followed:
• Is the 12 min head wall required to remain or can we have something smaller in width of 8-10 inches?
• For case I (page 2 attached) can the plate E be modified to fit a culvert head wall that is 8-10 inches wide but not be significant to
the system?
• Or Would case III be better for a smaller culvert head wall and could the two ¾ x 11 (M19 x 279) threaded rods be smaller to 7 or 9
inches long?
Keywords
  • Guardrail
Other Keywords weak-post, MGS, culvert, headwall
Date September 12, 2019
Attachment 223-630111-01_WeakPostGuardrailAttachedtoCulvert.pdf
Attachment 12 inch headwall dimension.pdf
Response
Response There is brief discussion of smaller headwalls within the recommendations section of the test report (TRP-03-277-14 – page 107-108).  The 12” headwall depth can be reduced, but proper anchorage of the threaded rods must be maintained. The easiest method to ensure anchorage strength for narrower headwalls is to utilize through bolting, or Case II on page 3 of your drawings.  Through bolting would not have the negative effects of anchorage depth or edge spacing that are present with epoxy anchors.  As long as the headwall is reinforced and anchored to the top slab, through bolting is recommended for attachments to narrow headwalls (i.e., headwalls similar to yours with 8-10 inch thicknesses).
Date September 12, 2019