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Review of Standard drawings: 7470 - Guardrail Attached to Culvert

Question
State NE
Description Text We have developed a new standard for guardrail attached to culvert based on recent MwRSF research. Can you please review the details and provide comments.
Keywords
  • Guardrail
Other Keywords Culvert
Date December 19, 2014
Attachment 74700e00.pdf


Response
Response

I have reviewed the attached drawings and have the following comments/edits,

 

Sheet 1:

·         The spacing between the first S3x5.7 post (in socket on culvert) and the adjacent W6x9 post (standard line post in soil) can be either 37.7” or 75”.  The wider spacing may allow installations to avoid conflicts with W6x9 posts and concrete structures such as wing walls.

·         The cross section view shows a standard line post and blockout configuration, but is labeled as an S3x5.7 post.  The line posts (in soil) should remain the standard W6x9 posts.  The S3x5.7 posts are placed in sockets which are attached to the culvert, and do not utilize blockouts.

·         The notes section call out guardrail bolts for standard line posts.  The rail attachment bolts for the bridge rail (and this culvert attachment) are 5/16” dia. A307 bolts.  Further a 1.75” square washer (1/8” thick) is utilized between the bolt head and the face of the rail.

·         The weak-post bridge rail should have backup plates between the posts and the rail.  The original bridge rail was tested with 6” backup plates (6” long sections of W-beam).  However, as discussed during the Dec. 17th pooled fund meeting, MwRSF will be recommending utilizing 12” long backup plates for all weak-post guardrail variations due to the consistent occurrence of rail tears forming during crash testing at both TTI and MwRSF.  Oversized holes/slots will need to be cut into these 12” backup plates to fit over the splice bolts for the post locations that coincide with rail splices.

·         Note section should also indicate that any of the 4 designs on sheets 3-6 are acceptable for use.  All utilize the same post, just the attachment to the culvert is different.

·         A note should be added to specify an epoxy with a minimum bond strength of 1,300 psi.

 

Sheet 2:

·         The post length should be 44”, not variable

·         The post details on the right again show a standard line post to guardrail attachment (12” blockout and 5/8” bolt).  This detail needs to be replaced with the 5/16” bolt, square washer, and 12” backup plate as discussed above.

 

Sheet 4:

·         May want to add total length dimension of 9” (top to bottom) for top mounting plate.

 

Sheet 5:

·         The 5-13/16”  dimension should be from the bottom of the top plate to the center of the hole.  The dimension as drawn (bottom of top plate to absolute bottom of plate) should be 7-5/16”

 

Sheet 6:

·         The welds on the top plate gussets (shown on “top view”) should be ¼” fillets.  3/8” welds are too large for ¼” thick plate.

 

 

Date December 22, 2014


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