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Approach Transition Post Alternatives

Question
State NE
Description Text

Please review and comment.

 

Latest changes:

Is a w8x21 " 7' a quality substitute for the w6x25 " 7' for posts 1-3?

 

These match the 2000 Texas Transportation Institute TTI testing to NCHRP 350 - Contract No. DTFH61-97-C-00039 as well as letter from Ron faller " Sept 26 2002.

 

Posts at the end of the nested thrie-beam and through the 6'-3" single thrie-beam and 6'-3" transition to w-beam follow testing performed by MwRSF Research Report No. TRP-03-210-10 "Design K".

Testing also known as:

Midwest States' Regional Pooled Fund Research Program

Fiscal Years 2008-2009 (Years 18-19)

Research Project Number SPR-3 (017)

NDOR Sponsoring Agency Code RPFP-08-05

 

The need for using two tests to justify the bridge approach section comes from the later test using a thrie beam bridge rail instead of transitioning to a concrete rail.

Keywords
  • Approach Guardrail Transitions
Other Keywords none
Date May 7, 2010


Response
Response A W8x21 post has a flange width of 5.25 in. while the tested W6x25 had a flange width of 6 in. This could cause significantly differences to force-deflection characteristics of these posts. This coupled with the 10% strength difference between the posts raises too many unknowns for me to say that the posts can be used interchangeably.


With your alternate assembly design when you are specifying W6x25 posts, hopefully you are putting these larger posts after the W6x15 posts. The W6x25s cannot simply replace the W6x15s (at least without component testing and analysis to show there isn't any snap problems)


Finally, one minor error I see in the drawings " the post 3'-1.5" post spacing is labeled as between post nos. 7 and 10. It should be 7 " 11. It's drawn correctly, just labeled incorrectly.
Date May 24, 2010


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