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Short Radii Other than Tested - Bolts on Posts in Radius

Question
State WI
Description Text Previously, MwRSF performed research related to the use of short radius guardrail with larger radii. Previously tested short-radius systems did not use guardrail to post connection bolts. Can you comment on this?
Keywords
  • Bullnose Median Barrier & Short Radius
Other Keywords none
Date February 6, 2015


Response
Response

I had a chance to discuss the bolts on posts topic with Bob and Dr. Faller and we seem to be in agreement here. All the tested systems did not utilize a post with a bolt in the radiused section for concern that the post would remain attached to the rail for too long and drag the rail down. There doesn’t appear to be a pressing need to add a bolt to those posts on the radius if the radius increases. Thus, we concur with omitting post-to-rail bolts for posts within the curved rail section. Please note that there should be adequate upstream length of rail on the secondary side of the system (and primary side too, if not anchored to a stiff structure or rail) to develop the required tension in the rail. According to what I found from the Wisconsin larger-radius guardrail simulations, the first point on a guardrail system that can capture or redirect a truck impacting with TL-2 conditions was 6 posts downstream from an anchor, or the 8th post from the upstream end of the rail. I recommend that this point be approximately aligned with the beginning of the length of need.

 

Dr. Faller indicated he is more inclined toward the use of a small shelf bracket on the CRTs in lieu of a screw on the front of the post. I believe the bracket is more helpful to support the post because (1) it is easier to mount the rail and (2) to reduce the propensity for stress concentration and possible rail tear initiation at the screw. Nonetheless, mounting hardware is up to your determination.

 

Let me know if you have any additional questions.

 

 

Date February 6, 2015


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