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Short Radius Controlled Releasing Post on Concrete Box Culvert

Question
State NE
Description Text

MwRSF Report No. TRP-03-288-14



What are your thoughts on the short radius being placed over
a box culvert;



When one post(at the 6’3” spacing) would land on the box
culvert:



Could the UBSP steel post be used?



Could the wood post be attached to the top of the culvert?



Could the steel breakaway post be used?


Here it is.

https://maps.google.com/maps?q=Scribner,+NE&hl=en&ll=41.669472,-96.672665&spn=0.001685,0.002411&sll=39.609127,-106.370444&sspn=0.027806,0.038581&oq=scribner&t=h&hnear=Scribner,+Dodge+County,+Nebraska&z=19


Keywords
  • Bullnose Median Barrier & Short Radius
Other Keywords none
Date February 13, 2015
Attachment NYSR.png


Response
Response

I have briefly looked over the materials and will make a few comments below.

What are your thoughts on the short radius being placed over a box culvert;

** I have reservations about the placement of a SRG over culvert hazard. Per the draft sketch, an impacting vehicle would likely deform the system and travel far more than the 6 to 7 ft distance to the obstacle being shielded. The accepted Yuma County system and grandfathered/modified TTI system have secondary lengths longer than that shown as I recall. For Yuma County, the pickup truck appears to have traveled up to 20+ ft into system at TL-2 conditions. For SRG designs, CRT posts are around and/or behind the nose section. These posts are founded in soil. A concrete box culvert would likely obstruct post placement as you noted, thus potentially altering its safety performance from what was observed many years ago. In summary, hazard seems close and barrier cannot be installed in similar manner to that tested previously.

 

When one post (at the 6’3” spacing) would land on the box culvert:

Could the UBSP steel post be used?

**We have verified the use of UBSPs in bullnose applications in lieu of CRTs. We are getting ready to verify their use in long-span guardrail systems. We do not know how they will perform in SRG systems. As we continue to investigate their use in barrier systems, we may eventually try UBSPs in such designs. However, some post rotation and energy dissipation occurs when placed in soil. When mounted to culvert slab, the behavior may not match that of CRTs in soil. In summary, we cannot justify its use in an alternative manner without adequate R&D. I guess one needs to know how much soil is over culvert slab.

 

Could the wood post be attached to the top of the culvert?

**I do not currently see how this attachment would be accomplished and provide similar behavior to CRTs in soil.

 

Could the steel breakaway post be used?

**I discussed the UBSP above.

Date February 13, 2015


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