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Guardrail flare rate with Bullnose

Question
State NE
Description Text

With w-beam tested on a 7:1 taper rate, would you expect
thrie-beam to redirect a MASH vehicle properly on a 7:1 taper?



 



What about thrie-beam on a 8:1 placed in a 45 mph median?



This is attached to a bullnose.

Keywords
  • Bullnose Median Barrier & Short Radius
  • Guardrail
Other Keywords Flare
Date July 1, 2015


Response
Response

We have not recommended increased flare rates on thrie beam at this time. While the work done with the MGS system would indicate that the potential for increased flares with thrie beam exists, there are too many unknowns. The thrie beam system would have different capture, post stiffness, and dynamic deflections as compared to the MGS. As such, it is difficult to ensure that the performance would be similar. Certain design changes might need to be made regarding the post embedment, splice location, and the blockout geometry to ensure that it would work.

 

As far as the bullnose system goes, we have recommended standard flare rates as recommended by the RDG beginning at post no. 9 on the oncoming traffic side. Flaring prior to post no. 9 may affect the performance of the bullnose. On the reverse direction traffic side of the system, we have allowed more aggressive flares as the guardrail would be flaring away from oncoming traffic.

 

The RDG list 8:1 flares as acceptable for 40 mph and 10:1 for 45 mph.

 

Thanks

Date July 6, 2015


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