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The Internet Police kicked me off Linkedin and you guys apparently had some server issues yesterday.

What would be Midwest’s thoughts of using the new Thrie Beam Bullnose in the gore of an exit ramp?

Everyone here thinks it’s a great idea, but I remind them that at what point are we going to begin a flare to match the existing mainline and ramp guardrail.

I would propose to flare at Post 8 as shown on the Wisconsin drawings. Is this Wisconsin detail a result of the Midwest research?
The flare at Post 8 I propose is based on the beginning of “Unbent Standard Thrie Beam”.

I am trying to address an existing ramp where the mainline and ramp guardrail was terminated with a pair of Tangent End Terminals essentially beside each other. None of us believe this is an acceptable design, since to our knowledge there is no testing of TET’s in this placement.

The TET’s do not look like this today, I have some pics if you would like to see them. 

The detail you sent from WisDOT is based on our bullnose system that was tested to NCHRP 350 criteria. We do believe that it can be used in gore areas and it has been done in the past. You can get the reports and other details for the system at the links below.

http://mwrsf.unl.edu/researchhub.php?search-textbox=bullnose&submit=Search

With regards to the start of the taper or flare, we have allowed flaring of the system to begin at post no. 5 with a flare rate of 15:1 based on RDG guidance. That flare may change based on your conditions and the RDG guidance for them.

With regards to the grading, we have addressed this issue in the past by stating that the bullnose itself should be on a maximum grade of 10:1. This applies to cross slopes and v-ditches. We also recommend that the 10:1 slope area be applied for at least 60’ in front of the system to provide for more stable tracking of errant vehicles prior to impact. For the longitudinal slopes prior to the 10:1, we have come up with several options in conjunction with the Minnesota DOT. Can get you those if you need them.

Only one other thing to note. Because the gore installation has similar traffic flow on both sides, you will have to make sure that the thrie beam splices are lapped correctly with the traffic flow on each side of the system. For two way traffic, lapping all of the guardrail the same as it moves around the system is fine. However, with the gore installation, this would cause the splices to be setup wrong along one side. I would suggest simply switching the splice on either side of the nose as needed.

Thanks