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F-Shaped Median Barrier

Question
State IN
Description Text

Good afternoon,



ODOT completed some MASH testing on a single slope
unreinforced concrete barrier.  I was hoping to review the crash report
and also had a question.



  • Is the ODOT report available on line?  I did not see it in the MASH list, sorry if I missed it.

  • INDOT uses a similar unreinforced
    F-shaped barrier
    – can the single slope results be used to support
    continued use of the F-shaped barrier as MASH TL-3 compliant?  Is there a
    compilation of research that can be used to support continued use as MASH
    TL-3? 

  • We have attached a PDF that shows the INDOT F-Shaped Median Barrier

thank you





Keywords
  • Permanent Concrete Barriers
Other Keywords F-Shaped Median Barrier
Date June 27, 2018


Response
Response

Unreinforced barriers crack over time, even to the point where visual gaps may exist throughout the cross section. In this scenario, no rail continuity would exist, and vehicle redirection is dependent on a combination of several factors, including the inertial resistance of the thick concrete barrier, any bond between the barrier and support surface and/or asphalt keyway, and the limited structural capacity of the concrete cross section (shear, tension, torsion, bending, etc.) away from the gap location. Your barrier appears to have a similar or greater footing resistance to the Ohio barrier we tested. However, because your barrier section has no reinforcement, the only comparison we can make between the tested Ohio barrier and your shape is the inertial resistance.

 

I have reviewed your F-shape section and compared it with the Ohio single-slope section. Your barrier is 9” shorter with nearly the same base width. Thus, the Ohio single-slope has approximately 19 percent more mass per unit length as your F-shape. Because the F-shape barrier has lower mass and inertia, we cannot say definitively that the section will meet MASH TL-3. Based on the lack of damage observed in the testing of the Ohio barrier, there is potential for your F-shape to meet MASH TL-3, but there is no way for use to prove it. Thus, we have to take a conservative approach and say that for a section to be equivalent to the Ohio barrier that was tested, it would need to have equivalent or greater section properties (similar width through the height of the barrier) and mass per unit length.

 

Thus, we cannot make a concrete argument for your barrier being MASH TL-3 compliant at this time. This discussion is very similar to the discussion I had with Ohio that led to the full-scale crash testing of their barrier. We have also had similar discussions with Kansas DOT regarding a smaller F-shape barrier with minimal reinforcement and not shear steel.

 

Date June 28, 2018
Attachment IL-OH_COMP.jpg


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