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Transition from single slope to F-shape barrier

State IA
Description Text

I am working on a new standard.  The need for this standard came from the transition from F-shape to single slope as our standard shape.  This new standard is a transition from 44” single slope to an existing 44” F-shape.  I was hoping you could review this standard and provide your thoughts.


A couple of discussion points that have come up:

  • Field bending of the horizontal

  • Connection between existing barrier and new barrier.  Dowls vs. chipping away concrete and lapping with existing rebar.


Please review and provide comments.



Permanent Concrete Barriers

Transition and Attachment Structures

Date June 28, 2022
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Attachment BA-111.pdf

Overall,  this detail looks pretty good.  We have been recommending a minimum lateral taper of 10:1 for concrete barrier shape changes.  Your 4-ft long transition section satisfies this criteria as the two barrier sections are similar in width.


  • From what I have heard during discussions with various DOTs, field bending of longitudinal rebar is pretty common for shape transitions.  Even if the longitudinal bars are pre-bent to approximately the correct shape, there always seems to be small tweaks necessary to fit right within the rebar cage. I do not think this is a problem.
  • Chipping away concrete to lap with the rebar in the existing barrier would likely result in a stronger barrier connection.  However, using a doweled joint similar to the one you are showing is common and has been successfully crash tested in multiple barrier segments. In fact, MwRSF has recently crash tested a similar joint detail on multiple of Hawaii DOT’s concrete bridge rails to Mash TL-3.  Thus, I don’t see an issue with using a doweled joint. I do recommend increasing the length of the dowel bars.  The tested Hawaii barriers used 2-ft long bars with a corresponding 12-in. embedment in each barrier.  This increases concrete breakout shear strength and typically results in the dowel extending through 2 transverse stirrups (additional strength and robustness).



Let me know if you have any further questions.

Date June 30, 2022
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