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We have this standard that shows a basic bridge pier protection.

We are updating it to make it longer but have questions about tying it to the road.

https://iowadot.gov/design/SRP/IndividualStandards/ba150.pdf

Is there information on how much rebar should be in the connection between barrier and the pavement for a 54" tall barrier? I would imagine details would be different between asphalt and concrete.

We actually looked at this barrier as part of the Midwest Pooled Fund project on MASH equivalency for existing barrier systems. At that time we found the barrier to be MASH TL-5 compatible based on internal transverse steel stirrups and corresponding anchorage of #5 rebar on the front and back faces of the barrier at 12” spacings.  Please see the attached for a brief analysis of the barrier – it is also documented in the final report for the study:  https://mwrsf.unl.edu/researchhub/files/Report495/TRP-03-454-24.pdf

Utilizing less anchorage steel for this barrier would reduce the barrier’s strength capacity. At this time, we don’t have a method to evaluate the anchorage strength requirements for concrete median barriers.  We are working toward this goal with a new Midwest Pooled Fund project, but the project is only in the infancy of Phase I of the study. Thus, we would have to fall back to comparing anchorage strengths on similar MASH tested barriers.  The closest comparison point is the Manitoba barrier referenced in the previously noted study.  That barrier used #5 anchors (front and back face) at 15.75” spacing.  However, this spacing doesn’t match with your reinforcement of IA’s TL-5 barrier, so I don’t know if increasing the spacing slightly would have any benefit as there wouldn’t be anything for the anchor bars to tie to. A 12” spacing may be the best answer for now.

Note the previously discussed study/analysis was focused on the rebar anchorage being tied to a concrete roadway slab.  As you mentioned, asphalt would not provide the same strength.  I am unaware of any studies or tests on concrete barriers being tied to asphalt pads.  Until further analysis/testing is conducted, I would not recommend anchoring the TL-5 barrier to an asphalt pad.