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We ran into a potential issue with an existing bridge terminal wall and some staked temporary concrete barrier that need to be butted together to protect the motorists (see diagram below).  Looking through the past research, I found a drawing from 2008 for the R6-TCBT-1 that connects the temporary barrier to a single slope but our situation is a F-shaped barrier.

We are concerned about pocketing between the two barrier and wanted to see if you had any recommendations.

Thanks

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Chuck,

Thank you.  The bridge barrier that the temporary barrier is butting up against is the older standard VDOT BPB-4C terminal wall, I’ve attached the detail from the plans.

The posted speed will be 55 mph.

Thanks,

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Chris:

Do you have a sketch of the abutting bridge parapet?  I would like to send a request for input from our pooled fund folks at the University of Nebraska to see if they have any recommendations.

I agree that the two systems do not have the same deflection characteristics and could cause snagging.  What will be the posted speed?

Thanks

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I’m reaching out to you regarding a potential issue that has come up on the HRBT expansion project, related to the transition between the temporary concrete barrier on the roadway and the bridge parapet for the SMOT EB Trestle on the south island.  This is the run-on side of the bridge, where EB traffic is coming out of the tunnel and transitioning to the bridge.

The design-builder is intending to utilize pinned MB-11A along both sides of the approach roadway, and butt the MB-11A up to the bridge parapet terminal wall.  No physical connection is planned between the MB-11A and the terminal wall.  We expressed some concern about this situation, given that the end of the MB-11A pinned in asphalt may still move when impacted while the bridge terminal wall would not, leading to a potential blunt end/snag hazard at the interface.  We suggested the potential use of VDOT Standard Detail MB-INS (502.24) for this situation, which includes a 20’ length of two double face barriers with sandbags between them.  However, the design-builder has stated that they do not have enough space available to accommodate the width of this detail.

We wanted to see if you had any thoughts on this situation – below is a sketch from the MOT plans showing this location on the south island.  Please let us know if you need more information or want to discuss.

The report for the barrier system you mentioned has the best available guidance for that type of installation.

https://mwrsf.unl.edu/researchhub/files/Report54/TRP-03-208-10.pdf

This research looked at transitioning to a critical median barrier shape from free-standing PCB, but it also included guidance for attachment to other shapes. For attachment to an F-shape, you would want to align the traffic side face of the PCB with the existing bridge terminal. Note that if there is a height difference between the PCB and the parapet, you would want to have some type of cap to transition the height smoothly. I cannot see the height of the PCB in your detail, but it may be similar.

Also note that the transition guidance in the report above was developed for the F-shape PCB used by many of the pooled fund states. Your barrier appears to have different anchoring and barrier details. As such, it may not perform in an equivalent manner when impacted. However, this may the best guidance we can currently provide. One could use a similar staking pattern modified to coincide with your barrier configuration. However, this has not been tested. Thus, there may be differences in the stiffness of the transition and the structural capacity of the PCB segments.

Let me know if you need more information.

Thanks.