View Q&A

I apologize for bugging you again so soon, but as the manufacturer is working on obtaining an engineering analysis for the anchored J-J hook connection jersey wall that you previously looked at for me, they and contractors are asking some particular questions about the J-J hook connection 12’/12.5’ F-shape wall and some different nuances with those.  Those walls were tested/passed with that connection but we have some questions about the specifics of these shapes.

The manufacturer/contractor has approval from Georgia to use an anchored F-shape with 9” top, however the crash tested F-shape only had an 8” top when anchored.  Per attached email we had recently denied the use of the 9” in the anchored condition due to some subtle differences from that of the 8”;  part of that was rebar size/placement but I’m having a difficult time determining where those are and especially how impactful that may be.  You’re probably aware that the F-shape 9” top with J-J hook connection was tested and passed in the free-standing condition; so the manufacturer and contractor are asserting it should also be okay in the anchored condition since it has a larger section.  I would generally agree but again I’m struggling with where the rebar differences may be that were mentioned in Will’s email, so while we’d like to offer them some flexibility while they’re doing the jersey wall analysis we’re not sure this is the place for it.

Regarding adhesively bonding these barriers in the bolted condition, we’re not permitting the bonding method from one system to be used on another system as that isn’t how it was tested.  With that said, in Will’s other attached email he noted “the J-J Hook TCB itself does not have an approved adhesively bonded anchoring application that has passed the required MASH crash testing criteria” however for the F-shape there was an adhesive used in the crash test that’s noted in the TTI report.  I’m not sure if we’ve interpreted that correctly or if that was part of the F shape/jersey shape testing confusion that we’re in.  It looks to me that the J-J F-shape has an approved bonding method per the test though.

Lastly, and a bit of a pivot from the above questions.  With the F-shape (and possible others too) it seems there are variations in section and design and not just a consistent F-shape; like it’s dimensions can be adjusted somewhat.  Regarding those F-shape with pin/loop connections is there any concern with varying versions of the F-shape being used interchangeably in freestanding and/or anchored (pinned or bolted) scenarios?  Specifically I think this would the 12’/12.5’ length sections but we’re seeing top widths that vary from 8” to 9.5”.

I appreciate any insights you can provide on these questions.

Thanks

From the information you sent, I don’t see any reason that SCDOT cannot use the as-tested anchorage with the GDOT standard provided, The GDOT standard has equal longitudinal and shear reinforcement in the barrier and the same additional reinforcement in the area of the anchors. The main difference is the 1” additional top width and the 1.5” additional bottom width of the section. Use of the same reinforcement within a wider barrier section would tend to increase the capacity of the barrier section over the as-tested barrier. In general, use of an alternative anchored barrier section would be a concern if the barrier had lower structural capacity, lower mass, and/or an altered face geometry. In this case, the additional width would only serve to strengthen the section and add mass. Both of these factors would tend to reduce the demand on the anchors and improve performance.

In terms of the anchors themselves, it appears that the as-tested system used anchor bolts threaded into custom inserts that were installed in the concrete with a Hilti epoxy. I would not deviate from the as-tested anchors without further analysis or investigation. Altering the anchors may adversely affect performance. In general, we have allowed the use of anchors with equivalent or greater shear, tensile, and moment capacity to as-tested anchorage designs for systems we have developed. However, that requires an analysis of the as-tested anchors and some kind of analysis or demonstration of the capacity of the alternative anchorages. I don’t have enough detail on the custom anchors in this tested system and the proposed alternatives to make that determination here. EASISET or TTI may have more information with regards to the as-tested anchor capacities.

For your final question, the answer is similar to the first question above. The concern for alternative F-shapes would be if the barrier face geometry were changed and if the mass and/or structural capacity were reduced. Generally, if the barrier width is increased and the reinforcement is similar, then the barrier capacity and inertia are increased which would tend to provide similar or improved performance. For example, a 9” top width PCB with identical reinforcement to an 8” top width PCB would have increased moment and shear capacity due to the increased barrier width and wider rebar spacing. Additionally, the addition width would provide greater barrier mass. This mass would increase the barrier segment inertial resistance and friction which would reduce the barrier deflections and demand on the connection loops.

Let me know if that helps or if you have further questions.

Thanks!