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We are developing a project where we are proposing to use a side-mounted version of the MGS bridge rail on a 17" thick slab bridge that is located on the NHS.  Please review the attached memo, detail, and analysis and provide any comments or concerns.  Note: adhesive anchor values are from the HILTI Product Technical Guide for the HIT-RE 500-SD Epoxy Adhesive Anchoring System.

I'm curious whether you think this minor change from the tested system would require approval from FHWA. 

Also, I'm open to any suggestions you might have!

As Dr. Faller has indicated, we are currently in the process of adapting the side-mounted, weak post MGS system to culvert headwalls.  The headwall we are attaching to is 18 in. in height.  Thus, our current study is very similar to your situation.  In fact, one of the 3 design concepts we are working with is very similar to the one you have proposed (we only use 4 attachment bolts were you have used 6).

My first question to you is... How soon do you need this system?  I ask because we will be testing and evaluating our design concepts relatively soon (hopefully spring of 2012).  If that timeline would work for you, I would recommend waiting for these test results and utilizing our tested side-mounted design configuration.   If you need an answer quicker than that, we can take a close look at your proposed design.

If we were to wait and incorporate your system, do you see any potential issues with the fact that our slab is one inch shallower (17" vs. 18") than what you will be testing with?

If our side-mounted design proves to cause no significant damage to the culvert headwall, I do not see the 1" difference in thickness/height causing any issues.  The current design does not extend to the bottom of the 18" tall headwall, thus all components would be the same for your situation.

I'll check with our Bridge Office and see if they'd like to hold off for awhile.

The system noted by Scott Rosenbaugh was successfully evaluated to MASH TL-3 impact conditions. Results of the research study and the design of the culvert connections are shown in:

https://mwrsf.unl.edu/reportResult.php?reportId=293