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I have a project that has issues with a curved beam guard installation (see below).  My initial comments to them are:

Should not use curved beam guard with curb and gutter because there is a good chance that the rail will fail during an impact.

Kinks in rail will concentrate stresses making it more likely that the rail will fail.

Plan (PDF title 40) has the beam guard too far back from the curb, making it likely that the errant vehicle will jump over or submarine the rail.

Beam guard flare near 68+75 LT on the plan is likely too steep and will likely fail during an impact.

Beam guard in radius should likely have breakaway holes installed.  After a certain point during the impact the post should break away from the ground or the beam guard will become a ramp.

My questions to you are:

Are my recommendations above valid?

What are the typical radius that beam guard can be bent to (e.g. 5 or 10 ft increments)?

Can manufactures bend beam guards to any radius (e.g.  53' radius)?

As requested, I am sending some photos of the guardrail installation concerns and summary of the conversations had with Highway Landscapers and Gregory Products.  The photos represent the southeast and southwest corners of CTH C and the Northeast Frontage Road.  Bends in the guardrail were the result of pushing the rail into the posts to meet the existing radius.  I have attached the plan page showing the radii to the flange of the curbs.  We placed the guardrail along the face of the curb rather than at the provided radius so that they would perform appropriately.  Therefore, the 55' and 60' radii would have been 53' and 58' for the face of curb.  When we discussed our concerns with Highway Landscaping, they initially told us that only 20', 40, and 50' radii can be provided.  I am not sure what they used, because the panels are not marked and checking the chord length would now represent the installed radius.  Gregory Products is their supplier and I found the attached list on their website that shows 5' increments being available.   I also spoke with the regional sales person from Gregory to confirm this was the case.  He was reluctant to provide too much information because Highway is a customer of his.  He noted that the installation method is common and kinks sometime occur, but also that they should have had the material sizes they needed for this particular radii.

We also have been having panels delivered that are not on the approved list.  Highway tells us that these panels had only recently been tested in the yard, and that is why they are not on the list yet.  On the EFR, we needed to test in the field because they were never tested at the yard.  We are still waiting to see if we need to do the same on the WFR.  One of our concerns is whether the contractor is getting the appropriate stockpiling of material in time to test properly and delivery correct radii to the specific projects.  Our EFR was an urgent need as Highway replaced Andrews, and we wonder if they grabbed whatever they had available to get it installed in time.  And, what they had available was not the radii identified in the plan.

From our findings at this point, we are proposing that we add to the project punch list that the SE and SW quadrants be replaced with appropriate radii for the EFR and CTH C guardrail.  Any other suggestions, comments, questions?

1.       The installation shown has radii in the 50' to 60' range for the curved sections. The radii shown here are too small to be treated as standard longitudinal barrier and its location adjacent to the intersection will potentially subject the rail to high angle impacts like a short-radius system. As you know, there are no acceptable, tested TL-3 short-radius guardrail designs at present. TTI has received FHWA acceptance of the Yuma Country short-radius guardrail for TL-2. Additional information on short-radius guardrail design was given by FHWA in the memo titled, "Curved W-Beam Guardrail Installations at Minor Roadway Intersections - T 5040.32". I cannot tell what design speeds you are dealing with for this installation, but I would recommend that the Yuma County system be used in this area as it currently represents our best guidance and state of practice with regards to short-radius guardrail systems. The radii here are larger than those in the FHWA memo or the standard Yuma county design. However, I believe that adapting the Yuma County design over to a larger radii is likely your best option. The TTI report and the design details is below.

A. Abu-Odeh, K. Kim, D.C. Alberson. Evaluation of Existing T-Intersection Gaurdrail System for Equivalency with NCHRP Report 350 TL-2 Test Conditions. 405160-10. Texas Transportation Institute, College Station, TX. August 2010.

2.       I would agree that the guardrail system not be used with a curb and gutter. Previous testing of standard w-beam guardrail with curb has shown the potential to either vault the vehicle over the rail if the offset from the curb is significant or the potential  to increase rail loads and rupture the guardrail.

3.       The kinks in the rail that you saw are not a huge concern in terms of stress concentrations. However, the rail manufacturers should be able to fabricate a rail that matches the design radii much more closely than what you have shown. In addition, it appears that the posts do not fit up to the rail in the correct locations, which is causing the system to be field modified with additional post bolt holes in the rail. This would be a cause for concern with respect to proper release of the post from the guardrail.

4.       We would recommend that the rail flares outside the radii follow the guidance in the RDG. Thus, the recommended flare is likely very shallow.

5.       The posts in the radius will perform better if they are breakaway posts. See the Yuma County details mentioned previously.

6.       As I noted before, the manufacturers should be able to make various radii for the guardrail. We have ordered radiused guardrail several times in the past and have not had issues getting a certain size. However, manufacturers may want to limit the potential sizes to certain ranges to simplify fabrication.