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Development of TL-3 Transition Between Concrete Barrier and Guardrail

Question
State CT
Description Text I found an excerpt about the subject project and I’m very interested in obtaining additional information. Not sure if you remember me …I have attended a few Task Force 13 meetings in the past. In any event, I created a detail to transition guiderail to TPCBC that has been used a bit here in CT and its gaining popularity with the contractors and designers. For me to have any wide spread use of it or for me to be able to make it a standard detail, I need to find crash test information to support its use.

As it turns out, there isn’t a large amount of information for this application. However, I did find your project, details from Virginia DOT in their GRIT manual, a detail from Oregon, and one from Georgia. I have attached my detail for your use and information. Specifically, if you can help I am looking for the following:

1. Does the barrier the rail is attached to need to be anchored? Does more than one barrier need to be anchored?
2. Is a rubrail required?
3. Can this detail be used for both Jersey shape and F-shape TPCBC?
4. Is it necessary for the element to be 10ga?
5. Are block outs necessary?

Thank you for any time or input you can give.
Keywords
  • Approach Guardrail Transitions
  • Guardrail
  • Temporary Barriers
Other Keywords none
Date September 13, 2013


Response
Response

I am currently working on the guardrail to TCB transition project that we have through NDOR. I would agree with you that there is very little testing or previous development of these kinds of transitions. We are working on a transition between G4(1S) guardrail and the F-shape PCB used by the majority of the Midwest Pooled Fund states. Currently we are conducting LS-DYNA simulations of various design alternatives. The work is not yet complete, but I can make sure to get you the report when it is finished in near the end of 2013/beginning of 2014.

 

As for your questions, see below.

 

1.       Does the barrier the rail is attached to need to be anchored? Does more than one barrier need to be anchored?

a.       We are currently attempting to transition between the barriers without anchoring the TCB sections. We are not finished with the analysis, but it appears reasonable that it could be done. However, we currently are overlapping the guardrail past the flared TCB segments approximately 2-3 TCB segments. In addition, we are mounting spacer blocks between the rail and PCB to improve their interaction in the region were they overlap. We have also used a kicker beam off the end of the TCB to get the end of the system moving more quickly. It appears that you are attempting to connect the two systems end to end. We were concerned about this type of installation due to concerns with snag on the TCB end. We also believe that it is important to get the TCB and guardrail moving together near the end of the system to prevent pocketing.

2.       Is  a rubrail required?

a.       It may help reduce snag on the TCB end in your case. We have not observed issues with vehicle snag on the end of the barrier in our design iterations as we have overlapped the two systems sufficient to prevent it.

3.       Can this detail be used for both Jersey shape and F-shape TPCBC?

a.       Because the design you have shown has not been tested, I cannot recommend its use. I would have concerns with the stiffness transition used and snag on the end of the TCB section as it is shown in the detail. However, I do believe that a design that was successfully tested for F-shape barrier may be acceptable for NJ shapes as well depending on the design of the TCB section and the connections.

4.       Is it necessary for the element to be 10ga?

a.       We are currently looking at both single and nested systems with thrie beam and W-beam. Both types have shown some advantages and disadvantages depending on the design of the transition. Thus, I can’t say with certainty whether or not the 10 gauge rail or nesting is necessary.

5.       Are block outs necessary?

a.       The blockouts on the W6x8.5 posts can only help in this installation.

 

I don’t want to provide too much guidance on your design until we have a chance to finish the analysis we are currently doing. That said, I would have some concerns with the lack of overlap of the guardrail and PCB, the potential for snag on the end of the PCB section, and the use of the quarter post spacing between the weak posts and the TCB.

 

Thanks

 

Date December 10, 2013


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