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Temporary barrier rail questions - Flare at Ends

Question
State	IA
Description Text	I ran something similar to this by you earlier this month, but that was the week before the pooled fund meeting. It may have gotten lost in the mad scramble to put the pooled fund meeting together, so I’ll run it by you again. We frequently taper our TBR if we are closing a lane for construction purposes. We do this by flaring TBR as shown. Has anchored TBR been tested on a flare (either NCHRP-350 or MASH)? If we can’t flare anchored TBR, could we use an unanchored flare and then transition to anchored TBR using the transition developed in TRP-03-180-06, something like what I show below? Or would you advise not using the transition for unanchored to anchored since it was developed for unanchored to rigid barrier? Thanks much!

Question

State

Description Text

I ran something similar to this by you earlier this month, but that was the week before the pooled fund meeting. It may have gotten lost in the mad scramble to put the pooled fund meeting together, so I’ll run it by you again.

We frequently taper our TBR if we are closing a lane for construction purposes. We do this by flaring TBR as shown.

Has anchored TBR been tested on a flare (either NCHRP-350 or MASH)?

If we can’t flare anchored TBR, could we use an unanchored flare and then transition to anchored TBR using the transition developed in TRP-03-180-06, something like what I show below? Or would you advise not using the transition for unanchored to anchored since it was developed for unanchored to rigid barrier?

Thanks much!

System Performance Evaluation

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Portable Barriers

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Date April 26, 2018
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Attachment Iowa PCB Flare-1.jpg Attachment Iowa PCB Flare-2.jpg

Response
Response (active)	There is not a lot of good research and guidance on termination of PCBs. The most common guidance used in chapter 4 of NCHRP 358. This guidance has flaring of the barrier as one of the end treatment options. However, little of the guidance in that document has been crash tested. One issue that was not discussed in that document was determination of the beginning and end of length-of-need for the PCBs. We recently did some work in that area for NDOT. https://mwrsf.unl.edu/researchhub/files/Report331/TRP-03-337-17.pdf This work did not consider flares, but it did attempt to define the beginning and end of length of need for the PCBs. We have proposed future research related to further investigation of proper methods for termination of PCBs. However, it has never been taken on by the DOTs. It terms of your items below, we do believe that you can flare the PCBs outside of the clear zone to terminate the barriers. This is one of the recommended methods in NCHRP 358. However, you may want to consider the LON study above when deciding how many PCBs you need outside of the redirective length of the system and the clear zone. Another option for the upstream end is to use and upstream anchor we previously developed through the Pooled Fund for the F-shape PCB. See the report attached. https://mwrsf.unl.edu/researchhub/files/Report63/TRP-03-209-09.pdf Anchored PCB has not been tested on a flare at this time. There may be some concerns with doing so in terms of barrier loading, vehicle snag on the PCB joints, and vehicle stability. Your lower figure could be an option, but the flared, unanchored portion might have to be significantly longer. There would be concerns that impact on barriers A-D may not safely redirect the vehicle with limited upstream barriers. Thus, you may need to provide for the minimum upstream LON barriers based on the report above outside the clear zone to ensure vehicle redirection along barriers A-D. Thanks

Response

Response
(active)

There is not a lot of good research and guidance on termination of PCBs. The most common guidance used in chapter 4 of NCHRP 358. This guidance has flaring of the barrier as one of the end treatment options. However, little of the guidance in that document has been crash tested. One issue that was not discussed in that document was determination of the beginning and end of length-of-need for the PCBs. We recently did some work in that area for NDOT. https://mwrsf.unl.edu/researchhub/files/Report331/TRP-03-337-17.pdf

This work did not consider flares, but it did attempt to define the beginning and end of length of need for the PCBs. We have proposed future research related to further investigation of proper methods for termination of PCBs. However, it has never been taken on by the DOTs.

It terms of your items below, we do believe that you can flare the PCBs outside of the clear zone to terminate the barriers. This is one of the recommended methods in NCHRP 358. However, you may want to consider the LON study above when deciding how many PCBs you need outside of the redirective length of the system and the clear zone.

Another option for the upstream end is to use and upstream anchor we previously developed through the Pooled Fund for the F-shape PCB. See the report attached. https://mwrsf.unl.edu/researchhub/files/Report63/TRP-03-209-09.pdf

Anchored PCB has not been tested on a flare at this time. There may be some concerns with doing so in terms of barrier loading, vehicle snag on the PCB joints, and vehicle stability.

Your lower figure could be an option, but the flared, unanchored portion might have to be significantly longer. There would be concerns that impact on barriers A-D may not safely redirect the vehicle with limited upstream barriers. Thus, you may need to provide for the minimum upstream LON barriers based on the report above outside the clear zone to ensure vehicle redirection along barriers A-D.

Thanks

Date April 27, 2018
Previous Views (151) Favorites (0)