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TRP-03-337-17

Question
State KS
Description Text

I wanted to ask a clarification question on Report TRP -03-337-17, Length of Need and Minimum System Length for F-Shape Portable Concrete Barrier. My understanding from the report is 5 barrier sections are needed downstream of the beginning of the LON for free-standing TCSB intallations. My question is related to reducing or eliminating the need for these 5 sections.

KDOT's previous practice has been to eliminate the barrier sections upstream of the beginning of the LON if the installation is fully restrained. Is that still acceptable?

Additionally, I was curious to know if the 5 sections were still needed if the last 12'-6" section of TCSB was fully restrained or anchored with an impact attenuator, but the rest of the installation was free standing with the overall length of the installation still meeting the 9 section minimum. Please contact me if you have any questions.

Thanks,

Tom Rhoads

785-296-0322

thomas.rhoads@ks.gov

Keywords
  • End Treatments & Crash Cushions
  • Temporary Barriers
Other Keywords LON, TCSB
Date August 4, 2017


Response
Response The PCB LON research noted that a minimum of three barriers were needed upstream of the beginning of LON and a minimum of five barriers were needed downstream of the end of the length of need in order to safely redirect vehicles under MASH TL-3 impact conditions. 

The potential exists to shorten the no. of required barrier segments on the upstream end using an anchorage system developed previously that was tested to MASH TL-3. See report below.

http://mwrsf.unl.edu/researchhub/files/Report63/TRP-03-209-09.pdf

We have also developed roadside and median transition systems for attaching the ends of the PCB to a rigid parapet. These options could be used on either end of a PCB installation. 

http://mwrsf.unl.edu/researchhub/files/Report54/TRP-03-208-10.pdf

http://mwrsf.unl.edu/researchhub/files/Report133/TRP-03-180-06.pdf

Attachment to an impact attenuator or crash cushion might be feasible, but to my knowledge no testing of transitions to those systems has been conducted. Because you are connecting free-standing PCB to a fixed attenuator, some form of stiffness transition between the two systems would likely be needed. It would seem reasonable the one could use a similar stiffness transition to those used to transition from free-standing PCBs to a rigid parapet. However, consideration of the attachment of the PCBs to the attenuator and mitigation of snag at that connection would need to be considered. This may vary depending on the type of attenuator used.

MwRSF has not designed approach transitions to any proprietary attenuators at this time. 
Date August 11, 2017


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