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I participate in a Traffic Control Review Team here at KDOT where we go out and look at projects under construction. Mostly I ride along to review general roadside safety, TCSB, temporary guardrail, etc. types of installations.
One thing that has come up this year that hasn't come up before has to do with our free standing TCSB installations. I noticed, in some cases, the contractors weren't tensioning the free standing TCSB after it had been placed and the pin was dropped through the loops (i.e. the pin could be freely removed if I lifted it out with my hand). From other conversations on this topic, my recollection is best practice is to tension or pull the barrier tight after installation so it will immediately engage a vehicle during an impact. Is that correct?
When I looked back through the original Temporary Type F3 crash testing report I didn't see the tensioning or pulling mentioned there and I didn't find a question where this had already been asked on the consulting site so now I'm not sure what the best practice is; tension the TCSB or just set it and drop the pin where the pin can be freely removed. I guess my thought is if the barrier isn't tensioned there may be a delay in the barrier engaging the vehicle and the working widths might be greater compared to a pre-tensioned or pulled installation.
Any guidance will be helpful. Just as a side note I noticed my old e-mail is still registered with the Pooled Fund Member's only site. If you respond via e-mail my new e-mail is firstname.lastname@example.org.
|Other Keywords||tension, stretch, pull, tighten|
|Date||June 21, 2017|
|Response||We typically recommend and test our PCB installations with the joints pulled tight. As you noted above, this helps the barriers engage more quickly when impacted.
The F-shape PCB that KDOT uses was tested this way as well in both the NCHRP 350 and MASH tests. Thus, we recommend installation of the barriers in a similar manner in the field. It is believed that not pulling the joints tight will not adversely affect the overall performance of the barrier to redirect vehicles. However, there may be some increase in deflection and working width if the barrier segments take longer to engage. The magnitude is a little difficult to estimate without further analysis, but it may be in the 10%-20% increase range.
|Date||June 23, 2017|
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