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Cable Barrier Adjacent to Slope

Question
State NE
Description Text Could we simulate a cable guardrail 2' from the edge of a 2:1 slope?

Was this simulated a few years ago with the NCHRP 350 vehicles when the testing was performed on the flat to a 1.5:1 slope?


What effect will using the MASH 09 vehicles have on these previous simulations?


I would like to keep the front tire on the slope by simulating our typical cross section a 4% shoulder slope in front of the guardrail. The 2' behind the cable we normally break to a 6:1, then the 2:1 slope.


When we place cable guardrail 2' from a 2:1 our plan specifies S 3 x 5.7 x 7' posts with soil plates on 16" max. spacing.


The new inline end section is what we would use in the future to anchor this " if this makes a difference.


What would help this placement?


Closer post spacing?
Keywords
  • Guardrail
Other Keywords none
Date June 4, 2010


Response
Response

I will try to address some of your questions below with my responses in red.


Could we simulate a cable guardrail 2' from the edge of a 2:1 slope?


Yes, we can simulate the cable guardrail 2' from the edge of a 2:1 slope. We proposed similar research regarding a low-tension version of the 4 cable median barrier at this year's Pooled Fund meeting. The cost for this kind of analysis would be in the $35K range to do the analysis. If you want to formally address this, we can develop a proposal and budget. The simulation analysis will provide guidance on this issue, but full-scale testing will likely be required in order to fully address this issue.

Was this simulated a few years ago with the NCHRP 350 vehicles when the testing was performed on the flat to a 1.5:1 slope?


The simulation effort for the 1.5:1 slope was done using Barrier VII and would not address some of the slope changes you are proposing.
The previous analysis looked solely at the effect of reducing the post spacing on barrier deflection and did not address the interaction of the vehicle and slope.

What effect will using the MASH 09 vehicles have on these previous simulations?


Using the 2270P vehicle would likely result in additional barrier deflection. In addition, the higher CG for the 2270P vehicle could potentially adversely affect the capture of the vehicle we saw in our previous testing of the 2000P adjacent to the 1.5:1 slope.


I would like to keep the front tire on the slope by simulating our typical cross section a 4% shoulder slope in front of the guardrail. The 2' behind the cable we normally break to a 6:1, then the 2:1 slope.

When we place cable guardrail 2' from a 2:1 our plan specifies S 3 x 5.7 x 7' posts with soil plates on 16"max. spacing.


This type of installation could be modeled. However, based on our previous experience with the 2000P testing on 1.5:1 slope, the cable barrier might require reduced post spacing to effectively capture the vehicle.


The new inline end section is what we would use in the future to anchor this " if this makes a difference.


What would help this placement?


Lots of factors including, cable tension, post spacing, cable spacing, and post offset could all have effects on this type of installation.


Date June 13, 2010


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