Structural Issues with AC over JPCP pavements with PCTB Layers in AASHTOWare 2.5


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5 weeks ago by
Hello Everyone,

I am a graduate student at Kanas State University. I have been working on AC over JPCP pavements. The AC over JPCP pavements in Kansas typically have AC>JPCP>PCTB>LTSG>Subgrade cross sections. The JPCP thicknesses are typically arount 9- 12 inches, and the PCTB thicknesses are around 4.0 inches. I could model and run this type of pavements in AASHTOWare 2.3 version. However, I have recently upgraded the software to the AASHTOWare PMED 2.5 version and the new version shows an error message as "For AC rehabilitation and semi-rigid designs, the structure must have a base layer." One solution I came to know of is to add a 2.0 in. non-stabilized beneath the PCTB with Mr value close to the subgrade. There might not be significant difference in prediction due to presense of thick AC and PCC layer on top. I am looking for other ideas from the intellectual minds here.

Any suggestion how to resolve this issue. Thank you everyone in advance.

Shuvo.



1 Answer


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5 weeks ago by
The reason you are getting this error message is due to the limitations and requirements of the reflection cracking model in Pavement ME. The model requires that a pavement structure must at a minimum have a surface layer, non-stabilized base layer, and a subgrade layer. The software did not check for these requirements in Version 2.3.1 in the software and were added to this years release to ensure appropriate results. Upon review of your section, you can add a 2 inch granular non-stabilized base layer with a resilient modulus similar to that of the subgrade layers. Please see the example below. The impact of the 2 inch non-stabilized layer should not be significant because the stiffness of the asphalt and concrete layers will carry most of the load.


- Wouter Brink via Chadwick Becker

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I'd like to note that this also came up as an issue in beta testing for v2.5. As a result we have just completed developing a fix so that the user does not have to add the extra layer themselves, the application will do it for them as described in the answer above. This should be available in v2.5.1
written 5 weeks ago by Chadwick  
Thank you very much Chadwick for the detailed answer. I still have results from the 2.3.1 version. I would run the projects again adding the non-stabilized based with version 2.5. Let's see how they turn up. I appreciate your help.
written 5 weeks ago by Shuvo Islam  
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