overlay design 2

[fyaure]

If there is a pavement which has been made 10 years back but none of its design specifications and other design data are avaiable now. Traffic has increased tremendously over these years. the exisiting pavement does show some stress cracks but is still fuctioning.
So, my question is is there any standard conservative procedure to assume some original design values, calculate percent damage and then design an overlay?
I guess there are some other criteria I will have to address, please tell me what else I need to know to do that?

 

[ACtrafficengr]

Find someone with a falling weight deflectometer, have them thump it, calculate the moduli, and go from there...

FWD owners tend to be universities and a few state DOT's.

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[fyaure]

Thank you for your suggestion. Even when I find Mr(resilient mod.) value for the existing layer, I do not know reliability factor (which I will assume anyways) and old ESAL which I will need to find the SN.
Is it okay to just design for the new pavement starting from the basics (but keeping the base and subbase layer thickness same) and then add the asphalt layer on the old pavement to bring it upto the thinkness from new calculation.
Also, since you must have experience with this kind of work, can you tell me from experince(without any calculations)if overlay is worth it when the previous pavement was designed for light traffic whereas new pavement has to be designed for heavy-duty loads?
Totally ripping off the whole pavement and starting fresh might be agood idea economically when performance is not to be compromised???

 

[Ron]

Design the section as a new one, then go in and use what you have in place, considering the structural layer coefficient for the asphalt will be about 50 percent of its original value which was probably 0.42 to 0.44

Don't worry about old ESAL for getting SN....use new values and iterate accordingly.