# Pavement Question



## PEREADY (Aug 22, 2011)

I am designing a 15" thick rigid pavement. The govering crane outrigger load is about 200 kips on 1.5' x 1.5' area. How do I decide whether I need both top &amp; bottom reinforcement or only top reinf. is good enough? I would really appreciate your response. Thanks


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## MA_PE (Aug 22, 2011)

PEREADY said:


> I am designing a 15" thick rigid pavement. The govering crane outrigger load is about 200 kips on 1.5' x 1.5' area. How do I decide whether I need both top &amp; bottom reinforcement or only top reinf. is good enough? I would really appreciate your response. Thanks


if anything you would only need bottom reinforcement under the outrigger pad because bending would cause tension on the bottom and not the top.

Also for a concentrated load like that you need to check punching shear so the outribber doesn't just go through your slab.

you say "rigid pavement". Is this a slab on grade? What is the supporting material below the slab? how stiff is it? how well compacted?

What is it's bearing capacity?

In other words, how long a span do you need to carry the 200kips for?

Is that 200k a working load or a factored ultimate load?


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## IlPadrino (Aug 22, 2011)

MA_PE said:


> Is this a slab on grade? What is the supporting material below the slab? how stiff is it? how well compacted? What is it's bearing capacity?


In my experience with mobile cranes, the problem with outriggers is tied to bearing capacity of the soil underneath the pavement (rigid or flexible). One failure that comes to mind was a punch through the 8" concrete because of soil washed away at the edge of a concrete slab.


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## PEREADY (Aug 23, 2011)

MA_PE said:


> PEREADY said:
> 
> 
> > I am designing a 15" thick rigid pavement. The govering crane outrigger load is about 200 kips on 1.5' x 1.5' area. How do I decide whether I need both top &amp; bottom reinforcement or only top reinf. is good enough? I would really appreciate your response. Thanks
> ...




Thanks for your respond. Yes, it is a slab on grade. 200 kips is factored load. I checked the punching shear. The soil underneath has 300 pci subgrade modulus &amp; slab panels are approx 20' x 16' with dowel bars.


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