Slab On Grade 1

[Ryan H]

I have a 10" thick slab on grade with two mats of #4 @ 12" o.c. each way
from ACI min equations for temp and shrinkage, the slab has equivalent reinforcing.
As(min)=.0018(h)(bw)

I will have larger trucks parking on this slab so I wanted to check for punching shear. assuming a conservative tire contact area of 8"x8", and treating the tire as an interior column, I was able to calculate a design punching shear capacity of 91 kips which I feel is far sufficient for a single tire load.

What I would like to do is provide a PSF rating for the slab. I do not have a soils report but assuming 1500 psf bearing, I know the slab is fine when it comes to bearing pressure.

I know there are a lot of factors in slab design. But what I want to do is provide a conservative rating

I have generous control joints throughout as well

if anyone can help
Same building I have a 8" slab and 6" slab with single mats, I would like ratings for those as well

 

[canwesteng]

You should provide the axle load of the truck. I wouldn't provide a psf load, since only point loads will govern, but I guess you could take weight divided by the area of the truck

 

[Ryan H]

yea I guess I'm down a rabbit hole
All I know is the truck weight plus pay load is 60,000 lbs

I was told to check punching shear on the slab to confirm the tire weight was good. from that I calculated 91kips in capacity for the slab, the sound right?

 

[Once20036]

I`ve never provided a PSF rating for a slab, as it depends on too many factors.
If you have uniform storage over a huge area, it's a very uniform load and your concrete is just acting as a spacer as the load is delivered to the soil.
If you cut an aisle into the storage load, it will be the negative moment that controls the slab rating, and that moment depends on the aisle width.

Also, I disagree that this is a punching shear problem. The slab will crack and begin to deteriorate long before your wheel punches through the slab...
My go-to for this type of question is an old textbook by Ringo. I think he references a PCA method for wheel loads, but I don't have the text handy right now.

 

[Brad805]

Based on the GVW you can find the legal axle loads for that truck.

 

[GC_Hopi]

When it comes to traffic loads I found the best approach is to be specific. If you are check for a specific loading then state it, check for that, and state it is good for that load. Sounds like you are checking a HS20.

A few resources for pavement design (which is what I would call what you are doing) is ACI 360R, PCA, WRI, COE. Just google those organizations with slab on grade or pavement design.

And one interesting article for fun. How Full Can Concrete Trucks be when Driving on Slabs-on-Grade?

 

[atrizzy]

As far as I can tell, a maximum psf load for the slab would equal the psf capacity of the soil.

 

[dik]

You may want to look up the loading for an HS40 truck, or whatever the current vehicle is, or whatever the max vehicle you will have is... Using an average load based on the footprint does not even closely mimic your SOG. Also take a gander at:

https://www.cecalc.com/References/AASHTO Pavement Design.pdf

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

I agree with GC_Hopi that communication is the key. The engineering is fairly straightforward: 15-20 tonne axle and 1200-2500 psf distributed, depending on ground stiffness & concrete grade, and assuming the ground can take it. This assumes load transfer at joints or sufficient edge thickening.

But, tyre contact pressure is more like 15,000 psf so people might freak out if you tell them 1,500 psf. Send them a picture like GC_Hopi's.