Concrete Slab on Grade 1

[cmkujawa]

I need to design a 4' wide by 35' long concrete slab on grade. I've done floor slabs elevated, but never a slab on grade and not sure really were to go with it or how to design. I planned on using 4,000 psi conc with wwf for reinf. any help would be appreciated.

Thanks

 

[SperlingPE]

Good sub-grade
Joints to control cracking
panels should be square or nearly square
joints should be at least 1/4 depth of slab
Make sure mesh is in iproper location

 

[cmkujawa]

Yeah I have good subgrade about 2500 psf, and plan on having joints at 12 feet. other than dead load from the concrete and I one point load of 100lbs, how do I show it in calculation.

 

[JAE]

And don't use mesh....total waste of time as the mesh ends up in the dirt.

 

[cmkujawa]

Thanks for the advice on the mesh, however I am still looking at how to design the slab on grade. for example if I have a 100lb/ft live load and dead load of concrete, how do I calculate proper depth of slab and proper steel reinf.

 

[samdamon]

cmk-

see ACI 360R for sog design data, ACI 302.1R for sog construction reccomendations.

 

[twinnell]

What is loading the slab? Equipment? Foot traffic? If it is equipment, how much of the equipment footprint covers the slab?

 

[cmkujawa]

The only loading is the dead load of the concrete and a set of stairs in which the only part of the stairs that connects into the concrete is the absolute bottom ot the 2 stair stringers. The stairs go in one run from the concrete to the 2nd floor. Any help would be appreciated since I wont be able to buy the ACI 360R book till next week. Thanks also for the advice from others.

 

[dik]

You might consider joints @6' max.(sawcuts) with actual filled joints @ 12' or 18'. There was an earlier thread on design loads. Problem is not from uniform loads, but from point loads. Base material should be well compacted and uniform in elevation as well as density.

Dik

 

[twinnell]

Is this slab interior or exterior?

It sounds like you should have two structual items. 1) A stair support footing. 2)And a standard slab on grade, 4" thick with 6x6-w1.4xw1.4 WWF. Essentially you have a sidewalk.

Or place the slab on grade with a thickend slab under the stair support. Typical thickened area is 1'-6" wide by width of stairs + 6". Add 2-#4 in the bottom of the thickened portion.

Slab on Grades are generally not designed unless there are heavy equipment or moving industrial loads on them. Or garages for heavy trucks.

Google it, you should find some tables that give the suggested thickness and reinforcing for various loads.

 

[cmkujawa]

Thanks Twinnell, I used to always just go by the rule of thumb and those charts, but just being new I didnt know if there was more detail into it or not.

 

[Lutfi]

Go to this link. It has nice cad details and many articles on concrete parking lot designs. The design on SOG is similar to concrete parking lots.

http://www.concreteparkinglots.com/

FC&PA used to give lots of good handouts on this subject as well. It may be worth while to contact them. They also have CAD details for typical SOG and parking lots and driveway designs.


Regards,
Lutfi

 

[ropo48]

Is this soil expansive? On light slabs, expansive soils usually cause more damage than loads. I would use an E.J. @ the stair landing slab to isolate it from the other 40'