Slab on grade; concentrated loads

[RHB51]

When a concentrated load is placed on a slab on grade
how do you determine the soil pressure distribution
and if the pressure is within the allowable soil limits?
Since the slab confines the soil the allowable bearing pressures typically listed for a soil such as clay become
much larger.

 

[Ussuri]

If I remember correctly you can use Boussinesqs Equation to calculate the stress within the soil at any depth and radius from your applied load. I think the Newmark chart is based on boussinesqs equation so you could maybe try one of those.

 

[jike]

The way to find out the bearing pressure would be to run a finite element analysis or beam on elastic foundation. Various software packages have this capability.

Typical concentrated loads may be wheel loads from fork trucks or post loads from racks, equipment or platforms. Design charts are available for wheel loads and post loads in "Designing Floor Slabs On Grade" by Ringo and Anderson.


For the lighter concentrated loads, bearing pressures often are not of much concern as is the positive and negative bending in the slab. If the slab is designed properly for bending, it often can spread the load out sufficiently for bearing pressure.

 

[haynewp]

Look at PCA mats if you are considering software.

http://www.pcastructurepoint.com/soft/soft_profile.asp?l_family_id=20

 

[structuresguy]

The Army Coprs of Engineers has a slab on grade design manual which is pretty good. Go the to army corps website, and search for manuals. I don't have the link anymore, sorry.

PCA also publishes a manual for designing slabs on grade. It is also good.

 

[Ron]

A slab on grade is simply a pavement. Analysis is done using Boussinesq or variations of same. PCA method for pavement analysis will give you what you want or you can use an elastic layer analysis program such as ELSYM5 or CHEV-PC....they're both old, DOS based and available in the public domain....but they are pretty accurate.