Concrete Slab on Grade Analysis Calculator (for Post or Wheel Loading)
For Slab Subjected to Interior Concentrated Post or Wheel Loading
Assuming Slab is Reinforced for Shrinkage and Temperature Only
Check Bearing Stress on Dowels at Construction Joints with Load Transfer:
1. "Load Testing of Instumented Pavement Sections - Improved Techniques for Appling the Finite Element
Method to Strain Predition in PCC Pavement Structures" - by University of Minnesota, Department of Civil
Engineering (submitted to MN/DOT, March 24, 2002)
2. "Dowel Bar Opimization: Phases I and II - Final Report" - by Max L. Porter (Iowa State University, 2001)
3. "Design of Slabs-on-Ground" - ACI 360R-06 - by American Concrete Institute (2006)
4. "Slab Thickness Design for Industrial Concrete Floors on Grade" (IS195.01D) - by Robert G. Packard
(Portland Cement Association, 1976)
5. "Streses and Stains in Rigid Pavements" (Lecture Notes 3) - by Charles Nunoo, Ph.D., P.E.
(Florida International University, Miami FL - Fall 2002)
there will be a few situations where certain combinations of the Concentrated
Load, P, Subgrade Modulus, k, and Contact Area, Ac, result in a #N/A error message
and thus no solution for the minimum slab thickness, t(min), for one or more of the
equations listed above. For those cases, the user would then manually iterate the
input slab thickness to determine the minimum value if desired.
|Subgrade Soil Types and Approximate Subgrade Modulus (k) Values|
|Type of Soil||Support Provided||k Values Range (pci)|
|Fine-grained soils in which|
silt and clay-size particles
|Low||50 - 120|
|Sands and sand-gravel|
mixtures with moderate
amounts of silt and clay
|Medium||130 - 170|
|Sands and sand-gravel|
mixtures relatively free
of plastic fines
|High||180 - 220|
|Cement-treated subbases||Very high||250 - 400|
|Truck Rated Capacity (lbs.)||Total Axle Load (lbs.)||Wheel Spacing (in.)|
Note: Axle loads are given for trucks handling the rated loads at 24 in.
from load center to face of fork with mast vertical.
|Slab Depth||Dowel Dia., db||Total Dowel Length||Dowel Spacing (c/c), s|
|5" - 6"||3/4"||16"||12"|
|7" - 8"||1"||18"||12"|
|9" - 11"||1-1/4"||18"||12"|
|< 3/4" Aggregate||> 3/4" Aggregate||Slump < 4"|
It is a linear dimension and represents mathematically the 4th root of
the ratio of the stiffness of the slab to the stiffness of the foundation.
Concrete Strength, Modulus of Rupture, Srinkage Coefficient,
|f 'c (psi)||MR (psi)||e (in./in.)|
1. For 6" to 10" thick slabs on grade with 'k' values between 100 pci and 200
pci, the increase in stress, 'i', due to a 2nd wheel (or post) load as a
percentage of stress for a single wheel (or post) load is approximately
15% to 20% for a wheel (or post) spacing of 3' to 4'.
2. For wheel (or post) spacings of 5' to 15', the increase in stress is
approximately 0% to 5%.
3. For a single post load, input a value of i = 0%.
4. For situations outside of the above criteria and/or for a more in depth
analysis and evaluation of the effects of a 2nd wheel (or post) load, please
refer to the "BOEF.xls" (Beam On Elastic Foundation) spreadsheet workbook.
Disclaimer: This calculator is not intended to be used for the design of actual structures, but only for schematic (preliminary) understanding of structural design principals. For the design of an actual structure, a competent professional should be consulted.
‘Calculations courtesy of Alex Tomanovich, PE ’