Concrete Slab on Grade Analysis Calculator (Wall Loading)

For Slab Subjected to Continuous Line Loading from Wall

Input Data

Slab Thickness, t = in.
Concrete Strength, f 'c = psi
Subgrade Modulus, k = pci
Wall Load, P = in.

Result :

Design Parameters:
Modulus of Rupture, MR = psi MR = 9*SQRT(f 'c)
Allow. Bending Stress, Fb = psi Fb = 1.6*SQRT(f 'c) (as recommended in reference below)
Factor of Safety, FS =   FS = MR/Fb
Section Modulus, S = in.^3/ft. S = b*t^2/6
Modulus of Elasticity, Ec = psi Ec = 57000*SQRT(f 'c)
Width, b = in. b = 12" (assumed)
Moment of Inertia, I = in.^4 I = b*t^3/12
Stiffness Factor, l =   l = (k*b/(4*Ec*I))^(0.25)
Coefficient, Blx =   Blx = coefficient from "Beams on Elastic Foundations" by M. Hetenyi
Wall Load Near Center of Slab or Keyed/Doweled Joints:
Allowable Wall Load, Pc = lb./ft. Pc = 4*Fb*S*l
= 12.8*SQRT(f 'c)*t^2*(k/(19000*SQRT(f 'c)*t^3))^(0.25)
Wall Load Near Free Edge of Slab: psf Pe = Fb*S*l/Blx
= 9.9256*SQRT(f 'c)*t^2*(k/(19000*SQRT(f 'c)*t^3))^(0.25)
Min. req'd. slab thk. for center or keyed/doweled joints:
t(min) = in. Set Pc(allow) = 12.8*SQRT(f 'c)*t^2*(k/(19000*SQRT(f 'c)*t^3))^(0.25)
Min. req'd. slab thk. for free edge load:
t(min) = in. Set Pe(allow) = 9.9256*SQRT(f 'c)*t^2*(k/(19000*SQRT(f 'c)*t^3))^(0.25)

"Concrete Floor Slabs on Grade Subjected to Heavy Loads"
       Army Technical Manual TM 5-809-12, Air Force Manual AFM 88-3, Chapter 15 (1987)

Disclaimer: This calculator are 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

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
Low50 - 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
Note: direct solution for t(min) has been rounded up to nearest 1/4" thickness.
Note: direct solution for t(min) has been rounded up to nearest 1/4" thickness.