Concrete Slab on Grade Thickness Analysis

For Slab Subjected to Concentrated Post Loading (for k = 100 pci)
Per PCA "Slab Thickness Design for Industrial Concrete Floors on Grade" - Figure 7b, page 10

Instructions for Use of Figure 7b:
1. Enter chart with slab stress =
2. Move to right to eff. contact area =
3. Move to right to post spacing, y =
4. Move up/down to post spacing, x =
5. Move to right to slab thickness, t

Input Data

Concrete Strength, f 'c =		psi
Subgrade Modulus, k =		psi
Post Load, P =		lbs.
Post Spacing, y =		in.
Post Spacing, x =		in.
Load Contact Area, Ac =		in.^2
Factor of Safety, FS =		in.

Result :

Effective Contact Area, Ac(eff) =	in.^2	Ac(eff) = determined from Figure 5, page 6
Concrete Flexual Strength, MR =	psi	MR = 9*SQRT(f 'c) (Modulus of Rupture)
Concrete Working Stress, WS =	psi	WS = MR/FS
Slab Stress/1000 lb. Post Load =	psi	Ss = WS/(P/1000)
Slab Thickness, t =	in.	t = determined and input from Figure 7b above

Note: ;User MUST determine slab thickness from
Figure 7b, and input the result in cell Slab Thickness, t.

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 ’