APPENDIX 1—DESIGN EXAMPLES
USING PCA METHOD
A1.1—Introduction
The following two examples show the determination of
thickness for a slab-on-ground using design charts published
by PCA in Concrete Floors on Ground (2001). Both examples
select the thickness based on limiting the tension on the
bottom of the slab. The following examples are presented in
inch-pound units. A table for converting the examples to SI
units, along with an example of the process, is provided at
the end of the Appendixes.
A1.2—PCA thickness design for single-axle load
This procedure selects the thickness of a concrete slab for
a single-axle loading with single wheels at each end. Use of
the design chart (Fig. A1.1) is illustrated by assuming the
following:
Loading: axle load = 22.4 kips
Effective contact area of one wheel = 25 in.
2
Wheel spacing = 40 in.
Subgrade modulus k = 200 lb/in.
3
Material: concrete
Compressive strength = 4000 psi
Modulus of rupture = 570 psi
Design: Selected safety factor = 1.7
Allowable stress = 335 psi
Stress/1000 lb of axle load = 335/22.4 = 14.96 = 15
Solution: thickness = 7-3/4 in., as determined from Fig. A1.1.
Figures A1.2
and
A1.3
are also included for determining the
effective load contract area and for the equivalent load factor.
A1.3—PCA thickness design for slab with
post loading
This procedure selects the slab thickness due to loading by
a grid of posts shown in
Fig. A1.4
, such as from rack storage
supports. The use of the design chart (
Fig. A.1.5
) is illustrated
by assuming the following:
Loading: post load = 15.5 kips
Plate contact area for each post = 36 in.
2
Long spacing y = 100 in.
Short spacing x = 40 in.
Material: concrete
Compressive strength = 4000 psi
Modulus of rupture = 570 psi
k = 100 lb/in.
3
Fig. A1.1—PCA design chart for axles with single wheels.
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