TM
10 18
(2) The required concrete thickness is first determined using the current design procedure presented in
TM
88-7, Chap. 3 as a starting point. Assuming an E value of 10,000 psi for the
soil, four
concrete thicknesses were selected as shown in table 7-2, and the maximum stresses were computed using JULEA
computer program for all the axle configurations. The stresses are tabulated in column 4 of table 7-2. Since load
transfer is not considered in roads and streets for concrete pavements as wheel and track loads travel along the
concrete slab edges, stresses computed with codes such as JULEA (interior stresses) do not simulate the edge
stress condition and thus the computed stresses will be multiplied by a factor of 1.33. The modified stresses are
shown in column 5 of the table. Assuming a
strength R for the concrete of 675 psi and a
of
80, the allowable coverages were computed using equation 5-l. The damage is computed as the ratio of design
coverage to the allowable coverage
and is presented in column 8 of the table; the cumulative damage for
design thicknesses of 6, 7, 8, and 10 inches is 58.6, 3.8, 0.2, and 0.0, respectively. A plot of these values indicates
a required concrete thickness of 7.2 inches for a damage factor of one. This thickness value would be rounded off
to 7.5 inches for design.
7-3
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