AASHTO Rigid Pavement Design (Example).

1. A pavement for four-lane rural divided highway is to be
designed to last 25 years. During the first year, the estimated
two-way equivalent single axle application are 144,000. The
expected traffic growth rate is 3.5 percent. The design
reliability is 95 percent, and the overall standard deviation is
0.35. The initial serviceability po is expected to be 4.5, and
terminal serviceability, pt is 2.5.
The PCC pavement is to be laid on a granular subbase material.
The average compressive strength fc’ = 4900 psi, and average
modulus of rupture is 600 psi.
The drainage was judged to be fair and will be subjected to
moisture levels, approaching saturation, 10 % of time. The
effective modulus of subgrade reaction, (corrected for loss of
support) k is 110 psi.
Determine the design thickness.
Example
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2. Solution
1. The effective modulus of subgrade reaction = 110 psi.
(corrected for loss of support) k
2. The concrete elastic modulus Ec = 57000 * (fc’)0.5
= 3.99 * 10 6 psi
3. The concrete modulus of rupture Sc
’ = 600psi
4. The load transfer coefficient, J, = 3.2 (from table 20.10)
5. The drainage coefficient CD = 0.95 (from table 20.11)
6. R = 0.95
7. So = 0.35
8. Design Serviceability loss, ΔPSI =Po –Pt = 4.5 -2.5 = 2.0
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4.  Traffic in the design lane
W18 = DD * DL * w18
W18 = 0.5 * 0.9 * 144000 = 64800
Design ESAL =
[((1.35)25 – 1)/ 0.035] 64800 = 2.52*106
using the inputs given above in the nomograph, Figure 20.13
The design thickness can be determined
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1
1
1
T
r
r
T
n
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



 
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6. The design thickness is
slightly less than 9 inches
Round up to 9 inches.
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