A six-lane concrete roadway is being designed for a metropolitan area. This roadway will be constructed on a subgrade with an effective modulus of subgrade reaction k of 170 lb/in3 . The ESAL used for the design period is 2.5 106 . Using the AASHTO design method, determine a suitable thickness of the concrete pavement (to the nearest 1 ⁄2 inch), provided that the working stress of the concrete to be used is 650 lb/in2 and the modulus of elasticity is 5 106 lb/in2 . Assume the initial serviceability is 4.75 and the terminal serviceability is 2.5. Assume the overall standard deviation, So, as 0.35, the load transfer coefficient J as 3.2, the drainage coefficient, Cd as 1.15, and R as 95%.
A six-lane concrete roadway is being designed for a metropolitan area. This roadway
will be constructed on a subgrade with an effective modulus of subgrade reaction k of
170 lb/in3
. The ESAL used for the design period is 2.5 106
. Using the AASHTO
design method, determine a suitable thickness of the concrete pavement (to the
nearest 1
⁄2 inch), provided that the working stress of the concrete to be used is
650 lb/in2 and the modulus of elasticity is 5 106 lb/in2
. Assume the initial serviceability is 4.75 and the terminal serviceability is 2.5. Assume the overall standard deviation, So, as 0.35, the load transfer coefficient J as 3.2, the drainage coefficient, Cd as
1.15, and R as 95%.
20-14 An existing rural four-lane highway is to be replaced by a six-lane divided expressway
(three lanes in each direction). Traffic volume data on the highway indicate that the
AADT (both directions) during the first year of operation is 24,000 with the following
vehicle mix and axle loads.
Passenger cars 50%
2-axle single-unit trucks (12,000 lb/axle) 40%
3-axle single-unit trucks (16,000 lb/axle) 10%
The vehicle mix is expected to remain the same throughout the design life of 20 years,
although traffic is expected to grow at a rate of 3.5% annually. Using the AASHTO
design procedure, determine the minimum depth of concrete pavement required for
the design period of 20 years.
R 95%
So 0.3
Cd 1.0
J 3.2
k 130
Ec 5 106
lb>in.2
S¿
c 650 lb>in.2
Pt 2.5
Pi 4
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