UFC 3-260-02
30 June 2001
Table 11-4
Bituminous Concrete Moduli for Each Month for Conventional Flexible Pavement Design Based
on Bituminous Concrete Strain
Design Pavement
Dynamic Modulus
Average Daily Mean
*E**
Air Temperature,1
Temperature,2
103 psi
degrees F
degrees F
Month
Jan
47.5
56
1,500
Feb
50.7
60
1,270
Mar
58.0
67
920
Apr
66.1
76
570
May
73.3
84
360
Jun
80.5
92
220
Jul
83.1
95
180
Aug
82.7
95
180
Sep
77.3
89
260
Oct
67.2
77
540
Nov
56.2
65
1,000
Dec
49.3
57
1,400
1
Determined from local climatological data for Shreveport, LA.
2
Estimated from 5-inch bituminous concrete thickness curve in Figure 6-1. (In design for bituminous
concrete strain, the average daily mean air temperature is used as the design air temperature for
entering Figure 6-1.)
Conversion Factors: degrees C = degrees F - 32/1.8, millimeters = 25.4 inches
(1) The horizontal strain at the bottom of the asphalt layer and the vertical strain at the top of
the subgrade are computed for each traffic grouping shown in Table 11-5. The data needed for input
into the JULEA computer program for the computation of asphalt and subgrade strains for the
760-millimeter (30-inch) pavement structure for a taxiway design are given in Table 11-6. Note that the
input contains data for one run, but four runs would be required to compute the subgrade data, i.e., one
run for each grouping to account for variation in asphalt modulus. The strain is computed considering
only two of the four main tires; the transverse spacing of the tires is sufficiently large to prevent an
overlapping effect for the other two tires. The individual tire loading is computed by considering
90 percent of the gross load on the main gear, equally distributed between the four tires of the main
gear, resulting in a weight on each tire of 15,820 kilograms (34,875 pounds). The radius of the loaded
area is computed as a circle having an area equal to the tire contact area. A contact area of
0.258 square meters (400 square inches) results in a radius of the contact area of 28.6 millimeters
(11.28 inches). The pavement system is a five-layer system having full friction between layers. For a
11-13
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