Boeing 757
4000
3000
2000
1000
50 x 103
0
10
20
30
40
PCC Modulus (MPa)
a. Boeing 757.
5000
MD DC 9
4000
3000
2000
1000
50 x 103
0
10
20
30
40
PCC Modulus (MPa)
b. MD-DC9.
Figure 34. Effect of PCC modulus on the horizontal tensile stress at the
bottom of the PCC layer.
LOAD TRANSFER EFFICIENCY (LTE)
results. We used partial basin areas, but found no bet-
ter correlation. The following equation can be used to
Joints are generally weak points in jointed concrete
determine σh from the total basin area
pavements. Although the load transfer across joints has
a great effect on the stress at the bottom of the slab, and
σh = 7.35 AT
R2 = 0.7.
therefore on the performance of the pavement, it is
largely ignored in most evaluation schemes because of
The ISM can also be used to estimate σh, as shown
the difficulty of measuring these stresses (Foxworthy
in Figure 36. A power relationship was found to best
1985). The load transfer can be inferred from the
describe the relationship between ISM and (σh)
amount of deflection on both sides of the joint when a
load is applied on one side of the joint. The FWD, sim-
σh = 357,068 ISM0.8165
R2 = 0.81.
ulating a wheel load on one side of a joint, can be used
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