or, with respect to total basin area, an estimate could be

and also because of the small database. However, be-

made using

cause of the unique relationship between JTE and LTE

shown in Figure 45, it may be possible to apply the

σtensile = 7.35*A*T

same relationship to longitudinal joints.

where σtensile = horizontal tensile stress at the bottom

To meet the criterion that the LTE of the joint be not

of the PCC layer (kPa)

less than 25%, the JTE should exceed 80%. If this is the

case, a review of Tables 11a and 12a indicates that

(MN/m3)

many of the joints at CWA and OCA were below capac-

ity during the thawing period. At the end of thaw, nearly

The LTE across transverse joints can be estimated from

all of them met the 25% criterion. The results indicate that

the JTE from Figure 47 or from the following equation

most of the damage to transverse joints probably occurs

during the winter and spring thawing period.

where *JTE *is the joint transfer efficiency (decimal)

δu

δi

and δu is FWD deflection on an unloaded slab and δi is

ment performance during the thaw-weakening periods

FWD deflection on a loaded slab.

using FWD deflection data. From this study, we found

2500

2000

1500

1000

500

0

200

400

600

Total Basin Area (mm 2 )

50

that, for PCC pavement, the composite subgrade mod-

ulus (base and subgrade) can be estimated from the de-

flection basin area and Figure 46 or from the following

40

equation

30

where *E*sub is the subgrade modulus (MPa), and ∆ is

deflection basin area (mm2). The horizontal tensile

20

stress at the bottom of the PCC layer was found to be a

function of pavement thickness and *E*sub or the coeffi-

cient of subgrade reaction (*k*) from the following equa-

10

tions for either a Boeing 757 or for a MD-DC9.

σtensile = 7360 1.5*E*sub 17*t*

0

20

40

60

80

100

σtensile = 7389 3.02*k * 17.5*t*

Joint Transfer Efficiency (%)

37