Ill
Case 2. For 3.0 < t < 8.0 in.,
l
log (Ei)
1.4506 19.6499 log (D D ) + 32.5256 log (D D )
12 13
- 18.6215 log (D D ) 4.78148 log (D D )
14 15
Eqn. 4.19
(N = 320 and R2 = 0.979)
Case 3. For 4.5 < t < 8.0 in.,
l
log (E ) = 1.79194 10.8459 log (D D ) + 13.6157 log (D D )
- 3.65434 log (D D )
1 4
Eqn. 4.20
(N = 240 and R2 = 0.993)
The above equations hold for their respective range in tx values
and the following range in moduli:
75.0 < E < 1200.0 ksi, 42.5 < E < 85.0 ksi,
l 2
30.0 < E < 60.0 ksi, and 5.0 < E < 40.0 ksi.
3 4
The accuracy and reliability of these equations will be discussed later
using both theoretical and field FWD deflection measurements.
4.3.3.2 Prediction Equations for E2. The sensitivity analysis
presented in Section 4.2 suggested that it would be difficult to develop
E2 prediction equations from FWD deflections. This was due to the
relative lack of sensitivity of E on the theoretical FWD deflection