69
6.4 Analysis of shear stiffness
This section deals with analysis of shear stiffness data. The sensitivity of shear
stiffness to various mix and test parameters is investigated using statistical analysis, and
surrogate models are developed for the prediction of dynamic shear stiffness and shear
loss stiffness.
6.4.1 Surrogate models for shear stiffness
The shear stiffness model development procedure followed is similar to that used
for axial stiffness characterization. The models presented in this section are the general
model for shear stiffness (| G*|), shear loss stiffness ( G"), and shear stiffness
Hz
G
10
* at
10 Hz frequency.
Table 6- 2 through Table 6- 4 provides summary of regression analysis for the
various models. The shear stiffness models based on GLM are as follows:
At 10 Hz frequency
10.7313 105 exp( 0.04504 0.05947 0.34265 0.1564 ) 2 0.71
10
G* = ´ - AC + GR - Temp - Va R =
Hz
( 6.2)
For variable frequency
G* = 4.297 ´ 105 exp( 0.05805AC + 0.08957GR - 0.57338Temp - 0.1703Va ) × ( Freq) 0.4775 R2 = 0.91 ( 6.3)
G" = 1.496 ´ 105 exp( - 0.0195AC + 0.04779GR - 0.32727Temp - 0.13927Va ) × ( Freq) 0.3091 R2 = 0.71 ( 6.4)
where,
| G* | , G"= shear stiffness, and shear loss stiffness in psi;
AC = asphalt content: - 1 and + 1 for opt.- 0.5% and opt.;
GR = aggregate gradation: - 1 and + 1 for SP 12.5- mm and SP 19- mm;
Va = air void content in percent;