135
would affect the FWD deflections and vice versa (see Section 4.2).
Error analysis of these equations revealed that predictive errors were
generally below 20 percent, with most cases actually being less than 10
percent. The highest errors occurred with Equation 4.25, and the least
in Equation 4.29. This trend was in agreement with that of the R2
values.
The lowest and least number of prediction errors always occurred
using the equations with Dg as an independent variable(s). These are
Equations 4.27 and 4.29. The FWD sensor for D measurement is located
o
72.0 in. from the center of the loading plate and is not a conventional
sensor spacing. The high degree of prediction accuracy with this sensor
deflection emphasizes the need to incorporate its measurement in the FWD
test system. However, in the absence of Dg, Equation 4.28 which incor
porates both Dg and D? would be the best equation compared to the
others. With the use of two sensor deflections, this equation should
minimize the potential for prediction error due to measurement
variability.