Technical information

2-24
2.5 STRUCTURAL BEHAVIOR AT NCAT
2.5.1 Resilient Response
The resilient responses presented hereafter were obtained from Section N1 while in its
pristine state. The data was collected soon after construction, on November 7, 2003,
during which a single NCAT truck was doing multiple laps. The corresponding raw data
file provided by NCAT for the purpose of this study contained three such laps (see
Appendix A). Herein, the responses due to the first of the three passes is presented and
discussed.
Each time the truck approached the gauge array, the data acquisition system was
switched on and the gauge readings were recorded for a period of about 2 seconds.
Between truck passes, for a period of about 2 minutes, the data acquisition system was
switched off in order to save storage space. The pavement temperatures in different
depths during this experiment are reported in Table 2.5.1. The values in the table are
hourly averages, based on minute-by-minute readings, corresponding to the hour in
which the data files were created (personal communication, D. H. Timm, 2007).
Table 2.5.1: Temperature profile in Section N1 for analysis of resilient response data.
Depth, in. (mm) Temperature, ºF (ºC)
0 88.5 (31.4)
2 (51) 80.9 (27.2)
4 (102) 77.1 (25.1)
10 (254) 73.7 (23.2)
The following figures present the measured N1 responses to one truck pass as
recorded by the gauge array layout shown in Figure 2.4.3. In all figures the abscissa
represents test time and ranges between 0 and 2.2 seconds (the zero is arbitrary). In each
case circular markers denote NCAT data; the solid line passing between the data points
was created using cubic spline interpolation as means of increasing the ‘measurement’
density (this increased measurement density will be used later on in the report). It is
possible to identify and relate graphically the data in the charts to the specific axle. This
is done using the terminology in Table 2.4.1 where ‘1S’ refers to the steering axle, ‘1D’