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From page 73... ... The prediction of the endurance limit from the round-robin data shows small differences based on binder grade and asphalt content. The rankings from the uniaxial tension tests are the reverse of those determined from the beam fatigue tests. Read the entire page →
From page 74... ... For the triple trailer, the average steer axle weight was 10,680 lbs, the average weight of the tandem drive axles was 40,610 lbs, and the average weight of the single-axle trailer ranged from 20,550 to 21,010 lbs. For the five-axle single trailer, the steer axle weighed 11,550 lbs, the tandem drive axles weighed 33,850 lbs, and the tandem rear axles weighed 32,900 lbs (73) Read the entire page →
From page 75... ... Cracking apparently began in the overlying layer. Shift Factors Based on Measured Strain The eight structural sections from the 2003 NCAT Test Track were instrumented to measure in situ strain in the asphalt, compressive stresses in the unbound layers, and moisture and temperature as a function of depth in the pavement structure (72) Read the entire page →
From page 76... ... 76 Figure 7.3. Typical gauge array for 2003 NCAT Test Track structural sections (72) Read the entire page →
From page 77... ... . The regression constants for the 2003 NCAT Test Track 19.0-mm NMAS base mixes, based on the beam fatigue tests conducted as part of this study are shown in Table 7.6. Read the entire page →
From page 78... ... The temperature data from the 2003 cycle of the NCAT Test Track were used for the PerRoad analysis. Figure 7.5 shows a frequency distribution of the air temperature data. Read the entire page →
From page 79... ... The modulus values used for determining shift factors for the test track sections and subsequent sensitivity analyses are presented in Table 7.11. where, MMPT = mean monthly pavement temperature, °F, MMAT = mean monthly air temperature, °F, and MMPT MMAT Z Z = + + ⎛⎝⎜ ⎞⎠⎟ − + +1 1 4 34 4 6 41( ) Read the entire page →
From page 80... ... Frequency distribution of air temperature data for the 2003 NCAT Test Track. Table 7.11. Read the entire page →
From page 81... ... The MEPDG provides the predicted (50% reliability) bottom-up fatigue cracking, termed maximum cracking, and the predicted cracking at some level of reliability, in this case, 81 Section Shift Factor Based on All Seasons Shift Factor Neglecting Summer Season N1 13.4 6.7 N2 45.0 19.2 N6 17.6 NA NA = Not applicable because Section N6 went through two summer seasons. Read the entire page →
From page 82... ... MEPDG predicted cracking for Sections N2 and N6 (PG 67-22) , 2003 NCAT Test Track. Read the entire page →
From page 83... ... Summary of Observed Shift Factors from 2003 NCAT Test Track Structural Sections The observed shift factors based on the performance of the 2003 NCAT Test Track structural sections are summarized in Table 7.14. Based on the measured strains and the PerRoad analyses, the shift factor for the PG 67-22 mix at optimum asphalt content exceeds the assumed shift factor of 10.0. Read the entire page →
From page 84... ... and 35 in. were required for the PG 67-22 and PG 76-22 mixes at optimum asphalt content to achieve predicted cracking performance similar to that achieved when an endurance limit was considered (for maximum cracking of 0% to be predicted at the end of 40 years) Read the entire page →
From page 85... ... ( ) The second set of analyses examined the sensitivity of the MEPDG and PerRoad to the measured endurance limit using the NCAT Test Track traffic. Read the entire page →
From page 86... ... Pavement design simulations were conducted using the PG 67-22 mix at optimum asphalt content, the previously described pavement design parameters, and three levels of the endurance limit: 70 ms, 100 ms, and the measured (151 ms) endurance limit. Read the entire page →
From page 87... ... Figure 7.13 shows a comparison of the conventional and perpetual design thicknesses. The PerRoad perpetual design using the measured endurance limit of 151 ms is slightly less thick than the 40-year empirical design using the 1993 AASHTO Design Guide. Read the entire page →
From page 88... ... recommendations that long-life pavements should range between 7.9 and 15.4 in. Further, Section N3 and N4 of the 2003 NCAT Test Track have now gone through two test track loading cycles without any observed fatigue cracking (77) Read the entire page →
From page 89... ... . The proposed upper bound for a cumulative frequency distribution of endurance limit strain is shown in Table 7.17 for Sections N3 and N4 of the NCAT Test Track. Read the entire page →
From page 90... ... test temperature used for the beam fatigue tests. Hence, the fact that the 50% strain values are greater than the endurance limits measured for this study is not unexpected. Read the entire page →

From page 73...

... The prediction of the endurance limit from the round-robin data shows small differences based on binder grade and asphalt content. The rankings from the uniaxial tension tests are the reverse of those determined from the beam fatigue tests.