Methodology for Temperature and Load Compensation in Full-Scale Traffic Tests on Flexible Airport Pavements

Abstract

A methodology is described that is used to compensate for changes in wheel load and asphalt material temperature during full-scale traffic tests on flexible airport pavements. The method is based on a known failure and structural model describing failure due to rutting in the subgrade of a flexible pavement and the assumption that the pavement structure deteriorates according to the cumulative damage factor (CDF) relationship (Miner’s Rule). The test results are separated into portions during which the temperature is approximately constant and the wheel load is constant. The CDF for each portion of the test results is computed with the failure model fixed. But, by definition, CDF = 1.0 at failure and the failure model is allowed to move vertically until the CDF at failure = 1.0. The method has been applied to results from full-scale traffic tests run at the Federal Aviation Administration (FAA) National Airport Pavement Test Facility (NAPTF). Two examples are given. The first is a comparison of the performance of a conventional structure with the performance of an equivalent structure having an asphalt stabilized base and where the wheel loads are the same in both cases, but the temperature, and therefore the stiffnesses, of the asphalt layers changed during the tests. The number of passes to failure is also normalized to a standard temperature. The second example is normalization of the number of passes to failure to a standard load for a test in which the wheel loads varied over a range of 22.68 to 31.75 metric tons (MT) (50,000 to 70,000 lb). The test objective was to compare the performance of a six-wheel gear with that of a ten-wheel gear on the same structure. The compensation procedure allowed the results for both gears to be rationally compared, even though both experienced different loading histories. The first example assumes a linear failure model, allowing an analytic solution, and the second example assumes a non-linear failure model, requiring a numerical iterative solution procedure.