Paper by WANG BRILL from ISCR 12th 2014 Prague Czech Republic
The Federal Aviation Administrations (FAA) National Airport Pavement Test Facility (NAPTF) conducts accelerated full-scale testing of airport pavements under controlled conditions. Construction Cycle 6 (CC6) was aimed at evaluating the effects of concrete strength and subbase materials. Two types of isolation joints were also tested for comparison. Data from embedded strain gages and deflection sensors were acquired and analyzed along with the observed performance data. The wander pattern for the traffic test consisted of nine discrete tracks. All sensor data were collected for each track and stored in a database. Traffic tests were simulated using the finite element method in three dimensions and compared with sensor readings. The effects of equivalent temperature gradient and interface contact were evaluated. It was found that the friction coefficients can greatly influence the difference in stress magnitude between the slab top and bottom. Therefore, this parameter needs to be carefully considered when attempting to match the observed sensor data. The CC6 test data show that strains under wheel loads were unsymmetrical with respect to the concrete slab neutral axis. It was found that the magnitude of strain at the slab top is greater than at the slab bottom for the same horizontal location. This was observed for two cases: (a) where the maximum tensile stress was at the slab bottom due to wheel loading directly over the gage, and (b) where the peak tensile stress occurs at the top of the slab, i.e., where the gage of interest is located on the neighbor of the slab receiving the principal loading.
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