Proceedings of the 12th International Conference on Concrete Pavements, 2021
On November 08, 2018, the Federal Aviation Administration (FAA) National Airport Pavement Testing... more On November 08, 2018, the Federal Aviation Administration (FAA) National Airport Pavement Testing Facility (NAPTF) completed a full-scale test on concrete airport pavements comparing joint types, as part of NAPTF Construction Cycle 8 (CC8). The objective of this experiment was twofold: (a) compare the performance of a new type of sinusoidal keyway joint with standard doweled longitudinal construction joints; and (b) compare the performance of doweled versus undoweled transverse contraction joints. The indoor test pavement consisted of twelve slabs divided into four groups according to the joint types. All four groups received traffic from a full-scale dual-wheel landing gear configuration using the FAA National Airport Pavement Test Vehicle (NAPTV). All test items were trafficked to failure. Performance of the joints was analyzed using data from heavy-weight deflectometer (HWD) tests and from embedded strain gages to determine load transfer values. For equal traffic, the sinusoidal ...
In airfields, reflective cracking is one of the major distresses in asphalt overlays which are pl... more In airfields, reflective cracking is one of the major distresses in asphalt overlays which are placed on rigid pavements, cracked asphalt pavements, and even in asphalt layers with cement-treated base pavements. Recently, a comprehensive laboratory testing program to characterize reflective cracking was conducted at the Federal Aviation Administration (FAA) NextGen Pavement Materials Laboratory. All tests were conducted on field extracted hot mix asphalt (HMA) cores. Test data from the customized overlay tester (OT) showed an excellent correlation between the Dissipated Energy (DE) and fracture parameters for specimens tested with different maximum crack opening displacement (or displacement rate). Parallel to the laboratory study, a finite element (FE) modeling effort was also carried out. The developed 2D FE model was not only capable of simulating the OT test but also accurately compute the fracture parameters, which consequently can be used to predict the fatigue performance of ...
International Journal of Geotechnical Engineering, 2013
Abstract Falling weight deflectometer (FWD) data are generally processed through backcalculation ... more Abstract Falling weight deflectometer (FWD) data are generally processed through backcalculation software for computing layer modulus of airport pavements. Though a number of backcalculation software are currently available, it is not known that software produces the most consistent and accurate results. Inconsistent and inaccurate backcalculation software can take a significant toll on the overlay and rehabilitation design of airport pavements as modulus being the inputs for such design calculations. Most backcalculation software requires an initial value of modulus, known as seed modulus, to initiate simulations. Unfortunately, in many of the software, the outputs vary with the initial choice of seed modulus (consistency). In addition, depending on the software algorithm, the final output differs from the laboratory measured value of modulus (accuracy). In this study, three backcalculation software programs are evaluated for consistency and accuracy. They are BAKFAA, MODULUS and EVERCALC. The major goal is to determine the most consistent and accurate software for determining layer modulus of airport pavements in New Mexico. Consistency of software is determined by comparing outputs from three sets of input data from FWD tests at identical locations with three magnitudes of loads: 40·03, 53·38 and 71·17 kN. Laboratory tests are conducted for modulus and tensile strength of asphalt and soil samples collected from the same locations of FWD tests. Software accuracy is determined based on the distribution and magnitude of the variance of laboratory and FWD modulus. Laboratory tensile stress is also compared with the backcalculated tensile stress using KENLAYER, a multilayer elastic analysis software. Study results show that EVERCALC software produces more consistent and accurate modulus values than the BAKFAA and MODULUS software. Therefore, EVERCALC is recommended for analyzing layer modulus of airport pavements.
AbstractThe falling weight deflectometer (FWD) testing develops a deflection basin on the pavemen... more AbstractThe falling weight deflectometer (FWD) testing develops a deflection basin on the pavement surface. Depths of this deflection basin from the center of the falling weight are measured at different radial offsets. These deflections are used for the backcalculation of the pavement layer moduli. Most of the available backcalculation software uses the layered elastic theory and static load to calculate moduli from known pavement surface deflections. However, the FWD test load is dynamic, and layer materials may show nonelastic behavior. Layered elastic theory in these types of software cannot characterize dynamic response of the pavement. Also, elastic theory is unable to accurately predict the surface deflection whenever stress developed in any pavement layer exceeds the yield point. For this reason, this study has performed a finite-element analysis of the airport pavement under the FWD test considering the dynamic load and materials plasticity. The analysis presented here includes elastoplastic beha...
Proceedings of the 12th International Conference on Concrete Pavements, 2021
On November 08, 2018, the Federal Aviation Administration (FAA) National Airport Pavement Testing... more On November 08, 2018, the Federal Aviation Administration (FAA) National Airport Pavement Testing Facility (NAPTF) completed a full-scale test on concrete airport pavements comparing joint types, as part of NAPTF Construction Cycle 8 (CC8). The objective of this experiment was twofold: (a) compare the performance of a new type of sinusoidal keyway joint with standard doweled longitudinal construction joints; and (b) compare the performance of doweled versus undoweled transverse contraction joints. The indoor test pavement consisted of twelve slabs divided into four groups according to the joint types. All four groups received traffic from a full-scale dual-wheel landing gear configuration using the FAA National Airport Pavement Test Vehicle (NAPTV). All test items were trafficked to failure. Performance of the joints was analyzed using data from heavy-weight deflectometer (HWD) tests and from embedded strain gages to determine load transfer values. For equal traffic, the sinusoidal ...
In airfields, reflective cracking is one of the major distresses in asphalt overlays which are pl... more In airfields, reflective cracking is one of the major distresses in asphalt overlays which are placed on rigid pavements, cracked asphalt pavements, and even in asphalt layers with cement-treated base pavements. Recently, a comprehensive laboratory testing program to characterize reflective cracking was conducted at the Federal Aviation Administration (FAA) NextGen Pavement Materials Laboratory. All tests were conducted on field extracted hot mix asphalt (HMA) cores. Test data from the customized overlay tester (OT) showed an excellent correlation between the Dissipated Energy (DE) and fracture parameters for specimens tested with different maximum crack opening displacement (or displacement rate). Parallel to the laboratory study, a finite element (FE) modeling effort was also carried out. The developed 2D FE model was not only capable of simulating the OT test but also accurately compute the fracture parameters, which consequently can be used to predict the fatigue performance of ...
International Journal of Geotechnical Engineering, 2013
Abstract Falling weight deflectometer (FWD) data are generally processed through backcalculation ... more Abstract Falling weight deflectometer (FWD) data are generally processed through backcalculation software for computing layer modulus of airport pavements. Though a number of backcalculation software are currently available, it is not known that software produces the most consistent and accurate results. Inconsistent and inaccurate backcalculation software can take a significant toll on the overlay and rehabilitation design of airport pavements as modulus being the inputs for such design calculations. Most backcalculation software requires an initial value of modulus, known as seed modulus, to initiate simulations. Unfortunately, in many of the software, the outputs vary with the initial choice of seed modulus (consistency). In addition, depending on the software algorithm, the final output differs from the laboratory measured value of modulus (accuracy). In this study, three backcalculation software programs are evaluated for consistency and accuracy. They are BAKFAA, MODULUS and EVERCALC. The major goal is to determine the most consistent and accurate software for determining layer modulus of airport pavements in New Mexico. Consistency of software is determined by comparing outputs from three sets of input data from FWD tests at identical locations with three magnitudes of loads: 40·03, 53·38 and 71·17 kN. Laboratory tests are conducted for modulus and tensile strength of asphalt and soil samples collected from the same locations of FWD tests. Software accuracy is determined based on the distribution and magnitude of the variance of laboratory and FWD modulus. Laboratory tensile stress is also compared with the backcalculated tensile stress using KENLAYER, a multilayer elastic analysis software. Study results show that EVERCALC software produces more consistent and accurate modulus values than the BAKFAA and MODULUS software. Therefore, EVERCALC is recommended for analyzing layer modulus of airport pavements.
AbstractThe falling weight deflectometer (FWD) testing develops a deflection basin on the pavemen... more AbstractThe falling weight deflectometer (FWD) testing develops a deflection basin on the pavement surface. Depths of this deflection basin from the center of the falling weight are measured at different radial offsets. These deflections are used for the backcalculation of the pavement layer moduli. Most of the available backcalculation software uses the layered elastic theory and static load to calculate moduli from known pavement surface deflections. However, the FWD test load is dynamic, and layer materials may show nonelastic behavior. Layered elastic theory in these types of software cannot characterize dynamic response of the pavement. Also, elastic theory is unable to accurately predict the surface deflection whenever stress developed in any pavement layer exceeds the yield point. For this reason, this study has performed a finite-element analysis of the airport pavement under the FWD test considering the dynamic load and materials plasticity. The analysis presented here includes elastoplastic beha...
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