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theses

The analysis of pavement responses is important for better understanding of pavement performance and accurate estimation of pavement service life. This dissertation aims to study flexible pavement responses using forward and inverse analysis. The first objective is development of axisymmetric finite element (FE) models that can simulate FWD loading on the pavement system. After that, the backcalculation of pavement layer moduli from FWD testing was studied by means of soft computing techniques such as Artificial Neural Networks (ANNs) and Genetic Algorithms (GA). The axisymmetric FE models were used to generate a synthetic database. The ANN-GA backcalculating program is developed to assess existing pavement condition after the training and verification using the synthetic database. The second objective of this dissertation is to investigate airfield flexible pavement responses under aircraft loading in consideration of the realistic aircraft tire–pavement interaction. An advanced three-dimensional (3-D) finite element (FE) model was developed to simulate heavy aircraft loading with high tire pressure. The aircraft loading was simulated as moving wheels having non-uniform contact stress distributions. Different tire rolling conditions caused by aircraft ground maneuvering were simulated, including free rolling, full-braking, and turning. The multi-wheel aircraft loading was modeled in two-wheel, four-wheel and six-wheel assembly. The analysis concludes that FWD deflections were affected by dynamic analysis, temperature gradient, bedrock depth, asphalt layer delamination, viscoelasticity, and unbound material nonlinearity. After validated with the field measurements in the long-term pavement performance program (LTPP) database, the developed ANN-GA program can be used to obtain damaged dynamic moduli of asphalt concrete and evaluate in-situ pavement conditions from structural point of view, which facilitates pavement overlay design procedure using Mechanistic-Empirical Pavement Design Guideline (MEPDG). The investigation on airfield flexible pavement emphasized the importance of considering non-uniform tire contact stresses and temperature profiles in airfield pavement analysis. For the aircraft ground maneuvering, aircraft braking or turning significantly increases shear failure potential in asphalt layer. The analysis of stress states would facilitate evaluation of the shear failure potential at airfield asphalt pavements. Finally, the investigation on multi-wheel aircraft loading indicates that the six-wheel gear configuration would cause more fatigue cracking and near-surface cracking potential than dual-wheel and four-wheel gears.

ETD_8452

Ph.D.

Includes bibliographical references

by Maoyun Li

doi:10.7282/T30K2CP7

ETD doctoral

The author owns the copyright to this work.