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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.
This volume gathers the latest advances, innovations, and applications in the field of accelerated pavement testing (APT), presented at the 6th International Conference on Accelerated Pavement Testing, in Nantes, France, in April 2022. Discussing APT, which involves rapid testing of full-scale pavement constructions for structural deterioration, the book covers topics such as APT facilities, APT of asphalt concrete and sustainable/innovative materials, APT for airfield pavements, testing of maintenance and rehabilitation solutions, testing of smart and multi-functional pavements, data analysis and modeling, monitoring and non-destructive testing, and efficient means of calibrating/developing pavement design methods. Featuring peer-reviewed contributions by leading international researchers and engineers, the book is a timely and highly relevant resource for materials scientists and engineers interested in determining the performance of pavement structures during their service life (10+ years) in a few weeks or months.
Abstract: A research study was conducted to evaluate the response of aged flexible airfield pavements at varying ambient temperatures using the Falling Weight Deflectometer (FWD). Eight field tests were performed on three sites at Duke Field, Florida, at pavement surface temperatures ranging from 30 to 130.F. Monthly subgrade moisture readings were taken along with the measuring of pavement temperature profiles during each test. Laboratory tests were conducted on collected asphalt concrete and sand asphalt cores. Tests included low-temperature rheology tests, indirect resilient modulus, and indirect static creep tests (fracture energy). The analysis of the test data provided a reliable and effective method for predicting the asphalt modulus and fracture energy using asphalt viscosity and air void content. Back calculation of layer moduli using measured FWD data was performed by the layered elastic computer program BISDEF. The asphalt concrete modulus (E1)was computed using the developed asphalt modulus prediction equations which BISDEF iterated for the base and subgrade layer moduli. This technique greatly reduced the errors in determining E1 from the iteration process. Uncracked segments of pavement gave good results using the prediction equations for all asphalt layers. However, adjustments to E1 were necessary to accommodate the degradation of modulus due to pavement cracking. Dissertation Discovery Company and University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Evaluation and Response of Aged Flexible Airfield Pavements at Ambient Temperatures Using the Falling Weight Deflectometer" by Charles William Manzione, was obtained from University of Florida and is being sold with permission from the author. A digital copy of this work may also be found in the university's institutional repository, IR@UF. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation.
This study utilized Illinois DOT (IDOT) mechanistic-empirical (M-E) technology and Mn/ROAD mainline pavement section data and information to verify/refine/modify IDOT M-E analysis and design concepts and procedures for full-depth asphalt concrete (FDAC) and conventional flexible pavements (CFP). The Mn/ROAD mainline flexible pavements include eleven CFP and three FDAC pavement sections. Four different granular materials were used in the conventional flexible pavements. A fine-grained soil subgrade (R-value of about 12) is present throughout the mainline. Laboratory material testing results, field distress measurements, and FWD test data were used to study pavement deflection response and performance (rutting and asphalt concrete fatigue). The study demonstrated that the IDOT M-E analysis and design procedures for FDAC and CFP sections are adequate. The ILLI-PA VE structural model adequately predicts the pavement responses. The use of bi-linear (arithmetic) subgrade model and the "theta" granular material model ILLI-PA VE inputs closely replicate CFP field FWD deflection responses. The effect of granular material quality on CFP deflection response is very limited. The ILLI-PAVE FWD backcalculation algorithms are adequate for estimating the moduli of asphalt concrete and sub grade soils.
A research study was conducted to evaluate the response of aged flexible airfield pavements at varying ambient temperatures using the Falling Weight Deflectometer (FWD). Eight field tests were performed on three sites at Duke Field, Florida, at pavement surface temperatures ranging from 30 to 130 deg F. Monthly subgrade moisture readings were taken along with the measuring of pavement temperature profiles during each test. Laboratory tests were conducted on collected asphalt concrete and sand asphalt cores. Tests included low- temperature rheology tests, indirect resilient modulus, and indirect static creep tests (fracture energy). The analysis of the test data provided a reliable and effective method for predicting the asphalt modulus and fracture energy using asphalt viscosity and air void content. Back calculation of layer moduli using measured FWD data was performed by the layered elastic computer program BISDEF. The asphalt concrete modulus (E1) was computed using the developed asphalt modulus prediction equations which BISDEF iterated for the base and subgrade layer moduli. This technique greatly reduced the errors in determining E1 from the iteration process. Uncracked segments of pavement gave good results using the prediction equations for all asphalt layers. However, adjustments to E1 were necessary to accommodate the degradation of modulus due to pavement cracking. Theses.
This text/software package explores the structural analysis and design of highway pavements - focusing on the mechanistic-empirical design procedures rather than the purely empirical methods. *presents the theory of pavement design and reviews the methods developed by several organizations, such as the AASHTO, the AI, and the PCA. *includes the KENLAYER program for flexible pavements - applicable to a multilayered system under stationary or moving multiple wheel loads with each layer being either linear elastic, nonlinear elastic, or viscoelastic. *contains the KENSLABS program for rigid pavements - applicable to multiple slabs fully or partially supported on a liquid, solid, or layered foundation with moment or shear transfer across the joints. *presents most of the advanced theory and detailed information in appendices. *features a large number of examples and line drawings.
Mechanistic design concepts for conventional flexible pavement (asphalt concrete (AC) surface + granular base/subbase) for highways are proposed and validated. The procedure is based on ILLI-PAVE, a stress dependent finite element computer program, coupled with appropriate transfer functions. Two design criteria are considered: AC flexural fatigue cracking and subgrade rutting. Fatigue cracking is controlled by limiting the tensile strain at the bottom of the AC layer. Subgrade rutting is controlled by limiting the stress-ratio at the granular layer-subgrade interface. Algorithms were developed relating pavement response parameters (stresses, strains, deflections) to AC thickness, AC moduli, granular layer thickness, and subgrade moduli. Extensive analyses of the AASHO Road Test flexible pavement data are presented supporting the validity of the proposed concepts.