A number of pavement structures experience deterioration due to high traffic volume and growing weights. Recently, the Texas Legislatures passed bills allowing trucks of gross vehicle weight (GVW) up to 556 kN routinely to use a route in south Texas along the Mexican border. Thus, there is a need to model pavement responses due to various types of overweight truck traffic (OTT) by taking into account axle loads, configuration, and pavement layer material characterizations in order to provide a guideline to assess the existing pavement performance and expected service life. It is for this purpose that the nonlinear cross-anisotropic pavement analysis finite element program (NCPA) has been developed. Stress dependent and directionally different resilient modulus and Poisson's ratios are incorporated into the finite element formulation to model the pavement response. As a tool to assess the performance of the pavement, the procedure to calculate the overall rutting and the cracked area was included in the formulation Intensive nondestructive testing has been performed to identify the existing pavement test section geometry and layer properties. In addition, a fiber optic based Weigh-in Motion (WIM) sensor was developed and tested. It is expected to be a promising device to monitor traffic by showing a reliable response. Sampled materials from the test section were tested to characterize their stress-dependent, cross-anisotropic and permanent deformation properties. Constitutive models are verified by comparing the predicted displacements with field displacements measured with the Multi-Depth Deflectometer (MDD). The result was that the least error between predicted and measured displacements is generated by the nonlinear cross-anisotropic model. In addition, the cross-anisotropic characteristic of the asphalt concrete material is introduced and evaluated based on the relationship between the backcalculated static and dynamic modulus. This addition improves the accuracy of the assessment of pavement performance with respect to both rutting and fatigue cracking. Charts to evaluate the service life of the existing pavement subjected to OTTs are established in terms of the unit service life consumed due to the rutting and fatigue cracking with the various observed combinations of pavement geometry, traffic load, and material properties.

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Simulative tests refer to the Full-scale accelerated pavement testing (APT) and laboratory wheel tracking testing, which are widely used for evaluation of pavement responses and performance under a controlled and accelerated damage conditions in a compressed limited time. This dissertation focuses on comparative evaluations under ALF, MMLS 3 and APA tests, in terms of rut depth, strain response, seismic stiffness, and contact stress using both experimental and numerical simulation results. Test slabs extracted from the ALF test lanes, are trafficked with the MMLS3 under comparable environmental conditions at laboratory in Virginia Tech. Some specimens were cut from the slabs for APA tests at VTRC. It is found that the monitored parameters yielded by the MMLS 3 test were comparable to the related full-scale ALF test results in terms of intrinsic material characteristics and pavement performance. The wireless sensor network based on Internet of things technology is implemented in laboratory for the MMLS 3 test, which provides a convenient solution for researchers on long-term observation and monitoring without being physically presented. The numerical simulations of ALF, MMLS 3 and APA in ABAQUS are used to supplement the investigation on the pavement response and performance under repeated moving loading. The viscoelastic-viscoplastic model is adopted to characterize rate and temperature dependent properties of asphalt mixtures. The 3D finite element models are capable of predicting the pavement response at critical locations while underestimates the rut depth because the permanent deformation induced by volumetric change cannot be represented in simulation. According to the test results, a power law function fits well for the accumulated rut depth versus number of load repetitions before the material reaches tertiary stage in MMLS 3 test. The rut depth development of APA tests exhibits a close-to-liner regression with number of load cycles after the initial 500 load repetitions. A regression model for predicting rut depth after 500 loads has a satisfying agreement with the experimental measurement. The calibrated MEPDG fatigue model can be used to estimate the allowable load repetitions in MMLS 3 trafficking. Besides, the effects of tire configuration, tire pressure, axle load amplitude, wheel load speed and temperature on pavement responses are investigated in this dissertation using the finite element model. It is concluded that MMLS 3 is an effective, economic and reliable trafficking tool to characterize rutting and fatigue performance of pavement materials with due regard to the relative structures. MMLS 3 test can be employed as the screen testing for establishing full-scale testing protocols as desired or required, which will significantly enhance economics of APT testing. / Ph. D.

There is a growing interest for the use of mechanistic procedures and analytical methods in the design and evaluation of pavement structure rather than empirical design procedures. The mechanistic procedures rely on predicting pavement response under traffic and environmental loading (i.e., stress, strain, and deflection) and relating these responses to pavement field performance. A research program has been developed at the Center for Pavement and Transportation Technology (CPATT) test track to investigate the impact of traffic and environmental parameters on flexible pavement response. This unique facility, located in a climate with seasonal freeze/thaw events, is equipped with an internet accessible data acquisition system capable of reading and recording sensors using a high sampling rate. A series of controlled loading tests were performed to investigate pavement dynamic response due to various loading configurations. Environmental factors and pavement performance were monitored over a two-year period. Analyses were performed using the two dimensional program MichPave to predict pavement responses. The dynamic modulus test was chosen to determine viscoelastic properties of Hot Mix Asphalt (HMA) material. A three-step procedure was implemented to simplify the incorporation of laboratory determined viscoelastic properties of HMA into the finite element (FE) model. The FE model predictions were compared with field measured pavement response. Field test results showed that pavement fully recovers after each wheel pass. Wheel wander and asphalt mid-depth temperature changes were found to have significant impact on asphalt longitudinal strain. Wheel wander of 16 cm reduced asphalt longitudinal strains by 36 percent and daily temperature fluctuations can double the asphalt longitudinal strain. Results from laboratory dynamic modulus tests found that Hot Laid 3 (HL3) dynamic modulus is an exponential function of the test temperature when loading frequency is constant, and that the HL3 dynamic modulus is a non-linear function of the loading frequency when the test temperature is constant. Results from field controlled wheel load tests found that HL3 asphalt longitudinal strain is an exponential function of asphalt mid-depth temperature when the truck speed and wheel loading are constant. This indicated that the laboratory measured dynamic modulus is inversely proportional to the field measured asphalt longitudinal strain. Results from MichPave finite element program demonstrated that a good agreement between field measured asphalt longitudinal strain and MichPave prediction exists when field represented dynamic modulus is used as HMA properties. Results from environmental monitoring found that soil moisture content and subgrade resilient modulus changes in the pavement structure have a strong correlation and can be divided into three distinct Seasonal Zones. Temperature data showed that the pavement structure went through several freeze-thaw cycles during the winter months. Daily asphalt longitudinal strain fluctuations were found to be correlated with daily temperature changes and asphalt longitudinal strain fluctuations as high as 650m/m were recorded. The accumulation of irrecoverable asphalt longitudinal strain was observed during spring and summer months and irrecoverable asphalt longitudinal strain as high as 2338m/m was recorded.

There is a growing interest for the use of mechanistic procedures and analytical methods in the design and evaluation of pavement structure rather than empirical design procedures. The mechanistic procedures rely on predicting pavement response under traffic and environmental loading (i.e., stress, strain, and deflection) and relating these responses to pavement field performance. A research program has been developed at the Center for Pavement and Transportation Technology (CPATT) test track to investigate the impact of traffic and environmental parameters on flexible pavement response. This unique facility, located in a climate with seasonal freeze/thaw events, is equipped with an internet accessible data acquisition system capable of reading and recording sensors using a high sampling rate. A series of controlled loading tests were performed to investigate pavement dynamic response due to various loading configurations. Environmental factors and pavement performance were monitored over a two-year period. Analyses were performed using the two dimensional program MichPave to predict pavement responses. The dynamic modulus test was chosen to determine viscoelastic properties of Hot Mix Asphalt (HMA) material. A three-step procedure was implemented to simplify the incorporation of laboratory determined viscoelastic properties of HMA into the finite element (FE) model. The FE model predictions were compared with field measured pavement response. Field test results showed that pavement fully recovers after each wheel pass. Wheel wander and asphalt mid-depth temperature changes were found to have significant impact on asphalt longitudinal strain. Wheel wander of 16 cm reduced asphalt longitudinal strains by 36 percent and daily temperature fluctuations can double the asphalt longitudinal strain. Results from laboratory dynamic modulus tests found that Hot Laid 3 (HL3) dynamic modulus is an exponential function of the test temperature when loading frequency is constant, and that the HL3 dynamic modulus is a non-linear function of the loading frequency when the test temperature is constant. Results from field controlled wheel load tests found that HL3 asphalt longitudinal strain is an exponential function of asphalt mid-depth temperature when the truck speed and wheel loading are constant. This indicated that the laboratory measured dynamic modulus is inversely proportional to the field measured asphalt longitudinal strain. Results from MichPave finite element program demonstrated that a good agreement between field measured asphalt longitudinal strain and MichPave prediction exists when field represented dynamic modulus is used as HMA properties. Results from environmental monitoring found that soil moisture content and subgrade resilient modulus changes in the pavement structure have a strong correlation and can be divided into three distinct Seasonal Zones. Temperature data showed that the pavement structure went through several freeze-thaw cycles during the winter months. Daily asphalt longitudinal strain fluctuations were found to be correlated with daily temperature changes and asphalt longitudinal strain fluctuations as high as 650m/m were recorded. The accumulation of irrecoverable asphalt longitudinal strain was observed during spring and summer months and irrecoverable asphalt longitudinal strain as high as 2338m/m was recorded.

The research presented in this thesis covers the development, calibration and verification of two thin surfaced unbound granular pavement models: one model to predict the response of a pavement to loading by the monotonic application of a single load event (Response model) and the other model to predict the accumulation of permanent deformation of the pavement when it is subjected to a large number of load applications (Performance model). The response model was developed using the finite element method and used an anisotropic stress dependent stiffness model to represent the granular and subgrade materials. The models were verified with an extensive set of stress, strain and surface deflection measurements collected at the CAPTIF facility. The calibrated models were able to predict the subsurface response of the pavement to a range of dual tyre and FWD load levels (23-72 kN). It was found that the measured stress and strain response of the pavement was different under the two loading mechanisms. It was also found that a particular response at a point in the pavement was linear with respect to load. The performance model was based on similarities observed in the performance of granular materials in both laboratory and full-scale experiments. When the specimen or pavement was showing a steady state response, it was found that the rate of accumulation of permanent deformation was related to the resilient strain. This relationship was then used to predict the deformation of CAPTIF pavements based on the outputs from the response model. The application of laboratory derived models required the use of shift functions to be able to be successfully used in replicating field measurements, this was expected given the differences in boundary conditions and loading mechanisms for the laboratory and field systems.

During the last two decades, environmental awareness and climate change concerns have encouraged and supported the implementation of recycled techniques in the Transportation Infrastructure Industry for rehabilitating and constructing pavements in the United States. Besides that, pavement roads are public goods that bring economic and social benefits to all countries. Therefore, assessing the pavement structural condition is essential to understand the performance of new materials and determine actions for conservation, maintenance, or rehabilitation. In-situ Pavement monitoring through embedded instrumentation is a type of monitoring technique, which uses several sensors installed within the pavement to obtain the structural responses used in Mechanical-Empirical design to control the performance and define asset management plans. This thesis presents the instrumented response of a Recycled Pavement Section on the Interstate 64 (located in Virginia, USA) to analyze the actual pavement responses (strain and stress) under real traffic and environmental conditions. Several sensors were installed during the construction (including strain gauges, pressure cells, thermocouples, and TDR probes), and two recycling techniques were used (CCPR and Full Depth Reclamation (FDR)) in this project. The Instrumented Recycled Pavement Section analyzed in this research was tested during five months in 2019 to evaluate the effect of temperature, sensor location, and load configuration on the pavement responses collected in the field. During the tests, three loaded trucks ran over the instrumented section. The results showed that the pavement structure is working properly, the stress responses decreased with depth, the maximum strain over the months was compared, and the temperature effect was addressed. Nevertheless, the stress and strain data obtained in each test presented a large variability because it is difficult to control the position where the trucks are passing during this type of experiment. Furthermore, the measured strains were useful to develop a calibrated pavement structural model, which showed that the pavement is expected to have a long structural service life. / M.S. / During the last two decades, different Departments of Transportation have been studying the implementation of recycled materials in pavement structure to provide better economic, environmental, and social benefits by addressing environmental challenges within the Transportation Infrastructure Industry. Among the emerging recycled techniques, Cold-Central Plant Recycling (CCPR) and Full Depth Reclamation (FDR) are included. Both procedures recollect and use the existing asphalt in the rehabilitation or reconstruction of the new pavement structure. The main benefits of pavement recycled materials include reduction of raw materials required and gas emissions. Nevertheless, recycled techniques are not commonly implemented due to the lack of information about long-term performance under real traffic and environmental conditions. In addition, since 2004, when the new Pavement Design Guide was released, the evaluation and validation of new materials require the understanding of the interaction between material properties, traffic, and climate. To address this concern, this thesis analyzed the pavement response measurements obtained in the Interstate 64 Widening Project (Virginia, USA), where two recycling techniques were used (CCPR and FDR). In this project, several sensors were installed during the construction to obtain information regarding the current environment condition (temperature and moisture) and pavement performance (stress and strain). The recycled pavement section was tested during five months of 2019 and trucks with known load configurations were implemented in the field tests. The results showed that the pavement structure is properly working, there is an acceptable stress distribution within the pavement layers, and the overall thickness is expected to have a long structural service life. Besides that, measured strain values obtained through the field experiment were compared with the theoretical ones obtained with computational tools.