Research On Multiscale Mechanical Analysis Method And Model Of Asphalt Pavement

The damage behavior of asphalt concrete pavement is the most important and complicated problem in pavement engineering. In order to accurately and rationally describe the damage behavior of pavement, Mechanical theories and methodologies need to be employed to investigate the response of the pavement under dynamic loading. The multi-scale model is very powerful to determine the initiation and termination of the damage behavior. In this doctoral study, three aspects in the pavement structure dynamics were covered, including analysis and determination on dynamic parameters, dynamic response in asphalt pavement, and the multi-scale damage model of asphalt concrete, which were briefly introduced as follows:The composite material micromechanics theory was utilized to develop and analytic method to calculate dynamic modulus of asphalt concrete (E*). Both the self-consistent and generalized self-consistent methods were employed to calculate (E*) and the later one is found more proper to calculate E*through the comparison of calculation results. The self-consistent method provides irrational results when the inclusion contents in asphalt concrete is high. An analytical method to calculate dynamic modulus of asphalt concrete with aggregate gradation considered was proposed. The comparison between calculated and experimental values of E*indicates this analytical method can provide calculated E*having the same trend with the experimental E*while the loading frequencies change. However, there are still a quantitative differences between them. Therefore, an improved Hashion model with aggregate gradation considered was proposed to calculate E*. It is found that the improved Hashion model gives better prediction on E*while the predicted E*values lower than measured E*values. When the air voids in asphalt concrete was treated as cracks, the generalized self-consistent method provide simulated E*values slightly higher than measured E*values. The proposed generalized self-consistent method and the improved Hashion method in this study provide the upper and lower boundaries in calculating E*.An integrated procedure for asphalt concrete E*was proposed based on MATLAB platform, ABAQUS, ANSYS, PYTHON, and FORTRAN. The integrated procedure includes geometry modeling, finite element method (FEM) meshing, dynamic modulus calculation, post-processing and statistics analysis. The simulated E*with different space distributions of aggregates in asphalt concrete located in a range, which is similar to the range of measured E*, which demonstrates that E*has statistical characteristics, such as mean value and variance, which relates to the model size. The statistical model of E*were developed based on the relationship between specimen size and the statistical parameters, i.e., mean and variance of E*, which was obtained through50thousand numerical tests with different sizes of models.The3-dimensional FEM models were developed for different tires with different treads and the distributions of pavement-tire contact pressure for these tires were analyzed, which is useful when describing the dynamic response of pavement surface contacted with tires. It is found in the analyses that for all steel radial tires, when the loading increases to some degree, the longitudinal direction contact length increases as the loading increases while the contact pressure keep constant.The roughness of asphalt pavement was modeled and generated in a developed FEM program. In such program the rolling of tires on rigid pavement with roughness stimulus was simulated and the time-history displacement of the centroid of tire was provided. Based on implicit solution and experiment mutual interpolation technology, the tire-pavement coupling dynamic model was developed and applied to simulate and analyze the dynamic response of asphalt pavement. Furthermore, the pavement finite element model is established using triple-triple transition mesh element to save the cost of computation. Based on Hertz contact theory, a vehicle-tire-pavement coupled dynamic model was developed, which gives rational simulation, compared to the experimental results. The dynamic responses of aggregate and mastic in asphalt concrete under vehicle loading were investigated using multi-pole substructure technology under moving vehicle loading.A constitutive model was developed based on area weighting nonlocal and plastic coupling damage model to describe the local deformation band of asphalt concrete material. The constitutive model can successfully solve the problem of mesh dependence phenomenon. The potential size effect of asphalt concrete was simulated using the strain gradient theory, the results from which indicates hardening behavior of asphalt exists when the inclusion aggregate size is nanometer level. The macro-fracture behavior of asphalt concrete was analyzed based on extended finite element method (short for XFEM), with two fracture patterns covered, i.e., fatigue fracture and failure fracture.This doctoral study provides a numerical methodology to analyze the dynamic response and fracture behavior of asphalt pavement, and establishes a foundation to analyze the multi-scale damage behavior of asphalt concrete as well.