Multiscale Dynamic Behavior And Damage Evolution Of Asphalt Deck Pavement Under Vehicle-Bridge Interaction

Asphalt deck pavement is in a more complex service state due to the dynamic vehicle-bridge interaction.Cracks,ruts,bumps and other damages occur prematurely during the operation period of the bridge,which greatly shortens its service life.Asphalt mixture is a heterogeneous temperature sensitive material composed of coarse aggregates,asphalt mastic,mortar and voids.Its viscoelastic properties are of great importance to study the failure mechanism of bridge deck pavement.The vehicle-bridge interaction and the complex mechanical properties of asphalt mixtures increase the difficulty of dynamic analysis of deck pavement.Moreover,it is hard to explain the complicated dynamic evolution from material changes to structure changes by single-scale macromechanical analysis.It is necessary to investigate the mechanical behavior of viscoelastic asphalt pavement under vehicle-bridge interaction and the cross-scale damage evolution process from material failure to structural failure from a multi-scale perspective.The main works are as follows.(1)Two dynamic analysis schemes of deck pavement system considering vehicle-bridge interaction and viscoelastic properties of asphalt mixtures were proposed: direct coupling(DC)method and separation reconstruction(SR)method.Based on the Euler-Bernoulli theory,the viscoelastic properties of materials are characterized by Burgers constitutive relationship.The 1/4 vehicle and viscoelastic double-layer Euler-Bernoulli beam coupling systems were established by the DC and SR methods.The dynamic equations of the coupled system were derived and discretized by Galerkin method.Particularly,the nonlinear terms were cleverly simplified by using the characteristics of trigonometric function and transformation relationship of calculus,which made equations transformed into ordinary differential equations.Finally,the dynamic response of the beam can be captured by solving the equations using the fourth-order Runge Kutta method.The results showed that the two dynamic analysis methods are equivalent in obtaining the dynamic responses of viscoelastic asphalt pavement.The SR method solves the problem that it is difficult to couple the vehicle-bridge interaction and viscoelastic properties of pavement materials in one system model based on the existing finite element technology,and provides a theoretical basis for the subsequent study of the dynamic behavior of viscoelastic pavement under vehicle-bridge interaction.(2)Based on the results of Euler-Bernoulli beam,the SR method was adopted to obtain the dynamic responses of viscoelastic pavement under the actual vehicle-bridge coupling.The coupling system model was firstly established,which consisted of the vehicle model including solid tires,linear elastic pavement and steel-concrete continuous beam FEM models.Park numerical integration was selected to calculate the dynamic responses of pavement and bridge structure,and the FEM model of the coupling system was modified and adjusted through the field dynamic bridge test.The dynamic coupling suspension force was then obtained and applied to the nonlinear tire-viscoelastic deck pavement-bridge coupling system model to capture the dynamic behavior of viscoelastic pavement.Moreover,the dynamic response of deck pavement under special conditions such as curved bridge driving and multivehicle eccentric load was also investigated.(3)Using the multiscale calculation method,a section of pavement was taken out at the most unfavorable position of macro mechanical analysis,and its mesostructure model was established to study the rutting evolution mechanism of pavement under the actual vehicle-bridge coupling.Considering the irregular shapes and random distribution characteristics of aggregates,the connection of aggregate-aggregate,aggregate-mastic and mastic-mastic adopted linear model,improved Burgers model and Burgers model respectively to characterize the linear elasticity of aggregates and the viscoelastic properties of mastic.The transformation relationship of macroparameters and mesoparameters of the three models was deduced using kinematics and force balance theory.The mesoparameters of Burgers model were finally determined through indoor mastic creep test.The numerical model was verified by the rutting test and used to capture the movements of aggregates and the changes of contact forces between particles in the rutting process.The cross-scale damage evolution process was revealed from the change of mesomaterial to the permanent macrodeformation.(4)Based on the discrete element method of Newton’s second law,the mesostructure of multiphase asphalt mixture was characterized,and its crack evolution mechanism was explored from the perspective of mesomechanics.The parallel bonding model was adopted to characterize the bonded properties of asphalt mixture.The shapes and spatial positions of aggregates were obtained based on high-definition camera technology and image processing technology.The mesomodel of bending specimen was established to conduct the three-point bending virtual test,and the failure mechanism from the appearance of microcracks,the gradual increase of the numbers of micro cracks to the final expansion into macrocracks was studied.It is found that the macrocrack originates at the bottom of the specimen and evolves to the loading center,mainly along the interior of the mastic and the mastic-aggregate interface.The research conclusions of this thesis may provide some theoretical guidance for deeply understanding the damage evolution mechanism of pavement and improving the dynamic analysis and design level of pavement.They also could offer a certain basis for more accurate evaluation of the fatigue performances of pavement and reducing its early failure.