Research On Dynamics Of Pavement Structure Due To Vehicle And Pavement Interaction

With the continuous development of national economy and highway transportation industry, the high speed and heavy duty phenomenon has become extraordinary common. The early pavement damage caused by dynamic load of heavy duty vehicle is becoming more and more serious and receives widespread attention. The static method to design highway has found difficult to meet the demand. It is a prevailing subject to study the dynamics of pavement structure, reveal the pavement damage mechanism, and promote the changing of pavement design criterion from static to dynamic. Although many studies have recently been conducted to find the dynamic responses of the pavement to moving load, most of them have used moving load of constant and harmonic amplitude, and have not considered the stochastic variations in load amplitude with time.Pavement damage makes vehicle's vibration increase, which can seriously reduce the vehicle's driving safety and riding comfort. As a result, vehicle dynamic load increase greatly. Vehicle and pavement are interacted and coupled. When analyzing the dynamic responses of the pavement, the interaction between vehicle and pavement must be considered. In this dissertation, the vehicle model, pavement model and subgrade model are linked to a vehicle-pavement-subgrade interaction system by the vehicle dynamic load. Based on this interaction system, the dynamic responses of the pavement under moving stochastic load are systemically researched by employing the methods of theoretical analysis and simulation. The effects of vehicle and pavement parameters on the dynamic responses and the fatigue failure of the pavement structure are discussed in detail. The main contents include:(1)A whole-vehicle model with eight degrees of freedom subjected to pavement surface roughness is built to simulate the vehicle dynamic load in frequency domains. The effects of vehicle parameters, vehicle moving speed and pavement surface roughness on the power spectral density (PSD) of the dynamic load are investigated. A two-objective optimum concept to design vehicle suspension with the recognition of ride performance and road friendliness as the objective functions is presented and illustrated. The results show that the dynamic load generated by the heavy duty vehicle is primarily distributed in the low frequency region, and decreasing suspension stiffness and increasing suspension damping can not only improve the ride performance but also reduce the pavement damage.(2) An infinite two-layer plate resting on Kelvin foundation and elastic half-space is put forward to model the subgrade and pavement structure. The Fourier transform is used to derive the Green's function of the pavement under the unit impulse load. Based on the superposition principle of linear system, the analytical solutions of the dynamic responses are then derived using the generalized Duhamel integral. The vibration characteristics of the pavement under moving constant and harmonic load are analyzed through some examples, and the regularities of vibration propagation in subgrade and pavement are clarified.(3) A vehicle-pavement-subgrade interaction system is established by linking the vehicle model and the infinite two-layer thin plate resting on Kelvin foundation through the vehicle dynamic load. Based on this interaction system, the dynamic responses of the pavement under moving stochastic load are simulated. The effects of the model parameters on the dynamic responses of the pavement are discussed in detail. Some helpful conclusions and suggestions about vehicle and pavement design are given. A full systematic method as this to study the dynamics of the pavement structure is made.(4) A multilayered viscoelastic system is established by modelling the asphalt surface as viscoelastic constitutive relation. By means of integral transforms and transfer matrix, the Green's function of the multilayered viscoelastic system under the unit impulse load is obtained. The analytical solution of the steady-state displacement is then derived by combining the generalized Duhamel integral with the Green's function. The spline interpolation numerical algorithm is successfully used to calculate the multiple integral of singular and oscillatory function, and transfers the solution from the integral transform domain to the time-space domain. The vibration characteristics of the multilayered viscoelastic system under moving constant and harmonic load are analyzed through some examples. Viscoelastic material can reflect the delaying of the pavement deformation, which is in good agreement with the situation of pavement material and mechanics.(5) Based on the layered theory, a 3-D viscoelastic ANSYS model of the pavement structure is established by modelling the asphalt surface as viscoelastic constitutive relation. The time-dependent deflection, stress and strain of the pavement are obtained by linking together the pavement surface roughness, a moving heavy duty vehicle, and a multilayered pavement structure. The fatigue life of pavement structure is calculated by taking the tensile strain at the bottom of asphalt surface as the evaluation index. A parametric study then follows to show the effects of road grade, loading capacity, vehicle moving speed and vehicle parameters on the fatigue life of the pavement. The fatigue-induced failure regularity and mechanism of the pavement under moving stochastic load is elucidated.