Study On The Vehicle-Pavement Interaction Based On The Viscoelastic Property Theory Of Fractional Order Derivative

As the traffic vehicles on the highway become larger and heavier, the static load model can not represent the actual state of pressure on the road surface any more. The static load model is unable to explain various phenomena in the road surface structure under the random dynamic load as well. Therefore, it is essential to study the dynamic interaction mechanism in the vehicle and road surface coupling system. Based on the relevant research results in China and abroad, this dissertation is to study the asphalt road surface and to analyze the dynamic interaction of vehicle-road coupling system by applying the viscoelastic property theory with the fractional order derivative. The following research works have been accomplished and the relevant results achieved.(1)An asphalt mixture testing instrument SPT is used to test the dynamic modulus of three types of asphalt mixtures named AC-13, AC-20 and AC-25. A viscoelastic property model of fractional order derivative for the asphalt mixtures is established based on the viscoelastic property theory of fractional order derivative. The result shows that the three-element model of fractional order derivative can precisely describe the dynamic behavior of viscoelastic asphalt mixtures at a wide range of temperature and frequency. Only a few experiment parameters are required to confirm the model and the fitting parameters obtained have some physical meanings. Generally the derivative orderαof the model is between 0.4 and 0.5.(2)As the dynamic response of viscoelastic structure of fractional order derivative is concerned, a numerical calculating method for the constitutive relation of fractional order derivative is proposed on the basis of precise time integral method. The calculated result coincides with the results by analytic method and Zhang-Shimizu algorithm. The calculating method is of good convergence and the smaller the counting step, the more precise is the result.(3)As for FE format of the three-element-model of fractional order derivative for the asphalt mixture, the three-element-model of fractional order derivative is applied to the FE model. The finite element equation of viscoelastic structure dynamics is derived based on the three-element constitutive relation of fractional order derivative.(4)A two-dimension FEM of road base and road surface is established with the hypothesis of multi-level viscoelastic system of flexible pavement. The geometry and dynamics coupling relations are introduced to the joint of vehicle and road surface. The fractional dynamics equation of vehicle-road surface coupling system is drawn out and then transformed into status equation.(5)A response analysis program for the vehicle and road surface coupling system is developed by applying the numerical algorithm proposed above. The random excitation of class B pavement is used to calculate the dynamic response of the vehicle, the road base and the road surface. Furthermore, the effects of vehicle load, speed and road roughness on the dynamic viscoelastic response of road are analyzed. Analysis shows that the random dynamic load varies with the speed, the load and the road roughness and the road roughness plays a crucial role. Since the random dynamic load has a great effect on the structure of road base and road surface, it is necessary to limit strictly the overloading and overspeeding on the road, to pay attention to the quality of the pavement and to strengthen the maintenance.