Research On Fluctuation Of Running Vehicle Load And Impact On Asphalt Pavement Structure Design

It has become a common phenomenon that expressway asphalt pavement with design life of 15 years often early damaged in two or three years after opening to traffic. Problem occurs because vehicles will produce random vibration affected by road excitation when running on rough pavement. This leads to the stress increase and roughness decrease of the pavement. Furthermore, the deterioration of pavement roughness will aggravate vehicle vibration once again, and make the road subject to greater force. This kind of relationship between running vehicle load and pavement roughness greatly accelerate the damage of pavement. But existing asphalt pavement structure design mainly considered axle load as static load. The space repeatability and fluctuation of actual vehicle load are not under consideration. Bec ause of these issues, the designed pavement often cannot meet the requirement of design life.In this paper, filtered white noise method is used to simulate the pave ment elevation under different power spectral density. With the consideration of road surface shape effect, the relationship between pavement power spectral density and international roughness index is built. After validated, the simulated pavement elevation is correct and effective.Then the simulated pavement elevation is used as the import of biaxial semi-truck model with the consideration of loading effect. Suitable length and amount of the simulated pavement is selected to calculate the running vehicle loads of each point of pavement under different roughness, speed of vehicle and axle load. Finally, biaxial semi-truck systems modes and amplitude-frequency characteristics of running vehicle load are comparatively analyzed.By the analysis of regularity of vehicle load fluctuation under different roughness, speed of vehicle and axle load, it can be concluded that running vehicle load have a spatial repeatability in the same location of pavement when vehicles traveling on the same road with different speed and axle load. The standard deviation of running vehicle is selected as the representative value to obtain the regularity and sensitivity of each influential factors of running vehicle load.Combined with examples, the influence of running vehicle load to structure design of asphalt pavement is analyzed, including the impacts to pavement servic e life, design deflection value, layer bottom tensile stress of each layer and the roughness maintenance criteria of asphalt pavement.