Study On The Interaction Of Vehicle Random Loads And Flexible Pavement

Due to the dynamic load,there is a more and more discrepancy between the mode of static load and the fact force on pavement of the running vehicle.Dynamic characteristic of pavement can not nearly be described by statics.It is impossible to resolve radically those defaults and discrepancies with the existing design theory and means.The dissertation targets on some heated and difficult issues(research on vehicle random loads and dynamic response of flexible pavement by experiment)and researches on vehicle dynamic load and pavement structure response.By regarding vehicle and road surface as synthesized system,deeper theoretic analysis and experimental research were made.1.To aim directly at pavement irregularity as a excitation for random vibration of vehicle,the input spectra matrix of pavement was deduced by analytical method of frequency domain,and these characteristics and rules of PSD of highway pavement's irregularity were analyzed.Above these, various vibration models of vehicles were analyzed and evaluated.And then,through two degree of freedom and unidirectional vibration models of vehicles,vehicles random vibration was calculated by numerical method.These factors including Vehicle load,running speed,pavement irregularity,rigidity of wheel weight-bearing system,damping and so on that have influences on magnitude and distribution of dynamic wheel loading were analyzed.2.The Analytical Hierarchy Process(AHP)was used to assess the random dynamic loads of vehicle based on the specified hierarchical index system,according to the main factors which affects the random loads.With application of AHP method complex random loads of vehicle are disintegrated into several parts,and then quantitative evaluation is made for random loads.Based on the analytic results, classification criterion of random loads is established which can provide foundation for logical loads model.3.Field experiments were conducted on the ChangDe-ZhangJiajie freeway of vehicle random dynamic load.The time history curves of acceleration of vertical vibration at axis were gained by piezoelectric sensor.Based on it,the root mean square values of acceleration of vertical vibration were obtained and through the rms value,the normal loads of wheels were get.The characteristics of vehicle random vibration at various running speed and loading were researched and analyzed.Auto-power spectrum and mutual power spectrum of vehicle random vibration were analyzed,and then the spectra of the vibration at various running speed and loading were investigated.4.Based on physical mechanic properties of flexible pavement and with reference to pertinent files,transfer function matrix was adopted via theory of layered system after transformation through Fourier and Laplace integration;it predicts solution of dynamic equation of multiple viscoelastic system under moving harmonic loads.Due to the difficulties of analyzing viscoelastic,FEM numerical method applied in ANSYS was proposed as the way to analyze multiple-layered dynamic response.5.According to proposition of multiple-layered viscoelastic system of flexible roadbed and surface,3-D dynamic FEM model of flexible roadbed and surface was established by ANSYS.Based on it,dynamic responses of flexible pavement structure under dynamic load of vehicle were analyzed,influences on pavement structure as a result of vehicle speed and load were researched,and then destroy mechanism of the brake power of vehicles to pavement were investigated.Finally,numerical modeling results were compared with experimental values,which show that experimental value conforms to numerical solutions.Therefore,the viscoelastic 3D Finite model established in the dissertation is valid.6.Field experiments were carried out on the ChangDe-ZhangJiajie freeway of pavement dynamic displacement of flexible pavement under heavy vehicle loads.The traits of pavement dynamic displacement were investigated at various running speed and loading. Vehicle excitation and pavement response regarded as synthesized system were investigated.The features of vibration spectra of pavement were analyzed.7.Field experiments were conducted on the ChangDe-ZhangJiajie freeway of dynamic response of each structural layer of flexible roadbed and surface under heavy-load vehicle.With consideration to impact of vehicle load,speed and freeway lane on the dynamic response regularity of roadbed and surface,analyzed were portrait varying characteristics of vibration frequency.