| The life and service function of asphalt pavement is related to the ambient temperature in addition to the traffic load.The influence of temperature on the performance of asphalt pavements is mainly reflected in two aspects,one of which is that asphalt mixtures are typical viscoelastic materials,and their stiffness is significantly dependent on temperature.On the other hand,the warming-cooling effect will produce temperature stress(strain)in the pavement structure,when the temperature stress exceeds the allowable strength of the material,it will cause pavement cracking,even if the temperature stress is less than the allowable strength of the material,although it does not cause pavement cracking,but in the long term under the cyclic action of the temperature stress(strain),it will cause fatigue damage to the pavement structure.For the above problems,the finite element numerical analysis method(FEM)was used to analyze the temperature field and modulus field distribution characteristics of asphalt pavement,and based on the temperature field and modulus field,the thermomechanical response characteristics and temperature fatigue damage of asphalt pavement structure were investigated.The main research work and results are as follows:Firstly,the spatial and temporal distribution characteristics of air temperature and solar radiation in 34 provincial capital cities in China were analyzed,and the ranges of changes in air temperature and solar radiation in different regions of the country were obtained;The cumulative frequency distributions of daily maximum air temperature,daily air temperature temperature difference and total daily solar radiation all conform to the Weibull distribution in the Generalized extreme value(GEV)model;The distribution maps of daily maximum air temperature,daily air temperature temperature difference and total daily solar radiation across the country were constructed with 95% probability quantile thresholds.Secondly,the influence of meteorological characteristic parameters on the FEM analysis results of pavement temperature was demonstrated by numerical analysis method,and the recommended values of meteorological characteristic parameters were given;The distribution characteristics of pavement structure temperature and temperature difference with time and depth under different air temperature conditions were analyzed;According to different daily temperature extremes and total daily solar radiation,the asphalt pavement temperature prediction model and daily temperature difference extreme prediction model,which do not depend on geographical differences,are constructed,and the reliability of the prediction model is verified;The temporal and spatial distribution patterns of road surface temperature were analyzed using the temperature prediction model and the daily temperature extreme prediction model,and the cumulative frequency distributions of the mean daily road surface temperature and the daily road surface temperature difference conformed to the Weibull distribution in the GEV distribution,and the distribution maps of the national mean road surface temperature and the daily road surface temperature difference were constructed with the 95% probability quantile threshold.Thirdly,according to the temperature and frequency of traffic loads at different depths of asphalt layer of asphalt pavement,an iterative calculation program of dynamic modulus of asphalt layer was written to calculate the dynamic modulus at different depths of asphalt layer at different moments,which revealed the distribution law of dynamic modulus of asphalt layer with time and depth;The effects of temperature,vehicle speed,asphalt layer thickness and asphalt mixture type on the dynamic modulus of asphalt layer were analyzed;The dynamic modulus prediction model of asphalt layer considering temperature and depth is established,and the correction of the regression parameters of the dynamic modulus prediction model when the vehicle speed,asphalt layer thickness and asphalt mixture type are different is discussed;The temporal and spatial distribution characteristics of the dynamic modulus of asphalt layer in 34 provincial capital cities in China were analyzed by using the dynamic modulus prediction model,and the distribution map of the annual average of the dynamic modulus in China was constructed.Then,based on the temperature and modulus fields of asphalt pavements under different air temperature conditions,combined with the stress relaxation characteristics of asphalt concrete,the FEM method was used to analyze the characteristics of the temperature stress(strain)generated within the asphalt pavement structure with time and depth under the effect of warming-cooling;The effects of different temperature conditions and wide stiffness domain base structures on the temperature stress(strain)response are discussed;The conditions under which the temperature stresses arise after considering the stress relaxation effect of asphalt mixtures are clarified;The prediction models of temperature strain extremes and temperature stress extremes were established;The temporal and spatial distribution characteristics of temperature strain extremes and temperature stress extremes in 34 provincial capital cities in China were analyzed by using the prognostic model.The cumulative frequency distribution of temperature strain extremes conformed to the Weibull distribution in the GEV model,and the cumulative frequency distribution of temperature stress extremes conformed to the Gamma distribution,and the distribution maps of temperature strain extremes and temperature stress extremes for the whole country were constructed with 95% probability quantile thresholds.Finally,according to the dynamic modulus of asphalt layer and temperature strain extreme value,combined with the fatigue life estimation model and fatigue damage accumulation criterion,the temperature fatigue damage calculation method was initially proposed,and the temperature fatigue damage calculation software was developed;Taking one day and one night and one year as the calculation cycle,the daily temperature fatigue damage and annual temperature fatigue damage of asphalt pavements in 34 provincial capital cities in China generated under the effect of warming-cooling during the calculation cycle were calculated,and the accumulation rules of daily temperature fatigue damage and annual temperature fatigue damage in one year were analyzed;The distribution map of cumulative temperature fatigue damage in China was constructed.Using the temperature prediction model and dynamic modulus prediction model,the temperature and dynamic modulus of asphalt pavement at different depths in any moment in any region can be found,and then the temperature stress and temperature strain as well as temperature fatigue damage generated by the cyclic change of warming-cooling can be found.The research results contribute to the further improvement and development of asphalt pavement structural analysis theory,laying a theoretical foundation for the construction of long-life asphalt pavement. |
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