Study On Cement Concrete Pavement Structural Reliability Based On Random Field Theory

In China, the cement concrete pavement is a very important pavement structure. Ithas a very wide application both in the high-grade highway and the low-grade highway.The reliability is a very important quality indicator of the pavement structure. It is alsoan important content of cement pavement structure research. The structure size, materialproperty and load are uncertainty. How to describe the random factors more accurately,choosing a suitable reliability calculation method and analysis the reliability which isaffected by random factors is the main content in this paper.First, this paper analyzes the random factors which affect the reliability of the cementconcrete pavement structure. There are mainly cumulative axle load, axial load,flexural-tensile strength of cement concrete, temperature gradient, material modulus andcement concrete slab thickness. According to the characteristics of the above factors, themodulus of surface course, subbase course and subgrade is regarded as two-dimensionrandom field. The other random factors are regarded as random variable. Accordingto local averaging technique, the modulus random field is dispersed as random variable.The covariance matrix and correlation coefficient matrix is calculated.Second, based on Ansys, the finite element model of cement concrete pavementstructure is built and the correctness of the model is verified. The above randomvariables are regarded as the input variables. Distribution form is truncated gaussiandistribution. According to the monte carlo method which is provided by Ansys/PDS, thefailure probability of pavement structure under the limit states condition of fatiguecriteria and limit criteria is calculated. Random factors which have a larger influence onstructure reliability are analyzed. They are concrete slab thickness, axle load, flexuralstrength of concrete and the concrete modulus. The difference of failure probabilitybetween modulus random field model and modulus random variables model is analyzed.The result shows that the failure probability of modulus random variable model isgreater than modulus random field model.Finally, the failure probability which is influenced by axial load, surface coursemodulus, slab thickness, contact conditions between surface course and base course andsynthetic action of temperature load and vehicle load is analyzed. The result shows thatthe mean concrete slab thickness, the mean surface modulus and axle load have a greatinfluence on the reliability of the structure. Compared to the mean, the variablecoefficient of slab thickness and surface modulus have less influence on the structuralreliability. The relation curve of the structure failure probability and the frictioncoefficient between surface course and subbase course has a critical point. Controlling the friction coefficient greater than the point is very beneficial for improving thestructural reliability. The combined action with the temperature gradient and axial loadhas a great influence on structural reliability. The failure probability of positivetemperature gradient is greater than not considering the combined action temperaturegradient and axial load. The failure probability of negative temperature gradient is verysmall.