Application of matter-element analysis based on entropy right to evaluate the pavement condition in permafrost region

Evaluation of pavement performance is one of the most important issues in a pavement-management system.By employing the concept of entropy,the matter-element model for evaluating pavement is established,and the weights of the evaluation indices are obtained from sur-veying data.By calculating the degree of dependence of the matter-element model,the pavement performance evaluation can be obtained by this method.The results show that the matter-element model based on entropy right has good performance for evaluating the pavement condition in permafrost region.

Effect of anisotropic characteristics on the mechanical behavior of asphalt concrete overlay

Asphalt concrete (AC)overlays placed over old asphalt pavement have become an alternative to repairing and reinforcing pavements.The strength contributed by the AC overlay is strongly influenced by the anisotropic properties of the pavement material.This study was conducted to analyze the influence of anisotropy,modulus gradient properties,and the condition of the AC overlay and old pavement contact plane on the mechanical behaviors of AC overlays,as well as to quantify the influence of the degree of anisotropy on the mechanical behaviors of AC overlay by a sensitivity analysis (SA).The mechanical behaviors of the AC overlay were numerically obtained using the three- dimensional finite element method with the aid of ABAQUS,a commercial program.Variations in the AC overlay's modulus as a function of temperature as well as the contact state between the AC overlay and AC layer were considered. The SA is based on standardized regression coefficients method.Comparing the mechanical behavior in terms of surface deflection,stress,and strain of the anisotropy model against those corresponding to the isotropic model under static loads show that the anisotropic properties had greater effects on the mechanical behavior of the AC overlay.In addition,the maximum shear stress in the AC overlay was the most significant output parameter affected by the degree of anisotropy. Therefore,future research concerning the reinforcement and repair of pavements should consider the anisotropic properties of the pavement materials.

Assessing artificial neural network performance for predicting interlayer conditions and layer modulus of multi-layered flexible pavement

The objective of this study is to evaluate the performance of the artificial neural network(ANN)approach for predicting interlayer conditions and layer modulus of a multi-layered flexible pavement structure.To achieve this goal,two ANN based back-calculation models were proposed to predict the interlayer conditions and layer modulus of the pavement structure.The corresponding database built with ANSYS based finite element method computations for four types of a structure subjected to flling weight deflectometer load.In addition,two proposed ANN models were verifed by comparing the results of ANN models with the results of PADAL and double multiple regression models.The measured pavement deflection basin data was used for the verifications.The comparing results concluded that there are no significant differences between the results estimated by ANN and double multiple regression models.PADAL modeling results were not accurate due to the inability to reflect the real pavement structure because pavement structure was not completely continuous.The prediction and verification results concluded that the proposed back-calculation model developed with ANN could be used to accurately predict layer modulus and interlayer conditions.In addition,the back-calculation model avoided the back-calculation errors by considering the interlayer condition,which was barely considered by former models reported in the published studies.

Anisotropy of multi-layered structure with sliding and bonded interlayer conditions

A better understanding of the mechanical behavior of the multilayered structure under extermal loading is the most important item for the structural design and the risk asssment.The objective of this study are to propose and develop an analytical solution for the mechanical behaviors of multi-layered structure generated by axisy mmetric loading,and to investigate the impact of anisotropic layers and interlayer conditions on the multi-layered structure.To reach these objectives,first,according to the goveming equations,the analytical solution for a single layer was formulated by adopting the spatial Hankel transform.Then the global matrix technique is applied to achieve the analytical solution of multi-layered structure in Hankel domain.The sliding and bonded interlayer conditions were considered in this process.Finally,the numerical inversion of integral transform was used to solve the components of displacement and stress in real domain.Gauss-Lcgendre quadrature is a key scheme in the numerical inversion process.Moreover,following by the verification of the proposed analytical solution,one typical three-layered flexible pavement was applied as the computing carrier of numerical analysis for the multi-layered structure.The results have shown that the anisotropic layers and the interlayer conditions significantly affect the mechanical behaviors of the proposed structure.