Mechanical Analysis On Engineered Cementitious Composites Pavement Structure

Engineerd Cementitious Composites (ECC) is a class of fiber reinforced cementitious composites which based on the theory of micromechanical material design.This kind of material shows high bending tensile strength, excellent deformation ability, strain hardening and multi-cracking characteristics. Compared with ordinary cement concrete, the excellent mechanical properties of ECC can effectively reduce the traditional cement concrete pavement distress due to the damage caused by brittle cracking. It is significant to improve the durability and safety of pavement structure.However, the current domestic research on the ECC is mainly focused on the mechanical properties of the material itself. Research involving ECC structure under the external load and environmental effects is relatively less. Therefore, it is necessary to analyze the mechanical properties of ECC pavement structure, to study the structural design method of this new type pavement, and to provide some theoretical reference for further engineering application. In this thesis, the method of finite element analysis is adopted. The mechanical response of ECC pavement structure under the effect of traffic load and temperature gradient including stress and displacement are analysed respectively. The load stress formula and the temperature stress formula of the ECC slab are obtained through regression analysis. At last, ECC pavement structure design method based on the reliability theory is proposed.Firstly, the mechanical response of ECC pavement structure under traffic load is analyzed. On the basis of the constitutive relation of ECC material, the three-dimensional finite element model of pavement structure is established by ABAQUS, in which the influence of joints are considered. Stress, displacement and equivalent plastic strain of ECC pavement structure under traffic load are numerical simulated. The critical load position of ECC pavement structure is ascertained. Then, The effects of different pavement structure parameters on the mechanical response and fatigue performance of ECC pavement are analyzed.Secondly, the mechanical response of ECC pavement structure under temperature gradient is analyzed. On the basis of the constitutive relation of ECC material, the three-dimensional finite element model of pavement structure is established, the effects of different pavement structure parameters on the mechanical response and fatigue performance of ECC pavement under temperature gradient are numerical simulated.Thirdly, the regression formula of load stress and temperature stress of ECC pavement structure is studied. The load stress formula on the basis of orthogonal design method and multivariate statistical regression method of ECC pavement is obtained. The load fatigue stress of ECC pavement is analyzed considering the fatigue performance of ECC material. Moreover, the temperature stress formula is obtained.At last, the structural design method of ECC pavement based on the reliability theory is proposed. On the basis of previous analysis of the load stress calculation method and the temperature stress calculation method and the fatigue stress calculation method proposed in the current specification, structural design method of ECC pavement based on the reliability theory is proposed. By analyzing the specific examples, the outcomes by using specification design method on common cement concrete pavement and the method given in this thesis on ECC pavement are compared. The application of the two methods is studied. Moreover, the length range of the ECC slab is recommended.