RESEARCH ON CONCRETE FAILURE PROCESS UNDER UNIAXIAL TENSION BASED ON STOCHASTIC DAMAGE MODEL

A one-dimensional stochastic mesomechanical damage model is adopted to study the failure process of concrete specimen subjected to uniaxial tension. A balance is taken into account between the dissipated energy in damage evolution and the released elastic strain energy of the specimen during the loading process. The stability analysis of the failure process is conducted;and a stability criterion of the failure process for uniaxial tension test of concrete is derived based on energy principle. The critical state is defined according to the criterion,which is a transition from uniform damage to local damage;and the state is different from the peak stress state and lags behind it. The instable failure process of concrete specimen is accompanied by stress significantly decreased and it indicates that the specimen will fail in a brittle manner,while the stable failure process shows more ductility. Theoretical analysis indicates that the stress-strain curve shape,which includes a sudden decline in stress,is not only affected by the material heterogeneity but also by the length of the test specimens. To describe the heterogeneity,it is regarded that the material failure strain is given by a homogeneous,lognormal or Weibull random distribution. Finally,the failure processes of several concrete specimens under uniaxial tension are simulated with different lengths.