Damage Evolution of Concrete under Triaxial Proportional Loading

According to the damage theory by Najar,the damage model of concrete under uniaxial compression is applied to triaxial compressive state to analysis damage evolution of concrete under various triaxial loading pattern.Based on the Simpson integral method,the damage curve of concrete in the main stress direction under triaxial proportional loading is calculated by the damage model.The damage evolution rule of concrete under triaxial and uniaxial compression shows the similar tendency.With the increase in the strain of the loading history,the incremental speed of damage becomes less and less,and finally the damage approaches a stable extreme value.Experienced the same axial strain loading history,the damage value of concrete is lower than that of under uniaxial compression,and the damage of concrete in axial direction is reduced gradually with the increase in lateral pressures,which means that the lateral pressure can reduce the damage effectively.In addition,under triaxial equi-compression loading history,the damage of concrete is found to be in linear dependence relationship with the increase of axial strain,which means that kind of loading pattern can develop the compressive feature of concrete adequately.