DAMAGE MODEL FOR TENSION-COMPRESSION FATIGUE LOADING OF CONCRETE AND ITS VERIFICATION

A constitutive relationship for predicting the response of concrete subjected to uniaxial tension-compression fatigue loading is established based on the continuum damage mechanics. The tension and compression bounding surfaces are employed in the formulation of the theoretical model. The equations of loading and bounding surfaces are described in strain-energy release rate. The position of the loading surface in the energy release space between the initial and the bounding surface present the various levels of damage states. The varying size of the limit fracture surface for fatigue loading is obtained through establishing the relation between the cumulative damage and the onset of the energy release of the cycle, which simulates the degenerative process of the stiffness of concrete under cyclic loading. The calculation parameters of the model are given according to the fatigue test results acquired by the authors. Comparison of the stress-strain and fatigue life results indicates good agreement between the theoretical model and the experimental data.