DAMAGE MODEL FOR COMPRESSION FATIGUE LOADING OF CONCRETE WITH UNIAXIAL LATERAL CONFINEMENT

An anisotropic damage model for concrete subjected to compression fatigue loading with constant lateral confinement is developed based on continuum damage mechanics with the concept of bounding surface. The equations of loading and bounding surfaces are described in terms with strain-energy release rate. The position of the loading surface in the energy release space between the initial and the bounding surface presents 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 of the first author of the paper. Comparison of fatigue life indicates good agreement between the theoretical and the experimental results.