The Simulation Of Nonlinear Behavior Of Concrete Under Cyclic Loading

The paper introduced some damage models used in the numerical analyses ofconcrete structures. Based on the damage mechanics, an anisotropic damage model isdeveloped by establishing a damage evolution rule determined by the dissipating energyand fracture energy. The nonlinear unloading/linear reloading stress branches are usedto model the hysteretic behavior of concrete under cyclic loading. Moreover, a yieldingfunction is introduced into the damage model to account for the influence of multi-axialstress state on the concrete strength.Utilizing the software ABAQUS, finite element transplantation of the proposedmodel was achieved thus the theoretical model could be applied to practical projects.Applying FORTRAN statement to build concrete fatigue damage model, the yieldjudgment, unload path description, nonlinear iteration and numerical computation ofstress, strain, Jacobian matrix, etc. were conducted in this model. And through the usersubroutines UMAT, the model was implanted to the large commercial finite elementsoftware ABAQUS and then analytical platform of concrete uniaxial fatigue damageand biaxial compression monotonic and repeating load simulation was established.With the help of simulation analysis platform, we can simulate the mechanicalbehavior of concrete specimens under uniaxial cyclic loading, biaxial proportionalloading, biaxial non-proportional loading and biaxial compression cyclic loading.Comparing simulation results under uniaxial cyclic loading with the test data, thesimulation curve can well demonstrate the mechanical behavior of concrete, such as thestiffness degradation, the residual deformation and the hysteresis energy dissipationunder uniaxial cyclic loading. This model can be applied to nonlinear finite elementanalysis of concrete and can be used to simulate the fatigue properties under uniaxialcompression cyclic loading availably. Under the case of biaxial compression loading, itis a simplified model that mapped directly the damage evolution rule of uniaxial tobiaxial. Simulated results under biaxial proportional/non-proportional loading coincidewell with the test data, and can well demonstrate the increasing of concrete strengthunder biaxial compression loading. Simulated results under biaxial compression cyclicloading can well demonstrate the hysteresis energy dissipation, fatigue failure behaviorand the increasing of concrete under biaxial cyclic loading. The model, in this paper,can simulate the real response of concrete under uniaxial(biaxial) monotonic(cyclic) loading and confirm the reasonability of transplanting the theoretical model to the finiteelement software. A sound simulation platform to apply this theoretical model onconcrete uniaxial and multiaxial fatigue damage analysis was provided.