Rate-dependent Endochronic Damage Constitutive Model For Concrete

Concrete is a type of rate-dependent material. There are distinct differences between low strain rate situation and high strain rate situation about the strength and stiffness of concrete. And structures are subjected to dynamic loads unavoidably, like seismic load, wind load, blast load and so on.In order to describe the strength and deformation characteristics of concrete under impact loads, an endochronic damage constitutive model with the effect of strain rate taken into account is proposed. In this model, the elasto-plasticity of concrete is described by endochronic theory, so that the concept of the yield surface is not needed. And the behavior of stiffness degeneration due to microcrack propagation is described by damage theory. Based on the dynamic experiments, incremental evolvement law of damage is introduced. The comparison of numerical and experimental results shows that the model can well represent the uniaxial and biaxial dynamic behavior of concrete.Finally, the proposed model is used to analyze a reinforced concrete frame structure. The analyzing result shows that the strain rate dependence of the material can have a great effect on the strength and stiffness of concrete structures subjected to seismic load. And the effect is greater when structures are under severe earthquake than under normal earthquake.