Modeling strain rate effect on tensile strength of concrete using damage plasticity model

Experimental researches show that the strength of material increases with strain rate. However, dynamic response of quasi-brittle materials is significantly different under tensile and compressive loading. In order to simulate this phenomenon, damage plasticity model is adopted and enhanced with strain rate effect. Two different state variables as equivalent strain rates are defined, one for compression and other one for tension. Corrected strain rates are used instead of instantaneous ones, in order to consider retardation of damage evolution. Simulations of Split Hopkinson pressure bar (SHPB) are conducted to investigate dynamic tensile strength of concrete specimens. Performance of the proposed model is demonstrated by comparing with experimental results. Furthermore, a parametric study is conducted and effects of different parameters, such as dilatation angle, friction, thickness of the specimen, shape of impulse and impedance mismatch, on the dynamic increase factor are discussed in detail.