Strain-rate-sensitive constitutive law for concrete

Concrete strength is highly sensitive to loading procedure, especially in the range of high strain rates. On the basis of experimental results, it is demonstrated that the full loading history must be included in a dynamic constitutive model, not just consideration of the current strain rate. The rate effect is mainly attributed to internal inertia forces during microdamage evolution. A strain history-dependent constitutive model is proposed based on this retarded activation of microdamage. A simplified version allows identification of material parameters for practical application. It is shown how this dynamic approach fits into the general framework of continuum damage mechanics.