Rate effect of concrete strength under initial static loading

The dynamic strength enhancement of concrete under different initial static loadings is investigated in this paper. The mechanism of the influence of the inertia effect on the dynamic strength of concrete is discussed first by analyzing a single dimension of freedom system, which shows that the inertia effect only influences the dynamic loading part. The dynamic strength of concrete at initial static loading is calculated assuming a single crack model with consideration of free water viscosity using dynamic fracture mechanics. The dynamic stress intensity factor of the crack under linearly increasing loading on the basis of an initial static loading is achieved. The relationship between the dynamic strength increase factor and the static stress level is obtained. The comparison between the results by the model proposed in this paper and those by experiments in some available references indicates a good agreement.