Dynamic strength criterion of concrete utilizing dynamic coordinates

The effects of strain rate on the strength of concrete should be considered when analyzing the dynamic responses of concrete structures subjected to earthquakes or explosions. This paper shows that the effect of strain rate on strength characteristics can be attributed to an increase in cohesion. Notably, the effects of friction, hydrostatic pressure, and intermediate principal stress tend to remain rate-independent under the appropriate reference system. Consequently, a dynamic coordinate system is established to account for the effects of strain rate on isotropic tensile strength. In this dynamic coordinate system, the strength envelopes for concrete closely resemble those in quasi-static conditions under varying strain rates, as defined in the unified strength criterion. Using this proposed dynamic strength criterion, this paper explores the dynamic characteristics of different stress paths, including uniaxial, biaxial, and triaxial compression and tension. The predictions, both in terms of tendencies and magnitudes, are consistent with test results. The proposed method enables the extension of most strength criteria to dynamic scenarios by introducing two additional parameters with clear physical interpretations. This advancement enhances the current understanding of dynamic strength characteristics and provides a theoretical foundation for dynamic response analysis.