A comparison of strain-rate enhancement approaches for concrete material subjected to high strain-rate. Issue 2 (June 2017) - Kong, Xiangzhen
High strain-rate induced from intense dynamic loadings will cause an obvious enhancement of concrete material frequently used in civil and defense engineering, which plays an important role in correct numerical simulations of concrete members subjected to intense dynamic loadings. In this article, the existing three strain-rate enhancement approaches for concrete material are compared by three aspects, that is, flexibility of fitting data, consistency condition, and time-dependent behavior. The so-called "overstress approach" is found to be not flexible for fitting high strain-rate data and unable to well predict the strain-softening behavior but can capture the inherent viscidity of concrete material. The "consistency approach" can describe the strain-softening behavior and the inherent viscidity but may be inconvenient and time-consuming when fitting high strain-rate data. The "simplified approach" widely used in commercial concrete material models can describe the strain-softening behavior and fit high strain-rate data by a more convenient and direct way but cannot capture the inherent viscidity of concrete material. Examples of uniaxial stress including loading and unloading under constant and varying strain-rates are presented to demonstrate the above-mentioned findings, in which the updating algorithm of dynamic stress is presented in detail.