Meso-scale modelling of the size effect on dynamic compressive failure of concrete under different strain rates

Abstract

Great progresses have been made in static size effect of concrete, while almost no efforts have been conducted in dynamic size effect of concrete. The macro nonlinearity and size effect of concrete should be attributed to the inner heterogeneities. Herein, a meso-scale simulation method was built to study the dynamic failure and size effect of concrete. In the approach, the concrete heterogeneities were explicitly described, and the strain rate effect for the meso components were also taken into account. Taking squared concrete specimens as examples, the dynamic compressive failure and the size effect of concrete under different strain rates from 10−5/s to 200/s were modelled and investigated. The effect of strain rate on the size effect in compressive strength of concrete was also explored. The simulation results indicate that, there exists a critical strain rate (ɛ˙cr=1/s). When the applied strain rate is less than the critical strain rate, the compressive strength decreases with increasing the specimen size and the size effect on the dynamic compressive strength is weakened as the strain rate increases. The dynamic compressive strength turns to be independent on the structural size of the specimen for the critical strain rate. When the applied strain rate is more than the critical strain rate, the compressive strength increases with the increase of specimen size and the size effect on the dynamic compressive strength is enhanced as the strain rate increases. Finally, based on the influencing mechanism of strain rate effect to dynamic strength and size effect, a Static and Dynamic unified Size Effect Law (i.e. SD-SEL) for compressive strength of concrete was established. The proposed size effect law was also calibrated by the meso-scale simulation results.