Dynamic size effect of concrete under tension: A numerical study

The macro nonlinearity and size effect of concrete are essentially attributed to the internal heterogeneity of concrete. Considering the heterogeneities and the strain rate effect of meso-components, the concrete was modelled as a three-phase composite composed of aggregate particles, mortar matrix and the interfacial transition zones (ITZs). Taking double-edge notched concrete specimens as examples, a meso-scale numerical model for the simulation of the failure and size effect of concrete under dynamic tensile loading with different strain rates from 10(-5)/s to 100/s was established. The effect of structural sizes on the dynamic tensile strength of concrete was explored. The numerical results indicate that dynamic size effect on tensile strength of concrete has an obvious discrepancy with the static one. There exists a critical strain rate ((epsilon) over dot(cr) = 1/s), and at the strain rate the dynamic tensile strength turns to be independent on the structural size of the specimen. For the case less than the critical strain rate, the tensile strength decreases with increasing the specimen size, and the size effect on the dynamic tensile strength is weakened or suppressed as the strain rate increases. For the strain rate larger than the critical one, there is no obvious difference in the dynamic tensile strength of the concrete specimen having different structural sizes, and the corresponding size effect completely disappears. According to the influencing mechanism of strain rate effect and size effect, a Static and Dynamic unified Size Effect Law (i.e. SD-SEL) for tensile strength of concrete was built. The proposed SD-SEL was also verified by the mesoscopic numerical simulation results.