Numerical analysis of lateral inertial confinement effects on impact test of concrete compressive material properties

Abstract

Dynamic material properties, in particular the dynamic strength, of concrete material are usually obtained by conducting laboratory tests such as drop-weight test and Split Hopkinson Pressure Bar (SHPB) test. It is commonly agreed that a few parameters associated with stress wave propagation will affect the test results, including the lateral and axial inertial effect, end friction confinement and stress wave reflection and refraction. Many different measures have been proposed to eliminate or limit the influences of these effects in dynamic tests of material properties. However, owing to the nature of dynamic loadings, especially those with high loading rates, it is very unlikely to completely eliminate these influences in physical testing. Moreover, it is also very difficult to quantify these influences from the laboratory testing data. In the present study, a refined mesoscale concrete material model is developed to simulate impact tests and to study the influences of lateral inertial confinement on concrete compressive strength increment at high strain rate. The commercial software AUTODYN is used to perform the numerical simulations. Numerical simulations of concrete specimens of different dimensions and under impact loads of different loading rates are carried out. The results are compared with those obtained from laboratory tests, with those specified in the code and simulated with homogeneous concrete material model. The reliability of the numerical simulation of impact tests is verified. It is found that the influences of lateral inertial confinement effect on Dynamic Increase Factor (DIF) is strain rate and specimen size dependent. Neglecting aggregates in concrete specimen in laboratory tests and numerical simulations lead to underestimation of DIF of concrete material.