Abstract: In an attempt to explore the relationship between dynamic response of concrete and waveform of reflected waves during Split Hopkinson Pressure Bar (SHPB) tests under confining pressure, we simulated the SHPB tests under active confining pressure using LS-DYNA based on the Johnson-Holmquist Concrete constitutive model. We also analyzed the influence of confining pressure on dynamic properties of concrete in terms of changes in waveform characteristics. Results show that the failure mode of concrete under confining pressure is compression-shear failure, and the average degree of damage decreases with the climbing of confining pressure. The reflected wave in SHPB test is featured with double peaks, of which the first peak stress is barely affected by confining pressure, but by the magnitude of impact wave; while the second peak stress is significantly affected by confining pressure, declining with the increase of confining pressure, which implies the deformation degree of specimens. Compressive wave was found in the end of the reflected wave; with the increase of confining pressure, peak stress of the compressive wave increased as well, indicating an enhancement in deformation capacity and residual bearing capacity of the concrete specimen. The research achievements could serve as a reference for evaluating the dynamic damage and residual bearing capacity of concretes under triaxial stress.

Key words: concrete, SHPB tests, active confining pressure, degree of damage, double-peak characteristic, compressive wave