Dynamic mechanical behavior and numerical simulation of concrete under three-dimensional coupled static-dynamic loading

To study the dynamic mechanical behavior of concrete under three-dimensional coupled static-dynamic loading, split Hopkinson pressure bar (SHPB) experiments were carried out under combined axial compression, confining pressure, and impact loading. A stress initialization method was introduced into the LS-DYNA program, and a sequential analysis approach consisting of implicit static loading followed by explicit transient dynamic loading was used to simulate the coupled static-dynamic loading process. The influence of different static load combinations on the strength and failure characteristics of concrete was systematically analyzed. The results show that, at the same impact velocity, the dynamic compressive strength of concrete increases with increasing confining pressure, which provides a protective effect on the specimen. A critical axial compression value is observed: below this threshold, axial compression enhances specimen strength, whereas beyond it, axial compression leads to strength deterioration. The introduction of the stress initialization method enables accurate realization of constant pre-stress conditions before dynamic analysis. Comparative analysis between experimental and numerical results shows that static loading provides limited compaction enhancement, while changes in static load combination significantly alter the internal stress distribution, which is the main factor affecting the dynamic strength of concrete. Numerical simulations effectively capture the failure process of concrete under three-dimensional coupled static-dynamic loading, revealing that the dominant failure mode is compressive-shear failure. Furthermore, the damage evolution of concrete can be reliably predicted by analyzing the time-history curves of damage variables in the numerical model.