Determination and evaluation of Holmquist-Johnson-Cook constitutive model parameters for ultra-high-performance concrete with steel fibers

Ultra-high performance concrete (UHPC) features with exceedingly high strength and fracture energy, and thus is regarded as a promising structural material to resist impact and blast loadings. Particularly, adding steel fibers can significantly enhance the impact resistance of UHPC. To facilitate the simulation of the behavior of UHPC structures with various steel fiber ratios against extreme loadings, selecting an appropriate constitutive model and determining its parameters should be highly emphasized. The Holmquist-Johnson-Cook (HJC) model is widely used in the simulation of the conventional concrete subjected to impact and explosion, whereas there are rare studies on calibrating the parameters of the HJC model for UHPC. In this study, a set of HJC model parameters for UHPC with considering the volume ratio of steel fiber ranging from 0% to 3% were firstly determined based on existing test data, originating from the Split-Hopkinson pressure bar (SHPB) test, triaxial test, uniaxial loading test, and Hugoniot test. To verify the correctness of the calibrated parameters of HJC model, UHPC slabs under the contact explosion condition were then tested, and a finite element model (FEM) with the calibrated parameters implemented was thereby established to reproduce this experiment numerically. Finally, the existing bullet penetration experiment was also verified with the numerical procedure. The results show that finite element simulations by employing the HJC model with calibrated parameters agree well with the experiments. The successful applications and evaluation of the HJC model with calibrated parameters in this work can provide guidance in simulating the behavior of UHPC with certain prescribed steel fiber ratio subjected to the impact and blast loading.