Calibration of KCC concrete model for UHPC against low-velocity impact

As an innovative material, UHPC (ultra-high performance concrete) is regarded as a promising material to improve dynamic resistant performance of civil engineering structures suffered from extreme loadings such as blast, shock and impact loading. The mechanical properties of UHPC members suffered from static/dynamic loading have been systematically investigated through many physical experiments. However, the rationality of the constitutive model utilized in numerical simulations (especially the finite element simulations) to precisely describe behaviors of UHPC has been little emphasized. The objective of this study, therefore, is to calibrate the KCC (Karagozian & Case Concrete) model to effectively predict behaviors of UHPC suffered from low-velocity impact loading. At the beginning, the properties of UHPC under triaxial compression were experimentally investigated by a series of triaxial compression tests to obtain the parameters of three strength surfaces by experimental data fitting. Meanwhile, EoS (equation of state) was derived by the combination of hydro-static compression test, p-alpha equation and Mie-Grueneisen equation of state. Moreover, suitable damage parameters were given by repeated trials, and the suitable model of strain-rate effect for UHPC was also suggested. The single element analysis results indicate that the calibrated KCC model can reasonably reflect the behaviors of UHPC under the uniaxial and triaxial stress state. Eventually, numerical results of low-velocity impact tests of UHPC columns and beams based on the calibrated KCC model agree very well with the tests results, which indicates the rationality of the calibrated KCC model for numerical simulations on low-velocity impact.