Research on dynamic constitutive model of ultra-high performance fiber-reinforced concrete

A dynamic constitutive model for ultra-high performance fiber-reinforced concrete (UHPFRC) was investigated in this paper. In view of the particularity of UHPFRC material, two improvements including the modifications of yield surface and the change of strain rate effect due to the adjunction of steel fibers were made based on the Holmquist-Johnson-Cook model (HJC model). Further, on the purpose of model parameter determination, a series of mechanical tests for UHPFRC material, including uniaxial compression test, bending test, uniaxial cyclic compression test and SHPB test were carried out. And the 22 calculation parameters required in the improved HJC model such as strength parameters, damage parameters and pressure parameters were obtained through data analysis and fitting. Finally, the numerical simulation of the SHPB test performed in this study and the drop hammer impact test in the literature were carried out in order to verify the rationality and practicability of the improved HJC model. The numerical simulation results of SHPB test show that the failure morphology and stress-strain curves of UHPFRC specimens are in good agreement with the test results. When the improved HJC model and the appropriate corrosion strain value (1.0% in this work) were selected, the mid-span deflection-time curve obtained by numerical simulation is consistent with the result of the drop hammer impact test.