Impact response of steel fiber-reinforced concrete using a split Hopkinson pressure bar

The uniaxial compressive response of steel fiber-reinforced concrete (SFRC) subjected to high strain rate loading is presented. Details of an experimental investigation using a 75-mm-diameter split Hopkinson pressure bar (SHPB) are outlined. The investigation focuses on recorded data and results in distinguishing the strain rate that mobilizes ductility of steel fiber reinforced concrete. SFRC specimens with relatively high static compressive strength were tested at strain rates between about 20 and 100 s(-1) produced by impact from two specially designed striker bars on the SHPB facility; different impact load durations were produced using these striker bars. The reason for adopting this strategy is explained. Tests confirmed that the unconfined uniaxial compressive strength of SFRC increases with strain rate in the same way as plain concrete. Further, strain rate has a significant influence on the ductility of SFRC. At a high strain rate, the postpeak ductility is absent. This is in direct contrast to the behavior of the same material subjected to static loading. However, SFRC possesses good postpeak ductility at a strain rate below a specific value dictated by the entire loading process; a recommendation on the strain rate is proposed. A method for conducting approximate constant strain rate testing using the SHPB facility is also described in the paper.