A centrally loaded round panel test was used to characterize the fracture energy of FRC under low velocity impact loading. The specimens, with a diameter of 650 mm and a thickness of 60 mm, were cast using plain high strength concrete (HSC, f'c = ～80 MPa), steel fiber reinforced HSC and a synthetic fiber reinforced HSC. These panels were subject to impact loading at their centers using a large instrumented drop-weight impact machine. The mass of the drop weight was 578 kg, with an impact velocity 1.9 m/s. Direct measurement of the central deflection at the bottom of the panel was made using a laser transducer. No significant changes in the failure mode were observed between static and low velocity impact loading, but the peak loads under impact loading were higher. Toughness evaluations were carried out to with central deflections ranging from 30～50 mm, for both static and impact loading. The fracture toughness could be related to the fiber type and volume. It was found that under low velocity impact loading, the toughness of steel reinforced concrete (SFRC), unlike that of synthetic fiber reinforced concrete (PPNFRC), was higher than under static loading at the same central deflection. It was concluded that this test method appears to be promising for impact studies.
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