Axial-Impact Resistance of CFRP-Confined Ultrahigh-Performance Concrete

Abstract

This study investigated the axial-impact resistance of unconfined and CFRP-confined UHPC. External confinement was provided by one to three plies of CFRP wraps with confinement ratios ranging from 0.126 to 0.378. A series of single- and multiple-impact tests was conducted using a Ø100 mm split Hopkinson pressure bar apparatus at mean strain rates ranging from 25 to 120 s−1. The dynamic behaviors of the specimens were examined and compared with those under quasi-static loading. The results indicate that the confinement of CFRP can significantly improve the axial-impact resistance of UHPC, exhibiting a strong strain-rate dependency. However, this sensitivity decreases with an increase in the confinement ratio. The dynamic failure modes of the CFRP-confined UHPC are different from those in the static tests, and the CFRP confinement ratio and impact energy determine the impact failure mode. Unlike in unconfined UHPC, a history of multiple impacts results in considerably lower accumulative damage in the confined UHPC. A new model was proposed to estimate the dynamic compressive strength of the CFRP-confined UHPC by considering the coupling effects of the confinement ratio and core concrete lateral inertia.