Dynamic response of GFRP-reinforced UHPC beams under close-in blast loading

Combined use of ultrahigh-performance concrete (UHPC) with glass fiber reinforced polymer (GFRP) reinforcement has the potential for further blast resistance enhancement of reinforced concrete (RC), due to the improved toughness of UHPC and the high strength-to-weight ratio of GFRP. This paper aims to fill the gap on the effectiveness of GFRP bars on the blast response of UHPC beams. The blast resistance of UHPC beams built with GFRP bars (UHPC-GFRP beams) is experimentally and numerically investigated in this paper. In the experimental scheme, twelve beams strengthened with various types of concrete and reinforcement are tested under near-field explosions. The properties of UHPC beams reinforced with GFRP bars are compared with specimens reinforced with normal-strength steel (NSS) and high-strength steel (HSS) bars. GFRP bars reduce the maximum displacements, which enhances the blast performance of UHPC beams. However, reinforcing UHPC beams with GFRP bars results in large rebound displacements. In addition, the coupled finite element model is adopted to predict the response of test beams. The numerical method using LS-DYNA achieves reasonable accuracy. Moreover, the damage process, energy characteristics, reaction forces, stress response and the effect of the compressive reinforcement are examined to better depict the damage mechanism of the UHPC-GFRP beams.