Effect of Reinforcing Steel on the Impact Resistance of Reinforced Concrete Panel Subjected to Hard-Projectile Impact

•The effect of reinforcing bars on the impact resistance of RC panel was investigated.•Hard-projectile impact testing for RC panel and numerical analysis were conducted.•Reinforcing bars afforded a confining force to concrete, and entrapped fragments.•Narrowing the rebar spacing enhanced the impact resistance.•Rebar diameter and yield strength barely affected impact resistance. Experimental and numerical studies were conducted to investigate the effect of reinforcing steel on the impact resistance of reinforced concrete structures and to reveal its mechanism. Hard-projectile impact tests using a single-stage gas gun were performed with reinforced concrete panels to simulate a nuclear power plant structure. Parametric analysis was conducted with a numerical model that applied a finite element method coupled with smoothed particle hydrodynamics using the following four variables: the impact velocity of the projectile as well as yield strength, spacing and diameter of the reinforcing steel. The experimental and numerical analysis results indicated that the impact resistance was significantly affected by the spacing of the reinforcing steel, but not by the yield strength or the diameter of the reinforcing steel. Narrower rebar spacing improved the impact resistance due to the enhanced confining and fragment trapping effects.