Influence of steel reinforcement on the performance of an RC structure subjected to a high-velocity large-caliber projectile

Abstract

The reinforcement setting in reinforced concrete (RC) protective structure should be optimized to resist the impact of high-velocity large-caliber projectiles (LCPs), which is yet to be clearly understood. This study adopts a high-fidelity finite element analysis (FEA) approach to examine the influence of steel reinforcement setting, including the diameter/spacing/strength of reinforcement, the number/spacing/distribution depth of the mesh layer, and the reinforcement ratio, on the performance of RC structure against the large-caliber projectile impact. The FEA approach utilizes an improved dynamic constitutive model of concrete recently proposed by the authors to capture the responses of concrete, i.e., the penetration resistance, cratering, scabbing, and cracking failure, and the *CONSTRAINED_BEAM_IN_SOLID coupling method to consider the bond-slip relation between steel reinforcement and concrete. By simulating the 64 mm-diameter projectile impact tests on the plain concrete (PC) and RC targets, it validates the established FEA approach in contrast to that using the existing concrete models in LS-DYNA, i.e., the Holmquist-Johnson-Cook, Riedel-Thoma-Hiermaier, and Karagozian & Case concrete models, and the full coupling method, i.e., the *CONSTRAINED_LAGRANGE_IN_SOLID. The performance of the RC target struck by a 154 mm-diameter LCP is further numerically studied using the validated FEA approach. Based on more than fifty simulation cases, it derives the optimal reinforcement setting for the engineering design: (i) increasing the mesh layer number should be given priority to increasing the reinforcement ratio; (ii) the optimal rebar diameter and spacing are 1/15 and 1/2 of projectile diameter, respectively; (iii) uniform distribution of reinforcement layer along target thickness is suggested; (iv) normal strength reinforcement is preferred; (v) the practical highest reinforcement ratio is 4% to reduce structural thickness.