Parametric study on local impact damage of concrete members

High-velocity impact causes local failure in reinforced concrete structures.1,2 For civilian and military structures under impact load, the impact load resistance needs to be accurately evaluated. However, due to the complicated mechanism of concrete subjected to impact load, the impact resistance of concrete members has been studied by a number of tests and empirical methods. In order to predict the penetration depth of concrete targets, Petry et al.2 proposed a method based on a simplified equation of motion for the first time, considering the projectile mass, impact velocity, sectional area of the projectile, and factor related to concrete penetrability. Army Corps of Engineers (ACE)3 evaluated the allowable concrete target thickness to restrain significant local failure, and National Defense Research Committee (NDRC)4 and Kennedy5 additionally considered the nose shape effect of the projectile in ACE model.4 The effects of maximum aggregate size, elastic modulus of the projectile, strain-rate of concrete, thickness of the concrete target, concrete density, configuration of the projectile, and hybrid-fibers on the penetration depth of the concrete target have been studied.6-15 Unlike empirical models, Hwang et al.16 developed an energy-based model for the penetration depth and residual velocity of a projectile. Comparing the kinetic energy of a projectile with the resistant energy of a concrete target directly, the penetration depth of the concrete target can be estimated. Although the energy-based model predicts well the penetration depth of the concrete target, it is difficult to understand the effect of each design parameter on the penetration depth intuitionally in initial design stage. Thus, to investigate the impact damage of the concrete target under high velocity impact, a parametric study was performed. The modified NDRC model5 and energy-based model16 were used, and the penetration depth of the local impact-damaged concrete target under various design conditions was examined. The analysis results can provide an insight to researchers and practical engineers.