Effects of Reinforcement on Ballistic Resistance of RC Targets

Abstract

Reinforced concrete (RC) is a widely used construction material, renowned for its high strength and durability. Despite this, when subjected to high-velocity impacts, such as those from ballistic projectiles or blast loading, RC structures are prone to local failure. This can significantly damage their structural integrity, potentially leading to total failure. Therefore, understanding the failure behavior of RC structures under such impact loads is of critical importance. The rebar ratio is one of the factors that affect the erosion behavior of RC targets. The rebar ratio refers to the proportion of rebar (reinforcing steel) in the RC target relative to the concrete. A higher rebar ratio is expected to result in higher resistance to local failure, as the rebar provides additional reinforcement to the concrete. The hardness of the projectile is another factor that affects the failure behavior of RC targets. An ogive-nose steel projectile is expected to cause more profound local failure than a soft-type projectile, as a projectile is a relatively minor projectile deformation after a collision. In this study, a series of impact tests were performed on RC targets with different rebar ratios and impact velocities using ogive-nose steel projectile. The penetration depth, scabbing& perforation limit were measured and analyzed as a function of the rebar ratio and impact velocity. The accuracy of existing empirical formulae recommended by various design standards for military and nuclear structures was verified using the results, and a modified empirical formula for predicting the penetration depth of RC targets subjected to impact loading was developed. A total of 21 RC targets were tested in this study, with four different rebar ratios (0%, 1.6%, 2.5%, and 3.4%) and a constant target size of 600mm x 600mm x 500mm. The targets were made of normal-weight concrete with a compressive strength of 52 MPa. The rebar was made of high-strength steel with a yield strength of 470 MPa. The impact tests were performed using a 60 mm single-stage gas gun in EPTC, in which an ogive-nose steel projectile was launched through helium gas pressure and collided with the RC target at the target speed. The impact velocity was varied from 550m/s to 850m/s in increments of 50m/s. The penetration depth, scabbing& perforation limit was measured after each impact test and recorded for analysis. The results showed that the rebar ratio sig the local failure behavior of the RC targets. The targets with a higher rebar ratio (2.5% and 3.4%) showed less erosion than those with a lower rebar ratio (0% and 1.6%). The results also showed that the impact velocity sig the failure of the RC target, with higher impact velocities resulting in higher impact damage. Based on the results, a modified empirical formula was suggested for predicting the impact damage of RC targets subjected to impact loading. The formula takes into account both the rebar ratio and impact velocity. Then, the validity of the proposed formula was verified by applying it to the existing experimental data of 153ea and FEA using the LS-Dyna program. In conclusion, this study has investigated the impact response of reinforced concrete (RC) targets under various loading conditions, including different rebar ratios and striking velocities. The results have shown that the rebar ratio can significantly impact the RC target's response to impact loading. The modified empirical formula developed in this study provides a valuable tool for predicting the response of RC targets to impact loading. It can inform design and engineering decisions related to impact resistance. Future work in this area could include further testing with a larger number of RC target specimens and developing more detailed numerical models better to understand the mechanisms of impact damage in RC targets. Additionally, it may be helpful to investigate the impact response of RC targets under more realistic loading conditions, such as those that incorporate dynamic loading and material nonlinearities. Overall, this study has contributed to a deeper understanding of the impact response of RC targets and has provided valuable insights into the factors that can affect this response. This study's findings can inform the design and engineering of structures subjected to impact loading and ensure that these structures are adequately protected against impact damage.