Impact Resistance of High Performance Concrete Panels under High Velocity Projectile Collision

Abstract

Although many studies on impact and explosions have been made due to the frequent occurrence of collisions and explosions that threaten the safety of concrete structures, it is not easy to predict damage to a concrete panel under high velocity impact loads due to the complexity of the impact mechanism of concrete. In this paper, various experimental and analytical studies are carried out to evaluate the impact resistance of concrete, and a new local impact formula is proposed to predict local damage levels.<br/> In order to evaluate the impact resistance of a concrete panel with various parameters that were not investigated much, three experiments are carried out different. In the first experiment, the effect of steel fibers and wire mesh on impact resistance is investigated. In addition, aggregate size, panel thickness and projectile speed are used as parameters. The second experiment uses concrete strengths of 30 ~ 150 MPa and five kinds of bullets in order to evaluate the impact strength according to both concrete strength and the nose shape of the projectile. The third experiment evaluates the impact resistance of a thin panel using 180 MPa concrete. For the second and third experiments, a small impact test device developed by the author is used.<br/> Based on the experimental results, the impact mechanism is classified into six categories: deformed energy of the projectile, elastic penetration resistance energy of the panel, overall deformed energy of the panel, spalling-resistant energy, tunneling-resistant energy, and scabbing-resistant energy. Using these impact mechanism and energy conservation laws, new penetration depth, scabbing depth, scabbing limit thickness, and perforation limit thickness are proposed. The validity of the proposed impact formula is verified using the results of the current experiment and other research.<br/> Supplementary nonlinear analysis is performed to investigate how reinforcing bars affect the impact resistance of reinforced concrete panels, as the presence of reinforcing steel was identified as one of the unclarified parameters during the test. In addition, the effects of projectile size, panel area, and thickness on impact resistance, which are insufficiently studied in the experiments, are examined through nonlinear analysis.<br/>