Paper Title
Safety Distance from Ricocheted Concrete Debris onto Concrete

When a building or ammunition explodes, many debris are scattered and collides with the ground and rebounds. This is called ricochet phenomenon. Debris is dangerous because it contains large kinetic energy. The medium affects the ricochet of the debris, and the air drag affects the debris flight. These should be considered to set a safety distance from debris more exactly. In this study, FEM was used to investigate the ricochet about the concrete debris and medium. Also, the flight trajectory was studied with the air drag force according to the Reynolds number. The ricocheted angle is very low when the debris collides onto concrete. This is because the repulsion force in the direction perpendicular to the ground is weak when the debris collide onto the concrete. Therefore, the effect of increasing the travel distance of the debris is very small from ricochet. Index Terms - Ricochet, Drag force, Concrete, Safety distance