Impact of Deformable Missiles on Concrete Walls

Relationships for the penetration depth of the missiles, the wrinkling or collapse length of the missiles, critical missile stress, the time history of impact, and the spalling of the target are developed. The derived relationships are based on a simplified force-time history which assumes that the initial penetration of the missile occurs without significant deformation of the missile until the critical stress of the missile is reached. At that time the missile wrinkles or collapses and negligible penetration occurs. During this stage of impact it is assumed that diagonal cracks, initiating at the end of the missile are formed and propagate to the backface reinforcing while splitting cracks develop and propagate to yield hinge lines that form in the plane of the reinforcing. Repenetration resulting from moving the failure cone described above is the final stage of impact prior to spalling. For cases in which the strength of the wall is greater than that of the missile, the time history is modified to account for the fact that the missile does not penetrate.