Penetration and spallation depth estimation for concrete structures

The predictability of the NDRC equations for penetration and spallation depth, particularly with respect to large solid missiles similar to those expected in a nuclear power plant, are reevaluated here. Presently, available test results for both solid missiles and bullets are used for this purpose. Penetration depths are estimated using NDRC, statistical NDRC, and the proposed Haldar equations. The Haldar equations are developed by introducing a nondimensional impact factor. This study confirms the industry notion that the NDRC equations predict the penetration depth reasonably well for small missiles; however, they fail to do so for large missiles. The proposed Haldar equations predict the penetration depth accurately for both large solid missiles and bullets. The spallation depths are estimated indirectly by three methods from the information on the penetration depths estimated by the NDRC, statistical NDRC, and Haldar equations. They are also estimated directly using the impact factor concept. This direct method is found to be the best. However, the coefficients of variation for penetration and spallation depth estimation are considerably large. Thus, for any probabilistic formulation, they need to be considered probabilistically. It is recommended that the proposed relationships for penetration and spallation depth estimation should be used in the future using the impact factor concept. (orig.)