Assessment of Empirical Concrete Impact Formulas

Data from 145 recent impact tests of reinforced concrete walls with solid and pipe missiles are used to assess the accuracy of several empirical formulas. For solid missiles, penetration depths greater than six-tenths the missile diameter are predicted by the NDRC formula to within —25%, scabbing is predicted equally well by the NDRC, Bechtel, and Stone and Webster formulas, and perforation is predicted best by the CEA-EDF formula. For pipe missiles, the best overall agreement with data is obtained with the NDRC formulas, using the outside diameter in the penetration equation and the equivalent solid diameter in the equations for scabbing and perforation. The limitations of all of the formulas for impact conditions outside their range of applicability are pointed out. For example, the formulas are inapplicable for highly deformable missiles such as wooden poles and autos and give only approximate results for rotating or irregularly shaped missiles such as fragments from rotating machinery.