Scabbing Thickness.

DOE-STD-3014-96

APPENDIX C

missile shape factor = 0.72 for flat-nosed bodies, 0.84 for

blunt-nosed bodies, 1.00 for average bullet-nosed

(spherical end) bodies, and 1.14 for very sharp-nosed

bodies;

missile weight (lb);

effective missile diameter (in.);

missile impact velocity (ft/sec).

For noncircular or irregular shaped missiles, D is computed as the equivalent

diameter of the contact area. The formula is only applicable when the target is

sufficiently thick to prevent scabbing. Scabbing would lead to more penetration

than would be predicted by the formula. The penetration depth, x, is used to

predict scabbing and perforation thickness.

The NDRC formula was derived from impact data for missile velocities greater

than 500 ft/sec or 340 mph (152 m/s) and missile diameters ranging from 1 in. to

16 in. (2.54 cm to 40.6 cm). The testing conditions included ratios of target

thickness to missile diameter equal to or greater than 3. However, because it

was based on the theory of penetration, it can be extrapolated beyond the range

of available test data. The effects of reinforcing are inherently included.

In a properly designed reinforced concrete structural member with adequate

longitudinal and transverse reinforcing steel in each direction, the spreading of

the radial cracks produced by the impact will be inhibited by the rebars, and the

amount of concrete that spalls off the front face will be limited.

The missile velocities from an aircraft crash event are typically less than

500 ft/sec or 340 mph (152 m/s ), and the missile diameters are greater than

12 in. (30.5 cm). Missiles impacting the structures are also mostly deformable.

Because of these factors, the Modified NDRC formula shall only be used to

predict local penetration of the reinforced concrete structures. For further details

on limitations, see Reference 2.

C-7