
 DOESTD301496
Evaluation of Reinforced Concrete Targets.
6.3.2.1
6.3.2.1.1
Scabbing Thickness. The scabbing thickness (ts) is defined as
the panel thickness that is just large enough to prevent the
peeling off of the back face of the panel opposite to the face of
impact. In 1981, Chang (Reference 4) proposed an empirical
formula based on lower velocity missiles (less than about
500 ft/sec [152 m/s]) to predict mean scabbing thickness for
reinforced concrete panels subjected to a cylindrical rigid
(nondeformable) steel missile impact:
0.13
(MV 2)0.4
U
ts = 1.84
(61)
V
/ 0.4
0.2
D
(fc)
where:
U
=
reference velocity = 200 ft/sec;
V
=
missile impact velocity (ft/sec);
M
=
mass of the missile = W/g,
where:
W = missile weight (lb),
g = 32.2 ft/sec2;
D
=
effective missile diameter (ft);
f/c
=
ultimate compressive strength of concrete
(lb/ft2).
ts
=
scabbing thickness (ft)
To prevent scabbing, minimum concrete thickness, td, should
1.1ts, where ts is given by the above formula. Other
be
formulas, as listed in Table I and discussed in Appendix C,
may also be used if the missile and target characteristics
(missile size, velocity, and deformability, and target rigidity and
thickness) are comparable to those used in the formula above.
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