(5) Determine impulse of shock loading using one of Figures

4-17 through 4-62 of NAVFAC P-397.

(6) Determine duration of shock load using Equation (17) and

determine fictitious peak shock pressure.

Calculation:

Given:

(1) Diameter of hole in roof = 5.75 feet.

(2) Charge weight = 30.8 pounds TNT, located at geometric

center of cubicle.

(3) Cubicle has dimensions of 15 x 10 x 10 feet and the wall

in question is 15 x 10 feet.

Solution:

(1) A = [pi]d2/4 = [pi]x 5.752/4 = 26.0 ft2

W = 1.2 x Charge Weight = 1.2 x 30.8 = 37.0 lb

V = L x W x H = 15.0 x 10.0 x 10.0 = 1,500.0 ft3

(2) A/V2/3 = 26.0/1,5002/3 = .20 < .21

O.K.

W/V = 37.0/1.500.0 = .025 lb/ft3

A/W2/3 = 26.0/37.02/3 = 2.34 ft2/lb2/3

(3) Scaled impulse of gas pressure from Figure 10.

ig/W1/3 = I,190.0 psi-ms/lb1/3

ig = 1,190.0 x 371/3 = 3,965.0 psi-ms

(4) Peak gas pressure from Figure 8.

Pg = 210.0 psi

Fictitious duration is:

t'g = 2ig/Pg = 2 x 3.965.0 = 37.8 ms

210.0

(5) Scaled shock impulse for 15- by 10-foot wall using

Figure 4-62 of NAVFAC P-397 and L/H = 1.50, h/H = .50,

1/L = .50, L/RA = 3.00, ZA = 1.50, and N = 4.

ib/W1/3 = 250 psi-ms/lb1/3

ib = 371/3 x 250 = 833.0 psi-ms

2.08-59