Example Problems - dm2_080075

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(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