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 (7) Compute the moment of inertia, I, for a 1-inch width.
I = bd3/12
= 1 x (3/8)3/12
= 0.004394 in4/in
(8) Calculate the equivalent elastic stiffness, KE.
KE = 160EI/bL4
= 160(29)(106)(0.004394)/1(15.75)4
= 331.3 psi/in
(9) Determine the equivalent elastic deflection, XE.
XE = ru/KE
= 56.11/331.3
= 0.1694 in
(10) Calculate the effective mass of element.
Average of elastic and plastic transformation factors
from Table 10
KLM = (0.78 + 0.66)/2
= 0.72
Unit mass of element, m
m = w/g
= (3/8 x 1 x 1 x 490 x 106)/(1,728 x 32.2 x 12)
= 275.2 lb-ms2/in2
Effective unit mass of element, me (Section 6.6, NAVFAC
P-397)
me = mKLM
= 275.2 x 0.72
= 198.1 lb-ms2/in2
(11) Calculate the natural period of vibration, TN.
TN = 2[pi](198.1/331.3)1/2
= 4.859 ms
(12) Determine the door response.
Peak overpressure, B = 27.0 psi
Peak resistance, ru = 56.11 psi
Duration, T = 22.81 ms
Natural period of vibration, TN = 4.859 ms
2.08-284
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