Example Problems -Cont. - dm2_080189

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(8) Determine the total resistance, Ru, and peak pressure
load, B.  Enter Figure 6-7 of NAVFAC P-397 with the ratios
T/TN and B/Ru in order to establish the ductility
ratio, [mu].  Compare with given criteria.
(9) Calculate the equivalent elastic deflection, XE, as given
by:
XE = Ru/KE
and establish the maximum deflection, Xm, given by:
Xm = [mu]XE
Compute the corresponding member end rotation.  Compare [mu]
with the criteria in paragraph 1.b. of this section.
(10) Check for shear using Equation (92) and Table 9.
(11) If a different member size is required, repeat Steps 1
through 10 by selecting a new dynamic load factor.
Calculation:
Given:
(1) Pressure-time loading as shown in Figure 48a.
(2) Design criteria:  Reusable structure, maximum ductility
ratio = 3, maximum end rotation [theta] = 1o, whichever
governs.
(3) Structural configuration as shown in Figure 48b.
(4) Steel properties:  Fy = 36 ksi (ASTM A36 steel);
E = 30 x 103 ksi.
Solution:
(1) Determine the equivalent static load (i.e., required
DLF = 1.0 for reusable structure
w = 1.0 x 5 x 4.5 x 144/1,000 = 3.24 k/ft
(2) Determine required Mp (Table 5).
Mp = wL2/8 = (3.24 x 172)/8 = 117 k-ft
(3) Select a member.
(S + Z) = 2Mp/Fdy = (2 x 117 x 12)/39.6
= 71.0 in3
where Fdy = cFy = 1.1 x 36 = 39.6 Ksi
2.08-172