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 8.
EXAMPLE PROBLEMS.
a.
Design of Beams for Pressure-Time Loading.
Problem:
Design a purlin or girt as a flexural member which responds to a
pressure-time loading.
Given:
(1) Pressure-time load, P-T.
(2) Design criteria [theta]max and [mu]max.
(3) Span length, L.
(4) Beam spacing, b.
(5) Support conditions.
(6) Properties and type of steel.
Solution:
(1) Determine the equivalent static load, w, using the
following preliminary dynamic load factors:
0.8 for a non-reusable
DLF =
1.0 for a reusable
w = DLF x p x b
(2) Using the appropriate resistance formula from Table 5 and
the equivalent static load derived in Step 1,
determine Mp.
(3) Select a member size using Equation (83) or (84). Check
the local buckling criteria of paragraph 3.a.(5) for the
member chosen.
(4) Determine the mass, m, including the weight of the decking
over a distance center-to-center of purlins or girts, and
the weight of the members.
(5) Calculate the equivalent mass, me, using Table 6-1 of
NAVFAC P-397 or Table 10 of this manual.
(6) Determine the equivalent elastic stiffness, KE, from
Table 7 of this manual.
(7) Calculate the natural period of vibration, TN, using
Equation (91).
2.08-171
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