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 (8) (a) If the deflection criteria for both sidesway and beam
mechanisms are satisfied, then the member sizes from
Step 5 constitute the results of this preliminary
design. These members would then be used in a more
rigorous dynamic frame analysis such as the nonlinear
dynamic computer program DYNFA (Section 8).
(b) If the deflection criteria for a sidesway mechanism is
exceeded, then the resistance of all or most of the
members should be increased.
(c) If the deflection criterion for a beam mechanism of
the front wall or roof girder is exceeded, then the
resistance of the member in question should be
increased. The member sizes to be used in a final
analysis should be the greater of these determined
from Steps 8b and 8c.
Calculation:
Given:
(1) Pressure-time loading as shown in Figure 50a.
(2) Design criteria for reusable structure:
For a frame, [delta] /H = 1/50
[theta]max for a frame member are summarized in
paragraph 1.b (2) of this section.
(3) Structural configuration as shown in Figure 50b
(4) ASTM A36 steel.
Solution:
(1) Determine [alpha]:
bh = bv = 17 ft
qh = 5.8 x 17 x 12 = 1,183 lb/in
qv = 2.5 x 17 x 12 = 510 lb/in
[alpha] = qh/qv = 2.32
(2) Establish equivalent static loads:
(a) Local beam mechanism, w = DLF x qv
w = (1.0 x 510 x 12)/ 1,000 = 6.12 k/ft.
(b) Panel or combined mechanism, w = DLF x qv
w = (0.5 x 510 x 12)/1,000 = 3.06 k/ft
2.08-186
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