0053

FIGURE 31.29 Pin-based stepped crane columns: (a) frame subjected to gravity loads and (b) frame subjected to fictitious lateral loads.

1BC = Ief = 1CE = Iu = 5420 in.4 (2.26 x 109 mm4) Abc = AEF = ACE = Au = 34 .14 in.2 (22,026 mm2)

Solution

1. Apply a set of fictitious lateral forces with a = 0.001 as shown in Figure 31.29b

2. Perform a first-order analysis and find

( Ai)b = 0 .1086 in. (2 . 76mm) and ( D1)F = 0 .1077 in. (2 .74mm)

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