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Chapter 7 Column Design (Part 2)
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Shearson Lehman/American Express Information Services Center, New York City. (Courtesy of Owen Steel Company, Inc.)
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3 Table 5.1 may not be suitable for practical design conditions e.g. when a column is part of a continuous frame
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o Sidesway? o Lateral deflection of building frame because of : Lateral loads, or Unsymmetrical vertical loads, or Unsymmetrical frame o Sidesway inhibited (braced frame), Fig. 7.1 (p. 214) Braced by diagonal bracing, or Braced by rigid shear wall o Sidesway uninhibited ( moment frame) o Alignment charts may help find k (the effective length factor) o Fig 7.2 introduces the alignment chart produced by Jackson and Moreland
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Figure 7.1 Sidesway inhibited.
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A B g4 g1 g5 g6 g3 g2 g7 g8 c1 c2 c3A : joint A B: joint B C1 column 1 G1 girder 1 (beam)
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Figure 7.3
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To use the alignment charts o Preliminary sizes for girders and columns framing into the column in question is required o Assuming E = 29000 ksi for all columns and girders, the G is G = 10 for hinge support = 1 for fixed support
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Figure 7.2 Jackson and Moreland alignment charts for effective lengths of columns in continuous frames.
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Figure 7.4
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Figure 7.2 Jackson and Moreland alignment charts for effective lengths of columns in continuous frames.
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TABLE 7.1 Multipliers for Rigidly Attached Members
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Figure 7.6 Steel shapes, including their I/L values.
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Not applied for G=1 or G=10
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Table 7.2 Stiffness Reduction Factor, τ b Source: AISC Manual, Table 4-21, p. 4-321, 14th ed., 2011. “Copyright © American Institute of Steel Construction. Reprinted with permission. All rights reserved.”
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Figure 7.8
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Base Plates (Concentrically loaded columns) Spread column load over sufficient area to prevent overstressing of footing Steel base Welded, or Bolted
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Robins Air Force Base, GA. (Courtesy Britt Peters and Associates.)
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Figure 7.13 Column base plates.
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Figure 7.14
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Define : t = base plate thickness A 1 = base plate area = B x N A 2 = supporting concrete area P p = nominal bearing strength of the concrete Moment used to calculate t
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When A 1 covers A 2 When A 1 ≤ A 2 Ω c = 2.31
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Figure 7.15
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Figure 7.16
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Homework # 6 problems: 7-3 (part a only) and 7-14
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Figure P7-3
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