# Chapter 7 Column Design (Part 2). Shearson Lehman/American Express Information Services Center, New York City. (Courtesy of Owen Steel Company, Inc.)

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Chapter 7 Column Design (Part 2)

Shearson Lehman/American Express Information Services Center, New York City. (Courtesy of Owen Steel Company, Inc.)

3 Table 5.1 may not be suitable for practical design conditions e.g. when a column is part of a continuous frame

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

Figure 7.1 Sidesway inhibited.

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)

Figure 7.3

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

Figure 7.2 Jackson and Moreland alignment charts for effective lengths of columns in continuous frames.

Figure 7.4

Figure 7.2 Jackson and Moreland alignment charts for effective lengths of columns in continuous frames.

TABLE 7.1 Multipliers for Rigidly Attached Members

Figure 7.6 Steel shapes, including their I/L values.

Not applied for G=1 or G=10

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.”

Figure 7.8

Base Plates (Concentrically loaded columns) Spread column load over sufficient area to prevent overstressing of footing Steel base Welded, or Bolted

Robins Air Force Base, GA. (Courtesy Britt Peters and Associates.)

Figure 7.13 Column base plates.

Figure 7.14

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

When A 1 covers A 2 When A 1 ≤ A 2 Ω c = 2.31

Figure 7.15

Figure 7.16

Homework # 6 problems: 7-3 (part a only) and 7-14

Figure P7-3

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