Simplified Design for Columns - Simplified Design of Reinforced Concrete Buildings - page 169

1.0

Single
curvature

Zone 3

40

k ˜ u
r

22 34

Zone 1

Double
curvature

Zone 2

-0.5

-1.0
Zone 1: Neglect slenderness, sway and non-sway frames
Zone 2: Neglect slenderness, non-sway frames
Zone 3: Consider slenderness, moment magnification method (ACI 10.10.6 and ACI 10.10 .7)

Figure 5-14 Consideration of Column Slenderness

Table 5-4 Maximum Story Heights to Neglect Slenderness—Non-sway Columns

Column size
h (in.)

Maximum clear height
u

" (ft)

10 10

12 12

14 14

16 16

18 18

20 20

22 22

24 24

If the beam stiffness is reduced to one-fifth of the column stiffness at each end, then k = 2.2; consequently,
slenderness effects need not be considered as long as ˜ u / h is less than 3. As can be seen from these two
examples, beam stiffnesses at the top and the bottom of a column in a structure where sidesway is not prevented
will have a significant influence on the degree of slenderness of the column.

Due to the complexities involved, the design of slender columns is not considered in this topic. For a
comprehensive discussion of this topic, the reader is referred to Chapter 11 of Reference 5.5.