Structural Concrete - Hassoun

Summary 439
3. The value of K can be determined from the alignment chart (Fig. 12.3) or Eqs. 12.2
through 12.6.
Section 12.4
Member stiffness is EI:
E c = 33w 1.5√ f ′ c
The moment of inertia, I, may be taken as I = 0.35I g for beams, 0.70I g for columns, 0.70I g
for uncracked walls, 0.35I g for cracked walls, and 0.25I g for plates and flat slabs.
Alternatively, the moments of inertia of compression and flexural members, I, shall be permitted
to be computed as follows:
1. Compression members:
(
I = 0.80 + 25 A )(
st
1 − M )
u
A g P u h − 0.5P u
I
P g ≤ 0.875I g
o
2. Flexural members:
(
I =(0.10 + 25ρ) 1.2 − 0.2 b )
w
I
d g ≤ 0.5I g
(Eq.12.2)
(Eq.12.3)
Section 12.5
The effect of slenderness may be neglected when
Kl u
r
⎧
⎪
22 (for unbraced frames) (Eq.12.8)
≤ ⎨
⎪
34 − 12 M 1
≤ 40 (for braced columns) (Eq.12.5)
⎩
M 2
where M 1 and M 2 are the end moments and M 2 > M 1 .
Section 12.6
1. For nonsway frames,
or the more simplified equation
More simply,
The Euler buckling load is
EI = 0.2E cI g + E s I se
1 + β dns
(Eq.12.10)
EI = 0.4E cI g
1 + β dns
(Eq.12.11)
β dns =
1.2D
1.2D + 1.6L
EI = 0.25E c I g (β dns = 0.6)
P c = π2 EI
(Kl u ) 2
(Eq.12.4)
(Eq.12.12)
(Eq.12.13)