xaxaxa

1. 8-4
Table 8-2 Gross and Cracked Moment of Inertia of Rectangular and Flanged Section
b
d
nAs
kd n.a.
bw
b
d
nAs
kd
n.a.
d
'
(n -1)A's
Gross Section Cracked Transformed Section Gross and Cracked Moment of Inertia
b
h
A's
As
b
h
As
b
bw
hf
h
b
h
hf
yt
A's
As
b
d
nAs
kd
n.a.
b
d
nAs
kd
n.a.
d'
(n -1)A's
Without compression steel
With compression steel
Without compression steel
With compression steel
n
E
E
B
b
nA
I
bh
12
kd 2dB 1 1 /B
I bk d /3 nA d kd
s
c
s
g
3
cr
3 3
s
2
=
=
( )
=
= + −
( )
= + −
( )
Without compression steel
With compression steel
With compression steel
kd C 2d h f 2rd f r 1 f r 1 C
I b b h 12 b k d 3 b b h kd h 2
nA d kd n 1 A kd d 2
f
2
cr w f
3
w
3 3
w f f
2
s
2
s
= + + ′
( )+ + +
( ) − + +
( )






= −
( ) + + −
( ) −
( ) +
−
( ) + −
( ) ′ − ′
( )
Without compression steel
n
E
E
C b nA , f h b b nA ,
y h 1/2 b b h b h b b h b h
I b b h 12 b h 12 b b h h h 2 y
b h y h 2
s
c
w s f w s
t w f
2
w
2
w f w
g w f
3
w
3
w f f t
2
w t
2
=
= ( ) = −
( ) ( )
= − −
( ) +
[ ] −
( ) +
[ ]
= −
( ) + + −
( ) − −
( ) +
−
( )
kd
kd C 2d h f 1 f 1 f C
I b b h 12 b k d 3 b b h kd h 2
nA d kd
f
2
cr w f
3
w
3 3
w f f
2
s
2
= +
( )+ +
( ) − +
( )






= −
( ) + + −
( ) −
( ) +
−
( )
r n 1 A nA
kd 2dB 1 rd /d 1 r 1 r /B
I bk d /3 nA d kd n 1 A kd d
s s
2
cr
3 3
s
2
s
2
= −
( ) ′ ( )
= + ′
( ) + +
( ) − +
( )






= + −
( ) + −
( ) ′ − ′
( )