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PROBLEM (7.103) Consider the reinforced concrete beam of Fig. 7.103. For ( c
σ
)all = 10
MPa and (
s
σ
)all = 140 MPa., determine the largest bending moment M that may be applied to
about the z axis of the beam.
Given: b = 400 mm, d = 600 mm, As = 2500 mm2, n = 8
SOLUTION
Equation (7.43a) becomes
216 16
( ) ( ) (2500) (600)(2500) 0
400 400
kd kd+− =
or 01060)(100)( 32 =×−+ kdkd
Solving,
mmkdmmkd 400600200
=
−
=
From Eq. (d) of Example 7.15:
6
10 10 0.2
( )( ) (0.4 0.2)(0.6 )
232
c
ckd 3
kdd
σ
×
=−= ×−
Mb
mkN ⋅= 213
63
( ) 140 10 (2.5 10 )(0.533)
3
sss kd
MA d
σ
−
=−=××
all ⋅6.186
mkN ⋅= 6.186
Thus, M= mkN
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