F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

436 Practical design and detailing
% moment redistribution = 100(1 - {Jb) = 17%
From Table 4.7-1 (or eqn 4.7-5),
K' = 0.139
M (520)(10 6 )
K = fcubd2 = (40)(350)(4752) = 0.165 > 0.139
Compression reinforcement is required.
From Fig. 11.5-9(a),
d' =50 mm
From Table 4.7-2 (or eqns 4.7-7 and 4.6-3),
zld = 0.81 xld = 0.42
From eqn (4.7-10),
A~= 0. 8~Y{d ~ud') (where Mu = K'fcubd 2 )
- (520)(10 6 ) - (0.139)(40)(350)(4752)
- (0.87)(460)(475-50)
= 476 mm2
(From Section 4.10, when compression steel is required, the minimum
area to be provided = 0.2% bh = 385 mm2 < 476 mm2 OK)
From eqn (4.7-11),
As = O.~fyz + A~ (where Mu = K'fcubd 2 )
(0.139)( 40)(350)( 4752)
= (0.87)(460)(0.81)(475) + 476
= 3327 mm2
Top 5T32 ( 4021 mm2)
Span AB (Fig. 11.5-9(b)). From Section 4.8,
Bottom 2T32 (1608 mm2)-see Step 9
effective flange width = 350 + 0.2(0.7 of 9000)
= 1610 mm
From bending moment envelope (Fig. 11.5-6),
M = 522 kNm
_M_ - (522)(10 6 )
fcubd2 - (40)(1610)(5Q02)
(where d = 500 from Fig. 1L5-9(b))
= 0.033