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)

-(I)
Elastic theory: cracked, uncracked and partially cracked sections 159
r-b-l
T.~T
xt~~
d-x
:=.L • As •
Cracked section
Fig. 5.2-2
(a)
ignore voids
£ZZZ:zf)4~~a~e~As
Equivalent section
(b)
I
where ac = Esf Ec (E, = 200 kN/mm 2 ; Ec from Table 2.5-6), (} = Asfbd,
e' = A~lbd and the other symbols are as defined in Fig. 5.2-l(a).
Equation (5.2-4) is plotted in Fig. 5.2-3.
With reference to the equivalent section, the well-known bending
formula is applicable:
M
fci = yxi
c
(5.2-S(a))
::s 0·21---+---+----+-+-1+1--+-f----1
J 015~~r-~--~~~+-~--_,
'0;{
o~~~~0-~2--~o~-3--o~.-4--0~-~s~o~
xfd
Fig. 5.2-3 Neutral axis depth of cracked section [6] (d'/d = 0.1)