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)

130 Reinforced concrete beams-the ultimate limit state
(a)
Fig. 4.8-3
h
b- bw
t==Lt
c=J-- ::==J
I
I
I
I
I
I
I
I
I
I
·-·-~·
(b) Flange & web
components.
~·4Sf;~/2
n0·4Sf (b-bw)hf
cu
Sht
j
(c) Forces on flange
component.
Step4
Calculate Kr.
M- Mur
Kr = fcuhwd2 (4.8-5)
where bw is the web width. If Kr ~ 0.156 (where 0.156 is K' as given by
eqn 4.6-5), then calculate A. from
Mur M- Mur
A = + (4.8-6)
s 0.87/y(d -0.5hr) 0.87/yz
where z is obtained from Table 4.6-1.
Comments
(a) With reference to Fig. 4.8-4, the moment to be resisted by the web
component (Fig. 4.8-4(c)) is the excess moment M - Mur (see
eqn 4.8-4 for Mur). Equation (4.8-5) treats the web component
as a rectangular section, in the same way as eqns (4.6-4) and (4.6-5)
do.
r--- b---,
T
d
..~..l ___ •• As
..fbwl--
.:Jh,
O·Sht
Oo45x
[:::::r--c:=::3-_..1l o-t;c:::~::~=-~
; ~ ,-·-- I
~ ~ d-O·Sx z•d-0·45x
: I l ~
Asf ~~-~r
Asw •• ___ _..
Actual section
Moment= M
(a)
Fig. 4.8-4
Flange component
Moment = Mut
(b)
Web component
Moment= M- Muf
lcl