Civil Engineering Reference
In-Depth Information
column (
r
c
), which is necessary to introduce to the column to provide some mean-
ingful confinement effect; and the longitudinal steel reinforcement ratio (ρ
s
). It can
be easily shown that the effective area to concrete area ratio (
A
e
/
A
c
) is found to be
b
h
h
b
(
)
2
(
)
2
hr
−
2
+
br
−
2
c
c
1
−
−ρ
s
A
A
3
1
A
(7.11)
e
g
=
−ρ
c
s
The strength and strain efficiency factors (κ
a
, κ
b
) are functions of the effective
area of confined rectangular section (
A
e
), determined from Equation (7.11), and the
column aspect ratio (
b
/
h
) as postulated by Lam and Teng (2003b). The respective
expressions of these variables are given by Equations (7.12) and (7.13):
2
κ=
A
A
b
h
e
(7.12)
a
c
0.5
κ=
A
A
h
b
e
(7.13)
b
c
7.2.3 C
ombineD
C
onFinement
oF
Frp
anD
t
ranSverSe
S
teel
in
C
irCular
S
eCtionS
The
f
flf,
expression given by Equation (7.7) is updated by Abd El Fattah (2012) to
account for the contribution of FRP and transverse steel in confining the core:
2
nt E
D
ε
2
kA f
dS
f
f
fle
e pyh
f
=
+
(7.14)
fle
×
c
(
)
2
1
1
−
−ρ
s
d
1
1
−
−ρ
s
d
cc
2
2
c
where
k
e
=
for spiral transverse steel and
k
e
=
for circular hoop
c
cc
transverse steel,
s
′ is the clear spacing of hoops or clear pitch of spiral,
d
c
is the
diameter of concrete core c/c, and ρ
cc
is the ratio of longitudinal reinforcement area
to the area of core.
Similarly, the
f
flf,
expression that confines the cover of the column only is deter-
mined by
2
nt E
D
ε
f
f
fle
f
=
(7.15)
flf,
The values of the ultimate confined strength of the core and cover (
f
cce
and
f
ccf
) are determined from Equation (7.6) by substituting
f
fle
and
f
flf,
, resp fle ct ively.
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