Civil Engineering Reference
In-Depth Information
E
L
modulus of elasticity of surface-mounted CF sheet relative to fibre cross-section
t
L
theoretical thickness of fibre cross-section in CF sheet
D
diameter of reinforced concrete column
ε
juk
characteristic ultimate strain assumed for CF sheet.
ε
juk
k
?
k
?
k
?
k
?
k
?
ε
Lk
α
k
?
ν
?
ε
cc
Δ
t
(7.42)
ε
Lk
characteristic ultimate strain in CF sheet determined in tensile test on strip of CF
material
α
k
coefficient to allow for the increased scatter of creep deformations:
α
k
=
1.5
ν
Poisson's ratio:
ν
=
0.2
ε
cc
(
Δ
t
)
longitudinal deformation of reinforced concrete column due to creep.
σ
cp
E
cm
ε
cc
Δ
k
?
β
c
Δ
?
β
f
cm
?
β
0
;
k
?
(7.43)
β
c
(
Δ
t
)
coef
cient for describing the development of creep over time.
<
1
for normal strengthening tasks
0
:
3
β
c
Δ
Δ
t
=
1
:
7
β
H
Δ
(7.44)
:
members with short remaining lifetimes
t
=
1
:
7
Δ
t
remaining lifetime [d]
β
H
coefficient for describing the influence of moisture.
mm
2
250
for
f
cm
35 N
=
β
H
(7.45)
for
f
cm
>
35 N
=
mm
2
250
?
α
3
mean value of uniaxial concrete compressive strength [N/mm
2
]
f
cm
β
(
f
cm
) coefficient to allow for the influence of the concrete compressive strength at the
time of strengthening.
16
8
f
cm
:
p
β
f
cm
(7.46)
β
0,k
coef
cient to allow for the loading level with respect to creep of the con
ned
concrete.
e
2
:
7
?
k
σ
0
:
45
for
k
σ
>
0
:
45
β
0
;
k
(7.47)
1
for
k
σ
0
:
45
k
σ
stress-strength ratio of concrete:
k
σ
=
σ
cp
/
f
cm
σ
cp
creep-effective concrete compressive stress due to quasi-permanent actions.
N
Eqp
A
i
M
0Eqp
I
i
σ
cp
(7.48)
N
Eqp
axial load due to quasi-permanent actions at the serviceability limit state
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