Civil Engineering Reference
In-Depth Information
guideline [1, 2] part 1 Eq. (RV 6.84):
7
?
10
3
2264
?
10
2
7
?
10
6
N
0
;
Eqp
A
i
M
0
;
Eqp
2764
:
20
:
mm
2
σ
cp
13
:
63 N
=
2
D
2
500
9
?
10
6
I
i
?
3653
:
?
The factor
β
c
(
Δ
t
) takes into account the chronological development of the action. As this
is a customary strengthening assignment, we shall select
β
c
(
Δ
t
)
=
1.0 according to
DAfStb guideline [1, 2] part 1 Eq. (RV 6.75).
It is also important to check whether non-linear creep needs to be considered. To do this,
the degree of utilization under a quasi-permanent load must be calculated. As this
is
<
0.45, it is not necessary to consider non-linear creep and therefore
β
0,k
=
1 (see
DAfStb guideline [1, 2] part 1 Eqs. (RV 6.82) and (RV 6.83)).
k
σ
σ
cp
13
63
38
:
f
cm
0
:
36
0
:
45
Likewise, the in
uence of the concrete compressive strength at the time of strengthening
must be considered according to DAfStb guideline [1, 2] part 1 Eq. (RV 6.80):
16
8
:
16
8
:
f
c
p
3
p
β
f
c
2
:
73
With these factors and factor [k7] from Table 8.2 at our disposal, we can now calculate
the creep of the con
ned concrete:
13
:
63
33 000
0
:
44 mm
=
m
ε
cc
Δ
t
0
:
39
?
1
?
2
:
73
?
1
?
8.5.2 Properties of the CF sheet
The stiffness of the wrapping relative to the column diameter
D
is required for the next
calculations. According to DAfStb guideline [1, 2] part 1 Eq. (RV 6.66), this relative
stiffness is
2
?
E
L
?
t
L
D
2
?
230 000
?
0
:
75
mm
2
E
jl
690 N
=
500
We also need the long-term characteristic value of the strain in the confining
reinforcement, which is calculated according to DAfStb guideline [1, 2] part 1
Eq. (RV 6.67). This is calculated depending on the coefficients for considering
the influence of the change of direction at the member
α
r
=
[
k
2
]
0.25, temperature
=
α
T
=
[
k
3
]
0.7, moisture
α
F
=
[
k
4
]
1.0, type of loading
α
E
=
[
k
5
]
1.0, duration of
=
=
=
loading
t
) (Section 8.5.1),
the factor for taking into account the scatters of the creep deformations
α
Z
=
[
k
6
]
1.0 and the creep of the confined concrete
ε
cc
(
Δ
=
α
k
=
1.5,
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