Civil Engineering Reference
In-Depth Information
a
k
a
?
ξ
?
d
L
0
:
37
?
0
:
26
?
160
15
:
70 mm
z
s1
d
s1
a
140
15
:
70
124
:
30 mm
z
L
h
a
160
15
:
70
144
:
30 mm
We can therefore work out the admissible moment for the cross-section. As this
corresponds to the acting moment, the second boundary condition for the iteration
is also satisfied.
61
?
10
3
08
?
10
3
m
Rd
z
s1
?
F
s1d
z
L
?
F
Ld
124
:
3
?
192
:
144
:
3
?
96
:
37
:
81 kNm
=
m
m
Ed
The values for the other cracks are worked out similarly (see Table 4.4).
The difference between two cracks is the stress resultant for that concrete element
between cracks; the
figures are given in Table 4.5. In this table,
F
LEd,1
is the strip force at
the less heavily stressed crack
x
1
and
F
LEd,2
that at the more highly stressed crack
x
2
.
Δ
F
LEd
F
LEd
x
cr
s
r
F
LEd
x
4.5.4.2 Determining the bond strength
As an example, we shall only determine the resistance at element 3. The resistance
at the element between cracks depends on the action and so this must be determined
for every element. The element with the greatest change in force need not necessarily
be the critical element. According to DAfStb guideline part 1, RV 6.1.1.3.6, or
Section 3.3.3.3 of this topic, the admissible change in the strip force consists of three
components:
Δ
F
LRd
Δ
F
Lk
;
BL
Δ
F
Lk
;
BF
Δ
F
Lk
;
KF
γ
BA
With the strip force
F
LEd,1
at the less heavily stressed crack, the
first component from
the basic value of the bond of externally bonded reinforcement is
<
F
Lk
;
BL
Δ
F
Lk
;
BL
Δ
F
Lk
;
BL
Δ
for
F
LEd
;
1
F
Lk
;
BL
F
LEd
;
1
F
Lk
;
BL
Δ
F
Lk
;
BL
:
q
b
L
τ
L1k
s
L0k
E
L
t
L
F
LEd
;
1
for
F
Lk
;
BL
<
F
LEd
;
1
F
LEd
;
1
The following calculated variables are required to determine this component. First of
all, the effective bond length of the externally bonded reinforcement is calculated
according to DAfStb guideline part 1, RV 8.4.6 (RV 8.11), with the factor
κ
Lb
=
1.128:
r
E
L
?
t
L
?
s
L0k
τ
L1k
2
κ
Lb
?
l
bL
;
max
Using the boundary values of the bilinear bond stress-slip relationship
s
L0k
,
τ
L1k
according to DAfStb guideline part 1 annex RV K 1 and the associated long-term
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