Civil Engineering Reference
In-Depth Information
4.5.3 Determining the crack spacing
The crack spacing is required for the accurate bond analysis. This will be determined
here according to DAfStb guideline part 1, RV 6.1.1.3. To do this, it is first necessary to
determine the cracking moment of the cross-section with the help of the near-surface
tensile strength:
m
cr
κ
fl
?
f
ctm
;
surf
?
W
c
;
0
h
1000
160
1000
κ
fl
1
:
6
1
:
6
1
:
44
1
:
0
b
?
h
2
6
1000
?
160
2
6
27
?
10
6
mm
3
W
c
;
0
4
:
=
m
m
cr
1
:
44
?
2
:
1
?
4
:
27
12
:
91 kNm
=
m
We also require the mean bond stress in the reinforcing steel in order to calculate the
bond force per unit length. In doing so, the double bars of the R 443 mesh are multiplied
p
according to the DAfStb guideline:
by the factor
43
?
f
2
=
3
43
?
28
2
=
3
mm
2
f
bsm
κ
vb1
?
0
:
1
:
0
?
0
:
3
:
96 N
=
cm
p
?
6
X
n
443
F
bsm
n
s
;
i
?
ϕ
s
;
i
?
π
?
f
bsm
:
5
?
π
?
3
:
96
764
:
32 N
=
m
4
?
2
?
5
2
6
:
?
π=
i
1
Consequently, the cracking moment and the internal lever arm, which may be assumed
to be 0.9 times the static effective depth, can be used to calculate the transmission length
of the reinforcing steel:
m
cr
z
s
?
F
bsm
m
cr
0
:
9
?
d
s1
?
F
bsm
l
e
;
0
12
:
91
?
10
6
0
:
9
?
140
?
764
:
32
133
:
98 mm
According to the DAfStb guideline, the crack spacing is then 1.5 times the transmission
length of the reinforcing steel:
s
r
l
e
;
0
1
:
5
?
l
e
;
0
1
:
5
?
133
:
98
200
:
96 mm
4.5.4 Accurate analysis of concrete element between cracks
For this analysis, DAfStb guideline part 1, RV 6.1.1.3.6, which is described in Section
3.3.3.3 of this topic, requires veri
cation of every concrete element between cracks.
It must be ensured that the acting change in forceinthestripislessthantheadmissible
change in force in the strip at the concrete element between cracks.
Δ
F
LEd
Δ
F
LRd
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