Civil Engineering Reference
In-Depth Information
4.7 Serviceability limit state
Analyses of crack width and deformation are not carried out in this example. It is merely
verified that the necessary stresses are complied with. According to DAfStb guideline
part 1 section 7.2, described in Section 3.6 of this topic, the strains in the strip and the
reinforcing steel must be limited as follows for a rare load combination:
f
yk
E
s
500
200 000
2
:
5mm
=
m
ε
s
ε
L
2mm
=
m
Under a rare load combination, we get the following maximum moment at mid-span:
p
?
l
2
8
4
3
5
?
4
:
3
2
8
m
E
;
rare
27
:
74 kNm
=
m
The prestrains
ε
s1,0
=
0.75mm/m,
ε
c,0
=
0.21mm/m and
ε
L,0
=
0.88mm/m are calcu-
lated as explained in Section 4.3. The variables
ε
L
=
1.41mm/m and
ε
c
=
0.65mm/m
are determined iteratively via the following two conditions:
m
R
m
E
;
rare
F
s1
F
L
F
c
The strain in the reinforcing steel is then determined via the depth of the compression
zone:
ε
c
ε
c
ε
L
;
0
ε
L
?
d
L
0
:
65
x
41
?
160
35
:
46 mm
0
:
65
0
:
88
1
:
d
x
x
0
:
65
?
140
35
:
46
35
:
46
ε
s1
ε
c
?
1
:
93 mm
=
m
2
:
5mm
=
m
As the ultimate strains for the strip and the reinforcing steel are not exceeded, the design
is veri
ed.
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