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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 1
P. M. LAZZARI | A. CAMPOS FILHO | F. P. S. L. GASTAL | R. A. BARBIERI | R. C. SCHWINGEL
of a cross section is represented in Figure 8. This zone has
the same center of gravity as the prestressing reinforcements,
ensuring a minimal “c” protection cover. The value of cover “c”
corresponds to the highest value between the tendon duct di-
ameter and to the cover recommended for a specific class of
environmental aggressive conditions. According to the French
norm, this value corresponds to an environmental class equal to
3cm in weather-protected sites, 4cm in weather-exposed sites,
and 5cm in sites submitted to aggressive weather conditions
(Thonier, [12]).
The evaluation during service of crack width essentially consists in
the observation of passive and active reinforcement stress limits.
If the passive reinforcement stress is lower or equal to the low-
est value indicated in expression (15), and if active reinforcement
stress variation between decompression state and final loading is
below the limit value, which corresponds to 10% of maximal active
reinforcement breaking strength relative to fatigue (expression 16),
then the member is considered safe in terms of SLS-W. According
to Thonier [12], if CA-50 steel is used in the passive reinforcement,
Figure 7 – Flow chart of the routine verification
ULS (Brazilian code specification)
Table 3 – Verifications of Serviceability Limit State – French Code Specification (Thonier, [12])
Serviceability Limit State (SLS)
Load Combination
Partial
Prestressing
Limited
Prestressing
Full Prestressing
Rare load combination
Frequent load combination
Quasi-permanent load combination
Rare load combination
Frequent load combination
Rare load combination
SLS-W
SLS-W (concrete cover zone*)
SLS-D (concrete cover zone*)
SLS-F (f - concrete cover zone*; 1.5 f – others zones)
tj
tj
SLS-D (concrete cover zone*)
SLS-D
* Concrete cover zone: area of the section with a minimum protective concrete cover for active reinforcement.
Table 4 – Concrete allowable stresses – Serviceability Limit State – French Code Specification (Thonier, [12])
Compression
Full
Prestressing
Limited
Prestressing
Partial
Prestressing
Tension
Quasi-permanent load combination
Frequent load combination
Rare load combination
Construction phase
Quasi-permanent load combination
Frequent load combination
Rare load combination
Construction phase
0.5 f
ck
0.6 f
ck
0.6 f
ck
0.6 f
cj
0
1.5 f
tj
0
1.5 f
tj
f
tj
1.5 f
tj
0.7 f
tj
1.5 f
tj
0
0
0
0
0
0
0.7 f
tj
0.7 f
tj
0
-
-
-
-
-
-
-
Concrete cover zone
Others zones
Concrete cover zone
Others zones
Concrete cover zone
Others zones
Concrete cover zone
Others zones