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IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 1
Automation of the evaluation of bonded and unbonded prestressed concrete beams, according to brazilian
and french code specifications
Passive reinforcement tendons were distributed in 13 layers, as
shown in Figure 15, with a 2.5-cm cover. Table 6 presents the
characteristics of each passive reinforcement layer, including its
relative position, diameter, number of tendons, section, and date.
The bonded prestressing tendons have a straight section and are
distributed in three layers, as shown in Figure 16. Table 7 shows
the characteristics of location, diameter, number of bars, reinforce-
ment section, and prestressing date of each layer of the active
reinforcement. Initial stress value for the prestressing tendons was
152 kN/cm².
Table 8 presents the loading cases used for SLS evaluation. The
applied loading was calculated according to the load combination
required for service evaluation as determined in each norm. In
SLS-W evaluation, a distributed load of 18.4 kN/m (frequent com-
bination) was considered for the Brazilian norm and of 22.5 kN/m
(rare combination) for the French norm.
According to Table 8, the member was analyzed on day 28, con-
sidering prestressing only of the precast section I. The second load
case is applied on day 29, when the compression flange was add-
ed to the upper part of the section. Having the total section working
monolithically, the permanent loading portion (g) was added, cor-
responding to the non-reduced portion of the total structure load.
Between days 29 and 10,000, the effects of yield, shrinkage, and
relaxation on the total section were calculated. After the analysis
of structural behavior relative to time, the last loading portion was
added on day 10,000, corresponding to the reduced variable load
(q) along the element’s sections. Five load increments were esti-
mated for cases 1, 2, 3, and 5.
After SLS-W was evaluated according to the Brazilian and French
norms, results were analyzed in a post-processing stage. Input
Figure 14 – Definition of the cross-section modules
Figure 15 – Distribution of the passive
reinforcement in the cross-section
Table 6 – Characteristics of the passive reinforcement layers
Layer
Height (cm)
Number of bars
2
Area (cm )
Date (days)
Ø (mm)
1
2
3
4
5
6
7
8
9
10
11
12
13
4.5
20
30
50
70
85
100
120
135
140
145
145
160
4
2
2
2
2
2
2
2
2
2
6
4
2
19.63
1.01
1.01
1.01
1.01
1.01
1.01
1.01
1.01
1.01
12.06
4.91
1.57
28
28
28
28
28
28
28
28
28
28
28
28
29
25
8
8
8
8
8
8
8
8
8
16
12.5
10