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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 5
V. J. FERRARI | J. B. DE HANAI
strengthening assists the steel to resist to tensile stresses. For the
beam V1C the increase was of 48.4%. In the beam V2C the in-
crease reached 67,1%.
Regarding the ultimate load it is highlighted the beam V2C re-
sponse. A significant increment of 120% was observed in relation
to the control beam, while the beam V1C presented a limited in-
crement of 65.1%. Considering the strengthened RC beam, the
resistance capacity for the beam V2C was 33.2% higher.
4.3 Vertical displacements
In the Figure [12] are compared, through the load-deflection
curves (P-d), the behaviors for the beams V1A, V1C and V2C. It
was observed that until the load cracking the response of beams
is similar. After the concrete cracking, it is clear the increase of
stiffness in the strengthened beams in relation to the beam without
strengthening. It is emphasized the effect of the transition layer in
the responses of the beam V2C. Higher stiffness and load capacity
were verified for this beam, especially in relation to the beam of
reinforced concrete V1C.
In the beam V1A it is observed that any addition of load after
the yield of longitudinal reinforcement was obtained. As for the
strengthened beams, it is clearly observed an increase of load
after the longitudinal reinforcement yield. In this way, the largest
extension for the final stretch of the curve of beam V2C indicates
that the strengthening was more required in this beam than in the
beam V1C.
In the Table [6] is presented a comparison between the deflection
for beams in the middle of span for a load equal to 90% of the
failure load of the beam V1A. The values show that the strength-
ened beams were stiffer than the control beam. The deflection
of the beam V1A was 47% larger than the deflection of the beam
V1C. The beam V2C presented a deflection even less pronounced
than the beam without strengthening. The displacement of beam
V1A was 67% higher than the beam V2C. Therefore, the innova-
tion proposed in the present paper, retrofitting and strengthening
of beam tensile zone, is not only effective in terms of load capacity,
but also in terms of stiffness.
4.4 Stresses and strains
The strengthening response is evaluated through the distribu-
tion of specific strain throughout its extension. Associating the
strengthening geometric and mechanical properties to values of
strain it is possible to obtain a distribution of longitudinal and tan-
gential stresses along the strengthening. It is possible to calculate
Table � � �oads and failure modes of the beams
Beams
P (kN)
f
P (kN)
y
P (kN)
u
Failure mode
Increments (%)
P
f
P
y
P
u
V1A
21.01
79.80
89.27
Excessive deformation for
the longitudinal
reinforcement
-
-
-
V1C
25.16
118.45
147.37
Strengthening debonding
19.8
48.4
65.1
V2C
34.92
133.37
196.35
Strengthening debonding
through the cement
composite interface
66.2
67.1
120.0
Figure 12 � ��ad�de��e�ti�n �ur�es ��
the beams V1A, V1C and V2C
Ta�le � � Comparati�e of �eams �eflections
Beams
Deflection (mm)
Comparison
V1A
12.79
1.00
V1C
8.73
1.47
V2C
7.68
1.67