Basic HTML Version
8
IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 1
RC T beams strengthened to shear with carbon fiber composites
same conditions as the beams. The ends of the cylinders were
grounded before the tests. The cylinders were cast simultaneously
with beams using the same batch concrete. The average value of
the compressive strength of the concrete for each test beam was
obtained from three 15
cm
x 30
cm
cylinder specimens. Table [2]
shows the concrete strength. All the specimens were tested in ac-
cordance with Brazilian standards. The average concrete secant
modulus is 25.01
GPa
, and the average splitting stress (Brazilian
test) is 4.08
MPa
.
The ordinary steel bars were ribbed bars with diameters of 5
mm
, 8
mm
, and 16
mm
. Tensile tests on three representative
specimens of each reinforcing bar type were conducted. The av-
erage values of the yield stress and yield strain were 596
MPa
and 0.30 % for 5
mm
diameter, and 600
MPa
and 0.20 % for 16
mm
diameter, respectively. The 8
mm
bars were not considered
in the design because this reinforcement was only a support for
the steel stirrups.
The CFC was tested in accordance with ASTM D3039/D3039M
([15]); CFC mechanical properties (mean values) was: tensile
strength 2969
MPa
, ultimate strain 11.6 %, modulus of elasticity
255.000
MPa
.
4.4 Test setup and loading procedures
All eight
T
reinforced concrete beams were tested on steel frames
with capacities of 500
kN
and 1000
kN
, fixed on the plate reactor
of the Laboratory of Structures of PUC‑Rio. The applied force was
measured using a load cell in series with an actuator. Beams were
loaded at two points with force control using a double action hydrau-
lic actuator located at the top of the supplementary steel beam.
The beams VR1 and VR2 were tested with a monotonic loading
until failure, and the beams VI-1, VI-2, VI-3, VII-1, VII-2, and VII-3
were loaded under sustained strain with a special apparatus after
bending cracking (after the first crack) and strengthening. They
were subsequently loaded monotonically until failure.
The load was applied in imposed deformation steps by a hydraulic
jack, and was controlled by load cells placed at the beam supports.
The load cell under the jack furnished the ultimate load
exp u,
P
.
Figure 8 – General view of strain gauge locations on steel stirrups and longitudinal bars of series II, distance
from support: section 1=0.15 cm, section 2=0.45 cm; section 5=middle and other sections are symmetric
Figure 9 – Strain gauge rosette locations on concrete surface
Beams VR1 and VR2
Beams VI-1, VI-2, VI-3, VII-1, VII-2 and VII-3
A
B