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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 3
M. R. GARCEZ | G. L. C. P. SILVA FILHO | URS MEIER
A gradual anchorage system was applied: after the cure of the ad-
hesive at the middle part of the beam, the prestressing force was
marginally reduced and the following areas were bonded. The force
was reduced further and the adjacent areas were bonded. This
procedure was repeated until there was no remaining prestressing
force at the ends of the strip. With the gradual reduction, the level of
prestress applied at the ends of the strip is very low or close to zero,
eliminating the need of additional anchorage systems.
The maximum prestressing force applied to prestress the strip was
60kN, at mid-span. Then, prestressing force was reduced, gradu-
ally, to 48kN, 36kN, 24kN, 12kN and, finally, zero, at the ends.
3.5 Test Procedure
Loading was applied according to a six point bending test scheme:
simple supported beam and four vertical loads, spaced by
12000mm, symmetrically applied along the 6000mm span.
Load was applied by two 100kN hydraulic jacks. During the tests, val-
ues of deflection at mid-span and specific strain at steel, concrete
and FRP were continuously recorded by a computer controlled data
acquisition system. Bending test setup is shown in Figure [8].
4. Results and discussion
4.1 Loads and failure modes
Table [3] shows that the flexural capacity of beam VFC_NP_01,
post-strengthened with two non-prestressed CFRP strips, in-
creased 27% when compared to the control beam. On the other
hand, post-strengthening of beam VFC_PE_01, two prestressed
Figure 8 – Bending test setup
Table 3 – Ultimate Loads and failure modes of post-strengthened beams tested under static loading
Beam
Post-strengthening
Ultimate load
Failure Mode
VT
-
100,14kN
Yielding of steel followed by
concrete crushing
VFC_NP_01
Two 1,2mm x 50mm
non-prestressed strips
127,25kN
Premature failure (peeling-off)
VFC_PE_01
Two 1,2mm x 50mm
prestressed strips
162,41kN
Premature failure (peeling-off)
Figure 9 – Beam VFC_NP_01: (a) During
test; (b) After premature failure of strips
A
B