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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
M. R. GARCEZ | L. C. P. SILVA FILHO | URS MEIER
reached. When the first strip debonded, the sudden release of the
pre-tensioning force caused a compressive failure at the CFRP, as
a secondary failure (Figure [03]).
The secondary failure occurred in a region that was damaged due
to the presence of the flexural crack showed in Figure [03], which
reached about 90% of the cross-section. Figure [04 (b)] shows
one of the CFRP strips after the failure of the post-strengthened
beam.
Flexural crack showed in Figure [03] induced the identification of a
steel rebar broken due to fatigue. After the test, the concrete was
removed from the bottom of the beam and all steel rebars were
inspected. Figure [05] confirms the existence of more steel rebars
broken also due to fatigue.
Figures [06] and [07] show strains in the concrete and in the CFRP
strips, obtained by deformeters, which gauge points were placed
of the yielding stress observed at beam VFC_PE_01, tested under
static loading. Maximum and minimum applied loads were, respec-
tively, 80kN and 40kN, which, added to the self weight, 28 kN,
resulted applied loads of 108kN and 68kN (66% and 42% of the
ultimate capacity of beam VFC_PE_01)
Aiming to produce the first cracks, beam VFC_PC_01 was first
pre-loaded up to108kN. Then, cyclic loading was applied at a fre-
quency of 4Hz.
When 282.000 cycles were reached, a crack of about 2,2mm
was observed, approximately at mid-span, reaching about 90%
of the cross-section. After 331 300 cycles the machine automati-
cally stopped, when the deflection limit was reached. It was not
observed any sign of apparent failure at the strips. Larger displace-
ment limits were settled and the test was restarted. However, the
post-strengthening failed before the maximum load of 108kN was
Figure 4 – Failure of post-strengthening strips: (a) Next to a flexural crack; (b) Distant from flexural cracks
A
B
Figure 5 – Fatigue failure of steel rebars
Figure 6 – CFRP and concrete strains of beam
VFC_PC_01, submitted to 108kN,
during pre-loading