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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 4
M. R. GARCEZ | L. C. P. SILVA FILHO | URS MEIER
Figure [08] also shows that up to 100.000 cycles the behavior of
both strips is similar. However, some variations can be observed at
mid-span, due to the high cracking.
The strategy adopted to monitor the crack growing at mid-span
of beam VFC_PC_01 can be observed at Figure [09]. Results of
crack openings and the respective position from the left end of the
beam are shown in Figure [10].
A high concentration of cracks can be observed at the mid-span
of beam VFC_PC_01, between the four loading points. Figure [10]
shows the crack openings at mid-span between the two central
loading points (signaled on the figure by two vertical arrows). It
is noteworthy that, before 100.000 cycles, crack openings did not
reached 0,05mm.
The highest crack opening after 100.000 cycles, named D, was
0,4mm, located 254cm from the left side of the beam. However,
apparently the post-strengthening failed due to a 2,2mm crack
opening, named I, after 331.300 cycles. It is important to notice
that, after 100.000 cycles, this crack opening was about 0,3mm
(Figure [11]).
The decision of testing beam VFC_PC_01 under a high stress vari-
ation led to the fatigue failure before 5.000.000 cycles, that was
considered the pattern of infinite fatigue life. Stress levels applied
to the beam VFC_PC_02, however, are more consistent with the
ones usually found in real structures. Results of beamVFC_PC_02
will allow a more detailed analysis of the CFRP prestressing tech-
nique used, as well as of the gradual anchorage system.
4.2 Results of beam VFC_PC_02
Beam VFC_PC_02 was submitted to stress levels of 50% and 60%
Figure 9 – Cracks at mid-span of beam VFC_PC_01 after 100.000 cycles
Figure 10 – Cracks at mid-span of beam VFC_PC_01 after 100.000 cycles