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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 1
Steel fiber reinforced concrete pipes. Part 1: technological analysis of the mechanical behavior
the displacements of 1.2 mm and 3 mm, for the first and 2
nd
Series
respectively. It is possible to observe clearly that the fibers content
interferes in both parameters. The linear regression between fiber
content and ultimate load or post-cracking load provide good level
of correlations, as shown by the coefficients of correlation. Thus,
this type of curves can be used in a mix-design procedure, if the
variability of the test is well known. However, the fiber mix-design
in order to accomplish a required post-peak residual strength has
a greater relevance when the Brazilian standard [2] is used for
pipes control.
4. Final remarks
The performance demonstrated by the FRCP was higher than
the presented by the SBRCP when they were submitted to low-
er levels of displacement and cracking. A similar behavior has
been observed in previous studies [9]. This fact occurs because
the fibers are mobilized early in the process of cracking due to
their position along the wall surface of the component. Since
the steel bars are eventually being placed along the neutral
line, by the requirement of minimum coverage, it will demand
a high level of displacement and cracking in order to mobilize
their resistance. So, the behavior of FRCP with low contents of
fiber is typically softening, while the pipes with rebars present a
typical hardening behavior. Thus, even for low fiber consump-
tions, the performance of FRCP is comparable or even superior
to SBRCP at low cracking and displacement level. This is par-
ticularly interesting since this is the stage of primary interest to
the component application because the pipes are still in good
conditions to meet the durability requirements. Moreover, in the
particular case of this experimental study, the SBRCP had much
better performance than the prescribed class. It also indicates
that the fiber reinforcement is so efficient that approximates
the behavior of FRCP to the one presented by a higher class
SBRCP at the serviceability conditions.
It has been shown that the fiber content affects equally the ultimate
load as the post-peak maximum load presented by the pipe in the
crushing strength test. For this reason, it is important to take into
account the contribution of the fiber in mix design analysis of the
FRCP concerning to meeting the requirements of the ultimate and
maximum post-peak load.
The results also confirmed the critical condition related to the
spigot displacement in relation to the socket area. This fact
shows that the component displacement measured at this po-
sition could be associated to the more demanding pipe condi-
tion in terms of displacement and crack initiation. However, this
is a conservative approach concerning only to the test method,
since the spigot will be protected by the follow pipe socket during
use. This effect, however, is not applicable to pipes where the
socket has no enlargement [2] [4]. Thus, the crushing test carried
out in pipes which diametrical displacement is measured only at
the spigot is very much in favor of security. Furthermore, this ar-
rangement test proved to be much more suitable to evaluate the
pipes performance. This occurs because, for pipes with higher
fiber consumptions, it would not be possible to verify when the
load drops to 95% of its value at low level of displacement. In
that situation, the technician in charged to run the test could not
observe the right moment to impose the end of the first cycle and
start up the second one.
5. Acknowledgements
The authors of this paper wish to express their appreciation for
the support received from Fermix Indústria e Comércio Ltda. and
Belgo Bekaert Arames that turns possible the entire experimental
work.
Likewise, Professor Antonio D. de Figueiredo wishes to thank the
support provided by CAPES -Coordenação de Aperfeiçoamento
de Pessoal de Nível Superior– for having awarded him the post-
doctoral grant that allowed him to participate in this work.
6. References
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