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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 5
R. R. F. SANTOS | D. R. C. OLIVEIRA
possibility of extending the fatigue lifetime considering the current
value of concrete strength obtained from sclerometry and axial
compression tests on concrete testimonies.
6. Conclusions
After tests performed “in situ”, the taken concrete testimonies were
tested in laboratory and the results revealed that the concrete
compression strengths are much higher than those specified in the
project (18 MPa). Thus, the concrete of the current structure has
a degree of safety higher than that stipulated in the preparation of
structural design. The difference between the values for elasticity
modulus of concrete (referring to f
ck
stipulated in the project and
the result obtained in the tests) was also considered in the compu-
tational models to verify the bridge structure in relation to ultimate
limit states and serviceability limit states.
Based on direct observation of the state of the minerals, in the
investigation of the maintenance history, which directly reflects the
degree of reliability and integrity of the structure and of the theoreti-
cal models, it is concluded that at no studied point occurred cor-
rosion in the reinforcements nor CO
2
penetration into the concrete
layer corresponding to the coating. This indicates unfavorable con-
ditions for the advance of carbonation front provided by the envi-
ronment, giving a high reliability to the test results of sclerometry
which may be strongly affected by this phenomenon, once accord-
ing to the ACI 228R-89 (1989 ) [13] a carbonated surface layer
results in sclerometric indexes greater than those corresponding
to the inner layers of the structural element.
The sclerometry tests also revealed that resistance values do not
suffer large dispersions when comparing elements relatively dis-
tant along the structure, which reinforces the hypothesis concern-
ing “uniformity” in the strength of concrete. The pacometry tests
served to ensure compatibility between the existing and designed
reinforcements, but it is recommended to repeat the procedure on
a larger number of regions. The axial compression tests accord-
ing to NBR 5739 : 1994 and modulus of elasticity under the light
of NBR 8522 : 2003 converge with those obtained by sclerometry
and codes’ estimates, and the perceived differences are justified
by the different natures of the tests. The recommended values for
the strain corresponding to the maximum stress of concrete are
Figure �� � Fatigue lifetime analy�i� con�i�ering f from calculation memory
ck
also close to those observed experimentally. The characteristic
curve of the concrete, although atypical point modulus of elastic-
ity commensurate with analyzed codes’ estimates, however it is
recommended campaigns for removal of a greater number of con-
crete testimonies to increase the representation of the conclusions
related to the constitution of the bridge as a whole.
Regarding the fatigue results it was observed that the damage in
the elements of the cross section is low, except for the concrete of
the bottom surface of the section, which is very compressed due to
the concrete fibers are subject to considerable initial stresses (per-
manent loading) suffering large stress variations with the passage
of the moving loads. For the future loaded train, it was observed
that the element of greatest damage corresponded to the bottom
surface reinforcement and concrete of the studied cross section.
Because of this it is possible state that the OAE 50A shows no
fatigue problems.
7. Acknowledgements
The authors thank to company VALE, ITEGAM, FAPESPA and
CAPES for the financial support for this and other experimental
works carried out in Northern Brazil.
8. References
[01] CÁNOVAS, M. F. Pathology and therapy of the
reinforced concrete. São Paulo: Pini, 1998.
[02] CASCUDO, O. The control of reinforcement corrosion
in concrete: inspection and electrochemical
techniques. São Paulo: Pini, 1997.
[03] BRAZILIAN ASSOCIATION OF TECHNICAL
STANDARDS. NBR 6118: Design of concrete
structures. Rio de Janeiro, 1978.
[04] METHA, P. K. & MONTEIRO, P. J. M. Concrete:
microstructure, properties and materials. São Paulo:
Pini, 2008.
[05] EVANGELISTA, A. C. J. Concrete strength
evaluation using different non-destructive tests. (Ph.D.
Thesis). COPPE. Universidade Federal do Rio de
Janeiro, Brasil, 2002.