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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 5
Flexural strengthening of reinforced concrete beams with carbon fibers reinforced polymer (CFRP) sheet
bonded to a transition layer of high performance cement-based composite
This technique involves a process of previous retrofitting of beams
with a high performance composite based on Portland cement and
short steel fibers, intended to constitute the called transition layer.
After the performance of several steps of experimental and theo-
retical analysis, it can be concluded that the technique proposed
– even with the possibility of further improvements, as any other
technique – proved to be efficient both in the reconstitution of ten-
sile zone of RC beams and in the improvement of beam perfor-
mance as a whole, particularly in a more efficient exploration of the
resistance properties of strengthening with sheets of PRFC.
The research was not limited to simple testing and comparison of
strengthened and non-strengthened beams, but aimed to cover
several scientific foundations and evaluations that focused on the
problem in question. From the joint analysis of all results obtained,
it could be concluded that the intended objective was reached.
Finally, it is highlighted a synthesis of the partial conclusions and
complementary comments on each specific study produced:
the addition of steel microfibers to conventional fibers enhances the
contribution of the matrix to the composite resistance and the im-
provement in the mechanism of stress transfer from matrix to fibers;
with the matrix cracking, the stress transfer was facilitated by the
steel microfibers which, in large amount in the matrix, led to the
progress of cracking with the increase in the loading level;
the flexural strengthening of beams through the external bonding
of CFRP sheet to a transition layer constitutes an efficient strategy
with practical application in engineering;
despite of being analyzed, during the last experimental steps, for a
single case (beam V2C), it was demonstrated that the previous re-
constitution of tensile zone with a high performance cement-based
composite based on macro and microfibers of steel prevents the
rapid progression of a critical crack at the strengthening end and
delays the sheet premature detachment. In the presence of a ma-
terial with greater fracture strength in the tensile zone of the beam,
the cracks become more distributed and with small openings along
the strengthening extent.
besides the considerable increase in resistance, the bonding of
CFRP sheet to a transition layer leads to a significant increase of
beam stiffness in relation to a beam without transition layer.
7. Acknowledgements
We thank FAPESP and CAPES for financial support. We also
thank Maccaferri – Latin America for the production, under pur-
chase order, of steel microfibers.
8. References
[01] Juvandes L. Strengthening and rehabilitation of
concrete structures using composites materials.
Thesis, Porto University Engineering; 1999.
[02] Ferrari VJ. Flexural strengthening of reinforced
concrete beams with carbono fibers sheets. Thesis,
Federal University of Santa Catarina; 2002.
[03] Beber, AJ. (2003). Structural behavior of
strenghetened reinforced concrete beams with steel
fibers composites. Thesis, Porto Alegre. Tese, Federal
University of Rio Grande do Sul; 2003.
[04] FIB. Bond of reinforcement in concrete-state-of-the-art
report. Lauseanne. Bulletin 10. 2000.
[05] Ferrari VJ. Flexural strengthening of reinforced
concrete beams with carbon fibers reinforced
polymer sheet bonded to a transition layer of high
performance cement-based composite. Thesis,
University of Sao Paulo, School of engineering; 2007.
[06] Ferreira LET. About the fracture resistance concrete
and the steel fibers concrete. Thesis, University of
Sao Paulo; 2002.
[07] RILEM TC 162-TDF. Test and design methods for
steel fibre reinforced concrete. Bending test. Materials
and Structures, 2002a; 35, 579-582.
[08] RILEM TC 162-TDF. Test and design methods for
steel fibre reinforced concrete. Design of steel fibre
reinforced concrete using the s-w method: principles
and applications. Materials and Structures, 2002b; 35,
262-278.
[09] Ferrari, V.J; Hanai, J.B. Development and analysis
of high performance hybrid cement composites.
Ibracon Structures and Materials Journal, 2009;
3, 254-270.
[10] ACI.318M. Building code requirements for reinforced
concrete.1989
[11] DIANA – Finite Element Analysis – user’s manual
release 9.