5 th International Conference on Advanced Composite
Materials in Bridges and Structures (ACMBS-V)
Winnipeg, Manitoba, Canada / September 22 – 24, 2008
AN INVESTIGATION OF POSSIBILITY FOR REPLACEMENT
OF REINFORCED CONCRETE BEAM'S STEEL
REINFORCEMENT WITH CARBON BARS AND POSTSTRENGTHENING WITH CARBON FRP LAMINATES
Emad Abdulahad
University of Architecture, Civil Engineering and
Geodesy, Sofia, Bulgaria, Europe
Dimitar Panichkov
University of Architecture, Civil Engineering and
Geodesy, Sofia, Bulgaria, Europe
Fantina Rangelova
Transportation University VTU “Todor Kableshkov”,
Sofia, Bulgaria, Europe, fantina_fce@uacg.bg
Abstract
On January 2007 Bulgaria become a part of Europe Union, and regarding to this very big projects on infrastructure
development have been started. This paper presents its authors’ efforts to meet the needs, and to try to suggest
adequate and advanced solutions in this infrastructure development. This kind of research gives answers as for
building of new engineering structures, as well as for rehabilitation and strengthening of the old one. The problem
with corrosion and finding alternative of this problem is one of the reasons to prepare and implement experimental
research of replacement of conventional steel reinforcement with Carbon FRP bars in newly building of reinforced
concrete beams, as a general element of infrastructure structures. Strengthening with Carbon FRP laminates
presumes a lot of advantages and it is one unstudied field in Bulgarian civil engineering practice.
INTRODUCTION
In the last few years the investigation of Bulgarian Building Fund demonstrates necessity of application of advanced
solutions for design, rehabilitation and strengthening. Regarding to these necessities an experimental investigation is
prepared and is implemented in the Structural laboratory at the University of Architecture, Civil Engineering and
Geodesy (UACG), Sofia, Bulgaria, Europe. The general goal is to be examined the opportunity of application of the
Advanced FRP reinforcement.
TEST SET UP
Two beams were prepared for experimental investigation. One of them is with traditional steel reinforcement, and
other is with carbon fiber reinforcement. The beams were tested of flexure. The experiment was implemented in two
stages:
 First stage: Experimental investigation of unstrengthened beams, and
 Second stage: Experimental investigation of strengthened beams.
The goal of this research is to investigate the effects of the Carbon FRP reinforcement, its bearing capacity, and its
failure mechanisms.
Figure 1 and Figure 2: Test specimens - Beams specimens with Steel and Carbon Reinforcement
Where:
(1) For beam with Carbon Reinforcement – Carbon 2N22 with Ac = 2 x 3,801 = 7,602 cm2;
(1) For beam with Steel Reinforcement AIII – 2N22 with As = 2 x 3,801 = 7,602 cm2;
(2) Assembled Reinforcement;
(3) Transverse Reinforcement Φ8/20;
(4) Steel plates 12,5/25/6 cm;
(5) Steel plates 12,5/25/6 cm;
(4) and (5) are for beams support.
Note:
AIII with Rs = 37,5 kN/ cm2 – calculated strength of the Steel;
Carbon with Rc = 180 kN/ cm2 – calculated strength of Concrete of ressure;
Rbt = 0,09 kN/ cm2 – calculated strength of Concrete of tension.
The test specimens were loading in center (support dimension is 180 cm) with fixed load by the steps F = 30, 60, 90,
105, 120, 135, 150 kN.
Figure 3: Test set up
Figure 4: Test measuring
Figure 5: Test specimen
TEST RESULTS OF THE FIRST STAGE OF THE EXPERIMENTAL WORK
From Fig. 6: The deflections of the beam with carbon reinforcement are 3,5 times more than the deflections of the
beam with steel reinforcement.
The first cracks in the beam with steel reinforcement are appearing by 90 kN, and in the beam with carbon
reinforcement by 60 kN.
From Fig. 7: The difference between the relative deformations in the steel and carbon reinforcement is 3 times (the
bigger value is by the carbon).
From Fig. 8: The relative deformations of the concrete in the pressure zone of the two beams are close; In the
tension zone they are 3 times bigger for the carbon rebars.
CONCLUTIONS FROM THE FIRST STAGE OF THE EXPERIMETAL WORK
1.
2.
3.
4.
5.
The effectiveness of the carbon reinforcement is not realized by little lengths of the beam specimen;
The carbon rebars create more powerful and clear effect of stress in comparison with the steel rebars;
The bond between the concrete and carbon rebars is less than the bond between the concrete and the steel
rebars;
The anchor length of the carbon rebars depends from the geometrical length of the beam, the class of the
concrete and from the strains in these rebars;
The results show that the effective application of the carbon rebars is useful for prestressed construction.
SECOND STAGE OF EXPERIMENTAL INVESTIGATION – STRENGTHENING BEAMS
WITH CARBON TAPE, APPLIED ON THE TENSION ZONE OF THE BEAMS
The beams were strengthened with MEGAPLATE HM-250 (Isomat) with dimensions 50 mm x 1,2 mm; Tensile
Strength ffk (MPa) = 2 000; Efk (GPa) = 245; and EPOMAX-PL with Tensile Strength = 41 MPa; Strength of
Pressure = 70 MPa; E (flexure) = 6,40 MPa. The tapes were affixed to the beams on its two ends by MEGAWRAP
– 2000 with ffk (MPa) = 3,800; Efk (GPa) = 235, as shown on the pictures:
The strengthened beams were loading with the same loads: 30, 60, 90, 105, 120, 135 and 150 kN:
TEST RESULTS OF THE SECOND STAGE OF THE EXPERIMENTAL WORK
Beams with steel reinforcement
Experimental investigation was implemented of reinforced concrete beams, reinforced with steel reinforcement AIII
and reached a stage III of failure; and after that strengthened with carbon tapes. The results show:
From Figure 9: The deflections are smaller with 20 %;
From Figure 10: The relative on the tensile reinforcement are smaller with approximately 20 to 30 %;
From Figure 11: The relative deformations of the concrete on the tensile zone are smaller with approximately 30%.
Beams with carbon reinforcement
For this specific investigation of concrete beams reinforced with carbon rebars by preliminary loading so early is
reached the stage III. After that the beam is strengthened with carbon rapes and is received the following results:
From Figures 12, 13 and 14: As results after the implemented beams’ strengthening by the repeated loading, the
deflections, the relative deformations in the concrete on the tension zone and the relative deformation in the carbon
rebars decrease with 50%:
CONCLUTIONS FROM THE SECOND STAGE OF THE EXPERIMETAL WORK
Beams with steel reinforcement:
1.
2.
The strengthening of the reinforced concrete beams reached the stage III of failure is effective to be
implemented with Carbon FRP as preliminary received cracks have to be filled and have to be rehabilitated
the continuous of the structure of the element. This kind of strengthening method could to be useful
solution by accidents.
When the increasing of the bearing capacity of the elements is necessary by assumption of bigger loads,
this kind of strengthening will be useful.
Beams with carbon reinforcement:
1.
The reason for these kinds of results is that the carbon tape begins their “work” on the first stage of loading.
Explanation of that is the high strength of the carbon tapes, the good bond between the concrete, the epoxy
resin and the carbon tapes.
REFERENCES
1.
2.
3.
4.
5.
L. Wyllie, Use of Composite Materials in Civil Infrastructure (2000)
Panichkov, D., “Application of the constructive glass-plastics in the physical structural modeling”
Rangelova, F. (2004) : “FRP system’s kind by the strengthening and rehabilitation of the civil engineering
structures”, DCB 2004, pp. 250-256
Abdulahad E., Rangelova F., Panichkov D., “FRP reinforcement for concrete beams – an experimental
investigation”, 8 th International Symposium on FRPRCS, University of Patras, Patras, Greece, 16 – 18 July,
2007
Fyfe & Co, Technical notes of TYFO FRP Strengthening Systems