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THE EFFECT OF GLASS FIBER REBAR REINFORCEMENT ON FLEXURAL BEHAVIOUR OF REINFORCED CONCRETE STRUCTURAL ELEMENTS

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In recent years, fiber reinforced polymers (FRP), a type of composite material formed by the incorporation of various fibers into polymeric resins, have also begun to be utilized or used in construction technology like in many other areas. One of the uses of FRP has been the duty of reinforcing steel in reinforced concrete. The advantages such as high rust resistance, high resistance to environmental conditions (due to material), being non-magnetic, high strength / weight ratio and easier transportation due to low weight cause the use of FRP bar reinforcement as reinforced concrete accomplice and an important research topic. As FRP materials, carbon, aramid, basalt and glass are among the widely used materials. In this study, flexural resistance of concrete elements reinforced with FRP bars were investigated under three-point bending load. C30 concrete was casted into molds with dimensions 100 mm x 100 mm x 500 mm, and 3 copies were casted for each types of FRP reinforcement rebar. The tops of the samples were covered with a wet linen cover and left in the mold for 24 hours. The samples taken from the mold were stored in the curing pool until the day of the bending test. The failure mode, flexural capacity, deflection, crack propagation and of the tested beams were investigated. In order to better understand the effect of glass FRP rebar reinforcement on the flexural behavior of concrete, the obtained test results were compared with the test results of the reference concrete. Test results showed that effective enhancement in flexural strength and ductility was demonstrated by fiber reinforced concrete beams with embedded FRP rebars.
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EGE UNIVERSITY, IZMIR, TURKEY
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THE EFFECT OF GLASS FIBER REBAR REINFORCEMENT ON
FLEXURAL BEHAVIOUR OF REINFORCED CONCRETE
STRUCTURAL ELEMENTS
Hakan SARIKAYA1, H Ersen BALCIOĞLU*2
1 Department of Civil Engineering, Faculty of Engineering, Uşak University, Turkey
2 Department of Mechanical Engineering, Faculty of Engineering, Uşak University, Turkey
ersen.balcioglu@usak.edu.tr
ABSTRACT
In recent years, fiber reinforced polymers (FRP), a type of composite material formed by
the incorporation of various fibers into polymeric resins, have also begun to be utilized or
used in construction technology like in many other areas. One of the uses of FRP has been
the duty of reinforcing steel in reinforced concrete. The advantages such as high rust
resistance, high resistance to environmental conditions (due to material), being non-
magnetic, high strength / weight ratio and easier transportation due to low weight cause the
use of FRP bar reinforcement as reinforced concrete accomplice and an important research
topic. As FRP materials, carbon, aramid, basalt and glass are among the widely used
materials. In this study, flexural resistance of concrete elements reinforced with FRP bars
were investigated under three-point bending load. C30 concrete was casted into molds with
dimensions 100 mm x 100 mm x 500 mm, and 3 copies were casted for each types of FRP
reinforcement rebar. The tops of the samples were covered with a wet linen cover and left
in the mold for 24 hours. The samples taken from the mold were stored in the curing pool
until the day of the bending test. The failure mode, flexural capacity, deflection, crack
propagation and of the tested beams were investigated. In order to better understand the
effect of glass FRP rebar reinforcement on the flexural behavior of concrete, the obtained
test results were compared with the test results of the reference concrete. Test results
showed that effective enhancement in flexural strength and ductility was demonstrated by
fiber reinforced concrete beams with embedded FRP rebars.
KEYWORDS: Reinforced concrete, glass fiber rebar, flexural behavior
1. INTRODUCTION
In recent years, alternative materials have been searched for steel and alloys, which
were used to reinforce concrete structures, due to their disadvantages such as weight and
low corrosion resistance and aging infrastructure. The major cause of deterioration of
reinforced concrete structures is corrosion of the reinforcing steel. This problem is a more
serious concern in terms of the structural integrity of reinforced concrete (RC) structures in
areas having saline and cold climatic properties.
The fiber-reinforced composite structures become an alternative material to
traditional building materials in many sectors, with the development of the polymer
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industry. Fiber reinforced polymer (FRP) composite materials are used in plane,
automotive and ship industries due to their superior mechanical strength, impact and
corrosion resistance. FRP bars, which is non-corrosive and chemically inert, can help
extend the lifecycle of reinforced concrete structures substantially, as well as reduce their
maintenance, repair, and replacement costs (Chidananda and Khadiranaikar 2017).
Nowadays, glass (GFRP), carbon (CRFP), aramid (ARFP), basalt (BFRP) fiber reinforced
rebars are used to reinforce concrete structures (Figure 1). Each type of FRP rebar has its
advantages and disadvantages in terms of its mechanical properties, durability properties,
and cost. Among the four, GFRP rebar have been extensively used as one-dimensional
reinforcement in concrete structures, such as bridge girders and decks due to its relatively
low cost with respect to CFRP, AFRP, and BFRP rebars. (Duic, Kenno, and Das 2018).
Figure 1. Fiber reinforced polymer rebar (a) glass, (b carbon), (c)aramid, and (d) basalt
The effectiveness of fiber-reinforced polymer (FRP) used as reinforcement in
concrete has been extensively investigated. Kasagani and Rao (Kasagani and Rao 2018)
have investigated the effect of fiber length coefficient, orientation coefficient and fiber
dispersion coefficient on the tensile strength of glass fiber reinforced concrete. The test
results showed that the tensile strength decreased as the fiber length increased, in spite of
that the deformation capacity of the structure increased as the fiber length increased. The
other finding obtained from results that strain hardening increased with increase in fiber
volume content and fiber length. Duic et al. (Duic, Kenno, and Das 2018) has been
evaluated performance of concrete beams reinforced with BFRP rebar under four point
bending load. According to test results, at a low reinforcement ratio, BFRP rebar
reinforced beams exhibited more flexural and shear cracking than counterpart steel rebar
reinforced concrete beams. Jabbar and Farid (Jabbar and Farid 2018) have investigated
mechanical characterizations of reinforced concrete with GFRP rebars and compared with
that of steel rebars. Test results showed that, the tensile strength of GFRP rebar was higher
than about 13% that the steel rebar, while tensile strain of GFRP is higher than steel about
58%. Anandaraj et al. (Anandaraj et al. 2018) have investigated structural distress in glass
fiber reinforced concrete containing marble and granite dusts exposed to tensile,
EGE UNIVERSITY, IZMIR, TURKEY
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compressive, and loadings and aggressive environments such as chloride ingress and acid
attack. They found the results of that 20% marble dust or granite dust as fine aggregate
replacement improved the strength characteristics of concrete. In addition, results showed
that 1% glass addition to concrete containing 20% marble dust as fine aggregate
replacement produced higher strength properties than the control concrete.
Ferrier et al. (Ferrier et al. 2015) noted that the use of FRP rebars with ultra-high-
performance fiber-reinforced concrete had the advantage to increase the tensile capacity of
the beam, leading to a higher ultimate capacity, and exhibited typical reinforced concrete
beam behavior in terms of concrete cracking and failure under tension or compression.
Yoo et al (Yoo, Banthia, and Yoon 2016) have studied the flexural behavior of fiber
reinforced concrete beams reinforced with GFRP rebars and hybrid reinforcements with
steel and GFRP rebars. The increase in the reinforcement ratio of GFRP rebars resulted in
the improvement of their flexural performances, including post-cracking stiffness, load
carrying capacity, and ductility or deformability. Congruently, Lau and Pam (Lau and Pam
2010) experimentally verified that the low ductility and large deflection of FRP bar-
reinforced concrete members are improved when hybrid reinforcements with steel rebars
are used. De Lorenzis et al. (De Lorenzis, Rizzo, and La Tegola 2002) studied to determine
the mechanism of bonding between FRP rebars and concrete and ın order to analyze the
most effective parameters on bond strength. Variables such as the type of FRP bar, the
properties of the material filling the ribs, anchorage length and rib size, were investigated.
Test results showed that fracture of concrete pull-out samples, in which FRP bars were
embed via epoxy, occurs at the epoxy-concrete interface, and average value of bond
strength at the epoxy-concrete interface decreases with increasing anchorage length and rib
size.
There are many studies in the literature that seek to answer the question whether
fiber reinforced composite rebars can be an alternative to traditional rebar materials. In this
study, the bending behaviors of C30 concrete beam reinforced with glass fiber reinforced
composite bars having different diameters were investigated. In this context, C30 concrete
was reinforced with GFRP reinforcement rebars with three different diameters such as
8mm, 14m and 16mm.Test results were evaluated in terms of damage mode, flexural
capacity and crack propagation under the three-point flexural load of the concrete beam.
Also, in order to better understand the effect of glass FRP rebar reinforcement on the
flexural behavior of concrete, the obtained test results were compared with the test results
of the reference concrete.
2. MATERIAL AND METHODS
Discrete from metallic materials, composite materials can be easily formed to
complex shape and contours and can be gained required strength to carry combined normal
and shear load by changing orientation. Therefore, composite structures have been used as
alternative materials instead of metallic materials in the constructions applications. A
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pultruded composite consists of reinforcing materials, a laminating resin that binds the
composite together, possibly a surfacing mat to improve the composite surface appearance,
chemical resistance and weather resistance, and a variety of ancillary materials such as
pigments to impart color, accelerators to cure the laminating resin, internal release agents,
and inert fillers (Balcıoğlu and Aktaş 2015). The used E-glass/vinylester pultruded
composite rebars having 8mm, 14mm, and 16mm diameter were produced in Pul-Tech
FRP composite company in Usak, Turkey. The fiber volume fraction and density of E-
glass/vinylester composite pultruded shafts were 65% and 1.82 g/cm3, respectively.
In this study, it is aimed to produce C30 concrete according to TS EN 206-1
standard by using normal aggregate in concrete compositions. C30 concretes, now
recognized as a standard in Europe, are very strong and increasingly used in constructions.
It is especially recommended to use it in the areas of earthquake areas. A square centimeter
is based on an average load of 300 kilograms. The constituent materials used in the
concrete for casting of beams were cement, fine aggregate, coarse aggregate, and water.
The concrete to be produced in the scope of the study is prepared in dry plastic
consistency. Accordingly, the mixture calculations were made maximum grain diameter of
16 mm on the basis of the unit volume weight method. Aggregate mixing ratios were taken
to be 40% thin (0-4 mm) and 60% thick (4-16 mm). Manufacturing of concrete samples
and flexural tests were performed at the Construction Laboratory of the Department of
Civil Engineering at Uşak University. In this study, concrete specimens were produced in 4
different forms and the diameters of FRP rebar used in the produced specimens are given
in Table 1. Series A was a reference concrete and series B was reinforced with GRFP rebar
with different diameter.
Table 1. FRP rebar diameters using for produced specimens
Code
Diameter
(mm)
A
-
B1
Ø8
B2
Ø14
B3
Ø16
Figure 2. The detail of mixing process
mixing
M
ixing
water
g
mixing
6
3
6
1
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Natural municipal water was used for mixing process. Natural river sand of
fineness modulus 2.32 was used as fine aggregate. Crushed stones having maximum
aggregate size of 20 mm was used as coarse aggregate. Mixing process was done with the
help of a vertical axis mixer. In order to determine the consistency of the semi-product
concrete, the amount of slump, concrete temperatures and unit volume weights were
measured by abrams' cone. After mixing mortar concrete was placed into mold having 100
mm x 100 mm x 500 mm dimension on the vibratory table, in three stages. At each stage,
the mortar was vibration by the vibratory table tool for 10 seconds. Mixing was carried out
for a total of 300 s (5 min), 30 s dry (coarse aggregate, fine aggregate, and binder), 90 s
(first one-minute water addition), 60 s rest and 120 s mixture (Figure 2).
Figure 3. Storing of the concrete samples in the cure pool along 28 days
Table 2. Chemical Properties of Cement and Aggregate Used in Concrete Mixtures
Composition
CEM I
42,5 R
( % )
Normal
Aggregate (%)
SiO2
20,02
2,75
Fe2O3
3,52
1,29
Al2O3
5,16
-
CaO
63,46
0,2
MgO
1,03
2,8
SO3
2,74
-
Loss of ignition
2,35
-
Five samples were produced for each concrete series. The samples were left in the
mold for 24 hours and they were finally extracted from the mold with the help of rubber
wedges. Then, concrete specimens extracting from mold were stored in the curing pool
until the 28th day when will the experiment performed (Figure 3). The chemical properties
of the cement and agglomerate used for concrete were given in Table 2.
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2.1. Three-Point Bending Tests
Destructive three-point bending tests were carried out according to TS EN 12390
standard. According to this test standard, the prism-shaped test specimens are subjected to
a bending moment by applying a load through the support (bottom) and loading (top)
cylinders (Figure 4). The largest load is recorded and the bending strength is calculated.
Figure 4. Three-point bending test setup
Bending device with 25-ton capacity was used in the construction laboratory of the
Department of Civil Engineering of the Engineering Faculty of Usak University for this
experiment. The concrete samples prepared for this purpose were removed from the cure
pool at the end of the 28th day and the excess water on the surfaces was cleaned by wiping
before being placed in the test machine. The loading speed 66 N/s was applied for bending
test. This value was calculated according to Equation 1 that is in the test standard to avoid
impact effect.
𝑹 = 𝟐𝒅𝟏𝒅𝟐
𝟐𝒔
𝟑𝑳 (1)
where R required loading speed (N/s), s, stress increase rate (MPa/s), L span length and d1,
d2 the cross section of the sample. S stress increase rate was taken as 0,04 MPa/s that as
expressed in the test standard. Thanks to the computer-controlled software of the device,
the load-displacement curves of the concrete specimens were obtained during the test. The
data obtained from the load-displacement curve were used in Equation 2 to calculate the
flexural strength values of each concrete beam.
𝝈𝑭=𝟑𝑭𝑳
𝟐𝒅𝟏𝒅𝟐
𝟐 (2)
Where 𝝈𝑭 flexural strength, F maximum load (damage load). Five repetitions were
made from each series of concrete beams and the average of the obtained flexural strength
was considered to be a mean flexural strength value.
EGE UNIVERSITY, IZMIR, TURKEY
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3. RESULTS AND DISCUSSION
In order to investigate the effect of the glass fiber rebar reinforcement on the
flexural behaviors of the concrete beam, 4 different concrete beams were produced in 2
different series. One of them is A series that is not reinforced. B is a series which were
reinforced with glass fiber reinforced composite rebars having different diameters. Load-
displacement graphs generated on the computer during the experiment and damages on the
sample were followed. The displacement value is measured from the mid-zone of the
beam. The load-displacement curves obtained from three-point bending tests of series A
and B are shown in Figure 5.
(a)
(b)
(c)
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(d)
Figure 5. Load-displacement curve of series (a) A, (b) B1, (c) B2, and (d) B3
The first cracking in the A series concrete beam (reference concrete beam) started
at the range of 3-3,5kN. The capillary cutting cracks were formed at the load level of 4,5-5
N. An increase in the width of these cracks was observed with increasing load. The
maximum load on the beam is 5,8kN and the displacement corresponding to this load is
obtained as 1,5-2,5 mm. The load began to fall rapidly with the expansion of the cracks,
which occurred as a result of shear cracking. Figure 6 showed the state of the reference
concrete beam after it has been cracked.
Figure 6. Cracking of reference concrete beam (A series)
The three-point bending strength of reinforced concrete beams with glass fiber
rebar varies according to the diameter of the rebars. The flexural strength of the concrete
beam increased as the diameter of the rebar increased as shown in Figure 7. Concrete
beams, which were reinforced rebar having 8 mm diameter, carry average load of 16.5kN,
while beams reinforced with rebar with a diameter of 16 mm carry average of 36kN loads.
The flexural strengths calculated according to Equation 6 were given in Table 3 together
with standard deviations. The average maximum flexural strength of 21.61 MPa was found
from concrete beams reinforced with glass fiber rebar having 16 mm diameter. The
average minimum flexural strength of 3.19 MPa was obtained from unreinforced concrete
EGE UNIVERSITY, IZMIR, TURKEY
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beams. According to the obtained results, reinforcing of concrete beams with glass fiber
composite rebar increased the flexural strength up to 577%.
Table 3. Flexural strength of concrete beams with and without reinforced
Repetition Num.
A
B1
B2
B3
1
2,91
10,21
19,41
22,23
2
3,25
9,83
20,56
21,45
3
3,41
8,97
19,03
21,16
Average
3,19
9,67
19,67
21,61
Std. Dev.
0,21
0,52
0,65
0,45
Damage forms of reinforced concrete beams with glass fiber composite rebar were
given in Figure 7. Despite the fact that the reinforced concrete beam is completely broken,
the structural form of the beam is not collapsed thanks to the glass fiber reinforcement. All
of the damage occurred on the concrete structure in the performed flexural tests
Figure 7. Cracking of reinforced concrete beams (Series B)
4. CONCLUSION
In order to struggle the corrosion of the rebar, it is think of that the use of stainless
GRFP rebar instead of steel rebar, which is one of the two materials forming the concrete,
in the new constructions can be a suitable solution. It is thought that the use of composite
rebar with high tensile strength is considered ideal for structures subjected to severe
weather conditions in areas with high corrosion risk. Although composite rebars are more
expensive than conventional steel rebar, potential savings in maintenance costs make
composite equipment a viable alternative.
Despite of the fact that the advantages of the GRFP rebars such as low weight, high
strength, easy formalizing, corrosion resistance, high fatigue resistance, low thermal
conductivity and lack of magnetic permeability, they have some disadvantages such as the
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strength of the composite structure changes depending on fiber orientation, adherence
problem and costly. Moreover, since the values of the damage deformations of composite
rebar are very small, this situation can be a problem in the calculation of the reinforced
concrete section according to the transport strength method.
As a result of the experiments, glass fiber reinforced composite rebars have been
found as suitable for use in reinforced concrete structures. The reason of that is no
permanent deformation or damage did not observe on the GRFP composite rebar as a result
of the loading. If the adherence problem with concrete is eliminated and higher adhesion
strength is achieved, higher strength values can be achieved than the obtained data.
Composite reinforcement rebars are sandblasted, ribbed, etc. solutions can be applied to
eliminate the problem of adherence. Also, the increase in the diameter of the GRFP
composite rebars used as reinforcements increased the strength of the concrete beam.
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... FRP is a composite material (such as carbon, aramid, steel, basalt, and glass) that is formed by incorporating different fibers into polymeric resins [19,20]. It is highly resistant to corrosion and chemical attack, with a high strength-to-weight ratio [21]. In terms of structural application and design, serviceability criteria are often used as deciding factors in designing FRP-reinforced concrete sections, as FRP generally has a low modulus of elasticity and high tensile strength without a yielding point [22]. ...
... For instance, Elgabbas et al. [29] observed that the cracking moment of BFRP beams, by applying the bending test until failure, was less than the values predicted by the ACI 440.1R [30] and CAN/CSA-S806 [31] equations. The failure modes of FRP beams are either concrete crushing in the compression zone or rupture of the FRP itself [21]. El Refai and Abed [28] tested the shear strength of BFRP beams without shear reinforcement, and observed that the behavior of BFRP-or GFRP-reinforced beams was quite similar. ...
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Effective blending of short length and long length fibers in concrete is termed as Graded fiber reinforced concrete. Earlier research shows that short length fibers primarily control the propagation of micro cracks, and improve the ultimate strength whereas, long length fibers arrest the macro cracks and improve the post crack deformation of concrete. Thus different combinations of short and long length fibers would help in arresting the micro and as well as macro cracks to improve both pre and post crack performances of concrete. An attempt has been made to study the effect of addition of Graded Glass Fibers with different fiber length and volume fraction in Glass Fiber Reinforced Concrete. The experimental work was carried out under uni-axial tension for M30 grade of concrete with the 0.1%, 0.2%, 0.3%, 0.4% & 0.50% fiber volume of Mono Glass Fibers (3 mm, 6 mm, 12 mm and 20 mm length fiber). In 0.3% fiber volume, different fiber volume combination of Glass fibers in Short Graded form (3 mm + 6 mm length fiber), combination of Glass fibers in Long Graded form (12 mm + 20 mm length fiber) and combination of Short Graded + Long Graded fibers to form Combined Graded fibers (3 mm + 6 mm + 12 mm + 20 mm length fiber) were studied. The results shows that the strength, deformation capacity and energy absorption capacity is higher for Graded Glass Fiber Reinforced concrete than Mono Glass Fiber Reinforced Concrete. Graded fibers improved the workability. Fiber efficiency characteristics (Fiber length, Fiber dispersion, fiber orientation) were quantified to investigate their effect on the tensile strength of Glass Fiber Reinforced Concrete (GFRC). For this purpose, optical microscopic study and an image analysis technique is used to examine the failed specimens of GFRC. The results of image analysis shows that the strength of fiber reinforced composite are dependent on the fiber efficiency characteristics.
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Using industrial and construction rejects as alternatives to conventional materials is becoming the most attractive option for ensuring sustainability in concrete production. This experimental study investigates structural distress in glass fibre-reinforced concrete containing marble and granite dusts exposed to various loadings and aggressive environments. The properties of concrete determined includes mechanical – compressive strength, split-tensile strength, flexural strength, and durability – chloride ingress and acid attack. A preliminary investigation showed that 20% marble dust or granite dust as fine aggregate replacement improved the strength characteristics of concrete. Then, further investigation has shown that 1% glass addition to concrete containing 20% marble dust as fine aggregate replacement produced higher strength properties than the control concrete. Concrete elements produced with glass fibre, marble and granite dust as described in this study are expected to have a prolong service life when subjected to a severe environmental condition.
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Basalt fibre reinforced polymer (BFRP) rebar is an emerging green construction material. In this research, performance of concrete beams reinforced with BFRP rebar has been evaluated. Full-scale tests on eight large-scale concrete beam specimens reinforced with either BFRP rebars or steel rebars were undertaken. The test data were analysed to evaluate the performance of BFRP rebar reinforced concrete beams in shear and flexure. It was found that at a low reinforcement ratio, BFRP rebar reinforced beams exhibited more flexural and shear cracking than counterpart steel rebar reinforced concrete beams. It was also found that BFRP reinforced beams exhibited acceptable deformability according to CSA S6-14. Cracking moments were found to be 30–50% higher for steel rebar reinforced specimens, compared to BFRP rebar reinforced specimens. The study also found that shear failure can govern the design of BFRP rebar reinforced concrete beams containing BFRP stirrups, and that Vc is 30–40% less for BFRP reinforced beams. The CSA S806-12 standard was found to be conservative in predicting Vc. However, ACI 440.1-15 standard was found to be unconservative, but in some cases accurately predicted Vc.
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This study describes the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with glass fiber-reinforced polymer (GFRP) rebars and hybrid reinforcements (steel + GFRP rebars). Three GFRP bar-reinforced beams and four hybrid reinforced beams with different reinforcement ratios were fabricated and tested. Owing to the strain-hardening characteristics of UHPFRC, all test beams exhibited very stiff load-deflection behavior after the formation of cracks and satisfied the service crack width criteria of CAN/CSA S806. In addition, deformability factors higher than the lower limit of CAN/CSA-S6 were obtained for all test beams. The increase in the reinforcement ratio of GFRP rebars resulted in the improvement of their flexural performances, including post-cracking stiffness, load carrying capacity, and ductility (or deformability). The use of hybrid reinforcements by replacing a part of a GFRP rebar with a steel rebar contributed to a higher post-cracking stiffness before steel yielding, but led to lower deformability. Based on a sectional analysis, both AFGC/SETRA and JSCE recommendations were appropriate for predicting the moment-curvature response of UHPFRC beams with GFRP rebars and hybrid reinforcements: the average ratios of the maximum moments obtained from experiments and numerical analyses were found to be 1.12 and 0.94, respectively.
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The primary objective of this research was to develop a new type of high-performance lightweight beam providing better performance than conventional beams made of timber, steel or reinforced concrete (RC) by casting fibre-reinforced polymer (FRP) reinforcing bars (rebars) in ultra-high-performance concrete with short fibre reinforcement (UHPC–SFR). This new type of beam was developed to be lightweight, have high compressive and tensile strength, be able to sustain large bending moments and be resistant to shear. The main objective was to verify the mechanical behaviour of the beams and compare it with typical RC beam behaviour. For this purpose, an experimental program was designed to identify the failure modes and bending behaviour. The results indicate that the behaviour of such RC beams can be compared to typical RC beam behaviour to a certain extent. A model to validate this concept is presented in this paper; this analytical model is based on typical material law behaviour hypotheses of beam nonlinear mechanical behaviour. The load–displacement and moment–curvature relationships predicted with this model were compared to the experimental results obtained for four large-scale specimens. The comparisons revealed good correlation between the analytical and experimental results and illustrate the potential of these composite beam configurations in civil engineering structures.
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Fiber-reinforced polymer (FRP) has become a practical alternative construction material for replacing steel bars as reinforcement in concrete structures. However, the brittleness of FRP greatly reduces the ductility of FRP-reinforced concrete (FRPRC) beams. In order to improve its flexural ductility, and at the same time retain the high strength feature of the FRP bars, it is proposed that steel longitudinal reinforcement should be added to form a hybrid FRPRC beam. Twelve specimens consisting of plain concrete beams, steel-reinforced concrete (SRC) beams, pure FRPRC beams and hybrid FRPRC beams were fabricated and tested. The test results show the hybrid FRPRC beams behave in a more ductile manner when compared with the pure FRPRC beams. Also, it is observed that a higher degree of over-reinforcement in the beam specimen resulted in a more ductile FRPRC beams. Hence, the addition of steel reinforcement can improve the flexural ductility of FRPRC members, and over-reinforcement is a preferred approach in the design of FRPRC members.
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Among the strengthening techniques based on fiber-reinforced polymer (FRP) composites, the use of near-surface mounted (NSM) FRP rods is emerging as a promising technology for increasing flexural and shear strength of deficient concrete, masonry and timber members. In order for this technique to perform effectively, bond between the NSM reinforcement and the substrate material is a critical issue. Aim of this project was to investigate the mechanics of bond between NSM FRP rods and concrete, and to analyze the influence of the most critical parameters on the bond performance. Following up to previous investigations, a different type of specimen was designed in order to obtain a test procedure as efficient and reliable as possible. Among the investigated variables were: type of FRP rod (material and surface pattern), groove-filling material, bonded length, and groove size. Results of the first phase of the project are presented and discussed in this paper.
Flexural Behaviour of Concrete Beams Reinforced With GFRP Rebars
  • S H Chidananda
  • R B Khadiranaikar
Chidananda, S. H., and R. B. Khadiranaikar. 2017. "Flexural Behaviour of Concrete Beams Reinforced With GFRP Rebars." International Journal of Advance Research, Ideas and Innovations in Technology.