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S. Marvel Dharma
PG Student, Dept. of Civil Engineering
EBET Group of Institutions,
Tirupur, India
Abstract- The Strength of conventional reinforced
concrete gets progressively reduced due to the
degradation of the steel bars. GFRP bars being high
strength, low self-weight and non-corrodable
remains to be the better replacement for steel bars.
The behaviour of GFRP-RC members and Steel-RC
members tends to vary. This paper gives a review on
the researches carried out on the performance of
GFRP rebars. Low elasticity modulus and brittle
nature reduces the ductility of the GFRP-RC beams.
The steel fibres and the steel longitudinal
reinforcement are added as a measure to improve
the ductility of the members. The members are to be
preferably designed as over reinforced as per ACI
440 1R-06 and deflection predicting equations are
validated.
Key words: GFRP, Beams, ACI, Ductility, Codal
provisions.
I. INTRODUCTION
Steel rebars have been the reinforcing medium in
concrete structures for decades. Their performance
dips when exposed to aggressive environments such
as coastal and marine structures, bridges, chemical
plants and wastewater treatment facilities. The
corrosion problem has been the major concern in the
structural deterioration. Several measures have been
taken to overcome corrosion problems in steel
reinforcement such as use of admixtures, coated steel
rebars etc. Among these measures, for the past few
years there has been an increase in the use of
alternative reinforcing materials for concrete in harsh
environments. The recent advancements in
composites have led to the development of Fibre-
Reinforced Polymer (FRP) rebars that possess the
strength and corrosion resistance properties than that
of steel.
The Fibre Reinforced Polymer (FRP) material
promises to be a better alternative for steel as
reinforcing medium. They are made of fibers
S. Yamini Roja
Assistant Professor, Dept. of Civil Engineering
Sri Ramakrishna Institute Of Technology,
Coimbatore, India.
reinforced in polymers. High tensile strength, light
weight and non-corroding nature are its advantages.
Glass Fibre Reinforced Polymer (GFRP) Carbon
Fibre Reinforced Polymer (CFRP), Basalt Fibre
Reinforced Polymer (BFRP) and Aramid Fibre
Reinforced Polymer (AFRP) comes under the types
of FRP’’s. Among these, GFRP is effective in
structural applications. These rebars are reinforced
by fine fibres of glass. Resistance to chemical attack
and electromagnetic neutrality are some of its other
advantages. However, their effective use in
reinforced concrete has been very limited due to lack
of research and design specifications. Poor ductility
is one of the considerable disadvantages of GFRP
rebar.
II. PROBLEM STATEMENT
The behaviour of concrete beams reinforced with
FRPbars (FRP-RC) is different from conventional
RC beams due to the differences between the
physicaland mechanical properties of FRP and steel
reinforcements. Owing to the lower modulus of
elasticity the FRP-RC beams exhibit lower
serviceability performance compared to steel bars.
The rigid and brittle behaviour of FRP bars forces the
FRP-RC beams to be designed as over-reinforced
making the failure by crushing of concrete. The
surface textures and mechanical features of FRP bars
are different from steel bars and thus the bond
behaviour is a major concern in FRP—RC members.
The bond between the FRP bars and the concrete is
affected by various factors. Limited experimental
researches exist for FRP reinforced concrete deep
beams. Shear behaviour of them is not clear and the
shear capacity of deep beams is a major issue in their
design. Being a composite material their surface
seems to be weaker than that of steel bars. The linear
elastic brittle behavior of FRP bars results poor
ductility in the flexural behavior of FRP-reinforced
concrete beams. Due to the linear elastic properties of
the FRP bars up to failure, the conventional ductility
REVIEW ON BEHAVIOUR OF GLASS
FIBRE REINFORCED POLYMER RC
MEMBERS
behaviour of steel reinforced structures is far better to
the structures reinforced with FRP rebars.
III. REVIEW OF LITERATURES
Benmokrane et al.[1] carried out an experimental
study on the Flexural behaviour of the concrete
beams reinforced with glass fibre reinforced polymer
(GFRP) rebars. The properties of GFRP and its
components are presented. To make use of GFRP
rebars possible, an appropriate reinforcement ratio
not greater than 2% and lower span-to-depth ratio is
preferred since when this ratio is low, the ratio
between deflections of GFRP and deflections of Steel
rebars is low. Alsayed. S. H et al.[2] investigated the
validity of ACI-318 code of practice for both strength
and serviceability requirements for designing
concrete beams reinforced with GFRP reabrs. Two
simple empirical models are suggested to predict the
actual service load and deflection. A model to
estimate the minimum required reinforcement ratio is
also suggested. Abdalla. H. A.[3] has evaluated the
deflection in concrete members reinforced with FRP
bars. Simple approach to estimate the deflection of
FRP RC members by testing under short term static
load is developed. Various deflection prediction
models are validated. HoussamToutanji and Yong
Deng [4] verified the ACI 440 methods for predicting
the deflections and crack width of RC members
reinforced with glass FRP rods. ACI 440.1R-01 is
effective in predicting beams with one-layer FRP
bars and underestimates two-layer FRP bars. For
Two-layer FRP bars, kb value is suggested from 1.2
to 1.4 for accurate predictions. Weigan and Abdalla
[5] evaluated the effect of the low modulus of
elasticity and the non-yielding characteristics on the
shear capacity of RC members reinforced with FRP
rods. A simple expression for the shear capacity of
FRP-RC is developed. Shear strength of beams
reinforced with FRP rods is significantly lower
comparing to the beams reinforced with steel due to
reduced compression stress block and the cracking
nature of FRP rods. The analytical proposed method
was also examined by experimental results. Ashour
[6] investigated the flexural and shear capacities of
RC beams reinforced with GFRP bars. Two modes of
failure, Flexural failure due to tensile rupture of bars
in under reinforced sections and Shear failure
initiated by diagonal cracks in over reinforced
sections were observed. Methods to predict shear
capacity were examined. Biswarup et al.[7] studied
the strength and serviceability performance of GFRP
reinforce concrete beams. Beams are designed based
on limit state principles and examined. A Model has
been proposed for calculating the maximum width of
cracks and the strength. The failures were observed
due to reduced post cracking stiffness. Maranan et
al[8] evaluated the geopolymer concrete beams
reinforced with GFRP bars. Main parameters like
nominal diameter (12.7mm, 15.9mm and 19.0mm),
reinforcement ratio (1-2.2) and anchorage system
(mechanical interlock system) were investigated.
Increased reinforcement ratio enhances the
performance. Emadaldin Moammadi Golafshani et
al.[9] investigated the bond behaviour of GFRP bars
in self-compacing concrete. The Changes in the bond
strength of reinforcing bars in the horizontal and
vertical specimens were analysed and compared.
Steel seems to have a better bond than GFRP bars.
Pedro Santos et al.[10] presented an experimental
and numerical investigation about the flexural
behaviour of continuous beams reinforced with
GFRP bars and their capacity to redistribute the
moments. It was observed that the confinement of the
concrete at critical sections enhances the plastic hinge
ductility and the moment. Also the lower elasticity
modulus of GFRP when compared to steel can be
compensated with an increase of the reinforcement
ratio. Abdelmonem Masmoudi et al.[11] presented an
investigation of reinforced concrete beams with
GFRP rebar. Based on the experimental and
analytical studies, it was concluded that GFRP rebars
have a weaker elasticity modulus, which generate
more deflection for equal loads and spans. With
reinforcement of more than 2% of GFRP, the stress
does not increase considerably. Yu Zheng et al.[12]
presented the results of an experimental study of one-
third scaled concrete bridge deck models.
Compressive membrane action was evident in the
slabs of the GFRP reinforced concrete bridges and
the ultimate strengths and serviceability were
improved with the increasing supporting beam width.
Iincreasing the lateral restraint stiffness and concrete
compressive strength could enhance the loading
capacities obviously. Mohamed S. Issa et al. [13]
studied the influence of internal fibres on the
performance of concrete beams reinforced with
GFRP rebars. The experimental results showed that
the internal fibers used improved the ductility and
beam’s flexural strength. Denvid Lau et al.[14]
conducted an experimental investigation on the
ductility behaviour of FRP reinforced concrete
beams. In this study, it is proposed that steel
longitudinal reinforcement should be additionally
fabricated to form a hybrid FRPRC beam in order to
improve its flexural ductility and also to retain high
strength feature of the FRP bars. The study also
includes the effect of 90 and 135 degree hooks in
improving the ductility.
III. RESULTS AND RECOMMENDATIONS
The beneficial effect FRP reinforced concrete beams
is limited due to various drawbacks. The crack widths
of FRC beams were smaller than conventional
concrete beam. The ultimate concrete strains are
larger in FRC beams than the conventional concrete
beams. Addition of fibers proved to be an effective
way to enhance the ductility of FRP reinforced
structural members. To compensate the low ductility,
the members are to be designed as over reinforced
and not above 2% reinforcement ratio is
recommended. Tensile strength of GFRP bars seems
to decrease with increase in diameter. ACI equations
to predict the deflections and crack width showed
good accordance with experimental results.
REFERENCES
1. Benmokrane, Chaallal, Masmoudi. “Glass Fibre
Reinforced Plastic (GFRP) rebars for Concrete
structures”. Construction and Building Materials
1995,9(6);353-364
2. Alsayed, Al-Salloum, Almusallam. “Performance
of glass fiber reinforced plastic bars as a reinforcing
material for concrete structures”. Composites Part B
2000,31;555-567
3. Abdalla. H. A. “Evaluation of deflection in
concrete members reinforced with fiber reinforced
polymer (FRP) bars”. Composite Structures
2002,56;63-71
4. HoussamToutanji, Yong Deng. “Deflection and
crack-width prediction of concrete beams reinforced
with glass FRP rods”. Construction and Building
materials2003,17;69-74
5. Wegian, Abdala. “Shear capacity of concrete
beams rein forced with fiber reinforced polymers”,
Composite Structures 2005,71;130-138
6. Ashour. A. F. “Flexural and Shear capacities of
concrete beams reinforced with GFRPbars”,
Construction and Building Materials 2006,20;1005-
1015
7. Biswarup Saikia, Phanindra Kumar, Job Tomas,
NanjundaRao, Ananth Ramaswamy. “Strength and
Serviceability performance of beams reinforced with
GFRP bars in flexure”, Construction and Building
Materials2007,21;1709-1719
8. Maranan, Manalo, Benokrane, Karunasena,
Mendis. “Evaluation of the flexural strength and
serviceability of geopolymer concrete beams
reinforced with glass fiber reinforced polymer
(GFRP) bars”, Engineering Structures
2015,101;529-541
9. Emadaldin Moammadi Golafshani, AlirezaRahai,
Moammad Hassan Sebt. “Bond Beaviour of steel and
GFRP bars in self-compacting concrete”,
Construction and Building Materials 2014,61;230-
240
10. Pedro Santos, Gilberto Laranja, Paulo M. Franco
and Joao R.Correia.“Ductility and Moment
redistribution capacity of multi span T-section
concrete beams reinforced with GFRP bars”,
Construction and Building Materials 2013,49;949-
961.
11. Abdelmonem Masmoudi, Mongi Ben Ouezdou
and Jamel Bouaziz.“New parameter design of GFRP
RC beams”, Construction and Building Materials
2012,29;627-632
12. Yu Zheng, Guoyou Yu and Yunfeng
Pan.“Investigation of ultimate strengths of concrete
bridge deck slabs reinforced with GFRP bars”,
Construction and Building Materials 2012,28;482-
492
13. Mohamed S. Issa, Ibrahim M. Metwally and
Sherif M. Elzeiny.“Influence of fibers on flexural
behaviour and ductility of concrete beams reinforced
with GFRP rebars”, Engineering Structures
2011,33;1754–1763
14. Denvid Lau and HoatJoen Pam.“Experimental
Study of Hybrid FRP reinforced concrete beams”,
Engineering Structures 2010,32;3857-3865