S. Marvel Dharma

PG Student, Dept. of Civil Engineering

EBET Group of Institutions,

Tirupur, India

Id: marvel.civilaspirer@gmail.com

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.

Id: yaminiroja@gmail.com

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.

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