This is a research on fiber reinforced polymer

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TITLE PAGE

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TABLE OF CONTENTS................................................................................................................................................. iii
CHAPTER 1: INTRODUCTION......................................................................................................................................1
1.1. Background Information...........................................................................................................................1
1.2. Objectives .................................................................................................................................................1
CHAPTER 2: RESEARCH METHODOLOGY ...................................................................................................................3
2.1. Methodology Identification......................................................................................................................3
2.2. Analytical Technology...............................................................................................................................3
2.3. Significance of the Present Study .............................................................................................................6
CHAPTER 3: LITERATURE REVIEW ..............................................................................................................................8
3.1. Definitions.................................................................................................................................................8
3.2. Types of Fibers ..........................................................................................................................................9
3.3. Fiber Surfaces Treatment for FRPs .........................................................................................................10
3.3.1. Plasma treatment ...............................................................................................................................11
3.3.2. Gamma treatment ..............................................................................................................................12
3.3.3. Rare earth treatment..........................................................................................................................13
3.4. Manufacturing Process for FRPs.............................................................................................................13
3.5. Bonding mechanism for FRPs with RC specimens and Formation of the Bond......................................18
3.6. FRP Composites as Internal Reinforcement for Concrete Elements ......................................................20
3.7. Application procedures for FRPs to environmentally exposed specimen..............................................22
3.7.1. Traditional methods............................................................................................................................23
3.7.2. FRP Composite Based Solutions..........................................................................................................23
3.7.3. Flexural Strengthening of Beams........................................................................................................23
3.7.4. Strengthening of RC Columns .............................................................................................................24
CHAPTER 4: DESIGN AND MODEL DESCRIPTION .....................................................................................................25
4.1. Model Description...................................................................................................................................25
4.2. Model of Bond Interface.........................................................................................................................25
4.3. Drucker-Pager Model for FRP restricted concrete .................................................................................26
CHAPTER 5: RESULTS, DISCUSSIONS and CONCLUSIONS.........................................................................................30
REFERENCES.............................................................................................................................................................32

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1.1. Background Information
Fibre Reinforced Plastic (FRP) as composite material are utilized where there is a need for high
mechanical strength, corrosion and temperature resistance and light weight properties (Plasticon,
2016). Furthermore, FRP is critical for the formation of complex shapes with high thermal
insulation and the smooth internal surface where cost is the first decisive selection.
FRP are made from a combination of plastic polymer resin and strong reinforcing fibers (Center,
2014). The components retain their initial form and giving unique individual properties resulting
from a fresh, composite material with improved overall performance. Consequently, polymers are
said to have improved strength and stiffness if reinforced with fibers. Furthermore, polymer resins
aid in protecting polymers from abrasion and chemical attack since they act as binders and are
typically viscous hence mechanically support transfer loads in the composite.
FRP have been used widely in many applications due to their high-strength and lightweight (Hota
& Liang, 2006; Mallick, 2007). FRP are applied in numerous industries like in transportation,
aircraft, corrosion resistant and marine. In the 21st
century, FRP has been used widely in highway
structures due to fast deterioration of other material as a result of harsh environmental conditions
since their strength meshes with limitations of traditional materials (Mertz, et al., 2003).
1.2. Objectives
The paper looks into the idea for the arrangement of FRP from chemical to physical to mechanical
properties. The requisition of the composites produced starting from the basic definitions to the
complexity of the models used in FRP and meshing is discussed. The paper will also look into the
strengths of the bond between FRP-concrete interfaces. Understanding of the configuration of the
bonds loading and meshing are also covered. A numerical model that have been used in the

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concrete confinement models is also discussed. The numerical outcomes of the models shall be
considered. The effects of parameters found in the bonding and models are also discussed.
The main elements of the paper are the effect of the significance of the retrofit and cement columns.
A large number points of interest with FRP reinforcement, yet the primary disservice is those
absence of a broadly acknowledged model that could dependably anticipate those conduct
technique of the FRP restricted cement. So as to take advantage of the mechanical qualities
introduced by FRP reinforcement, a planning model will be recommended for utilizing in the
configuration of the cement columns, alongside a point by point development strategy.

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2.1. Methodology Identification
All around the years, examination for structural building need made significant portions different
support for retrofitting or strengthening systems for structural parts. The practically prevalent from
claiming this is a continuously reinforcing bar, alternately rebar confines. However, a portion of
the other models incorporates fiber-reinforced polymer (FRP) and concrete. Every last bit systems
need their favorable circumstances to allow use of FRP. In this research, models, bonds and
meshing will be presented as systems. Structural characteristic of various models will be discussed.
The research will depend on other papers presented. Conclusions is drawn in line with models
presented.
2.2. Analytical Technology
Conventional rebar support techniques on cement columns have been acknowledged to large
portions a considerable length of time as those regular act. There has been scrutiny on the design
of columns used that are FRP based. Furthermore, designers are skilled of foreseeing what's to
come execution of the columns. More recently, retrofit strategies need to be utilized around to
understand cement columns models.
This incorporates including an extra layer of cement alternately composite material around the
existing section should moderate those crumbling and with building the cement restriction.
Present models exist in the utilization of a mix of a rebar confine. Fiber-reinforced polymer
(FRP) wraps would quick turning into another type of innovation organization to displace
conventional rebar retrofit innovation. The fiber-reinforced polymer covers a composite material
that might make appended of the existing cement section utilizing an epoxy polymer.

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However, FRP wraps need to be utilized within structural requisitions vigorously. Since there
will be not an acknowledged model that need to be turned out should faultlessly foresee future
quality conditions of the restricted cement section.
The centering from claiming this examination venture will be to utilize those comes about-about
an as of now finished test about cement columns limited toward FRP wraps and think about the
coming about stress-strain curves of the ordinarily recommended demonstrating innovation
organization accessible. FRP demonstrating is even now new Furthermore there may be not a
broadly acknowledged model.
The reason for this examination venture may be with determining how faultlessly those suggested
FRP models foresee that quality of the tried columns. There would large portions different types
that need to be proposed, yet the way of the future of FRP retrofitting may be on make A broadly
accepted, dependable model that particular architects prefers alongside the planes. It may be
imperative with standardizing those plan methodology for FRP retrofitted columns in place should
prefer to use the engineering later on.
Restriction in the FRP framework may be undoubtedly imagined. Those pivotal load connected on
the cement makes it extend out radially. The FRP coat may be there with withstand this outward
extension and give acceptable those latent binding weight of the cement. That FRP framework
will, in the end, come up short because of those bending stress in the parallel bearing. The structural
hardware part gives uniform restriction with the FRP system, the same time a non-round part won't
make uniformly limited. In the next sections, a percentage models created to plain. Furthermore
strengthened solid restricted by FRP will have a chance to be exhibited.
The experimental results have been used by Matthys, et al., (2006) in his analytical model to
represent the basis of on confinement to obtain equations. The model inspected two regions of the

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stress-strain curve for FRP confined concrete distinctly. The rebar reinforced concrete acts
similarly to FRP confined concrete in the first region. The methods varied significantly in strain
as presented in the figure below.
Figure 1: Typical FRP Stress-Strain Diagram
A separate study done by (Samaan, et al., 1988) recognized the overestimation involved in the
typical FRP confinement model that was based off of Mander et al.’s (1988) model developed for
reinforced concrete. Recognizing the fact that concrete dilation was the most important factor in
developing a widely accepted and accurate confinement model for FRP, it was the most important
characteristic in distinguishing their model from previous efforts.
Samaan et al. tested 30 cylindrical specimens under axial loads, and developed a new model to
more closely represent the behavior of FRP confined concrete. Their comparison of several

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existing models is presented in Figure 2.5. As can be seen, the existing models at the time over-
estimate the confinement of the FRP reinforcement.
Figure 2: Confinement Model Comparison
Spoelstra & Monti, (1999) created a restriction model not main for FRP support as well as for steel
jackets or other transverse support. Furthermore, in other model where built model was used where
an iterative approach was utilized. The model keys on the communication between those dilating
cement and the binding device. In all the cases, the model had a capacity of strains showing that
the models exhibited different strains.
2.3. Significance of the Present Study
The study justifies the need for research on FRP an alternative too many engineering applications
which have for long time seen challenges. For instance the issue of strength while at the same

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time taking into consideration of the weight has been a resulted in many possible faults. This
research has shown that FRP are when used and designed properly will aid solve the basic
engineering problems.

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3.1. Definitions
Fiber reinforced polymers are considered composite materials since they are formed when two or
more materials are combined to have better property than their original properties (Singh & Soni,
2016). Composites materials can be categorized as natural or synthetic such as wood which is a
natural composite of cellulose fiber and lignin. Other types of composites are ancient Egyptian
manufactured composites like the adobe bricks.
Regarding phases, composites materials are in two phases (Christensen, 2012; Hashin, 1983;
Vinson & Chou, 1975): secondary and primary. Secondary phase is often known as a reinforcing
agent which act as strength boosters and is made amongst the three primary materials like boron
or carbon. Primary composite, on the other hand, is the datum for matrix formation from where
the secondary phase is embedded.
Fiber is one of the types of composites materials along with particle, flake, laminar or layered and
filled composites. Composites can also be classified into the following materials polymer matrix
composites (PMCs), metal matrix composites (MMCs) and ceramic matrix composites (CMCs)
(Matthews & Rawlings, 1999). MMCs are mixtures of ceramics such as aluminum or magnesium
reinforced with fibers. CMCs are least common and embedded with fibers to improve properties
of the materials, e.g. aluminum oxide. PMCs, on the other hand, are the most familiar such as
epoxy and polyesters and forms the fiber reinforcement.
The matrix in composite material functions to provide bulkiness of the product in holding the
imbedded phase in the proper position besides sharing the load with the secondary phase
composites. The fibers can be oriented in the three forms: one-dimension, where maximum

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strength and stiffness of the material is attainable in the direction of the fibers (Berthelot, 2012).
Planar, which is in two-dimensional intertwined fiber. Random or three-dimensional phase in
which the materials possess isotropic properties.
The term composite is mostly used with FRP. Thus FRP can be defined as a polymer matrix
embedded with high-strength fibers. FRP are widely used in rubber in the manufacture of tires and
conveyor belt (Shalin, 2012). Glass, carbon, and Kevlar are the principle fiber matrix while epoxy
reinforces advanced composites such as carbon, Kevlar, and boron.
3.2. Types of Fibers
Fiber is made up of fiber (carbon, glass, basalt and aramid) and resins also known as a polymer
(Gevin & Knight, 2014). Aramid fibers are sensitive to environmental conditions while glass
failure is due to two possible methods: creep under high loading and degradation in the alkaline
environment. Carbon and Basalt are regarded as premium cost and future of FRP respectively.
Resins, on the other hand, are in two broad categories (Gevin & Knight, 2014; Saheb, et al., 1999):
thermoset resins which are in structures and is always in a liquid state under normal conditions
before curing. Thermoset resins are always impregnated into reinforcing fibers before heating
which result in a chemical reaction and becomes solid after heating. Thermoplastic resins, on the
other hand, is solid at room temperature and hence is often heated to a liquid state and pressurized
to impregnate reinforcing fiber. Worth noting is that they are cooled under pressure and can be
reversed.
Thermoset resins are also of varied types (Ratna, 2009): polyester which has the lowest cost and
is easier to use but is sensitive to UV degradation and has moderate mechanical properties. Vinyl
ester that is for industrial standard since they pose very high chemical or environmental resistance
while at the same time sensitive to heat. Polyurethane whose cost are premium and is very flexible

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has high chemical or environmental resistance; and epoxy whose cost is above average and are
commonly used in aerospace applications due to their higher mechanical and thermal properties,
better moisture resistance and longer durability but corrode very fast when not handled
appropriately.
3.3. Fiber Surfaces Treatment for FRPs
Fiber surface treatment can be analyzed in terms of treatment of Carbon Fibers (CFs). CF are
common in plastics; CF reinforced the material, carbon-carbon composite, and CF reinforced
cement. CF are known to possess the highest specific modulus and strength as compared to any
other reinforcing fibers (Donnet & Bansal, 1998). Consequently, their usage is in areas where
lower weight, high strength, and stiffness besides outstanding fatigue characteristics are key
specification. Also, their use is in areas where chemical inertness, excellent thermal and electrical
conductivity, high damping and temperature are essential criteria used for selection. The linear
coefficient of thermal expansion must also be low in CFs to suit their applicability. Aerospace and
nuclear engineering are the two most important sectors of CFs applications. Besides the
transportation sector like bearings, cams, gears, and fan blades and general engineering are also
where they are used mostly (Buckley & Edie, 1993).
CFs must be surface treated since without surface treatment their composites results to low
interlaminar shear strength (ILSS) that are prone to weak adhesion and poor bonding between the
matrix and fiber (Ma, et al., 2015). Treatments have two major advantages of in that it increase the
surface acidity of functional groups and area thereby improving bonding between the fiber and the
resin matrix. This further increases the wettability of the CFs, which also enhances the ILSS.
The major surface treatments can be categorized into oxidative and non-oxidative treatments.
Oxidation treatments are liquid-phase oxidation, gas-phase oxidation all which are carried out

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chemically or electrochemically (Kozhevnikov, 1998). However, there is also catalytic oxidation.
The non-oxidative treatments, on the other hand, entails deposition of more active forms of carbon,
like the highly effective winterization and the deposition of pyrolytic carbon. Besides many
treatment methods, there exist plasma treated, which improve bonding between the fiber and
matrix. Further, liquid phase oxidation treatments that are mostly preferred are very effective and
milder.
Oxidative and non-oxidative methods mostly use acid (HNO3) treatment, rare earth treatment
plasma treatment and gamma irradiation of CF, which are discussed later in the section besides
discussion of the main types of surface treatments.
In oxidative method involves the production of the acidic functional groups on the CFs surface.
The effectiveness of treatment which results in improvement of the surface properties that rely on
medium oxidative concentration, the fiber itself, treatment time and temperature. In general,
oxidation is achieved by use of gasses or liquids such as nitric acid, hydrochloric acid. Other
studies have shown that oxidation leads to the formation of various types of acids such as
carboxylic acid (Yue, et al., 1999). The increase in the acidity is a linear function. Worth noting
is that the tensile strengths of the fiber decrease as oxidation time increases, revealing that the
surfaces of fibers may be pitted and fragmented. Oxidation also leads to positive changes in the
surface area of the fiber.
3.3.1. Plasma treatment
Plasma is an electrically conducting medium which consists of cations, anions and neutral atoms
or molecules (Tiwari & Bijwe, 2014). The principal purpose of plasma treatment is the
modification of physical and chemical structures of the surface layer without interfering with
mechanical properties of the polymer. Majorly, plasma treatment aims at controlling interfacial

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bonding, which is critical in strengthening fiber-reinforced composites. Plasma treatment promotes
possible removal of surface contaminants aiding in better resin contact. It also enhances the extent
of degree of mechanical keying between the fiber and the matrix as the fiber surface roughness is
improved. Further increase in wetting of the matrix and increase in the chemical interactions
between the fiber and the matrix resin is also made possible (Hegemann, et al., 2003).
Figure 3: Plasma surface treatment
3.3.2. Gamma treatment
Gamma treatment involves exposing high-energy gamma-irradiation leading to surface
roughening besides the addition of chemical groups (Tiwari & Bijwe, 2014). This is achieved by
hardening of resins taking in the fibers enhancing strength and wear behavior. The performance of
the surface is treated FRP also improves as surface roughness improves, resulting improved fiber-
matrix adhesion (Xu, et al., 2007).

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3.3.3. Rare earth treatment
Chemical bonding permits absorption of rare earth onto both the CFs surface and the matrix
(Tiwari & Bijwe, 2014). Chemical bonding forms a platform from where the concentration of
reactive functional group can be made active. The functional groups improve the compatibility
between CFs and PI matrix by forming a chemical combination between the CFs and PI matrix
thereby increasing the interfacial adhesion between CFs and PI matrix (Cheng & Shang-guan,
2006).
3.4. Manufacturing Process for FRPs
There are many methods for manufacturing FRPs. The choice of manufacturing methods depends
on the use of the FRP. For instance, FRP manufactured for container assemblies can be made in
part to allow transportation of the parts for assembly elsewhere (Gutierrez & Bono, 2013).
However, the physical requirement of the FRP product will also determine the method of
production. Another production process can be developed with the aim to reduce the cost while
maximizing on the process to meet the commercial and technical necessities. For instance,
pultrusion method was developed for the production of beams that is extended structures which
are expensive when other methods are used.
Some methods are based on the capacity for the production hence need for other mechanization
like automation. For instance, the sheet molding compound (SMC) and bulk molding compound
(BMC) combine the production capacities generate Glass Fiber Reinforced Polymer (GFRP)
whose profiles can be set to produce a different surface finish. This is done by controlling the
orientation of reinforced fiber. This process is difficult to attain in other production processes.

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Other processes like Resin Transfer Moulding (RTM), which uses a higher level of capital and
whose productivity potential is good, is based on the improvement of another process (Mortimer
& Coppock, 2003).
Quality is also an aspect that is considered when the production process is decided. For instance,
in an event where excellent structural properties are required, the component of the product has to
utilize the fiber alignment. Two automated FRP manufacturing methods that are known to provide
both the quality and manufacturing capacity at a reasonable cost are filament winding and
pultrusion (Gutierrez & Bono, 2013; Hensher, 2016). Filament winding though good at offering
the possibility of manufacturing good quality laminates, the curvature produced during the process
can only be used to generate cylindrical shells of revolution. If the curves are used for non-circular
sections, the curvature has to be positive on the outside of the tool. Hence the process can be used
mostly for structural components like columns or beams.
In general pultrusion as a technique and process can be used perfectly for longitudinal elements
whose properties specially allow axial loading such as primary column and perimeter beams
(Gutierrez & Bono, 2013).
The figure below shows how FRP manufacturing processes can be classified.

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Figure 4: Fiber Reinforced Polymer manufacturing processes classification (Gutierrez & Bono,
2013).
Before the process of formation of the FRP, the materials are separated and combined during
shaping processes such as filament winding and pultrusion (already discussed). The materials are
then combined for use in the shaping process like prepregs and molding compounds (Gutierrez &
Bono, 2013). The molding compounds are made of resins matrix with short fibers like the ones
used in plastic molding. The molding material must be able to flow and must already be cured

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during or after shaping. Prepegs on the other hand are fibers impregnated with partial thermosetting
resins to ease and facilitate shape processing. They are often available as tapes or fabrics and are
fabricated with continuous filaments hence boosting the strength and modulus of the composites.
From the diagram, it is clear that the processes can be said to be open mold processes. Open
processes are those processes that use a single positive for production of laminated FRP structures
(Vockel Jr, et al., 1992). The shaping process begins with resins, fibers, mats and woven roving
applied to the mold in layers to build the desired thickness. Curing and part removal are then done.
Hand Lay-Up Method is the open mold shaping where successive layers of resins and
reinforcement are applied manually to an open mold to build the laminated FRP composite
structure. The method is labor intensive and the product must be trimmed with powder to reduce
the outside edges and is the oldest method.
Other processing methods commonly known are Hand lay–up, or contact molding, also known as
the oldest and simplest way of making fiberglass–resin composites. Hand lay-up process is mostly
used in the manufacture of standard wind turbine blades, boats. The process involves treatment of
mold and release agent. The process proceeds with the application of thin gel coat outside the
surface of the molding. After partial settling of resins, fiber is applied in the form of mat or cloth.
Each layer is then rolled to impregnate the fiber with resin and remove air. Then the part is cured
and removed after hardening (Gutierrez & Bono, 2013).
In other processes, successive FRP laminations of the mold are created by spraying liquid resin
and chopped fibers (Weatherhead, 1980). There has been an attempt to mechanize application of
resin-fiber layers to reduce the time taken for this process to be completed. On the other hand, in
spray–up process as a method entails simultaneous spraying of chopped fibers and resins into or

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onto the mold. The resultant products are mostly used in making of small boats bodies, truck
fairings, caravan bodies, and bathtubs.
The vacuum–bag molding process was developed to make various components such as relatively
large parts with complex shapes (Gutierrez & Bono, 2013). The product is mostly used in the
making of large cruising boats and racecar components. Pressure–bag process is a mirror image of
vacuum–bag molding and products are mostly used in the manufacture of sonar domes, antenna
housings and aircraft fairings (Gutierrez & Bono, 2013). In this process, prepreg layers are
wrapped around rubber blocks and placed in a metal mold. As the rubber expands due to heating,
it puts pressure in the metal laminate forming a simple or complex shape. Autoclave Molding
process resembles vacuum-bag and pressure-bag and is used to make parts for agile fighter aircraft,
motorsport vehicles.
Closed mold processes are often performed in molds consisting of two sections that open and
closes each molding cycle (Gutierrez & Bono, 2013). The complex equipment used in the process
makes open mold expensive. The primary processes are compression molding, where there is a
transfer of molding and injection molding. In compression molding, in the lower sections, a charge
is placed to bring together pressure forcing the charge to take the shape of the cavity. After
sufficient curing, the mold is removed, and the part used.
Transfer molding processes, on the other hand, use charge of the thermosetting resin to make the
mold. In this method, thermosetting resins with short fibers are placed in a pot or chamber, heated
to cure the resins, and squeezed by ram action into one or more mold cavities. Injection molding,
on the other hand, is cheap and thermoplastics, whose process is adaptable to thermosets.
Reaction injection molding (RIM) uses two reactive ingredients mixed and injected into a mold
cavity where curing and solidification occur due to chemical reaction. Reinforced reaction

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injection molding (RRIM) is similar to RIM with the difference being the typical glass fibers in
the mixture. It is preferred to RIM since it is cheaper due to lack of heat. RIM process is used tom
make a product like auto body truck cab applications for bumpers, fenders, and other body parts.
When pultrusion has more additional steps, it is then called performing (Gutierrez & Bono, 2013).
Unlike pultrusion which is only limited to straight sections of constant cross section, pulforming
has unlimited straight sections. There is also a need for long parts with continuous fiber
reinforcement that are curved rather than straight and whose cross sections may vary throughout
the length. Performing is suited to these less regular shapes.
3.5. Bonding mechanism for FRPs with RC specimens and Formation of the Bond
Bonding mechanism can be related to loading of the FRP at the interface. This is because the bonds
act as a link between FRP sheet and the concrete. In reality, when compressive strengthening is
used for wrapping a concrete column, FRP would provide a confining pressure, which requires a
close contact with the concrete (Yao, et al., 2005). Load transfer mechanism in bonding resembles
the one between concrete and steel plate. The load transfer often consists of three components;
Epoxy applicable at the interface of concrete, FRP Friction between FRP and concrete that relies
on the roughness of surfaces.
Mechanical interlocking of bonds is in various forms. The bond strength in mechanical fasteners
is heightened by fastening the laminates to FRP with steel fasteners. The modes of failure of the
bonds also differ, for instance, the desirable mode of failure of FRP is rupture which happens after
maximum capacity has been attained and surpassed (Mani, 2013).
Debonding, which is brittle, is the most common mode of failure and takes before crushing in the
concrete or rupture in FRP sheets. The knowledge on all modes of failure is important since it
helps in the understanding of the ultimate loads at failure.

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Studies have been done on different modes of failure, for instance, Smith & Teng, (2002) study
revealed six modes of failures including; crushing of concrete, concrete cover separation, FRP
rupture, plate end interfacial debonding, and the interfacial crack induced interfacial debonding,
and shear failure.
Figure 5: Failure modes of FRP strengthened concrete (Smith & Teng, 2002)
Intermediate crack induced debonding, is where the debonding occurs at the crack near mid-span
and then extends to the end of the beam. In plate end debonding, the failure takes place at the end
of the beam and then spreads inwards to its middle. Plate end debonding can pervade to
longitudinal reinforcement propagating along the reinforcing bars causing concrete cover
debonding. This is known as concrete cover separation (Mani, 2013).

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For shear failure, mode failure is the same and consists of FRP rupture and interfacial debonding.
Methods for preventing debonding failure exists in different forms. These methods make use of
mechanical anchors, application of U-wraps or transverse FRP sheets. Worth noting is that bond
performance differs from the type of material used, for instance, the behavior of bond at the FRP-
concrete interface is different that of concrete-steel interface in structural concrete.
The type of orientation of the fibers and resins affects the behavior of the bonds (Cosenza, et al.,
1997). For instance, the anisotropic performance of FRP is different with the isotropic behavior of
the steel reinforcement. This is what controls the failure mechanism and is majorly used as a design
question. In general, the bond mechanism depends on the friction between the surfaces and the
adhesive layer characteristics at the interface (Ehsani, et al., 1994).
3.6. FRP Composites as Internal Reinforcement for Concrete Elements
The studies on the bonding of FRP-concrete interface have focused on the load transfer. FRP
composites materials have been used in the 21st
century in construction more as was used initially.
This has been field by different researchers who have shown that composites bond strengths are
superior to the traditional building materials (Nicolae, et al., 2008). Thus the materials have been
used in the upgrade of the old buildings.
The use of FRP composites as internal reinforcement for concrete elements have been fuelled by
the fact that FRP composites have a high strength to specific weight ratios, are electromagnetically
transparent, have increased resistance to corrosive agents, reduced own weight hence are suitable
for structural applications (Berthelot, 2012). FRP composites have high tensile strengths making
them suitable as an alternative to longitudinal reinforcing elements (shown in figure 4 and 5) for
concrete structural members subjected mainly to flexural failures (Cosenza, et al., 1997).

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Figure 6: Different types of FRP composites reinforcing bars for concrete elements (Nicolae, et
al., 2008).
Figure 7: Bridge deck reinforced with FRP bars (Nicolae, et al., 2008).

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The success in the use of FRP composite relies on the adoption of steel reinforcement with basic
design codes. The anisotropic performance of FRP is different with the isotropic behavior of the
steel reinforcement, which leads to superior mechanical properties development and is only strong
in the longitudinal direction as opposed to the transverse direction where fiber reinforcement is
weak, as shown in Figure 6. This is different as related as to steel. Therefore, transversal properties
and bond characteristics directly affect the usability selection of FRP.
Figure 8: Variation of mechanical properties of FRPs with loading direction (Nicolae, et al.,
2008).
3.7. Application procedures for FRPs to environmentally exposed specimen
The application procedures for FRP to environmentally exposed sample can be can be presented
in terms of:

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3.7.1. Traditional methods
Traditional methods handle strengthening solutions of Reinforced-Concrete members, which can
range from repair of damaged members to restore their initial original load-carrying capacity to
boost their strength. The traditional methods are project specific but adhere to general approaches.
However, the most common and traditional techniques to strengthening Reinforced-Concrete
members are as follows: Increasing the concrete reinforcement cross-section. Followed by addition
of prestressing to discharge the dead load and using plate bonding to improve tensile reinforcement
of the RC elements. Then the addition of confining elements to the performance of the concrete in
the compression members; and shear strengthening by installing external straps.
3.7.2. FRP Composite Based Solutions
FRP Composite Based Solutions entails strengthening of existing deteriorated reinforced concrete
(RC) members done to (Teng, et al., 2004): reduce chances of failure in beams and columns caused
by the inadequacy of longitudinal reinforcement. The use of external bonded FRP of plates and
fabrics enables an increase in the bending capacity of concrete elements. This procedure can also
be done by mounting near-surface strips or rods with the fiber longitudinal to the member axis.
Furthermore, the inadequacy of transverse reinforcement may have brittle effect near shear failure
in structural members such as shear walls, columns, beams and beam-column joints. This shear
capacity of concrete members can be improved by if externally bonded FRP fibers are oriented in
the transverse direction.
3.7.3. Flexural Strengthening of Beams
Degradation as a result of corrosion of steel reinforcement, freeze-thaw action, cracking of
concrete from extreme carbonation, spalling of concrete cover, effects of alkali-silica reactions and
changing in loading patterns. The need for methods of repair and strengthening of RC beams and

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girders has been imposed by (Karbhari & Seible, 2000); cases of increasing load carrying capacity
of bridges to reduce the cost of technology while at the same time reduce distress in traffic. The
need to strengthen existing beams buildings where the occupant’s activities have led to the
deterioration of building materials. This method mostly uses the addition of adhesive-bonded steel
plates on the tension side of the RC beams.
3.7.4. Strengthening of RC Columns
Traditional ways of strengthening measures for Reinforced Concrete columns are in the range from
external confinement and steel use of steel cables which are wound helically around the existing
column at closely proceeded by coverage of concrete and use of steel jackets welded together in
the field confining the existing columns (Ciupala, et al., 2003). These methods are effective but
are labor intensive, time-consuming. Some of these rely on field welding, quality, which is often
questionable. The changes introduced in the columns can cause degradation due to corrosion and
can trigger stiffness hence causing variation in changes in seismic force levels.
The most common of these methods is FRP column strengthening which entails external wrapping
of FRP straps. To reduce or alleviate the occurrence of stiffness, FRP composites can be used for
confinement. Also, the use of FRP composite confinement enables rapid fabrication while at the
same time reduces cost.

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4.1. Model Description
In this paper, FRP confined with concrete columns are proposed for new construction and
rebuilding of concrete piers/piles in engineering structures. The modeling design requires accuracy
to enhance performance estimation for confinement mechanism. Thus a proper solution relies on
the development of confinement model relating to concrete strength with the unconfined concrete
strength besides the confining pressure whose provision is guided by FRP. This model has a close
form expression which implies that the applicability of the design will be relation to confinement
models predominant in designing of FRP confined concrete columns.
Further, it is noted in this model that the design oriented models are directly based knowledge on
the analysis of the design results since each existing design is based on certain range of test
database and the prediction of the results is within the expected range.
4.2. Model of Bond Interface
A durable component with traction-separation demonstrating technique may be utilized for
demonstrating the epoxy. A standout amongst those requisitions for durable components will be
demonstrating cement materials. What is more is that bond interface depends on various factors.
Those conduct from claiming durable components relies on ahead a few factors, for example, their
physical properties, their application, and the kind of the reactions mimicked.
There need aid three sorts for conceivable responses: traction-separation built modeling,
demonstrating for gaskets, which are continuum-based. A short depiction for every reaction is
reviewed, and the purpose behind suitable of the footing detachment model as the best model for
simulating epoxy is explained: Traction-separation based modeling: this model is impeccable. The

30. 26
point when the thickness from claiming paste is unimportant. This constitutive model acceptance
and the conducting technique holding. This model might anticipate debonding initiation, harm
propagation, and so on. Those material properties assume a real part in this model.
Constantly on about these aspects from claiming footing division model make it a perfect decision
for demonstrating durable zone. Continuum -based modeling: Dissimilar to traction- division built
modeling, this model will be impeccable if the point that thickness of the paste may be significant
and limited. This reaction could suspect split start and proliferation.
Demonstrating of gaskets: Similarly, as that sake of this reaction suggests, exactly extra abilities
need aid joined should model the gaskets. Some of these properties would as takes after: they
would be fully nonlinear, they camwood be utilized within progressive analyses, Also that this
model could be a chance to be characterized towards material properties from claiming paste.
Done these strong elements, with traction-separation demonstrating system might have been
utilized to demonstrating the collaboration between the FRP laminates and the cement. Interfacing
durable components with contiguous components might have been crucial, on account of the
network thickness done epoxy layers is substantially better over those contiguous elements.
The procedure used for modeling makes use of traction-separation modeling for interrelationship
between FRP laminates and concrete. The connection between cohesive elements and adjacent
elements are vital since density in polymer layer is better than the adjacent elements which might
causes error during analysis of the model.
4.3. Drucker-Pager Model for FRP restricted concrete
The Drucker-Prager (D-P) model has been realized in FRP as yield criterion for confined or
restricted concrete (Yu, et al., 2007). D-P has been used mostly in FRP and concrete model since
it is simple as it involves only two parameters. The criterion significance increases since

31. 27
hydrostatic pressure increases increasing its capability to capture shear strength. An increase in
hydrostatic pressure as significance of the criterion is the most distinguishing feature of concrete
under confinement.
Meridian plane, which is shown by an inclined is used to represent D-P yield and failure surfaces
(Jayajothi, et al., 2013). Shear strengths of concrete differs from the point of application. For
instance, according to Chen & Lan, (2004) and Chen, (1982), the shear strength of concrete under
equal biaxial compression and that under tri-axial compression are not equal, even when the first
stress invariant of the two cases are the same.
In light of the plasticity theory, it will be known that those stress states about rise to biaxial
layering. Furthermore, triaxial layering relate will diverse boundary positions on the
disappointment surface in the deviatoric plane. Those shear quality proportion between these two
situations might a chance to be found starting with test effects or experimental equations for the
qualities about cement under rise to biaxial layering or trial layering. The test outcomes of would
utilized cement under rise to biaxial. Layering and the experimental mathematical statement
suggested. Compression, this quality proportion was around 0. 7 (Yu, et al., 2007). Therefore, a
disappointment surface which plans during reflecting reveled test conducted from claiming cement
to represent those impact of the third deviatoric stress invariant and adoption. A non-round
disappointment bend in the deviatoric plane. Cement utilizing a cement model over which will be
known as those spread split cement model. Also need a yield paradigm which may be the same as
the D-P yield paradigm to cement clinched alongside layering. Therefore, these models can't give
exact predictions for both the quality from claiming cement under rise to biaxial layering. Also
that from claiming cement under triaxial layering. Additionally making deduction on the crest
stress about cement under non-uniform restriction which cannot be faultlessly predicted.

32. 28
Those anxiety state for non-uniform restriction corresponds with a boundary position the middle
of that about triaxial.
Therefore, those crest anxiety about this situation can't a chance to be faultlessly predicted as the
two amazing cases which cannot make both faultlessly characterization Loading and Meshing
The discretization of the domain of smaller subdomains is the first step to finite element analysis.
Different methods are available for generation of mesh in the modeling procedure like manual
discretization, Automatic mesh generation, which include methods such as Octree method,
Tesselation method and Bottom-up approach (Yao, et al., 2005). These procedures are not
appropriate for meshing various elements of the specimen hence a manual discretization method
is proposed for meshing the elements. Meshing procedure influenced (Jayajothi, et al., 2013) by
various factors, like geometric specifications.
Generally, meshing process is clear. The procedure comprised from claiming two phases. In the
primary stage, seeds categorized on the edge of the second segments (Mani, 2013). Meshes are
allocated for every a component which are dependent on wanted level of claimed accuracy where
the meshes is controlled. For epoxy layers with significant risk, more accuracy is needed hence
better refined mesh is vital. Determination of mesh size depicts that a number of elements are
required. These elements include seeds at the edge of the parts.
However, the effect of the mesh size and quality on the final results requires that several factors
are considered (Yao, et al., 2005). These are size and location of elements and nodes respectively.
These elements at the same time are the most important factor that affects mesh quality. Aspect
ratio, which is the ratio of the largest to smallest dimension, is significant as it dictates the shape
of the elements. Consequently, an aspect ratio of one is the most regarded.

33. 29
Material property, geometry, or load determines the existence of any disruption in the nodes. The
loading of the node determines the modeling of a concrete block (Jayajothi, et al., 2013).
Nonetheless, there is no discontinuity, in FRP laminates and this can be divided in equal partitions
without any extra nodes.
A number of elements determines the level of accuracy of the modeling procedure. The initial
procedure is prone to errors in modeling hence there reliance is skewed to the second procedure.
It is worth noting that increasing the number of elements does not guarantee the accuracy of the
solution indefinitely causing certain point, hence adding complexity to computational errors.

34. 30
Three perceived models done FRP support were broke down and contrasted with test effects found
starting with those test with respect to three columns retrofitted with FRP. Those coming about
stress-strain curves starting with the three test columns were analyzed against those hypothetical
stress-strain curves. The eventual models suggested that demonstration of the expansion over
quality given by the FRP support. Those section have demonstrated against a generally
acknowledged strengthened solid model.
The examination venture might have been continuation of a bigger examination venture finished
which shows FRP are superior to conventional engineering materials. The FRP strengthened
columns were utilized proved that modern materials like FRP are versatile. Those expectation for
this task is will view how the information that we need starting with that undertaking for those
load Also simultaneous uprooting of the FRP strengthened columns matches dependent upon those
hypothetical stress-strain curves from claiming A percentage prominent models. The coming
about plots compared the hypothetical model test on the three columns further proved FRP are
more appropriate for engineering applications. They give a great premise for the contention for if
those information might bring a percentage imperfections, alternately assuming that the model
might not be exceptionally solid to this kind of provision.
Those expectation from claiming this project might have been to dissect FRP support models with
a set for information that needed not been analyzed in this paper. Those three models were
analyzed, also there were a few guaranteeing effects. Other models have a large portion exactness
proving the results of the single-performed experiments. However, this is main accurate in the
carbon-FRP column, which is similarly to the glass-FRP section might have been not predicted
faultlessly. Some models presented shows reliably over-estimated quality of the columns.

35. 31
A percentage issues existed in the FRP demonstrating results, yet a few from claiming them might
a chance to be undoubtedly demonstrated. The greater part of all the models required challenge
demonstrating those to begin with straight part of the bilinear stress-strain bend. However, this
conduct is in front of those FRP may be actuated. Furthermore, if the paper is reflected poorly,
then models would be inaccurate. This mistake might have been well on the way on bring been
initiated toward the aspects of the cement constantly demonstrated erroneously. Assuming that
inaccurate compressive stress may be recorded to those concrete, the initial straight bend might
have a chance to be somewhat off of the outcomes. This not best makes inaccurate modulus of
elasticity, Anyway an inaccurate yield perspective, hence FRP when blended with other materials
like concrete where the use of FRP will be justified.

36. 32
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