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Thermomechanical responses of concrete members strengthened with CRFP sheets

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Title:
Thermomechanical responses of concrete members strengthened with CRFP sheets
Creator:
Alqurashi, Abdulaziz ( author )
Language:
English
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1 electronic file (255 pages) : ;

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Subjects / Keywords:
Carbon fiber-reinforced plastics ( lcsh )
Iron and steel bridges -- Corrosion ( lcsh )
Steel, Structural -- effect of high temperature ( lcsh )
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theses ( marcgt )
non-fiction ( marcgt )

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Abstract:
Strengthening structural members means to be able to carry additional loads. Since, 1990s, a lot of materials and techniques have been established to not only increasing the capacity of member but also facing deterioration. Deterioration has become one of the worst highly maintenance cost. According to The ASCE, 27.1% of all bridges in the United States are not effectual. This is because the high traffic reflects negatively to structural members and cause deterioration of these members. This problem has been cost a lot of money. In addition, FRP has approved that it can increase the capacity of member and overcome some disadvantages such as deterioration. Therefore, CFRP sheet has become widely used. However, high temperatures affect the performance of externally bonded CFRP sheet negatively. Investigation should be carried out on relaxation and flexural performance of members under different temperatures. Therefore, this thesis focus on analyzing and investigating the performance of strengthened members exposed to elevated temperatures (25 to 175 0C). The experimental program was divided to two main parts. First, 144 strengthen concrete blocks 100mm X 150mm X 75mm has been exposed to elevated temperatures. These blocks have two main categories, which are different CFRP sheet width, and different CFRP sheet length. Different CFRP width has three types, which are type 0.25B (25mm x 100mm), type 0.5B (50mm x 100mm) and type 0.75B (75mm x 100mm). Also, Different CFRP length has three types, which are iv type Le (bonded area of 50 mm by 90mm), 1.25 Le (area of 50mm by 125mm) and type 1.5Le (50mm by 137 mm). Second, studying the performance of RC beams exposed to elevated temperatures.
Thesis:
Thesis (M.S.) - University of Colorado Denver
Bibliography:
Includes bibliographic references
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System requirements: Adobe Reader.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Abdulaziz Alqurashi.

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University of Colorado Denver
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Auraria Library
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946649435 ( OCLC )
ocn946649435
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Full Text
THERMOMECHANICAL RESPONSES OF CONCRETE MEMBERS
STRENGTHENED WITH CFRP SHEETS
By
ABDUL AZIZ ALQURASHI
B.S., Umm Al-Qura University, 2010
A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fulfillment
of the requirements for the degree of
Master of Science
Civil Engineering
2015


2015
ABDUL AZIZ ALQURASHI
ALL RIGHTS RESERVED
11


This thesis for the Master of Science degree by
Abdulaziz Alqurashi
has been approved for the
Civil Engineering Program
By
Yail Jimmy Kim, Chair
Cheng Yu Li
Nien Yin Chang


November 20, 2015
Abdulaziz, Alqurashi. (M.S., Civil Engineering)
Thermomechanical responses of concrete members strengthened with CFRP sheets.
Thesis directed by Associate Professor, Yail Jimmy Kim
ABSTRACT
Strengthening structural members means to be able to carry additional loads. Since,
1990s, a lot of materials and techniques have been established to not only increasing the
capacity of member but also facing deterioration. Deterioration has become one of the
worst highly maintenance cost. According to The ASCE, 27.1% of all bridges in the
United States are not effectual. This is because the high traffic reflects negatively to
structural members and cause deterioration of these members. This problem has been cost
a lot of money. In addition, FRP has approved that it can increase the capacity of member
and overcome some disadvantages such as deterioration. Therefore, CFRP sheet has
become widely used. However, high temperatures affect the performance of externally
bonded CFRP sheet negatively. Investigation should be carried out on relaxation and
flexural performance of members under different temperatures. Therefore, this thesis
focus on analyzing and investigating the performance of strengthened members exposed
to elevated temperatures (25 to 175 C). The experimental program was divided to two
main parts. First, 144 strengthen concrete blocks 100mm X 150mm X 75mm has been
exposed to elevated temperatures. These blocks have two main categories, which are
different CFRP sheet width, and different CFRP sheet length. Different CFRP width has
three types, which are type 0.25B (25mm x 100mm), type 0.5B (50mm x 100mm) and
IV


type 0.75B (75mm x 100mm). Also, Different CFRP length has three types, which are
type Le (bonded area of 50 mm by 90mm), 1.25 Le (area of 50mm by 125mm) and type
1.5Le (50mm by 137 mm). Second, studying the performance of RC beams exposed to
elevated temperatures.
The form and content of this abstract are approved. I recommend its publication.
Approved: Jimmy Kim
v


ACKNOWLEDGEMENTS
Since I got B.S. at 2010,1 have been excited to study more about civil engineering.
In spring 2014, associate Professor Yail Jimmy Kim -the ideal- gave me an enormous
opportunity to be one of his amazing research team. Without his advice and inspiration, I
could not do this entire thesis. I appreciate him for all work that he has done for me or to
the research students. He is my thesis adviser and he supports me and encourages me to
do the best. Every Friday meeting, I have learned new things not only for me work but
also to develop me skills. Also, I appreciate all civil engineering members, who are
department chair, committee chair, and committee members. I would like to also thank
the Faculty of Engineering Department, who help me and support me to reach me goal.
Also I would like to thank the lab staff members, Tom, Jack, and Eric.
I would like to thank research mate student for their assistance, and
encouragement. Ibrahim bumadian, Abdullah Alajmi, ihama lkubaisy, Ahmed Mutalib,
Thushera, and Yongcheng, Thank you all friend. You help me and support me.
Thanking to Saudi Arabian Cultural Mission (SACM) and Islamic university for
help me and be sponsor of me master studying. They were with me since I came
Colorado. Thank you so much. I would take this opportunity and thank Dr. Mohammad
Farouq Addas, who always encourage me to do the best.
Finally, My parent thank you so much for all helping and supporting. You were
the fuel that makes me work. I always feel you around my all time. I would like to thank
vi


you for all work that you did for me. I would take this opportunity to thank my wife and
son for making my life happy.


TABLE OF CONTENTS
Chapter
1. Introduction.....................................................................1
1.1 General..........................................................................1
1.2 Research significance and objectives............................................3
1.3 Thesis organization.............................................................5
2. Literature review................................................................7
2.1 Strengthening systems for concrete structures...................................7
2.2 FRP.............................................................................8
2.2.1 FRP applications..............................................................10
2.2.2FRP techniques.................................................................11
2.2.3 NSM FRP strengthening system.................................................14
2.3 Externally bonded sheet strengthening system.................................16
2.3.1 Externally bonded sheet techniques............................................17
2.3.2Previous applications on externally bonded sheet...............................18
2.3.3Previous research studies on externally bonded sheet FRP.......................19
2.4 Fire endurance of concrete Structures..........................................19
2.4.1 Effect of elevated temperatures on CFRP Materials.............................20
2.4.2 Effect of elevated temperatures on epoxy and resin............................21
2.4.3 E bonded sheet concrete structures exposed to fire...........................23
2.5 The glass transition temperature for epoxy.....................................24
2.6 Summary and Conclusions........................................................25
viii


3. Performance of externally bonded CFRP-concrete Interface subjected to elevated
temperatures......................................................................28
3.1 General.......................................................................28
3.2 Experimental program..........................................................30
3.2.1 specimen preparation.........................................................31
3.2.2 Effective length of CFRP sheet..............................................32
3.2.3 Experimental phases.........................................................33
3.2.4 Heat application............................................................34
3.2.5 Instrumentation and testing procedure.......................................34
3.3 Test results..................................................................35
3.3.1 Failure point................................................................35
3.3.2 Thermomechanical load.......................................................36
3.4 Thermal propagation at mid-span of the concrete block........................40
3.5 Temperature dependent Models..................................................41
3.5.1 Thermal relaxation Model to 0.25 B type......................................41
3.5.2 Thermal relaxation Model to 0.5 B type......................................42
3.5.3 Thermal relaxation Model to 0.75 B type.....................................42
3.5.4 Thermal relaxation Global Model.............................................43
3.5.5 Thermal relaxation Model to Le..............................................43
3.5.6 Thermal relaxation Model to 1.25 Le.........................................44
3.5.7 Thermal relaxation Model to 1.5 Le.........................................44
3.5.4 Thermal relaxation Global Model.............................................45
3.6 Time logarithm Model...........................................................45
IX


3.6.1 Time logarithm Model 0.25B.................................................45
3.6.2 Time logarithm Model 0.5B..................................................46
3.6.3 Time logarithm Model 0.75B.................................................46
3.6.4 Time logarithm global Model with different CFRP Width......................46
3.6.5 Time logarithm Model Le....................................................46
3.6.6 Time logarithm Model 1.25Le................................................47
3.6.7 Time logarithm Model 1.5Le.................................................47
3.6.8 Time logarithm Global Model with different CFRP length.....................47
3.7 Summary and Conclusion.......................................................47
4. Performance of Externally bonded CFRP- RC beam Subjected to Elevated
Temperatures....................................................................107
4.1 General....................................................................107
4.2 Experimental program.......................................................109
4.2.1 specimen preparation......................................................110
4.2.2 Experimental category.....................................................Ill
4.2.3 Heat application..........................................................Ill
4.2.4 Instrumentation and testing procedure.....................................112
4.3 Test results...............................................................113
4.3.1 four points bending .......................................................113
4.3.2 three points bending......................................................114
4.3.3 Failure Mode..............................................................116
4.4 Thermal propagation at mid-span of the RC beam.............................116
4.5. Summary and Conclusion.....................................................117
x


5.1. Summary and Conclusion................................................151
References..................................................................154
Appendix
A...........................................................................157
B...........................................................................182
xi


LIST OF TABLES
Table
2.1 FRP Tensile Strength and Youngs Modulus (ACI 440.2R-08).................27
3.1. Concrete mix design.....................................................49
3.1a CFRP sheets sizes all unit by (in)......................................49
3.2. Compressive strength of concrete cylinders 28 days......................49
3.6 . Correlation between all parameters.....................................50
4.3.3- 1 four point bending test.............................................122
4.3.3- 3 three point bending test............................................122
xii


LIST OF FIGURES
FIGURES
3.2 a : specimens ready fortesting.............................................50
3.2 b : Applied thermomechanic load............................................50
3.3.1 result of three specimens of 0.25 B, (a) 25 C to (n) 175 C..............53
3.3.2 result of three specimens of 0.5 B, (a) 25 C to (n) 175 C...............56
3.3.3 result of three specimens of 0.75 B, (a) 25 C to(n) 175 C...............59
3.3.4 result of three specimens of Le, (a) 25 C to (n) 175 C..................62
3.3.5 result of three specimens of 1.25 Le, (a) 25 C to (n) 175 C.............65
3.3.6 result of three specimens of 1.5 Le, (a) 25 C to(n) 175 C...............68
3.3.7 (a) to (d) different ratio for 0.25B, 0.5B, and 0.75B.....................79
3.3.8 ((a) to (d) different ratio for Le, 1.25 Le, and 1.5 Le...................70
3.4.1: thermal propagation for block heated to 50C at: (a) to (k)..............71
3.4.2: thermal propagation for block heated to 75 C at: (a) to (k) ............72
3.4.3: thermal propagation for block heated to 100 C at: (a) to (k)............73
3.4.4: thermal propagation for block heated to 125 C at: (a) to (k)............74
3.4.5: thermal propagation for block heated to 150 C at: (a) to (k)............75
3.4.6: thermal propagation for block heated to 175 C at: (a) to (k)............76
3.4.7: thermal propagation for block heated to 50C at: (a) to (k)..............77
3.4.8: thermal propagation for block heated to 75 C at: (a) to (k) ............78
3.4.9: thermal propagation for block heated to 100 C at: (a) to (k)............79
3.4.10: thermal propagation for block heated to 125 C at: (a) to (k)...........80
xiii


3.4.11: thermal propagation for block heated to 150 C at: (a) to (k)..............81
3.4.12: thermal propagation for block heated to 175 C at: (a) to (k) .............82
3.5.1: compares between model and experimental for 0.25B: (a) to (k)...............85
3.5.2: compares between model and experimental for 0.5B: (a) to (k)................87
3.5.3: compares between model and experimental for 0.75B: (a) to (k)...............89
3.5.4: global model for different width: (a) to (k)................................90
3.5.4: compares between model and experimental for Le: (a) to ( k).................92
3.5.5: compares between model and experimental for 1.25Le: (a) to (k)..............94
3.5.6: compares between model and experimental for 1.5Le: (a) to (k)...............96
3.5.7: compares between model and experimental for 1.5Le: (a) to (k)...............98
3.5.8: global model for different length: (a) to (k)..............................100
3.6.1 temperature dependent For 0.25 B: (a) to (b) ...............................101
3.6.2 temperature dependent For 0.5 B: (a) to (b) ...............................101
3.6.3 temperature dependent For 0.75 B: (a) to (b)...............................101
3.6.4: global model for different width: (a) to (j)...............................103
3.6.5 temperature dependent For Le: (a) to (b) ...................................104
3.6.6 temperature dependent For 1.25 Le: (a) to (b)..............................104
3.6.7 temperature dependent For 1.25 Le: (a) to (b)..............................104
3.6.8: global model for different length: (a) to (j)..............................105
4.1a: Four points bending ........................................................119
4.1b: Three points bending .......................................................119
4.2: Beam section ................................................................119
4.2.1a: Test preparation .........................................................120
xiv


4.2.1b: Test preparation ..........................................................121
4.2.1c: Test preparation ..........................................................122
4.3: MTS setup.....................................................................122
4.3.1 (I): response of unstrengthen beam: (a) to (e) ..............................123
4.3.1 (II): response of strengthen beam: (a) to (e) ...............................124
4.3.1 (III): response of strengthen beam at 75 C: (a) to (e) .....................125
4.3.1 (IV): response of strengthen beam at 100 C: (a) to (e) .....................126
4.3.1 (V): response of strengthen beam at 125 C: (a) to (e) ......................127
4.3.1 (VI): response of strengthen beam at 150 C: (a) to (e) .....................128
4.3.1 (VII) compares temperatures and strain.......................................129
4.3.2 (I): response of strengthen beam at 75 C: (a) to (e) ......................130
4.3.2 (II): response of strengthen beam at 100 C: (a) to (e) ....................131
4.3.2 (III): response of strengthen beam at 125 C: (a) to (e) ...................132
4.3.2 (IV): response of strengthen beam at 150 C: (a) to (e) ...................133
4.3.2 (V): response of strengthen beam at 150 C at 45 mins: (a) to (e) ..........134
4.3.2 (VI): response of strengthen beam at 150 C at 60 mins: (a) to (e) .........135
4.3.2 (VII): response of strengthen beam at 150 C at 75 mins: (a) to (e) ........136
4.3.2 (VII) compares temperatures and Pu: (a) to (f)..............................137
4.4.1: thermal propagation for beam heated to 75 C at: (a) to (k) ................138
4.4.2: thermal propagation for beam heated to 100 C at: (a) to (k) .............141
4.4.3: thermal propagation for beam heated to 125 C at: (a) to (k) .............143
4.4.4: thermal propagation for beam heated to 150 C at: (a) to (k)................145
xv


4.4.5: thermal propagation for beam heated to 75 C at: (a) to (k) .............146
4.4.6: thermal propagation for beam heated to 100 C at: (a) to (k) ............147
4.4.7: thermal propagation for beam heated to 125 C at: (a) to (k) ............148
4.4.8: thermal propagation for beam heated to 150 C at: (a) to (k).............149
xvi


1. Introduction
1.1 General
Concrete is one of the most popular materials in construction. Since its composite of
inexpensive materials such as cement, aggregate, and water, it becomes a wildly used
material around the world. This composite material has advantages and disadvantages.
Because its very durable material, a lot of researches have been done to overcome the
disadvantages. For example, concrete weak in tension and strong in compression.
Therefore, Reinforcement concrete system has been created to overcome the weakness of
concrete. With rapidly development in construction, the concrete technology has to walk
parallel with this development. Therefore, the Prestressed concrete was created to
overcome the limit of reinforcement concrete span. Like this technique many
megastructures such as bridges, and garages can be built. Girders, beams, or slabs that
were built by using prestressed technique can cover longer span than reinforcement
concrete. These critical structures need very important maintenance, because there are
many factors such as corrosion and weather conditions. These factors cause one of the
most danger problem which deterioration. Therefore, the maintenance of these important
structures is very expensive. Because of these factors of deterioration, many researchers
had tried to find new technology or new material can strengthen the structures without
changing size of the structure member. According to Chen, Teng, 2003 in early 1990s,
there are new material which can defend this problem which is Carbon fiber-reinforced
polymer (CFRP). This amazing material can increase the capacity of the member without
changing the dimensions of the member. Briefly, Concrete technology has rapidly
developed due to the complexity of new structures. There are a lot of papers have been
1


published to cover these new techniques. In addition, CFRP has approved that it is very
light material that can overcome many rick factors.
Fiber-reinforced polymer (FRP) is a gorgeous material. It is consist of fiber and polymer.
Because of its advantages, it has become a perfect alternative strengthen material. FRP is
being noticeable by engineers in the early of 1990 (Chen and Teng, 2003). FRP has a lot
of pros such as light, noncorrosive and high tensile material. Based these advantages,
FRP approve that it is an efficient composite material. According to Lee, L. S., & Jain, R.
2009, to investigate if any composite material is a sustainable material, it has to follow
these factors, which are less resource using, environmental effect, human risks,
performance. For all these factors, there are few materials can satisfy these requirement.
There are some challenges for FRP to be sustainable material, but depend on a lot of its
advantages; FRP is an efficient composite material (Lee, L. S., & Jain, R. 2009).
Therefore, FRP has become the most popular strengthen material in construction. There
are different sizes and fibers in market. There are three popular fibers in construction,
which are Carbon fiber reinforced polymer (CFRP), Aramid fiber reinforced polymer
(AFRP) and glass fiber reinforced polymer (GFRP). The First type is CFRP. This kind is
made from carbon fiber. From table 2.1, CFRP shows the highest tensile strength and
Youngs Modulus. In addition, CFRP is the highest stiffness, excellent fatigue, lower
creep and relaxation (Carolin, 2003). The second common type is glass fiber reinforced
polymer (GFRP). This kind is widely used because of its advantages such as, cheaper
than CFRP, high resistant to chemicals. There are three common types of glass, which are
E-glass, C-glass, and D-glass (Carolin, 2003). The third type is Aramid fiber reinforced
polymer (AFRP). Aromatic polyamide (Aramid) has different brands in market depend
2


on the name of fiber such as, Kevlar, Twaron, and Technora. Furthermore, AFRP is
lower cost than CFRP, and very light material. However, it shows some issues with
relaxation (Carolin, 2003).
FRP has a number of advantages. It has low weight compare with steel, concrete, or
wood. Also it shows high tensile strength, high durability, and noncorrosive. Therefore,
any strengthen structural by FRP would avoid a problem of deterioration (Lee, L. S., &
Jain, R. 2009). On the other hand, the normal structural member has shown a lot of the
cons such corrosion, and deterioration. Therefore, a number of engineers and researchers
have done a lot of papers to study and investigate FRP as a structural element. For
Example, Erki, M. A., & Rizkalla, S. H. (1993) illustrated using CFRP instead of
reinforcement steel. The authors concluded that its difficult used CFRP as reinforcement
because low failure strain and very high cost control the design. In addition, many
researches have been published to investigate the performance of FRP as strengthen
material. According to ACI, 440R, (2002), FRP can be used as maintenance and
strengthening material. In addition, there are two main FRP systems, which are NSM
strengthening system, and Externally bonded strengthening system. The report illustrated
the different types of strengthening such as flexural strengthening and shear
strengthening (ACI, 440R, 2002).
1.2 Research significance and objectives
For last 20 years, the using of FRP as has been increased because of some factors such as
corrosion and fire. Therefore, a number of papers have been published to start using FRP
as construction or repair material. Also, a lot of engineers and scholars have been
investigating and trying to find the efficient way to use FRP in structure filed. In addition,
3


there are few published papers that study and investigate the behavior and performance of
NSM CFRP exposed to elevated temperatures. For example, Siriwardanage has studied
and investigated the performance of NSM CFRP exposed to elevated temperatures at
2014. He also, focused on the chemical of the epoxy that exposed to high temperatures.
In addition, there are some papers that investigate not only the failure of different kind of
epoxy exposed to high temperatures but also, the different isolated system. However,
studying and investigating the bond performance of an externally CFRP sheet
strengthening system at elevated temperatures has not been well researched. Therefore,
This thesis is focusing on the bond performance of CFRP exposed to elevated
temperatures. This experimental program has two main phases. The first phase is to study
the performance of externally bonded CFRP-concrete blocks interface subjected to
elevated temperatures. In this phase, more than 144 concrete blocks were exposed to
elevated temperatures ranging from 25C (77F) to 175C (347F). The second phase is
to investigate the performance of RC beam strengthen by CFRP sheet exposed to
elevated temperatures ranging from 25C (77F) to 175C (347F). The objective of this
thesis is illustrated below.
Studying and investigating experimentally the behavior and performance of
strengthen concrete system. The performance of different CFRP sheet bonded
area is investigating.
More than 144 concrete specimens were exposed to elevated temperatures ranging
from 25C (77F) to 175C (347F). 30% of ultimate load was applied to the
concrete blocks.
Focusing on the temperatures higher than Tg is very important since epoxy is
4


changed to rubber condition because of high temperatures.
Thermal propagation was captured be using IR camera. The aim of using IR
camera is to investigate the relationship between the specific temperature and
specific points inside the tested block or beam
High temperatures change epoxy state, which will reflect to the performance of
not only the bond strength, but also to the whole strengthen system negatively.
Therefore, a number of beams were investigated experimentally to figure out the
relationship between elevated temperatures and the performance of beams.
1.3 Thesis Organization
Five chapters are in tis thesis. Literature review of CFRP is illustrated in chapter two.
Chapter two demonstrate the strengthening systems for concrete structures, FRP
applications and techniques, previous applications on externally bonded sheet, Effect of
Elevated Temperatures on CFRP Materials, and e glass transition temperature for epoxy.
Chapter three presents the experimental programs of strengthen concrete blocks exposed
to elevated temperatures. Chapter three investigates the behavior and performance of
concrete specimens. Also, thermal propagation is capture in chapter three. Modeling the
behavior of the specimens is taking a large area in the chapter.
Reinforcement concrete beams strengthen by CFRP sheet is illustrated in Chapter four.
All beams were exposed to elevated temperatures. The behavior of the beams is being
focused on the chapter four.
5


Chapter five presents summary and conclusion of entire thesis. Also, some
recommendations based the experimental program is illustrated in chapter five.
Appendix A presents all tables of results of concrete blocks and RC beam strengthen by
CFRP
Appendix B presents pictures of all process of experimental program and thermal
propagation.
6


2. Literature Review
2.1 Strengthening systems for concrete structures
Civil engineering has faced a challenge of rehabilitation of deterioration of
infrastructures like the beams, girders, marine structure and even roads. These structures
may be deteriorating because of different reasons. The reasons can be due to age, natural
disasters such as earthquakes, poor maintenance, poor environmental conditions and even
poor initial design. This has raised a need to upgrade the civil engineering structures.
However, the upgrades come with demands that are increasing. An example is the
increased traffic conditions that in some cases do not go together with the initial design
(De Lorenzis, Nanni, & La Tegola, 2000). Due to the above issues, it is of great
importance that the rehabilitation of the civil engineering structures should be addressed
The traditional methods of reinforcing concrete structures include, steel plate
bonding and concrete column jacketing. When the steel plates are used in bonding, they
are known to increase the flexural capacity of concrete members at the tension zones.
Steel has been used for a long time to strengthen the structures especially concrete
(Hollaway&Leeming, 1999).
Despite steel increasing the flexural capacity of the structural members, it has faced many
challenges that have rendered it not effective for use as a material for strengthening. First,
the bond between steel and concrete deteriorates over time (Chen &Teng, 2001). There
are also difficulties that have been experienced during the installation of steel such as the
fact that heavy machines are needed in installing. As a result of these drawbacks,
researchers have come up with FRP strengthening as a method of replacing steel that has
been in existence for long (Chen &Teng, 2003).
7


2.2 FRP
FRP (Fiber Reinforced Polymer) is a polymer that has been reinforced using a
fiber. The main aim of using the fiber is to take part in carrying the strength and stiffness
in one direction. The FRP are under the class of materials called the composite materials.
The composite materials do not change their physical or chemical compositions in the
combined state. FRP are very different from the other construction materials like
aluminum and steel. Steel and aluminum are isotropic while the FRP are anisotropic. The
properties of FRP are directional. This means that the best mechanical properties of the
FRP are in the direction in which the fiber is placed (Kim, & Mai, 1998). .
The FRP have composite components. First are the fibers. The properties of the
composites are mainly determined by the fibers. In civil engineering, there are three types
of fibers, which are very dominant. The three fibers are aramid, glass and carbon (Lee &
Jain, 2009). Their naming is always done by the fiber that has been used to reinforce. The
different types have the fibers when compared to the ordinary steel. The main difference
between the three types of fibers is the tensile strain and the stiffness.
Another composite is the matrices. The main function of the matrices is to ensure
that the forces are transferred along the fibers. The matrices also protect the fibers from
the environment. Thermosets are exclusively used in civil engineering. The two common
matrices used are epoxy and vinyl ester. Epoxy is preferable but more costly to vinyl
ester.
There are different types of FRP. Those that are used in civil engineering are only
three, which are glass fiber, aramid, and carbon fiber.
8


The glass fibers are majorly made by mixing limestone, folic acid, silica sand and
some other minor ingredients. During the making of these fibers, the mix is heated to a
temperature of 1260 C. The glass that is in molten form is allowed to flow through holes
that are made on a platinum plate. The strands of the glass are left to cool, gathered and
then wound. The fibers are drawn so that the directional strength is increased. The fibers
are made in different shapes and forms so that they can be used in the composites. The
glass produced fibers have a low susceptibility when exposed to moisture; they are good
electrical insulators and have very high mechanical properties. Glass happens to be a
good impact resistant. However, glass weighs more when compared to carbom and
aramid. The glass fibers have properties that are better that that of steel in some given
forms.
The second type of fiber polymer is the carbon fiber reinforced polymer. These
types of polymer always have a high modulus of elasticity that ranges from 100-140 Gpa
(Bakis, Ganjehlou, Kachlakev, Schupack, Balaguru, Gee & Harik, 2002). The carbon
fiber is non-reactive and does not absorb water. They are very excellent when it comes to
withstanding fatigue. They do not show any signs of relaxing nor do they stress corrode.
When in direct contact with steel, carbon fiber can give a galvanic corrosion. This is
because the carbon fibers are electrically conductive.
The third type of reinforced fiber is the aramid fiber reinforced polymer. The
word aramid is the shortened form of the word aromatic polyamide. Aramid is mainly
used for helmets and the bullet proofs. This is because it has very high fracture energy.
These types of fibers are not highly used in civil engineering. This is because the aramids
9


are sensitive to high temperatures, ultraviolet radiation as well as moisture. These types
of fibers do not have any problem with stress corrosion and relaxation.
There are different reasons why FRP have become very common especially in
civil engineering. Some of the reasons include the fact that they can absorb energies. The
corrosion potential in the fibers is also reduced. The fasteners and the joints are
simplified while using the fibers or even eliminated. The FRP can give stiffness to
density ratio of between 4 to 5 times better than steel or aluminum. The materials also
have a high fatigue endurance limits. These advantages contribute to the high usage of
FRP in civil engineering structures (Chen, &Teng, 2003).
2.2.1 FRP applications
The FRP are being used as an enhancement for the structural elements because of their
recommended properties. The FRP are also being used as substitutes for the traditional
engineering materials such as steel and aluminum (Bakis.,Ganjehlou, Kachlakev,
Schupack, Balaguru, Gee &Harik, 12002). The reason behind the use is, FRP do not
corrode like steel, they have a specific stiffness, are lightweight, and they show a high
specific strength (Carolin, 2003). The composites can also be structured to fit the
performance that is required (Lee, & Jain, 2009). Because of these characteristics FRP
has been included in rehabilitation and construction of structures through its use in
reinforcing concrete (Kim, & Mai, 1998).
The carbon fiber reinforced polymers are very strong and contain carbon fibers.
The carbon fibers are classified based on the strength, modulus, and the final heat
treatment.
10


Based on the carbon fiber properties, the carbon fibers can be put into five groups
that include the SHT (Super high tensile type) this have a tensile strength greater than 4,5
Gpa (Benedikt, Goodall, & Society of Plastics Engineers 1998). The second one is the
HT (high tensile and low modulus) type. The IM (intermediate modulus), the HM (High
Modulus and lastly the ultra-high modulus (UHM).
Basing the classification on the precursor fiber material, there are six classes, and
they include the pitch based, isotropic pitch based, rayon-based, gas phase grown and the
PAN base carbon fibers. Another classification is on the final heat treatment. Under this
classification, there are only three types. The first one is the high heat treatment; type 2 is
the intermediate heat treatment carbon, and the last type is the low heat treatment carbon
(Erki, &Rizkalla, 1993).
2.2.2FRP techniques
The techniques used in strengthening are concerned with the application of FRP
to an existing concrete substrate as a structural reinforcement. Taking into account all the
requirements and the specifications, the technique can be applied under different
conditions and at different places of the structural member
The first technique is the basic technique. In this technique, wet lay-up is applied
manually. The main feature that distinguishes this technique is that the principle tensile
stresses and the fibers of the FRP are parallel to each other. The manual application of the
FRP reinforcement to a member that is already in existence is what is described as the
basic technique. Epoxy that is a two-part cold cured bonding is used to achieve the
bonding (De Lorenzis, Nanni, and La Tegola, 2000). The basic technique involves three
11


main acting elements that include the substrate. The existing structure and the FRP
composite are bonded to enhance strength. The type of material of that structure is what
is called the substrate. Therefore, the behavior of the structure that is strengthened
depends mainly on how good the concrete substrate is and the way the concrete surface
has been prepared. The original conditions of the concrete surface should, therefore, be
known in terms of unevenness, strength, carbonation, imperfections humidity and if
possible the corrosion of the internal steel.
Secondly is the resin. For a particular FRP strengthening, there should be a
particular resin for it the resins in most cases are specified by the manufacture so that the
can meet the necessary requirements for the installation system. The importance of the
bonding agent is to assure the bond between the FRP and the substrate reinforcement
(Binetruy, Chinesta & Keunings, 2015).
The FRP composites can be categorized differently depending on their application.
One is the laminate. The laminates have their final stiffness strength and shape. They are
always available in strips that are similar to those of steel. For the laminates, the resins
present only provide the bond between the concrete and the strip only. Another type is the
fabrics the fabrics are provided as dry fiber. This means that they do not have any resins
inside unless they are applied. The amount of resin that is available is insufficient for
polymerization. For the fabrics, the adhesive is important to bond the concrete and the
sheet and also to impregnate the sheet.
The second technique is the special techniques. Because of the basic requirement
of FRP some special techniques have been put in place to speed the speed of construction.
The first special technique is the automated wrapping. Wet fibers are made to wind
12


continuously around structures with a slight angle. The technique has a main advantage
of fastness. Another special technique is the prestressed FRP. Bonding a prestressed FRP
externally onto the surface of concrete may be more favorable. Analytically and
experimentally, it has been proven that this method is an advancement to the FRP
strengthening technique (Li, & Shchukin, 2012). This method, however, has some of the
advantages and disadvantages.
The advantages of these techniques include the formation of cracks is delayed in
the shear span. Stiffer behavior is provided, and the deflection at the early stages can be
controlled. The already existing cracks can be closed using the technique. Also, the shear
resistance of a member is improved. Because of the reduced cracking, the technique
improves the durability of the structural member (Tan, 2003).
The technique also has some of the disadvantages. First, the technique is
expensive that the normal strip bonding. The time of operation is also longer. Lastly, the
technique requires that the equipment used to push the strip to the soffit of the beam is
expected to remain in place until the resins have sufficiently hardened. The main problem
with this technique that there can be the failure of the beam because of the prestressing
force which is applied at the two ends of the beam. The design, therefore, requires special
attention.
Another important technique under the special technique is the in site fast curing
using the heating devices. The curing time is reduced in this technique by using heating
devices to cure the cold bond interface. This technique is mainly applied in cold weather
conditions. Heating systems such as electrical heaters and heating buckets are applied.
The technique is also very important when rapid strengthening is required.
13


The fourth special technique is the use of prefabricated shapes. This technique
reduces the time of installation and gives room for better quality control. These types of
FRP are developed as straight strips but other forms are also available in the market like
shells and angels. The systems can be used in the applications where wet lay-up systems
are used (Wuertz, 2013).
Lastly, there is the FRP impregnation by vacuum technique. This system can be
compared to the wet lay-up and is common in the plastic industry. The concrete substrate
is prepared before strengthening through grinding, sandblasting or water jet blasting. The
surface is dried and cleaned before the premier is applied. After the premier is cured, the
fibers are placed in directions that are predetermined. In this technique, the fabrics have
channels through which the resins flow. A bag that is vacuum is placed on top of the
fibers the edges of the bag are then sealed and a vacuum pressure applied. The bag has
two holes, one of the holes is used to apply vacuum pressure, and the other hole is used
for the injection of the resins. To achieve a good vacuum pressure, a special type of
epoxy putty is used in the sides of the beams. The advantages of this method over the
traditional methods are that the quality of composite can be improved, and the hand
contact with the epoxy can be avoided. Waste is also reduced at the work site.
2.2.3 NSM FRP strengthening system
In addition to the bonding that is done externally, FRP reinforcements can be put
into the grooves that are cut into the given structural members. This application is called
NSM (Near surface mounted). The use of the technique of NSM reinforcement was first
discovered in Europe. The technique was used to strengthen reinforced concrete in the
1950s. In 1940, as made of reinforced concrete was to be upgraded because of the
14


negative moment region that had been caused by excessive settlement of the steel cage
when construction was taking place. The upgrade was achieved through inserting some
steel bars in grooves that were made in the concrete surface that was filled with cement
mortar (Blaschko, 2003).
The near surface mounting technique has many advantages when compared with
the external bonding technique. The bond surface that is larger ensures there is better
anchorage capacity. Higher resistance is provided against peeling off. A higher
percentage of the tensile strength can be mobilized. Apart from grooving there is no other
preparation that is required. The installation time is therefore reduced. The FRP that are
reinforced due the mounting setup is protected from mechanical influence by the
surrounding concrete. This technique is therefore very attractive for straitening especially
in the negative moment region. This type of strengthening provides protection against
vandalism, ultra violet rays, fire and even elevated temperatures (Bakis, et al., 2002).
The NSM technique has its disadvantages also. The debonding failure mode is
more common in cases where more than two grooves have been cut for strengthening
with the NSM bars in a beam that has limited width due to overlapping of stress. Due to
the limited width, there is an opportunity of edge breaking along the concrete section. For
this reasons, enough width of the beam should be provided for the NSM technique whose
main aim is to come up with a proper clear spacing between any grooves that are near
each other. In some cases, an updated NSM approach is needed.
15


2.3 Externally bonded sheet strengthening system
The process of replacing structures that already exist with new structures is in
most cases economically cost effective. It is therefore of great importance that a solution
for strengthening and repairing the structures is found. Strengthening a structure that
already exists is more complicated than a new structure. Traditional methods of
strengthening have been used over a long period such as the post-tensioned cables, which
require a lot of space.
The FRP in the last few years has offered a good alternative in various
engineering structures. Due to this improvement research has led to different techniques.
One of the techniques is the externally bonded reinforcement technique. The EBR is one
of the most common methods used to strengthen structures made from reign forced
concrete. While using this method, the FRP sheet is bonded adhesively to the tension face
of the member concrete. The surface preparation is mainly done to do away with
contamination, remove the surface layer that may be weak, and polish the surface of the
concrete. The polishing is done to promote the adherence capacity.
The advantages of this system include the easy and quick installation, the
performance costs that are quite low. There is no need for any specific labor skills while
using this system and the strengthened structures can be used immediately.
The system also has it disadvantages that include the brittle failure mode. The
brittle failure mode is due to the premature debonding of the FRP sheet from the substrate
of the concrete. Another disadvantage of the system is that the FRP materials are
vulnerable against the environmental conditions like abrasion, acidic conditions, and
16


mechanical impacts. The appearance of the structure can also be changed because the
changes that are caused
2.3.1 Externally bonded sheet techniques
To postpone and eliminate the debonding of the FRP sheets, the grooving
technique was invented. This technique was the one later named as externally bonded
reinforcement on grooves (BROG). In this technique, the grooves are first cut on the side
of the concrete member with tension. The air jet is then used to clean the grooves and
filled with the epoxy resin. The surface that is saturated with the epoxy resin is then filled
with the grooves, and the resin that is in excess is removed. From research and
experiments, it is very clear that the longitudinal grooves are effective compared to the
diagonal and the transverse grooves (Galbreath, 1966).
Another technique is the EBRIG method. The grooving method was improved by
penetrating the FRP sheets that were used in the EBROG into the groove. The method
was the named EBRIG (externally bonded reinforced in grooves) this method promoted
the structural performance because it provided a larger contact area between the concrete
layer and the FRP. The method also modified propagation, promotes the structural
performance and crack initiation (mostfineiad and Shameli, 2013). This method is proved
to be better than EBROG.
Also, there is the MF-EBR method. The (MF-EBR) mechanically fastened and externally
bonded reinforcement is a technique that is based on the MF-FRP. It combines two
methods of the EBR and the MF-RFP. One of the advantages of these methods is that it
does not need any special labor skills and surface preparation is not required. It also
increases the load carrying capacity up to a level of 87%. The strengthened structures can
17


also be used immediately. Lastly, the technique raises the ductility index compared to the
original methods that have been used for a very long time (Cruz, et all, 2012).
2.3.2 Previous applications on externally bonded sheet
The FRP systems have many applications, especially in the civil engineering
structures. The systems have for a long time been used to restore the strength of structural
members that deteriorated. They can also be used in increasing the strength of the
structural member whose load carrying capacity has been increased. Before selecting the
type of system that should be used, the professional designer should determine if the FRP
system is applicable.
In assessing the suitability of an FRP system, a thorough assessment should be
done by the silenced design professional that includes establishing the characteristics of
the existing structure. Such characteristics involve the carrying capacity and the concrete
substrate (Hollaway & Leeming, 1999). The overall assessment should include a review
of the designs that already exist, structural analysis, and other guiding document. The
system has been in use for a very long time and especially in the strengthening of the
civil engineering structures.
2.3.3 Previous research studies on externally bonded sheet FRP strengthening
system
With regards to the performance, the NSM strengthening systems have been well
researched. The systems have been proven through experiments to be an effective. This is
a method that is an alternative to the externally bonded strengthening system. The
externally bonded systems have been used highly on aged prestressed girders
(Hassan,&Rizkalla, 2002).
18


The externally bonded FRP have been observed by many researchers to have a
debonding failure. The debonding failure was mainly observed at the termination point of
the sheets for the strengthened systems that had a short span (Hollaway & Leeming,
1999). And those that had a long span the failures were observed at the mid-span. There
are different models that have been proposed by different researchers who predict the
failure loads of the concrete members who have been reinforced through the use of FRP
due to the debonding. There is very little research however that has been done on the
debonding mechanism on the mid-span.
2.4 Fire endurance of concrete Structures
Fire resistance is the ability that the structural members possess of withstanding
fire or giving protection from the fire. This ability is not limited to continue to perform a
given structural function or to confine a fire. Unlike the structures that are steel framed, it
is difficult for one to analytically determine the fire endurance of a concrete building that
is reinforced this is because there is little information that has been given to the effect of
high temperature on the concrete properties. This is especially the deformation such as
creep expansion and shrinkage.
One of the reasons why concrete is a preferred building material over the other
building materials is the property of fire resistance. The concrete structures must,
however, be designed for the purpose of fire effects. The structural members of the
buildings should be in a position of withstanding the live and dead loads without
collapsing even when exposed to fire. This is because fire decreases the strength and the
modulus elasticity of various structures both steel and concrete reinforcement. Concrete
19


does not burn depends on the increase in temperature and the insulating properties of the
concrete.
The change in which the properties of concrete change are dependent on the type,
of course, aggregates used. The reinforcing steel is according to research is more
sensitive to temperature than concrete. From experiments, the reinforcing bars do not lose
much yield strength up to a temperature of 8000f. The prestressing strands start losing
their strength at about 5000f. The fire resistance is different between the prestressed and
the non-prestressed elements as well as the other types of concrete (Kodur, Bisby& Green,
2007).
The performance requirement during a fire exposure is the load carrying capacity.
The fire rating that is always needed by the building codes is the time that the structural
element can support the load when it has been exposed to standard fire.
2.4.1 Effect of Elevated Temperatures on CFRP Materials
Despite the good characteristics of FRP that have allowed them to be used in the
structures, there is a weak link in the FRP strengthening application especially at the
elevated temperatures even though the fibers alone are in a position of retaining the
strength. Although a lot of research has been done on the bond behavior at elevated
temperatures, information on the behavior of the bond CFRP system when subjected to
elevated temperatures has remained limited (ACI Committee 216, & Fire Resistance and
Fire Protection of Structures. (1982).
Most of the FRPs are combustible because of their polymer matrix. This leads to
increased spread of frames and evolution of toxic smoke. Also, the adhesives and the
20


matrices that are commonly used lose stiffness and strength above their glass transition
temperature (Galbreath, 1966).
2.4.2 Effect of Elevated Temperatures on epoxy and resin
Change in temperature has an effect especially on the properties of the
thermosetting polymers and the epoxies. Before being cured, an epoxy is a composition
of a curing agent and a resin. After polymerization, the entity changes into an organized
crystalline structure that is referred to the glassy state. In the glassy state, the molecules
can vibrate but cannot move because they are locked in one position. As the temperatures
rise, the molecules become more lose, and they start moving apart. The polymer finally
changes state to a rubbery state. This transition takes place over a range of temperatures
(Matsumoto & Iwate ,2013).
As the temperatures are increased, the thermosetting polymers show a change in
their physical state, which includes the tensile strength, heat capacity, thermal expansion,
electrical properties and the modulus. One of the changes that can be highly observed is
the change in the linear coefficient of thermal expansion. As the epoxy moves through
the tg. Its CTE at a very high rate until the value becomes tree to five times higher than
the given value below the tg range. The material properties at these temperatures are very
different from the properties that are observed below the tg temperatures. The changes
that occur to the epoxies are not permanent and are highly dependent on the amount of
time that the tg temperature is exceeded. The strength profile of an epoxy is restored as it
returns to its original temperatures. Understanding the nature of this transition is
important especially to the engineers so that they can be in a position of choosing the best
system for any specific application (Yourdkhani, 2014)
21


The (Tg) glass transition temperatures is one of the very crucial properties of an
epoxy. This is the temperature in which the polymer changes from a hard glassy material,
to a material that is very soft and rubbery. Epoxy materials do not reflow or melt when
exposed to temperatures. This is because the epoxies are thermosetting materials, and
they cross-linked chemically during the curing process. Epoxies only undergo a phase
change and become softened when exposed to temperatures.
The glass transition temperature is a temperature range where the thermosetting
polymer is changed from a glassy or rigid state to a state that is rubbery. Tg is not
discrete but it is a continuous range of temperatures.to come up with the Tg, several
factors have to be considered. One is the chemical structure of the epoxy resin. The type
of hardener is also considered and the degree of cure of the epoxy resin. The epoxies are
in a position of retaining the structural integrity and the adhesive strength after being
exposed to the high temperatures (Song, Casern, & Kimberley, 2015).
Another term that is used in the behavior of epoxy in temperature is heat
deflection under load (HDETL) this term is always shortened as (NDT) heat deflection
temperature. This is a term that is used in the whole industry to give the characteristics of
the thermal behavior of many resin systems. This test is the one that determines the
temperature upon which a bar cured of epoxy. Each of the two temperatures is very
important in the use of the epoxies. The temperatures assist in the design and engineering
works.
2.4.3 Externally bonded sheet strengthened concrete structures exposed to fire
The steel members in most cases require protection so as to preserve the strength
in them in case of a fire event. Concrete that is FRP strengthened require protection to
22


prevent combustion of material, maintain strength and preserve the existing bond
between them and the substrate. The use of the FRP in design and engineering comes
with some obstacles. One of the concerns that have been highly considered in research is
the performance of the sheets in elevated temperatures. The FRP have an organic
polymer matrix. This matrix makes the susceptible to combustion whenever that is
exposed to the high levels of temperature. When the Tg has exceeded the matrix of the
polymer changes and becomes runny and soft. This reduces the strength.
Thermomechanical behavior of CFRP strengthened concrete members is unknown.
However some research that has been done shows that the FRPs lost about 50 % of their
strength at the temperature of 2500 C and 3250 C the stiffness of these materials
suffered losses that are negligible from the temperature of 4000 C and reduced rapidly
above these temperatures (Song, Casern, & Kimberley, 2015).
The insulated beams have shown fire endurance that is satisfactory. According to
research, beams that are insulated have a fire endurance of about 81 minutes. The
insulated beams on the other hand had a fire endurance of 146 minutes. The endurance of
the CFRP insulated beam is larger than that of an RC bam that is not strengthened. Once
the Tg of the FRP is reached, the load bearing contribution that was given by the FRP is
highly reduced. Overall, the fire endurance of the FRP sheet is not that sufficient.
The performance of the FRP strengthening methods is mainly dependent on the
bond between the FRP and the reinforced concrete. The bond between the two is,
however, susceptible to the environmental factors and fractures like humidity,
temperature, and corrosive materials. Thermomechanical behavior of CFRP strengthened
concrete members is unknown.
23


2.5 The glass transition temperature for epoxy
The glass transition temperature Tg, for any given compound, is the temperature
that represents the range over which an epoxy that has been cured to change from a hard
glassy state to a rubbery and softer state. There are three methods that have been used by
the researchers to determine the glass transition temperatures (Wuertz, 2013). The
methods include thermo mechanical analysis, dynamic mechanical analysis and the
differential scanning calorimetric. Each of the methods produces a very different result
and also measures a very different phenomenon that is a characteristic of the phase of
transition.
Under the differential scanning calorimetric, the Tg is identified by observing the
change that takes place in the heat capacity of the epoxy as the temperature is increased.
The principle applied here is that when a material is undergoing a state transition, less
temperature is supplied to maintain it at its temperature. In this method, a small is heated
together with another sample as the control experiment. The difference of heat flow
between the samples is observed. The Tg is given as the temperature in which the
inflection point occurs (MacKenzie, Mulkem, Beck, & U.S. Army Research Laboratory,
2001).
Another method is the thermal mechanical analysis. This technique is mainly used
to come up with the coefficient of thermal expansion of the material; the Tg of the
material can be determined. The principle that is applied in this technique is that when a
material is transiting from a hard state to a rubbery state the changes occur on a molecular
level, which results in increased movement. During this phase transition, the coefficient
of thermal expansion also increases in a noticeable way.
24


The last method is the dynamic mechanical analysis. This technique is used to
characterize the viscoelastic properties of polymer materials. The principle used in this
technique is that at the Tg, the damping and stiffness of a polymeric material change.
This technique is more accurate compared to the other techniques, but it requires a
machine sample that is precise with a uniform thickness.
2.6 Summary and Conclusions
Composites have been used highly especially in civil engineering in the past years.
The early application of the FRP is dated back to the 1970s. The early applications of
these composites were not satisfactory. The application techniques of the FRP have been
improved over time. In the current world, the FRP are highly used in the construction of
new structures and also the strengthening and rehabilitation of the existing structures. The
infrastructure that is deteriorating needs to be rehabilitated. The FRP have been adapted
by most civil engineers to address this problem. This is because of their high strength,
light weight and resistance to electrochemical corrosion, the ease of installation also
makes the use of FRPs effective for engineering works.
Despite the advantages that are associated with the FRPs, they can be degraded
when exposed to very high temperatures. This makes their uses especially in the
residential building a bit of a challenge. While the other materials are also susceptible to
the fire degradation, research has been done on them, and the results have been included
in different building codes and fire safety codes. The way the FRP materials behave
under fire has not been investigated thoroughly and the way these materials behave in
elevated temperatures is unknown.
25


Table 2.1 FRP Tensile Strength and Youngs Modulus (ACI 440.2R-08)
FRP Type Young's Modulus (GPa) Tensile strength (MPa)
CFRP 100-140 GPa 1,020-2,080 MPa
GFRP 20-40 Gpa 520-1400 MPa
AFRP 48-68 Gpa 700-1720 MPa
26


3. Performance of Externally bonded CFRP-concrete Interface Subjected to
Elevated Temperatures
3.1 General
The deterioration of bridge elements is an enormous issue facing the U.S
economy, especially the cost of maintenance. Therefor, the structural elements such as
slabs, beams, and girders are usually needed to strengthen. Externally- bonded carbon
fiber reinforced polymer (CFRP) laminates has been widely used to strengthen and
upgrade the deteriorated members. There are two different types of strengthening
techniques, which are Externally laminates and near surface mounted strengthening
system. Because of its benefits such as corrosion resistance, and high tensile strength, it
has become one of the most common techniques for strengthening structural elements.
Concrete surfaces face a lot of different situations and weather conditions. Also, in
strengthen structural members; the CFRP faces the same conditions that concrete has
faced such as raining or fire. Under these conditions, strengthen structural members
might not work efficiency or in some situations the structure will be unsafe. One of the
most danger environmental conditions is fire. Fire might affect the material properties
and causes deterioration to the whole structure. Therefore, fire is an important factor that
should be study and investigate.
On externally- bonded CFRP strengthen members there are three elements, which
are main member, epoxy adhesive, and CFRP sheet. Main member can be Concrete or
steel. Fire can change the CFRP and epoxy adhesive properties because it is a polymer
material. Polymer material has a thermal limit. If the material reaches the limit, the
material proprieties will change and will act as an elastic behavior. The thermal limit
called the glass transition temperature (Tg). According to Blontrock et all, 1999, the glass
27


transition temperature (Tg) of Epoxy resins has range of 50 C to 90 C. Therefore, it is
important to analyze and investigate the flexural performance and relaxation of the
strengthen members due to different temperatures, which are below and great than glass
transition temperature (Tg).
External bonding of FRP sheet plate- has become very popular. Many concrete
structures such as slabs, beams, and columns have been strengthened by CFRP external
bonded sheet. As it mentioned in chapter 2, Maintenance is very expensive specially
Hugh and critical elements in cities such as bridges. Many laboratory researches have
approved that using carbon fiber reinforced polymer (CFRP) increase the capacity of the
concrete members. However, a few researches have focused on performance of the
strengthen members and the effect of temperature during time. This research is focusing
in two parts. The first part is to analyze and investigate the flexural performance of the
strengthen members to elevated temperatures ranging from 25C (77F) to 175C
(347F). This experimental program focus on investigating the behavior of the CFRP that
exposed to elevated temperatures. The experimental program has two main categories.
The first category is different CFRP sheet width. In this category, there are three types.
First type is 0.25B. The bonded area of this type is 1 by 4 (25 mmXlOO mm). The
second type is 0.5B. The bonded area of this type is 2 by 4 (50 mmXlOO mm). The
tired type is 0.75B. The bonded area of this type is 3 by 4 (75 mmXlOO mm). Second
category is different CFRP sheet length. First type is Le. The bonded area of this type is 2
by 3.6 (50 mmX87 mm). The second type is 1.25 Le. The bonded area of this type is 2
by 4.5 (50 mmXl 14 mm). The tired type is 1.5 Le. The bonded area of this type is 2 by
5.4 (50 mmX137 mm) Figure 3.1a. The experimental program studies the performance
28


of the CFRP glued with concrete blocks by epoxy and subjected to elevated temperatures.
The size of the concrete block is 150 mm long by 100 mm width and 75 mm height. The
Mbrace epoxy adhesive was used for the two different categories.
3.2 Experimental program
More than (144) concrete blocks were prepared with compressive strength, f c, of
20 MPa (2,900 psi). In addition, the ACI standard 211.1 was followed to select the
properties of concrete Figure 3.1. There are nine steps to design the mix of concrete. The
dimensions of bricks long, width, and thick are 6 (150 mm), 4(100 mm), and 3(75
mm), respectively. After 28 days from casting the bricks, CFRP sheet has clued by Epoxy
Adhesive. The MBrace saturant PTA and MBrace saturant PTB were used as an epoxy
adhesive. The glue is composite of two parts, which are blue resin and hardener.
According to Mbrace (2007), the weight ratio of resin to hardener has to be 3:1. In
addition, the epoxy adhesive required 7 days curing to make sure it reaches the maximum
strength bonded. The thermal conductivity of this material as 1.45 Btuin/hrft2I>F
(0.21 W/m bK) and the glass transition temperature (Tg) is 71C (163F) (MBreace,
2007). The Ultimate tensile strength (fepx) and corresponding modulus (Eepx) are 55.2
MPa and 3034 MPa, respectively. There are six different sizes of CFRP sheets. Three of
them are bonded with constant length and different width. The next three categories are
bonded with constant width and different long. 7 day is needed for curing after bricks
bonded with the CFRP sheets. The next step is finding the failure point of each category,
and calculates 30 % of the failure to be the maximum point to study and investigate the
performance of the bricks. The research is focusing on studying different temperatures
29


ranging from 25C (77F) to 175C (347F).
In summary the test setup had four steps:
Step 1: casting Concrete and 28 day curing
Step 2: Bonding six different sizes of CFRP sheets to concrete with by Epoxy
adhesives.
Step 3: A seven day is enough for curing the blocks at room temperature to allow
the epoxy reaches the full strength.
Step 4: Putting the concrete blocks to thermal distresses ranging from 25C (77F)
to 175C (347F) while it is applied to tension with a constant load, which is 30 %
of the failure load figure 3.2 a.
3.2.1 specimen preparation
There are three elements was prepared to create the specimen. First, concrete was
mixed and followed by the ACI 304R specifications. The required concrete strength of
concrete is 20 MPa. It is normal concrete, which consist of cement, water, fine aggregate,
and course aggregate. Depending on ACI specification, there are 6 cylinders with
diameter and height, 100 mm and 200 mm, receptively. These cylinders were cured at
curing room for 28 days, and three of them were tested by compression strength machine
on the 7th day and the remain at 28th day Figure 3.2. The results of the compression
strength are shown in table 3.2. The concrete was mixed on cloudy morning day. The
temperature of water is 25 5 C. In addition, concrete was casted on steel mold. The
30


dimension of the concrete block is 100 mm, 75 mm, 150 mm, width, height, length,
respectively. All concrete blocks cleaned and smoothed before doing the second phase.
Secondly, the epoxy was used to bond concrete with CFRP sheet. It is consist of
two things, which are resin and hardener. The resin is a blue thick liquid and the hardener
is colorless light liquid. According to manufacturing requirements, the resin has to be
mixed with the hardener by 3:1 rate. In addition, curing time of the epoxy is 7 days to
reach the optimum strength.
Third, the CFRP sheets were cut to the size that required by the category. The
strength of CFRP sheet was attached on chapter 2. After 7 day of clued CFRP sheet, the
specimens are ready for testing.
3.2.2 Effective length of CFRP sheet
In brief, the authors create the affective length depend on, bond strength, the
thickness of epoxy, and compression strength of concrete.
Where:
Ep = Youngs modulus of bonded plate.
tp = Thickness of bonded plate.
/c= Concrete cylinder compressive strength;
Depend on the equation; the effective length is 87 mm. on another hand, the are three
(1)
31


types of this category, which are Le, 1.25 Le, 1.5 Le, 87 mm, 114 mm, and 137 mm,
respectively. The section depends on (Chen, and Teng, 2001).
3.2.3 Experimental phases
To summarize, there are two main phases that the experimental program has been
followed. Frist is to find the failure point of each type. In this phase, the heat did not
applied to the concrete block and they applied to tension untie failure. The second phase
is to applied thermo-mechanical load to the concrete blocks. These two phases will be
explained more in the Instrumentation and testing procedure section.
3.2.4 Heat application
More than 144 concrete blocks was cured and prepared to expose to elevated
temperatures from 25C [77F] to 175C [347F], Elevated temperatures were exposed
to the concrete surface by heating pad (100 mm X 150 mm). To measure the applied
temperature, there is a thermo couple attached to the surface of concrete blocks. In
addition, concrete blocks' heating were monitored by IR camera to see the heat
propagation.
3.2.5 Instrumentation and testing procedure
All concrete specimens were tested by MTS 20 kips machine. The machine is
setup depend on which phase is. Before starting any test, machine was preheated. It takes
one to two minutes to be ready for Appling the tension force. For safety, before switching
the machine on, all tools and all cables have to be connected to the controlling station.
While running any test, MTS recording the force, time, and displacement. In addition,
32


there are two phase of testing concrete blocks. The first phase is pullout tension. In this
phase, MTS machine applied gradually tension force unit the failure happened. There is
one failure mode happened to concrete blocks, which is epoxy and CFRP remove from
the concrete. That means CFRP and epoxy were separated as a one part from the surface
of concrete blocks. More than 18 concrete blocks were done to find the failure point for
each type of concrete specimen. Finding the failure point is very important to the second
phase. The second point is to find the temperature relaxation mode. In this phase, we
applied 30 % of the failure load and applied elevated temperatures from 25C [77F] to
175C [347F], Each category needs at least 63 concrete blocks. Machine is setup to do
two commands. First command start from zero unit the tension force reach the goal,
which is 30% of failure point. Second command is to hold this force until 20 minutes. For
these 20 minutes, the heat bed and thermo cable are attached to the concrete specimen.
On the other hand, IR camera was taking thermal images while concrete block is
tensioned and exposed to elevated temperature. The main advantage of using IR camera
is to see the thermal propagation Figure 3.2 b.
3.3 Test results
3.3.1 Failure point
MTS 20kips machine has applied tension force to 18 concrete specimens. The
load was applied gradually by load rate 16.67 N/sec Figure 3.3 a Concrete blocks were
tightened by steel frame. Steel frame was connected to MTS from down and the upper
part of MTS tensioned the CFRP sheet. For the first category, the average failure points
were 3.9 kN, 5.9 kN, 7.5 kN, 0.25B, 0.5B, 0.75B, respectively. Also, 0.198, 0.300, 0.179,
are the COY of 0.25B, 0.5B, 0.75B, respectively. On the second category, Le, 1.25 Le,
33


and 1.5 Le, there are not huge failure points between them. The average failure points
were 5.7 kN, 5.9 kN, 6 kN, Le, 1.25 Le, and 1.5 Le, respectively. Failure mode for all
concrete blocks was the epoxy removes totally from the surface of concrete. The main
purpose for testing the concrete until failure is to load 30% of these failure points to
concrete blocks while testing the thermomechanic test.
3.3.2 Thermomechanical load
Thermomechanical test takes 20 minutes for each specimen. Frist, MTS 20 kips is
setup for two commands, which are tensioned concrete blocks until it reach 30% of
ultimate load then hold that load for 20 minutes while applying elevated temperatures by
heating pad. Thermocouple is recording the equal applied temperature. Also, IR camera
is capturing the heat propagation. More than 122 concrete blocks were examined and
investigated while they are loaded by thermomechanical load. Three concrete blocks is
enough to find the behavior and performance of the relaxation behavior that happened
because of thermomechanical load at each specific temperature.
For first category shows similar performance at specific temperature. Frist, 0.25 B
type shows consist performance for elevated temperatures. Temperatures less than Tg
show similar behavior such as 25 C and 50 C by COV 0.079 and 0.111, respectively.
Also, the loss loads of temperatures less than Tg were very slight. For example, the
average of three concrete blocks were applied to 50 C shows a 15.38 % loss from
sustained load which is 1.17 kN. Nevertheless, the share stress of these specimens shows
very small relaxation such as 25 C and 50 C, shear stress loss 15 and 27 %, respectively.
In addition, the temperatures near Tg, which are 75 C, 100 C, 125 C show very
stabilized performance. 75 C specimen shows an average loss by 0.74 kN from 1.18 kN
34


at 1200 sec. comparing with the other concrete blocks, the standers deviation is 0.034
with COV 0.045 shown at At 100 C the performance of the three specimen is very
similar with coefficient of variatio 0.058 and standers deviation 0.033. 75 C, 100 C, 125
C shows losses 0.298, 0.233, and 0.213 by MPa, respectively. Shear stress for 75 C,
100 C, 125 C 34%, 48%, and 53%, respectively. In addition, the temperatures so far
from Tg, which are 150 C, 175 C show an enormous loss. 175 C specimen shows an
average loss by 0.253 kN from 1.18 kN at 1200 sec with standers deviation 0.065.
Because of high temperature, the percentage of loss gets almost 78 %. This will reflect
negatively to the capacity of the structure. Shear stress for high temperature reach 78%
loss by 0.097 MPa. From comparing with the control temperature, the decreasing load
ratio (AP/At) started from 0.8 to 0.25 at 175 C. This decreasing load ratio seems to be
liner figure 3.3.1 (a) to (n).
Secondly type 0.5B indicated consistent performance for elevated temperatures.
Temperatures lower than Tg had similar behavior, 25 C by COV 0.043 and 50 C by
COV 0.081. Loss shear stress for temperatures less than Tg were slight. For example,
three concrete blocks at 50 C indicated a 12% loss from a sustained load f 1.77 kN.
Shear stress of the specimens small relaxation, 25 C had 12% shear loss while 50 C, had
22 %,. Higher temperatures had stabilized performance. At 75 C the specimen had an
average loss of 1.16 kN from 1.77 kN at 1200 seconds standard deviation was 0.175 with
COV 0.151. At 100 C the specimens behave similarly with a co efficient of variation of
0.162. And standard deviation is 0.152. Temperatures beyond Tg had enormous losses of
almost 66%. Comparing with the control temperature the load ratio was decreasing. All
details are shown in figure 3.3.2 (a) to (n).
35


Third, 0.75 B type shows consist performance for elevated temperatures.
Temperatures less than Tg show similar behavior such as 25 C and 50 C by COV 0.070
and 0.056, respectively. Also, the loss loads of temperatures less than Tg were very slight.
For example, the average of three concrete blocks were applied to 50 C shows a 13 %
loss from sustained load which is 2.25 kN. Nevertheless, the share stress of these
specimens shows very small relaxation such as 25 C and 50 C, shear stress loss 7.1 %
and 13 %, respectively. In addition, the temperatures near Tg, which are 75 C, 100 C,
125 C show very stabilized performance. 75 C specimen shows an average loss by
1.648 kN from 2.25 kN at 1200 sec. comparing with the other concrete blocks, the
standers deviation is 0.039 with COV 0.024. At 100 C the performance of the three
specimen is very similar with coefficient of variatio 0.065 and standers deviation 0.097.
75 C, 100 C, 125 C shows losses 0.207, 0.194, 0.191 by MPa, respectively. Shear
stress for 75 C, 100 C, 125 C, 28.8 %, 33 %, and 34.5 %, respectively. In addition, the
temperatures so high from Tg, which are 150 C, 175 C show an enormous loss. 175 C
specimen shows an average loss by 1.093 kN from 2.25 kN at 1200 sec with standers
deviation 0.065. Because of high temperature, the percentage of loss gets almost 53 %.
This will reflect negatively to the capacity of the structure. Shear stress for high
temperature reach 53 % loss by 0.136 MPa. From comparing with the control
temperature, the decreasing load ratio (AP/At) started from 1.8 to 0.85 at 175 C figure
3.3.3 (a) to (n).
Second category also indicted the same performance. Type LE indicated
consistent performance for elevated temperatures. Temperatures lower than Tg had
similar behaviour, 25 C by COVoO.054 and 50 C by COV 0.026. At 50 C the loss was
36


12.22 % from sustained load of 1.71 kN. 25 C had shear stress of 3.5% while and 50 C
had 12.8 %. At high temperatures the percentage loss is high with shear stress of almost
75% that has a negative impact on the capacity of the structure. Figure 3.3.4 (a) to (n)
illustrate all details for each specific temperature.
Second, 1.25 Le type shows consist performance for elevated temperatures.
Temperatures less than Tg show similar behavior such as 25 C and 50 C by COV 0.055
and 0.093, respectively. Also, the loss loads of temperatures less than Tg were very slight.
For example, the average of three concrete blocks were applied to 50 C shows a 15.1 %
loss from sustained load which is 1.770 kN. Nevertheless, the share stress of these
specimens shows very small relaxation such as 25 C and 50 C, shear stress loss 3.7 and
15.1 %, respectively. In addition, the temperatures near Tg, which are 75 C, 100 C, 125
C show very stabilized performance. The 75 C specimen shows an average loss by
1.28 kN from 1.77 kN at 1200 sec. Comparing with the other concrete blocks, the
standers deviation is 0.068 with COV 0.052. At 100 C the performance of the three
specimen is very similar with coefficient of variatio 0.113 and standers deviation 0.138.
75 C, 100 C, 125 C shows losses 0.262, 0.236, 0.223 by MPa, respectively. Shear
stress for 75 C, 100 C, 125 C 23 %, 30 %, and 34 %, respectively. In addition, the
temperatures so far from Tg, which are 150 C, 175 C show an enormous loss. 175 C
specimen shows an average loss by 0.45 kN from 1.770 kN at 1200 sec with standers
deviation 0.120. Because of high temperature, the percentage of loss gets almost 75 %.
This will reflect negatively to the capacity of the structure. Shear stress for high
temperature reach 74 % loss by 0.087 MPa. From comparing with the control
37


temperature, the decreasing load ratio (AP/At) started from 1.45 to 0.45 at 175 C. This
decreasing load ratio seems to be liner figure 3.3.5 (a) to (n).
Type 1.5 Le indicated similar performance for elevated temperatures. At 25 C
and 50 C by COV 0.075 and 0.023, respectively with slight loss loads. Shear stress for
the specimen had small relaxation, 25 C had 4%shear stress while 50 C had 19%.
Temperature close to Tg (75, 100, 125 C) showed stabilized performance. Shear stress
was 75 C (22%), 100 0 C g(27%) and 125 C (38%). Temperatures far beyond Tg had
enormous loss. Due to the high temperatures the percentage loss was 65%.losses of shear
stress are shown in figure 3.3.6 (a) to (n).
For the two main categories, the performance of each specimen shows consistent
behavior. First, with different CFRP sheet width, 0.75B has showed very efficient
performance comparing with the anther two types. The total loss of each specific
temperature at 0.75B was the lowest loss of each individual temperature. However, the
behavior of 0.25 B is not efficient, because the maximum loss reach 75 % of the 30% of
ultimate load shown figure 3.3.7 (a) to (c) and 3.3.8 (a) to (c) With increasing the width
of CFRP sheet, the total shear stress loss decreased significantly from 78 % to 55%,
0.25B to 0.75B respectively. This decreasing ratio seems to be liner. However, the second
category (different L of CFRP sheet) shows disparate performance unlike first category.
The total shear stress loss generally is decreasing slightly with increasing in the length of
CFRP sheet. Fro example, 1.25Le show the maximum percentage loss by 75 %. 1.5 Le
shows the lowest loss percentage by 65 % at 175 C.
38


3.4 Thermal propagation at mid-span of the concrete block
All concrete specimens were exposed to elevated temperatures. The surface of
concrete blocks was heated by the heating bed and recorded by thermocouple. We can
control the applied heat from heating bed and the thermocouple attached to the surface of
concrete blocks. However, it is imposable to see the thermal propagation inside
individual concrete specimen. Therefore, FLIR E8, Infrared Camera (IR camera) with
MSX has been used for all elevated temperatures. IR camera has been used to capturing
the thermal propagation inside concrete blocks. This will reflect to our tests to see the
relationship between the specific temperature and the thermal propagation inside concrete
blocks. Each specific temperature was pictured for 1200 sec for two times, one while
loading and without. IR camera take shoot each 120 sec. At middle of span, there are four
points are pointed to read the temperature inside the block. They named by 1 to 4, where
point 1 is the nearest point from heating bed by 18.75 mm. Also, the distance between
each point is 18.75 mm.
For 50 C, there are two specimens were used to picture the thermal propagation.
Temperatures less than Tg show very less thermal propagation at mid-span. At 600 sec,
the temperature at mid-span was 23.4 C. After 1200 sec, the temperature reached 29 C
figure 3.4.1. Also, temperatures near Tg such as 75 C show similar thermal propagation
than temperatures lower than Tg. At 1200 sec, 75 C had a temperature at mid-span 32 C
figure 3.4.2. On the other hand, the temperatures higher than the Tg such as 100 C, 125
C, 150 C, show high thermal propagation than the temperatures less than Tg figure 3.4.3
to figure 3.4.5. On other words, with increasing applied temperature, the thermal
propagation increases significantly. For instance, while applying 175 C to concrete
39


blocks, at 120 sec the inducted temperature is equal to applying 75 C for 1200 sec, by 32
C. Comparing 175 C to loss strength, concrete specimen loss than 75 % of the applied
load figure 3.4.7 (a) to (g). Also All contour lines and summary were shown in figure
3.4.8 to 3.4.12.
3.5 Temperature dependent Model
There are two different models, which are Thermal relaxation Model, and Time
logarithm model. First, Thermal relaxation model depend on the performance of the
behavior of concrete specimens. There are three phases happened while applying
thermomechanical test. The first phase is to applying gradually tension force until a 30%
of ultimate load. The second phase is to determine the relaxation happened to concrete
specimens. The third phase is to find the final shear stress.
3.5.1 Thermal relaxation Model to 0.25 B type
f r f \ ^max ( f. ) for 0 < t < tmax
Lmax
T= i ,. ~ \r t~tmax \ a mu ax v Mu ax v Jl t ) Lf Lmax for tmax < t < tf (2)
[ Tf for tf < t
Where:
tf = 835.34e'0003T a = 0.3612e 0002T, tmax = -0.0002T + 70.737
x f = 0.4964e' 007T, x max = -2E-05T + 0.4634, T = temperature by C
tf is the time that finial shear stress (x f) start. tmax is the time that shear stress
reaches maximum shear stress (x max). a is an empirical coefficient. This model will be
repeated with all different types to illustrate a global model for each category (see figure
3.5.1).
40


3.5.2 Thermal relaxation Model to 0.5 B type
r t x ^max ( t ) for 0 < t < tmax
Lmax
W -(Tmax 'T/)(^7^) Lf Lmax for tmax < t tf
T/ for tf < t
Where:
tf = 897.65e'0003T, a = 0.5094e02T, tmax = -5E-05T + 106.56
x f= 0.3708e"06T, x max = 2E-05x + 0.3381, T = temperature by C
these specific values were molded from experimental data. Also, the date was feed to the
second equation to find the a (empirical coefficient). The regression trend line of each
parameter is shown in figure 3.5.2.
3.5.3 Thermal relaxation Model to 0.75 B type
t- f \ ^max ( t ) for 0 < t < tmax
Lmax
Tmax -(W Tf )( ) Lf Lmax for tmax ^ t tf (4)
T/ for tf < t
Where:
tf = 853.9e'0002T, a = 0.505e'04T, tmax = -0.0005T + 135.17
x f = 0.2987e'0 004T , x max = 2E-06T + 0.2926, T = temperature by C
The third type is 0.75 B, which is 200mm X 150 mm. all regression chart and
comparing chart with experimental specimens are show in 3.5.3.
41


3.5.4 Thermal relaxation Model to First category (Global model)
r t x ^max ( t ) for 0 < t < tmax
Lmax
Tmax -(Tmax 'T/)(^7^) Lf Lmax for tmax < t < tf (5)
T/ for tf < t
Where:
tf= = 865.27e , a = 0.453e , tmax = 110
x f= 1.0474e'0005T, x max = 1, T = temperature by C
Figure 3.5.4 compares between the model and the experimental work. Normalizing shear
stress for each type that exposed to the same temperature is used to illustrate the global
model. The limits of this model is from 1 to 3 width with 4 length.
3.5.5 Thermal relaxation Model to Le
f t x ^max ( t ) for 0 < t < tmax
Lmax
Tmax -(W Tf )( Lf Lmax for ^772(2^ f- (6)
Tf for tf < t
Where:
tf= 856.66e 0003T, a = 0.4618e04T, tmax =-0.0045T + 100.51
t f = = 0.4874e'0 008T, t max = 2E-05T + 0.3668, T = temperature by C
For second category, the same processes were repeated to illustrate the Global model.
Figures 3.5.5 show the regression line and compering results for elevated
temperatures.
42


3.5.6 Thermal relaxation Model to 1.25 Le
f r t ^ ^max ( t ) Lmax for 0 < t < tmax
T = i Enax "(^max _ r t tmax \ a Tf K v-w for tmax < t <
l T/ for tf < t
Where:
tf= 1003.6e'05T, a = 0.491e'0004T, tmax =-0.0014T + 108.93
x f = = 0.4027e'aoo8T, x max = 2E-06T + 0.3025 T = temperature by C
1.25 Le shows small different results between relaxation results from modeling and
experimental results. The comparing results and regression equations were shown in
Figure 3.5.6.
3.5.7 Thermal relaxation Model to 1.5 Le
f t x ^max ( t ) for 0 < t < tmax
Lmax
Tmax -(Tmax )( ) Lf Lmax for t-max f-
Tf for tf < t
Where:
tf = 942.14e 0005T, a = 0.4349e'0004T, tmax = -0.0012T + 108.58
x f = 0.2857e"0005T, x max = 1E-05T + 0.2558, T = temperature by C
For last type, comparing results shows similar results of experimental average shear
stress. Figure 3.5.7 illustrates the regression equations and comparing results
between experimental and modeling.
43


3.5.8 Thermal relaxation Global Model With different length
T= i
(7M
Lmax
"(^max ~^f )(
t-t-n
tf tf]
Lf
for 0 < t < tmax
) for tmax < t < tf
for tf < t
(9)
Where:
tf = 934.1e'0004T, a = 0.4202e'
xf = 1.2019e'0007T, max 1 5
0004T, W = 5E-16x+ 106.67
T = temperature by C
For different length, this global model illustrates the performance of each average
shear stress exposed to elevated temperatures. The limits of this model is from 3.6 to
5.4 length, with width 2. Figure 3.5.8 shows the comparing between experimental
and modeling.
3.5.9 Time logarithm model
3.5.10 Time logarithm model 0.25B
Y= a-b log (T) (10)
Where:
a= 0.465 MPa, b= 0.0601 e0 0087T, T= temperature by C
Another way to model the performance of average shear stress is to logarithm time. This
will make the experimental results straight lines. This model is repeated for each type to
illustrate the global model for each category. Comparing result is shown in figure 3.6.1.
3.5.11 Time logarithm model 0.5B
Y= a-b log (T) (11)
Where:
a= 0.351 MPa, b= 0.0403 e0 011 T, T= temperature by C
. Comparing result is shown in figure 3.6.2.
44


3.5.12 Time logarithm model 0.75B
Y= a-b log (T)
Where:
a= 0.291 MPa, b= 0.0321 e0 0105 T, T= temperature by C
. Comparing result is shown in figure 3.6.3.
3.5.13 Time logarithm Global model with different CFRP Width
Y= a-b log (T)
Where:
a= 1 MPa , b= 0.0457 e0 0097T5 T= temperature by C
. Comparing result is shown in figure 3.6.4.
3.5.14 Time logarithm model Le
Y= a-b log (T)
Where:
a= 0.372 MPa, b= 0.023 e00142T, T= temperature by C
. Comparing result is shown in figure 3.6.5.
3.5.15 Time logarithm model 1.25 Le
Y= a-b log (T)
Where:
a= 0.320 MPa, b= 0.0247 e0 0135 T, T= temperature by C
. Comparing result is shown in figure 3.6.6.
(12)
(13)
(14)
(15)
45


3.5.16 Time logarithm model 1.5 Le
Y= a-b log (T)
(16)
Where:
A= 0.256 MPa, b= 0.0351 e'
0.0107 T
T= temperature by C
. Comparing result is shown in figure 3.6.7.
3.5.17 Time logarithm Global model with different CFRP length
Y= a-b log (T)
(17)
Where:
a= 1 MPa,
b= 0.0295 e'
0.0123 T
T= temperature by C
Comparing result is shown in figure 3.6.8.
3.6 Summary and Conclusion
More than 144 concrete blocks were investigated in this chapter. All blocks has been
exposed to elevated temperatures 25 C to 175 C. there are two main categories were
illustrated in this chapter, which are different CFRP sheet width and Different length.
Also, IR camera has been used to capture the heat propagation inside strengthen
concrete blocks. Also, the correlation between all parameters is shown in table 3.6.
There are some conclusions are illustrated in this section.
Applying higher temperatures than Tg reflects to the performance of the
strengthen system negatively. In some cases the total loss reaches 75 %.
This enormous loss percentage happened because the epoxy was changed
from solid condition to rubber condition.
46


Increasing bonding area reflects to performance of system positively. For
example, 0.25B shows the highest loss for elevated temperatures.
However 0.75B shows the lowest loss for the same exposed temperatures.
IR camera shows the gradually propagation for each 2 min. with
increasing temperature the propagation increases.
In this chapter, average shear stress was modeled depend on the
experimental work. There are two temperature dependent models, which
are logarithm time and divided the performance of relaxation to three steps.
47


Table 3.1. Concrete mix design
w/c 68%
3 Cement (kg/m ) 279
Water (kg/m') 190
3 Aggregate (kg/m ) 1116
Sand (kg/m') 805
Table 3.1 a CFRP sheets sizes all unit by (in)
Width CFRP- bonded length CFRP- unbounded length
0.25 B 1 4 4
0.5 B 2 4 4
0.75 B 3 4 4
L 2 3.6 4
1.25 L 2 4.5 4
1.5 L 2 5.4 4
Table 3.2. Compressive strength of concrete cylinders 28 days
Specimen Compressive Stress (MPa)
Ml 17.22
M2 21.25
M3 19.66
Average 19.37
48


Table 3.6 : Correlation between all parameters
Variable width Variable Length Temperature Tf
Variable width 1 1 0 -0.244
Variable Length 1 1 0 -0.351
Temperature 0 0 1 -0.902
Tf -0.244 -0.351 -0.902 1
Figure 3.2 a : specimens ready for test
Figure 3.2 b : Applied thermomechanic load
49


Load (J Time (sec) Time (sec)
(a)
(b)
Time (sec)
Time (sec)
(c)
(d)
(e)
(f)
50


Time (sec) Time (sec)
(g)
(h)
Time (sec)
Time (sec)
(i)
(i)
(k)
(1)
51


Time (sec) Time (sec)
(m)
(n)
Figure 3.3.1 result of three specimens of 0.25 B, (a) and (b) 25 C, (c) and (d) 50 C, (e)
and (f) 75 C, (g) and (h) 100 C, (i) and (j) 125 C, (k) and (1) 150 C, (m) and (n)
175 C.
52


Time (sec)
Time (sec)
(a)
(b)
Time (sec)
Time (sec)
(c)
(d)
Time (sec) Time (sec)
(e)
(f)
53


Time (sec)
Time (sec)
(g)
(h)
Time (sec)
Time (sec)
(i)
(i)
(k)
(1)
54


Time (sec) Time (sec)
(m)
(n)
Figure 3.3.2 result of three specimens of 0.5 B, (a) and (b) 25 C, (c) and (d) 50 C, (e)
and (f) 75 C, (g) and (h) 100 C, (i) and (j) 125 C, (k) and (1) 150 C, (m) and (n)
175 C.
55


Time (sec) Time (sec)
(a)
(b)
Time (sec)
Time (sec)
(c)
(d)
Time (sec)
0 200 400 600 800 1000 1200 1400 1600
Time (sec)
(e)
(f)
56


Load (kN)
Time (sec) Time (sec)
(g)
(h)
Time (sec)
Time (sec)
(i)
(i)
(k) (1)
57


Time (sec) Time (sec)
(m)
(n)
Figure 3.3.3 result of three specimens of 0.75 B, (a) and (b) 25 C, (c) and (d) 50 C, (e)
and (f) 75 C, (g) and (h) 100 C, (i) and (j) 125 C, (k) and (1) 150 C, (m) and (n)
175 C.
58


Time (sec) Time (sec)
(a)
(b)
Time (sec)
Time (sec)
(c)
(d)
Time (sec) Time (sec)
(e)
(f)
59


Time (sec)
Time (sec)
(g)
(h)
Time (sec)
(i) (i)
(k) (1)
60


175 C (Average)
Time (sec) Time (sec)
(m) (n)
Figure 3.3.4 result of three specimens of Le, (a) and (b) 25 C, (c) and (d) 50 C, (e) and
(f) 75 C, (g) and (h) 100 C, (i) and (j) 125 C, (k) and (1) 150 C, (m) and (n) 175 C.
61


Time (sec)
Time (sec)
(a)
(b)
Time (sec)
Time (sec)
(c) (d)
Time (sec)
Time (sec)
(e)
(f)
62


Time (sec)
Time (sec)
(g)
(h)
Time (sec)
Time (sec)
(i)
(i)
(k)
(1)
63


175 C (average)
Time (sec) Time (sec)
(m) (n)
Figure 3.3.5 result of three specimens of 1.25 Le, (a) and (b) 25 C, (c) and (d) 50 C, (e)
and (f) 75 C, (g) and (h) 100 C, (i) and (j) 125 C, (k) and (1) 150 C, (m) and (n)
175 C.
64


Time (sec)
Time (sec)
(a)
(b)
Time (sec)
Time (sec)
(c)
(d)
Time (sec)
Time (sec)
(e)
(f)
65


Time (sec)
Time (sec)
(g)
(h)
Time (sec)
(i)
G)
(k) (1)
66


175 C (average)
Figure 3.3.6 result of three specimens of 1.5 Le, (a) and (b) 25 C, (c) and (d) 50 C, (e)
and (f) 75 C, (g) and (h) 100 C, (i) and (j) 125 C, (k) and (1) 150 C, (m) and (n)
175 C.
67


%ofloss Rate 2
-----0.25B
2.5
....0.25 B
0.5 B
-----0.75 B
(a)
0 I i-------------1------------1------------
0 50 100 150 200
Temperature CC)
(b)
(c)
(d)
Figure 3.3.7 (a): the different loss ratio by (kN/sec), (b) the total loss by kN, (c): the total
loss by percentage, (d) the total shear stress loss by MPa for 0.25B, 0.5B, and 0.75B.
68


(a) (b)
(c)
(d)
Figure 3.3.7 (a): the different loss ratio by (kN/sec), (b) the total loss by kN, (c): the total
loss by percentage, (d) the total shear stress loss by MPa for Le, 1.25 Le, and 1.5 Le.
69


(i) (k)
Figure 3.4.1: thermal propagation for block heated to 50C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.
70


(d)
(e)
(f)
(i) (k)
Figure 3.4.2: thermal propagation for block heated to 75 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.
71


(g)
(h)
(i)
mum
CFLIR 23.6
(j) (k)
Figure 3.4.3: thermal propagation for block heated to 100 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.
72


(g)
(h)
(i)
(j) (k)
Figure 3.4.4: thermal propagation for block heated to 125 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.
73


(d)
(e)
(f)
45.8 c
130


EL
Oflir
26.0
(i) (k)
Figure 3.4.5: thermal propagation for block heated to 150 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.
74


(g)
(h)
(i)
(j) (k)
Figure 3.4.6: thermal propagation for block heated to 175 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.
75


(i)
Figure 3.4.7: thermal propagation for block heated to 75 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 20 minutes.
76
*SS g g 8 6 IS SC SS 8
CM *


(i)
Figure 3.4.8: thermal propagation for block heated to 100 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 20 minutes.
77


29.5
(i)
Figure 3.4.9: thermal propagation for block heated to 125 C at: (a) 0; (b) 2; (c) 4; (d) 6;
(e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 20 minutes.
78


29
(a) (b) (c)
(j)
Figure 3.4.10: thermal propagation for block heated to 150 C at: (a) 0; (b) 2; (c) 4; (d)
79
88$ 8


28
27.5
27
429 430
428
430 434 ^
29
_J~44 ^
t33 t42 42 48
43 L^: J
(3)
Figure 3.4.11: thermal propagation for block heated to 175 C at: (a) 0; (b) 2; (c) 4; (d)
6; (e) 8; (f) 10; (g) 12; (h) 14; (i) 16; (j) 20 minutes.
80
£ ft K


(c) (d)
(e)
Figure 3.4.12: thermal propagation for blocks: (a) 75 C (b) 100 C (c) 125 C (d)
150 C (e) 175 C, for 20 minutes
81


0 200 400 600 800 1000120014001600
Time (sec)
(a)
(b)
(c)
(d)
0 200 400 600 800 1000120014001600
Time (sec)
(e)
(f)
(g)
82


0 50 100 150 200
Temperature {C)
(h)
(i)
06
055
0.5
045
0.4
0 35
03
* t max
50 100 150 200
Temperature (l,C)
02 y = 0.3612e 0002x
0.15 R* = 0.60487
o.i
0.05 '
0 \----------1---------1---------1----------1
0 50 100 150 200
Temperature (C)
(i)
(k)
Figure 3.5.1: compares between model and experimental for 0.25B: (a) 25 C, (b) 50 C,
(c) 75 C, (d) 100 C, (e) 125 C, (f) 150 C, (g) 175 C, (h) finial shear stress (t f), (i)
time of maximum shear stress tmax, (j) maximum shear stress (t max). (k) a is an empirical
coefficient.
83


(C) (d)
(e)
(f)
(g)
84


Full Text

PAGE 1

THERMOMECHANICAL RESPONSES OF CONCRETE MEMBERS STRENGTHENED WITH CFRP SHEETS By ABDULAZIZ ALQURASHI B.S., Umm Al Qura University 20 10 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillm ent of the requirements for the degree of Master of Science Civil Engineering 201 5

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ii 201 5 ABDULAZIZ ALQURASHI ALL RIGHTS RESERVED

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iii This thesis for the Master of Science degree by Abdulaziz Alqurashi has been approved for the Civil Engineering Program By Yail Jimmy Kim, Chair Cheng Yu Li Nien Yin Chang

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iv November 20 2015 Abdulaziz Alqurashi (M.S. Civil Engineering) Thermomechanical responses of concrete members strengthened with CFRP sheets. Thesis directed by Assoc iate Professor, Yail Jimmy Kim A BSTRACT Strengthening structural members means to be able to carry additional loads Since, 1990s, a lot of materials and techniques have been established to not only increasing the capacity of member but also facing deter ioration Deterioration has become one of the worst highly maintenance cost. According to The ASCE, 27.1% of all bridges in the United States are not effectual This is because the high traffic reflects negatively to structural members and cause deteriorat ion of these members. This problem has been cost a lot of money. In addition, FRP has approved that it can increase the capacity of member and overcome some disadvantages such as deterioration. Therefore, CFRP sheet has become widely used. However, high te mperatures affect the performance of externally bonded CFRP sheet negatively. Investigation should be carried out on relaxation and flexural performance of members under different temperatures Therefore, this thesis focus on a nalyzing and investigating th e per formance of strengthened members exposed to elevated temperatures (25 to 175 0 C) The experimental program was divided to two main parts. First, 144 strengthen concrete blocks 100mm X 150mm X 75 mm has been exposed to elevated temperatures. These block s have two main categories, which are different CFRP sheet width, and different CFRP sheet length. Different CFRP width has three types, which are type 0.25B (25mm x 100mm), type 0.5B (50mm x 100mm) and

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v type 0.75B (75mm x 100mm). Also, Different CFRP lengt h has three types, which are type L e (bonded area of 50 mm by 90mm ), 1.25 L e (area of 50mm by 125mm ) and type 1.5L e (50mm by 137 mm). Second, studying the performance of RC beams exp osed to elevated temperatures. The form and content of this abstract are approved. I recommend its publication. Approved: Jimmy Kim

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vi ACKNOWLEDGEMENTS Since I got B.S. at 2010, I have been excited to study more about civil engineering. In spring 2014, a ssociate Professor Yail Jimmy Kim the ideal gave me an e normous opportunity to be one of his amazing research team. Without his advice and inspiration I could not do this entire thesis. I appreciate him for all work that he has done for me or to the research students. He is my thesis adviser and he supports m e and encourages me to do the best. Every Friday meeting, I have learned new things not only for me work but also to develop me ski lls. Also, I appreciate all civil engineering members, who are department chair, committee chair and committee members I wo uld like to also thank the Faculty of Engineering Department, who help me and support me to reach me goal. Also I would like to thank the lab staff members, Tom, Jack, and Eric. I would like to thank research mate student for their assistance and enco uragement Ibrahim bumadia n, Abdullah Alajmi, ihama lkubaisy, Ahmed Mutalib, Thushera, and Yongcheng Thank you all friend You help me and support me. Thanking to Saudi Arabian Cultural Mission (SACM ) and Islamic university for help me and be sponsor of me master studying. They were with me since I came Colorado. Thank you so much. I would take this opportunity and thank Dr. Mohammad Farouq Addas, who always encourage me to do the best. Finally, My parent thank you so much for all helping and support ing. You were the fuel that makes me work. I always feel you around my all time. I would like to thank

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vii you for all work that you did for me I would take this opportunity to thank my wife and son for making my life happy.

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viii TABLE OF CONTENTS Chapter 1. I ntroduction.. .. ... ..1 1.1 General ... ..1 1.2 Research significance and objectives ... 3 1.3 Thesis o rganization. .. ............5 2. Literature r eview ..7 2.1 Str engthening systems for concrete structures ... ...7 2.2 FRP... .8 2.2.1 FRP applications ... 10 2.2.2FRP techniques .. .. 11 2.2.3 NSM FRP s trengthening system ..14 2.3 Externally bonded sheet strengthening system .. ..16 2.3.1 Externally bonded sheet techniques .. ... 17 2.3.2Previous applications on externally bonded sheet ... 18 2.3. 3Previous research studies on externally bonded sheet FRP ... ... 19 2.4 Fire endurance of concrete Structures .19 2.4.1 Effect of elevated t emperatures on CFRP Materials .. . 20 2.4.2 Effect of elevated t emperatures on ep oxy and resin .. ... 21 2.4.3 E bonded sheet concrete structures exposed to fire .. ..23 2.5 The glass transition temperature for epoxy ... ... ... 24 2.6 Summary and Conclusions .. 25

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ix 3. Performa nce of e xte rnally bonded CFRP concrete Interface subjected to elevated t emperatures ... .28 3.1 General ... 28 3.2 Experimental program ... .. 3 0 3.2.1 specimen preparation... ... ............ .............. 31 3.2.2 Effective length of CFRP sheet ... 32 3.2.3 Experimental phases 33 3.2.4 Heat application 34 3.2.5 Instrumentation and testing proce dure .. 34 3.3 Test results .. .35 3.3.1 Failure point .. 35 3.3.2 Thermomechanical load ... ... 36 3.4 Thermal propagation at mid span of the concr ete block .. . 40 3.5 Temperature dependent Model s... ..... .. 41 3.5.1 Thermal relaxation Model to 0.25 B type ... .... ... ....... 41 3.5.2 Thermal relaxation Model to 0.5 B type ... ...... ... ... 42 3.5.3 Thermal relaxation Model to 0.75 B type.... ... ... .. .42 3.5.4 Thermal relaxation Global Model .. .. .... .................. .43 3.5.5 Thermal relaxation Model to Le ... .. .. .. .....4 3 3.5.6 Thermal relaxation Model to 1.25 Le .. ... ..... .................. ..44 3.5.7 Thermal relaxation Model to 1.5 Le .. .... .................. .............. .44 3.5.4 Thermal relaxation Global Model .... ... ................... ... .................. ........... .4 5 3.6 Time logarithm Model .. ... ............................... 45

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x 3.6.1 Time logarithm Model 0.25B ... ........................................................ ... .45 3.6.2 Time logarithm Model 0.5B .. .46 3.6.3 Time logarithm Model 0.75B ... 46 3.6.4 Time logarithm global Model with different CFRP Width ...... .. 46 3.6.5 Time logarithm Mod el Le ... .. 46 3.6.6 Time logarithm Model 1.25Le ... .. 47 3.6.7 Time logarithm Model 1.5Le ... 47 3.6.8 Time logarithm G lobal Model with different CFRP length ... .. 47 3.7 Summary and Conclusion ... .47 4. Performance of Externally bonded CFRP RC beam Subjected to Elevated Temperatures ... 107 4 .1 General ... 1 07 4 .2 Experimental program .. 109 4 .2.1 specimen preparation... ........ ........... .... ....110 4.2.2 Experimental category ... ...111 4.2.3 Heat application ... ... 111 4.2.4 Instrumentation and testing procedure ... .112 4 .3 Test results ..... ....113 4 .3.1 four points bending ... .. ... .. 113 4 .3.2 three points bending ... 114 4.3.3 Failure Mode... ... .116 4 .4 Thermal propagation at mid span of the RC beam .. 116 4.5 Summary and Conclusion .. .117

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xi 5.1. Summary and Conclusion ... .151 References ... 154 Appendix A ...157 B ...182

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xii LIST OF TABLES Table 2.1 FRP Tensile Strength and Young's Modulus ( ACI 440.2R 08) 27 3. 1. Concrete mix design .....49 3.1 a CFRP sheets sizes all unit by (in) ... 49 3.2. Compressive strength of concrete cylinders 28 days ........49 3.6 Correlation between all parameters 50 4.3.3 1 four point bending test ........122 4.3.3 3 th ree point bending test .. ... ........122

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xiii LIST OF FIGURES F IGURES 3.2 a : specimens ready for test ing .. ..50 3.2 b : Applied th ermomechanic load .. .. ...50 3.3.1 result of three s pecimens of 0.25 B, (a) 25 ¡C to (n) 1 75 ¡C ...53 3.3.2 result of three specimens of 0.5 B, (a) 25 ¡C to (n) 1 75 ¡C .. ...56 3.3.3 result of three specimens of 0.75 B, (a) 25 ¡C to (n) 1 75 ¡C .59 3.3.4 result of three specimens of Le, (a) 25 ¡C to (n) 1 75 ¡C ... ... 62 3.3.5 result of three s pecimens of 1.25 Le, (a) 25 ¡C to (n) 1 75 ¡C ..6 5 3.3.6 result of three s pecimens of 1.5 Le, (a) 25 ¡C to (n) 1 75 ¡ C ....68 3.3.7 (a) to (d) different ratio for 0.25B, 0.5B, and 0.75B 79 3.3.8 ( (a) to (d) different ratio for Le, 1.25 Le, and 1.5 Le ... 70 3.4.1: thermal propagation for block heated to 50¡C at: (a) to (k) .. .71 3.4.2 : thermal propagation for block heated to 75 ¡C at: (a) to (k) ..72 3.4.3: thermal propagation for block heated to 100 ¡C at: (a) to (k) ...73 3.4.4: thermal propagation for block heated to 125 ¡C at: (a) to (k) ...74 3.4.5: thermal propagation for block heated to 150 ¡C at: (a) to (k) .. ..75 3.4.6: thermal propagation for block heated to 175 ¡C at: (a) to (k) ... .. .. .....76 3.4.7 : thermal propagation for block heated to 50¡C at: (a) to (k) .. .77 3.4.8 : thermal pr opagation for block heated to 75 ¡C at: (a) to (k) ..78 3.4.9 : thermal propagation for block heated to 100 ¡C at: (a) to (k) ....79 3.4.10 : thermal propagation for block heated to 125 ¡C at: (a) to (k) ....80

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xiv 3.4.11 : thermal propagation for block heated to 150 ¡C at: (a) to (k) ....81 3.4.12 : thermal propagation for block heated to 175 ¡C at: (a) to (k) ... .... .....82 3.5.1: compares between model and experimental for 0.25B: (a) to (k) ... ...85 3.5.2: compares between m odel and experimental for 0.5B: (a ) to (k) ...87 3.5.3: compares between model and experimental for 0.75B: (a) to (k) ... ...89 3.5.4: gl obal model for different width: (a) to (k) ...90 3.5.4: compares between model and experi mental for Le: (a) to ( k) ... ...92 3.5.5: compares between model and experimental for 1.25Le: (a) to (k) ...94 3.5.6: compares between model and experimental for 1.5Le: (a) to (k) .. ...96 3.5.7: compares between model and experimen tal for 1.5Le: (a ) to (k) .. ...98 3.5.8: global mod el for different length: (a) to (k) ... ...100 3.6.1 temperature dependent For 0.25 B: (a) to (b) .. ...101 3.6.2 temperature dependent For 0. 5 B: (a) to (b) ..101 3.6.3 temperature dependent For 0.7 5 B: (a) to (b) .. 101 3.6.4: global model for different width: (a) to (j) .. ... 103 3.6.5 temp erature dependent For Le: (a) to (b) .104 3.6.6 temperat ure dependent For 1.25 Le: (a) to (b) .104 3.6.7 temperature dependent For 1.25 Le: (a) to (b) .104 3.6.8: global model for different length: (a ) to (j) ... .105 4.1a: Four points bending .. .. .119 4.1b: Three points bending ... .119 4.2: Beam section .119 4.2.1a: Test preparation .. ...120

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xv 4.2.1b: Test preparation 121 4.2.1c: Test prepa ration ... .. 122 4.3: MTS setup ...1 22 4.3.1 (I): response of unstrengthen beam: (a) to (e) ......1 23 4.3.1 (II): response of strengthen beam: (a) to (e) .........1 24 4.3.1 (III): res ponse of strengthen beam at 75 o C : (a) to (e) .........1 25 4.3.1 (IV): response of strengthen beam at 100 o C : (a) to (e) ...........1 26 4.3.1 (V): response of strengthen beam at 125 o C : (a) to (e) ........12 7 4.3.1 (VI): response of str engthen beam at 150 o C : (a) to (e) .......12 8 4.3.1 (VII) compares temperatures and strain.. .. 12 9 4.3.2 (I): response of strengthen beam at 75 o C : (a) to (e) ........130 4.3.2 (II): response of strengthen beam at 100 o C : (a) to (e) ............ 1 31 4.3.2 (III): response of strengthen beam at 125 o C : (a) to (e) .......1 32 4.3.2 (IV): response of strengthen beam at 150 o C : (a) to (e) .......1 33 4.3.2 (V): response of strengthen beam at 150 o C at 45 mins : (a) to (e) ......... .. 1 34 4.3.2 (VI): response of strengthen beam at 150 o C at 60 mins : (a) to (e) ........ .. 1 35 4.3.2 (VII): response of strengthen beam at 150 o C at 75 mins : (a) to (e) ........... 1 36 4.3.2 (VII) compares temperatures and Pu: (a) to (f) ... 13 7 4.4.1: thermal propagation for beam heated to 75 ¡C at: (a) to (k) ...13 8 4.4.2: thermal propagation for beam heated to 100 ¡C at: (a) to (k) .....1 41 4.4.3: thermal propagation for beam heated to 125 ¡C at: (a) to (k) .....1 43 4.4.4: thermal propagation for beam heated to 150 ¡C at: (a) to (k) .. .1 45

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xvi 4.4.5 : thermal propagation for beam heated to 7 5 ¡C at: (a) to (k) ...146 4.4.6 : thermal propagation for beam heated to 100 ¡C at: (a) to (k) ....1 47 4.4.7 : thermal propagation for beam heated to 125 ¡C at: (a) to (k) .....1 48 4.4.8 : thermal propagation for beam heated to 150 ¡C at: (a) to (k) .. .1 49

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1 1. Introduction 1.1 General Concrete is one of the most popular materials in c onstruction. Since it's composite of inexpensive materials such as cement, aggregate, and water, it becomes a wildly used material around the world. This composite material has advantages and disadvantages. Because it's very durable material, a lot of rese arches have been done to overcome the disadvantages. For example, concrete weak in tension and strong in compression. Therefore, Reinforcement concrete system has been created to overcome the weakness of concrete. With rapidly development in construction, the concrete technology has to walk parallel with this development. Therefore, the Prestressed concrete was created to overcome the limit of reinforcement concrete span. Like this technique many megastructures such as bridges, and garages can be built. Gir ders, beams, or slabs that were built by using prestressed technique can cover longer span than reinforcement concrete. These critical structures need very important maintenance, because there are many factors such as corrosion and weather conditions. Thes e factors cause one of the most danger problem which deterioration. Therefore, the maintenance of these important structures is very expensive. Because of these factors of deterioration, many researchers had tried to find new technology or new material can strengthen the structures without changing size of the structure member. According to Chen, Teng, 2003 in early 1990s, there are new material which can defend this problem which is Carbon fiber reinforced polymer (CFRP). This amazing material can incre ase the capacity of the member without changing the dimensions of the member. Briefly, Concrete technology has rapidly developed due to the complexity of new structures. There are a lot of papers have been

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2 published to cover these new techniques. In additi on, CFRP has approved that it is very light material that can overcome many rick factors. Fiber reinforced polymer (FRP) is a gorgeous material. It is consist of fiber and polymer. Because of its advantages, it has become a perfect alternative strengthen m aterial. FRP is being noticeable by engineers in the early of 1990 ( Chen and Teng, 2003). FRP has a lot of pros such as light, noncorrosive and high tensile material. Based these advantages, FRP approve that it is an efficient composite material. Accordin g to Lee, L. S., & Jain, R. 2009, to investigate if any composite material is a sustainable material, it has to follow these factors, which are less resource using environmental effect, human risks, performance. For all these factors, there are few materi als can satisfy these requirement. There are some challenges for FRP to be sustainable material, but depend on a lot of its advantages; FRP is an efficient composite material ( Lee, L. S., & Jain, R. 2009) Therefore, FRP has become the most popular stren gthen material in construction. There are different sizes and fibers in market. There are three popular fibers in construction, which are Carbon fiber reinforced polymer (CFRP), Aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFR P). The First type is CFRP. This kind is made from carbon fiber. From table 2.1, CFRP shows the highest tensile strength and Young's Modulus. In addition, CFRP is the highest stiffness, excellent fatigue, lower creep and relaxation ( Carolin, 2003). The sec ond common type is glass fiber reinforced polymer (GFRP). This kind is widely used because of its advantages such as, cheaper than CFRP, high resistant to chemicals. There are three common types of glass, which are E glass, C glass, and D glass ( Carolin, 2 003). The third type is Aramid fiber reinforced polymer (AFRP). Aromatic polyamide (Aramid) has different brands in market depend

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3 on the name of fiber such as, Kevlar¨, Twaron¨, and Technora¨. Furthermore, AFRP is lower cost than CFRP, and very light mater ial. However, it shows some issues with relaxation ( Carolin, 2003 ). FRP has a number of advantages. It has low weight compare with steel, concrete, or wood. Also it shows high tensile strength, high durability, and noncorrosive. Therefore, any strengthen structural by FRP would avoid a problem of deterioration ( Lee, L. S., & Jain, R. 2009). On the other hand, the normal structural member has shown a lot of the cons such corrosion, and deterioration. Therefore, a number of engineers and researchers have don e a lot of papers to study and investigate FRP as a structural element. For Example, Erki M. A., & Rizkalla, S. H. (1993) illustrated using CFRP instead of reinforcement steel. The authors concluded that it's difficult used CFRP as reinforcement because low failure strain and very high cost control the design. In addition, many researches have been published to investigate the performance of FRP as strengthen material. According to ACI, 440R, (2002) FRP can be used as maintenance and strengthening mater ial. In addition, there are two main FRP systems, which are NSM strengthening system, and Externally bonded strengthening system. The report illustrated the different types of strengthening such as flexural strengthening and shear strengthening ( ACI, 440R, 2002) 1.2 Research significance and objectives For last 20 years, the using of FRP as has been increased because of some factors such as corrosion and fire. Therefore, a number of papers have been published to start using FRP as construction or repair materi al. Also, a lot of engineers and scholars have been investigating and trying to find the efficient way to use FRP in structure filed. In addition,

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4 there are few published papers that study and investigate the behavior and performance of NSM CFRP exposed to elevated temperatures. For example, Siriwardanage has studied and investigated the performance of NSM CFRP exposed to elevated temperatures at 2014. He also, focused on the chemical of the epoxy that exposed to high temperatures. In addition, there are so me papers that investigate not only the failure of different kind of epoxy exposed to high temperatures but also, the different isolated system. However studying and investigating the b ond performance of an externally CFRP sheet strengthening system at el evated temperatures has not been well researched. Therefore, This thesis is focusing on the bond performance of CFRP exposed to elevated temperatures This experimental program has two main phases. The first phase is to study the perfo rmance of externally bonded CFRP concrete blocks interface subjected to elevated temperatures In this phase, more than 144 concrete blocks were exposed to elevated temperatures ranging fro m 25¡C (77¡F) to 175¡C (347¡F) The second phase is to investigate the performance of RC beam strengthen by CFRP sheet exposed to elevated temperatures ranging fro m 25¡C (77¡F) to 175¡C (347¡F) The objective of this thesis is illustrated below. Studying and investigating experimentally the behavior and performance of strengthen concrete s ystem. The performance of different CFRP sheet bonded area is investigating. More than 144 concrete specimens were exposed to elevated temperatures ranging fro m 25¡C (77¡F) to 175¡C (347¡F) 30% of ultimate load was applied to the concrete blocks. Focu sing on the temperatures higher than Tg is very important since epoxy is

PAGE 21

5 changed to r ubber condition because of high temperatures. Thermal propagation was captured be using IR camera. The aim of using IR camera is to investigate the relationship between t he specific temperature and specific points inside the tested block or beam High temperatures change epoxy state which will reflect to the performance of not only the bond strength, but also to the whole strengthen system negatively. Therefore, a numb er of beams were investigated experimentally to figure out the relationship between elevated temperatures and the performance of beams. 1.3 Thesis Organization Five chapters are in tis thesis Literature review of CFRP is illustrated in chapter two. Chap ter two demonstrate the strengthening systems for concrete structures, FRP applications and techniques, previous applications on externally bonded sheet, Effect of Elevated Temperatures on CFRP Materials and e glass transition temperature for epoxy. Ch apter three presents the experimental programs of strengthen concrete blocks exposed to elevated temperatures. Chapter three investigates the behavior and performance of concrete specimens. Also, thermal propagation is capture in chapter three. Modeling th e behavior of the specimens is taking a large area in the chapter. Reinforcement concrete beams strengthen by CFRP sheet is illustrated in Chapter four. All beams were exposed to elevated temperatures. The behavior of the beams is being focused on the chapter four.

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6 Chapter five presents summary and conclusion of entire thesis. Also, some recommendations based the experimental program is illustrated in chapter five. Appendix A presents all tables of results of concrete blocks and RC beam strengthen by CFRP Appendix B presents pictures of all process of experimental program and thermal propagation.

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7 2. Literature Review 2.1 Strengthening systems for concrete structures Civil engineering has faced a challenge of rehabilitation of deterio ration of infrastructures like the beams, girders, marine structure and even roads. These structures may be deteriorating because of different reasons. The reasons can be due to age, natural disasters such as earthquakes, poor maintenance, poor environment al conditions and even poor initial design. This has raised a need to upgrade the civil engineering structures. However, the upgrades come with demands that are increasing. An example is the increased traffic conditions that in some cases do not go togethe r with the initi al design (De Lorenzis, Nanni, & La Tegola, 2000). Due to the above issues, it is of great importance that the rehabilitation of the civil engineering structures should be addressed The traditional methods of reinforcing concrete structure s include, steel plate bonding and concrete column jacketing. When the steel plates are used in bonding, they are known to increase the flexural capacity of concrete members at the tension zones. Steel has been used for a long time to strengthen the struct ures especially concrete (Hollaway&Leeming, 1999). Despite steel increasing the flexural capacity of the structural members, it has faced many challenges that have rendered it not effective for use as a material for strengthening. First, the bond between steel and concrete deteriorates over time (Chen &Teng, 2001). There are also difficulties that have been experienced during the installation of steel such as the fact that heavy machines are needed in installing. As a result of these drawbacks, researchers have come up with FRP strengthening as a method of replacing steel that has been in existence for long (Chen &Teng, 2003).

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8 2.2 FRP FRP (Fiber Reinforced Polymer) is a polymer that has been reinforced using a fiber. The main aim of using the fiber is to ta ke part in carrying the strength and stiffness in one direction. The FRP are under the class of materials called the composite materials. The composite materials do not change their physical or chemical compositions in the combined state. FRP are very diff erent from the other construction materials like aluminum and steel. Steel and aluminum are isotropic while the FRP are anisotropic. The properties of FRP are directional. This means that the best mechanical properties of the FRP are in the direction in wh ich the fiber is placed (Kim, & Mai, 1998). The FRP have composite components. First are the fibers. The properties of the composites are mainly determined by the fibers. In civil engineering, there are three types of fibers, which are very dominant. The three fibers are aramid, glass and carbon (Lee & Jain, 2009). Their naming is always done by the fiber that has been used to reinforce. The different types have the fibers when compared to the ordinary steel. The main difference between the three types of fibers is the tensile strain and the stiffness. Another composite is the matrices. The main function of the matrices is to ensure that the forces are transferred along the fibers. The matrices also protect the fibers from the environment. Thermosets are e xclusively used in civil engineering. The two common matrices used are epoxy and vinyl ester. Epoxy is preferable but more costly to vinyl ester. There are different types of FRP. Those that are used in civil engineering are only three, which are glass fib er, aramid, and carbon fiber.

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9 The glass fibers are majorly made by mixing limestone, folic acid, silica sand and some other minor ingredients. During the making of these fibers, the mix is heated to a temperature of 1260 o C. T he glass that is in molten fo rm is allowed to flow through holes that are made on a platinum plate. The strands of the glass are left to cool, gathered and then wound. The fibers are drawn so that the directional strength is increased. The fibers are made in different shapes and forms so that they can be used in the composites. The glass produced fibers have a low susceptibility when exposed to moisture; they are good electrical insulators and have very high mechanical properties. Glass happens to be a good impact resistant. However, g lass weighs more when compared to carbom and aramid. The glass fibers have properties that are better that that of steel in some given forms. The second type of fiber polymer is the carbon fiber reinforced polymer. These types of polymer always have a high modulus of elasticity that ranges from 1 00 14 0 Gpa (Bakis, Ganjehlou, Kachlakev, Schupack, Balaguru, Gee & Harik, 2002). The carbon fiber is non reactive and does not absorb water. They are very excellent when it comes to withstanding fatigue. They do not show any signs of relaxing nor do they stress corrode. When in direct contact with steel, carbon fiber can give a galvanic corrosion. This is because the carbon fibers are electrically conductive. The third type of reinforced fiber is the aramid fiber rei nforced polymer. The word aramid is the shortened form of the word aromatic polyamide. Aramid is mainly used for helmets and the bullet proofs. This is because it has very high fracture energy. These types of fibers are not highly used in civil engineering This is because the aramids

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10 are sensitive to high temperatures, ultraviolet radiation as well as moisture. These types of fibers do not have any problem with stress corrosion and relaxation. There are different reasons why FRP have become very common esp ecially in civil engineering. Some of the reasons include the fact that they can absorb energies. The corrosion potential in the fibers is also reduced. The fasteners and the joints are simplified while using the fibers or even eliminated. The FRP can give stiffness to density ratio of between 4 to 5 times better than steel or aluminum. The materials also have a high fatigue endurance limits. These advantages contribute to the high usage of FRP in civil engineering structures (Chen, &Teng, 2003). 2.2.1 FRP applications The FRP are being used as an enhancement for the structural elements because of their recommended properties. The FRP are also being used as substitutes for the traditional engineering materials such as steel and aluminum (Bakis.,Ganjehlou, K achlakev, Schupack, Balaguru, Gee &Harik, I2002). The reason behind the use is, FRP do not corrode like steel, they have a specific stiffness, are lightweight and they show a high specific strength (Carolin, 2003). The composites can also be structured to fit the performance that is required (Lee, & Jain, 2009) Because of these characteristics FRP has been included in rehabilitation and construction of structures through its use in reinforcing concrete (Kim, & Mai, 1998). The carbon fiber reinforced po lymers are very strong and contain carbon fibers. The carbon fibers are classified based on the strength, modulus, and the final heat treatment.

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11 Based on the carbon fiber properties, t he carbon fibers can be put into five groups that include the SHT (Super high tensile type) this have a tensile strength greater than 4,5 Gpa (Benedikt, Goodall, & Society of Plastics Engineers 1998). The second one is the HT (high tensile and low modulus) type. The IM (intermediate modulus), the HM (High Modulus and lastly the ultra high modulus (UHM). Basing the classification on the precursor fiber material, there are six classes, and they include the pitch based, isotropic pitch based, rayon based, gas phase grown and the PAN base carbon fibers. Another classification is on the final heat treatment. Under this classification, there are only three types. The first one is the high heat treatment; type 2 is the intermediate heat treatment carbon, and the last type is the low heat treatment carbon (Erki, &Rizkalla, 1993). 2.2 .2FRP techniques The techniques used in strengthening are concerned with the application of FRP to an existing concrete substrate as a structural reinforcement. Taking into account all the requirements and the specifications, the technique can be applied under different conditions and at different places of the structural member The first technique is the basic technique. In this technique, wet lay up is applied manually. The main feature that distinguishes this technique is that the principle tensile stre sses and the fibers of the FRP are parallel to each other. The manual application of the FRP reinforcement to a member that is already in existence is what is described as the basic technique. Epoxy that is a two part cold cured bonding is used to achieve the bonding (De Lorenzis, Nanni, and La Tegola, 2000). The basic technique involves three

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12 main acting elements that include the substrate. The existing structure and the FRP composite are bonded to enhance strength. The type of material of that structure i s what is called the substrate. Therefore, the behavior of the structure that is strengthened depends mainly on how good the concrete substrate is and the way the concrete surface has been prepared. The original conditions of the concrete surface should, t herefore, be known in terms of unevenness, strength, carbonation, imperfections humidity and if possible the corrosion of the internal steel. Secondly is the resin. For a particular FRP strengthening, there should be a particular resin for it the resins in most cases are specified by the manufacture so that the can meet the necessary requirements for the installation system. The importance of the bonding agent is to assure the bond between the FRP and the substrate reinforcement (Binetruy, Chinesta & Keunin gs, 2015). The FRP composites can be categorized differently depending on their ap plication. One is the laminate. The laminates have their final stiffness strength and shape. They are always available in strips that are similar to those of steel. For the laminates, the resins present only provide the bond between the concrete and the strip only. Another type is the fabrics the fabrics are provided as dry fiber. This means that they do not have any resins inside unless they are applied. The amount of resin that is available is insufficient for polymerization. For the fabrics, the adhesive is important to bond the concrete and the sheet and also to impregnate the sheet. The second technique is the special techniques. Because of the basic requirement of FRP s ome special techniques have been put in place to speed the speed of construction. The first special technique is the automated wrapping. Wet fibers are made to wind

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13 continuously around structures with a slight angle. The technique has a main advantage of f astness. Another special technique is the prestressed FRP. Bonding a prestressed FRP externally onto the surface of concrete may be more favorable. Analytically and experimentally, it has been proven that this method is an advancement to the FRP strengthen ing technique (Li, & Shchukin, 2012). This method, however, has some of the advantages and disadvantages. The advantages of these techniques include the formation of cracks is delayed in the shear span. Stiffer behavior is provided, and the deflection at t he early stages can be controlled. The already existing cracks can be closed using the technique. Also, the shear resistance of a member is improved. Because of the reduced cracking, the technique improves the durability of the structural member (Tan, 2003 ). The technique also has some of the disadvantages. First, the technique is expensive that the normal strip bonding. The time of operation is also longer. Lastly, the technique requires that the equipment used to push the strip to the soffit of the beam i s expected to remain in place until the re sins have sufficiently hardened. The main problem with this technique that there can be the failure of the beam because of the prestressing force which is applied at the two ends of the beam. The design, therefore, requires special attention. Another important technique under the special technique is the in site fast curing using the heating devices. The curing time is reduced in this technique by using heating devices to cure the cold bond interface. This technique is mainly applied in cold weather conditions. Heating systems such as electrical heaters and heating buckets are applied. The technique is also very important when rapid strengthening is required.

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14 The fourth special technique is the use of prefabricated shapes. This technique reduces the time of installation and gives room for better quality control. These types of FRP are developed as straight strips but other forms are also available in the market like shells and angels. The systems can be used in the a pplications where wet lay up systems are used (Wuertz, 2013). Lastly, there is the FRP impregnation by vacuum technique. This system can be compared to the wet lay up and is common in the plastic industry. The concrete substrate is prepared before strength ening through grinding, sandblasting or water jet blasting. The surface is dried and cleaned before the premier is applied. After the premier is cured, the fibers are placed in directions that are predetermined. In this technique, the fabrics have channel s through which the resins flow. A bag that is vacuum is placed on top of the fibers the edges of the bag are then sealed and a vacuum pressure applied. The bag has two holes, one of the holes is used to apply vacuum pressure, and the other hole is used f or the injection of the resins. To achieve a good vacuum pressure, a special type of epoxy putty is used in the sides of the beams. The advantages of this method over the traditional methods are that the quality of composite can be improved, and the hand c ontact with the epoxy can be avoided. Waste is also reduced at the work site. 2.2.3 NSM FRP strengthening system In addition to the bonding that is done externally, FRP reinforcements can be put into the grooves that are cut into the given structural membe rs. This application is called NSM (Near surface mounted). The use of the technique of NSM reinforcement was first discovered in Europe. The technique was used to strengthen reinforced concrete in the 1950s. In 194 0 as made of reinforced concrete was to b e upgraded because of the

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15 negative moment region that had been caused by excessive settlement of the steel cage when construction was taking place. The upgrade was achieved through inserting some steel bars in grooves that were made in the concrete surface that was filled with cement mortar (Blaschko, 2003). The near surface mounting technique has many advantages when compared with the external bonding technique. The bond surface that is larger ensures there is better anchorage capacity. Higher resistance i s provided against peeling off. A higher percentage of the tensile strength can be mobilized. Apart from grooving there is no other preparation that is required. The installation time is therefore reduced. The FRP that are reinforced due the mounting setup is protected from mechanical influence by the surrounding concrete. This technique is therefore very attractive for straitening especially in the negative moment region. This type of strengthening provides protection against vandalism, ultra violet rays, fire and even elevated tempe ratures (Bakis, et al. 2002). The NSM technique has its disadvantages also. The debonding failure mode is more common in cases where more than two grooves have been cut for strengthening with the NSM bars in a beam that has li mited width due to overlapping of stress. Due to the limited width, there is an opportunity of edge breaking along the concrete section. For this reasons, enough width of the beam should be provided for the NSM technique whose main aim is to come up with a proper clear spacing between any grooves that are near each other. In some cases, an updated NSM approach is needed.

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16 2.3 E xternally bonded sheet strengthening system The process of replacing structures that already exist with new structures is in most c ases economically cost effective. It is therefore of great importance that a solution for strengthening and repairing the structures is found. Strengthening a structure that already exists is more complicated than a new structure. Traditional methods of st rengthening have been used over a long period such as the post tensioned cables, which require a lot of space. The FRP in the last few years has offered a good alternative in various engineering structures. Due to this improvement research has led to diff erent techniques. One of the techniques is the externally bonded reinforcement technique. The EBR is one of the most common methods used to strengthen structures made from reign forced concrete. While using this method, the FRP sheet is bonded adhesively t o the tension face of the member concrete. The surface preparation is mainly done to do away with contamination, remove the surface layer that may be weak, and polish the surface of the concrete. The polishing is done to promote the adherence capacity. Th e advantages of this system include the easy and quick installation, the performance costs that are quite low. There is no need for any specific labor skills while using this system and the strengthened structures can be used immediately. The system also has it disadvantages that include the brittle failure mode. The brittle failure mode is due to the premature debonding of the FRP sheet from the substrate of the concrete. Another disadvantage of the system is that the FRP materials are vulnerable against the environmental conditions like abrasion, acidic conditions, and

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17 mechanical impacts. The appearance of the structure can also be changed because the changes that are caused 2.3 .1 Externally bonded sheet techniques To postpone and eliminate the debonding of the FRP sheets, the grooving technique was invented. This technique was the one later named as externally bonded reinforcement on grooves (BROG). In this technique, the grooves are first cut on the side of the concrete member with tension. The air jet is then used to clean the grooves and filled with the epoxy resin. The surface that is saturated with the epoxy resin is then filled with the grooves, and the resin that is in excess is removed. From research and experiments, it is very clear that the long itudinal grooves are effective compared to the diagonal and the transverse grooves (Galbreath, 1966). Another technique is the EBRIG method. The grooving method was improved by penetrating the FRP sheets that were used in the EBROG into the groove. The me thod was the named EBRIG (externally bonded reinforced in grooves) this method promoted the structural performance because it provided a larger contact area between the concrete layer and the FRP. The method also modified propagation, promotes the structur al performance and crack initiation (mostfineiad and Shameli, 2013) This method is proved to be better than EBROG. Also, there is the MF EBR method. The (MF EBR) mechanically fastened and externally bonded reinforcement is a technique that is based on the MF FRP. It combines two methods of the EBR and the MF RFP. One of the advantages of these methods is that it does not need any special labor skills and surface preparation is not required. It also increases the load carrying capacity up to a level of 87%. The strengthened structures can

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18 also be used immediately. Lastly, the technique raises the ductility index compared to the original methods that have been used for a very long time (Cruz, et all, 2012) 2.3 .2 Previous applications on externa lly bonded sheet The FRP systems have many applications, especially in the civil engineering structures. The systems have for a long time been used to restore the strength of structural members that deteriorated. They can also be used in increasing the str ength of the structural member whose load carrying capacity has been increased. Before selecting the type of system that should be used, the professional designer should determine if the FRP system is applicable. In assessing the suitability of an FRP syst em, a thorough assessment should be done by the silenced design professional that includes establishing the characteristics of the existing structure. Such characteristics involve the carrying capacity and the concrete substrate (Hollaway & Leeming, 1999). The overall assessment should include a review of the designs that already exist structural analysis, and other guiding document. The system has been in use for a very long time and especially in the strengthening of the civil engineering structures. 2.3 .3 Previous research studies on externally bonded sheet FRP strengthening system With regards to the performance, the NSM strengthening systems have been well researched. The systems have been proven through experiments to be an effective. This is a metho d that is an alternative to the externally bonded strengthening system. The externally bonded systems have been used highly on aged prestressed girders ( Hassan,&Rizkalla, 2002)

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19 The externally bonded FRP have been observed by many researchers to have a de bonding failure. The debonding failure was mainly observed at the termination point of the sheets for the strengthened systems that had a short span (Hollaway & Leeming, 1999). And those that had a long span the failures were observed at the mid span. Ther e are different models that have been proposed by different researchers who predict the failure loads of the concrete members who have been reinforced through the use of FRP due to the debonding. There is very little research however that has been done on the debonding mechanism on the mid span. 2.4 Fire endurance of concrete Structures Fire resistance is the ability that the structural members possess of withstanding fire or giving protection from the fire. This ability is not limited to continue to perf orm a given structural function or to confine a fire. Unlike the structures that are steel framed, it is difficult for one to analytically determine the fire endurance of a concrete building that is reinforced this is because there is little information th at has been given to the effect of high temperature on the concrete properties. This is especially the deformation such as creep expansion and shrinkage. One of the reasons why concrete is a preferred building material over the other building materials is the property of fire resistance. The concrete structures must, however, be designed for the purpose of fire effects. The structural members of the buildings should be in a position of withstanding the live and dead loads without collapsing even when expose d to fire. This is because fire decreases the strength and the modulus elasticity of various structures both steel and concrete reinforcement. Concrete

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20 does not burn depends on the increase in temperature and the insulating properties of the concrete. The change in which the properties of concrete change are dependent on the type, of course, aggregates used. The reinforcing steel is according to research is more sensitive to temperature than concrete. From experiments, the reinforcing bars do not lose much yield strength up to a temperature of 8000f. The prestressing strands start losing their strength at about 5000f. The fire resistance is different between the prestressed and the non prestressed elements as well as the other types of concrete (Kodur, Bisb y& Green, 2007). The performance requirement during a fire exposure is the load carrying capacity. The fire rating that is always needed by the building codes is the time that the structural element can support the load when it has been exposed to standar d fire. 2.4 .1 Effect of Elevated Temperatures on CFRP Materials Despite the good characteristics of FRP that have allowed them to be used in the structures, there is a weak link in the FRP strengthening application especially at the elevated temperatures e ven though the fibers alone are in a position of retaining the strength. Although a lot of research has been done on the bond behavior at elevated temperatures, information on the behavior of the bond CFRP system when subjected to elevated temperatures has remained limited (ACI Committee 216, & Fire Resistance and Fire Protection of Structures. (1982). Most of the FRPs are combustible because of their polymer matrix. This leads to increased spread of frames and evolution of toxic smoke. Also, the adhesives and the

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21 matrices that are commonly used lose stiffness and strength above their glass transition temperature (Galbreath, 1966). 2.4 .2 Effect of Elevated Temperatures on epoxy and resin Change in temperature has an effect especially on the properties of th e thermosetting polymers and the epoxies. Before being cured, an epoxy is a composition of a curing agent and a resin. After polymerization, the entity changes into an organized crystalline structure that is referred to the glassy state. In the glassy stat e, the molecules can vibrate but cannot move because they are locked in one position. As the temperatures rise, the molecules become more lose, and they start moving apart. The polymer finally changes state to a rubbery state. This transition takes place o ver a range of temperatures (Matsumoto & Iwate ,2013). As the temperatures are increased, the thermosetting polymers show a change in their physical state, which includes the tensile strength, heat capacity, thermal expansion, electrical properties and the modulus. One of the changes that can be highly observed is the change in the linear coefficient of thermal expansion. As the epoxy moves through the tg. Its CTE at a very high rate until the value becomes tree to five times higher than the given value bel ow the tg range. The material properties at these temperatures are very different from the properties that are observed below the tg temperatures. The changes that occur to the epoxies are not permanent and are highly dependent on the amount of time that t he tg temperature is exceeded. The strength profile of an epoxy is restored as it returns to its original temperatures. Understanding the nature of this transition is important especially to the engineers so that they can be in a position of choosing the b est system for any specific application (Yourdkhani, 2014)

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22 The (T g) glass transition temperatures is one of the very crucial properties of an epoxy. This is the temperature in which the polymer changes from a hard glassy material, to a material that is ver y soft and rubbery. Epoxy materials do not reflow or melt when exposed to temperatures. This is because the epoxies are thermosetting materials, and they cross linked chemically during the curing process. Epoxies only undergo a phase change and become soft ened when exposed to temperatures. The glass transition temperature is a temperature range where the thermosetting polymer is changed from a glassy or rigid state to a state that is rubbery. Tg is not discrete but it is a continuous range of temperatures .t o come up with the T g, several factors have to be considered. One is the chemical structure of the epoxy resin. The type of hardener is also considered and the degree of cure of the epoxy resin. The epoxies are in a position of retaining the structural int egrity and the adhesive strength after being exposed to the high temperatures (Song, Casem, & Kimberley, 2015). Another term that is used in the behavior of epoxy in temperature is heat deflection under load (HDUL) this term is always shortened as (NDT) heat deflection temperature. This is a term that is used in the whole industry to give the characteristics of the thermal behavior of many resin systems. This test is the one that determines the temperature upon which a bar cured of epoxy. Each of the two temperatures is very important in the use of the epoxies. The temperatures assist in the design and engineering works. 2.4 .3 Externally bonded sheet strengthened concrete structures exposed to fire The steel members in most cases require protection so as to preserve the strength in them in case of a fire event. Concrete that is FRP strengthened require protection to

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23 prevent combustion of material, maintain strength and preserve the existing bond between them and the substrate. The use of the FRP in design and engineering comes with some obstacles. One of the concerns that have been highly considered in research is the performance of the sheets in elevated temperatures. The FRP have an organic polymer matrix. This matrix makes the susceptible to combustion whenever that is exposed to the high l evels of temperature. When the T g has exceeded the matrix of the polymer changes and becomes runny and soft. This reduces the strength. Thermomechanical behavior of CFRP strengthened c oncrete members is unknown Howev er some research that has been done shows that the FRPs lost about 50 % of their stre ngth at the temperature of 2500 o C and 3250 o C the stiffness of these materials suffered losses that are negligib le from the temperature of 4000 o C and reduced rapidly abo ve these temperatures (Song, Casem, & Kimberley, 2015). The insulated beams have shown fire endurance that is satisfactory. According to research, beams that are insulated have a fire endurance of about 81 minutes. The insulated beams on the other hand had a fire endurance of 146 min u tes. The endurance of the CFRP insulated beam is larger than that of an RC bam that is not strengthened. Once the T g of the FRP is reached, the load bearing contribution that was given by the FRP is highly reduced. Overall, the fire endurance of the FRP sheet is not that sufficient. The performance of the FRP strengthening methods is mainly dependent on the bond between the FRP and the reinforced concrete. The bond between the two is, however, susceptible to the environmental factors and fractures like humidity, temperature, and corrosive materials. Thermomechanical behavior of CFRP strengthened c oncrete members is unknown

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24 2.5 The glass transition temperature for epoxy Th e glass transition temperature T g, for any given compou nd, is the temperature that represents the range over which an epoxy that has been cured to change from a hard glassy state to a rubbery and softer state. There are three methods that have been used by the researchers to determine the glass transiti on temp eratures (Wuertz, 2013) The methods include thermo mechanical analysis, dynamic mechanical analysis and the differential scanning calorimetric. Each of the methods produces a very different result and also measures a very different phenomenon that is a ch aracteristic of the phase of transition. Under the different ial scanning calorimetric, the T g is identified by observing the change that takes place in the heat capacity of the epoxy as the temperature is increased. The principle applied here is that when a material is undergoing a state transition, less temperature is supplied to maintain it at its temperature. In this method, a small is heated together with another sample as the control experiment. The difference of heat flow betwee n the samples is obser ved. The T g is given as the temperature in which the inflection point occ urs (MacKenzie, Mulkern, Beck, & U.S. Army Research Laboratory, 2001). Another method is the thermal mechanical analysis. This technique is mainly used to come up with the coefficient of thermal expansion of the material ; the T g of the material can be determined. The principle that is applied in this technique is that when a material is transiting from a hard state to a rubbery state the changes occur on a molecular level, which result s in increased movement. During this phase transition, the coefficient of thermal expansion also increases in a noticeable way.

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25 The last method is the dynamic mechanical analysis. This technique is used to characterize the viscoelastic properties of polyme r materials. The principle used in this technique is that at the T g, the damping and stiffness of a polymeric material change. This technique is more accurate compared to the other techniques, but it requires a machine sample that is precise with a uniform thickness. 2.6 Summary and Conclusions Composites have been used highly especially in civil engineering in the past years. The early application of the FRP is dated back to the 1970s. The early applications of these composites were not satisfactory. The a pplication techniques of the FRP have been improved over time. In the current world, the FRP are highly used in the construction of new structures and also the strengthening and rehabilitation of the existing structures. The infrastructure that is deterior ating needs to be rehabilitated. The FRP have been adapted by most civil engineers to address this problem. This is because of their high strength, light weight and resistance to electrochemical corrosion, the ease of installation also makes the use of FRP s effective for engineering works. Despite the advantages that are associated with the FRPs, they can be degraded when exposed to very high temperatures. This makes their uses especially in the residential building a bit of a challenge. While the other mat erials are also susceptible to the fire degradation, research has been done on them, and the results have been included in different building codes and fire safety codes. The way the FRP materials behave under fire has not been investigated thoroughly and the way these materials behave in elevated temperatures is unknown.

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26 Table 2.1 FRP Tensile Strength and Young's Modulus ( ACI 440.2R 08) FRP Type Young`s Modulus (GPa) Tensile strength (MPa) CFRP 100 140 GPa 1,020 2,080 MPa GFRP 20 40 Gpa 520 1400 MP a AFRP 48 68 Gpa 700 1720 MPa

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27 3. Performance of Externally bonded CFRP concrete Interface Subjected to Elevated Temperatures 3 .1 General The deterioration of bridge elements is an enormous issue facing the U.S economy, espec ially the cost of maintenance. Therefor, the structural elements such as slabs, beams, and girders are usually needed to strengthen. Externally bonded carbon fiber reinforced polymer (CFRP) laminates has been widely used to strengthen and upgrade the dete riorated members. There are two different types of strengthening techniques, which are Externally laminates and near surface mounted strengthening system. Because of its benefits such as corrosion resistance, and high tensile strength, it has become one o f the most common techniques for strengthening structural elements. Concrete surfaces face a lot of different situations and weather conditions. Also, in strengthen structural members; the CFRP faces the same conditions that concrete has faced such as rain ing or fire. Under these conditions, strengthen structural members might not work efficiency or in some situations the structure will be unsafe. One of the most danger environmental conditions is fire. Fire might affect the material properties and causes d eterioration to the whole structure. Therefore, fire is an important factor that should be study and investigate. On externally bonded CFRP strengthen members there are three elements, which are main member, epoxy adhesive, and CFRP sheet. Main member c an be Concrete or steel. Fire can change the CFRP and epoxy adhesive properties because it is a polymer material. Polymer material has a thermal limit. If the material reaches the limit, the material proprieties will change and will act as an elastic behav ior. The thermal limit called the glass transition temperature (T g ). According to Blontrock et all, 1999, the glass

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28 transition temperature (T g ) of Epoxy resins has range of 50 ¡C to 90 ¡C. Therefore, it is important to analyze and investigate the flexural performance and relaxation of the strengthen members due to different temperatures, which are below and great than glass transition temperature (T g ). External bonding of FRP sheet plate has become very popular. Many concrete structures such as slabs, beams, and columns have been strengthened by CFRP external bonded sheet. As it mentioned in chapter 2, Maintenance is very expensive specially Hugh and critical elements in cities such as bridges. Many laboratory researches have approved that using carbon fiber reinforced polymer (CFRP) increase the capacity of the concrete members. However, a few researches have focused on performance of the strengthen members and the effect of temperature during time. This research is focusing in two parts. The first par t is to analyze and investigate the flexural performance of the strengthen members to elevated temperatures ranging fro m 25¡C (77¡F) to 175¡C (347¡F) This experimental program focus on investigating the behavior of the CFRP that exposed to elevated temper atures. The experimental program has two main categories. The first category is different CFRP sheet width. In this category, there are three types. First type is 0.25B. The bonded area of this type is 1" by 4" (25 mmX100 mm). The second type is 0.5B. The bonded area of this type is 2" by 4" (50 mmX100 mm). The tired type is 0.75B. The bonded area of this type is 3" by 4" (75 mmX100 mm). Second category is different CFRP sheet length First type is L e T he bonded area of this type is 2" by 3.6 (50 mmX 87 mm). The second type is 1 25 L e The bonded area of this type is 2" by 4 .5 (50 mmX114 mm). The tired type is 1. 5 L e The bon ded area of this type is 2" by 5.4 ( 50 mmX 137 mm) Figure 3.1a. The experimental program studies the performance

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29 of the CFRP g lued with concrete blocks by epoxy and subjected to elevated temperatures. The size of the concrete block is 150 mm long by 100 mm width and 75 mm height. The Mbrace epoxy adhesive was used for the two different categories. 3.2 Experimental program More t han ( 144 ) concrete blocks were prepared with compressive strength, f' c of 20 MPa (2,900 psi). In addition, the ACI standard 211.1 was followed to select the properties of concrete Figure 3.1 There are nine steps to design the mix of concrete. The dimensi ons of bricks lo ng, width, and thick are 6" (150 mm), 4"(100 mm), and 3"(75 mm), respectively. After 28 days from ca sting the bricks, CFRP sheet has clued by Epoxy Adhesive. The MBrace saturant PTA and MBrace saturant PTB were used as an epoxy adhesive. T he glue is composite of two parts, which are blue resin and hardener. According to Mbrace (2007), the weight ratio of resin to hardener has to be 3:1. In addition the epoxy adhesive required 7 days curing to make sure it reaches the maximum strength bond ed. The thermal conductivity of this material as 1.45 Btu! in/hr! ft2!"F (0.21 W/m!"K) and the glass transition temperature (Tg) is 71¡C (163¡F) (MBreace, 2007)." The Ultimate tensile strength (f epx ) and corresponding modulus (E epx ) are 55.2 MPa and 3034 M Pa, respectively. There are six different sizes of CFRP sheets. Three of them are bonded with constant length and different width. The next three categories are bonded with constant width and different long. 7 day is needed for curing after bricks bonded w ith the CFRP sheets. The next step is finding the failure point of each category, and calculates 30 % of the failure to be the maximum point to study and investigate the performance of the bricks. The research is focusing on studying different temperatures

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30 ranging from 25¡C (77¡F) to 175¡C (347¡F). In summary the test setup had four steps: Step 1: casting Concrete and 28 day curing Step 2: Bonding six different sizes of CFRP sheets to concrete with by Epoxy adhesives. Step 3: A seven day is enough fo r curing the blocks at room temperature to allow the epoxy reaches the full strength. Step 4 : Putting the concrete blocks to thermal distresses ranging from 25¡C (77 ¡F) to 175¡C (347¡F) while it is applied to tension with a constant load, which is 30 % of the failure load figure 3.2 a 3.2.1 specimen preparation There are three elements was prepared to create the specimen. First, concrete was mixed and followed by the ACI 304R specifications. The required concrete strength of concrete is 20 MPa. It is normal concrete, which consist of cement, water, fine aggregate, and course aggregate. Depending on ACI specification, there are 6 cylinders with diameter and height, 100 mm and 200 mm, receptively. These cylinders were cured at curing room for 28 days, a nd three of them were tested by compression strength machine on the 7 th day and the remain at 28 th day Figure 3.2. The results of the compression strength are shown in table 3.2 The concrete was mixed on cloudy morning day. The temperature of water is 25 5 o C. In addition, concrete was casted on steel mold. The

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31 dimension of the concrete block is 100 mm, 75 mm, 150 mm, width, height, length, respectively. All concrete blocks cleaned and smoothed before doing the second phase. Secondly, the epoxy was used to bond concrete with CFRP sheet. It is consist of two things, which are resin and hardener. The resin is a blue thick liquid and the hardener is colorless light liquid. According to manufacturing requirements, the resin has to be mixed with the hardener by 3:1 rate. In addition, curing time of the epoxy is 7 days to reach the optimum strength. Third, the CFRP sheets were cut to the size that required by the category. The strength of CFRP sheet was attached on chapter 2. After 7 day of clued CFRP shee t, the specimens are ready for testing. 3.2.2 Effective length of CFRP sheet In brief, the authors create the affective length depend on, bond strength, the thickness of epoxy, and compression strength of concrete. !" !" !" (1) Where: E p = Young's modulus of bonded plate. t p = Thickness of bonded plate. f c = Concrete cylinder compressive strength; Depend on the equation; the effective length is 87 mm. on another hand, the are three

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32 types of this category, which are Le, 1.25 Le, 1.5 Le, 87 mm, 114 mm and 137 mm, respectively. The section depends on ( Chen, and Teng, 2001). 3.2.3 Experimental phases To summarize, there are two main phases that the experimental program has been followed. Frist is to find the fa ilure point of each type. In this phase, the heat did not applied to the concrete block and they applied to tension untie failure. The second phase is to applied thermo mechanical load to the concrete blocks. These two phases will be explained more in the Instrumentation and testing procedure sectio n. 3.2.4 Heat application More than 144 concrete blocks was cured and prepared to expose to elevated temperatures from 25¡C [77¡F] to 175¡C [347 ¡F] Elevated temperatures were expose d to the concrete surface by heating pad (100 mm X 150 mm). To measure the applied temperature, there is a thermo couple attached to the surface of concrete blocks. In addition, concrete blocks' heating were monitored by IR camera to see the heat propagation. 3.2.5 Instrumentati on and testing procedure All concrete specimens were tested by MTS 20 kips machine. The machine is setup depend on which phase is. Before starting any test, machine was preheated. It takes one to two minutes to be ready for Appling the tension force. For safety, before switching the machine on, all tools and all cables have to be connected to the controlling station. While running any test, MTS recording the force, time, and displacement. In addition,

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33 there are two phase of testing concrete blocks. The fir st phase is pullout tension. In this phase, MTS machine applied gradually tension force unit the failure happened. There is one failure mode happened to concrete blocks, which is epoxy and CFRP remove from the concrete. That means CFRP and epoxy were separ ated as a one part from the surface of concrete blocks. More than 18 concrete blocks were done to find the failure point for each type of concrete specimen. Finding the failure point is very important to the second phase. The second point is to find the te mperature relaxation mode. In this phase, we applied 30 % of the failure load and applied elevated temperatures from 25¡C [77¡F] to 175¡C [347 ¡F] Each category needs at least 63 concrete blocks. Machine is setup to do two commands. First command start fro m zero unit the tension force reach the goal, which is 30% of failure point. Second command is to hold this force until 20 minutes. For these 20 minutes, the heat bed and thermo cable are attached to the concrete specimen. On the other hand, IR camera was taking thermal images while concrete block is tensioned and exposed to elevated temperature. The main advantage of using IR camera is to see the thermal propagation Figure 3.2 b. 3 .3 Test results 3 .3.1 Failure point MTS 20kips machine has applied tensio n force to 18 concrete specimens. The load was applied gradually by load rate 16.67 N/sec Figure 3.3 a Concrete blocks were tightened by steel frame. Steel frame was connected to MTS from down and the upper part of MTS tensioned the CFRP sheet. For the first category, the average failure points were 3.9 kN, 5.9 kN, 7.5 kN, 0.25B, 0.5B, 0.75B, respectively. Also, 0.198 0.300, 0.179, are the COV of 0.25B, 0.5B, 0.75B, respectively. On the second category, Le, 1.25 Le,

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34 and 1.5 Le, there are not huge failur e points between them. The average failure points were 5.7 kN, 5.9 kN, 6 kN, Le, 1.25 Le, and 1.5 Le respectively. Failure mode for all concrete blocks was the epoxy removes totally from the surface of concrete. The main purpose for testing the concrete until failure is to load 30% of these failure points to concrete blocks while testing the thermomechanic test. 3.3.2 Thermomechanical load Thermomechanical test takes 20 minutes for each specimen. Frist, MTS 20 kips is setup for two commands, which are tensioned concrete blocks until it reach 30% of ultimate load then hold that load for 20 minutes while applying elevated temperatures by heating pad. Thermocouple is recording the equal applied temperature. Also, IR camera is capturing the heat propagation More than 122 concrete blocks were examined and investigated while they are loaded by t hermomechanical load. Three concrete blocks is enough to find the behavior and performance of the relaxation behavior that happened because of t hermomechanical load at each specific temperature. For first category shows similar performance at specific temperature. Frist, 0.25 B type shows consist performance for elevated temperatures. Temperatures less than Tg show similar behavior such as 25 o C and 50 o C by COV 0.07 9 and 0.111, respectively. Also, the loss loads of temperatures less than Tg were very slight. For example, the average of three concrete blocks were applied to 50 o C shows a 15.38 % loss from sustained load which is 1.17 kN. Nevertheless, the share stres s of these specimens shows very small relaxation such as 25 o C and 50 o C, shear stress loss 15 and 27 %, respectively. In addition, the temperatures near Tg, which are 75 o C, 100 o C, 125 o C show very stabilized performance. 75 o C specimen shows an aver age loss by 0.74 kN from 1.18 kN

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35 at 1200 sec. comparing with the other concrete blocks, the standers deviation is 0.034 with COV 0.045 shown at At 100 o C the performance of the three specimen is very similar with c oefficient of variatio 0.058 and stand ers deviation 0.033. 75 o C, 100 o C, 125 o C shows losses 0.298, 0.233, and 0.213 by MPa, respectively. Shear stress for 75 o C, 100 o C, 125 o C 34%, 48%, and 53%, respectively. In addition, the temperatures so far from Tg, which are 150 o C, 175 o C show an enormous loss. 1 75 o C specimen shows an average loss by 0. 253 kN from 1.18 kN at 1200 sec with standers deviation 0.065. Because of high temperature, the percentage of loss gets almost 78 %. This will reflect negatively to the capacity of the structure Shear stress for high temperature reach 78% loss by 0.097 MPa. From comparing with the control temperature, the decreasing load ratio (#P/#t) started from 0.8 to 0.25 at 175 o C This decreasing load ratio seems to be liner figure 3.3.1 (a) to (n). Seco ndly type 0.5B indicated consistent performance for elevated temperatures. Temperatures lower than T g had similar behavior, 25 0 C by COV 0.043 and 50 0 C by COV 0.081. Loss shear stress for temperatures less than T g were slight. For example, three concrete blocks at 50 o C indicated a 12% loss from a sustained load f 1.77 kN. Shear stress of the specimens small relaxation, 25 o C had 12% shear loss while 50 o C, had 22 %,. Higher temperatures had stabilized performance. At 75 o C the specimen had an average lo ss of 1.16 kN from 1.77 kN at 1200 seconds standard deviation was 0.175 with COV 0.151. At 100 0 C the specimens behave similarly with a co efficient of variation of 0.162. And standard deviation is 0.152. Temperatures beyond T g had enormous losses of almos t 66%. Comparing with the control temperatur e the load ratio was decreasing. All details are shown in figure 3.3.2 (a) to (n).

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36 Third, 0.75 B type shows consist performance for elevated temperatures. Temperatures less than Tg show similar behavior such as 25 o C and 50 o C by COV 0. 070 and 0. 056 respectively. Also, the loss loads of temperatures less than Tg were very slight. For example, the average of three concrete blocks were applied to 50 o C shows a 13 % loss from sustained load which is 2.25 kN. Neve rtheless, the share stress of these specimens shows very small relaxation such as 25 o C and 50 o C, shear stress loss 7.1 % and 13 %, respectively. In addition, the temperatures near Tg, which are 75 o C, 100 o C, 125 o C show very stabilized perfo rmance. 75 o C specimen shows an average loss by 1.648 kN from 2.25 kN at 1200 sec. comparing with the other concrete blocks, the standers deviation is 0. 039 with COV 0. 024 At 100 o C the performance of the three specimen is very similar with c oefficient of variati o 0.065 and standers deviation 0.097. 75 o C, 100 o C, 125 o C shows losses 0.207, 0.194, 0.191 by MPa, respectively. Shear stress for 75 o C, 100 o C, 125 o C, 28.8 %, 33 %, and 34.5 %, respectively. In addition, the temperatures so high from Tg, which are 15 0 o C, 175 o C show an enormous loss. 1 75 o C spec imen shows an average loss by 1.093 kN from 2.25 kN at 1200 sec with standers deviation 0.065. Because of high temperature, the percentage of loss gets almost 53 %. This will reflect negatively to the capaci ty of the structure. Shear stress for high temperature reach 53 % loss by 0.136 MPa. From comparing with the control temperature, the decreasing load ratio (#P/#t) started from 1.8 to 0.85 at 175 o C figure 3.3.3 (a) to (n). Second category also indicted th e same performance. Type L E indicated consistent performance for elevated temperatures. Temperatures lower than T g had similar behaviour, 25 o C by COVo0.054 and 50 o C by COV 0.026. At 50 o C the loss was

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37 12.22 % from sustained load of 1.71 kN. 25 o C had she ar stress of 3.5% while and 50 o C had 12.8 %. At high temperatures the percentage loss is high with shear stress of almost 75% that has a negative impact on the capacity of the structure. Figure 3.3.4 (a) to (n) illustrate all details for each specific tem perature. Second 1.25 Le type shows consist performance for elevated temperatures. Temperatures less than Tg show similar behavior such as 25 o C and 50 o C by COV 0. 055 and 0. 093 respectively. Also, the loss loads of temperatures less than Tg were very slight. For example, the average of three concrete blocks were applied to 50 o C shows a 15.1 % loss from sustained load which is 1.770 kN. Nevertheless, the share stress of these specimens shows very small relaxation such as 25 o C and 50 o C, shear stress loss 3.7 and 15.1 %, respectively. In addition, the temperatures near Tg, which are 75 o C, 100 o C, 125 o C show very stabiliz ed performance. The 75 o C spec imen shows an average loss by 1.28 kN from 1. 77 kN at 1200 sec. C omparing with the other concrete b locks, the standers deviation is 0. 068 with COV 0. 052 At 100 o C the performance of the three specimen is very similar with c oefficient of variatio 0.113 and standers deviation 0.138. 75 o C, 100 o C, 125 o C shows losses 0.262, 0.236, 0.223 by MPa, respe ctively. Shear stress for 75 o C, 100 o C, 125 o C 23 %, 30 %, and 34 %, respectively. In addition, the temperatures so far from Tg, which are 150 o C, 175 o C show an enormous loss. 1 75 o C specimen shows an average loss by 0. 45 kN from 1.770 kN at 1200 se c with standers deviation 0.120. Because of high temperature, the percentage of loss gets almost 75 %. This will reflect negatively to the capacity of the structure. Shear stress for high temperature reach 74 % loss by 0.087 MPa. From comparing with the co ntrol

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38 temperature, the decreasing load ratio (#P/#t) started from 1.45 to 0.45 at 175 o C This decreasing load ratio seems to be liner figure 3.3.5 (a) to (n). Type 1.5 L e indicated similar performance for elevated temperatures. At 25 o C and 50 o C by COV 0.075 and 0.023, respectively with slight loss loads. Shear stress for the specimen had small relaxation, 25 o C had 4%shear stress while 50 o C had 19%. Temperature close to T g (75, 100, 125 0 C) showed stabilized performance. Shear stress was 75 o C (22%), 1 00 o C g (27%) and 125 o C (38%). Temperatures far beyond T g had enormous loss. Due to the high temperatures the percentage loss was 65%. losses of shear stress are shown in figure 3.3.6 (a) to (n). For the two main categories, the performance of each spec imen shows consistent behavior. First, with different CFRP sheet width, 0.75B has showed very efficient performance comparing with the anther two types. The total loss of each specific temperature at 0.75B was the lowest loss of each individual temperature However, the behavior of 0.25 B is not efficient, because the maximum loss reach 75 % of the 30% of ultimate load shown figure 3.3.7 (a) to (c) and 3.3.8 (a) to (c) With increasing the width of CFRP sheet, the total shear stress loss decreased signific antly from 78 % to 55%, 0.25B to 0.75B respectively. This decreasing ratio seems to be liner. However, the second category (different L of CFRP sheet) shows disparate performance unlike first category. The total shear stress loss generally is decreasing sl ightly with increasing in the length of CFRP sheet. Fro example, 1.25Le show the maximum percentage loss by 75 %. 1.5 Le shows the lowest loss percentage by 65 % at 175 o C

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39 3.4 Thermal propagation at mid span of the concrete block All concrete spec imens were exposed to elevated temperatures. The surface of concrete blocks was heated by the heating bed and recorded by thermocouple. We can control the applied heat from heating bed and the thermocouple attached to the surface of concrete blocks. Howeve r, it is imposable to see the thermal propagation inside individual concrete specimen. Therefore, FLIR E8, Infrared Camera (IR camera) with MSX has been used for all elevated temperatures. IR camera has been used to capturing the thermal propagation inside concrete blocks. This will reflect to our tests to see the relationship between the specific temperature and the thermal propagation inside concrete blocks. Each specific temperature was pictured for 1200 sec for two times, one while loading and without. IR camera take shoot each 120 sec. At middle of span, there are four points are pointed to read the temperature inside the block. They named by 1 to 4, where point 1 is the nearest point from heating bed by 18.75 mm. Also, the distance between each point i s 18.75 mm. For 50 o C there are two specimens were used to picture the thermal propagation. Temperatures less than Tg show very less thermal propagation at mid span. At 600 sec, the temperature at mid span was 23.4 o C. After 1200 sec, the temperature reached 29 o C figure 3.4.1. Also, temperatures near Tg such as 75 o C show similar thermal propagation than temperatures lower than Tg. At 1200 sec, 75 o C had a temperature at mid span 32 o C figure 3.4.2. On the other hand, the temperatures higher than the Tg such as 100 o C 125 o C 150 o C show high thermal propagation than the temperatures less than Tg figure 3.4.3 to figure 3.4.5. On other words, with increasing applied temperature, the thermal propagation increases significantly. For instance, while app lying 175 o C to concrete

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40 blocks, at 120 sec the inducted temperature is equal to applying 75 o C for 1200 sec, by 32 o C Comparing 175 o C to loss strength, concrete specimen loss than 75 % of the applied load figure 3.4.7 (a) to (g) Also All contour lines and summary were shown in figure 3.4.8 to 3.4.12 3.5 Temperature dependent Model There are two different models, which are Thermal relaxation Model and Time logarithm model. First, Thermal relaxation model d epend on the performance of the behavior of con crete specimens. There are three phases happened while applying thermomechanical test. The first phase is to applying gradually tension force until a 30% of ultimate load. The second phase is to determine the relaxation happened to concrete specimens. The third phase is to find the final shear stress. 3.5.1 Thermal relaxation Model to 0.25 B type !" !"# !" !"# !""""""""""""""""""""""""""""""""""""""""""""#$%"&"'"("'" !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# Where: t f = 835.34e 0.003T $ = 0.3612e 0.002T t max = 0.0002T + 70.737 % f = 0.4964e 0.007T % max = 2E 05T + 0.4634, T = temperature by ¡C t f is the time that finial shear stress (% f ) start. t max is the time that shear stress reaches maximum shear stress (% max ). $ is an empirical coefficient This model will be repeated with all different types to illustrate a global model for each category (see figure 3.5.1). (2)

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41 3.5.2 Thermal relaxation Model to 0. 5 B type !" !"# !" !"# !""""""""""""""""""""""""""""""""""""""""""""#$%"&"'"("'" !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# Where: t f = 897.65e 0.003T = 0.5094e 0.002T t max = 5E 05T + 106.56 f = 0.3708e 0.006T max = 2E 05x + 0.3381, T = temperature by !" these specific values were molded from experimental data. Also, the date was feed to the second equation to find the $ ( empirical coefficient ). The regression trend line of each parameter is shown in figu re 3.5.2. 3.5.3 Thermal relaxation Model to 0. 75 B type !" !"# !" !"# !""""""""""""""""""""""""""""""""""""""""""""#$%"&"'"("'" !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# Where: t f = 853.9e 0.002T = 0.505e 0.004T t max = 0.0005T + 135.17 f = 0.2987e 0.004T max = 2E 06T + 0.2926 T = temperature by !" The third type is 0.75 B, which is 200mm X 150 mm. all regression chart and comparing chart with experimental specimens are show in 3.5.3. (3) (4)

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42 3.5.4 Thermal relaxation Model to First category (Global model) !" !"# !" !"# !"""""""""""""" !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$%$&$'$&$ !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# W here: t f = = 865.27e 0.002T = 0.453e 0.003T t max = 110 f = 1.0474e 0.005T max = 1 T = temperature by !" Figure 3.5.4 compares between the model and the experimental work. Normalizing shear stress for each type that exposed to the same temperature is used to illustrate the global model. The limits of this model is from 1" to 3" width with 4" length. 3.5.5 Thermal relaxation Model to Le !" !"# !" !"# !""""""""""""""""""""""""""""""""""""""""""""#$%"&"'"("'" !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# Where: t f = 856.66e 0.003T $ = 0.4618e 0.004T t max = 0.0045T + 100.51 % f = = 0.4874e 0.008T % max = 2E 05T + 0.3668 T = temperature by ¡C For second category, the same processes were repeated to illustrate the Global model. Figures 3.5.5 show the regression line and compering results for elev ated temperatures. (5) (6)

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43 3.5.6 Thermal relaxation Model to 1.25 Le !"# !"# !" !"# !""""""""""""""""""""""""""""""""""""""""""""#$%"&"'"("'" !"# !"# !"# ! !"# !"# ! !"# !!!!!! !! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# Where: t f = 1003.6e 0.005T = 0.491e 0.004T t max = 0.0014T + 108.93 f = = 0.4027e 0.008T max = 2E 06T + 0.3025 T = tem perature by !" # 1.25 Le shows small different results between relaxation results from modeling and experimental results. The comparing results and regression equations were shown in Figure 3.5.6. 3.5.7 Thermal relaxation Model to 1.5 Le !" !"# !" !"# !""""""""""""""""""""""""""""""""""""""""""""#$%"&"'"("'" !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!! !"#$ !"# Where: t f = 942.14e 0.005T = 0.4349e 0.004T t max = 0.0012T + 108.58 f = 0.2857e 0.005T max = 1E 05T + 0.2558, T = temperature by !" # $%&#'()*#*+,-.#/%0,(&123#&-)4'*)#)5%6)#)101'(&#&-)4'*)#%7#-8,-&10-2*('#(9 -&(3-#)5-(&# )*&-)):#$134&-#;:<:=#1''4)*&(*-)#*5-#&-3&-))1%2#->4(*1%2)#(2?#/%0,(&123#&-)4'*)# @-*6--2#-8,-&10-2*('#(2?#0%?-'123:##### # # # # (7) (8)

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44 3.5.8 Thermal relaxation Global Model With different length !" !"# !" !"# !""""""""""""""""""""""""""""" !!!!!!!!!!!!!!! !"#$%$&$'$&$ !"# !"# !"# ! !"# !"# ! !"# !!!!!!!! !"#$ !"# !"#"!" ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !"#$ !"# Where: t f = 934 .1e 0.004T = 0.4202e 0.004T t max = 5E 16x + 106.67 f = 1.2019e 0.007T max = 1 T = temperature by !" For different length, this global model illustrates the performance of each average shear stress exposed to elevated tempera tures. The limits of this model is from 3.6" to 5.4" length, with width 2". Figure 3.5.8 shows the comparing between experimental and modeling. 3.5.9 Time logarithm model 3.5.10 Time logarithm model 0.25B Y= a b log (T) (10) Where: a = 0.465 MPa b= 0.06 01 e 0.0087 T T= temperature by ¡C Another way to model the performance of average shear stress is to logarithm time. This will make the experimental results straight lines. This model is repeated for each type to illustrate the global model for each category. Comparing result is shown in figure 3.6.1. 3.5.11 Time logarithm model 0.5B Y= a b log (T) (11 ) Where: a = 0.351 MPa b= 0.0403 e 0.011 T T= temperature by ¡C Comparing result is shown in figure 3.6.2. (9)

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45 3.5.12 Time logarithm model 0. 7 5 B Y= a b log (T) (12 ) Where: a = 0.291 MPa, b= 0.0321 e 0.0105 T T= temperature by !" Comparing result is shown in figure 3.6.3. 3.5.13 Time logarithm Global model with different CFRP Width Y= a b log (T) (13 ) Where: a = 1 MPa b= 0.0457 e 0.0097 T T= temperature by !" Comparing result is shown in figure 3.6.4. 3.5.14 Time logarithm model Le Y= a b log (T) (14 ) Where: a = 0.372 MPa b= 0.023 e 0.0142T T= temperature by ¡C Comparing result is shown in figure 3 .6.5. 3.5.15 Time logarithm model 1.25 Le Y= a b log (T) (15 ) Where: a = 0.320 MPa b= 0.0247 e 0.0135 T T= temperature by ¡C Comparing result is shown in figure 3.6.6.

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46 3.5.16 Time logarithm model 1. 5 Le Y= a b log (T) (16 ) Where: A= 0.256 MPa b= 0.0351 e 0.0107 T T= temperature by ¡C Comparing result is shown in figure 3.6.7. 3.5.17 Time logarithm Global model with different CFRP length Y= a b log (T) (17 ) Where: a = 1 MPa b= 0.0295 e 0.0123 T T= temperature by ¡C Comparing result is shown in figure 3.6.8. 3.6 Summary and C onclusion More than 144 concrete blocks were investigated in this chapter. All blocks has been exposed to elevated temperatures 25 o C to 175 o C. there are two main categories were illustrate d in this chapter, which are different CFRP sheet width and Different length. Also, IR camera has been used to capture the heat propagation inside strengthen concrete blocks. Also, the correlation between all parameters is shown in table 3.6. There are som e conclusions are illustrated in this section. Applying higher temperatures than Tg reflects to the performance of the strengthen system negatively. In some cases the total loss reaches 75 %. This enormous loss percentage happened because the epoxy was ch anged from solid condition to rubber condition.

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47 Increasing bonding area reflects to performance of system positively. For example, 0.25B shows the highest loss for elevated temperatures. However 0.75B shows the lowest loss for the same exposed temperatures IR camera shows the gradually propagation for each 2 min. with increasing temperature the propagation increases. In this chapter, average shear stress was modeled depend on the experimental work. There are two temperature dependent models, which are lo garithm time and divided the performance of relaxation to three steps.

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48 Table 3. 1. Concrete mix design W/C 68% Cement (kg/m 3 ) 279 Water (kg/m 3 ) 190 Aggregate (kg/m 3 ) 1116 Sand (kg/m 3 ) 805 Table 3.1 a CFRP sheets sizes all unit by (in) W idth CFRP bonded length CFRP unbounded length 0.25 B 1 4 4 0.5 B 2 4 4 0.75 B 3 4 4 L 2 3.6 4 1.25 L 2 4.5 4 1.5 L 2 5.4 4 Table 3 .2. Compressive strength of concrete cylinders 28 days Specimen Compressive Stress (MP a) M1 17.22 M2 21.2 5 M3 19.66 Average 19.37

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49 Table 3.6 : Correlation between all parameters Figure 3.2 a : specimens ready for test Figure 3.2 b : Applied thermomechanic load # Variable width Variable Length Temperature % f Variable width A # A # B # C B:DEE # Variable Length A # A # B # C B:;
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50 (a) (b) (c) (d) (e) (f)

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51 (g) (h) (i) (j) (k) (l)

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52 (m) (n) Figure 3.3.1 result of three specimens of 0.25 B, (a) and (b) 25 ¡C (c) and (d) 50 ¡C (e) and (f) 75 ¡C (g) and (h) 100 ¡C (i) and (j) 1 25 ¡C (k) and (l) 150 ¡C (m) and (n) 1 75 ¡C

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53 (a) (b) (c) (d) (e) (f)

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54 (g) (h) (i) (j) (k) (l)

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55 (m) (n) Figure 3.3. 2 result of three specimens of 0.5 B, (a) and (b) 25 ¡C (c) and (d) 50 ¡C (e) and (f) 75 ¡C (g) and (h) 100 ¡C (i) and (j) 1 25 ¡C (k) and (l) 150 ¡C (m) and (n) 1 75 ¡C

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56 (a) (b) (c) (d) (e) (f)

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57 (g) (h) (i) (j) (k) (l)

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58 (m) (n) Figure 3.3. 3 result of three s pecimens of 0.75 B, (a) and (b) 25 ¡C (c) and (d) 50 ¡C (e) and (f) 75 ¡C (g) and (h) 100 ¡C (i) and (j) 1 25 ¡C (k) and (l) 150 ¡C (m) and (n) 1 75 ¡C

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59 (a) (b) (c) (d) (e) (f)

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60 (g) (h) (i) (j) (k) (l)

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61 (m) (n) Figure 3.3. 4 result of three specimens of Le, (a) and (b) 25 ¡C (c) and (d) 50 ¡C (e) and (f) 75 ¡C (g) and (h) 100 ¡C (i) and (j) 1 25 ¡C (k) and (l) 150 ¡C (m) and (n) 1 75 ¡C

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62 (a) (b) (c) (d) (e) (f)

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63 (g) (h) (i) (j) (k) (l)

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64 (m) (n) Figure 3.3. 5 result of three specimens of 1.25 Le, (a) and (b) 25 ¡C (c) and (d) 50 ¡C (e) and (f) 75 ¡C (g) and (h) 100 ¡C (i) and (j) 1 25 ¡C (k) and (l) 150 ¡C (m) and (n) 1 75 ¡C

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65 (a) (b) (c) (d) (e) (f)

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66 (g) (h) (i) (j) (k) (l)

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67 (m) (n) Figure 3.3. 6 result of three specimens of 1.5 Le, (a) and (b) 25 ¡C (c) and (d) 50 ¡C (e) and (f) 75 ¡C (g) and (h) 100 ¡C (i) and (j) 1 25 ¡C (k) and (l) 150 ¡C (m) and (n) 1 75 ¡C

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68 (a) (b) (c) (d) Figure 3.3.7 (a): the different loss ratio by (kN/sec), (b) the total loss by kN, (c) : the total loss by percentage, (d) the total shear stress loss by MPa for 0.25B, 0.5B, and 0.75B.

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69 (a) (b) (c) (d) Figure 3.3.7 (a): the different loss ratio by (kN/sec), (b) the total loss by kN, (c) : the total loss by percentage, (d) the total shear stress loss by MPa for Le, 1.25 Le, and 1.5 Le.

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70 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k ) Figure 3.4.1: thermal propagation for block heated to 50¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.

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71 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k ) Figure 3.4.2 : thermal propagation for block heated to 75 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.

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72 (a) (b) ( c) (d) (e) (f) (g) (h) (i) (j) (k ) Figure 3.4.3 : thermal propagation for block heated to 100 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.

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73 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k ) Figure 3.4.4 : thermal propagation for block heated to 125 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.

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74 (a) (b ) (c) (d) (e) (f) (g) (h) (i) (j) (k ) Figure 3.4.5 : thermal propagation for block heated to 150 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.

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75 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k ) Figure 3.4.6 : thermal propagation for block heated to 175 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 18; (k) 20 minutes.

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76 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Figure 3.4.7 : thermal propagation for block heated to 75 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 20 minutes.

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77 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Figure 3.4.8 : thermal propagation for block heated to 100 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 20 minutes.

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78 (a) (b ) (c) (d) (e) (f) (g) (h) (i) (j) Figure 3.4.9 : thermal propagation for block heated to 125 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 20 minutes.

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79 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Figure 3.4.10 : thermal propagation for block heated to 150 ¡ C at: (a) 0; (b) 2; (c) 4; (d)

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80 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Figure 3.4.11 : thermal propagation for block heated to 175 ¡ C at: (a) 0; (b) 2; (c) 4; (d) 6; (e) 8; (f) 10 ; (g) 12; (h) 14; (i) 16; (j) 20 minutes.

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81 (a) (b) (c) (d) (e) Figure 3.4.12 : thermal propagation for blocks: (a) 75 ¡ C (b) 100 ¡ C (c) 125 ¡ C (d) 150 ¡ C (e) 175 ¡ C, for 20 minutes

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82 (a) (b) (c) (d) (e ) (f) (g)

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83 (h ) (i) (j) (k ) Figure 3.5.1 : compares between model and experimental for 0.25B: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress (% f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ). (k) $ is an empirical coefficient

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84 (a) (b) (c) (d) (e ) (f) (g)

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85 (h ) (i) (j) (k) Figure 3.5.2 : compares between model and experimental for 0.5B: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress (% f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ). (k) $ is an empirical coefficient

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86 (a) (b) (c) (d) (e ) (f) (g)

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87 (h ) (i) (j) (k) Figure 3.5.3 : compa res between model and experimental for 0.75B: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress (% f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ). (k) $ is an empiri cal coefficient

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88 (a) (b) (c) (d) (e ) (f) (g)

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89 (h ) (i) (j) (k) Figure 3.5.4 : compares between model and experimental for global model for differe nt width : (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress (% f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ), (k) $ empirical coefficient

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90 (a) (b) (c) (d) (e ) (f) (g)

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91 (h ) (i) (j) (k) Figure 3.5.4 : compares between model and experimental for Le: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress (% f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ), (k) $ empirical coefficient

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92 (a) (b) (c) (d) (e ) (f) (g)

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93 (h ) (i) (j) (k) Figure 3.5.5 : compares between mod el and experimental for 1.25Le: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress ( % f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ). (k) $ empirical coefficient

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94 (a) (b) (c) (d) (e ) (f) (g)

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95 (h ) (i) (j) (k) Figure 3.5.6 : compares between model and experimental for 1.5Le: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡ C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress % f ( i) time of maximum shear stress t max (j) maximum shear stress % max (k) $ empirical coefficient

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96 (a) (b) (c) (d) (e ) (f) (g)

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97 (h ) (i) (j) (k) Figure 3.5.7 : compares between model and experimental for 1.5Le: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress % f ( i) time of maximum shear stress t max (j) maximum shear stress % m ax (k) $ empirical coefficient

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98 (a) (b) (c) (d) (e ) (f) (g)

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99 (h ) (i) (j) (k) Figure 3.5.8 : compares between model and experimental for global model for different length: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) finial shear stress (% f ), ( i) time of maximum shear stress t max (j) maximum shear stress (% max ), (k) $ empirical coefficient

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100 (a) (b) Figure 3.6.1 shows the temperature dependent For 0.25 B: where (a) is A value and (b) is the slop b. (a) (b) Figure 3.6. 2 shows the temperature dependent For 0.5 B: where (a) is A value and (b) is the slop b. (a ) (b) Figure 3.6. 3 shows the temperature dependent For 0.75 B: where (a) is A value and (b) is the slop b.

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101 (a) (b) (c) (d) (e ) (f) (g)

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102 (h ) (i) Figur e 3.6.4 : shows the temperature dependent model for global model for different width: (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) maximum shear stress A (j) slob b.

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103 (a ) (b) Figure 3.6. 5 shows the temperature dependent For Le: where (a) is A value and (b) is the slop b. (a) (b) Figure 3.6. 6 shows the temperature dependent For 1.25 Le: where (a) is A value and (b) is the slop b. (a ) (b) Figure 3.6. 7 sho ws the temperature dependent For 1.25 Le: where (a) is A value and (b) is the slop b.

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104 (a ) (b) (c) (d) (e ) (f) (g)

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1 05 (h ) (i) Figure 3.6.8 : shows the temper ature dependent model for global model for different length : (a) 25 ¡C (b) 50 ¡C (c) 75 ¡C (d) 100 ¡C (e) 1 25 ¡C (f) 150 ¡C (g) 1 75 ¡C (h) maximum shear stress A (j) slob b.

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106 4. Performance of Externally bonded CFRP RC beam Subj ected to Elevated Temperatures 4.1 General In the United States, about 9.4 billion dollars are needed annually for maintaining the deterioration of the bridges. This amount is significant and reflects negatively on the country's economy. As a result, the u pgrading of the nation's bridges is needed to overcome this challenge. In essence, the maintenance of bridges, slabs, girders, as well as beams requires more maintenance as compared to other structural elements that make up the bridge. In addition, FRP com mends that the most operational upgrades play a critical role in strengthening the bridge materials. More especially, carbon fiber reinforced polymer (CFRP) has been broadly applied as the primary material for strengthening bridges. Several factors favor t he use of CFRP in bridge maintenance. Among these factors are its lightweight and high tensile strength features. From the 1990s, structural engineers have faced several challenges in using CFRP material to strengthen bridges. On the other hand, several d ifferent systems of strength have been applied. Among the most useful C FRP systems is what is regarded as the wet layup system. When using this system, the CFRP sheet is laid by hand. The major feature, which distinguishes this method from others, is that the FRP fibers and the principle of tensile stress are parallel to each other. FRP reinforcement is applied manually to a member that already exists. It is what is regarded as the basic technique. Nevertheless, temperature changes have an impact more espec ially on the properties of the epoxies and the thermosetting polymers. Fire can also change the epoxy and CFRP adhesive properties since it is a polymer material. A thermal limit is among the setbacks for using a polymer material for the maintenance of bri dges. When the materials attain their limit,

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107 their properties will transform and behave like an elastic material. The thermal limit is what is regarded as the glass transition temperature (Tg). Blontrock et al. (1999) argues that the glass transition tempe rature of the Epoxy ranges between 50 ¡C and 90 ¡C. It means that it is vital for engineers to not only investigate, but also analyze the flexural relaxation and performance of the strengthen members because of the diverse temperatures that are greater and below the glass transition temperature. The factor reflects on the main member's performance, steel or concrete, negatively. Currently, C FRP sheet plates are applied in external bonding, which has gained a lot of popularity in structural engineering. Seve ral concrete structures like columns, beams, as well as slabs are strengthened by the use of CRFP external bonded sheet. More especially beams have been reinforced through several techniques like shear strengthening and flexural strengthening. According t o the researches by several laboratories, the use of CFRP increases the concrete members' capacity. However, few studies have analyzed strengthen members' performance, as well as the impact of temperature throughout time. This study focuses on two categori es. The first category is to investigate and look into the strengthen beams' performance exposed to increased temperatures that range between 75 o C and 150 o C. In this first grouping specific temperatures will be exposed to the CFRP surface of the beams f or 20 minutes meanwhile two points constant load is applied shown in figure 4 1a The objective of the first category is to study and investigate the association between particular temperature and material strain. The second class will involve the applicat ion of three points bending shown in figure 4 1b Within this classification the study will focus on the ultimate load and the failure mode. These points of focus will be compared, as well as investigated

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108 with a specific temperature. 4.2 Experimental pro gram Concrete compressive strength, fc, of 20 MPa (2,900 psi) was used in the preparation of 15 strengthen beams. Nine steps are required in the concrete mix design. The dimensions of the beam were 47.5" (1200 mm) long, 4"(100 mm) width, and 6.5"(165 mm th ick) respectively shown in figure 4 2 The RC beams were cast and left for 28 days. Thereafter, the CFRP was glued by the epoxy adhesive. The epoxy adhesive used was the MBrace saturant PTB and the MBrace saturant PTA. The glue applied was composed of tw o parts, which are hardener and blue resin. Mbrace (2001) states that the resin to hardener weight ratio has to be 3:1. On the other hand, the epoxy adhesive needed a week of curing to ascertain it attains the optimum strength bonded. Tg was 71¡C (163¡F), and the thermal conductivity of this material was 1.45 Btuin/hrft2"F (0.21 W/m"K). The modulus (Eepx) and the corresponding Ultimate tensile strength (fepx) were 3034 MPa and 55.2 MPa, respectively. CFRP sheets are of two different sizes. The first si ze measures 900mm X 100mm. The primary aim of this sheet was to strengthen the RC beam. The second size measures 200mm X 400mm and its purpose is to prevent the CFRP from debonding. A week is needed to cure after the beams are debonded with the CFRPP sheet s. In the first category, at least six beams are exposed to four bending points for a duration of 20 minutes. A half of the ultimate load Pu is applied as a sustained load meanwhile the beams are exposed to increased temperatures. The objective of the f our points bending is comparing between and investigating elevated temperatures and strain. The second class involves studying the performance and behavior of strengthen beams that are exposed to three points

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109 bending. The second category beams are exposed to increased temperatures for & 1, 1 ( hours. 4.2.1 specimen preparation The specimen was created through the use of three elements. First, the beams were designed. 2#3 bars were applied for all the beams with fy =60 ksi. Thereafter, shear stirrups were distributed, each 3 inches. The mixing of concrete was done followed by the specifications of ACI 304R. The required strength of concrete was 20 MPa, which is the normal concrete. Accordingly, normal concrete comprises of water, cement, fine aggregate, as well as course aggregate Following the ACI specifications, six cylinders 100 mm diameter and 200 mm height respectively were available. The cylinders were cured at a room for four weeks. Three of the cylinders were tested through the compression strength machine on the 7th day; the rest were tested on the 28th day. Water temperature was maintained at 25 5 o C. The beams were cast using steel mold. The epoxy applied in bonding CFRPP sheet with concrete followed thereafter and it consisted of two things: th e hardener and the resin The hardener is a light colorless liquid while the thick blue liquid is the resin. The manufacturing requirements require that the resin is mixed with the hardener through a 3:1 rate. In addition, the epoxy was cured for a week, w hich is seven days to attain maximum strength. The CFRP sheets were cut according to the size required by the category. After a week of clued CFRPP sheet, the next step was completed. The subsequent step comprised the preparation of the beams for testing. Cell gauge, bi gauges, strain gauges, thermocouple, as well as displacement measures were attached to the beams before the testing of the beams started shown in figure 4.2.1a, b, and c

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110 4.2.2 Experimental category The research focused on two categories The first was investigating and studying the strengthen beams' performance when exposed to increased temperatures between 75 o C and 150 o C. This category involved the exposure of particular temperature to the CFRP beams surface for 20 minutes meanwhile a cons tant load was applied in two points. The first group aimed at studying and investigating the association between specific temperature and strain. At least six beams were tested with point bending. The precise temperatures that were applied to the beams wer e 75 oC, 100 oC, 125 oC, 150 oC respectively. This category involved the exposure of beams to a half of the ultimate load. The second group included the application of three points to bending. The precise temperatures that were applied to the beams at diff erent time intervals were 75 o C, 100 o C, 125 o C, and 150 o C. At first, all the temperatures were used for a half an hour. At 150 oC, four beams were tested for & 1, and 1 ( hours for every beam. The test was focused on the ultimate load, as well as the failure mode. The focusing points were compared and investigated with an elevated temperature. 4.2.3 Heat application The experimental program followed two major phases. Heating bed of 150mmX 100mm was used for the two categories. IR camera was used to ca pture thermal propagation. The heat bed was attached at the beams' mid span. 4.2.4 Instrumentation and testing procedure The MTS 20 kips machine was used to test all the strengthen beams. The

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111 setup of the machine was done based on the phase of the test. The machine was preheated before beginning. It took 2 minutes to apply the compression load. To ensure safety before the machine is turned on, all cables and tools were connected to the controlling station. Meanwhile, running any test, the commuter record ed the time, strain, force, as well as the displacement. Furthermore, two categories of beam testing were conducted. The first class involved the four bending points. Throughout this phase, the MTS machine applied gradual compression load unit until failur e occurred. Four strengthen and unstrengthen beams were tested at room temperature with the aim of figuring out the ultimate force. In the second process, finding the point of failure is crucial. After this, 50% of the failure load was applied along with t he increased temperature ranging between 75¡C and 150¡C. The setup of the machine is done to execute three commands. The first command begins from zero to 50% of the failure point. The second command holds the force for first 20 minutes. During this time, the thermo cable and the heat bed are connected to the concrete. Conversely, IR camera takes images meanwhile beams are exposed to increased temperature and compressed. The key benefit of the IR camera is to observe thermal propagation. The second category involves three point loading. Throughout this phase, MTS machine applied gradual compression load until failure occurred. The ultimate load was determined by testing one strengthen beam at room temperature. Finding the point of failure was also crucial in the second process. Later, a 60% failure load and temperatures ranging between75¡C and 150¡C were applied. The machine was set to execute three commands. The first command started from zero to 60% of the failure point. The second command was holding the f orce for the first 30 minutes. During this time, the thermo

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112 cable, the heat bed, and the concrete specimen were connected. The IR took the thermal images while beams were exposed to increased temperature and compressed. For the elevated temperatures of 150 ¡C, four beams were tested with increased time & 1, and 1 ( hours. 4.3 Test results 4.3.1 four points bending test Compression force was applied to the eight beams using the MTS 20kips machine. The force was gradually applied through a displacement r ate of 2mm/min shown in figure 4.3 The beams were placed in two simple supports. After that, six strain gauges were connected, three right to it and three left of the heating bed. The first beam was unstrengthen beam and failed at 48kN. All resulting char ts are shown in figure 4.3.1I. At 42 kN, the beam started cracking the experienced shear failure. It is the similar to a theoretical design ultimate force, which is 53 kN. The second beam to be tested was the strengthen beam that failed at 76 kN. It was mo re than 52% of the unstrengthen beam capacity shown in figure 4.3.1II The goal of this test was to compare strain and temperature. For the temperature near Tg, one of the beams was tested at 75 ¡C by first applying 50% of 76 kN for the first 20 minutes. T he load was then increased until failure. From this test the strain gauge near the heating bed indicated high strain as compared to the strain gauge far from the heating bed Figure 4.3.1III The goal was to focus on the first 20 minutes. At 75 ¡C gauge nu mber 10 was the highest strain reading that was the nearest strain gauge from the heating bed, 0.0012. When the temperature increased to 100¡C, the strain gauge indicated same

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113 behavior than the 75 ¡C beam. However, the beam with the high temperature showed more strain than the beam with lower temperature. At 100 ¡C beam, the highest strain rea ding was gauge number nine by 0 .0015 because it was near to the heating bed shown in figure 4.3.1 IV For elevated temperatures than Tg like 125 ¡C and 150 ¡C, the fai lure mode, as well as the strain reading indicated same responses shown in figure 4.3.1 V and figure 4.3.1 VI However, there was a rise in the strain readings' trend. For instance, 125 ¡C showed lesser strain at gauges next to the heating bed as compared to 150 ¡C when some sustained load is applied, that is 35kN. The largest strain reading was by 0.0021 in 150 ¡C beam. The least strain reading was gauge number seven at 75 ¡C beam that was the farthest gauge by 0.00 0 7 from the heating bed under a sustained force. When comparing the various applied temperatures under a sustained force the association between temperature and strain is a proportional relationship Figure 4.3.1 VII This implies that increase in temperature increases the strain All the beams h ave the same mode of failure that is the shear failure. This shear leads w arping CFRP sheet to be debonding In addition, for all the beams, the major crack started from the point where force is applied and continued to the point of support. Throughout the applied sustained load for the first 20 minutes, the beam's displacement was small less than 2mm. 4.3.2 three points bending test The test is like the one above, but seven beams were used instead of 8. The first beam to be tested was the stre ngthenin g beam that failed at 53 kN. The aim of the test was comparing between ultimate load and temperature. One of the beams was tested at 75 ¡C for the temperature near Tg. 6 0 % of 53kN was applied for 30 minutes and increased until failure occurred. The failure load was smaller from this beam than the

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114 control beam by 50kN shown in figure 4.3.2 (I) The displacement was 4 mm at 30 minutes In addition, in the nine gauge's, 0.002 was the maximum strain reading, which was next to the mid span. Increased temperature like 100 ¡C failure point indicated the same behavior as compared to the 75 ¡C beam. However, the 100 ¡C beam designated less ultimate load Pu than the 75 ¡C beam. At 100 ¡C beam, the optimal force was 50kN shown in figure 4.3.2 (II) For increased temp eratures than Tg like 125 ¡C, and 150 ¡C, mode failure, and strain reading show the same responses. However, there was a reduction in the failure load trend. For instance, 125 ¡C indicates higher ultimate load as compared to 150 ¡C shown in figures 4.3.2 ( III) and (IV) When applying a sustained load of 30kN, all the beams point to the same performance and behavior. The maximum ultimate load was in the control beams by a load of 53kN. Nevertheless, the least ultimate load was by 47kN at 150 ¡C beam. This wa s 10% less as compared to the control beam. For different heating time 45, 60, 75 minutes for 150 ¡C beams showed similar responses shown in figures 4.3.2 (V), (VI), and (VII) When making a comparison between all the various applied temperatures under a sustained load, the association between the temperature and the ultimate load is an inverse relationship shown in figures 4.3.2 (VIII) It means that an increase in temperature leads to a reduction of the ultimate load. All the beams have the same failur e mode that causes the major CFRP sheet to be debonded. For all the beams, the major crack started from the point where force was applied and continued to the point of support for both sides.

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115 4.3.3 Failure mode After beams were exposed to sustained load f or specific time, beams were loaded until failure. The failure mode can be classified to primary and secondary. On four point bending test more than seven beams were tested. The unstrengthening beam was tested. The primary shear crack was starting from the left point of loading and keep going to the support. The second beam was also unstrengthening beam. While the beam was loaded the cracks start showing at mid span and they are increasing until the concrete crush at compressive zone with displacement reach 25 mm. For strengthening control beam, the failure was debending the warping sheet. This failure mode was repeating for the all strengthening beams. For three point bending test, there are more seven beams were tested. Most of these beams were failed the same way, which is the primary shear crack started from the point load and go directly to the support. However, this failure is different then the failure in four point bending test. The failure happened in two areas, which are crushing in compressive zone and in the edge of warping sheet with strengthen sheet. In table 4.3.3 1 and 2 shows the specific details of beams. 4.4 Thermal propagation at mid span of the RC beam Every strengthen beam was exposed to elevated temperatures. The CFRP surface was heat ed by the heating bed, and the thermocouple used to record. The applied heat was controlled from the heating bed while the thermocouple recorded the heat applied. In this case, it was hard to see the thermal propagation in the individual concrete specimen. As a result, the IR camera was applied for all the high temperatures to capture the thermal propagation in the beams. Every particular temperature was captured for 1800 seconds. Temperatures higher than the glass transition one indicated high thermal prop agation as compared to the temperatures near the glass transition temperature. It means that when

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116 the temperature increased, the thermal propagation experienced a significant increase. For example, temperatures near Tg such as 75 o C had a temperature at mi d span 27 o C. On the other hand, the temperatures higher than the Tg such as 100 o C, 125 o C, 150 o C, show high thermal propagation than the temperatures near than Tg. In addition, while applying 150 o C to concrete blocks, at 1200 sec the inducted temperatu re is equal to applying 75 o C for 1800 sec, by 27 o C. All thermal pictures ar e shown in figure 4.4.1 to 4.4.9 At middle of span, there are three points was pointed to measure the thermal propagation They are named by 1, 2, and 3. 1 is the nearest point f rom heating bed, and the distance is 41 mm. Also, the distance between each point is 41 mm. 4.5 summary and conclusion Nowadays the use of the CFRP bonded sheet has gained popularity due to its technique of flexural and sheer strengthening. The past resea rches have indentified that the performance of the CFRP sheet is highly affected by temperature and time This research is based on investigating whether temperate is a consideration in CFRP sheet performance and it is divided into two categories. The rese arch aims at investigating the performance of beams at different temperatures. In the first experiment, the relationship between fixed temperature and strain are investigated. In the second experiment involves changing the temperature with time and identif ying the effect on the beam. During the investigation process, the MTS machine was used. The results of the investigations were then analyzed as follows; on a four points bending test the relationship temperature is directly proportional to strain. An inc rease in temperature levels causes a subsequent increase in strain. Shear failure was also identified as the common failure mode for all CFRP beams. On three points bending, a

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117 change in temperature under a sustained load also has an inverse effect on the u ltimate load. Thus an increase in temperature results to ultimate load decrease and vice versa. Here, the failure mode was also similar in all beam loads and the effect is deboning of the CFRP sheet.

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118 Figure 4. 1a shows the first category (Four points bending) all unit by (cm) F igure 4 1 b shows the second category (three points bending) all unit by (cm) Figure 4 2 shows the beam reinforcement and section all unit by (cm) Heating Heating

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119 Figure 4.2.1a shows the preparation before start testi ng Figure 4.2.1b shows the preparation before start testing

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120 Figure 4.2.1c shows the preparation before start testing Figure 4.3 shows the setup MTS 20kips

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121 Table: 4.3.3 1 four point bending test beams Specimen No Py Pu Failure Mode 4B25 N 1 35 kN 48 kN S FC C 4B25 N 2 54 kN 70 kN FC C 4B25 U 1 60 kN 73 kN FC C D 4B100 U 1 55 kN 67 kN S FC D 4B125 U 1 71 kN 92 kN S FC D 4B150 U 1 67 kN 90 kN S C D Table: 4.3.3 2 three point ben ding test beams Specimen No Py Pu Failure Mode 3B25 U 40 kN 53 kN FC LD -C 3B75 U 45 kN 50.7 kN FC LD C 3B100 U 48 kN 50 kN FC LD C 3B125 U 40 kN 49 kN FC LD C 3B150 U 1 40 kN 47 kN FC LD C 3B150 U 2 36 kN 47.3 kN FC LD C 3B150 U 3 39 kN 48 kN F C LD C 3B150 U 4 38 kN 43 kN FC LD C Details of symbols: (D) Debonding, (LD) local debonding in the edge of warping sheet with CFRP strengthening sheet, (S) Shear, (C) Crushing, (FC) flexure crack

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122 (a) (b) (c) (d) (e) Figure 4.3.1 (I) show the response of unstrengthen beam (a) load displacement chart, (b) load time chart, (c) displacement time chart, (d) load with strain at tensile gauge, (e) failure mode.

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123 (a) (b) (c) (d) Figure 4.3. 1 (II) show the response of strengthen beam (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) failure mode. Debonding

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124 (a) (b) (c) (d) (e) Figure 4.3. 1 (III) show the response of strengthen beam at 75 o C (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 20 minutes

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125 (a) (b) (c) (d) (e) Figure 4.3. 1 (IV) show the response of strengthen beam at 100 o C (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 20 minutes

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126 (a) (b) (c) (d) (e) Figure 4.3. 1 (V) show the response of strengthen beam at 125 o C (a) load displ acement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 20 minutes

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127 (a) (b) (c) (d) (e) Figure 4.3. 1 (VI) show the response of strengthen beam at 150 o C (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 20 minutes

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128 Figure 4.3. 1 (VII) compares between different temperatures and strain

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129 (a) (b) (c) (d) (e) Figure 4.3. 2 (I) show the response of strengthen beam at 75 o C (a) load displacement chart, (b) load strain c hart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 30 minutes

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130 (a) (b) (c) (d) (e) Figure 4.3. 2 (II) show the response of strengthen beam at 100 o C (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 30 minutes

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131 (a) (b) (c) (d) (e) Fig ure 4.3. 2 (III) show the response of strengthen beam at 125 o C (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 30 minutes

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132 (a) (b) ( c) (d) (e) Figure 4.3. 2 (IV) show the response of strengthen beam at 150 o C (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 30 minutes

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133 (a) (b) (c) (d) (e) Figure 4.3. 2 (V) show the response of strengthen beam at 150 o C at 45 minutes (a) load displacement chart, (b) load strain chart, (c) load with strain at compres sion gauge, (d) load with strain at tensile gauge, (e) strain for 45 minutes

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134 (a) (b) (c) (d) (e) Figure 4.3. 2 (VI) show the response of strengthen beam at 150 o C at 60 minutes (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 60 minutes

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135 (a) (b) (c) (d) (e) Figure 4.3. 2 (VI I ) show the response of strengthen beam at 150 o C at 75 minutes (a) load displacement chart, (b) load strain chart, (c) load with strain at compression gauge, (d) load with strain at tensile gauge, (e) strain for 75 minutes

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136 (a) (b) (c) (d) (e ) (f) Figure 4.3. 2 (VII I ) compares between temperature and ultimate load (a) 25 o C to 75 o C, (b25 o C to 100 o C, (c) 25 o C to 125 o C, (d) 25 o C to 150 o C, (e) all temperatures, (f) Ultimate load to temperature

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137 (a) (b) (c) (d) (e) (f) (g) (h) (I)

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138 (j) (k) Figure 4.4.1 : thermal propagation for beam heated to 75 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 27; (k) 30 minutes.

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139 (a) (b) (c) (d) (e) (f) (g) (h) (I)

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140 (j) (k) Figure 4.4.2 : thermal propagation for beam heated to 100 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 27; (k) 30 minutes.

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141 (a) (b) (c) (d) (e) (f) (g) (h) (I)

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142 (j) (k) Figure 4.4.3 : thermal propagation for beam heated to 125 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 27; (k) 30 minutes.

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143 (a) (b) (c) (d) (e) (f) (g) (h) (I)

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144 (j) (k) Figure 4.4. 4 : thermal propagation for beam heated to 150 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 27; (k) 30 minutes.

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145 (a) (b) (c) (d) (e) (f) (g) (h) (i ) (j) Figure 4.4.5 : thermal propagation for beam heated to 75 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 30 minutes.

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146 (a) (b) (c) (d) (e) (f) (g) ( h) (i) (j) Figure 4.4.6 : thermal propagation for beam heated to 100 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 30 minutes.

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147 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Figure 4.4.7 : thermal propagation for beam heated to 125 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 30 minutes.

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148 (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Figure 4.4.8 : thermal propagation for beam heated to 150 ¡ C at: (a) 0; (b) 3; (c) 6; (d) 9; (e) 12; (f) 15 ; (g) 18; (h) 21; (i) 24; (j) 30 minutes.

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149 (a) (b) (c) (d) Figure 4.4.9 : thermal propagation for beam (a) 75 ¡ C (b) 100 ¡ C (c) 125 ¡ C (d) 150 ¡ C, for 30 minutes.

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150 5.1 Summary and Conclusion This thesis presented the thermomechanical load's performance upon exposure into a CFRP fortified concrete. To day, considerable popularity is attached to the utilization of CFRP sheet owing to its aptitude to overcome a myriad of problems. Chapter two of this paper provided a comprehensive literature review that integrated a collection of insights from new and old papers. In history, composites have been highly utilized particularly in civil engineering. Some of the earlier FRP applications date back to the early 1970s. Nonetheless, such composite applications were not reasonable. Over time, the FRP application tec hniques have been enhanced. Currently, the construction sector highly relies on FRP in making new structures in addition to rehabilitating and strengthening the preexisting structures. Rehabilitation is essential for deteriorating structures. Consequ ently, a large number of civil engineers use CFRP to deal with this issue. The main reasons they opt to use CFRP comprise of their lightweight, strength, installation ease, and their resistance to corrosion triggered electrochemically. All these factors ma ke the FRP effective for the engineering works. In spite of the many advantages of FRPs, they can easily be degraded significantly once they are subjected to high temperatures. In this effect, their use, particularly in most residential building, may becom e quite challenging. While fire vulnerability is not limited to CFRP only, research on other materials has been done, and the findings have been incorporated in diverse fire safety codes and building codes. The manner in which FRP materials acts under infe rno has not been thoroughly examined, and the manner in which such materials behave under extreme temperatures is not known.

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151 More than one hundred and forty four concrete blocks were examined in chapter three. All blocks were exposed to high temperatures of around 25 o C 175 o C. Two major categories of different CFRP sheet length and width were shown in this particular chapter. To capture the propagation of heat inside the strengthened concrete block, an IR camera was used. This section further illustrated a couple of conclusions. Applying higher temperatures in comparison to Tg negatively reflect the strengthened system's performance. The loss in some incidents reached 75 percent. Such a high percentage loss occurred following the epoxy's change to micro rubber condition from a solid state. Increasing the bonding area positively reflected on the system's performance. For instance, 0.25B indicated the highest loss at elevated temperatures. On the other hand, the 0.75B indicated the least loss for such expos ed temperatures. The IR camera indicated the gradual propagation for every two minutes. An increase in propagation correlated with an increase in temperature. Still in the same section, the aggregate shear stress was molded depending on the experimental ta sk. Chapter four dealt with whether temperature is a major consideration in the performance of CFRP. The chapter was split into two units. Here the aim of conducting the research was investigating the beams' performance under different temperatures. The relationship between strain and fixed temperature were investigated in the very first experiment. The second experiment entailed changing of temperatures relative to time and then observing the impact of the beam. In the course of the investigation, an MTS machine was employed. The findings of the research were analyzed on the 4 points bending test seeking to ascertain the relationship of temperature and strain being directly proportional. In this case, a temperature increase led to a subsequent strain incr ease.

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152 Shear failure was acknowledged to be one of the most common failure modes in all the CFRP beams. A shift in temperature under the sustained load had an inverse impact on the final load on the 3 point bending. Accordingly, a temperature increase led t o an ultimate decrease in load and vice versa. The failure mode here was similar in every beam load, and the impact was a deboned CFRP sheet.

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153 REFERENCE Abdul Rahman Namrou."An Experimental Investigation into the Behavior of Concrete E lements Rerofitted with NSM Composite Strips at Elevated Temperatures."University of Colorado Denver (2013). ACI Committee 216, & Fire Resistance and Fire Protection of Structures. (1982). Guide for determining the fire endurance of concrete elements. Detr oit, MI: American Concrete Institute. Barnes, R. A., & Mays, G. C. (1999). Fatigue performance of concrete beams strengthened with CFRP plates. Journal of Composites for Construction 3 (2), 63 72. Bakis, C. E., Ganjehlou, A., Kachlakev, D. I., Schupack, M., Balaguru, P. N., Gee, D. J., ... & Harik, I. E. (2002). Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures. Reported by ACI Committee 440 (2002). Benedikt, G. M., Goodall, B. L., & Society of P lastics Engineers. (1998). Metallocene catalyzed polymers: Materials, properties, processing & markets. Norwich, NY: Plastics Design Library. Blaschko, M. 2003. Bond behavior of CFRP strips glued into slits, Proceedings of Fiber Reinforced Polymer Reinfor cement for Concrete Structures (FRPRCS 6), 205 214. Binetruy, C., Chinesta, F., &Keunings, R. (2015).Flows in polymers, reinforced polymers and composites: A multi scale approach. Chen, J. F., & Teng, J. G. (2003). Shear capacity of FRP strengthened RC beams: FRP debonding. Construction and Building Materials 17 (1), 27 41. Carolin, A. (2003). Carbon fibre reinforced polymers for strengthening of structural elements. Division of Structural Engineering, Department of Civil and Mining Engineering, Lulea U niversity of Technology, Sweden 194. Chen, J. F., &Teng, J. G. (2001). Anchorage strength models for FRP and steel plates bonded to concrete. Journal of Structural Engineering, 127(7), 784 791. De Lorenzis, L., Nanni, A., and La Tegola, A. 2000. Strengt hening of reinforced concrete structures with near surface mounted FRP rods, bibl. International Meeting on Composite Masterials, PLAST 2000, Milan, Italy, May 9 11, p 8.

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154 Erki, M. A., & Rizkalla, S. H. (1993). FRP reinforcement for concrete structures. CO NCRETE INTERNATIONAL DETROIT 15 48 48. Galbreath, M. (1966). Fire endurance of concrete assemblies: (a compilation of published information on fire endurance of a variety of concrete walls, floors, roofs, columns and beams). Ottawa. Hassan, T., &Rizka lla, S. (2002). Flexural strengthening of prestressed bridge slabs with FRP systems. PCI journal 47 (1), 76 93. Horie, C. V. (1987). Materials for conservation: Organic consolidants, adhesives, and coatings. London: Butterworths. Kim, J. K, & Mai, Y. W. (1998). Engineered interfaces in fiber reinforced composites. Amsterdam: Elsevier Sciences. Kodur, V. K. R., Bisby, L. A., & Green, M. F. (2007). Preliminary guidance for the design of FRP strengthened concrete members exposed to fire. Journal of Fire Pro tection Engineering 17 (1), 5 26. Lee, L. S., & Jain, R. (2009). The role of FRP composites in a sustainable world. Clean Technologies and Environmental Policy 11 (3), 247 249. Li, G., &Shchukin, V. Y. (2012). Advances in engineering design and optimiza tion III: Selected, peer reviewed papers from the third international conference on engineering design and optimization (ICEDO 2012), May 25 27, 2012, Shaoxing, P.R. China. MacKenzie, S. J., Mulkern, T. J., Beck, T. N., & U.S. Army Research Laboratory.(2 001). Material properties of bi modal epoxy networks. Aberdeen Proving Ground, MD: Army Research Laboratory. Matsumoto, S., & Iwate, U. (2013).Materials science researcher biographical sketches and research summaries. New York: Nova Science Publishers. M acKenzie, S. J., Mulkern, T. J., Beck, T. N., & U.S. Army Research Laboratory.(2001). Material properties of bi modal epoxy networks. Aberdeen Proving Ground, MD: Army Research Laboratory. Mostofinejad, D., & Shameli, S. M. (2013). Externally bonded reinf orcement in grooves (EBRIG) technique to postpone debonding of FRP sheets in strengthened concrete beams. Construction and Building Materials 38 751 758. Song, B., Casem, D., & Kimberley, J. (2015). Dynamic Behavior of Materials, Volume 1: Proceedings o f the 2014 Annual Conference on Experimental and Applied Mechanics. Cham: Springer.

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155 Sena Cruz, J. M., Barros, J. A., Coelho, M. R., & Silva, L. F. (2012). Efficiency of different techniques in flexural strengthening of RC beams under monotonic and fatigue loading. Construction and Building Materials 29 175 182. Tan, K. Y. (2003). Evaluation of externally bonded CFRP systems for the strengthening of RC slabs Thushara Siriwardanage "Mechanochemical Investigation Into Bond Performance Of An NSM CFRP Stren gthening System At Elevated Temperatures." University of Colorado Denver (2014). Wuertz, A. F. (2013). Strengthening rectangular beams with NSM steel bars and externally bonded GFRP. Manhattan, Kan: Kansas State University. Yourdkhani, M. (2014).Aspects of nanoparticles dispersion and interaction in polymer nanocomposites.

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156 Appendix A 0.25 B (( 1" width )) 25 0 C : Time (sec) 25 ¡C1 (kN) 25 ¡C2 (kN) 25 ¡C3 (kN) A verage (kN) Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.133 1.151 1.121 1.135 0.015 0.013 200 1.059 1.062 1.051 1.057 0.006 0.005 300 1.038 1.013 1.047 1.033 0.018 0.017 400 1.026 0.985 1.044 1.018 0.030 0.030 500 1.022 0.963 1.041 1.008 0.041 0.040 600 1.009 0.946 1.039 0.998 0.047 0.047 700 1. 002 0.931 1.039 0.991 0.055 0.055 800 0.994 0.921 1.038 0.984 0.059 0.060 900 0.986 0.912 1.035 0.978 0.062 0.063 1000 0.981 0.903 1.034 0.973 0.066 0.068 1100 0.977 0.898 1.034 0.970 0.068 0.070 1200 0.974 0.892 1.028 0.965 0.069 0.071 ** The peak v alue 100 # 10 which equal =1.18 kN @ 107.2, 103.3, 108.1 sec $ 50 0 C : T ime (Sec) 50 ¡C1 (kN) 50 ¡C2 (kN) 50 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 70 ** A:AG; # A:A=A 1.144 A:AHH # B:BAH B:BA;F 100 1.112 1.061 1.121 1.098 0.032 0.029 200 1.004 0.904 1.032 0.980 0.067 0.069 300 0.977 0.788 0.983 0.916 0.111 0.121 400 0.955 0.791 0.958 0.901 0.096 0.106 500 0.947 0.768 0.934 0.883 0.100 0.113 600 0.940 0.754 0.915 0.869 0.101 0.116 700 0.946 0.754 0.900 0.867 0.1 00 0.116 800 0.919 0.725 0.890 0.845 0.104 0.124 900 0.819 0.709 0.884 0.804 0.089 0.110 1000 0.864 0.686 0.874 0.808 0.106 0.131 1100 0.857 0.676 0.868 0.800 0.108 0.135 1200 0.859 0.663 0.860 0.794 0.113 0.143 ** The peak value 70 # 10 sec which e qual =1.18 kN @ 70.3 71.1, 71.8 sec

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157 $ 75 0 C : Time (Sec) 75 ¡C 1 (kN) 75 ¡C2 (kN) 75 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 70 ** A:AG< A:AGB 1.172 A:A=F B:BB<; B:BBE< 100 1.040 1.041 1.014 1.032 0.015 0.015 20 0 0.920 1.004 0.916 0.947 0.050 0.052 300 0.893 0.977 0.861 0.910 0.060 0.066 400 0.878 0.955 0.820 0.884 0.068 0.076 500 0.866 0.934 0.818 0.873 0.058 0.067 600 0.855 0.853 0.810 0.840 0.025 0.030 700 0.841 0.852 0.695 0.796 0.088 0.110 800 0.825 0. 828 0.701 0.785 0.073 0.092 900 0.801 0.807 0.702 0.770 0.059 0.076 1000 0.781 0.774 0.698 0.751 0.046 0.061 1100 0.771 0.772 0.699 0.748 0.042 0.056 1200 0.758 0.766 0.704 0.743 0.034 0.045 ** The peak value 70 # 10 sec, which equal =1.185 kN @ 71.2, 7 0.9, 71.4 sec $ 100 0 C : T ime (Sec ) 100 ¡C1 (kN) 100 ¡C2 (kN) 100 ¡C3 (kN) A verage Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 70 ** A:AGD A:AHF A:A== A:A=H B:BB<; B:BBE< 100 1.014 1.014 1.039 1.022 0.014 0.014 200 0.856 0.888 0.899 0 .881 0.022 0.026 300 0.784 0.834 0.737 0.785 0.048 0.062 400 0.728 0.821 0.639 0.729 0.091 0.125 500 0.690 0.790 0.614 0.698 0.088 0.126 600 0.666 0.792 0.587 0.682 0.104 0.152 700 0.633 0.734 0.586 0.651 0.075 0.116 800 0.616 0.667 0.572 0.618 0.047 0.077 900 0.616 0.676 0.573 0.622 0.052 0.083 1000 0.604 0.644 0.563 0.604 0.040 0.067 1100 0.599 0.658 0.556 0.604 0.051 0.084 1200 0.594 0.600 0.539 0.578 0.033 0.058 ** The peak value 70 # 10 sec, which equal =1.182 kN @ 71.5, 72.3, 73.1 sec

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158 12 5 ¡C : Time (Sec) 125 ¡C 1 (kN) 125 ¡C2 (kN) 125 ¡C 3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 70 ** A:AGG A:A=G A:AGA A:AGD; B:BBEA B:BB;< 100 1.056 1.061 0.950 1.022 0.063 0.061 200 0.711 0.867 0.734 0.771 0.084 0.109 300 0.624 0.822 0.667 0.704 0.104 0.148 400 0.573 0.826 0.579 0.659 0.145 0.219 500 0.552 0.758 0.510 0.607 0.133 0.219 600 0.537 0.701 0.526 0.588 0.098 0.166 700 0.533 0.761 0.529 0.608 0.133 0.218 800 0.526 0.684 0.517 0.576 0.094 0.163 900 0.51 7 0.695 0.503 0.572 0.107 0.187 1000 0.508 0.642 0.509 0.553 0.077 0.139 1100 0.489 0.688 0.503 0.560 0.111 0.198 1200 0.491 0.634 0.477 0.534 0.087 0.163 ** The peak value 70 # 10 sec, which equal =1.188 kN @ 70.7, 71.4, 70.6 sec $ 150 ¡C : Time (Sec ) 150 ¡C1 (kN) 150 ¡C2 (kN) 150 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 70 ** A:AGB A:A
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159 $ 1 75 ¡C : Time (Sec) 175 ¡C1 (kN) 17 5 ¡C2 (kN) 175 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 70 ** A:AGD A:A=A A:AG< A:A=F B:BBH B:BB< 100 0.813 0.952 0.998 0.921 0.096 0.105 200 0.522 0.674 0.700 0.632 0.097 0.153 300 0.327 0.552 0.593 0.491 0.143 0. 292 400 0.340 0.478 0.548 0.455 0.106 0.233 500 0.303 0.405 0.510 0.406 0.104 0.255 600 0.289 0.366 0.459 0.371 0.085 0.229 700 0.287 0.301 0.396 0.328 0.059 0.180 800 0.254 0.246 0.372 0.291 0.071 0.243 900 0.239 0.241 0.389 0.290 0.086 0.297 1000 0.234 0.218 0.333 0.262 0.062 0.238 1100 0.243 0.210 0.297 0.250 0.044 0.175 1200 0.216 0.216 0.329 0.254 0.065 0.256 ** The peak value 70 # 10 sec, which equal =1.185 kN @ 71.3, 72.4, 70.4 sec

PAGE 176

160 0.5 B (( 2" width )) $ 25 ¡C : Time (Sec ) 25 ¡C1 (kN) 25 ¡C2 (kN) 25 ¡C 3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.658 1.658 1.530 1.615 0.074 0.046 200 1.685 1.689 1.633 1.669 0.031 0.019 300 1.647 1.685 1.601 1.644 0.042 0.026 400 1.622 1.665 1. 597 1.628 0.034 0.021 500 1.602 1.663 1.619 1.628 0.032 0.019 600 1.583 1.635 1.571 1.596 0.034 0.021 700 1.573 1.632 1.587 1.597 0.031 0.019 800 1.556 1.635 1.562 1.584 0.044 0.028 900 1.527 1.610 1.562 1.566 0.042 0.027 1000 1.504 1.633 1.584 1.574 0.065 0.041 1100 1.494 1.614 1.550 1.552 0.060 0.039 1200 1.495 1.628 1.544 1.556 0.068 0.043 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 106.7, 105.9, 107.2 sec $ 50 ¡C : Time (Sec) 50 ¡C1 (kN) 50 ¡C2 (kN) 50 ¡C3 (kN) Average Standard D eviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.658 1.658 1.598 1.638 0.034 0.021 200 1.640 1.640 1.593 1.624 0.027 0.017 300 1.575 1.572 1.564 1.570 0.006 0.004 400 1.534 1.525 1.512 1.524 0.011 0.008 500 1.502 1.485 1.467 1.485 0.017 0.0 12 600 1.463 1.440 1.416 1.440 0.023 0.016 700 1.436 1.406 1.377 1.406 0.029 0.021 800 1.415 1.377 1.344 1.379 0.035 0.026 900 1.387 1.343 1.273 1.334 0.057 0.043 1000 1.374 1.322 1.372 1.356 0.029 0.022 1100 1.354 1.296 1.250 1.300 0.052 0.040 1200 1.336 1.271 1.137 1.248 0.102 0.081 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 105.4, 106.1, 107.3 sec

PAGE 177

161 $ 75 ¡C : Time (Sec) 75 ¡C 1 (kN) 75 ¡C2 (kN) 75 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.65 8 1.658 1.598 1.638 0.035 0.021 200 1.615 1.640 1.503 1.586 0.073 0.046 300 1.550 1.575 1.478 1.534 0.050 0.033 400 1.477 1.534 1.430 1.480 0.052 0.035 500 1.407 1.502 1.389 1.433 0.060 0.042 600 1.358 1.463 1.343 1.388 0.066 0.047 700 1.308 1.436 1. 308 1.351 0.074 0.055 800 1.271 1.415 1.278 1.321 0.081 0.061 900 1.217 1.387 1.183 1.262 0.109 0.087 1000 1.210 1.374 1.053 1.212 0.161 0.132 1100 1.159 1.354 1.068 1.194 0.146 0.122 1200 1.154 1.336 0.986 1.159 0.175 0.151 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 106.0, 106.5, 107.4 sec $ 100 ¡C : Time (Sec) 100 ¡C1 (kN) 100 ¡C2 (kN) 100 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.661 1.661 1.598 1.640 0.036 0.022 200 1.440 1.366 1.503 1 .436 0.068 0.048 300 1.221 1.177 1.478 1.292 0.162 0.126 400 1.162 1.148 1.430 1.246 0.159 0.128 500 1.135 1.135 1.250 1.173 0.066 0.057 600 1.106 1.103 1.225 1.145 0.070 0.061 700 1.087 1.043 1.219 1.116 0.092 0.082 800 1.066 0.982 1.213 1.087 0.116 0.107 900 1.056 0.933 1.183 1.058 0.125 0.118 1000 1.016 0.853 1.053 0.974 0.106 0.109 1100 1.012 0.809 1.029 0.950 0.122 0.129 1200 1.004 0.761 1.039 0.935 0.152 0.162 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 105.7 106.5, 105,9 sec

PAGE 178

162 $ 125 ¡C : Time (Sec) 125 ¡C1 (kN) 125 ¡C2 (kN) 125 ¡C2 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.663 1.676 1.653 1.664 0.011 0.007 200 1.409 1.366 1.240 1.338 0.088 0.066 300 1.143 1.279 1.120 1.181 0.086 0 .073 400 1.089 1.228 1.105 1.141 0.076 0.067 500 1.072 1.207 1.083 1.121 0.075 0.067 600 1.053 1.193 1.088 1.111 0.073 0.065 700 1.038 1.188 1.080 1.102 0.077 0.070 800 1.024 1.181 1.075 1.093 0.080 0.074 900 1.016 1.172 1.054 1.081 0.082 0.076 1000 0.999 1.163 1.059 1.074 0.083 0.077 1100 0.991 1.145 1.049 1.061 0.078 0.073 1200 0.981 1.146 1.016 1.047 0.087 0.083 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 105.4, 105.1, 105.7 sec $ 150 ¡C : Time (Sec) 150 ¡C1 (kN) 150 ¡C2 (kN) 150 ¡ C3 (kN) Average (kN) Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.665 1.772 1.731 1.723 0.054 0.031 200 1.451 1.560 1.361 1.457 0.100 0.068 300 1.281 1.318 1.174 1.258 0.075 0.059 400 1.221 1.139 1.049 1.136 0.086 0.076 500 1. 089 1.035 0.931 1.018 0.080 0.079 600 1.018 0.927 0.799 0.915 0.110 0.120 700 0.836 0.847 0.657 0.780 0.107 0.137 800 0.794 0.753 0.553 0.700 0.129 0.184 900 0.732 0.674 0.490 0.632 0.126 0.200 1000 0.666 0.584 0.353 0.534 0.162 0.303 1100 0.631 0.55 6 0.297 0.495 0.175 0.355 1200 0.623 0.539 0.329 0.497 0.151 0.305 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 101.4, 100.3,100.7 sec

PAGE 179

163 $ 175 ¡C : Time (Sec) 175 ¡C1 (kN) 175 ¡C2 (kN) 175 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0.0 00 0.000 0.000 0.000 0.000 0.000 100 ** 1.665 1.772 1.692 1.710 0.055 0.032 200 1.454 1.560 1.355 1.456 0.102 0.070 300 1.130 1.318 1.091 1.180 0.121 0.103 400 1.010 1.139 1.033 1.061 0.069 0.065 500 0.919 1.035 0.926 0.960 0.065 0.068 600 0.820 0.927 0.842 0.863 0.057 0.066 700 0.704 0.847 0.771 0.774 0.072 0.093 800 0.649 0.753 0.668 0.690 0.055 0.080 900 0.628 0.686 0.582 0.632 0.052 0.082 1000 0.567 0.655 0.508 0.577 0.074 0.129 1100 0.551 0.688 0.447 0.562 0.121 0.215 1200 0.516 0.731 0.350 0.532 0.191 0.359 ** The peak value 100 # 10 sec, which equal =1.77 kN @ 107.0, 104.2, 105.6 sec

PAGE 180

164 0.75 B (( 3" width )) 25 ¡C : T ime (Sec) 25 ¡C1 (kN) 25 ¡C2 (kN) 25 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0.000 0.000 0.00 0 0.000 0.000 0.000 100 1.622 1.651 1.651 1.642 0.017 0.010 140 ** D:D
PAGE 181

165 $ 75 ¡C : Time (Sec) 75 ¡C1 (kN) 75 ¡C2 (kN) 75 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 1.642 1.658 1.662 1.654 0.011 0.006 140 ** D:DEE D:D

PAGE 182

166 $ 125 ¡C : Time (Sec) 125 ¡C1 (kN) 125 ¡C2 (kN) 125 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 1.658 1.658 1.671 1.662 0.007 0.004 140 ** D:D<< D:AFB D:DEF D:D;A B:BDF B:BA; 200 1.944 2.000 1.974 1.973 0.028 0.014 300 1.781 1.864 1.827 1.824 0.042 0.023 400 1.641 1.790 1.694 1.708 0.075 0.044 500 1.654 1.688 1.638 1.660 0.026 0.015 600 1.625 1.693 1.564 1.627 0.064 0.039 700 1. 575 1.627 1.546 1.582 0.041 0.026 800 1.533 1.664 1.497 1.565 0.088 0.056 900 1.467 1.709 1.496 1.557 0.132 0.085 1000 1.480 1.723 1.470 1.558 0.143 0.092 1100 1.397 1.746 1.465 1.536 0.185 0.120 1200 1.404 1.796 1.473 1.558 0.209 0.134 ** The peak v alue 140 # 10 sec, which equal =2.25 kN @ 140.3, 138.6, 142.4 sec $ 150 ¡C : Time (Sec) 150 ¡C1 (kN) 150 ¡C2 (kN) 150 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 1.653 1.658 1.680 1.664 0.014 0.009 140 ** D:DE< D:DAB D:D;F D:D;A B:BA< B:BB= 200 2.026 1.944 1.920 1.963 0.056 0.028 300 1.744 1.765 1.699 1.736 0.034 0.019 400 1.511 1.595 1.673 1.593 0.081 0.051 500 1.419 1.578 1.490 1.496 0.080 0.053 600 1.318 1.519 1.358 1.398 0.106 0.076 700 1.276 1.439 1.08 5 1.267 0.177 0.140 800 1.254 1.367 0.970 1.197 0.205 0.171 900 1.159 1.271 0.973 1.134 0.151 0.133 1000 1.182 1.254 0.970 1.135 0.148 0.130 1100 1.148 1.141 0.959 1.083 0.107 0.099 1200 1.121 1.119 0.960 1.067 0.092 0.087 ** The peak value 140 # 10 se c, which equal =2.25 kN @ 143.3, 135.6, 137.7sec

PAGE 183

167 $ 175 ¡C : Time (Sec) 175 ¡C1 (kN) 175 ¡C2 (kN) 175 ¡C3 (kN) Average Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 1.671 1.663 1.665 1.666 0.004 0.002 140 ** D:D

PAGE 184

168 Effect length ( L= 3.6" B= 2") $ 25 ¡C : Time (Sec) 25 ¡C1 (kN) 25 ¡C2 (kN) 25 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0.000 0.000 0.000 0.000 0.000 0.000 100 ** 1.661 1.658 1.616 1.645 0.025 0.015 200 1.695 1.685 1.633 1.671 0.033 0.020 300 1.704 1.647 1.617 1.656 0.044 0.027 400 1.535 1.622 1.584 1.580 0.043 0.028 500 1.611 1.602 1.575 1.596 0.019 0.012 600 1.625 1.583 1.566 1.592 0.030 0.019 700 1.618 1.573 1.552 1.581 0.034 0.02 1 800 1.633 1.556 1.553 1.581 0.046 0.029 900 1.650 1.527 1.545 1.574 0.067 0.042 1000 1.653 1.504 1.506 1.554 0.086 0.055 1100 1.649 1.494 1.465 1.536 0.099 0.065 1200 1.613 1.495 1.456 1.521 0.082 0.054 ** The peak value 100 # 10 sec, which equal =1. 710kN @ 103.9, 104.1, 104.5 sec $ 50 ¡C : Time (Sec) 50 ¡C 1 (kN) 50 ¡C2 (kN) 50 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.659 1.691 1.648 1.666 0.022 0.013 200 1.592 1.602 1.572 1.589 0.015 0.009 300 1.564 1.553 1.543 1.553 0.010 0.007 400 1.538 1.528 1.518 1.528 0.010 0.007 500 1.549 1.504 1.497 1.517 0.028 0.018 600 1.575 1.485 1.489 1.516 0.051 0.033 700 1.509 1.470 1.469 1.483 0.023 0.015 800 1.423 1.460 1.453 1.446 0.020 0.014 900 1.465 1.454 1.436 1.452 0.015 0.01 0 1000 1.492 1.444 1.411 1.449 0.041 0.028 1100 1.475 1.438 1.402 1.438 0.037 0.025 1200 1.476 1.430 1.402 1.436 0.037 0.026 The peak value 100 # 10 sec, which equal =1.710kN @ 102.2, 103.1, 104.4 sec

PAGE 185

169 $ 75 ¡C : Time (Sec) 75 ¡C1 (kN) 75 ¡C2 (kN) 75 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.652 1.717 1.665 1.678 0.035 0.021 200 1.589 1.368 1.471 1.476 0.111 0.075 300 1.573 1.319 1.358 1.417 0.136 0.096 400 1.407 1.285 1.360 1.351 0.061 0.045 500 1.369 1.257 1.337 1.321 0.058 0.044 600 1.339 1.237 1.328 1.302 0.056 0.043 700 1.301 1.230 1.324 1.285 0.049 0.038 800 1.286 1.223 1.283 1.264 0.036 0.028 900 1.260 1.219 1.277 1.252 0.030 0.024 1000 1.236 1.209 1.247 1.230 0.019 0.016 1100 1.251 1.205 1.241 1.232 0.024 0. 020 1200 1.215 1.203 1.224 1.214 0.010 0.008 ** The peak value 100 # 10 sec, which equal =1.710kN @ 101.2, 100.7, 101.4 sec $ 100 ¡C : Time (Sec) 100 ¡C1 (kN) 100 ¡C2 (kN) 100 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.675 1.653 1.564 1.630 0.059 0.036 200 1.446 1.458 1.386 1.430 0.038 0.027 300 1.343 1.413 1.333 1.363 0.043 0.032 400 1.269 1.417 1.297 1.328 0.079 0.060 500 1.223 1.349 1.268 1.280 0.064 0.050 600 1.192 1.292 1.248 1.244 0.050 0.040 700 1.160 1.352 1.242 1.2 51 0.096 0.077 800 1.130 1.275 1.233 1.213 0.074 0.061 900 1.116 1.286 1.230 1.211 0.086 0.071 1000 1.114 1.233 1.223 1.190 0.066 0.056 1100 1.101 1.279 1.216 1.199 0.090 0.075 1200 1.077 1.225 1.215 1.173 0.083 0.071 ** The peak value 100 # 10 sec, wh ich equal =1.710kN @ 103.3, 104.1, 105.2 sec

PAGE 186

170 $ 125 ¡C : Time (Sec) 125 ¡C1 (kN) 125 ¡C2 (kN) 125 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.665 1.476 1.595 1.579 0.095 0.060 200 1.194 1.302 1.306 1.267 0.064 0.050 300 1.1 82 1.215 1.198 1.198 0.016 0.014 400 1.170 1.164 1.151 1.162 0.010 0.008 500 1.084 1.143 1.107 1.111 0.030 0.027 600 1.022 1.110 1.053 1.062 0.045 0.042 700 1.054 1.076 0.999 1.043 0.039 0.038 800 0.944 1.039 0.976 0.986 0.049 0.049 900 0.920 1.000 0 .992 0.971 0.044 0.046 1000 0.918 0.961 0.941 0.940 0.021 0.023 1100 0.880 0.912 0.903 0.898 0.016 0.018 1200 0.782 0.883 0.934 0.866 0.078 0.090 ** The peak value 100 # 10 sec, which equal =1.710kN @ 102.3, 106.1, 104.22sec $ 150 ¡C : Time (Sec) 150 ¡ C1 (kN) 150 ¡C2 (kN) 150 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.689 1.476 1.595 1.587 0.106 0.067 200 1.223 1.302 1.306 1.277 0.047 0.036 300 0.985 0.993 1.198 1.058 0.121 0.114 400 0.928 0.782 1.144 0.951 0.182 0.191 500 0.832 0.777 0.790 0.799 0.029 0.036 600 0.750 0.779 0.658 0.729 0.063 0.086 700 0.653 0.780 0.633 0.689 0.080 0.116 800 0.657 0.772 0.612 0.681 0.083 0.121 900 0.637 0.782 0.608 0.676 0.094 0.139 1000 0.625 0.783 0.606 0.671 0.097 0.144 1100 0.640 0. 778 0.600 0.673 0.093 0.139 1200 0.630 0.763 0.595 0.663 0.089 0.134 ** The peak value 100 # 10 sec, which equal =1.710kN @ 101.9, 105.2, 106.1 sec

PAGE 187

171 $ 175 ¡C : Time (Sec) 175 ¡C1 (kN) 175 ¡C2 (kN) 175 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.659 1.600 1.746 1.669 0.073 0.044 200 1.379 1.302 1.072 1.251 0.159 0.127 300 1.287 1.195 0.597 1.026 0.374 0.365 400 1.168 1.144 0.231 0.847 0.534 0.631 500 0.715 0.796 0.245 0.586 0.298 0.508 600 0.524 0.657 0.214 0.465 0.227 0. 489 700 0.475 0.629 0.238 0.447 0.197 0.440 800 0.424 0.612 0.233 0.423 0.190 0.448 900 0.417 0.613 0.238 0.423 0.187 0.443 1000 0.414 0.611 0.253 0.426 0.179 0.420 1100 0.401 0.595 0.223 0.406 0.186 0.459 1200 0.411 0.595 0.268 0.425 0.164 0.387 ** The peak value 100 # 10 sec, which equal =1.710kN @ 102.5, 103.3,100.1 sec

PAGE 188

172 1.25 Effect length (L= 4.5" B= 2") $ 25 ¡C : Time (sec) 25 ¡C1 (kN) 25 ¡C2 (kN) 25 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.658 1.735 1.725 1.706 0.042 0.025 200 1.689 1.660 1.634 1.661 0.028 0.017 300 1.685 1.640 1.585 1.636 0.050 0.031 400 1.665 1.627 1.558 1.616 0.054 0.033 500 1.663 1.623 1.535 1.607 0.066 0.041 600 1.635 1.610 1.518 1.588 0.062 0.039 700 1.632 1 .603 1.499 1.578 0.070 0.044 800 1.635 1.595 1.491 1.574 0.074 0.047 900 1.610 1.587 1.485 1.561 0.067 0.043 1000 1.633 1.582 1.473 1.563 0.082 0.052 1100 1.614 1.578 1.468 1.553 0.076 0.049 1200 1.628 1.575 1.462 1.555 0.085 0.055 ** The peak value 100 # 10 sec, which equal =1.770kN @ 106.9, 104.1, 105.7sec $ 50 ¡C : Time (sec) 50 ¡C1 (kN) 50 ¡C2 (kN) 50 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.654 1.687 1.677 1.673 0.017 0.010 200 1.666 1.598 1.406 1.557 0.134 0.086 30 0 1.651 1.575 1.353 1.527 0.155 0.101 400 1.581 1.543 1.317 1.480 0.142 0.096 500 1.547 1.533 1.288 1.456 0.146 0.100 600 1.457 1.525 1.268 1.416 0.133 0.094 700 1.494 1.504 1.262 1.420 0.137 0.096 800 1.501 1.499 1.253 1.417 0.142 0.100 900 1.447 1. 470 1.250 1.389 0.121 0.087 1000 1.480 1.446 1.243 1.389 0.128 0.092 1100 1.479 1.432 1.236 1.383 0.129 0.093 1200 1.481 1.426 1.235 1.381 0.129 0.093 ** The peak value 100 # 10 sec, which equal =1.770kN @ 108.9, 107.5, 107.9 sec

PAGE 189

173 $ 75 ¡C : Time (sec ) 75 ¡C1 (kN) 75 ¡C2 (kN) 75 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.636 1.663 1.677 1.659 0.021 0.013 200 1.636 1.505 1.406 1.516 0.115 0.076 300 1.570 1.389 1.353 1.437 0.116 0.081 400 1.519 1.392 1.317 1.409 0.102 0.072 500 1.448 1.370 1.288 1.368 0.080 0.059 600 1.409 1.355 1.268 1.344 0.071 0.053 700 1.441 1.355 1.262 1.353 0.090 0.066 800 1.343 1.326 1.253 1.308 0.048 0.037 900 1.353 1.310 1.250 1.304 0.052 0.040 1000 1.385 1.287 1.243 1.305 0.073 0.056 1100 1. 357 1.277 1.236 1.290 0.061 0.048 1200 1.364 1.265 1.235 1.288 0.068 0.052 ** The peak value 100 # 10 sec, which equal =1.770kN @ 105.9, 107.2, 105.1sec $ 100 ¡C : Time (sec) 100 ¡C1 (kN) 100 ¡C2 (kN) 100 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.712 1.713 1.712 1.712 0.001 0.000 200 1.488 1.605 1.458 1.517 0.078 0.051 300 1.397 1.578 1.385 1.453 0.108 0.074 400 1.401 1.556 1.328 1.428 0.116 0.081 500 1.356 1.535 1.290 1.394 0.127 0.091 600 1.313 1.454 1.248 1.338 0.106 0 .079 700 1.262 1.454 1.187 1.301 0.138 0.106 800 1.212 1.430 1.151 1.264 0.146 0.116 900 1.215 1.408 1.115 1.246 0.149 0.120 1000 1.211 1.375 1.092 1.226 0.142 0.116 1100 1.213 1.373 1.086 1.224 0.144 0.117 1200 1.195 1.367 1.094 1.219 0.138 0.113 The peak value 100 # 10 sec, which equal =1.770kN @ 107.3, 107.0, 106.6 sec

PAGE 190

174 $ 125 ¡C : Time (sec) 125 ¡C1 (kN) 125 ¡C2 (kN) 125 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.655 1.697 1.696 1.683 0.024 0.014 200 1.613 1.521 1.311 1.482 0.155 0.104 300 1.319 1.444 1.219 1.327 0.112 0.085 400 1.101 1.430 1.172 1.234 0.173 0.140 500 1.113 1.406 1.152 1.223 0.159 0.130 600 1.109 1.366 1.136 1.204 0.141 0.118 700 1.071 1.351 1.128 1.184 0.148 0.125 800 1.076 1.267 1.129 1.15 7 0.099 0.085 900 1.092 1.259 1.118 1.156 0.090 0.078 1000 1.099 1.202 1.119 1.140 0.054 0.048 1100 1.084 1.188 1.105 1.126 0.055 0.049 1200 1.069 1.201 1.090 1.120 0.071 0.063 ** The peak value 100 # 10 sec, which equal =1.770kN @ 105.4, 104.1, 104.3 s ec $ 150 ¡C : Time (sec) 150 ¡C1 (kN) 150 ¡C2 (kN) 150 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.686 1.686 1.594 1.655 0.053 0.032 200 1.406 1.186 1.305 1.299 0.110 0.085 300 1.258 1.031 1.048 1.112 0.127 0.114 400 0.988 0 .976 0.831 0.932 0.087 0.094 500 0.772 0.913 0.691 0.792 0.113 0.142 600 0.769 0.878 0.676 0.774 0.101 0.131 700 0.613 0.831 0.685 0.709 0.111 0.157 800 0.645 0.784 0.694 0.708 0.070 0.099 900 0.607 0.783 0.659 0.683 0.090 0.132 1000 0.608 0.766 0.65 3 0.676 0.081 0.121 1100 0.632 0.773 0.639 0.681 0.080 0.117 1200 0.606 0.796 0.682 0.695 0.095 0.137 ** The peak value 100 # 10 sec, which equal =1.770kN @ 106.2, 106.5, 108.1 sec

PAGE 191

175 $ 175 ¡C : Time (sec) 175 ¡C1 (kN) 175 ¡C2 (kN) 175 ¡C3 (kN) Avera ge (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.664 1.486 1.642 1.598 0.097 0.061 200 1.123 1.153 0.927 1.068 0.123 0.115 300 0.694 0.895 0.550 0.713 0.173 0.243 400 0.602 0.675 0.353 0.543 0.169 0.311 500 0.406 0.492 0.293 0.397 0.100 0.251 60 0 0.399 0.494 0.260 0.385 0.118 0.306 700 0.380 0.483 0.235 0.366 0.125 0.341 800 0.425 0.491 0.234 0.383 0.133 0.347 900 0.416 0.492 0.225 0.377 0.138 0.365 1000 0.426 0.491 0.288 0.402 0.104 0.258 1100 0.417 0.496 0.248 0.387 0.127 0.328 1200 0.407 0.492 0.256 0.385 0.120 0.312 ** The peak value 100 # 10 sec, which equal =1.770kN @ 102.2, 106.1, 103.5 sec

PAGE 192

176 1.5 Effect length ( L= 5.4" B= 2") $ 25 ¡C : Time (sec) 25 ¡C1 (kN) 25 ¡C2 (kN) 25 ¡C3 (kN) Average (kN) Standard D eviation COV 0 0 0 0 0 0 0 100 ** 1.663 1.658 1.725 1.682 0.037 0.022 200 1.657 1.685 1.634 1.659 0.026 0.015 300 1.708 1.665 1.585 1.653 0.063 0.038 400 1.687 1.660 1.558 1.635 0.068 0.042 500 1.621 1.660 1.535 1.605 0.064 0.040 600 1.654 1.662 1.51 8 1.611 0.081 0.050 700 1.569 1.672 1.499 1.580 0.087 0.055 800 1.586 1.674 1.491 1.584 0.092 0.058 900 1.565 1.666 1.485 1.572 0.091 0.058 1000 1.622 1.663 1.473 1.586 0.100 0.063 1100 1.605 1.673 1.468 1.582 0.104 0.066 1200 1.543 1.694 1.462 1.566 0.118 0.075 ** The peak value 100 # 10 sec, which equal =1.80 kN @ 108.2, 108.5, 109.1 sec $ 50 ¡C : Time (sec) 50 ¡C1 (kN) 50 ¡C2 (kN) 50 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.294 1.314 1.256 1.288 0.029 0.023 200 1.702 1.640 1.683 1.675 0.032 0.019 300 1.635 1.575 1.668 1.626 0.048 0.029 400 1.636 1.534 1.665 1.612 0.069 0.043 500 1.595 1.502 1.660 1.586 0.079 0.050 600 1.557 1.463 1.661 1.560 0.099 0.063 700 1.512 1.436 1.669 1.539 0.119 0.077 800 1.533 1.415 1.63 9 1.529 0.112 0.073 900 1.523 1.387 1.584 1.498 0.101 0.067 1000 1.427 1.374 1.524 1.442 0.076 0.053 1100 1.409 1.354 1.457 1.407 0.051 0.037 1200 1.366 1.336 1.392 1.365 0.028 0.021 ** The peak value 100 # 10 sec, which equal =1.80 kN @ 107.6, 107, 108 .5 sec

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177 $ 75 ¡C : Time (sec) 75 ¡C1 (kN) 75 ¡C2 (kN) 75 ¡C2 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.693 1.660 1.710 1.688 0.026 0.015 200 1.516 1.502 1.614 1.544 0.061 0.040 300 1.470 1.386 1.580 1.479 0.097 0.066 400 1.452 1.389 1.553 1.465 0.083 0.057 500 1.354 1.367 1.550 1.423 0.110 0.077 600 1.420 1.352 1.454 1.409 0.052 0.037 700 1.425 1.352 1.445 1.407 0.048 0.034 800 1.388 1.323 1.419 1.377 0.049 0.036 900 1.397 1.307 1.409 1.371 0.056 0.041 1000 1.339 1.284 1. 374 1.332 0.045 0.034 1100 1.194 1.274 1.368 1.279 0.087 0.068 1200 1.198 1.262 1.366 1.275 0.085 0.067 ** The peak value 100 # 10 sec, which equal =1.80 kN @ 107.2, 108.1 106.7 sec $ 100 ¡C : Time (sec) 100 ¡C1 (kN) 100 ¡C2 (kN) 100 ¡C3 (kN) Averag e (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.646 1.603 1.612 1.620 0.023 0.014 200 1.526 1.452 1.487 1.488 0.037 0.025 300 1.438 1.366 1.433 1.412 0.040 0.029 400 1.425 1.291 1.421 1.379 0.076 0.055 500 1.345 1.314 1.386 1.349 0.036 0.027 600 1.289 1.288 1.389 1.322 0.058 0.044 700 1.268 1.269 1.344 1.294 0.044 0.034 800 1.297 1.256 1.264 1.273 0.022 0.017 900 1.121 1.232 1.266 1.207 0.076 0.063 1000 1.166 1.212 1.242 1.207 0.038 0.032 1100 1.081 1.215 1.258 1.184 0.092 0.078 1200 1.084 1.209 1.198 1.163 0.069 0.060 ** The peak value 100 # 10 sec, which equal =1.80 kN @ 108.3, 109.6, 109.0 sec

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178 $ 125 ¡C : Time (sec) 125 ¡C1 (kN) 125 ¡C2 (kN) 125 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.646 1.694 1.491 1.61 0 0.106 0.066 200 1.331 1.518 1.308 1.386 0.115 0.083 300 1.287 1.441 1.217 1.315 0.115 0.087 400 1.184 1.427 1.169 1.260 0.145 0.115 500 1.119 1.403 1.149 1.223 0.156 0.128 600 1.066 1.363 1.133 1.187 0.156 0.131 700 1.072 1.348 1.125 1.182 0.147 0. 124 800 1.022 1.264 1.126 1.137 0.122 0.107 900 1.049 1.256 1.115 1.140 0.105 0.092 1000 1.054 1.199 1.116 1.123 0.073 0.065 1100 1.082 1.185 1.102 1.123 0.055 0.049 1200 1.084 1.193 1.087 1.121 0.062 0.055 ** The peak value 100 # 10 sec, which equal = 1.80 kN @ 107.1, 106.5, 109,6 sec $ 150 ¡C : Time (sec) 150 ¡C 1 (kN) 150 ¡C2 (kN) 150 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.670 1.689 1.477 1.612 0.117 0.073 200 1.395 1.183 1.254 1.277 0.108 0.084 300 1.174 1.063 1.123 1.120 0.055 0.050 400 0.998 1.048 1.035 1.027 0.026 0.026 500 0.969 1.026 0.975 0.990 0.031 0.032 600 0.921 1.031 0.919 0.957 0.064 0.067 700 0.864 1.023 0.871 0.919 0.090 0.098 800 0.887 1.018 0.832 0.913 0.096 0.105 900 0.788 0.997 0.761 0.848 0.12 9 0.152 1000 0.854 1.002 0.768 0.875 0.118 0.135 1100 0.823 0.992 0.759 0.858 0.120 0.140 1200 0.816 0.959 0.785 0.853 0.093 0.108 ** The peak value 100 # 10 sec, which equal =1.80 kN @ 108.9, 109.1 109.6 sec

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179 $ 175 ¡C : Time (sec) 175 ¡C1 (kN) 175 ¡C2 (kN) 175 ¡C3 (kN) Average (kN) Standard Deviation COV 0 0 0 0 0 0 0 100 ** 1.656 1.656 1.660 1.657 0.002 0.001 200 1.488 1.183 1.128 1.266 0.194 0.153 300 1.246 1.063 0.941 1.084 0.153 0.142 400 1.203 1.048 0.934 1.062 0.135 0.127 500 1.188 1. 026 0.897 1.037 0.146 0.141 600 1.156 0.922 0.896 0.991 0.143 0.144 700 1.157 0.734 0.856 0.916 0.218 0.238 800 1.093 0.565 0.865 0.841 0.265 0.315 900 0.863 0.550 0.836 0.749 0.174 0.232 1000 0.665 0.556 0.837 0.686 0.142 0.207 1100 0.644 0.537 0.80 8 0.663 0.137 0.206 1200 0.639 0.535 0.819 0.665 0.144 0.216 ** The peak value 100 # 10 sec, which equal =1.80 kN @ 107.5, 107.3, 107.0sec

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180 Appendix B load displacement failure for variable width:

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181 0.25 B (( 1" width )) : $ 25 ¡C Shear stress ( ) $ 50 ¡C $ 75 ¡C

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182 $ 100 ¡C $ 125 ¡C $ 150 ¡C $ 175 ¡C

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183 $ 25 ¡C to 50 ¡C : $ 25 ¡C to 75 ¡C : $ 25 ¡C to 100 ¡C :

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184 $ 2 5 ¡C to 125 ¡C : $ 2 5 ¡C to 150 ¡C : $ 2 5 ¡C to 175 ¡C :

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185 $ 0.5 B (( 2 wid th )) : $ 25 ¡C Shear stress ( ) $ 50 ¡C $ 75 ¡C

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186 $ 100 ¡C $ 125 ¡C $ 150 ¡C $ 175 ¡C

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187 $ 2 5 ¡C to 50 ¡C : $ $ 2 5 ¡C to 75 ¡C : $ 2 5 ¡C to 100 ¡C :

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188 $ 2 5 ¡C to 125 ¡C : $ 2 5 ¡C to 150 ¡C : $ 2 5 ¡C to 175 ¡ C :

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189 $ 0.75 B width ( ) $ 25 ¡C Shear stress ( ) $ 50 ¡C $ 75 ¡C

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190 $ 100 ¡C $ 125 ¡C $ 150 ¡C $ 175 ¡C

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191 $ 2 5 ¡C to 50 ¡C : $ 2 5 ¡C to 75 ¡C : $ 2 5 ¡C to 100 ¡C :

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192 $ 2 5 ¡C to 125 ¡C : $ 2 5 ¡C to 15 0 ¡C : $ 2 5 ¡C to 175 ¡C :

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193 Comparing different avg by different width at the same temperature: @ 25 o C : @ 50 o C : @ 75 o C :

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194 @ 100 o C : @ 125 o C : @ 150 o C :

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195 @ 175 o C :

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196 Effect length ( L= 3.6" B= 2") $ 25 ¡C Shear stress ( ) $ 50 ¡C $ 75 ¡C

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197 $ 100 ¡C $ 125 ¡C $ 150 ¡C $ 175 ¡C

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198 $ 2 5 ¡C to 50 ¡C : $ 2 5 ¡C to 75 ¡C : $ 2 5 ¡ C to 100 ¡C :

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199 $ 2 5 ¡C to 125 ¡C : $ 2 5 ¡C to 150 ¡C : $ 2 5 ¡C to 175 ¡C :

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200 1.25 Effect length (L= 4.5" B= 2") $ 25 ¡C Shear stress ( ) $ 50 ¡C $ 75 ¡C

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201 $ 100 ¡C $ 125 ¡C $ 150 ¡C $ 175 ¡C

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202 $ 2 5 ¡C to 50 ¡C : $ 2 5 ¡C to 75 ¡C : $ 2 5 ¡C to 100 ¡C :

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203 $ 2 5 ¡C to 125 ¡C : $ 2 5 ¡C to 150 ¡C : $ 2 5 ¡C to 175 ¡C :

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204 1.5 Effect length ( L= 5.4" B= 2") $ 25 ¡C Shear stress ( ) $ 50 ¡C $ 75 ¡C

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205 $ 100 ¡C $ 125 ¡C $ 150 ¡C $ 175 ¡C

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206 $ 2 5 ¡C to 50 ¡C : $ 2 5 ¡C to 75 ¡C : $ 2 5 ¡C to 100 ¡C :

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207 25 ¡C to 125 ¡C : $ 2 5 ¡C to 150 ¡C : $ 2 5 ¡C to 175 ¡C :

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208 Comparing different avg by different length at the same temperature: @ 25 o C : @ 50 o C : @ 75 o C :

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209 @ 100 o C : @ 125 o C : @ 150 o C :

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210 @ 175 o C :

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211 Beams :: 2. 25 control strengthen. (2) (2)

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212

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213

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214 3. 25 control unstrengthen.

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215 4. 25 control unstrengthen.

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216

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217 5. 75 C strengthen.

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218

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219 6. 100 C strengthen.

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220

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221 7. 125 C strengthen.

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222 8. 150 C strengthen.

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223

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224 Second Category 8. 150 C strengthen. @ 30 mins

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225

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226 9. 150 C strengthen. @ 45 mins

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227 10. 150 C strengthen. @ 60 mins

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228

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229 11. 150 C strengthen. @ 75 mins

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230

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231 12. 125 C strengthen. @ 30 mins

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232

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2 33 13. 100 C strengthen. @ 30 mins

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234

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235 14. 75 C stren gthen. @ 30 mins

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236

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237 15. 25 C strengthen

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238

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239