Citation
Debonding-control of CFRP-strengthened concrete members

Material Information

Title:
Debonding-control of CFRP-strengthened concrete members
Creator:
Ibraheem, Ahmed ( author )
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
Publication Date:
Language:
English
Physical Description:
1 electronic file (230 pages) : ;

Thesis/Dissertation Information

Degree:
Master's ( Master of science)
Degree Grantor:
University of Colorado Denver
Degree Divisions:
Department of Civil Engineering, CU Denver
Degree Disciplines:
Civil engineering
Committee Chair:
Kim, Yail Jimmy
Committee Members:
Chang, Nien-Yin
Li, Chengyu

Subjects

Subjects / Keywords:
Fiber-reinforced concrete ( lcsh )
Carbon fiber-reinforced plastics ( lcsh )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Abstract:
An innovative bonding methodology is presented to preclude the debonding failure of composite sheets adhered to a concrete substrate. Such a problem is typical in composite strengthening for constructed concrete structures because the composite-concrete interface fails prior to achieving the full capacity of the composite. The hypothesis to be tested is that the grooved surface of concrete filled with an epoxy adhesive can provide a mechanical interlock to the interface so that stepwise failure takes place, rather than abrupt complete debonding of the sheets. To confirm the hypothesis, an experimental program is conducted with carbon fiber reinforced polymer composite sheets bonded to a concrete block having various numbers of periodic grooves (1 groove to 5 grooves). Monotonic tension is applied to the bonded joints to examine strain profiles and failure characteristics. Another interest of the proposed bonding scheme is that stress singularity along the interface is periodically controlled. In the first part of this research 30 blocks (prisms) strengthen by epoxy and CFRP after modify surface of these blocks by made grooves 20 mm (0.75in) width and 15 mm (0.6in) depth and filled by epoxy with various no of grooves from (1 groove to 5 grooves) another 30 blocks (prisms) strengthen by epoxy and CFRP but applied U wraps at locations of grooves, last 30 blocks (prisms) strengthen by epoxy, SMP and CFRP, SMP applied at locations of grooves. The blocks (prisms) with grooves showed high load carrying capacity and high energy dissipation. In the second part of this research nine beams strengthen with CFRP and epoxy with two categories of grooves (3 groves and Uniform distributed grooves) beams tested after changing location of first groove from 0 mm (0 in), 50mm (2 in) and 100 mm (4 in) form free end of CFRP sheet. Beams with end groove 0 mm (0 in) from CFRP showed high load carrying capacity.
Thesis:
Thesis (M.S.)--University of Colorado Denver, 2017.
Bibliography:
Includes bibliographical references.
System Details:
System requirements: Adobe Reader.
General Note:
n3p
Statement of Responsibility:
by Ahmed Ibrheem

Record Information

Source Institution:
University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
on10301 ( NOTIS )
1030159171 ( OCLC )
on1030159171

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Full Text
DEBONDING-CONTROL OF CFRP- STRENGTHENED CONCRETE MEMBERS
by
AHMED IBRAHEEM
B.S., Metropolitan State University of Denver, 2015 B.S, University of Technology, 2001
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 Program
2017


This thesis for the Master of Science degree by Ahmed Ibraheem Has been approved for the Civil Engineering Program by
Yail Jimmy Kim, Chair Nien-Yin Chang Chengyu Li
December 16, 2017


Ibraheem Ahmed (M.S., Civil Engineering)
Debonding-control of CFRP- strengthened Concrete Members Thesis directed by Professor Yail Jimmy Kim
ABSTRACT
An innovative bonding methodology is presented to preclude the debonding failure of composite sheets adhered to a concrete substrate. Such a problem is typical in compositestrengthening for constructed concrete structures because the composite-concrete interface fails prior to achieving the full capacity of the composite. The hypothesis to be tested is that the grooved surface of concrete filled with an epoxy adhesive can provide a mechanical interlock to the interface so that stepwise failure takes place, rather than abrupt complete debonding of the sheets. To confirm the hypothesis, an experimental program is conducted with carbon fiber reinforced polymer composite sheets bonded to a concrete block having various numbers of periodic grooves (1 groove to 5 grooves). Monotonic tension is applied to the bonded joints to examine strain profiles and failure characteristics. Another interest of the proposed bonding scheme is that stress singularity along the interface is periodically controlled. In the first part of this research 30 blocks (prisms) strengthen by epoxy and CFRP after modify surface of these blocks by made grooves 20 mm (0.75in) width and 15 mm (0.6in) depth and filled by epoxy with various no of grooves from (1 groove to 5 grooves) another 30 blocks (prisms) strengthen by epoxy and CFRP but applied U wraps at locations of grooves, last 30 blocks (prisms) strengthen by epoxy, SMP and CFRP, SMP applied at locations of grooves. The blocks (prisms) with grooves showed high load carrying capacity and high energy dissipation. In the second part of this research nine beams strengthen with CFRP and epoxy
with two categories of grooves (3 groves and Uniform distributed grooves) beams tested after
iii


changing location of first groove from 0 mm (0 in), 50mm (2 in) and 100 mm (4 in) form free end of CFRP sheet. Beams with end groove 0 mm (0 in) from CFRP showed high load carrying capacity.
The form and content of this abstract are approved. I recommend its publication.
Approved: Yail Jimmy Kim
IV


DEDICATION
I dedicate this work for my family especially my wife, my dad, my mother and my kids who support me in my life and encourage me to face all life challenges.
Also, dedicate this work all people who support me to complete this research.
v


ACKNOWLEDGEMENTS
This degree is one of my biggest challenging in my life, especially for a person who is responsible of a family and working full time job, it is not easy but not impossible.
I would thank all persons who support, advise, asset, pray for me to reach my goal, also I would thank University of Colorado Denver for giving me this opportunity.
First, I would thank my advisor Dr. Kim for advising and supporting me, I could not finish this research without his advising and assistance to reviewing my data results, and I would thank him for supporting part of my tuition, also I would thank all members in civil engineering department, committee chair and members.
Secondly, I would thank my family Mom, Dad, wife and my kids who support me to reach my goal, especially my Dad and Mom who pray for me, also I would thank the great lady in my life (my wife), she is always supporting me and encouraging me to not give up and push me ahead to reach my goal.
And, I would thank all my friends who assist me to complete my laboratory work, especially Ibrahim bumadian, Mohammed Abahiri, Abdullah Alajmi, and Thushera.
Finally, I thank all laboratory members Tom, Jack, Peter, and Christin for assistance and supporting me to complete experimental work.
vi


TABLE OF CONTENTS
1. INTRODUCTION............................................................1
1.1 General................................................................1
1.2 Research Significance..................................................2
1.3 Objectives.............................................................3
1.4 Scope..................................................................4
1.5 Thesis outline.........................................................5
2 LITERATURE REVIEW.......................................................7
2.1 Introduction...........................................................7
2.2 Background.............................................................7
2.3 Fiber Reinforced Polymer (FRP).........................................8
2.3.1 Introduction:.....................................................8
2.3.2 FRP types.........................................................9
2.3.3 FRP use..........................................................10
2.4 Epoxy types and specifications........................................11
2.5 Previous study and research on concrete strengthened by FRP...........12
2.5.1 Failure mode of Concrete Blocks..................................12
2.5.2 Mechanism of bond transfer from FRP to concrete..................13
2.5.3Behavior of structure members strengthened by FRP.................14
2.5.4 Failure mode of RC members strengthened by FRP...................16
3 BEHAVIOR OF CONCRETE BLOCKS STRENGTHENED WITH FRP SHEETS SUBJECTED TO TENSION..............................................20
3.1 General overview......................................................20
3.2 Experimental program..................................................20
3.2.1 Test specimens...................................................20
vii


3.2.2 Test setup.............................................................22
3.3 Materials...................................................................23
3.3.1 Concrete...............................................................23
3.3.2 Epoxy..................................................................23
3.3.3 SMP....................................................................24
3.3.4 FRP....................................................................24
3.4 Test Matrix.................................................................25
3.5 Test result of specimens with grooves.......................................27
3.5.1 Load-carrying capacity.................................................28
3.5.2 Load-displacement behavior.............................................29
3.5.3 Strain behavior of blocks has grooves..................................30
3.5.4 Failure Mode...........................................................31
3.5.5 Energy dissipation.....................................................31
3.6 Test result specimense with U-wrap..........................................32
3.6.1 Load-carrying capacity.................................................32
3.6.2 Load-displacement behavior.............................................33
3.6.3 Strain behavior of blocks..............................................34
3.6.4 Energy dissipation behavior............................................35
3.6.5 Failure Mode...........................................................35
3.7 Test result of specimens with SMP...........................................36
3.7.1 Load -carrying capacity................................................36
3.7.2 Load-displacement behavior.............................................37
3.7.3 Strain behavior of concrete Blocks strengthened by epoxy and SMP.......38
viii


5
6
3.7.4 Energy dissipation behavior....................................
3.7.5 Failure mode...................................................
3.8 Results and discussion..........................................
4 BEHAVIOR OF CFRP-STRENGTHENED BEAMS WITH MULTIPLE
GROOVES................................................................
4.1 General Overview...................................................
4.2 Experimental programme............................................
4.2.1 Test Matrix....................................................
4.2.2 Materials......................................................
4.2.3 Beams preparation..............................................
4.2.4 Test setup.....................................................
4.3 Results and discussion..............................................
4.3.1 Load carrying capacity.........................................
4.3.2 Failure mode...................................................
4.3.3 Comparison in failure mode for concrete blocks and beams.......
4.3.4 Crack propagation..............................................
Summary and conclusion.................................................
References.............................................................
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205
IX


LIST OF TABLES
Table 2-1: FRP types and properties..................................................19
Table 2-2: Epoxy Physical Properties.................................................19
Table 3-1: Technical data for sily modified polymer SMP).............................41
Table 3-2: Concert mix design........................................................42
Table 3-3: compressive strength results for cylinders at 28 days.....................42
Table 3-4: Test results For Prisms hasl,2,3,4&5 Grooves..............................43
Table 3-5 : Standard deviation and COV for phase I test results.......................44
Table 3-6: Test Result for Prisms have 1,2,3,4 and 5 U-wrap...........................45
Table 3-7: Standard deviation and COV for phase II test results.......................46
Table 3-8: Test Result for Prisms have 1,2,3,4 and 5 SMP layers.......................47
Table 3-9: Standard deviation and COV for phase III test results......................48
Table 4-1: Summary Beams Test behavior...............................................163
Table 4-2: Summary beams test results................................................164
x


LIST OF FIGURES
Figure 2-1: Failure Mode in concrete blocks
Figure 2-2: (a) Flexure failure by FRP rupture, (b) Flexure failure by concrete crushing, (c) shear failure, (d) concrete cover separation, (e) plate-end interfacial debonding, (f) flexure crack -induced in interfacial debonding, (g) critical diagonal crack-induced interfacial debonding.
Figure 3-l(a): Top view for COT prism detail, (b) side view for COT prism detail, (c) COT prism test setup, (d) COT side view test setup
Figure 3-2: (a) COT load -displacement test result for prism COT-1, FRP debonding in 6.65kn and displacement 0.06mm, (b) COT load -displacement test result for prism COT-2, FRP debonding in 6.58kn and displacement 0.05mm
Figure 3-3:(C) COT load -displacement test result for prism COT-3, FRP debonding in 6.18kn and displacement 0.09mm, (d) COT load -displacement test result for prism COT-4, FRP debonding in 5.20kn and displacement 0.07mm
Figure 3-4: (e) COT load -displacement test result for prism COT-5, FRP debonding in 5.34Kn and displacement 0.10mm, (d) COT load-displacement for all COT prisms
Figure 3-5: Top view side view for PG1 prism detail, (b) PG1 prism test setup
Figure 3-6: (a) load -displacement test result for prism PG1-1, FRP ruptured and hairy cracks appeared in 9.18kn, and displacement 0.26mm (b) load -displacement test result for prism PG1-2, FRP ruptured and hairy cracks appeared in 7.76kn and displacement 0.22mm
Figure 3-7: (a) load -displacement test result for prism PG1-3, FRP ruptured and hairy cracks appeared in 9.25kN and displacement 0.23mm (b) load -displacement test result for prism PG1-4, FRP ruptured in 10.51 and displacement 0.26mm
Figure 3-8: (a) load -displacement test result for prism PG1-5, FRP debonding and hairy cracks appeared in 8.44 kN and displacement 0.15mm, (b) load -displacement test result for prism for all PG1 prisms
xi


Figure 3-9: (a) Top view side and view of PG2 prism detail, (b) PG2 prism test setup
Figure 3-10: (a) load -displacement test result for prism PG2-1, FRP ruptured, and hairy cracks appeared in 9.49kn, and displacement 0.18mm (b) load -displacement test result for prism PG2-2, FRP ruptured and hairy cracks appeared in 9.79kn and displacement 0.20mm
Figure 3-11: (a) load -displacement test result for prism PG2-3, FRP ruptured, and hairy cracks appeared in 10.87kn and displacement 0.20mm, (b) load -displacement test result for prism PG2-4, FRP ruptured in 8.40kN and displacement 0.18mm
Figure 3-12: (a) load -displacement test result for prism PG2-5, FRP ruptured in 10.79kn and displacement 0.16mm, (b) load -displacement test result for all PG2 prisms
Figure 3-13: (a)Top view and side view of PG3 prism detail, (b) PG3 prism test setup
Figure 3-14: (a) load -displacement test result for prism PG3-1, FRP ruptured in 9.74kn and displacement 0.22mm, (b) load -displacement test result for prism PG3-2, FRP ruptured in
11.1 lkN and displacement 0.22mm
Figure 3-15: (a) load -displacement test result for prism PG3-3, FRP ruptured 8.77kN and displacement 0.17mm, (b) load -displacement test result for prism PG3-4, FRP ruptured and hairy cracks appeared in 11.43kN and displacement 0.17mm
Figure 3-16: (a) load -displacement test result for prism PG3-5, FRP ruptured, and hairy cracks appeared in 10.30 and displacement 0.17mm, (b) load -displacement test result for all PG3 prism
Figure 3-17: (a)Top view and side view of PG4 prism detail, (b) PG4 prism test setup
Figure 3-18: (a) load -displacement test result for prism PG4-1, FRP ruptured, and hairy cracks appeared in 11.27kN and displacement 0.16mm, (b) load -displacement test result for PG4-2 prism, FRP ruptured in 9.55 kN and displacement 0.19mm
Figure 3-19: (a) load -displacement test result for prism PG4-3, FRP ruptured and hairy cracks appeared in 11.07kN and displacement 0.23mm, (b) load -displacement test result for PG4-4 prism, FRP ruptured in 10.77kN and displacement 0.25mm
xii


Figure 3-20: (a) load -displacement test result for prism PG4-5, FRP ruptured in 9.10kn and
displacement 0.21mm, (b) load -displacement test result for all PG4 prisms.
Figure 3-21: (a) Top view and side view of PG5 prism detail, (b) PG4 prism test setup
Figure 3-22: (a) load -displacement test result for prism PG5-1, FRP ruptured and hairy cracks appeared in 12.84kN and displacement 0.25mm, (b) load -displacement test result for PG5-2 prism, FRP ruptured and hairy cracks appeared in 10.22kN and displacement 0.23mm
Figure 3-23: (a) load -displacement test result for prism PG5-3, FRP ruptured, and hairy cracks appeared in 11.52 kN, and displacement 0.27mm, (b) load -displacement test result for PG5-4 prism FRP ruptured and hairy cracks appeared in 10.20kN and displacement 0.29mm
Figure 3-24: (a) load -displacement test result for prism PG5-5, FRP ruptured in 8.37kN and displacement 0.30mm (b) load -displacement test result for all PG5 prisms
Figure 3-25: (a) strain gauges location for COT, (b) strain gauge location for PG1
Figure 3-26: (a) strain gauges location for PG2, (b) strain gauge location for PG3
Figure 3-27: (a) strain gauges location for PG4, (b) strain gauge location for PG5
Figure 3-28: (a) strain gauge result for COT, (b) strain gauge results for PG1
Figure 3-29: (a) strain gauges results for PG2, (b) strain gauge results for PG3
Figure 3-30: (a) strain gauges results for PG4, (b) strain gauge results for PG5
Figure 3-30 a: (a) strain profile for COT prism, (b) strain profile for PG1 prism
Figure 3-30 b: (a) strain profile for PG2 prism, (b) strain profile for PG3 prism
Figure 3-30C: (a) strain profile for PG4 prism, (b) strain profile for PG5 prism
Figure 3-31: (a) Energy dissipation for COT, (b) Energy dissipation for PG1, (c) Energy dissipation for PG2, (d) Energy dissipation for PG3, (e) Energy dissipation for PG4, (F) Energy dissipation for PG5
Figure 3-32: (a) P1U Top and side view, (b) strain gauge location for P1U
xiii


Figure 3-33: (a) Load -displacement for PIU-1 prism, FRP ruptured in 9.97kn and displacement 0.13mm, (b) Load-displacement for P1U-2 prism, FRP ruptured in 8.6kN and displacement 0.13mm
Figure 3-34: (a) Load -displacement for PIU-3 prism, FRP ruptured in 8.76kN and displacement 0.11mm (b) Load-displacement for P1U-4 prism, FRP ruptured in 11,67kN and displacement 0.16mm
Figure 3-35: (a) Load -displacement for PIU-5 prism, FRP ruptured in 9.24kn and displacement 0.13mm (b) Load-displacement for all P1U prisms
Figure 3-36: (a) Top and side view for P2U prisms, (b) strain gauges locations for PlUprism
Figure 3-37: (a) Load -displacement for P2U-1 prism, FRP ruptured in 8.4 kN and displacement 0.15mm (b) Load-displacement for P2U-2 prism, FRP ruptured in 10.28kN and displacement 0.13mm
Figure 3-38: (a) Load -displacement for P2U-3 prism, FRP ruptured in 9. lOkn and displacement 0.16mm (b) Load-displacement for P2U-4 prism, FRP ruptured in 10.75kN and displacement 0.14mm
Figure 3-39: (a) Load -displacement for P2U-5 prism, FRP ruptured in 10.03kN and displacement 0.14mm (b) Load-displacement for all P2U prisms
Figure 3-40: (a) Top and side view for P3U prisms, (b) strain gauges location for P3U prisms
Figure 3-41: (a) Load -displacement for P3U-1 prism, FRP ruptured and debonding in 8.73kN and displacement 0.09mm (b) Load-displacement for P3U-2 prism, FRP ruptured in 9.76kn and displacement 0.09mm
Figure 3-42: (a) Load -displacement for P3U-3 prism, FRP ruptured in 9.16kn and displacement 0.09mm (b) Load-displacement for P3U-4 prism, FRP ruptured in 10.72kN and displacement 0.11mm
xiv


Figure 3-43 :(a) Load -displacement for P3U-5 prism, FRP ruptured in 10.79kn and
displacement 0.1mm (b) Load-displacement for all P3U prisms
Figure 3-44: (a) Top and Side view for P4U prism, (b) strain gauges locations for P4U prism
Figure 3-45: (a) Load-displacement for P4U-1 prism, FRP ruptured in 9.94kn and displacement 0.13mm (b) Load-displacement for P4U-2 prism, FRP ruptured in 10.26kN and displacement 0.14mm
Figure 3-46: (a) Load -displacement for P4U-3 prism, FRP ruptured in 8.33kN and displacement 0.13mm (b) Load-displacement for P4U-4 prism, FRP ruptured in 11,30kN and displacement 0.17mm
Figure 3-47: (a) Load-displacement for P4U-5 prism, FRP ruptured in 10.30kn and displacement 0.15mm (b) Load-displacement for all P4U prisms
Figure 3-48: (a) Top and Side view for P5U prism, (b) strain gauges location for P5U prism
Figure 3-49: (a) Load-displacement for P5U-1 prism, FRP ruptured in 10.67kN and displacement 0.13mm (b) Load-displacement for P5U-2 prism, FRP ruptured in 8.98kn and displacement 0.1mm
Figure 3-50: (a) Load -displacement for P5U-3 prism, FRP ruptured in 9.20kn and displacement 0.1mm, (b) Load-displacement for P5U-4 prism, FRP ruptured in 11,22kN and displacement 0.12mm
Figure 3-51: (a) Load-displacement for P5U-5 prism, FRP ruptured in 10.53kN and displacement 0.11mm (b) Load-displacement for all P5U prisms
Figure 3-52: (a) strain gauges results for P1U, (b) strain gauge results for P2U Figure 3-53: (a) strain gauges results for P3U, (b) strain gauge results for P4U Figure 3-54: (a) strain gauges results for P5U
Figure 3-54A: (a) Strain Profile for COT prism, (b) Strain profile for P1U Prism Figure 3-54B: (a) Strain Profile for P2U prism, (b) Strain profile for P3U Prism
xv


Figure 3-54C: (a) Strain Profile for P4U prism, (b) Strain profile for P5U Prism
Figure 3-55a: (a) Energy dissipation for COT, (b) Energy dissipation for P1U, (c) Energy dissipation for P2U, (d) Energy dissipation for P3U, (e) Energy dissipation for P4U, (F) Energy dissipation for P5U.
Figure 3-55: (a) Top and side view for PIS prisms, (b) strain gauges location for PIS prisms.
Figure 3-56: (a) Load-displacement for P1S-1 prism, FRP debonding in 6.23kN and displacement 0.1mm (b) Load-displacement for P1S-2 prism, FRP ruptured in 4.94 and displacement 0.10mm
Figure 3-57: (a) Load -displacement for P1S-3 prism, FRP debonding in 5.8kN and displacement 0.09mm (b) Load-displacement for P1S-4 prism, FRP debonding in 5.73kN and displacement 0.1mm
Figure 3-58: (a) Load -displacement for P1S-5 prism, FRP debonding in 6.13kN and displacement 0.1mm (b) Load-displacement for all PIS prisms
Figure 3-59: (a) Top and side view for P2S prisms, (b) strain gauges location for P2S prisms
Figure 3-60: (a) Load-displacement for P2S-1 prism, FRP, debonding in 5.99kN and displacement 0.12mm (b) Load-displacement for P2S-2 prism FRP, debonding in 5.55kN and displacement 0.1mm
Figure 3-61: (a) Load -displacement for P2S-3 prism, FRP debonding in 5.87kN and displacement 0.08mm (b) Load-displacement for P2S-4 prism, FRP debonding in 5.76kN and displacement 0.08mm
Figure 3-62: (a) Load -displacement for P2S-5 prism, FRP debonding in 5.05kN and displacement 0.1mm (b) Load-displacement for all P2S prisms
Figure 3-63: (a) Top and side view for P3S prisms, (b) strain gauges location for P3S prisms
Figure 3-64: (a) Load -displacement for P3S-1 prism, FRP debonding in 6.23kN and displacement 0.2mm (b) Load-displacement for P3S -2 prism, FRP debonding in 6.99kN and displacement 0.16mm
xvi


Figure 3-65: (a) Load -displacement for P3S-3 prism, FRP debonding in 7.03kN and displacement 0.15mm (b) Load-displacement for P3S -4 prism, FRP debonding in 6.58kN and displacement 0.15mm
Figure 3-66: (a) Load -displacement for P3S-5 prism, FRP debonding in 5.06kN and displacement 0.14mm (b) Load-displacement for all P3S prisms.
Figure 3-66a: (a) Top and side view for P4S prisms, (b) strain gauges location for P4S prisms
Figure 3-67: (a) Load-displacement for P4S-1 prism, FRP debonding in 4.90kN and displacement 0.15mm (b) Load-displacement for P4S -2 prism, FRP debonding in 5.46kN and displacement 0.13mm
Figure 3-68: (a) Load -displacement for P4S-3 prism, FRP debonding in 6.26kN and displacement 0.12mm, (b) Load-displacement for P4S-4 prism, FRP debonding in 5.68kN and displacement 0.15mm
Figure 3-69: (a) Load -displacement for P4S-5 prism, FRP debonding in 4.68 kN and displacement 0.14mm (b) Load-displacement for all P4S prisms
Figure 3-70: (a) Top and side view for P5S prisms, (b) strain gauges location for P5S prisms
Figure 3-71: (a) Load -displacement for P5S-1 prism, FRP debonding in 5.16kN and displacement 0.08mm (b) Load-displacement for P5S-2 prism, FRP debonding in 4.47kN and displacement 0.16mm
Figure 3-72: (a) Load -displacement for P5S-3 prism, FRP debonding in 6.02kN and displacement 0.2mm (b) Load-displacement for P5S-4 prism, FRP debonding in 5.96kN and displacement 0.19mm
Figure 3-73: (a) Load -displacement for P5S-5 prism, FRP debonding in 4.74kN and displacement 0.14mm (b) Load-displacement for all P5S prisms
Figure 3-74: (a) strain gauges results for PIS, (b) strain gauge results for P2S Figure 3-75: (a) strain gauges results for P3S, (b) strain gauge results for P4S
XVII


Figure 3-76: (a) strain gauges results for P5S
Figure 3-76a: (a) Strain Profile for COT prism, (b) Strain profile for PIS Prism
Figure 3-76 b: (a) Strain Profile for P2S prism, (b) Strain profile for P3S Prism
Figure 3-76c: (a) Strain Profile for P4S prism, (b) Strain profile for P5S Prism
Figure 3-77: (a) Energy dissipation for COT, (b) Energy dissipation for PIS, (c) Energy dissipation for P2S, (d) Energy dissipation for P3S, (e) Energy dissipation for P4S, (F) Energy dissipation forP5S
Figure 3-77a: (a) comparing between load carrying for three phases, (b) comparing between Energy dissipation for three phases
Figure 3-77b: (a) concrete cylinder test, (b) concrete cylinder test, (c)concrete block grooves Preparation, (d) prism grooves preparation
Figure 3-78: (a) Gripping Details, (b) prisms FRP placement, (c) COT failure, (d) COT prism failure
Figure 3-79: (a) PG1 prism failure, (b) PIG prism failure, (c) PG2 prism failure, (d) PG2 prism failure
Figure 3-80: (a) PG3 Test setup, (b) PG3 prism failure, (c) PG3, PG4& PG5 prisms failure, (d)PG3, PG4, PG5 and COT prisms failure
Figure 3-81: (a)PG5 prism failure, (b)PG5 prism failure, (c)PlU prism failure, (d) PIU prism failure
Figure 3-82: (a) P2Ci prism failure, (b) P2Ci prism failure, (c) P3Ci prism failure, (d) P3Ci prism failure
Figure 3-83: (a) P4Ci prism failure, (b) P4Ci Prism failure, (c) P5Ci prism failure, (d) P5Ci prism failure
Figure 3-84: (a) PIS prism failure, (b) PIS prism failure, (c) P2S prism failure, (d) P2S prism failure
xvm


Figure 3-85: (a) P3S prism failure, (b) P3S prism failure, (c) P4S prism failure, (d) P4S prism failure
Figure 3-86: (a), (b), (c) & (d) P5S prisms failure
Figure 4-1: (a) Reinforcement Details for COT beam without FRP, (b) Reinforcement Details for COT beam with FRP and without grooves
Figure 4-2: (a) Reinforcement Details for BG3-0 beam, (b) crack pattern for BG3-2 beam
Figure 4-3: (a) Reinforcement Details for BG3-4 beam with FRP, (b) crack pattern for BDG-0 beam with FRP
Figure 4- 4: (a) Reinforcement Details for BDG-2 beam with FRP, (b) crack pattern for BDG-4 beam with FRP
Figure 4-5: Beam test Setup
Figure 4-6: (a) Test result COT beam load-displacement (b) PI gauges test result for COT beam
Figure 4-7: COT beam failure flexural crack appeared at 10 KN and propagated Flexural Shear cracks propagate at 30 kN Concrete crush, and beam fail at 47.2 Kn, (e) crack pattern for COT beam.
Figure 4 -8: (a) Test result COTCFRP beam load-displacement (b) PI gauges test result for COTCFRP beam
Figure 4 -9: (a) strain gauge result for COT CFRP left side, (b) strain gauge result for COT CFRP right side
Figure 4-10: (a) Strain Gauges profile for COT CFRP, (b) Crack Pattern for COT CFRP
Figure 4-11 DIC capture for crack propagation in different load level for COT CFRP
Figure 4-12: COT CFRP beam failure flexural crack appeared at 20 KN and propagated Flexural Shear cracks propagate at 45 kN Concrete crush, and beam fail at 57.1 kN
Figure 4-13: (a) load-displacement test result BG3-0 beam (b) PI gauges test result for BG3-0
Beam
Figure 4-14: (a) strain gauge result for BG3-0 left side, (b) strain gauge result for BG3-0 right side
xix


Figure 4-15: (a) Strain Gauges profile for BG3-0, (b) Crack pattern for BG3-0
Figure 4-16: DIC capture for crack propagation in different load level for BG3-0
Figure 4-17: BG3-0 beam failure flexural crack appeared at 23 KN and propagated Flexural Shear cracks propagate at 53.9 kN Concrete crush, and beam fail at 64.9 kN
Figure 4-18: (a) load-displacement result for BG3-2 beam, (b) PI gauges results for BG3-2
Figure 4-19: BG3-2 beam failure flexural crack appeared at 31 KN and propagated Flexural Shear cracks propagate at 49 kN Concrete crush, and beam fail at 64.27 Kn, (e) Crack pattern for BG3-2
Figure 4-20: (a) load-displacement for BG3-4, (b) PI gauges result for BG3-4 beam
Figure 4-21: (a) strain gauges results for BG3-4 left side, (b) Strain gauge results for BG3-4 right side
Figure 4-22: (a) Strain gauge profile for BG3-4, (b) crack pattern for BG3-4 Beam
Figure 4-23: DIC capture for BG3-4 crack propagation in different load level
Figure4-24: BG3-4 beam failure flexural crack appeared at 22 KN and propagated Flexural Shear cracks propagate at 35 kN Concrete crush, and beam fail at 63.9 kN
Figure 4-25: (a) load-displacement for BDG-0, (b) PI gauges result for BDG-0 beam
Figure 4-26: (a) Strain gauges results for BDG-0 left side, (b) strain gauges results for BDG-0 right side
Figure 4-27: (a) Strain gauges profile results for BDG-0, (b) crack pattern for BDG-0 beam
Figure 4-28: DIC capture for crack propagation in different load level for BDG-0
Figure 4-29: BDG-0 beam failure flexural crack appeared at 29.2 KN and propagated, Flexural Shear cracks propagate at 61.2 kN Concrete crush, and beam fail at 72.1 kN
Figure 4-30: (a) Load-displacement for BDG-2, (B) PI Gauge results for BDG-2
Figure 4-31: (a) Strain gauge results for BDG-2 Left side, (b) Strain gauge results for BDG-2 right side
Figure 4-32: (a) strain gauge profile result for BDG-2 beam, (b) Crack pattern for BDG-2 Figure 4-33: DIC capture for crack propagation in different load level for BDG-2
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Figure 4-34: BDG-2 beam failure flexural crack appeared at 25 KN and propagated, Flexural Shear cracks propagate at 61.0 kN Concrete crush and beam failed at 69.8 kN
Figure 4-35: Load-displacement results for BDG-4, (b) PI gauges test result for BDG-4 beam
Figure 4-36: (a) strain gauge result for BDG-4 beam left side, (b) Strain gauge result for BDG-4 beam right side
Figure 4-37: (a) strain gauge profile for BDG-4 beam, (b) crack pattern for BDG-4 Beam
Figure 4-38: DIC capture for crack propagation in different load level for BDG-4
Figure 4-39: BDG-4 beam failure flexural crack appeared at 22.9 KN and propagated, Flexural Shear cracks propagate at 60.2 kN Concrete crush, and beam fail at 65.3 kN
Figure 0-40: (a) Crack propagation for BDG-0, (b) Crack propagation for BG3-0
xxi


Notation
BDG-0 Beam has uniform distributed grooves terminated in end edge of FRP
BDG-2 Beam has uniform distributed grooves terminated in 2 in away from end edge of FRP
BDG-4 Beam has uniform distributed grooves terminated in 4 in away from end edge of FRP
BG3-0 Beam has three grooves terminated in end edge of FRP
BG3-2 Beam has three grooves terminated 2 in away from end edge of FRP
BG3-4 Beam has three grooves terminated 4 in away from end edge of FRP
COT Plain surface Concrete block (without groove), beam without groove and FRP
COT CFRP Beam strengthened by FRP without grooves
Gl, G2, G3... Strain Gauge #1,2,3...
PIS Prism has one SMP layer
P1U Prism has one U-wrap
P2S Prism has two SMP layer
P2U Prism has two U-wrap
P3S Prism has three SMP layer
P3U Prism has three U-wrap
P4S Prism has four SMP layer
P4U Prism has four U-wrap
P5S Prism has five SMP layer
XXII


P5U Prism has five U-wrap
PG1 Prism has one groove
PG2 Prism has two grooves
PG3 Prism has three grooves
PG4 Prism has four grooves
PG5 Prism has five grooves
XX111


CHAPTER ONE
INTRODUCTION
2.2 General
Structures are exposing too many environmental factors through a lifetime and cause decreasing in the lifetime of the structure. Flood, fire, seismic, traffics .. .etc all these environmental effects cause lowering in the life of structures, structures it composite of structures members (beams, columns, slab). These members are creating from concrete (cement, sand, gravel, reinforcement bars), these materials are exposed to a hard condition like corrosion, contraction, elongation, relaxation and this effect directly on building performance. In the United States, 40% of bridges need maintenance and rehabilitation through bridge lifetime (Wai-Fah Chen and Lian Duan 2000).
Many solutions were created by engineers to retrofit members and rehabilitation to correct performance for carrying applying load to extend structure lifetime, one of these methods is adding concrete, steel jacket, steel encasement and adding steel straps to members to increase strength and ductility (Hiroshi Fukuyama and Shunsuke Sugano 2000).
However, these techniques will add more service load to structure and foundations may not design for additional weight.
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The fantastic universal solution is using lightweight material Fiber- reinforced polymer (FRP) to strengthen members and increase member’s performance strength, it has used by many engineers since 1990 (Cheng and Teng 2003).
It is light material, noncorrosive and has high tensile strength, FRP material consists of glass and carbon, it is glued to structure members by epoxy to increase stiffness and member capacity.
FRP materials can be applied at the bottom of beams to increase beam performance for flexural strength, or wrap around columns to increase column performance for compressive strength and same for slab and other structures members.
2.3 Research Significance
Members strengthening by FRP depend on the bond quality of adhesive material (epoxy). An adhesive material (epoxy) is responsible for transferring stress to the members, and concrete members cannot resist high shear stress. However, cracks appear and debonding occurring in the region of high shear stress which is usually at the end of FRP sheet.
These cracks will cause loss of the connection between FRP and member (concrete or steel), so the member’s stiffness will be lost gradually by increase these cracks due to the increase in interfacial shear stress.
Many researchers studied this case and trying to determine an approximate value for shear stress compared with finite element models and detected the bond which is effected by a surface quality and concrete strength quality (E.Y. Sayed-Ahmed, R. Bakay, N.G. Shrive).
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Concrete compressive strength is a way to control interfacial shear stress which is causing increases or decreasing in interfacial shear stress depends on the concrete quality (Teng et al. 2002), this method is used to modify interfacial stress by changing materials properties.
This research studied method to reduce interfacial shear stress by modifying the surface, and material properties then compare results with the common way of applying epoxy with FRP.
2.4 Objectives
This research is studying interfacial shear stress for strengthened members by FRP materials to investigate the method for reducing stresses. That will achieve members to resist high load, which occurs high performance for structure, for this purpose three methods have been used to reduce interfacial shear stress by modifying a surface of connection between epoxy and concrete members, increasing area of connection and using another material besides epoxy to extend FRP performance.
We can get it by investigating failure load of three set of modified blocks, so three phases have been created and investigated:
1. Failure load of each set and compare it with control unmodified set.
2. Investigate the strain of each set and compare it with unmodified control set.
3. Investigate energy dissipation of each set.
4. Studying failure mode of each set and compare it with control set.
5. Investigate failure load of strengthening and strengthen concrete beams.
6. Investigate failure mode of strengthening and strengthening concrete beams.
3


2.5 Scope
This research has main three phases of concrete blocks (prisms) each phase has six categories, each category has five specimens. The first category of phase I represented five unmodified prisms specimens (plane surface).
The second category represented prisms has one groove (20) mm width by (15) mm depth. The third category prisms have two grooves each groove has (20) mm width, (15) mm depth and spacing (70) mm center to center between grooves.
The fourth category has three grooves each grove has (20) mm width by (15) mm depth and spacing (60) mm center to center between grooves.
The fifth category has four grooves each groove has (20) mm width by (15) mm depth and spacing (50) mm center to center between grooves. The sixth category represent prism has five grooves; each groove has (20) mm width by (15) mm depth and spacing (40) mm center to center between grooves.
Phase two also represent six category each category has five specimens,
The first category represents plain surface prisms, the second category represents prism has one U-wraps (15) mm width by (210) mm length, third category represent prism has two U -wrap traps (15) mm width by (210)mm length and spacing (70)mm center to center, fourth category represent prism has three U-wraps (15) mm width by (210)mm length and spacing (60)mm center to center, fifth category represent prism has four U-wraps (15) mm width by (210)mm length and spacing (50)mm center to center and sixth category represent prism has five U-wraps (15) mm width by (210)mm length and spacing (40)mm center to center.
4


Third phase represents six category each category has five specimens, first category represent plain surface prisms, second category represent prism has one layer of SMP material (15) mm width by (50) mm length, third category represent prism has two zones of SMP material each has (15) mm width by (50)mm length and spacing (70)mm center to center, fourth category represent prism has three SMP zones (15) mm width by (50)mm length and spacing (60)mm center to center, fifth category represent prism has four SMP zones (15) mm width by (50)mm length and spacing (50)mm center to center and sixth category represent prism has five SMP zones (15) mm width by (50)mm length and spacing (40)mm center to center. Tension force applied on FRP and studied deboned strength for each category and compare it with control blocks (plain surface) also studied failure mode and energy dissipation.
2.6 Thesis outline
This research has five main chapters each chapter explains part of the investigation as below: Chapter 2: explains literature review of previous researchers related to strengthen members using FRP, concrete blocks(prisms) applying direct shear stress and studying the behavior of unmodified (plain surface prisms) and describing materials properties used in an experimental test.
Chapter 3:
explains details of the experimental procedure of three phases of concrete blocks include blocks preparations, test setup, blocks behavior under direct shear stress, load-displacement behavior, load-strain behavior, strain profile, stress profile and energy dissipation and compare
5


all results with plain surface blocks and discus decreasing in interfacial shear stress by using these technics.
Chapter 4: Investigates set of modified RC beams by using grooves and studying load displacement, load strain, strain in reinforcement bars and discussing these results with strengthening concrete beams.
Chapter 5: explains conclusions and some recommendations for future researchers.
6


CHAPTER TWO
LITERATURE REVIEW
2.1 Introduction
This chapter will discuss a method of strengthening structural members (beams) by using FRP material. Also, it will discuss reducing shear stress at the end of beams (near supports) and explain used materials properties; cement, FRP types, purposes, and installation method. Another kind of epoxy material (SMP) will illustrate specifications, the purpose of using this type of epoxy. Also, it will discuss failure type in structures with focusing on shear failure and discuss other research related to this kind of failure.
Finally, it will discuss how this topic leads to improve load carrying capacity, displacement and strain by using grooves, U- wrap, and SMP epoxy material.
2.2 Background
The concrete structure is everywhere around cities; concrete is a cheap material and easy to shape. Word “concrete” is Latino word, “concretes” means growing something together. That happens when mix aggregate, sand, cement, and water. So, the result is concrete. Concrete is hard, durable and robust material. Concrete has high resistance to compression and weak in tension. Concrete is mixed with reinforcement bars to increase compression and tension resistance for solving the tension weakness issue.
7


Sometimes it needs high increase tension strength for concrete members in structures, so compression force applied before or after pouring concrete this called “prestressing or pr-tensioning.” All these modifications in concrete members fabrication will improve structure performance.
Structural concrete member is exposing to massive environmental effect such as fire, flood, tornados, freezing, many solutions developed to repair damaged members and structure but still expensive especially for replacing. One of the conventional solutions is strengthening concrete members by high resistance material specification such as epoxy and FRP. It is good for saving time, cost and increase structure life and performance.
2.3 Fiber Reinforced Polymer (FRP)
2.3.1 Introduction:
One of most excellent choice in the twentieth century in material engineering technology is a fiber reinforced polymer (FRP). This composite material has low weight and high strength. It is anisotropic material, lightweight material, durable material for construction, chemical resistance. FRP is showing high resistance to corrosion, fast cure, high strength resistance, low density, high elastic, low conductivity, low density, high elastic modulus, high workability, high fatigue resistance and high impact resistance (Wang, Dai, & Harries, 2013). Another advantage of using FRP material does not need special tools for applying, just clean the surface and make sure it is dry and glue with the member surface by epoxy.
8


FRP can be applied in any part of a structure, in columns to increase compressive strength, for beams can be used at the bottom to improve flexural strength, for both metal and concrete structures. Though, that will lead increasing in member strength without adding additional weight to foundations.
2.3.2 FRP types
FRP has three types, depending on the method of production, and each one has own specifications, properties, and applying method, these types are: -
1- CFRP: Carbon Fiber Reinforced Polymers, it is carbon-based anisotropic material, and it produced at a high temperature of 1300 C. It has lightweight, high strength, high creep resistance, high resistance to chemical, high elastic modulus beside that, it is brittle material and expensive.
2- GFRP: Glass Fiber Reinforced Polymers. It is glass based isotropic material. It has high strength, and high resistance to water and chemical, the common types of it are C-Glass, E-Glass, and S-Glass.
3- AFRP: Armed Fiber Reinforced Polymers, it has another name “Kevlar fiber,” it is anisotropic material and has high tensile strength, high stiffness, high impact resistance, high modulus, low weight but low compression and more expensive than CFRP & GFRP. It has five types Kevlar-29, Kevlar-49, Kevlar-100, Kevlar-119, Kevlar-129. Table 3-1 is showing the difference between these three types of FRP.
9


2.3.3 FRP Use
The retrofit word means updating exist thing by applying new material after manufacture. That has happened in structure when resisting higher load or exposing to a massive environment like a flood, earth quick, tornados which cause a loss in a member ductility and stiffness. Many materials have been used before to correct members strength and ductility like, installing steel plates on concrete members (Jacket), or using external post-tension; all these techniques improved damaged structure performance.
Steel plate underneath beam is used to increase flexural strength (Fleming and King 1967), but it needs professional tools and technicians for installation, maintenance, so it is expensive. However, the most important thing is adding more load to structure foundation, and these foundations may not designed for these additional weights.
As explained in the previous section FRP is the most common solution for structure retrofit; it is lightweight material, high resistance to corrosion, high strength resistance, and long-term performance.
For rehabilitate, modfy structure strength to resist additional loads for this purpose licensed professional engineer needs evaluating the structure to determine the type of damages (shear, flexural, compression) then determine FRP type, installation method and applying locations. Rating happens after reviewing as-built drawings and determining compressive strength for existing concrete members and corrosion for steel members.
All this information gives evaluator idea about structure performance, and the locations need to retrofit. However, FRP is not applied just to failed members; it may also be used for
10


neighbor’s members (beams or columns) because applying FRP just for the failed member will improve member stiffness and may cause damage in neighbors members.
ACI code 364.1R and ACI437R have a brief description of structural analysis and investigation method.
The adhesives used to glue FRP with concrete members (epoxy), it provides shear resistance between concrete and FRP, epoxy is a common product using to bond FRP with concrete or steel members.
2.4 Epoxy types and specifications
Epoxy is thermosetting polymer contains two groups of materials mix until getting viscosity, so we can use it to fill cracks or bond another material like FRP. All epoxy type has own specifications depend on manufacturer specifications and usually consist of two compounded (hardener and resin) mix together with mixing ration 1:2 or 1:3 and it is left for curing for one to seven days.
In this research will focus on MBrace Saturant 4500 type and specifications as shown in the table (2-2), Mix ratio used (hardener to resin) was 1:3 and curing time seven days, before applying epoxy concrete surface cleaned and dried, hardener and resin mixed carefully until getting homogeneous then used.
All tests that in this research, mixed hardener and resin in ratio 1:3 by volume or weight mixed by special tools until mix get homogeneous.
11


Epoxy is applied on the concrete surface (blocks and beams), then placed FRP sheet, after that put another layer of epoxy above FRP sheet and left for curing for seven days in a shaded, crisp and dry area as shown in tests’ pictures.
2.5 Previous study and research on concrete strengthened by FRP.
2.5.1 Failure mode of Concrete Blocks
Neubauer and Rostasy, 1997; Chen and Teng; 2001), mentioned in their papers that they are many failure load types.
The frequent failure is called (interfacial bond) as shown in (Figure 2-1, A); failure happened when debonding occurs between epoxy and concrete, sometimes crack propagates at the end of the block due to high tension force and causes a separate part of concrete from a block.
The second type of failure called (tension shear failure ) as shown in (figure 2-1, B). This occurs at the back end of FRP when epoxy layer too thick; this type of failure, not an ordinary happening.
The third type of failure leads to damage in FRP due to a high bond between epoxy, FRP, and concrete called (FRP rupture or damage) as shown in (Figure2-1, C).
12


FRP
EPOXY
M •• • '
1 Cqncfctc Prism
(A)
FRP
^=5
(C)
EPOXY
r7"
1 CQncj’etc Prism
F
(D)
Figure 2-1: Failure Mode in concrete blocks
2.5.2 Mechanism of bond transfer from FRP to concrete
When applying a tension force to FRP glued with epoxy to a fixed block, strain in the adhesive will follow applied load and increase gradually with the increasing load (E. Y.
13


Sayed-Ahmed, R. Bakay, N.G. Shrive2009). As shown in (Fig 2-1, D), strain keeps raising until reach concrete maximum strain value. When strain exceeds maximum concrete strain value, crack debonding occurs at the end of the block from force side.
By the increasing load, strain keeps increasing until debonding occur between epoxy and concrete block because strain exceeds maximum strain value for concrete and epoxy. According to (J.G. Teng, H. Yuan, J.F. Chen 2006) failure pass in three stages: -
1- Elastic stage: occurs when applying load is small and interface stress in elastic mode and lower than max interface stress.
2- Soften stage: occurs when applying load increases and interface stress equal to max interface stress.
3- Debond Stage: occurs when applying load increases and interface stress exceeds maximum interface stress, debonding happen between epoxy and concrete due to high interface stress and strain.
2.5.3 Behavior of structure members strengthened by FRP
Many researchers studied the mechanism of CFRP bonded to concrete and retrofit failed RC members by using CFRP, Taljsten, B. (1997) discussed strengthening method for RC members by FRP with epoxy adhesive and the improvement in strength and stiffness for concrete members. Also, they focused on the minimum anchor length of a plate that is needed to transfer stress from steel and concrete.
14


For this purpose, researcher studied strain behavior for two categories (16 steel beam and four RC beams).
For steel beam, they focused on the strength of beams strengthening by various CFRP length and width (length various from 100-800mm, and width various from 40-80mm) with constant thickness 2.9mm.
The failure mode for concrete beams was cracking and peeling off for FRP and steel category, was the extension in steel before failure.
Also, they discussed the strain behavior comparing with anchor length (Lc), results showed increased in load carrying when increase anchor length plus more safety for structure for steel beam category.
For the concrete beam, category prepared four beams with the various length of anchoring (100-400mm) with constant width and thickness, 50mm and 1.5 mm respectively.
Failure mode was not yielded or abruptly failure, also results showing RC beams have extended anchor length stiffer than RC beam have shorter anchor length.
(Ebead, U. A., Neale, K. W., & Bizindavyi, L. 2004, December) studied mechanism of fiber reinforced polymer and interface stress effect of bond FRP, adhesive and concrete surface. From the conclusion of this research and other researchers related to this topic, conclude the debonding laminate and FRP from the concrete surface depends on below conditions: a- Bond stress depend on tensile strength for concrete (Triantafillou and Plevris 1992) b- Flexural rigidity for laminate layer (Triantafillou and Plevris 1992) c- Concrete surface properties (Van Gemertl980) d- Thickness of adhesive.
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Also, they explained the separation of FRP sheet happened for high shear strength in adhesive cause cracks then separation.
Increasing or decreasing in bond strength depends on concrete strength itself and surface preparation, the authors improved that by finite element models.
For comparison with analytical results, concrete blocks prepared with various lengths of adhesive and FRP sheet, and it applied peeling force at the free end of FRP, strain measured at different locations on adhesive.
The authors concluded the strain decrease along adhesive layer, and this performs applied for force transfer from FRP to epoxy then to concrete.
2.5.4 Failure mode of RC members strengthened by FRP
(Ritchie st al. 1991: saastmanesh and Ehsani 1991) mentioned that the failure mode depends on the duration of strengthened material progress in a test, and this could be divided into two categories:
First, strengthen material still active until reaching ultimate load, failure happening depends on beam fabrication quality (reinforcement bar amount, a compressive strength of concrete). So, the common failure for this category is crush in concrete or FRP rupture or shear failure. Second, strength material fails before reaching ultimate strength and common failure happens interface debonding between epoxy and concrete.as shown in Fig (2-2).
(Sharif et al.1994) studied failure mode with laminate thickness, thin laminate bonded to RC beam failure occurred in FRP rupture, increasing laminate thickness lead to interface
16


debonding or FRP peel off from the terminated end, and common failure happened at the end of the beam (near support).
To avoid FRP peeling off from end many solutions used like anchored bolt for FRP end or U shape steel plate applied at the end of FRP this will increase shear strength 150% than beams without anchored (Sayed-Ahmed, E. Y.2009).
(Ross et al. 1999) Mentioned the ratio of reinforcement bar amount and cross section area would affect the failure load. Increasing ratio of reinforcement bar lead to failure move to compression zone, and shear crack will propagate between laminate and reinforcement bars, The Author concludes the displacement in mid-span of the beam with the higher reinforcement ratio is lower than the beam with the light ratio of reinforcement bar. So, the beams have light reinforcement ratio failure occurs in laminate and increase in displacement in mid-span of the beam.
17


Concrete crushing
a)


FRP rapture
d)
Debonding
e)


-Lfc.
AA
Crack propagation/debonding
1
f) g)
Crack propagation/debonding Crack propagation/debonding
Figure 2-2: (a) Flexure failure by FRP rupture, (b) Flexure failure by concrete crushing, (c) shear failure, (d) concrete cover separation, (e) plate-end interfacial debonding, (f) flexure crack -induced in interfacial debonding, (g) critical diagonal crack-induced interfacial debonding
Source: Sayed-Ahmed, E. Y., Bakay, R., & Shrive, N. G. (2009). Bond strength of FRP laminates to concrete: a state-of-the-art review. Electronic Journal of structural engineering, 9(1), 45-61.
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Table 0-1: FRP types and properties
FRP types Specific gravity Tensile Modulus of
(gr/cm3) Strength elasticity
(N/mm2) (N/mm2)
CFRP 1.75 3100 220000
GFRP 2.54 2410 70000
AFRP 1.46 3600 124000
Table 2-2: Epoxy Physical Properties
Tensile Properties
Density 6.13 Pcf (983-kg/m3)
Yield Strength 7900 psi (54 Mpa)
Strain at Yield 2.5%
Elastic Modulus 440 ksi (3034 Mpa)
Ultimate strength 8000 psi (55.2 Mpa)
Rupture Strain: 3.5%
Poisson’s Ratio 0.40
Compressive Properties
Yield Strength 1200 psi (138 Mpa)
Strain at Yield 3.8%
Elastic Modulus 540 ksi (3724 Mpa)
Ultimate Strength 20000 psi (138 Mpa)
Rupture Strain 5%
Functional Properties
CTE 20*10 -6/F
Thermal Conductivity 1.45 Btu.in/hr.ft2
Glass Transition Temp, Tg 3 71C)
19


CHAPTER THREE
BEHAVIOR OF CONCRETE BLOCKS STRENGTHENED WITH FRP SHEETS
SUBJECTED TO TENSION
3.1 General overview
The experimental tests used to investigate concrete blocks (prisms) bounded with FRP sheet behavior after applying a tension force to the free end of FRP, epoxy exposed to shear stress due to tension force.
To study shear force effect on epoxy, and the best option to reduce the shear force, three phases have been created. Each phase has five categories, and each category has five specimens. This chapter will describe all experimental work related to this research; next section 3.2 will describe experimental program and material used to prepare specimens. Also, it will represent test matrix. The three phases will discuss prism behavior on load displacement, strain behavior, Energy dissipation and comparison between each category.
3.2 Experimental program
3.2.1 Test specimens
Total of 95 concrete blocks (prisms) used in research, the blocks made of concrete have compressive strength 18 MPa (3045) Psi and has dimension 300mm (12) in long x 100mm (4) in height x 50mm (2) in width.
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concrete prepared for blocks and poured inside molds has dimensions 300mm (12) in long x 100mm (4) in height and left for curing for 28 days then concrete saw used to cut blocks 50mm (2) in width.
Five blocks strengthened with epoxy and FRP and left seven days for curing, FRP sheet had 431,8mm (17) in length and 50 mm (2) in width placed on each block, results for these blocks used as control data to compare it with other blocks as follows:
1- Five blocks made with one groove had dimension 50 mm (2) in length and 20 mm
(0.78) in width with 15 mm (0.59) in depth, these grooves filled out with epoxy.
2- Five blocks made with two grooves had dimension 50 mm (2) in length, and 20 mm
(0.78) in width with 15 mm (0.59) in depth, 70mm center to center spacing between grooves, these grooves filled out with epoxy.
3- Five blocks made with three grooves had dimension 50 mm (2) in length and 20 mm
(0.78) in width with 15 mm (0.59) in depth with spacing 60mm center to center between grooves.
4- Five blocks made with four grooves had dimension 50 mm (2) in length and 20 mm
(0.78) in width with 15 mm (0.59) in depth with spacing 50mm center to center between grooves.
5- Five blocks made with five grooves had dimension 50 mm (2) in length and 20 mm
(0.78) in width with 15 mm (0.59) in depth with spacing 40mm center to center between grooves. As shown in figures (3-1,3-7,3-13,3-19).
Other 25 blocks had the plain surface but applied U wrap had 210 mm (5.1) in length, and 20 mm (078) in width applied at the locations of grooves.
21


Five specimens one U-wrap prepared and another five specimens had two U-wrap and same for other specimens three U-wrap, four U-Wrap and five U-Wrap as shown in pictures.
Rest of 25 blocks applied SMP material at the location of grooves for each block, first placed epoxy then SMP and left for curing seven days, five blocks for each category prepared, as shown in pictures.
3.2.2 Test setup
Specimens were prepared by gluing FRP sheet to prism by epoxy, then were left seven days for curing then were prepared for a test, the tension force applied by MTS machine with displacement rate 0.3 mm/min, concrete blocks fixed inside a metal frame (fixture).
The fixture set in lower grips of MTS machine and FRP set in upper grips of MTS machine. The first attempt for the test, slipping issue faced from FRP fixing side because FRP sheet is too thin. For solving this problem, two layers of FRP sheets with dimensions 50mm x50mm (2inx2in) were glued to free end of FRP sheet by G-flex epoxy type and left one days for curing to make CFRP sheet thicker so they could hold by MTS grips and solve slipping problem.
Displacement was measured by laser instrument, a special tape was fixed on FRP sheet, and another one was placed on fixed tape on MTS then set up the laser light to be between two tapes.
After making sure all set up correctly, test run by applying displacement force to FRP sheet and waited until specimen failed.
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3.3 Materials
Concrete, epoxy, CFRP, and SMP has been used in all tests as follows:
3.3.1 Concrete
Concrete blocks prepared by using Portland cement, sand, aggregate and water with mix ratio designed according to ACI304R specifications.
Concrete prepared according to mix design shown in table 3-2 with compressive strength 18 MPa at 28 days.
The concrete mixer used for concrete preparation. Concrete mixed and casted in metal forms have dimensions 300mm (12 in) length and 100 mm (4in) width with 100 mm (4 in) depth; concrete left seven days in curing room for curing purpose.
Concrete cylinders poured to determine compressive strength for blocks, results for cylinders shown in table 3-3.
The concrete saw has been used to cut prisms into two blocks; each block has dimension 300mm (12in) length and 50mm (2 in) width with 100mm (4 in) thickness.
3.3.2 Epoxy
Epoxy used to bond FRP sheet with concrete blocks, epoxy consists of two-part hardener and
resin, mixed with ration 1:3 and left for seven days for curing as manufacturer specifications.
Epoxy Density 6.13 pcf (983-kg/m3), Yield Strength 7900 psi (54 MPa), Strain at Yield
2.5%, Elastic Modulus 440 ksi (3034 MPa), Ultimate strength 8000 psi (55.2 MPa), Rupture
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Strain:3.5%, Poisson’s Ratio 0.40, Compressive Properties, Yield Strength 1200 psi (138 MPa), Strain at Yield 3.8%, Elastic Modulus 540 ksi(3724 MPa), Ultimate Strength20000 psi (138 MPa), Rupture Strain 5%, Functional Properties CTE 20*10 -6/F, Thermal Conductivity 1.45 Btu.in/hr.ft2, Glass Transition Temp, Tgl63 F(71C)
Blocks cleaned by grinder to remove dust and left in oven for five minutes to make sure blocks are dry.
3.3.3 SMP
Silyl Modified Polymer (SMP) is used for bonding and sealing metal, aluminum frames and joint filler for roofs and floors because of fast curing and resistance to UV, it is just one part and low curing time, other technical data showing in the table (3-1).
SMP reduces energy then causes reducing load and increasing in displacement, SMP may dissipate applied energy before transfer to FRP (Kim, Y. J., LaBere, J., & Yoshitake)
3.3.4 FRP
FRP sheet used in all tests, FRP was cut in dimension 50 mm (2 in) width and 430mm (17 in) length and glued to concrete blocks by epoxy.
Epoxy applied to two layers, the first layer applied directly to prism surface and grooves then
FRP sheet applied and another layer of epoxy applied above FRP sheet, for FRP
specification, types, technical data available in section 2.4.3
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3.4 Test Matrix
Three phases used in this section each phase has 25 concrete blocks (prisms) divided as follows:
Phase I: twenty-five total concrete blocks have dimension (300) mm length, and (50) mm width and 100 mm depth, these blocks divided into five categories, each category have five blocks.
The first category has five blocks with one groove in the surface, groove dimension 50mm length and 20 mm width, 15 mm depth.
The second category has five blocks with two grooves in the surface, groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 70 mm center to center of the groove.
The third category has five blocks with three grooves in the surface, groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 60 mm center to center of the groove.
The fourth category has five blocks with four grooves in the surface, groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 50 mm center to center of the groove.
The fifth category has five blocks with five grooves in the surface, groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 40 mm center to center of the groove.
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Phase II: twenty-five total concrete blocks have dimension (300) mm length, and (50) mm width and 100 mm depth, these blocks divided into five categories, each category have five blocks.
The first category has five blocks with one U-wrap around three sides of the block, Unwrap dimension 210mm length and 20 mm width.
The second category has five blocks with two U-wrap around three sides of the block, Unwrap dimension 210mm length and 20 mm width, and spacing 70mm center to center.
The third category has five blocks with three Unwrap around three sides of the block, Unwrap dimension 210mm length and 20 mm width, and spacing 60mm center to center.
The fourth category has five blocks with four U-wrap around three sides of the block, U-wrap dimension 210mm length and 20 mm width, and spacing 50mm center to center. The fifth category has five blocks with four U-wrap around three sides of the block, U-wrap dimension 210mm length and 20 mm width, and spacing 40mm center to center. Phase III: twenty-five total concrete blocks have dimension (300) mm length, and (50) mm width and 100 mm depth, these blocks divided into five categories, each category have five blocks.
The first category has five blocks with one SMP layer in the surface, SMP dimension 50mm length and 20 mm width, and has same epoxy thickness.
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The second category has five blocks with two SMP layer in the surface, SMP dimension 50mm length and 20 mm width, with spacing 70mm center to center between two SMP layers and has same epoxy thickness.
The third category has five blocks with three SMP layer in the surface, SMP dimension 50mm length and 20 mm width, with spacing 60mm center to center between each SMP layers and has same epoxy thickness.
The fourth category has five blocks with four SMP layer in the surface, SMP dimension 50mm length and 20 mm width, with spacing 50mm center to center between each SMP layers and has same epoxy thickness.
The fifth category has five blocks with five SMP layer in the surface, SMP dimension 50mm length and 20 mm width, with spacing 40mm center to center between each SMP layers and has same epoxy thickness.
3.5 Test result of specimens with grooves
In this section will discuss test result observed from experimental work for concrete blocks have parodic grooves and strengthened by CFRP, result output will be focused on load-displacement, load-strain behavior, failure mode and will illustrate how the number of grooves reduced strain value in epoxy, also it will illustrate energy dissipation for each category.
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Each phase grouped into six categories as explained in test matrix above and results in Table (3-4), same test setup used for each category, tension force from MTS machine and displacement measurement by laser extensometer.
3.5.1 Load-carrying capacity
The load carrying obtained from test result for each category as shown in Table3-4 and Table 3-5. For first category (COT) specimens without grooves average of failure load was 5.99 kN (1.34) kip, standard deviation 0.68 and coefficient of variation 0.11, this category used for all other phases just to figure out groove effectiveness on load carrying development for each category.
First category PG1 (prism has one groove) showing increasing in load carrying capacity, five blocks tested an average of failed load was 9.03 kN (2.01 kip), standard deviation 1.03 and coefficient of variation 0.11, groove performed increasing ratio in load carrying capacity 50.75% , second category PG2 (prism has two periodic grooves) showing more increasing in load carrying capacity as well, five specimens failed in average load 9.84 kN (2.21)kip standard deviation (1.07) and coefficient of variation 0.11, that’s mean add two grooves will perform increasing in load carrying capacity ratio 64.27% comparing with COT category. Third category PG3 (prisms have three periodic grooves) five specimens failed in average load 10.27 KN (2.29 kip), standard deviation (1.07) and coefficient of variation (0.1) which is mean if add three grooves performed increasing in load carrying capacity ratio 71.45% comparing with COT category.
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Fourth category PG4 (prisms have four periodic grooves) five specimens failed in average load 10.35 Kn (2.32kip), standard deviation 0.97 and coefficient of variation 0.09, that is meaning add four grooves will perform load carrying capacity 72.78% comparing with COT category.
Fifth category PG5 (prisms have five periodic grooves) five specimens failed in average load 10.63 Kn (2.38 kip), standard deviation 1.67 and coefficient of variation 0.16, that is mean add five grooves will perform load carrying capacity 77.4% comparing with COT category. To reflect this improvement in CFRP load carrying capacity in construction filed, for grooves can create it in steel cover zone for beams, one side of grooves must cover with duct tape then epoxy inject in grooves after fix CRRP sheet.
3.5.2 Load-displacement behavior
The displacement of all specimens measured by using laser extensometer instrument by fixed two tapes and adjust laser light to be between two tapes level. Device leveled carefully to make sure laser light perpendicular on the prism and between two tape range.
For first category COT (prism have plain surfaces without grooves) as shown in Figures (3-2), (3-5). Test results are showing load increasing linearly with displacement because it is brittle material and average displacement 0.07 mm, (0.0029 in).
For second category PG1 (prisms have one groove) showing load increasing linearly with displacement as shown in Figures (3-6) and (3-8), figures showing a semi-linear relationship between load and displacement that is happened for some slipping in the free end of CFRP.
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While the test progress, sometimes some crack occurred in the top of the prism which caused elongation in CFRP sheet and MTS spent time until CFRP tide again.
Third category PG2 (prism has two grooves) Figures (3-9) to (3-12) showing a linear increase in load vs. displacement. At load range 4.5 kN to 7.5 kN happened abrupt load-drop in test progress that occurred for a crack in blocks from applied tension force side. The cracks happened in the free end of prism and grooves location due to high tension force applied, average displacement for five prisms 0.18 mm (0.007) in, this same test behavior for all other categories.
3.5.3 Strain behavior of blocks has grooves
Five strain gauges have been prepared and glued to prisms with spacing 25.4 mm (1 in) center to center, and 50 mm (2in) away from the free end of blocks. Blocks installed inside the metal fixture and fixed in MTS machine applied displacement force in rate 0.3 mm/min. Laser extensometer used to obtain displacement, data acquisition device, and load cell used to obtain strain values. Figures (3-30a,b,c) are showing a comparison between five categories in strain behavior in load range 2,4,6 and 8 KN, strain for COT prisms shows high strain value especially for ultimate applied load, this performs that grooves in prisms reduced strain values. In another trend showing strain in COT prism for load range 4 and 2 Kn, seems lower than another category that’s happened for the difference in epoxy thickness at locations of strain gauges or difference in strain gauges alignment, or small difference in strain gauges locations spacing.
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3.5.4 Failure Mode
First category COT concrete blocks failed when the applied load achieved maximum strain in epoxy and exceed maximum values of strain in concrete. Cracks happened in epoxy interface layer and debonding lost between FRP sheet and concrete surface, debonding happened in FRP sheet and epoxy which causes separation of FRP from concrete block surface as shown in test pictures.
Other categories failed in two different modes:
FRP rupture happened because the existing grooves in concrete surface reduced the strain in epoxy layer, which means epoxy layer can resist more load comparing with COT category, so when applied load exceed ultimate strength for FRP sheet, rupture in FRP sheet occurred
Hairline cracks and FRP rupture. Hairline cracks propagated in the concrete block from applied tension force side, and grooves location. It means strain at these zones exceeds max strain for concrete.
3.5.5 Energy dissipation
Energy dissipation obtained from experiment test, Figures (3-31) are showing energy dissipation for each category. It is showing energy dissipation for five grooves blocks (PG5) is (1.61 kN.mm), then it is higher than other categories, this performs creating grooves in the concrete surface will reduce strain and increasing in applying force.
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3.6 Test result specimens with U-wrap
This section will discuss test result of experimental work for concrete blocks have parodic FRP U-wrap glued over FRP sheet, FRP sheet glued by epoxy to concrete blocks, results data had been focused on load-displacement, load-strain behavior, energy dissipation and failure mode. Will discuss how increasing numbers of U-wrap reduced strain value in epoxy and effect on failure mode for each category.
This phase specimen grouped into six categories as explained in test matrix above and test results in Table 3-6, same test setup used for all categories, tension force from MTS machine, displacement measurement by laser extensometer and strain gauges glued for one specimen from each category to study strain behavior.
3.6.1 Load-carrying capacity
The load carrying gained from test result for each category shown in Table3-6 and Table 3-7. For first category (COT) specimens without U-wrap average of failure load was 5.99 KN (1.34 kip), standard deviation 0.68 and coefficient of variation 0.11, this category used for all other categories just to figure out U-wrap effectiveness on load carrying development for each category. First category P1U (prism has one U-wrap) is showing increases in load carrying capacity; five blocks tested an average of a failed load was 9.65 KN (2.16kip), standard deviation 1.25 and coefficient of variation 0.13, U-wrap performed increasing in load carrying capacity ratio 61.1%.Second category P2U (prism has two periodic U-wrap) showing more increasing in load carrying capacity as well, five specimens failed in average
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load 9.71 KN (2.18kip) standard deviation (0.95) and coefficient of variation 0.09. That is mean adding two U-wrap will perform increasing in load carrying capacity ratio 62.1% comparing with COT category. Third category P3U (prisms have three periodic U-wrap) five specimens failed in average load 9.83 kN (2.19 kip), standard deviation (0.92) and coefficient of variation (0.09) which is mean if add three U-wrap performed increasing in load carrying capacity ratio 64.1% comparing with COT category. Fourth category P4U (prism have four periodic U-wrap) five specimens failed in average load 10.03(2.25 kip), standard deviation (1.08) and coefficient of variation 0.11, that’s mean if add four U-wrap will perform increasing in load carrying capacity ratio 67.4% comparing with COT category. Fifth category P5U (prisms have five U-wrap categories) five specimens failed in average load 10.12 kN (2.27 kip), standard deviation 0.98 and coefficient of variation 0.10, that’s mean adding five U-wrap will perform load carrying capacity 68.9% comparing with COT category.
3.6.2 Load-displacement behavior
The displacement for all specimens measured by using laser extensometer instrument by fixed two special tapes and adjust laser light to be between two tapes level, instrument leveled carefully to make sure laser light perpendicular on the prism and between two tape range.
For COT category already discussed in section 3.5.2
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For first category P1U (prisms have one U-wrap) showing load increasing linearly with displacement as shown in Figure (3-32) to (3-35), Figures showing the semi linear relationship between load and displacement that happened for some slipping in the free end of FRP wile test progress.
Second categoryP2U (prism has two U-wrap) Figures (3-36), and (3-39) showing a linear increase in load vs. displacement. In load range 4 kN to 7 kN happened abrupt load-drop in test progress that occurred for a crack in blocks from applied tension force side, cracks happened in the free end of prism due to high tension force applied or debonding happened in some U-wrap.
The average of displacement for five prisms 0.13 mm (0.0052 in).
This behavior is same for all other categories.
3.6.3 Strain behavior of blocks
Five strain gauges have been prepared and glued on prism for each category; strain gauges spaced 25.4 mm (1 in) from center to center, and 50 mm (2in) away from the free end of blocks.
Blocks installed inside the metal fixture and fixed in MTS machine and applied displacement force in rate 0.3 mm/min; laser extensometer used to obtain displacement, data acquisition device, load cell used to obtain strain values. Figures (3-54 a,b,c ) are showing strain values for each category. The shaded area represents U-wrap location and showing the
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high value of strain comparing with other gauges, that’s happened because of strain gauge record strain from two side, first strain due to tension force from MTS machine, and second strain from u-wrap this just for strain gauges glued directly over U-wrap.
So for this phase, it is unable to compare strain between categories because strain varies for each category especially when strain gauge glued over U-wrap, for example, strain gauge #3 in category P4U glued over 2nd U-wrap and same strain gauge -#3- in category P2U glued over FRP sheet.
3.6.4 Energy dissipation behavior
Energy dissipation obtained from experiment test. Figures (3-55) are showing energy dissipation for each category. It is showing energy dissipation for each category. This happened because some specimens failed with low load and high displacement and other failed with high load and low displacement.
3.6.5 Failure Mode
First category COT failure behavior already discussed in section 3.5.4. Other categories failed in two different modes:
FRP rupture, this occurred because U-wrap distributes the shear stress over U-wrap zone that reduced interfacial shear stress and the applied load exceed ultimate strength for FRP, so it failed in FRP rupture. Debonding, some prisms failed by debonding that happens because of weakness in the bonding of U-wrap with prisms.
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3.7 Test result of specimens with SMP
For this phase summary results of experimental work showed in the table (3-8) & (3-9) for concrete blocks strengthened by FRP and two type of epoxy MBRACE 4500 and SMP.
Will discuss the effect of SMP on load carrying capacity, load displacement, strain behavior and energy dissipation.
3.7.1 Load -carrying capacity
The load carrying test result is shown in Tables 3-8 and Table 3-9. For category COT (specimens without SMP), the average of failure load was 5.99 kN(1.34 kip), the standard deviation was 0.68 and coefficient of variation was 0.11, this category used for all other categories just to figure out SMP effectiveness on load carrying development for each category.
First category PIS (prism has one layer of SMP) is showing decreasing in load carrying capacity. Five prisms tested and the average of failure load was 5.79 kN (1.29kip), the standard deviation was 0.51 and coefficient of variation was 0.09, SMP performed a decreasing ratio in load carrying capacity of 3.3%. Second category P2S (prism has two periodic SMP layers) showing more decreasing in load carrying capacity. As well, five specimens failed in an average load of 5.64 kN (1.26kip), standard deviation (0.37) and coefficient of variation 0.06, that’s mean adding two layers of SMP will perform decreasing in load carrying a capacity ratio of 5.85% in comparing with COT category.
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Third category P3S (prisms have three periodic SMP layers). Five specimens failed in average load 6.38 kN (1.4 kips), standard deviation (0.81) and coefficient of variation (0.13) which means adding three layers of SMP will perform increasing in load carrying a capacity ratio of 6.5% in comparing with COT category.
Fourth category P4S (prism have four periodic SMP layers). Five specimens failed in an average load of 5.40 (1.2 kips), standard deviation (0.63) and coefficient of variation 0.12, that is mean adding four of SMP will perform decreasing in load carrying a capacity ratio of 9.84% in comparing with COT category.
Fifth category P5S (prisms have five SMP layers). Five specimens failed in an average load of 5.27 kN (1.18 kip), standard deviation 0.70 and coefficient of variation 0.13, that’s mean adding five SMP layers will perform decreasing in load carrying capacity of 12% in comparing with COT category.
3.7.2 Load-displacement behavior
As discussed in part 3.5.2 and 3.6.2 about measuring load displacement, all categories showed a linear relationship between applying load and displacement for the epoxy zone. When interface failure due to increases in applying load interface a resistance, it moves to next zone SMP, and it is known SMP reduce energy. So, the prism cannot resist high value of applying the load, and abrupt load-drop happened in SMP zone until reaching the next epoxy zone, and linear behavior performs again between load and displacement as shown in Figure
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showing stepwise behavior.And, this is the same mechanism happened with all other categories.
3.7.3 Strain behavior of concrete Blocks strengthened by epoxy and SMP
Five strain gauges have been prepared and glued on FRP for each category. Strain gauges spaced 25.4 mm (1 in) center to center and 50 mm (2in) away from the free end of blocks. The blocks installed inside a metal fixture and fixed in MTS machine and applied a displacement force in rate 0.3 mm/min; laser extensometer used to obtain displacement, data acquisition device, load cell used to obtain strain values, Figures (3-76a,b,c ) showing strain values for each category. The shaded area represents SMP zone, cannot do a comparison between strain improvement of each category because strain gauges lay on the epoxy layer in some category and lay on SMP layer in other categories, but according to (Kim, Y. J., LaBere, J., & Yoshitake, I. (2013) strain gauges results consider in an acceptable range.
3.7.4 Energy dissipation behavior
Figure 3-77 is showing energy dissipation for each category; it shows performance in energy dissipation for developing in displacement due to add SMP layers.
Energy dissipation for PIS category (0.31) kN.mm, P2S category (0.3) kn.mm P3S category (0.58) kN.mm, P4S category (0.4) kN.mm and P5S (049) KN.mm comparing with COT category (0.21) kN.mm
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3.7.5 Failure mode
All the five categories failed in debonding of FRP sheet from concrete surface, and some specimens debonding occurred but FRP sheet keeps stick to SMP layer because SMP it silyl material. Debonding happened in the epoxy layer and epoxy separated from concrete block surface, but SMP layer keep glued to concrete block as shown in the attached pictures.
3.8 Results and discussion
If Compare all phases with control category (plan surface category), all phases showed improvement (increasing or decreasing) in comparing with COT category. However, this section will compare between each phase in load carrying capacity, energy dissipation and failure mode. Load carrying capacity in according to Fig (3-78) showing approximately same improvement for grooves phase with U-wrap Phase, grooves and U-wrap showed increasing in load carrying capacity compared with COT category.
However, SMP phase showed decreasing in load carrying capacity 4.9% for SMP reduce energy specification as explained in SMP properties in section 3.3.3.
Strain behavior as mentioned in section 3.5.3,3.6.3& 3.7.3 could not compare between categories and phases for a location of strain gauges on U- wrap and SMP, which cause varies in strain behavior due to changing in material properties and dimensions.
This comparison was needed it to determine beams plan, so energy dissipation compression made, as shown in Fig (3-79) grooves improve energy dissipation comparing with COT
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category, while U-wrap phase showed the increase in energy dissipation comparing with COT category but lower than the grooves phase.
SMP phase was showing increasing in energy dissipation comparing with COT category.
The failure mode for grooves phase of most prisms failed in debonding and crush or cracks in concrete, as discuss it in section 2.3 failure type depend on the epoxy thickness and concrete quality, the good improvement cracks in concrete appeared before reaching ultimate load, which give some indication when member reach to the critical load.
The failure mode for U-wrap phase of most prisms failed in FRP ruptured, just a few of them failed in FRP ruptured and debonded for weakness in bonding between U-wrap and concrete blocks. Comparing with grooves prisms internal cracks occurred -maybe concrete cracks or damage in epoxy layer- but not physically appeared, while grooves phase cracks physically appeared, which indication member reach to the critical situation, and this advantage point counts to grooves phase. SMP phase all prisms failed in debonding due to damage in an epoxy layer. FRP sheet keeps stick to prism surface for silyl, and massive viscosity of SMP material and this type of combination of epoxy and SMP generate stable bond than epoxy compounded (Kim, Y. J., LaBere, J., & Yoshitake, I. 2013).
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Table 0-1: Technical data for sily modified polymer (SMP)
Curing method Moisture
Specific gravity ca. 1.4 g/ml
Skin forming time Ca. 10 min (20°C/50% R.H.)
Open time < 15 min.* (20°C/50% R.H.)
Curing speed after 24 hrs ca. 3 mm (20°C/50% R.H.)
Shore A hardness ca. 55 (DIN 53505)
Volume change <3% (DIN 52451)
Green strength (max. load which can be applied per m2 ca. 300 Pa (Physica Rheometer MCI00)
Tensile stress (100%) uncured adhesive without sagging) ca. 1.7 MPa (DIN 53504/ISO 37)
Tensile stress at break ca. 2.6 MPa (DIN 53504/ISO 37)
Elongation at break ca. 250% (DIN 53504/ISO 37)
Shear stress ca. 2.5 MPa (DIN 53283/ASTM D1002) (Alu-Alu; adh. thickness 2mm, test speed 50 mm/min.)
Tear propagation ca. 16 N/mm (DIN 53515/ISO 34)
E-Modulus (Type C, test speed 500 mm/min.) (10%) ca. 3.3 MPa (DIN 53504/ISO 37)
Solvent percentage 0%
Isocyanate percentage 0%
Temperature resistance - 40°C till +120°C
Temperature resistance +180°C (max. /2hr)
Application temperature UV- and weather resistance excellent +5°C to +35°C
Colours (standard) white, grey, black
Packaging 290 ml cartridges, 600 ml bags
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Table 0-2: Concert mix design
w/c 45%
Cement(kg/m3) 380
Water (kg/m3) 205
Aggregate (kg/m3) 1200
Sand (kg/m3) 700
Table 0-3: compressive strength results for cylinders at 28 days
Specimen Compressive Stress at 28 days (MPa)
Cl 19.21
C2 18.54
C3 17.82
Average Compressive strength (MPa) 18.52
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Table 0-4: Test results of Prisms withl,2,3,4 and 5 grooves
ID Failure Load kN (Kip) Displacement mm (in) Failure mode
Each kN kip Ave. kN kip Each mm in Ave. mm in
COT-1 6.65 (1.49) 0.06 (0.0023) D
COT-2 6.58 (1.47) 0.05 (0.0019) D
COT-3 6.18 (1.38) 5.99 (1.34) 0.09 (0.0034) 0.07 (0.0029) D
COT-4 5.20 (1.16) 0.07 (0.0029) D
COT-5 5.34 (1.19) 0.10 (0.0038) D
PG1-1 9.18 (2.04) 0.26 (0.0101) C&F
PG1-2 7.76 (1.73) 0.22 (0.0088) C&F
PG1-3 9.25 (2.07) 9.03 (2.01) 0.23 (0.0091) 0.22 (0.0089) C&D
PG1-4 10.51 (2.35) 0.26 (0.0103) F
PG1-5 8.44 (1.89) 0.15 (0.0059) C&D
PG2-1 9.49 (2.12) 0.18 (0.0070) C&F
PG2-2 9.79 (2.20) 0.20 (0.0071) C&F
PG2-3 10.87 (2.44) 9.84 (2.21) 0.20 (0.0071) 0.18 (0.0070) C&F
PG2-4 8.24 (1.85) 0.18 (0.0070) F
PG2-5 10.79 (2.42) 0.16 (0.0062) F
PG3-1 9.74 (2.18) 0.22 (0.0088) F
PG3-2 11.11 (2.48) 0.22 (0.0087) F
PG3-3 8.77 (1.96) 10.27 (2.29) 0.17 (0.0068) 0.19 (0.0076) F
PG3-4 11.43 (2.56) 0.17 (0.0067) C&F
PG3-5 10.30 (2.30) 0.17 (0.0067) C&F
PG4-1 11.27 (2.53) 0.16 (0.0063) C&F
PG4-2 9.55 (2.14) 0.19 (0.0073) F
PG4-3 11.07 (2.48) 10.35 (2.32) 0.23 (0.0111) 0.21 (0.0086) C&F
PG4-4 10.77 (2.42) 0.25 (0.0099) F
PG4-5 9.10 (2.04) 0.21 (0.0083) F
P5G-1 12.84 (2.87) 0.25 (0.0098) C&F
P5G-2 10.22 (2.28) 0.23 (0.009) C&F
P5G-3 11.52 (2.58) 10.63 (2.37) 0.27 (0.0105) 0.27 (0.0105) C&F
P5G-4 10.20 (2.28) 0.29 (0.0113) F
P5G-5 8.37 (1.87) 0.30 (0.012) F
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Table 0-5: Standard deviation and COY for phase I test results
Failure Load
ID kN Kip) Standard Coefficient of
Each Ave. Deviation Variation
kN Kip kN Kip
COT-1 6.65 (1.49)
COT-2 6.58 (1.47)
COT-3 6.18 (1.38) 5.99 (1.34) 0.68 0.11
COT-4 5.20 (1.16)
COT-5 5.34 (1.19)
PG1-1 9.18 (2.04)
PG1-2 7.76 (1.73)
PG1-3 9.25 (2.07) 9.03 (2.01) 1.03 0.11
PG1-4 10.51 (2.35)
PG1-5 8.44 (1.89)
PG2-1 9.49 (2.12)
PG2-2 9.79 (2.20)
PG2-3 10.87 (2.44) 9.84 (2.21) 1.07 0.11
PG2-4 8.24 (1.85)
PG2-5 10.79 (2.42)
PG3-1 9.74 (2.18)
PG3-2 11.11 (2.48)
PG3-3 8.77 (1.96) 10.27 (2.29) 1.07 0.10
PG3-4 11.43 (2.56)
PG3-5 10.30 (2.30)
PG4-1 11.27 (2.53)
PG4-2 9.55 (2.14)
PG4-3 11.07 (2.48) 10.35 (2.32) 0.97 0.09
PG4-4 10.77 (2.42)
PG4-5 9.10 (2.04)
P5G-1 12.84 (2.87)
P5G-2 10.22 (2.28)
P5G-3 11.52 (2.58) 10.63 (2.37) 1.67 0.16
P5G-4 10.20 (2.28)
P5G-5 8.37 (1.87)
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Table 0-6: Test Result for Prisms with 1,2,3,4 and 5 U-wrap
ID Failure Load kN (Kip) Displac mmi ement m) Failure mode
Each Ave. Each Ave.
COT-1 6.65 (1.49) 0.06 (0.0023) D
COT-2 6.58 (1.47) 0.05 (0.0019) D
COT-3 6.18 (1.38) 5.99 (1.34) 0.09 (0.0034) 0.07 (0.0029) D
COT-4 5.20 (1.16) 0.07 (0.0029) D
COT-5 5.34 (1.19) 0.10 (0.0038) D
P1U-1 9.97 (2.24) 0.13 (0.0051) FR
P1U-2 8.60 (1.93) 0.13 (0.0051) FR
P1U-3 8.76 (1.96) 9.65 (2.16) 0.11 (0.0043) 0.13 (0.0052) FR
P1U-4 11.67 (2.62) 0.16 (0.0063) FR
P1U-5 9.24 (2.07) 0.13 (0.0051) FR
P2U-1 8.40 (1.88) 0.15 (0.0059) FR
P2U-2 10.28 (2.31) 0.13 (0.0051) FR
P2U-3 9.10 (2.04) 9.71 (2.18) 0.16 (0.0063) 0.14 (0.0055) FR
P2U-4 10.75 (2.42) 0.14 (0.0055) FR
P2U-5 10.03 (2.25) 0.14 (0.0055) FR
P3U-1 8.73 (1.96) 0.09 (0.0038) FR&DE
P3U-2 9.76 (2.19) 0.09 (0.0034) FR
P3U-3 9.16 (2.05) 9.83 (2.19) 0.09 (0.0038) 0.10 (0.0038) FR
P3U-4 10.72 (2.30) 0.11 (0.0043) FR
P3U-5 10.79 (2.42) 0.10 (0.0038) FR
P4U-1 9.94 (2.23) 0.15 (0.0059) FR
P4U-2 10.26 (2.30) 0.14 (0.0055) FR
P4U-3 8.33 (1.87) 10.03 (2.25) 0.13 (0.0051) 0.15 (0.0058) FR
P4U-4 11.30 (2.54) 0.17 (0.0067) FR
P4U-5 10.30 (2.31) 0.15 (0.0059) FR
P5U-1 10.67 (2.39) 0.13 (0.0051) FR
P5U-2 8.98 (2.01) 0.10 (0.0038) FR
P5U-3 9.20 (2.06) 10.12 (2.27) 0.11 (0.0043) 0.11 (0.0044) FR
P5U-4 11.22 (2.52) 0.12 (0.0047) FR
P5U-5 10.53 (2.36) 0.11 (0.0043) FR
45


Table 0-7: Standard deviation and COY for phase II test results
ID Failun kN 2 Load Kip) Standard Deviation Coefficient of Variation
Each kN Kip Ave. kN Kip
COT-1 COT-2 COT-3 COT-4 COT-5 6.65 (1.49) 6.58 (1.47) 6.18 (1.38) 5.20 (1.16) 5.34 (1.19) 5.99 (1.34) 0.68 0.11
P1U-1 P1U-2 P1U-3 P1U-4 P1U-5 9.97 (2.24) 8.60 (1.93) 8.76 (1.96) 11.67 (2.62) 9.24 (2.07) 9.65 (2.16) 1.25 0.13
P2U-1 P2U-2 P2U-3 P2U-4 P2U-5 8.40 (1.88) 10.28 (2.31) 9.10 (2.04) 10.75 (2.42) 10.03 (2.25) 9.71 (2.18) 0.95 0.09
P3U-1 P3U-2 P3U-3 P3U-4 P3U-5 8.73 (1.96) 9.76 (2.19) 9.16 (2.05) 10.72 (2.30) 10.79 (2.42) 9.83 (2.19) 0.92 0.09
P4U-1 P4U-2 P4U-3 P4U-4 P4U-5 9.94 (2.23) 10.26 (2.30) 8.33 (1.87) 11.30 (2.54) 10.30 (2.31) 10.03 (2.25) 1.08 0.11
P5U-1 P5U-2 P5U-3 P5U-4 P5U-5 10.67 (2.39) 8.98 (2.01) 9.20 (2.06) 11.22 (2.52) 10.53 (2.36) 10.12 (2.27) 0.98 0.10
46


Table 0-8: Test Result for Prisms with 1,2,3,4 and 5 SMP layers
ID Failure Load kN (Kip) Displacement mm (in) Failure mode
Each Ave. Each Ave.
COT-1 6.65 (1.49) 0.06 (0.01) D
COT-2 6.58 (1.47) 0.05 (0.01) D
COT-3 6.18 (1.38) 5.99 (1.34) 0.09 (0.02) 0.07 (0.02) D
COT-4 5.20 (1.16) 0.07 (0.02) D
COT-5 5.34 (1.19) 0.10 (0.02) D
P1S-1 6.23 (1.40) 0.10 (0.02) D
P1S-2 4.94 (1.11) 0.10 (0.02) D
P1S-3 5.80 (1.30) 5.79 (1.29) 0.09 (0.02) 0.10 (0.02) D
P1S-4 5.83 (1.31) 0.10 (0.02) D
P1S-5 6.13 (1.37) 0.10 (0.02) D
P2S-1 5.99 (1.34) 0.12 (0.03) D
P2S-2 5.55 (1.24) 0.10 (0.02) D
P2S-3 5.87 (1.32) 5.64 (1.26) 0.08 (0.02) 0.10 (0.02) D
P2S-4 5.76 (1.29) 0.08 (0.02) D
P2S-5 5.05 (1.13) 0.10 (0.02) D
P3S-1 6.23 (1.40) 0.20 (0.05) D
P3S-2 6.99 (1.57) 0.16 (0.04) D
P3S-3 7.03 (1.58) 6.38 (1.4) 0.15 (0.04) 0.16 (0.04) D
P3S-4 6.58 (1.47) 0.15 (0.04) D
P3S-5 5.06 (1.13) 0.14 (0.03) D
P4S-1 4.90 (1.10) 0.15 (0.04) D
P4S-2 5.46 (1.22) 0.13 (0.03) D
P4S-3 6.26 (1.40) 5.40 (1.2) 0.12 (0.03) 0.14 (0.03) D
P4S-4 5.68 (1.27) 0.15 (0.04) D
P4S-5 4.68 (1.05) 0.14 (0.04) D
P5S-1 5.16 (1.16) 0.08 (0.02) D
P5S-2 4.47 (1.01) 0.16 (0.04) D
P5S-3 6.02 (1.35) 5.27 (1.18) 0.20 (0.05) 0.15 (0.04) D
P5S-4 5.96 (1.33) 0.19 (0.05) D
P5S-5 4.74 (1.06) 0.14 (0.04) D
47


Table 0-9: Standard deviation and COY for phase III test results
ID Failun kN(] 2 Load m Standard Deviation Coefficient of Variation
Each kN Kip kN Ave. Kip
COT-1 6.65 (1.49)
COT-2 6.58 (1.47)
COT-3 6.18 (1.38) 5.99 (1.34) 0.68 0.11
COT-4 5.20 (1.16)
COT-5 5.34 (1.19)
P1S-1 6.23 (1.40)
P1S-2 4.94 (1.11)
P1S-3 5.80 (1.30) 5.79 (1.29) 0.51 0.09
P1S-4 5.83 (1.31)
P1S-5 6.13 (1.37)
P2S-1 5.99 (1.34)
P2S-2 5.55 (1.24)
P2S-3 5.87 (1.32) 5.64 (1.26) 0.37 0.06
P2S-4 5.76 (1.29)
P2S-5 5.05 (1.13)
P3S-1 6.23 (1.40)
P3S-2 6.99 (1.57)
P3S-3 7.03 (1.58) 6.38 (1.4) 0.81 0.13
P3S-4 6.58 (1.47)
P3S-5 5.06 (1.13)
P4S-1 4.90 (1.10)
P4S-2 5.46 (1.22)
P4S-3 6.26 (1.40) 5.40 (1.2) 0.63 0.12
P4S-4 5.68 (1.27)
P4S-5 4.68 (1.05)
P5S-1 5.16 (1.16)
P5S-2 4.47 (1.01)
P5S-3 6.02 (1.35) 5.27 (1.18) 0.70 0.13
P5S-4 5.96 (1.33)
P5S-5 4.74 (1.06)
48


FRP
(A)
FRP
7
Figure 3-l(a) Top view for COT prism detail, (b) side view for COT prism detail, (c) COT prism test setup, (d) COT side view test setup
49


(a)
(b)
Figure 0-2: (a) COT load -displacement test result for prism COT-1, FRP debonding in
6.65kn and displacement 0.06mm, (b) COT load -displacement test result for prism COT-2,
FRP debonding in 6.58kN and displacement 0.05mm
50


Displacement (nun)
(c)
(d)
Figure 0-3:(C) COT load -displacement test result for prism COT-3, FRP debonding in
6.18kn and displacement 0.09mm, (d) COT load -displacement test result for prism COT-4,
FRP debonding in 5.20kn and displacement 0.07mm
51


(e)
(f)
Figure 0-4: (e) COT load -displacement test result for prism COT-5, FRP debonding in 5.34Kn and displacement 0.10mm, (d) COT load-displacement for all COT prisms
52


FRP —
300
'â–  ,r
EPOXY—1 Groove (15x20)inm— Concrete prism —
(a)
Test Fixture—
FRP —

(b)
Figure 3-5: Top view and side view for PG1 prism detail, (b) PG1 prism test setup
53


14 -i
12 -10 -
0.00 0.05 0.10 0.15 0.20 0.25
0.30
Displacement (mm)
PG1-1
0.35 0.40
(a)
(b)
Figure 3-6: (a) load -displacement test result for prism PG1-1, FRP ruptured and hairy cracks appeared in 9.18kn, and displacement 0.26mm (b) load -displacement test result for prism PG1-2, FRP ruptured and hairy cracks appeared in 7.76kn and displacement 0.22mm
54


(a)
(b)
Figure 3-7: (a) load -displacement test result for prism PG1-3, FRP ruptured and hairy
cracks appeared in 9.25kN and displacement 0.23mm (b) load -displacement test result for
prism PG1-4, FRP ruptured in 10.51 and displacement 0.26mm
55


(a)
(b)
Figure 3-8: (a) load -displacement test result for prism PG1-5, FRP debonding and hairy cracks appeared in 8.44 kN and displacement 0.15mm, (b) load -displacement test result for prism for all PG1 prisms
56


(a)
Test Fixture—
FRP —
FRP
EPOXY
(b)
Figure 3-9: (a)Top view and side view of PG2 prism detail, (b) PG2 prism test setup
57


(a)
(b)
Figure 3-10: (a) load -displacement test result for prism PG2-1, FRP ruptured, and hairy
cracks appeared in 9.49 kN, and displacement 0.18 mm (b) load -displacement test result for
prism PG2-2, FRP ruptured and hairy cracks appeared in 9.79 kN and displacement 0.20 mm
58


14
12
10
5? 8
o
Ph 4 2 0
/

.1 f
A A
/ V
*
P2G-3
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Displacement (mm)
(a)
0.40
(b)
Figure 3-11: (a) load -displacement test result for prism PG2-3, FRP ruptured, and hairy
cracks appeared in 10.87kN, and displacement 0.20 mm, (b) load -displacement test result
for prism PG2-4, FRP ruptured in 8.40 kN and displacement 0.18 mm
59


14
12 -10 -
s? 8-
u 6 -
p
o
n, 4 -
/
2 -
0
0.00 0.05 0.10 0.15 0.20 0.25 0.30
Displacement (mm)
P2G-5
0.35 0.40
(a)
(b)
Figure 3-12: (a) load -displacement test result for prism PG2-5, FRP ruptured in 10.79kn and displacement 0.16mm, (b) load -displacement test result for all PG2 prisms
60


FRP — 1 225- 75
—I20!— r 1

= = = :=^=: = :==f= = f = ====3=:=E====::

50
_L
FRP
EPOXY
(b)
Figure 3-13: (a)Top view and side view of PG3 prism detail, (b) PG3 prism test setup
61


(a)
(b)
Figure 3-14: (a) load -displacement test result for prism PG3-1, FRP ruptured in 9.74kn and
displacement 0.22mm, (b) load -displacement test result for prism PG3-2, FRP ruptured in
11.1 lkN and displacement 0.22mm
62


14
12
10
S 8
â– Q 6
W l-J 4
2
0

✓


0.00 0.05 0.10 0.15 0.20 0.25
Displacement (mm)
-----PG3-3
0.30 0.35 0.40
(a)
(b)
Figure 3-15: (a) load -displacement test result for prism PG3-3, FRP ruptured 8.77kN and
displacement 0.17mm, (b) load -displacement test result for prism PG3-4, FRP ruptured and
hairy cracks appeared in 11.43kN and displacement 0.17mm
63


(b)
Figure 3-16: (a) load -displacement test result for prism PG3-5, FRP ruptured, and hairy cracks appeared in 10.30 and displacement 0.17mm, (b) load -displacement test result for all PG3 prism
64


FRP —
,20,
1111111111111111111111

FRP
-t-
1£T
Epoxy — Groove(15x20)m m —
Concrete prism —
(a)
Test Fixture—
FRP
EPOXY
(b)
Figure 3-17: (a)Top view and side view of PG4 prism detail, (b) PG4 prism test setup
65


14
12 -10 -
' 8 -
T3 , g 6 -

/
4 -2 -
/
0

0.00 0.05 0.10 0.15 0.20 0.25 0.30
Displacement (mm)
-----PG4-1
0.35 0.40
(a)
(b)
Figure 3-18: (a) load -displacement test result for prism PG4-1, FRP ruptured, and hairy
cracks appeared in 11.27 kN, and displacement 0.16 mm, (b) load -displacement test result
for PG4-2 prism, FRP ruptured in 9.55 kN and displacement 0.19 mm
66


14
12 -10 -
' 8 -
T3 , g 6 -
4 -2 -
0
X

t
J
0.00 0.05 0.10

0.15 0.20 0.25 0.30
Displacement (mm)
-----PG4-3
0.35 0.40
(a)
(b)
Figure 3-19: (a) load -displacement test result for prism PG4-3, FRP ruptured, and hairy
cracks appeared in 11.07 kN, and displacement 0.23 mm, (b) load -displacement test result
for PG4-4 prism, FRP ruptured in 10.77 kN and displacement 0.25 mm
67


14 n
12 -10 -
(a)
(b)
Figure 3-20: (a) load -displacement test result for prism PG4-5, FRP ruptured in 9.10 kN and displacement 0.21 mm, (b) load -displacement test result for all PG4 prisms
68


FKP
225
;=ai;3==3:;iE;;E:: a==3;;^;;e;=i
:::=i::fc±::t=t::fc=±:±=:t:=l
zzzzzzzzizzzEzzzzzzzzzzzzcz^za
7
100
1
(a)
(b)
Figure 3-21: (a)Top view and side view of PG5 prism detail, (b) PG4 prism test setup
69


14
T3
O
12 -10 -8 -6 -4 -2 -0 -k
..v

Z1
y
y
0.00 0.05 0.10 0.15 0.20 0.25 0.30
Displacement (mm)
PG5-1
0.35 0.40
(a)
0.00 0.05 0.10 0.15 0.20 0.25
Displacement (mm)
0.30
-----PG5-2
0.35 0.40
(b)
Figure 3-22: (a) load -displacement test result for prism PG5-1, FRP ruptured and hairy cracks appeared in 12.84 kN and displacement 0.25 mm, (b) load -displacement test result for PG5-2 prism, FRP ruptured and hairy cracks appeared in 10.22 kN and displacement 0.23 mm
70


(a)
(b)
Figure 3-23: (a) load -displacement test result for prism PG5-3, FRP ruptured, and hairy
cracks appeared in 11.52 kN, and displacement 0.27mm, (b) load -displacement test result for
PG5-4 prism FRP ruptured and hairy cracks appeared in 10.20 kN and displacement 0.29 mm
71


(a)
(b)
Figure 3-24: (a) load -displacement test result for prism PG5-5, FRP ruptured in 8.37 kN and displacement 0.30 mm (b) load -displacement test result for all PG5 prisms
72


FRP —
25 25 25 25 25 25

225
75
G1 G2 G3 G4 G5
50
1
300
25 25 25 25 25 , 25 |
' T 1
G1 G2 G3 G4 G5
100
(a)
(b)
Figure 3-25: (a) strain gauges location for COT, (b) strain gauge location for PG1
73


(a)
p5 25 25 25 25 25 MM
i i i a s* 7 fe4 gj
~r
FRP
100
(b)
Figure 3-26: (a) strain gauges location for PG2, (b) strain gauge location for PG3
74


FRP
25 25 25 25 25 25

75
Gli G2
G3I G4IG3
â–¡ i IZZI !â–¡[
50
(a)
FRP
(b)
Figure 3-27: (a) strain gauges location for PG4, (b) strain gauge location for PG5
75


Load (kN) Load Strain
(a)
Strain
(b)
Figure 3-28: (a)strain gauge result for COT, (b) strain gauge results for PG1
76


Strain
(a)
Strain
(b)
Figure 3-29: (a) strain gauges results for PG2, (b) strain gauge results for PG3
77


Full Text

PAGE 1

DEBONDING CONTROL OF CFRP STRENGTHENED C ONCRETE MEMBERS b y AHMED IBRAHEEM B.S., Metropolita n State University of Denver , 2015 B.S, University of Technology , 2001 A thesis submitted to the Faculty of the Graduate School of the University of Color ado in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering Program 2017

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ii This thesis for the Master of Science degree by A hmed I braheem Has been approved for the Civil Engineering Program by Yail Jimmy Kim, Chair Nien Yin Chang Chengyu Li December 16, 2017

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iii I br a heem Ahmed (M.S., Civil Engineering) Debonding control of CFRP strengthened Concrete Members Thesis directed by Professor Yail Jimmy Kim ABSTRACT An innovative bonding methodology is present ed to preclude the debonding failure of composite sheets adhered to a concrete substrate. Such a problem is typical in composite strengthening for constructed concrete structures because the composite concrete interface fails prior to achieving the full ca pacity of the composite. The hypothesis to be tested is that the grooved surface of concrete filled with an epoxy adhesive can provide a mechanical interlock to the interface so that stepwise failure takes place, rather than abrupt complete debonding of th e sheets. To confirm the hypothesis , an experimental program is conducted with carbon fiber reinforced polymer composite sheets bonded to a concrete block having various numbers of periodic grooves (1 groove to 5 grooves ). Monotonic tension is applied to t he bonded joints to examine strain profiles and failure characteristics. Another interest of the proposed bonding scheme is that stress singularity along the interface is periodically controlled . In the first part of this research 30 blocks (prisms) stren gthen by epoxy and CFRP after modify surface of these blocks by made grooves 20 mm (0.75in) width and 15 mm (0.6in) depth and filled by epoxy with various no of grooves from (1 groove to 5 grooves) another 30 blocks (prisms) strengthen by epoxy and CFRP bu t applied U wraps at locations of grooves, last 30 blocks (prisms) strengthen by epoxy, SMP and CFRP, SMP applied at locations of grooves. The blocks (prisms) with grooves showed high load carrying capacity and high energy dissipation. In the second part o f this research nine beams strengthen with CFRP and epoxy with two categories of grooves (3 groves and Uniform distributed grooves) beams tested after

PAGE 4

iv changing location of first groove from 0 mm (0 in), 50mm (2 in) and 100 mm (4 in) form free end of CFRP s heet. Beams with end groove 0 mm (0 in) from CFRP showed high load carrying capacity. The form and content of this abstract are approved. I recommend its publication. Approved: Yail Jimmy Kim

PAGE 5

v DEDICATION I dedicate this work for my family e specially my wife, my dad, my mother and my kids who support me in my life and encourage me to face all life challenges. Also, dedicate this work all people who support me to complete this research.

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vi ACKNOWLEDGEMENTS This degree is one of my big gest challenging in my l i f e , especially for a person who is responsible of a family and working full time job , it is not easy but not impossible . I would thank all persons who support, advi se, asset, pray for me to reach my goal , also I would thank University of Colorado Denver for giv ing me this opportunity. First, I would thank my advisor Dr. Kim for advising and supporting me, I could not finish this research without his advising and assistance to reviewing my data results, and I would thank him for supporting part of my tuiti on, also I would thank all members in civil engineering department, committee chair and members. Secondly, I would thank my family Mom, Dad, wife and my kids who support me to reach my goal, e specially my Dad and Mom who pray for me, also I would thank the great lady in my life (my wife) , she is always support ing me and encouraging m e to not give up and push me ahead to reach my goal. And , I would thank all my friends who assist me to complete my laboratory work , e specially Ibrahim bumadian, Mohammed Abahi ri, Abdullah Alajmi, and Thushera . Finally, I thank all laboratory members Tom , Jack, Peter, and Christin for assistance and s upporting me to complete experimental work .

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vii TABLE OF CONTENTS 1 . INTRODUCTION ................................ ................................ ................................ ....... 1 1.1 General ................................ ................................ ................................ ....................... 1 1.2 Research Significance ................................ ................................ ................................ . 2 1.3 O bjectives ................................ ................................ ................................ ................... 3 1.4 Scope ................................ ................................ ................................ .......................... 4 1.5 Thesis outline ................................ ................................ ................................ .............. 5 2 LITERATURE REVIEW ................................ ................................ ........................... 7 2.1 Introduction ................................ ................................ ................................ ................ 7 2.2 Background ................................ ................................ ................................ ................. 7 2.3 Fiber Reinforced Polym er (FRP) ................................ ................................ ............... 8 2.3.1 Introduction: ................................ ................................ ................................ ...... 8 2.3.2 FRP types ................................ ................................ ................................ ........... 9 2.3.3 FRP use ................................ ................................ ................................ ............ 10 2.4 Epoxy types and specifications ................................ ................................ ................. 11 2.5 Previous study and research on concrete strengthened by FRP. .............................. 12 2.5.1 Failure mode of Concrete Blocks ................................ ................................ .... 12 2.5.2 Mechanism of bond transfer from FRP to concrete ................................ ........ 13 2.5.3Behavior of structure members strengthened by FRP ................................ ...... 14 2.5.4 Failure mode of RC members strengthened by FRP ................................ ....... 16 3 BEHA VIOR OF CONCRETE BLOCKS STRENGTHENED WITH FRP SHEETS SUBJECTED TO TENSION ................................ ................................ ... 20 3.1 General overview ................................ ................................ ................................ ...... 20 3.2 Experimental program ................................ ................................ .............................. 20 3.2.1 Test specimens ................................ ................................ ................................ . 20

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viii 3.2.2 Test setup ................................ ................................ ................................ ......... 22 3.3 Materials ................................ ................................ ................................ ................... 23 3.3.1 Concrete ................................ ................................ ................................ ........... 23 3.3.2 Epoxy ................................ ................................ ................................ ............... 23 3.3.3 SMP ................................ ................................ ................................ ................. 24 3.3.4 FRP ................................ ................................ ................................ .................. 24 3.4 Test Matrix ................................ ................................ ................................ ............... 25 3.5 Test result of specimens with grooves ................................ ................................ ...... 27 3.5.1 Load carrying capacity ................................ ................................ .................... 28 3.5.2 Load displacement behavior ................................ ................................ ........... 29 3.5.3 Strain behavior of blocks has grooves ................................ ............................. 30 3.5.4 Failure Mode ................................ ................................ ................................ .... 31 3.5.5 Energy dissipation ................................ ................................ ........................... 31 3.6 Test result specimense with U wrap ................................ ................................ ......... 32 3.6.1 Load carrying capacity ................................ ................................ .................... 32 3.6.2 Load displacement behavior ................................ ................................ ............ 33 3.6.3 Strain behavior of blocks ................................ ................................ ................. 34 3.6.4 Energy dissipation behavior ................................ ................................ ............ 35 3.6.5 Failure Mode ................................ ................................ ................................ .... 35 3.7 Test result of specimens with SMP ................................ ................................ .......... 36 3.7.1 Load carrying capacity ................................ ................................ ................... 36 3.7.2 Load displacement behavior ................................ ................................ ........... 37 3.7.3 Strain behavior of concrete Blocks strengthened by epoxy and SMP ............ 38

PAGE 9

ix 3.7.4 Energy dissipation behavior ................................ ................................ ............ 38 3.7.5 Failure mode ................................ ................................ ................................ .... 39 3.8 Results and discussion ................................ ................................ ........................ 39 4 BEHAVIOR OF CFRP STRENGTHENED BEAMS WITH MULTIPLE GROOVES ................................ ................................ ................................ ............... 148 4.1 General Overview ................................ ................................ ................................ 148 4.2 Experimental programme ................................ ................................ .................... 149 4.2.1Test Matrix ................................ ................................ ................................ ..... 149 4.2.2 Materials ................................ ................................ ................................ ........ 150 4.2.3 Beams preparation ................................ ................................ ......................... 150 4.2.4 Test setup ................................ ................................ ................................ ....... 151 4.3 Results and discussion ................................ ................................ ............................ 152 4.3.1 Load carrying capacity ................................ ................................ .................. 152 4.3.2 Failure mode ................................ ................................ ................................ .. 154 4.3.3 Comparison in failure mode for concrete 56 5 Summary and conclusion ................................ ................................ ........................ 200 6 References ................................ ................................ ................................ ................ 205

PAGE 10

x LIST OF TAB LES Table 2 1 : FRP types and properties ................................ ................................ ....................... 19 Table 2 Table 3 1: Technical data for sily Table 3 2 : Concert mix design ................................ ................................ ................................ 42 Table 3 3 : compressive strength results for cylinders at 28 days ................................ ........... 42 Table 3 4 : Test results For Prisms has 1,2,3,4 & 5 Grooves ................................ ..................... 43 Table 3 5 : Standard deviation and COV for phase I test results ................................ ............ 44 Table 3 6 : Test Result for Prisms have 1,2,3,4 and 5 U wrap ................................ ................ 45 Table 3 7 : Standard deviation and COV for phase II test results ................................ ........... 46 Table 3 8 : Test Result for Prisms have 1,2,3,4 and 5 SMP layers ................................ ......... 47 Table 3 9 : Standard deviation and COV for phase III test results ................................ .......... 48 Table 4 1 : Summary Beams Test behavior ................................ ................................ ........... 163 Table 4 2 : Summary beams test results ................................ ................................ ................ 164

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xi LIST OF FIGURES Figure 2 1 : Failure Mode in concrete blocks Figure 2 2 : (a) Flexure failure by FRP rupture, (b) Flexure failure by concrete crushing, (c) shear failure, (d) concrete cover separation, (e) plate end interfacial debonding, (f ) flexure crack induced in interfacial debonding, (g) critical diagonal crack induced interfacial debonding. Figure 3 1(a): Top view for COT prism detail, (b) side view for COT prism detail, (c) COT prism test setup, (d) COT side view test setup Figure 3 2: (a) COT load displacement test result for prism COT 1, FRP debonding in 6.65kn and displacement 0.06mm, (b) COT load displacement test result for prism COT 2, FRP debonding in 6.58kn and displacement 0.05mm Figure 3 3 :(C) COT load displacement tes t result for prism COT 3, FRP debonding in 6.18kn and displacement 0.09mm, (d) COT load displacement test result for prism COT 4, FRP debonding in 5.20kn and displacement 0.07mm Figure 3 4: (e) COT load displacement test result for prism COT 5, FRP debo nding in 5.34Kn and displacement 0.10mm, (d) COT load displacement for all COT prisms Figure 3 5: Top view side view for PG1 prism detail, (b) PG1 prism test setup Figure 3 6: (a) load displacement test result for prism PG1 1, FRP ruptured and hairy cra cks appeared in 9.18kn, and displacement 0.26mm (b) load displacement test result for prism PG1 2, FRP ruptured and hairy cracks appeared in 7.76kn and displacement 0.22mm Figure 3 7: (a) load displacement test result for prism PG1 3, FRP ruptured and h airy cracks appeared in 9.25kN and displacement 0.23mm (b) load displacement test result for prism PG1 4 , FRP ruptured in 10.51 and displacement 0.26mm Figure 3 8: (a) load displacement test result for prism PG1 5, FRP debonding and hairy cracks appeare d in 8.44 kN and displacement 0.15mm, (b) load displacement test result for prism for all PG1 prisms

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xii Figure 3 9: (a ) Top view side and view of PG2 prism detail, (b) PG2 prism test setup Figure 3 10: (a) load displacement test result for prism PG2 1, FR P ruptured, and hairy cracks appeared in 9.49kn, and displacement 0.18mm (b) load displacement test result for prism PG2 2, FRP ruptured and hairy cracks appeared in 9.79kn and displacement 0.20mm Figure 3 11: (a) load displacement test result for pri sm PG2 3, FRP ruptured, and hairy cracks appeared in 10.87kn and displacement 0.20mm, (b) load displacement test result for prism PG2 4, FRP ruptured in 8.40kN and displacement 0.18mm Figure 3 12: (a) load displacement test result for prism PG2 5, FR P ruptured in 10.79kn and displacement 0.16mm, (b) load displacement test result for all PG2 prisms Figure 3 13: (a)Top view and side view of PG3 prism detail, (b) PG3 prism test setup Figure 3 14: (a) load displacement test result for prism PG3 1, FRP ruptured in 9.74kn and displacement 0.22mm, (b) load displacement test result for prism PG3 2, FRP ruptured in 11.11kN and displacement 0.22mm Figure 3 15: ( a) load displacement test result for prism PG3 3, FRP ruptured 8.77kN and displacement 0.17mm, (b) load displacement test result for prism PG3 4, FRP ruptured and hairy cracks appeared in 11.43kN and displacement 0.17mm Figure 3 16 : (a) load displacement test result for prism PG3 5, FRP ruptured, and hairy cracks appeared in 10.30 and displacem ent 0.17mm, (b) load displacement test result for all PG3 prism Figure 3 17: (a)Top view and side view of PG4 prism detail, (b) PG4 prism test setup Figure 3 18 : (a) load displacement test result for prism PG4 1, FRP ruptured, and hairy cracks appeared in 11.27kN and displacement 0.16mm, (b) load displacement test result for PG4 2 prism , FRP ruptured in 9.55 kN and displacement 0.19mm Figure 3 19: (a) load displacement test result for prism PG4 3, FRP ruptured and hairy cracks appeared in 11.07kN an d displacement 0.23mm, (b) load displacement test result for PG4 4 prism , FRP ruptured in 10.77kN and displacement 0.25mm

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xiii Figure 3 20: (a) load displacement test result for prism PG4 5, FRP ruptured in 9.10kn and displacement 0.21mm, (b) load displac ement test result for all PG4 prisms . Figure 3 21: (a) Top view and side view of PG5 prism detail, (b) PG4 prism test setup Figure 3 22: (a) load displacement test result for prism PG5 1, FRP ruptured and hairy cracks appeared in 12.84kN and displacement 0.25mm, (b) load displacement test result for PG5 2 prism , FRP ruptured and hairy cracks appeared in 10.22kN and displacement 0.23mm Figure 3 23: (a) load displacement test result for prism PG5 3, FRP ruptured, and hairy cracks appeared in 11.52 kN, and displacement 0.27mm, (b) load displacement test result for PG5 4 prism FRP ruptured and hairy cracks appeared in 10.20kN and displacement 0.29mm Figure 3 24: (a) load displacement test result for prism PG5 5, FRP ruptured in 8.37kN and displacemen t 0.30mm (b) load displacement test result for all PG5 prisms Figure 3 25: (a) strain gauges location for COT, (b) strain gauge location for PG1 Figure 3 26: (a) strain gauges location for PG2, (b) strain gauge location for PG3 Figure 3 27: (a) strain ga uges location for PG4, (b) strain gauge location for PG5 Figure 3 28: (a) strain gauge result for COT, (b) strain gauge results for PG1 Figure 3 29: (a) strain gauges results for PG2, (b) strain gauge results for PG3 Figure 3 30: (a) strain gauges results for PG4, (b) strain gauge results for PG5 Figure 3 30 a: (a) strain profile for COT prism, (b) strain profile for PG1 prism Figure 3 30 b: (a) strain profile for PG2 prism, (b) strain profile for PG3 prism Figure 3 30C: (a) strain profile for PG4 prism, (b ) strain profile for PG5 prism Figure 3 31: (a) Energy dissipation for COT, (b) Energy dissipation for PG1, (c) Energy dissipation for PG2, (d) Energy dissipation for PG3, (e) Energy dissipation for PG4, (F) Energy dissipation for PG5 Figure 3 32: (a) P1U Top and side view, (b) strain gauge location for P1U

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xiv Figure 3 33 : (a) Load displacement for PIU 1 prism, FRP ruptured in 9.97kn and displacement 0.13mm, (b) Load displacement for P1U 2 prism, FRP ruptured in 8.6kN and displacement 0.13mm Figure 3 34: (a ) Load displacement for PIU 3 prism, FRP ruptured in 8.76kN and displacement 0.11mm (b) Load displacement for P1U 4 prism, FRP ruptured in 11.67kN and displacement 0.16mm Figure 3 35: (a) Load displacement for PIU 5 prism, FRP ruptured in 9.24kn and dis placement 0.13mm (b) Load displacement for all P1U prisms Figure 3 36: (a) Top and side view for P2U prisms, (b) strain gauges locations for P1Uprism Figure 3 37: (a) Load displacement for P2U 1 prism, FRP ruptured in 8.4 kN and displacement 0.15mm (b) L oad displacement for P2U 2 prism, FRP ruptured in 10.28kN and displacement 0.13mm Figure 3 38: (a) Load displacement for P2U 3 prism, FRP ruptured in 9.10kn and displacement 0.16mm (b) Load displacement for P2U 4 prism, FRP ruptured in 10.75kN and displa cement 0.14mm Figure 3 39: (a) Load displacement for P2U 5 prism, FRP ruptured in 10.03kN and displacement 0.14mm (b) Load displacement for all P2U prisms Figure 3 40: (a) Top and side view for P3U prisms, (b) strain gauges location for P3U prisms Figu re 3 41: (a) Load displacement for P3U 1 prism, FRP ruptured and debonding in 8.73kN and displacement 0.09mm (b) Load displacement for P3U 2 prism, FRP ruptured in 9.76kn and displacement 0.09mm Figure 3 42 : (a) Load displacement for P3U 3 prism, FRP ru ptured in 9.16kn and displacement 0.09mm (b) Load displacement for P3U 4 prism , FRP ruptured in 10.72kN and displacement 0.11mm

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xv Figure 3 43 : (a) Load displacement for P3U 5 prism, FRP ruptured in 10.79kn and displacement 0.1mm (b) Load displacement for a ll P3U prisms Figure 3 44 : (a) Top and Side view for P4U prism, (b) strain gauges locations for P4U prism Figure 3 45: (a) Load displacement for P4U 1 prism, FRP ruptured in 9.94kn and displacement 0.13mm (b) Load displacement for P4U 2 prism, FRP rupture d in 10.26kN and displacement 0.14mm Figure 3 46: (a) Load displacement for P4U 3 prism, FRP ruptured in 8.33kN and displacement 0.13mm (b) Load displacement for P4U 4 prism , FRP ruptured in 11.30kN and displacement 0.17mm Figure 3 47: (a) Load displace ment for P4U 5 prism, FRP ruptured in 10.30kn and displacement 0.15mm (b) Load displacement for all P4U prisms Figure 3 48: (a) Top and Side view for P5U prism, (b) strain gauges location for P5U prism Figure 3 49: (a) Load displacement for P5U 1 prism, F RP ruptured in 10.67kN and displacement 0.13mm (b) Load displacement for P5U 2 prism , FRP ruptured in 8.98kn and displacement 0.1mm Figure 3 50: (a) Load displacement for P5U 3 prism, FRP ruptured in 9.20kn and displacement 0.1mm, (b) Load displacement f or P5U 4 prism, FRP ruptured in 11.22kN and displacement 0.12mm Figure 3 51: (a) Load displacement for P5U 5 prism, FRP ruptured in 10.53kN and displacement 0.11mm (b) Load displacement for all P5U prisms Figure 3 52: (a) strain gauges results for P1U, ( b) strain gauge results for P2U Figure 3 53: (a) strain gauges results for P3U, (b) strain gauge results for P4U Figure 3 54: (a) strain gauges results for P5U Figure 3 54A: (a) Strain Profile for COT prism, (b) Strain profile for P1U Prism Figure 3 54B: ( a) Strain Profile for P2U prism, (b) Strain profile for P3U Prism

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xvi Figure 3 54C: (a) Strain Profile for P4U prism, (b) Strain profile for P5U Prism Figure 3 55a: (a) Energy dissipation for COT, (b) Energy dissipation for P1U, (c) Energy dissipation for P2U, (d) Energy dissipation for P3U, (e) Energy dissipation for P4U, (F) Energy dissipation for P5U . Figure 3 55: (a) Top and side view for P1S prisms, (b) strain gauges location for P1S prisms . Figure 3 56: (a) Load displacement for P1S 1 prism, FRP debondin g in 6.23kN and displacement 0.1mm (b) Load displacement for P1S 2 prism, FRP ruptured in 4.94 and displacement 0.10mm Figure 3 57: (a) Load displacement for P1S 3 prism, FRP debonding in 5.8kN and displacement 0.09mm (b) Load displacement for P1S 4 pris m, FRP debonding in 5.73kN and displacement 0.1mm Figure 3 58: (a) Load displacement for P1S 5 prism, FRP debonding in 6.13kN and displacement 0.1mm (b) Load displacement for all P1S prisms Figure 3 59: (a) Top and side view for P2S prisms, (b) strain g auges location for P2S prisms Figure 3 60: (a) Load displacement for P2S 1 prism, FRP, debonding in 5.99kN and displacement 0.12mm (b) Load displacement for P2S 2 prism FRP, debonding in 5.55kN and displacement 0.1mm Figure 3 61: (a) Load displacement fo r P2S 3 prism, FRP debonding in 5.87kN and displacement 0.08mm (b) Load displacement for P2S 4 prism, FRP debonding in 5.76kN and displacement 0.08mm Figure 3 62: (a) Load displacement for P2S 5 prism, FRP debonding in 5.05kN and displacement 0.1mm ( b) L oad displacement for all P2S prisms Figure 3 63: (a) Top and side view for P3S prisms, (b) strain gauges location for P3S prisms Figure 3 64: (a) Load displacement for P3S 1 prism, FRP debonding in 6.23kN and displacement 0.2mm (b) Load displacement for P3S 2 prism, FRP debonding in 6.99kN and displacement 0.16mm

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xvii Figure 3 65: (a) Load displacement for P3S 3 prism, FRP debonding in 7.03kN and displacement 0.15mm (b) Load displacement for P3S 4 prism, FRP debonding in 6.58kN and displacement 0.15mm Fig ure 3 66: (a) Load displacement for P3S 5 prism, FRP debonding in 5.06kN and displacement 0.14mm (b) Load displacement for all P3S prisms . Figure 3 66a: (a) Top and side view for P4S prisms, (b) strain gauges location for P4S prisms Figure 3 67: (a) Load displacement for P4S 1 prism, FRP debonding in 4.90kN and displacement 0.15mm (b) Load displacement for P4S 2 prism , FRP debonding in 5.46kN and displacement 0.13mm Figure 3 68: (a) Load displacement for P4S 3 prism, FRP debonding in 6.26kN and displac ement 0.12mm, (b) Load displacement for P4S 4 prism, FRP debonding in 5.68kN and displacement 0.15mm Figure 3 69: (a) Load displacement for P4S 5 prism, FRP debonding in 4.68 kN and displacement 0.14mm ( b) Load displacement for all P4S prisms Figure 3 70: (a) Top and side view for P5S prisms, (b) strain gauges location for P5S prisms Figure 3 71: (a) Load displacement for P5S 1 prism, FRP debonding in 5.16kN and displacement 0.08mm ( b) Load displacement for P5S 2 prism, FRP debonding in 4.47kN and dis placement 0.16mm Figure 3 72: (a) Load displacement for P5S 3 prism, FRP debonding in 6.02kN and displacement 0.2mm (b) Load displacement for P5S 4 prism, FRP debonding in 5.96kN and displacement 0.19mm Figure 3 73: (a) Load displacement for P5S 5 pris m, FRP debonding in 4.74kN and displacement 0.14mm (b) Load displacement for all P5S prisms Figure 3 74: (a) strain gauges results for P1S, (b) strain gauge results for P2S Figure 3 75: (a) strain gauges results for P3S, (b) strain gauge results for P4S

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xviii F igure 3 76: (a) strain gauges results for P5S Figure 3 76a: (a) Strain Profile for COT prism, (b) Strain profile for P1S Prism Figure 3 76 b : ( a) Strain Profile for P2S prism, (b) Strain profile for P3S Prism Figure 3 76c: (a) Strain Profile for P4S prism, (b) Strain profile for P5S Prism Figure 3 77: (a) Energy dissipation for COT, (b) Energy dissipation for P1S, (c) Energy dissipation for P2S, (d) Energy dissipation for P3S, (e) Energy dissipation for P4S, (F) Energy dissipation for P5S Figure 3 77a: (a) comparing between load carrying for three phases, (b) comparing between Energy dissipation for three phases Figure 3 77b: (a) concrete cylinder test, (b) concrete cylinder test, (c)concrete block grooves Preparation , (d) prism grooves preparation Fi gure 3 78: (a) Gripping Details , (b ) prisms FRP placement, (c) COT failure , ( d) COT prism failure Figure 3 79: (a) PG1 prism failure, (b ) P1G prism failure, (c) PG2 prism failure, (d) PG2 prism failure Figure 3 80 : (a) PG3 Test setup, (b) PG3 prism fai lure, (c) PG3, PG4& PG5 prisms failure, ( d)PG3, PG4, PG5 and COT prisms failure Figure 3 81 : (a)PG5 prism failure, (b)PG5 prism failure, ( c)P1U prism failure, ( d) PIU prism failure Figure 3 82 : (a) P2U prism failure, (b) P2U prism failure, (c) P3U prism failure, (d) P3U prism failure Figure 3 83 : (a) P4U prism failure, (b) P4U Prism failure, (c) P5U prism failure, (d) P5U prism failure Figure 3 84: (a) P1S prism failure, (b) P1S prism failure, (c) P2S prism failure, (d) P2S prism failure

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xix Figure 3 85 : (a) P3S prism failure, (b) P3S prism failure, (c) P4S prism failure, (d) P4S prism failure Figure 3 86: (a), (b), (c ) & (d) P5S prisms failure Figure 4 1: (a) Reinforcement Details for COT beam without FRP, (b) Reinforcement Details for COT beam with F RP and without grooves Figure 4 2 : (a) Reinforcement Details for BG3 0 beam, (b) crack pattern for BG3 2 beam Figure 4 3 : (a) Reinforcement Details for BG3 4 beam with FRP, (b) crack pattern for BDG 0 beam with FRP Figure 4 4 : (a) Reinforcement Detail s for BDG 2 beam with FRP, (b) crack pattern for BDG 4 beam with FRP Figure 4 5 : Beam test Setup Figure 4 6 : (a) Test result COT beam load displacement (b) PI gauges test result for COT beam Figure 4 7 : COT beam failure flexural crack appeared at 10 KN and propagate d Flexural Shear cracks propagate at 30 kN Concrete crush , and beam fail at 47.2 Kn, (e) crack pattern for COT beam. Figure 4 8: (a) Test result COT_CFRP beam load displacement (b) PI gauges test result for COT_CFRP beam Figure 4 9: (a) s train gauge result for COT_CFRP left side, (b) strain gauge result for COT_CFRP right side Figure 4 10 : (a) Strain Gauges profile for COT_CFRP, (b) Crack Pattern for COT_CFRP Figure 4 11 DIC capture for crack propagation in different load level for COT _CFRP Figure 4 12: COT_CFRP beam failure flexural crack appeared at 20 KN and propagate d Flexural Shear cracks propagate at 45 kN Concrete crush , and beam fail at 57.1 kN Figure 4 13: (a) load displacement test result BG3 0 beam (b) PI gauges test resul t for BG3 0 Beam Figure 4 14: (a) strain gauge result for BG3 0 left side, (b) strain gauge result for BG3 0 right side

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xx Figure 4 15: (a) Strain Gauges profile for BG3 0, (b) Crack pattern for BG3 0 Figure 4 16: DIC capture for crack propagation in differe nt load level for BG3 0 Figure 4 17: BG3 0 beam failure flexural crack appeared at 23 KN and propagate d Flexural Shear cracks propagate at 53.9 kN Concrete crush , and beam fail at 64.9 kN F igure 4 18: (a) load displacement result for BG3 2 beam, (b) PI gauges results for BG3 2 Figure 4 19: BG3 2 beam failure flexural crack appeared at 31 KN and propagate d Flexural Shear cracks propagate at 4 9 kN Concrete crush , and beam fail at 64. 27 Kn, (e) Crack pattern for BG3 2 Figure 4 20: (a) load displacement f or BG3 4, (b) PI gauges result for BG3 4 beam Figure 4 21 : (a) strain gauges results for BG3 4 left side, (b) Strain gauge results for BG3 4 right side Figure 4 22: (a) Strain gauge profile for BG3 4, (b) crack pattern for BG3 4 Beam Figure 4 23: DIC ca pture for BG3 4 crack propagation in different load level Figure4 24: BG3 4 beam failure flexural crack appeared at 22 KN and propagate d Flexural Shear cracks propagate at 35 kN Concrete crush , and beam fail at 63. 9 kN Figure 4 25: (a) load displacement for BDG 0, (b) PI gauges result for BDG 0 beam Figure 4 26: (a) Strain gauges results for BDG 0 left side, (b) strain gauges results for BDG 0 right side Figure 4 27: (a) Strain gauges pro file results for BDG 0 , (b) crack pattern for BDG 0 beam Figure 4 28: DIC capture for crack propagation in different load level for BDG 0 Figure 4 29: BDG 0 beam failure flexural crack appeared at 29.2 KN and propagate d , Flexural Shear cracks propagate at 61.2 kN Concrete crush , and beam fail at 72.1 kN Figure 4 30: (a) Load displacement for BDG 2, (B) PI Gauge results for BDG 2 Figure 4 31: (a) Strain gauge results for BDG 2 Left side, (b) Strain gauge results for BDG 2 right side Figure 4 32: (a) strain gauge profile result for BDG 2 beam, (b) Crack pattern f or BD G 2 Figure 4 33: DIC capture for crack propagation in different load level for BDG 2

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xxi Figure 4 34: BDG 2 beam failure flexural crack appeared at 25 KN and propagate d , Flexural Shear cracks propagate at 61.0 kN Concrete crush and beam fail ed at 69.8 kN Fi gure 4 35: Load displacement results for BDG 4, (b) PI gauges test result for BDG 4 beam Figure 4 36: (a) strain gauge result for BDG 4 beam left side, (b) Strain gauge result for BDG 4 beam right side Figure 4 37: (a) strain gauge profile for BDG 4 beam , (b) crack pattern for BDG 4 Beam Figure 4 38: DIC capture for crack propagation in different load level for BDG 4 Figure 4 39: BDG 4 beam failure flexural crack appeared at 22.9 KN and propagate d , Flexural Shear cracks propagate at 60.2 kN Concrete cru sh , and beam fail at 65.3 kN Figure 0 40: (a) Crack propagation for BDG 0, (b) Crack propagation for BG3 0

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xxii Notation BDG 0 Beam has uniform distributed grooves terminated in end edge of FRP BDG 2 Beam has uniform distributed grooves terminated in 2 in away from end edge o f FRP BDG 4 Beam has uniform distributed grooves terminated in 4 in away from end edge of FRP BG3 0 Beam has three grooves terminated in end edge of FRP BG3 2 Beam has three grooves terminated 2 in away from end edge of FRP BG3 4 Beam has three grooves terminated 4 in away from end edge of FRP COT Plain surface Concrete block (without groove), beam without groove and FRP COT_CFRP Beam strengthened by FRP without grooves P1S Prism has one SMP layer P1U Prism has one U wrap P2S Prism has two SMP layer P2U Prism has two U wrap P3S Prism has three SMP layer P3U Prism has three U wrap P4S Prism has four SMP layer P4U Prism has four U wrap P5S Prism has five SMP layer

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xxiii P5U Prism has five U wrap PG1 Prism has one gr oove PG2 Prism has two grooves PG3 Prism has three grooves PG4 Prism has four grooves PG5 Prism has five grooves

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1 CHAPTER ONE I NTRODUCTION 2.2 General Structures are exposing t o o many environmental factors through a lifetime and cause dec environmental effects cause lowering in the life of structures, structures it composite of structures members (beams, columns, slab). These members are creating from c oncrete (cement, sand, gravel, reinforcement bars), these materials are exposed to a hard condition like corrosion, contraction, elongation, relaxation and this effect directly on building performance. In the United States, 40% of bridges need maintenance and rehabilitation through bridge lifetime (Wai Fah Chen and Lian Duan 2000). Many solutions were created by engineers to retrofit members and rehabilitation to correct performance for carrying applying load to extend structure lifetime, one of these metho ds is adding concrete, steel jacket, steel encasement and adding steel straps to members to increase strength and ductility (Hiroshi Fukuyama and Shunsuke Sugano 2000). However, these techniques will add more service load to structure and foundations may n ot design for additional weight.

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2 The fantastic universal solution is using lightweight material Fiber reinforced polymer many engineers since 1990 (Cheng and Teng 2003 ). It is light material, noncorrosive and has high tensile strength, FRP material consists of glass and carbon, it is glued to structure members by epoxy to increase stiffness and member capacity. FRP materials can be applied at the bottom of beams to incr ease beam performance for flexural strength, or wrap around columns to increase column performance for compressive strength and same for slab and other structures members. 2.3 Research Significance Members strengthening by FRP depend on the bond quality of adh esive material (epoxy). An adhesive material (epoxy) is responsible for transferring stress to the members, and concrete members cannot resist high shear stress. However, cracks appear and debonding occurring in the region of high shear stress which is usu ally at the end of FRP sheet. These cracks will cause loss of the connection between FRP and member (concrete or steel), in interfacial shear stress. Many res earchers studied this case and trying to determine an approximate value for shear stress compared with finite element models and detected the bond which is effected by a surface quality and concrete strength quality (E.Y. Sayed Ahmed, R. Bakay, N.G. Shrive ).

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3 Concrete compressive strength is a way to control interfacial shear stress which is causing increases or decreasing in interfacial shear stress depends on the concrete quality (Teng et al. 2002), this method is used to modify interfacial stress by chan ging materials properties. This research studied method to reduce interfacial shear stress by modifying the surface, and material properties then compare results with the common way of applying epoxy with FRP. 2.4 Objectives This research is studying interfa cial shear stress for strengthened members by FRP materials to investigate the method for reducing stresses. That will achieve members to resist high load, which occurs high performance for structure, for this purpose three methods have been used to reduce interfacial shear stress by modifying a surface of connection between epoxy and concrete members, increasing area of connection and using another material besides epoxy to extend FRP performance. We can get it by investigating failure load of three set o f modified blocks, so three phases have been created and investigated: 1. Failure load of each set and compare it with control unmodified set. 2. Investigate the strain of each set and compare it with unmodified control set. 3. Investigate energy dissipation of each set. 4. Studying failure mode of each set and compare it with control set. 5. Investigate failure load of strengthening and strengthen concrete beams. 6. Investigate failure mode of strengthening and strengthening concrete beam s.

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4 2.5 Scope This research has main three phases of concrete blocks (prisms) each phase has six categories, each category has five specimens. T he first category of phase I represented five unmodified prisms specimens (plane surface). The second category rep resented prisms has one groove (20) mm width by (15) mm depth. The third category prisms have two grooves each groove has (20) mm width, (15) mm depth and spacing (70) mm center to center between grooves. The fourth category has three grooves each grove h as (20) mm width by (15) mm depth and spacing (60) mm center to center between grooves. The fifth category has four grooves each groove has (20) mm width by (15) mm depth and spacing (50) mm center to center between grooves. The sixth category represent p rism has five grooves; each groove has (20) mm width by (15) mm depth and spacing (40) mm center to center between grooves. Phase two also represent six category each category has five specimens, The first category represents plain surface prisms, the sec ond categ ory represents prism has one U w raps (15) mm width by ( 21 0) mm length, third cate gory represent prism has two U wrap traps (15) mm width by ( 21 0)mm length and spacing (70)mm center to center, fourth catego ry represent prism has three U w raps (1 5) mm width by ( 21 0)mm length and spacing (60)mm center to center, fifth categ ory represent prism has four U w raps (15) mm width by ( 21 0)mm length and spacing (50)mm center to center and sixth categ ory represent prism has five U w raps (15) mm width by ( 21 0)mm length and spacing (40)mm center to center.

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5 Third phase represents six category each category has five specimens, first category represent plain surface prisms, second category represent prism has one layer of SMP material (15) mm width by (50) mm len gth, third category represent prism has two zones of SMP material each has (15) mm width by (50)mm length and spacing (70)mm center to center, fourth category represent prism has three SMP zones (15) mm width by (50)mm length and spacing (60)mm center to center, fifth category represent prism has four SMP zones (15) mm width by (50)mm length and spacing (50)mm center to center and sixth category represent prism has five SMP zones (15) mm width by (50)mm length and spacing (40)mm center to center. Tension force applied on FRP and studied deboned strength for each category and compare it with control blocks (plain surface) also studied failure mode and energy dissipation. 2.6 Thesis outline This research has five main chapters each chapter explain s p art of the investigation as below: Chapter 2: explain s literature review of previous researche r s related to strengthen members using FRP, concrete blocks(prisms) appl ying direct shear stress and study ing the behavior of unmodified (plain surface prisms) an d describ ing materials properties used in an experimental test. Chapter 3: explain s details of the experimental procedure of three phases of concrete blocks include blocks preparations, test setup, blocks behavior under direct shear stress, load displa cement behavior, load strain behavior, strain prof ile, stress profile and energy dissipation and compare

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6 all results with plain surface blocks and discus decreasing in interfacial shear stress by using these technics. Chapter 4: Investigate s set of modifie d RC beams by using grooves and studying load displacement, load strain, strain in reinforcement bars and discu s s ing these results with strengthening concrete beams. Chapter 5: explain s conclusions and some recommendations for future researche r s .

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7 CHAPT ER TWO LITERATURE REVIEW 2.1 Introduction This chapter will discuss a method of strengthening structural members (beams) by using FRP material. Also, it will discuss reducing shear stress at the end of beams (near supports) and explain used materials prope rties; cement, FRP types, purposes, and installation method. Another kind of epoxy material (SMP) will illustrate specifications, the purpose of using this type of epoxy. Also, it will discuss failure type in structures with focusing on shear failure and discuss other research related to this kind of failure. Finally, it will discuss how this topic leads to improve load carrying capacity, displacement and strain by using grooves, U wrap, and SMP epoxy material. 2.2 Background The concrete structure is everyw here around cities; concrete is a cheap material and easy to That happens when mix aggregate, sand, cement, and water. So, the result is concrete. Concrete is hard, durab le and robust material. Concrete has high resistance to compression and weak in tension. Concrete is mixed with reinforcement bars to increase compression and tension resistance for solving the tension weakness issue.

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8 Sometimes it needs high increase tens ion strength for concrete members in structures, so compression force applied performance. Struct ural concrete member is exposing to massive environmental effect such as fire, flood, tornados, freezing, many solutions developed to repair damaged members and structure but still expensive especially for replacing. One of the conventional solutions is st rengthening concrete members by high resistance material specification such as epoxy and FRP. It is good for saving time, cost and increase structure life and performance . 2.3 Fiber Reinforced Polymer (FRP) 2.3.1 Introduction: One of most excellent choice in the tw entieth century in material engineering technology is a fiber reinforced polymer (FRP). This composite material has low weight and high strength. It is anisotropic material, lightweight material, durable material for construction, chemical resistance. FRP is showing high resistance to corrosion, fast cure, high strength resistance, low density, high elastic, low conductivity, low density, high elastic modulus, high workability, high fatigue resistance and high impact resistance (Wang, Dai, & Harries, 2013). Another advantage of using FRP material does not need special tools for applying, just clean the surface and make sure it is dry and glue with the member surface by epoxy.

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9 FRP can be applied in any part of a structure, in columns to increase compressive s trength, for beams can be used at the bottom to improve flexural strength, for both metal and concrete structures. Though, that will lead increasing in member strength without adding additional weight to foundations. 2.3.2 FRP types FRP has three types, dependi ng on the method of production, and each one has own specifications, properties, and applying method, these types are: 1 CFRP: Carbon Fiber Reinforced Polymers, it is carbon based anisotropic material, and it produced at a high temperature of 1300 C. It has lightweight, high strength, high creep resistance, high resistance to chemical, high elastic modulus beside that, it is brittle material and expensive. 2 GFRP: Glass Fiber Reinforced Polymers. It is glass based isotropic material. It has high strength , a nd high resistance to water and chemical, the common types of it are C Glass, E Glass, and S Glass. 3 is anisotropic material and has high tensile strength, high stiffness, high im pact resistance , high modulus, low weight but low compression and more expensive than CFRP & GFRP. It has five types Kevlar 29, Kevlar 49, Kevlar 100, Kevlar 119, Kevlar 129. Table 3 1 is showing the difference between these three types of FRP.

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10 2.3.3 FRP U se Th e retrofit word means updating exist thing by applying new material after manufacture. That has happened in structure when resisting higher load or exposing to a massive environment like a flood, earth quick, tornados which cause a loss in a member ductili ty and stiffness. Many materials have been used before to correct members strength and ductility like, installing steel plates on concrete members (Jacket), or using external post tension; all these techniques improved damaged structure performance. Steel plate underneath beam is used to increase flexural strength (Fleming and King 1967), but it needs professional tools and technicians for installation, maintenance, so it is expensive. However, the most important thing is adding more load to structure foun dation, and these foundations may not designed for these additional weights. As explained in the previous section FRP is the most common solution for structure retrofit; it is lightweight material, high resistance to corrosion, high strength resistance, a nd long term performance. For rehabilitate, modfy structure strength to resist additional loads for this purpose licensed professional engineer needs evaluating the structure to determine the type of damages (shear, flexural, compression) then determine F RP type, installation method and applying locations. Rating happens after reviewing as built drawings and determining compressive strength for existing concrete members and corrosion for steel members. All this information gives evaluator idea about stru cture performance, and the locations need to retrofit. However, FRP is not applied just to failed members; it may also be used for

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11 members (beams or columns) because applying FRP just for the failed member will improve member stiffness and may c ause damage in neighbors members. ACI code 364.1R and ACI 437R have a brief description of structural analysis and investigation method. The adhesives used to glue FRP with concrete members (epoxy), it provides shear resistance between concrete and FRP, epoxy is a common product using to bond FRP with concrete or steel members. 2.4 Epoxy types and s pecifications Epoxy is thermosetting polymer contains two groups of materials mix until getting viscosity, so we can use it to fill cracks or bond another mate rial like FRP. All epoxy type has own specifications depend on manufacturer specifications and usually consist of two compounded (hardener and resin) mix together with mixing ration 1:2 or 1:3 and it is left for curing for one to seven days. In this resear ch will focus on MBrace Saturant 4500 type and specifications as shown in the table (2 2), Mix ratio used (hardener to resin) was 1:3 and curing time seven days, before applying epoxy concrete surface cleaned and dried, hardener and resin mixed carefully u ntil getting homogeneous then used. All tests that in this research, mixed hardener and resin in ratio 1:3 by volume or weight mixed by special tools until mix get homogeneous.

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12 Epoxy is applied on the concrete surface (blocks and beams), then placed FRP sheet, after that put another layer of epoxy above FRP sheet and left for curing for seven days in a 2.5 Previous study and research on concrete strengthened by FRP. 2.5.1 Failure mode of Concrete Blocks Neu bauer and Rostasy, 1997; Chen and Teng; 2001), mentioned in their papers that they are many failure load types. The frequent failure is called (interfacial bond) as shown in (Figure 2 1, A); failure happened when debonding occurs between epoxy and concre te, sometimes crack propagates at the end of the block due to high tension force and causes a separate part of concrete from a block. The second type of failure called (tension shear failure ) as shown in (figure 2 1, B). This occurs at the back end of FR P when epoxy layer too thick; this type of failure, not an ordinary happening. The third type of failure leads to damage in FRP due to a high bond between epoxy, FRP, and concrete called (FRP rupture or damage) as shown in (Figure2 1, C).

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13 (A) (B) ( C) (D) Figure 2 1 : Failure Mode in concrete blocks 2.5.2 Mechanism of bond transfer from FRP to concrete When applying a tension force to FRP glued with epoxy to a fixed block, strain in the adhesive will follow applied load and increase gradually with th e increasing load (E.Y.

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14 Sayed Ahmed, R. Bakay, N.G. Shrive2009). As shown in (Fig 2 1, D) , strain keeps r a ising until reach concrete maximum strain value. When strain exceeds maximum concrete strain value, crack debonding occurs at the end of the block fr om force side. By the increasing load, strain keeps increasing until debonding occur between epoxy and concrete block because strain exceeds maximum strain value for concrete and epoxy. According to (J.G. Teng, H. Yuan, J.F. Chen 2006) failure pass in thre e stages: 1 Elastic stage: occur s when applying load is small and interface stress in elastic mode and lower than max interface stress. 2 Soften stage: occur s when applying load increase s and interface stress equal to max interface stress. 3 Debond Stage : occur s when applying load increase s and interface stress exceed s maximum interface stress , debonding happen between epoxy and concrete due to high interface stress and strain. 2.5.3 Behavior of structure members strengthened by FRP Many researchers studied the mechanism of CFRP bonded to concrete and retrofit failed RC members by using CFRP, Täljsten, B. (1997) discussed strengthening method for RC members by FRP with epoxy adhesive and the improvement in strength and stiffness for concrete members. Also, they focused on the minimum anchor length of a plate that is needed to transfer stress from steel and concrete.

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15 For this purpose, researcher studied strain behavior for two categories (16 steel beam and four RC beams). For steel beam, they focused on the stre ngth of beams strengthening by various CFRP length and width (length various from 100 800mm, and width various from 40 80mm) with constant thickness 2.9mm. The failure mode for concrete beams was cracking and peeling off for FRP and steel category, was the extension in steel before failure. Also, they discussed the strain behavior comparing with anchor length (Lc), results showed increased in load carrying when increase anchor length plus more safety for structure for steel beam category. For the concret e beam, category prepared four beams with the various length of anchoring (100 400mm) with constant width and thickness, 50mm and 1.5 mm respectively. Failure mode was not yielded or abruptly failure, also results showing RC beams have extended anchor leng th stiffer than RC beam have shorter anchor length. (Ebead, U. A., Neale, K. W., & Bizindavyi, L. 2004, December) studied mechanism of fiber reinforced polymer and interface stress effect of bond FRP, adhesive and concrete surface. From the conclusion of t his research and other researchers related to this topic, conclude the debonding laminate and FRP from the concrete surface depends on below conditions: a Bond stress depend on tensile strength for concrete (Triantafillou and Plevris 1992) b Flexur al rigidity for laminate layer (Triantafillou and Plevris 1992) c Concrete surface properties (Van Gemert1980) d Thickness of adhesive.

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16 Also, they explained the separation of FRP sheet happened for high shear strength in adhesive cause cracks then separation. Increasing or decreasing in bond strength depends on concrete strength itself and surface preparation, the authors improved that by finite element models. For comparison with analytical results, concrete blocks prepared with various lengths of adhesive and FRP sheet, and it applied peeling force at the free end of FRP, strain measured at different locations on adhesive. The authors concluded the strain decrease along adhesive layer, and this performs applied for force transfer from FRP to epoxy then to concrete. 2.5.4 Failure mode of RC members strengthened by FRP (Ritchie st al.1991: saastmanesh and Ehsani 1991) mentioned that the f ailure mode depends on the duration of strengthened material progress in a test, and this could be divide d into two ca tegories: First, strengthen material still activ e until reaching ultimat e load, failure happen ing depend s on beam fabrication quality (reinforcement bar amount, a compressive strength of concrete) . So, the common f ailure for this category is crush in concr ete or FRP rupture or shear failure . Second, strength material fails before reaching ultimate strength and common failure happens interface debonding between epoxy and concrete.as shown in Fig (2 2). ( Sharif et al.1994 ) studied failure mode with laminate t hickness, thin laminate bonded to RC beam failure occurred in FRP rupture, increasing laminate thickness lead to interface

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17 debonding or FRP peel off from the terminated end , and common failure happened at the end of the beam (near support). To avoid FRP pe eling off from end many solutions used like anchored bolt for FRP end or U shape steel plate applied at the end of FRP this will increase shear strength 150% than beams without anchored (Sayed Ahmed, E. Y.2009). (Ross et al. 1999) M entioned t he ratio of re inforcement bar amount and cross section area w ould affect the failure load . Increasing ratio of reinforcement bar lead to failure move to compression zone, and shear crack will propagate between laminate and reinforcement bars, The Author conclude s the displacement in mid span of the beam with the higher reinforcement ratio is lower than the beam with the light r atio of reinforcement bar. S o, the beams have light reinforcement ratio failure occur s in laminate and increase in displacement in mid span of t he beam.

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18 Source : Sayed Ahmed, E. Y., Bakay, R., & Shrive, N. G. (2009). Bond strength of FRP laminates to concrete: a state of the art review. Electronic Journal of structural engineering, 9(1), 45 61. Figure 2 2 : (a) Flexure failure by FRP rupture, (b) Flexure failure by concrete crushing, (c) shear failure, (d) concrete cover separation, (e) plate end interfacial debonding, (f) flexure crack induced in interfacial debonding, (g) critical diagonal crack induced interfacial debonding

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19 Table 0 1 : FRP types and properties FRP types Specific gravity (gr/cm3) Tensile Strength (N/mm2) Modulus of elasticity (N/mm2) CFRP 1.75 3100 220000 GFRP 2.54 2410 70000 AFRP 1.46 3600 124000 Table 2 2: Epoxy Physical Properties Tensi le Properties Density 6.13 Pcf (983 kg/m3) Yield Strength 7900 psi (54 Mpa) Strain at Yield 2.5% Elastic Modulus 440 ksi (3034 Mpa) Ultimate strength 8000 psi (55.2 Mpa) Rupture Strain: 3.5% 0.40 Compressive Properties Yield Stre ngth 1200 psi (138 Mpa) Strain at Yield 3.8% Elastic Modulus 540 ksi (3724 Mpa) Ultimate Strength 20000 psi (138 Mpa) Rupture Strain 5% Functional Properties CTE 20*10 6/F Thermal Conductivity 1.45 Btu.in/hr.ft2 Glass Transition Temp, Tg 3 71C)

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20 C HAPTER THREE BEHAVIOR OF CONCRETE BLOCKS STRENGTHENED WITH FRP SHEETS SUBJECTED TO TENSION 3.1 General overview The experimental tests used to investigate concrete blocks (prisms) bounded with FRP sheet behavior after applying a tension force to the free end o f FRP, epoxy exposed to shear stress due to tension force. To study shear force effect on epoxy, and the best option to reduce the shear force, three phases have been created. Each phase has five categories, and each category has five specimens. This chapt er will describe all experimental work related to this research; next section 3.2 will describe experimental program and material used to prepare specimens. Also, it will represent test matrix. The three phases will discuss prism behavior on load displacem ent, strain behavior, Energy dissipation and comparison between each category. 3.2 E xperimental program 3.2.1 Test specimens Total of 95 concrete block s (prisms) used in research, the blocks made of concrete have compressive strength 18 MPa (3045) Psi and has dime nsion 300mm (12) in long x 100mm (4) in height x 50mm (2) in width.

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21 concrete prepared for blocks and poured inside molds has dimensions 300mm (12) in long x 100mm (4) in height and left for curing for 28 days then concrete saw used to cut blocks 50mm (2) in width. Five blocks strengthened with epoxy and FRP and left seven days for curing, FRP sheet had 431.8mm (17) in length and 50 mm (2) in width placed on each block, results for these blocks used as control data to compare it with other blocks as follows : 1 Five blocks made with one groove had dimension 50 mm (2) in length and 20 mm (0.78) in width with 15 mm (0.59) in depth, these grooves filled out with epoxy. 2 Five blocks made with two grooves had dimension 50 mm (2) in length, and 20 mm ( 0.78) in width with 15 mm (0.59) in depth, 70mm center to center spacing between grooves , these grooves filled out with epoxy. 3 Five blocks made with three grooves had dimension 50 mm (2) in length and 20 mm (0.78) in width with 15 mm (0.59) in dep th with spacing 60mm center to center between grooves. 4 Five blocks made with four grooves had dimension 50 mm (2) in length and 20 mm (0.78) in width with 15 mm (0.59) in depth with spacing 50mm center to center between grooves. 5 Five block s made with five grooves had dimension 50 mm (2) in length and 20 mm (0.78) in width with 15 mm (0.59) in depth with spacing 40mm center to center between grooves. As shown in figures (3 1,3 7,3 13,3 19). Other 25 blocks had the plain surface but applie d U wrap had 210 mm (5.1) in length, and 20 mm (078) in width applied at the locations of grooves.

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22 Five specimens one U w rap prepared and another five specimens had two U wrap and same for other specimens three U wrap, four U Wrap and five U Wrap as show n in pictures. Rest of 25 blocks applied SMP material at the location of grooves for each block, first placed epoxy then SMP and left for curing seven days, five blocks for each category prepared, as shown in pictures. 3.2.2 Test setup Specimens were prepared b y gluing FRP sheet to prism by epoxy, then were left seven days for curing then were prepared for a test, the tension force applied by MTS machine with displacement rate 0.3 mm/min, concrete blocks fixed inside a metal frame (fixture ). The fixture set in lower grips of MTS machine and FRP set in upper grips of MTS machine. The first attempt for the test, slipping issue faced from FRP fixing side because FRP sheet is too thin. For solving this problem, two layers of FRP sheets with dimensions 50mm x50mm (2i nx2in) were glued to free end of FRP sheet by G flex epoxy type and left one days for curing to make CFRP sheet thicker so they could hold by MTS grips and solve slipping problem. Displacement was measured by laser instrument, a special tape was fixed on F RP sheet, and another one was placed on fixed tape on MTS then set up the laser light to be between two tapes. After making sure all set up correctly, test run by applying displacement force to FRP sheet and waited until specimen failed.

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23 3.3 Materials Concrete , epoxy, CFRP , and SMP has been used in all tests as follows: 3.3.1 Concrete Concrete blocks prepared by using Portland cement, sand, aggregate and water with mix ratio designed according to ACI 304R specifications. Concrete prepared according to mix design sho wn in table 3 2 with compressive strength 18 MPa at 28 days. The concrete mixer used for concrete preparation. Concrete mixed and casted in metal forms have dimensions 300mm (12 in) length and 100 mm (4in) width with 100 mm (4 in) depth; concrete left sev en days in curing room for curing purpose. Concrete cylinders poured to determine compressive strength for blocks, results for cylinders shown in table 3 3 . The concrete saw has been used to cut prisms into two blocks; each block has dimension 300mm (12in ) length and 50mm (2 in) width with 100mm (4 in) thickness. 3.3.2 Epoxy Epoxy used to bond FRP sheet with concrete blocks, epoxy consist s of two part hardener and resin, mixed with ration 1:3 and left for seven days for curing as manufacturer specifications. Epo xy Density 6.13 pcf (983 kg/m3), Yield Strength 7900 psi (54 M P a), Strain at Yield 2.5%, Elastic Modulus 440 ksi (3034 M P a), Ultimate strength 8000 psi (55.2 M P a), Rupture

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24 0.40, Compressive Properties, Yield Strength 1200 psi ( 138 M P a), Strain at Yield 3.8%, Elastic Modulus 540 ksi(3724 M P a), Ultimate Strength20000 psi (138 M P a), Rupture Strain 5%, Functional Properties CTE 20*10 6/F, Thermal Conductivity 1.45 Btu.in/hr.ft2, Glass Transition Temp, Tg163 F(71C) Blocks cleaned by grinder to remove dust and left in oven for five minutes to make sure blocks are dry. 3.3.3 SMP Silyl Modified Polymer (SMP) is used for bonding and sealing metal, aluminum frames and joint filler for roofs and floors because of fast curing and resistance to UV , it is just one part and low curing time , other technical data showing in the table (3 1) . S MP reduce s energy then causes reducing load and increasing in displacement , SMP may dissipate applied energy before transfer to FRP ( Kim, Y. J., LaBere, J., & Yosh itake) 3.3.4 FRP FRP sheet used in all tests, FRP was cut in dimension 50 mm (2 in ) width and 430mm (17 in ) length and glued to concrete blocks by epoxy . E poxy applied to two layers, the first layer applied directly to prism surface and grooves then FRP sheet applied and another layer of epoxy applied above FRP sheet, for FRP specification, types, technical data available in section 2.4.3

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25 3.4 Test Matrix Three phases used in this section each phase has 25 concrete blocks (prisms) divided as follows: Phase I : twen ty five total concrete blocks have dimension (300) mm length, and (50) mm width and 100 mm depth, these blocks divided in to five categories, each category have five blocks. The f irst category has five blocks with one groove in the surface , groove dimension 50mm length and 20 mm width, 15 mm depth. The s econd category has five blocks with two grooves in the surface , groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 70 mm center to center of the groove . T he t hird category has five block s with three grooves in the surface , groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 60 mm center to center of the groove . The f ourth category has five blocks with four grooves in the surface , groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 50 mm center to center of the groove . The f ifth category has five blocks with five grooves in the surface , groove dimension 50mm length and 20 mm width, 15 mm depth with dimension 40 mm center to center of the groove .

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26 Pha se II: twenty five total concrete blocks have dimension (300) mm length, and (50) mm width and 100 mm depth, these blocks divided in to five categories, each category have five blocks. The f irst category has five blocks with one U wrap around three sides o f the block , U n wrap dimension 21 0mm length and 20 mm width. The s econd category has five blocks with two U wrap around three sides of the block , U n wrap dimension 21 0mm length and 20 mm width, and spacing 70mm center to center. T he third category has five b locks with three U n wrap around three sides of the block , U n wrap dimension 21 0mm length and 20 mm width, and spacing 60mm center to center. The f ourth category has five blocks with four U wrap around three sides of the block , U wrap dimension 21 0mm length a nd 20 mm width, and spacing 50mm center to center. The f ifth category has five blocks with four U wrap around three sides of the block , U wrap dimension 21 0mm length and 20 mm width, and spacing 40mm center to center. Phase III : twenty five total concrete blocks have dimension (300) mm length, and (50) mm width and 100 mm depth, these blocks divided in to five categories, each category have five blocks. The f irst category has five blocks with one SMP layer in the surface , SMP dimension 50mm length and 20 mm width, and has same epoxy thickness.

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27 The s econd category has five blocks with two SMP layer in the surface , SMP dimension 50mm length and 20 mm width, with spacing 70mm center to center between two SMP layers and has same epoxy thickness. T he t hird categor y has five blocks with three SMP layer in the surface , SMP dimension 50mm length and 20 mm width, with spacing 60mm center to center between each SMP layers and has same epoxy thickness. The f ourth category has five blocks with four SMP layer in the surfac e , SMP dimension 50mm length and 20 mm width, with spacing 50mm center to center between each SMP layers and has same epoxy thickness. The f ifth category has five blocks with five SMP layer in the surface , SMP dimension 50mm length and 20 mm width, with sp acing 40mm center to center between each SMP layers and has same epoxy thickness. 3.5 Test r esult of specimens with grooves In this section will discuss test result observed from experimental work for concrete blocks have parodic grooves and strengthened by C FRP, result output will be focused on load displacement, load strain behavior , failure mode and will illustrate how the number of grooves reduced strain value in epoxy, also it will illustrate energy dissipation for each category.

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28 E ach phase grouped in to s ix categories as explained in test matrix above and result s in T able ( 3 4) , same test setup used for each category , tension force from MTS machine and displacement measurement by laser extensomete r. 3.5.1 Load carrying capacity The load carrying obtained from te st result for each category as shown in Table3 4 and Table 3 5 . F or first category (COT) specimens without grooves average of failure load was 5.99 k N (1.34 ) kip, standard deviation 0.68 and coefficient of variation 0. 11, this category used for all other p hases just to figure out groove effectiveness on load carrying development for each category. First category PG1 (prism has on e groove) showing increasing in load carrying capacity, five blocks tested an average of failed load was 9.03 k N ( 2. 01 kip ) , stand ard deviation 1.03 and coefficient of variation 0.11 , groove performed increasing ratio in load carrying capacity 50.75% , second category PG2 (prism has two periodic grooves) showing more increasing in load carrying capacity as well , five sp ecime ns failed in average load 9.84 k N (2.21)kip two groove s will perform increasing in load carrying capacity ratio 64.27 % comparing with COT category. Third category PG3 (prisms have three pe riodic grooves) five specimens failed in average load 10.27 K N (2. 29 kip ) , standard deviation (1.07) and coefficient of variation (0.1) which is mean if add three groove s performed increasing in load carrying capacity ratio 71.45% comparing with COT catego ry.

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29 F o u rth category PG 4 (prisms have f our periodic grooves) five specimens failed in average load 10. 35 Kn (2. 32 kip ) , standard deviation 0.97 and coefficient of variation 0. 09 , that is mean ing add f our grooves will perform load carrying capacity 7 2.78 % com paring with COT category. Fifth category PG5 (prisms have five periodic grooves ) five specimens failed in average load 10.63 Kn (2. 38 kip ) , standard deviation 1.67 and coefficient of variation 0.16, that i s mean add five grooves will perform load carrying capacity 77.4% comparing with COT category. To reflect this improvement in CFRP load carrying capacity in construction filed, for grooves can create it in steel cover zone for beams, one side of grooves must cover with duct tape then epoxy inject in gr ooves after fix CRRP sheet. 3.5.2 Load displacement behavior The displacement of all specimens measured by using laser extensometer instrument by fixed two tapes and adjust laser light to be between two tapes level. Device leveled carefully to make sure lase r light perpendicular on the prism and between two tape range. For first category COT (prism have plain surfaces without grooves) as shown in Figures (3 2), (3 5). Test results are showing load increasing linearly with displacement because it is brittle ma terial and average displacement 0.07 mm, (0.0029 in). For second category PG1 (prisms have one groove) showing load increasing linearly with displacement as shown in Figures (3 6) and (3 8), figures showing a semi linear relationship between load and displ acement that is happened for some slipping in the free end of CFRP.

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30 While the test progress, sometimes some crack occurred in the top of the prism which caused elongation in CFRP sheet and MTS spent time until CFRP tide again. Third category PG2 (prism has two grooves) Figures (3 9) to (3 12) showing a linear increase in load vs. displacement. At load range 4.5 kN to 7.5 kN happened abrupt load drop in test progress that occurred for a crack in blocks from applied tension force side. The cracks happened in the free end of prism and grooves location due to high tension force applied, average displacement for five prisms 0.18 mm (0.007) in, this same test behavior for all other categories. 3.5.3 Strain behavior of blocks has grooves Five strain ga u ges have been pre pared and glued to prisms with spacing 25.4 mm (1 in) center to center, and 50 mm (2in) away from the free end of blocks. Blocks installed inside the metal fixture and fixed in MTS machine applied displacement force in rate 0 . 3 mm/ min . Laser extensometer u sed to obtain displacement, data acquisition device, and load cell used to obtain strain values. Figures (3 30a,b,c) are showing a comparison between five categories in strain behavior in load range 2,4,6 and 8 KN, strain for COT prisms shows high strain v alue especially for ultimate applied load, this performs that grooves in prisms reduced strain values. In another trend showing strain in COT prism for load range 4 and 2 Kn, seems lower the difference in epoxy thi ckness at locations of strain ga u ges or difference in strain ga u ges alignment, or small difference in strain ga u ges locations spacing .

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31 3.5.4 Failure Mode First category COT concrete blocks failed when the applied load achieved maximum strain in epoxy and exce ed maximum values of strain in concrete. Cracks happened in epoxy interface layer and debonding lost between FRP sheet and concrete surface, debonding happened in FRP sheet and epoxy which causes separation of FRP from concrete block surface as shown in te st pictures. Other categories failed in two different modes: FRP rupture happened because the existing grooves in concrete surface reduced the strain in epoxy layer, which means epoxy layer can resist more load comparing with COT category, so wh en applied load exceed ultimate strength for FRP sheet, rupture in FRP sheet occurred Hairline cracks and FRP rupture. Hairline cracks propagated in the concrete block from applied tension force side, and grooves location. It means strain at thes e zones exceeds max strain for concrete. 3.5.5 Energy dissipation Energy dissipation obtained from experiment test, Figures ( 3 31 ) are showing energy dissipation for each category . I t is showing energy dissipation for five groove s blocks (PG5) is (1.61 kN.mm) , then it is higher than other categories, this perform s creating grooves in the concrete surface will reduce strain and increasing in applying force.

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32 3.6 Test result specimens with U wrap This section will discuss test result of experimental work for concrete blocks have parodic FRP U wrap glued over FRP sheet, FRP sheet glued by epoxy to concrete blocks, results data had been focused on load displacement, load strain behavior, energy dissipation and failure mode. Will discuss how increasing numbers of U wrap reduced strain value in epoxy and effect on failure mode for each category. This phase specimen grouped into six categories as explained in test matrix above and test results in Table 3 6, same test setup used for all categories, tension force from MTS mac hine, displacement measurement by laser extensometer and strain ga u ges glued for one specimen from each category to study strain behavior. 3.6.1 Load carrying capacity The load carrying gained from test result for each category shown in Table3 6 and Table 3 7. F or first category (COT) specimens without U wrap average of failure load was 5.99 KN (1.34 kip), standard deviation 0.68 and coefficient of variation 0.11, this category used for all other categories just to figure out U wrap effectiveness on load carrying development for each category. First category P1U (prism has one U wrap) is showing increases in load carrying capacity; five blocks tested an average of a failed load was 9.65 KN (2.16kip), standard deviation 1.25 and coefficient of variation 0.13, U wra p performed increasing in load carrying capacity ratio 61.1%.Second category P2U (prism has two periodic U wrap) showing more increasing in load carrying capacity as well, five specimens failed in average

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33 load 9.71 KN (2.18kip) standard deviation (0.95) an d coefficient of variation 0.09. That i s mean adding two U wrap will perform increasing in load carrying capacity ratio 62.1% comparing with COT category. Third category P3U (prisms have three periodic U wrap) five specimens failed in average load 9.83 kN (2.19 kip), standard deviation (0.92) and coefficient of variation (0.09) which is mean if add three U wrap performed increasing in load carrying capacity ratio 64.1% comparing with COT category. Fourth category P4U (prism have four periodic U wrap) five s pecimens failed in average load 10.03(2.25 kip), standard deviation (1.08) and coefficient of variation 0.11, mean if add four U wrap will perform increasing in load carrying capacity ratio 67.4% comparing with COT category. Fifth category P5U (pris ms have five U wrap categories) five specimens failed in average load 10.12 kN (2.27 kip), standard deviation 0.98 and coefficient of variation 0.10, mean adding five U wrap will perform load carrying capacity 68.9% comparing with COT category. 3.6.2 Load displacement behavior The displacement for all specimens measured by using laser extensometer instrument by fixed two special tapes and adjust laser light to be between two tapes level, instrument leveled carefully to make sure laser light perpendic ular on the prism and between two tape range. For COT category already discussed in section 3.5.2

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34 For first category P1U (prisms have one U wrap) showing load increasing linearly with displacement as shown in Figure (3 32) to (3 35), Figures showing the s emi linear relationship between load and displacement that happened for some slipping in the free end of FRP wile test progress. Second categoryP2U (prism has two U wrap) Figures (3 36), and (3 39) showing a linear increase in load vs. displacement. In loa d range 4 kN to 7 kN happened abrupt load drop in test progress that occurred for a crack in blocks from applied tension force side, cracks happened in the free end of prism due to high tension force applied or debonding happened in some U wrap. The averag e of displacement for five prisms 0.13 mm (0.0052 in). T his behavior is same for all other categories. 3.6.3 Strain behavior of blocks Five strain gauges have been prepared and glued on prism for each category; strain gauges spaced 25.4 mm (1 in) from center to center, and 50 mm (2in) away from the free end of blocks. Blocks installed inside the metal fixture and fixed in MTS machine and applied displacement force in rate 0.3 mm/min; laser extensometer used to obtain displacement, data acquisition device, loa d cell used to obtain strain values. Figures (3 54 a,b,c ) are showing strain values for each category. The shaded area represents U wrap location and showing the

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35 high value of strain comparing with other gauges, happened because of strain gauge rec ord strain from two side, first strain due to tension force from MTS machine, and second strain from u wrap this just for strain gauges glued directly over U wrap. S o for this phase, it is unable to compare strain between categories because strain varies f or each category especially when strain gauge glued over U wrap, for example, strain gauge #3 in category P4U glued over 2nd U wrap and same strain gauge #3 in category P2U glued over FRP sheet. 3.6.4 Energy dissipation behavior Energy dissipation obtained from experiment test . Figures ( 3 55 ) are showing energy dissipation for each category . I t is showing energy dissipation for each category. T his happened because some specimens failed with low load and high displacement and other failed with high load and l ow displacement. 3.6.5 Failure Mode First category COT failure behavior already discussed in section 3.5.4. Other categories failed in two different modes: FRP rupture, this occurred because U wrap distributes the shear stress over U wrap zone that reduced inter facial shear stress and the applied load exceed ultimate strength for FRP, so it failed in FRP rupture. Debonding, some prisms failed by debonding that happens because of weakness in the bonding of U wrap with prisms.

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36 3.7 Test r esult of specimens with SMP F or this phase summary results of experimental work showed in the table (3 8 ) & (3 9 ) for concrete blocks strengthened by FRP and two type of epoxy MBRACE 4500 and SMP . Will discuss the effect of SMP on load carrying capacity, load displacement, strain beha vior and energy dissipation. 3.7.1 Load carrying capacity The load carrying test result is shown in Tables 3 8 and Table 3 9. For category COT (specimens without SMP), the average of failure load was 5.99 kN(1.34 kip), the standard deviation was 0.68 and coeffi cient of variation was 0.11, this category used for all other categories just to figure out SMP effectiveness on load carrying development for each category. First category P1S (prism has one layer of SMP) is showing decreasing in load carrying capacity. F ive prisms tested and the average of failure load was 5.79 kN (1.29kip), the standard deviation was 0.51 and coefficient of variation was 0.09, SMP performed a decreasing ratio in load carrying capacity of 3.3%. Second category P2S (prism has two periodic SMP layers) showing more decreasing in load carrying capacity. As well, five specimens failed in an average load of 5.64 kN (1.26kip), standard deviation (0.37) and coefficient of variation 0.06, mean adding two layers of SMP will perform decreasin g in load carrying a capacity ratio of 5.85% in comparing with COT category.

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37 Third category P3S (prisms have three periodic SMP layers). Five specimens failed in average load 6.38 kN (1.4 kip s ), standard deviation (0.81) and coefficient of variation (0.13) which means adding three layers of SMP will perform increasing in load carrying a capacity ratio of 6.5% in comparing with COT category. Fourth category P4S (prism have four periodic SMP layers). Five specimens failed in an average load of 5.40 (1.2 kip s ) , standard deviation (0.63) and coefficient of variation 0.12, that i s mean adding four of SMP will perform decreasing in load carrying a capacity ratio of 9.84% in comparing with COT category. Fifth category P5S (prisms have five SMP layers). Five specime ns failed in an average load of 5.27 kN (1.18 kip), standard deviation 0.70 and coefficient of variation 0.13, mean adding five SMP layers will perform decreasing in load carrying capacity of 12% in comparing with COT category. 3.7.2 Load displacement beh avior As discussed in part 3.5.2 and 3.6.2 about measuring load displacement, all categories showed a linear relationship between applying load and displacement for the epoxy zone. When interface failure due to increas es in applying load interface a resis tance, it moves to next zone SMP, and it is known SMP reduce energy. So, the prism cannot resist high value of applying the load, and abrupt load drop happened in SMP zone until reaching the next epoxy zone, and linear behavior performs again between load and displacement as shown in Figure

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38 showing stepwise behavior. And, this is the same mechanism happened with all other categories. 3.7.3 Strain behavior of concrete Blocks strengthened by epoxy and SMP Five strain gauges have been prepared and glued on FRP for ea ch category. Strain gauges spaced 25.4 mm (1 in) center to center and 50 mm (2in) away from the free end o f blocks. The blocks installed inside a metal fixture and fixed in MTS machine and applied a displacement force in rate 0.3 mm/min; laser extensometer used to obtain displacement, data acquisition device, load cell used to obtain strain values, Figures (3 76a,b,c ) showing strain values for each category. The shaded area represents SMP zone, cannot do a comparison between strain improvement of each cate gory because strain gauges lay on the epoxy layer in some category and lay on SMP layer in other categories, but according to (Kim, Y. J., LaBere, J., & Yoshitake, I. (2013) strain gauges results consider in an acceptable range. 3.7.4 Energy dissipation behavior Figure 3 77 is showing energy dissipation for each category ; it show s performance in energy dissipation for developing in displacement due to add SMP la yers . Energy dissipation for PIS category ( 0.31) k N .mm , P2S category ( 0.3) kn.mm P3S category ( 0.58) kN.mm , P4S category ( 0.4) kN.mm and P5S (049) KN.mm comparing with COT category (0.21) kN .mm

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39 3.7.5 Failure mode All the five categories failed in debonding of FRP sheet from concrete surface, and some specimens debonding occurred but FRP sheet keeps stick to SM P layer because SMP it silyl material. Debonding happened in the epoxy layer and epoxy separated from concrete block surface, but SMP layer keep glued to concrete block as shown in the attached pictures. 3.8 Results and discussion If Compare all phases with co ntrol category (plan surface category), all phases showed improvement (increasing or decreasing) in comparing with COT category. However , this section will compare between each phase in load carrying capacity, energy dissipation and failure mode. Load carr ying capacity in according to Fig (3 78) showing approximately same improvement for grooves phase with U wrap Phase, grooves and U wrap showed increasing in load carrying capacity compared with COT category. However , SMP phase showed decreasing in load ca rrying capacity 4.9% for SMP reduce energy specification as explained in SMP properties in section 3.3.3. Strain behavior as mentioned in section 3.5.3,3.6.3& 3.7.3 could not compare between categories and phases for a location of strain gauges on U wrap and SMP, which cause varies in strain behavior due to changing in material properties and dimensions. This comparison was needed it to determine beams plan, so energy dissipation compression made, as shown in Fig (3 79) grooves improve energy dissipation c omparing with COT

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40 category, while U wrap phase showed the increase in energy dissipation comparing with COT category but lower than the grooves phase. SMP phase was showing increasing in energy dissipation comparing with COT category. The failure mode for grooves phase of most prisms failed in debonding and crush or cracks in concrete, as discuss it in section 2.3 failure type depend on the epoxy thickness and concrete quality, the good improvement cracks in concrete appeared before reaching ultimate load, which give some indication when member reach to the critical load. The failure mode for U wrap phase of most prisms failed in FRP ruptured, just a few of them failed in FRP ruptured and debonded for weakness in bonding between U wrap and concrete blocks. Comparing with grooves prisms internal cracks occurred maybe concrete cracks or damage in epoxy layer but not physically appeared, while grooves phase cracks physically appeared, which indication member reach to the critical situation, and this advantage point counts to grooves phase. SMP phase all prisms failed in debonding due to damage in a n epoxy layer. FRP sheet keeps stick to prism surface for silyl, and massive viscosity of SMP material and this type of combination of epoxy and SMP generate stable bond than epoxy compounded (Kim, Y. J., LaBere, J., & Yoshitake, I. 2013).

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41 Table 0 1 : Technical data for sily modified polymer (SMP) Curing method M oisture Specific gravity ca. 1.4 g/ml Skin forming tim e Ca. 10 min (20°C/50% R.H.) Open time < 15 min.* (20°C/50% R.H.) Curing speed after 24 hrs ca. 3 mm (20°C/50% R.H.) Shore A hardness ca. 55 (DIN 53505) Volume change < 3% ( DIN 52451) Green strength (max. l oad which can be applied per m2 ca. 300 Pa (Physica Rheometer MC100) Tensile stress (100%) un cured adhesive without sagging) ca. 1.7 MPa (DIN 53504/ISO 37) Tensile stress at break ca. 2.6 MPa (DIN 53504/ISO 37) Elongation at break ca. 250% (DIN 53504/ISO 37) Shear stress ca. 2.5 MPa (DIN 53283/ASTM D1002) (Alu Alu; adh. thickness 2mm, test speed 50 mm/min.) Tear propagation ca. 16 N/mm (DIN 53515/ISO 34 ) E Modulus (Type C, test speed 500 mm/min.) ( 10%) ca. 3.3 MPa (DIN 53504/ISO 37) Solvent percentage 0% Isocyanate percentage 0% Temperature resistance 40°C till +120°C Temperature resistance +180°C (max. /2hr) Application temperature UV and weather resistance excell ent +5°C t o +35°C Colours (standard) white, grey, black Packaging 290 ml cartridges, 600 ml bags

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42 Table 0 2 : Concert mix design W/C 45% Cement(kg/m 3 ) 380 Water (kg/m 3 ) 205 Aggregate (kg/m 3 ) 1200 Sand (kg/m3) 700 Table 0 3 : compressive strength results for cylinders at 28 da ys Specimen Compressive Stress at 28 days ( MPa ) C1 19.21 C2 18.54 C3 17.82 Average Compressive strength (M P a) 18.52

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43 Table 0 4 : Test results of Prisms with 1,2,3,4 and 5 g rooves ID Failure Load Displaceme nt Failure mode kN (Kip) mm (in) Each kN kip Ave. kN kip Each mm in Ave. mm in COT 1 6.65 (1. 49 ) 5.99 (1. 3 4 ) 0.06 (0.0023) 0.07 (0.0029) D COT 2 6.58 (1. 47 ) 0.05 (0.0019) D COT 3 6.18 (1. 38 ) 0.09 (0.00 34) D COT 4 5.20 (1. 16 ) 0.07 (0.0029) D COT 5 5.34 ( 1.19 ) 0.10 (0.0038) D PG1 1 9.18 (2. 04 ) 9.03 (2. 01 ) 0.26 (0.0101) 0.22 (0.0089) C&F PG1 2 7.76 (1. 73 ) 0.22 (0.0088) C&F PG1 3 9.25 (2. 07 ) 0.23 (0.0091) C&D PG1 4 10.51 (2. 35 ) 0.2 6 (0.0103) F PG1 5 8.44 ( 1.89 ) 0.15 (0.0059) C&D PG2 1 9.49 (2.1 2 ) 0.18 (0.0070) C&F PG2 2 9.79 (2.20) 0.20 (0.0071) C&F PG2 3 10.87 (2.44) 9.84 (2.21) 0.20 (0.0071) 0.18 (0.0070) C&F PG2 4 8.24 (1.85) 0.18 (0.0070) F PG2 5 10.79 (2.42) 0.16 (0.0062) F PG3 1 9.74 (2. 18 ) 10.27 (2. 29 ) 0.22 (0.0088) 0.19 (0.0076) F PG3 2 11.11 (2. 48 ) 0.22 (0.0087) F PG3 3 8.77 ( 1.96 ) 0.17 (0.0068) F PG3 4 11.43 (2. 56 ) 0.17 (0.0067) C&F PG3 5 10.30 (2. 30 ) 0.17 (0.0067) C&F PG4 1 11.27 (2. 53 ) 10. 35 (2. 32 ) 0.16 (0.0063) 0.21 (0.0086) C&F PG4 2 9.55 (2. 14 ) 0.19 (0.0073) F PG4 3 11.07 (2. 48 ) 0.23 (0.0111) C&F PG4 4 10.77 (2. 42 ) 0.25 (0.0099) F PG4 5 9.10 (2. 04 ) 0.21 (0.0083) F P5G 1 12.84 ( 2.87 ) 10.63 ( 2. 37 ) 0.25 (0.0098) 0.27 (0.0105) C&F P5G 2 10.22 (2. 28 ) 0.23 (0.009) C&F P5G 3 11.52 (2. 5 8) 0.27 (0.0105) C&F P5G 4 10.20 (2. 28 ) 0.29 (0.0113) F P5G 5 8.37 ( 1.87 ) 0.30 (0.012) F

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44 Table 0 5 : Standard deviation and COV for phase I test results ID F ailure Load Standard Deviation Coefficient of Variation kN (Kip) Each kN Kip Ave. kN Kip COT 1 6.65 (1. 49 ) 5.99 (1. 3 4 ) COT 2 6.58 (1. 47 ) COT 3 6.18 (1. 38 ) 0.68 0.11 COT 4 5.20 (1. 16 ) COT 5 5.34 ( 1.19 ) PG1 1 9.18 (2. 04 ) 9.03 (2. 01 ) PG1 2 7.76 (1. 73 ) PG1 3 9.25 (2. 07 ) 1.03 0.11 PG1 4 10.51 (2. 35 ) PG1 5 8.44 ( 1.89 ) PG2 1 9.49 (2.1 2 ) PG2 2 9.79 (2 .20) PG2 3 10.87 (2.44) 9.84 (2.21) 1.07 0.11 PG2 4 8.24 (1.85) PG2 5 10.79 (2.42) PG3 1 9.74 (2. 18 ) 10.27 (2. 29 ) PG3 2 11.11 (2. 48 ) PG3 3 8.77 ( 1.96 ) 1.07 0.10 PG3 4 11.43 (2. 56 ) PG3 5 10.30 (2. 30 ) PG4 1 11.27 (2. 53 ) 1 0. 35 (2. 32 ) PG4 2 9.55 (2. 14 ) PG4 3 11.07 (2. 48 ) 0.97 0.09 PG4 4 10.77 (2. 42 ) PG4 5 9.10 (2. 04 ) P5G 1 12.84 ( 2.87 ) 10.63 (2. 37 ) P5G 2 10.22 (2. 28 ) P5G 3 11.52 (2. 5 8) 1.67 0.16 P5G 4 10.20 (2. 28 ) P5G 5 8.37 ( 1.87 )

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45 T able 0 6 : Test Result for Prisms with 1,2,3,4 and 5 U wrap ID Failure Load Displacement Failure mode kN (Kip) mm(in) Each Ave. Each Ave. COT 1 6.65 (1. 49 ) 5.99 (1. 3 4 ) 0.06 (0.0023) 0.07 (0.0029) D COT 2 6.58 (1. 47 ) 0. 05 (0.0019) D COT 3 6.18 (1. 38 ) 0.09 (0.0034) D COT 4 5.20 (1. 16 ) 0.07 (0.0029) D COT 5 5.34 ( 1.19 ) 0.10 (0.0038) D P1U 1 9.97 ( 2. 24 ) 9.65 ( 2. 16 ) 0.13 ( 0.0051 ) 0.13 ( 0.0052 ) FR P1U 2 8.60 ( 1.93 ) 0.13 ( 0.0051 ) FR P1U 3 8.76 ( 1.96 ) 0.11 ( 0.0043 ) FR P1U 4 11.67 ( 2. 6 2 ) 0.16 ( 0.0063 ) FR P1U 5 9.24 ( 2. 07 ) 0.13 ( 0.0051 ) FR P2U 1 8.40 (1.88) 0.15 (0.0059) FR P2U 2 10.28 (2.31) 0.13 (0.0051) FR P2U 3 9.10 ( 2.04) 9.71 (2. 18 ) 0.16 (0.0063) 0.14 (0.0055) FR P2U 4 10.75 (2.42) 0.14 (0.0055) FR P2U 5 10.03 (2.25) 0.14 (0.0055) FR P3U 1 8.73 ( 1.96 ) 9.83 ( 2. 1 9 ) 0.09 ( 0.0038 ) 0.10 ( 0.0038 ) FR&DE P3U 2 9.76 ( 2. 19 ) 0.09 ( 0.0034 ) FR P3U 3 9.16 ( 2. 05 ) 0.09 ( 0.0038 ) FR P3U 4 10.72 ( 2. 3 0 ) 0.11 ( 0.0043 ) FR P3U 5 10.79 ( 2. 42 ) 0.10 ( 0.0038 ) FR P4U 1 9.94 ( 2. 23) 10.03 ( 2. 25 ) 0.15 ( 0.0059 ) 0.15 ( 0.0058 ) FR P4U 2 10.26 ( 2. 30 ) 0.14 ( 0.0055 ) FR P4U 3 8.33 ( 1.87 ) 0.13 ( 0.0051 ) FR P4U 4 11.30 ( 2. 54 ) 0.17 ( 0.0067 ) FR P4U 5 10.30 ( 2. 31 ) 0.15 ( 0.0059 ) FR P5U 1 10.67 ( 2. 39 ) 10.12 ( 2. 27 ) 0.13 ( 0.0051 ) 0.11 ( 0.0044 ) FR P5U 2 8.98 ( 2. 01 ) 0.10 ( 0.0038 ) FR P5U 3 9.20 ( 2. 06 ) 0.11 ( 0.0043 ) FR P5U 4 11.22 ( 2. 52 ) 0.12 ( 0.0047 ) FR P5U 5 10.53 ( 2. 36 ) 0.11 ( 0.0043 ) FR

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46 Table 0 7 : Standard deviation and COV for phase I I test results ID Failure Load Standard Deviation Coefficient of Variation kN (Kip) Each kN Kip Ave. kN Kip COT 1 6.65 (1. 49 ) 5.99 (1. 3 4 ) COT 2 6.58 (1 . 47 ) COT 3 6.18 (1. 38 ) 0.68 0.11 COT 4 5.20 (1. 16 ) COT 5 5.34 ( 1.19 ) P1U 1 9.97 (2. 24 ) 9.65 (2. 16 ) P1U 2 8.60 ( 1.93 ) P1U 3 8.76 ( 1.96 ) 1.25 0.13 P1U 4 11.67 (2. 6 2) P1U 5 9.24 (2. 07 ) P2U 1 8.40 (1.88) P2U 2 10. 28 (2.31) P2U 3 9.10 (2.04) 9.71 (2. 18 ) 0.95 0.09 P2U 4 10.75 (2.42) P2U 5 10.03 (2.25) P3U 1 8.73 ( 1.96 ) 9.83 (2. 19 ) P3U 2 9.76 (2. 19 ) P3U 3 9.16 (2. 05 ) 0.92 0.09 P3U 4 10.72 (2. 30 ) P3U 5 10.79 (2. 42 ) P4U 1 9.94 (2. 23) 10.03 (2. 25 ) P4U 2 10.26 (2. 30 ) P4U 3 8.33 ( 1.87 ) 1.08 0.11 P4U 4 11.30 (2. 54 ) P4U 5 10.30 (2. 31 ) P5U 1 10.67 (2. 39 ) 10.12 (2. 27 ) P5U 2 8.98 (2. 01 ) P5U 3 9.20 (2. 06 ) 0.98 0.10 P5U 4 11.22 (2. 52 ) P5U 5 10.53 (2. 36 )

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47 Table 0 8 : Test Result for Prisms with 1,2,3,4 and 5 SMP layers ID Failure Load Displacement Failure mode kN (Kip) m m (in) Each Ave. Each Ave. COT 1 6.65 (1. 49 ) 5.99 (1. 34 ) 0.06 (0.01) 0.07 (0.02) D COT 2 6.58 (1. 47 ) 0. 05 (0.01) D COT 3 6.18 (1. 38 ) 0.09 (0.02) D COT 4 5.20 (1. 16 ) 0.07 (0.02) D COT 5 5.34 ( 1.19 ) 0.10 (0.02) D P1S 1 6.23 ( 1. 40 ) 5.79 ( 1. 29 ) 0.10 ( 0.02 ) 0.10 ( 0.02 ) D P1S 2 4.94 ( 1. 11 ) 0.10 ( 0.02 ) D P1S 3 5.80 ( 1. 30 ) 0.09 ( 0.02 ) D P1S 4 5.83 ( 1. 31 ) 0.10 ( 0.02 ) D P1S 5 6.13 ( 1. 37 ) 0.10 ( 0.02 ) D P2S 1 5.99 (1. 34 ) 0.12 ( 0.03) D P2S 2 5.55 (1.24) 0.10 (0.02) D P2S 3 5.87 (1.32) 5.64 (1.26) 0.08 (0.02) 0.10 (0.02) D P2S 4 5.76 (1.29) 0.08 (0.02) D P 2S 5 5.05 (1.13) 0.10 (0.02) D P3S 1 6.23 ( 1. 40 ) 6.38 ( 1. 4 ) 0.20 ( 0.05 ) 0.16 ( 0.04 ) D P3S 2 6.99 ( 1. 57 ) 0.16 ( 0.04 ) D P3S 3 7.03 ( 1. 58 ) 0.15 ( 0.04 ) D P3S 4 6.58 ( 1. 47 ) 0.15 ( 0.04 ) D P3S 5 5.06 ( 1. 13 ) 0.14 ( 0.03 ) D P4S 1 4.90 ( 1. 10 ) 5.40 ( 1. 2 ) 0.15 ( 0.04 ) 0.14 ( 0.03 ) D P4S 2 5.46 ( 1. 22 ) 0.13 ( 0.03 ) D P4S 3 6.26 ( 1. 40 ) 0.12 ( 0.03 ) D P4S 4 5.68 ( 1. 27 ) 0.15 ( 0.04 ) D P4S 5 4.68 ( 1. 05 ) 0.14 ( 0.04 ) D P5S 1 5.16 ( 1. 16 ) 5.27 ( 1. 18 ) 0.08 ( 0.02 ) 0.15 ( 0.04 ) D P5S 2 4 .47 ( 1. 01 ) 0.16 ( 0.04 ) D P5S 3 6.02 ( 1. 35 ) 0.20 ( 0.05 ) D P5S 4 5.96 ( 1. 33 ) 0.19 ( 0.05 ) D P5S 5 4.74 ( 1. 06 ) 0.14 ( 0.04 ) D

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48 Table 0 9 : Standard deviation and COV for phase III test results I D Failure Load Standard Deviation Coefficient of Variation kN(Kip) Each kN Kip Ave. kN Kip COT 1 6.65 (1. 49 ) 5.99 (1. 34 ) COT 2 6.58 (1. 47 ) COT 3 6.18 (1. 38 ) 0.68 0.11 COT 4 5.20 (1. 16 ) COT 5 5.34 ( 1.19 ) P1S 1 6.23 (1. 40 ) 5.79 (1. 29 ) P1S 2 4.94 (1. 11 ) P1S 3 5.80 (1. 30 ) 0.51 0.09 P1S 4 5.83 (1. 31 ) P1S 5 6.13 (1. 37 ) P2S 1 5.99 (1. 34 ) P2S 2 5.55 (1.24) P2S 3 5.87 (1.32) 5.64 (1.26) 0.37 0.06 P2S 4 5.76 (1.29) P2S 5 5.05 (1.13) P3S 1 6.23 (1. 40 ) 6.38 (1. 4 ) P3S 2 6.99 (1. 57 ) P3S 3 7.03 (1. 58 ) 0.81 0.13 P3S 4 6.58 (1. 47 ) P3S 5 5.06 (1. 13 ) P4S 1 4.90 (1. 10 ) 5.40 (1. 2 ) P4S 2 5.46 (1. 22 ) P4S 3 6.26 (1. 40 ) 0.63 0.12 P4S 4 5.68 (1. 27 ) P4S 5 4.68 (1. 05 ) P5S 1 5.16 (1. 16 ) 5.27 (1. 18 ) P5S 2 4.47 (1. 01 ) P5S 3 6.02 (1. 35 ) 0.70 0.13 P5S 4 5.96 (1. 33 ) P5S 5 4.74 (1. 06 )

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49 Figure 3 1 (a) Top view for COT prism detail, (b) side view for COT prism detail, (c) COT pris m test setup, (d) COT side view test setup

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50 (a) (b) Figure 0 2 : (a) COT load displacement test result for prism COT 1 , FRP debond ing in 6. 6 5kn and displacement 0.0 6 mm, (b) COT load displacement test result for prism COT 2 , FRP debonding in 6.5 8 kN and displacement 0.05mm

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51 (c) (d) Figure 0 3 :(C) COT load displacement test result for prism COT 3, FRP debonding in 6.18kn and displacement 0.09m m , (d) COT load displacement test result for prism COT 4 , FRP debonding in 5.20kn and displacement 0.07mm

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52 (e) (f) Figure 0 4 : (e) COT load displacement test result for prism COT 5 , FRP debonding in 5.34Kn and displacement 0.10mm , (d) COT load displacement for all COT prisms

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53 ( a) (b) Figure 3 5 : Top view and side view for P G1 prism detail, (b) P G1 prism test setup

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54 (a) (b) Figure 3 6 : ( a) load displacement test result for prism P G1 1, FRP ruptured and hairy cracks appeared in 9.18kn , and displa cement 0. 2 6mm ( b) load displacement test result for prism PG1 2 , FRP ruptured and hairy cracks appeared in 7.76kn and displacement 0.22mm

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55 (a) (b) Figure 3 7 : (a) load displacement test result for prism P G1 3, FRP ruptured and hairy cracks appeared in 9.25kN and displacement 0.23 mm ( b) load displacement test result for prism PG1 4 , FRP ru ptured in 10.51 and displacement 0.26mm

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56 (a) (b) Figure 3 8 : (a) load displacement test result for prism P G1 5 , FRP debonding and hairy cracks appeared in 8.44 kN and displacement 0. 15 mm , (b) load displacement test result for prism for all PG1 prisms

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57 (a) (b) Figure 3 9 : (a) Top view and side view of PG2 prism d etail, (b) PG2 prism test setup

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58 (a) (b) Figure 3 10 : (a) load displacement test result for prism PG 2 1 , FRP ruptured , and hairy cracks appeared in 9. 49 kN , and displacement 0. 18 mm ( b) load displace ment test r esult for prism PG2 2 , FRP ruptured and hairy cracks appeared in 9.79 kN and displacement 0.20 mm

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59 (a) (b) Figure 3 11 : (a) load displacement test result for prism PG2 3, FRP ruptured , and hairy cr acks appeared in 10.87kN, and displacement 0.20 mm , ( b) load displacement test result for prism PG2 4 , FRP ruptured in 8.40 kN and displacement 0.18 mm

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60 (a) (b) Figure 3 12 : (a) load displacement test result for prism PG2 5 , FRP ruptured in 10.79kn and displacement 0.16 mm, (b) load displacement test result for all PG2 prisms

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61 (a) (b) Figure 3 13: (a)Top view and side view of PG3 pris m detail, (b) PG3 prism test setup

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62 (a) (b) Figure 3 14: (a) load displacement test result for prism PG3 1 , FRP ruptured in 9. 74 kn and displacement 0. 22 mm, (b) load displacement test result for prism PG3 2 , FRP ruptured in 11.11kN and displacemen t 0.22mm

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63 (a) (b) Figure 3 15: ( a) load displacement test result for prism PG3 3 , FRP ruptured 8.77kN and displacement 0.17 mm, (b) load displacement test result for prism PG3 4 , FRP ruptured and hairy cracks appeared in 11.43kN and displacement 0 .17mm

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64 (a) (b) Figure 3 16 : (a) load displacement test result for prism PG3 5 , FRP ruptured , and hairy cracks appeared in 10.30 and displacement 0.1 7 mm, (b) load displacement test result for all PG3 prism

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65 (a) (b) Figure 3 17: (a)Top view an d side view of PG4 prism detail, (b) PG4 prism test setup

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66 (a) (b) Figure 3 1 8 : (a) load displacement test result for prism PG4 1 , FRP ruptured , and hairy cracks appeared in 11.27 kN , and displacement 0.1 6 mm, (b) load displacement test result for PG4 2 prism , FRP ruptured in 9.55 kN and displacement 0.19 mm

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67 (a) (b) Figure 3 19 : (a) load displacement test result for prism PG4 3 , FRP ruptured , and hairy cracks appeared in 11.07 kN , and displacement 0.23 mm, (b) load displacement test resu lt for PG4 4 prism , FRP ruptured in 10.77 kN and displacement 0. 25 mm

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68 (a) (b) Figure 3 20 : (a) load displacement test result for prism PG4 5, FRP ruptured in 9.10 kN and displacement 0.21 mm, ( b) load displacement test result for all PG4 prisms

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69 (a) (b) Figure 3 21: (a)Top view and side view of PG5 prism detail, (b) PG4 prism test setup

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70 (a) (b) Figure 3 2 2 : (a) load displacement test result for prism PG5 1, FRP ruptured and hairy cracks appeared in 12.84 kN and displacement 0.25 mm, ( b) load displacement test result for PG5 2 prism , FRP ruptured and hairy cracks appeared in 10.22 kN and displacement 0.23 mm

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71 (a) (b) Figure 3 2 3 : (a) load displacement test result for prism PG5 3 , FRP ruptured , and hairy cracks appeared in 11.52 kN , and displacement 0. 27 mm , ( b) load displacement test result for PG5 4 prism FRP ruptured and hairy cracks appeared in 10.20 kN and displacement 0.29 mm

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72 (a) (b) Figure 3 2 4 : (a) load displacement test result for prism PG5 5, FRP ruptured in 8.37 kN and displacement 0. 30 mm ( b) load displacement test result for all PG 5 prisms

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73 (a) (b) Figure 3 25: (a) strain gauges location for COT, (b) strain gauge location for PG1

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74 (a) (b) Figure 3 26: (a) strain gauges location for PG2, (b ) strain gauge location for PG3

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75 (a) (b) Figure 3 27: (a) strain gauges location for PG4, (b) strain gauge location for PG5

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76 (a) (b) Figure 3 28: (a)strain gauge result for COT, (b) strain gauge results for PG1

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77 (a) (b) Figure 3 29: (a) st rain gauges results for PG2, (b) strain gauge results for PG3

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78 (a) (b) Figure 3 30: (a) strain gauges results for PG4, (b) strain gauge results for PG5

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79 (a) (b) Figure 3 30 a: (a) strain profile for COT prism, (b) strain profile for PG1 prism

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80 (a) (b) Figure 3 30 b: (a) strain profile for PG2 prism, (b) strain profile for PG3 prism

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81 (a) (b) Figure 3 30C: (a) strain profile for PG4 prism, (b) strain profile for PG5 prism

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82 Figure 3 31: (a) Energy dissipation for COT, (b) Energy dissip ation for PG1, (c) Energy dissipation for PG2, (d) Energy dissipation for PG3, (e)Energy dissipation for PG4, (F) Energy dissipation for PG5

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83 (a) (b) Figure 3 32: (a) P1U Top and side view, (b) strain gauge location for P1U

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84 (a) (b) Figure 3 33 : (a) Load displacement for PIU 1 prism , FRP ruptured in 9. 97 kn and displacement 0.1 3 mm, (b) Load displacement for P1U 2 prism , FRP ruptured in 8.6kN and displacement 0.13mm

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85 (a) (b) Figure 3 34: (a) Load displacement for PIU 3 prism, FRP ruptured i n 8.76kN and displacement 0.11 mm (b) Load displacement for P1U 4 prism , FRP ruptured in 11.67kN and displacement 0.16mm

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86 (a) (b) Figure 3 35: (a) Load displacement for PIU 5 prism, FRP ruptured in 9.24kn and displacement 0.13mm (b) Load displacement for all P1U prisms

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87 (a) (b) Figure 3 36: (a) Top and side view for P2U prisms, (b) strain gauges locations for P1Uprism

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88 (a) (b) Figure 3 37: (a) Load displacement for P2U 1 prism, FRP ruptured in 8.4 kN and displacement 0.15mm (b) Load displace ment for P2U 2 prism , FRP ruptured in 10.28kN and displacement 0.13mm

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89 (a) (b) Figure 3 38: (a) Load displacement for P2U 3 prism, FRP ruptured in 9.10kn and displacement 0.16mm (b) Load displacement for P2U 4 prism , FRP ruptured in 10.75kN and displ acement 0.14mm

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90 Figure 3 39: (a) Load displacement for P2U 5 prism, FRP ruptured in 10.03kN and displacement 0.14mm (b) Load displacement for all P2U prisms

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91 (a) (b) Figure 3 40: (a) Top and side view for P3U prisms, (b) strain gauges locati on for P3U prisms

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92 Figure 3 41: (a) Load displacement for P3U 1 prism, FRP ruptured and debonding in 8.73kN and displacement 0. 09 mm (b) Load displacement for P3U 2 prism , FRP ruptured in 9.76kn and displacement 0.09mm

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93 Figure 3 42 : (a) Load d isplacement for P3U 3 prism, FRP ruptured in 9. 16 kn and displacement 0. 09 mm (b) Load displacement for P3U 4 prism , FRP ruptured in 10.72kN and displacement 0.11mm

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94 Figure 3 43: (a) Load displacement for P3U 5 prism, FRP ruptured in 10.79kn and disp lacement 0.1 mm (b) Load displacement for all P3U prisms

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95 (a) (b) Figure 3 44 : (a) Top and Side view for P4U prism, (b ) strain gauges locations for P4U prism

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96 (a) (b) Figure 3 45: (a) Load displacement for P4U 1 prism, FRP ruptured in 9.94kn a nd displacement 0.13mm (b) Load displacement for P4U 2 prism , FRP ruptured in 10.26kN and displacement 0.14mm

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97 (a) (b) Figure 3 46: (a) Load displacement for P4U 3 prism, FRP ruptured in 8.33kN and displacement 0.13mm (b) Load displacement for P4U 4 prism , FRP ruptured in 11.30kN and displacement 0.17mm

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98 (a) (b) Figure 3 47: (a) Load displacement for P4 U 5 prism, FRP ruptured in 10.30kn and displacement 0.15mm (b) Load displacement for all P4U prisms

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99 (a) (b) Figure 3 48: (a) Top and Side view for P5U prism, (b) strain gauges location for P5U prism

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100 (a) (b) Figure 3 49: (a) Load displacement for P5U 1 prism, FRP ruptured in 10.67kN and displacement 0.13mm (b) Load displacement for P5U 2 prism , FRP ruptured in 8.98kn and displacement 0.1mm

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101 (a) (b) Figure 3 50: (a) Load displacement for P5U 3 prism , FRP ruptured in 9.20kn and displacement 0.1mm , (b) Load displacement for P5U 4 prism , FRP ruptured in 11.22kN and displacement 0.12mm

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102 (a) (b) Figure 3 51: (a) Load displacement for P5U 5 prism, FRP ruptured in 10.53kN and displacement 0.11mm (b) Load displacement for all P5U prisms

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103 (a) (b) Figure 3 52: (a) strain gauges results for P1U, (b) strain gauge results for P2U

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104 (a) (b) Figure 3 53: (a) strain gauges results for P3U, (b) strain gauge results for P4U

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105 (a) Figure 3 54: (a) strain gauges results for P5U

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106 (a) (b) Figure 3 54A: (a) S train Profile for COT prism, (b) Strain profile for P1U Prism

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107 (a) (b) Figure 3 54 B: (a) Strain Profile for P2 U prism, (b) Strain profile for P3U Prism

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108 (a) (b) Figure 3 54C: (a) Strain Profile for P4U prism, (b) Strain profile for P5U Prism

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109 Figure 3 55a : (a) Energy dissipation for COT, (b) Energy dissipation for P1U, (c) Energy dissipation for P2U, (d) Energy dissipation for P3U, (e)Energy dissipation for P4U, (F) Energy dissipation for P5U

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110 (a) (b) Figure 3 55: (a) Top and side view for P 1S prisms, (b) strain gauges location for P 1S prisms

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111 (a) (b) Figure 3 56: (a) Load displacement for P 1S 1 prism, FRP debonding in 6.23kN and displacement 0.1 mm (b) Load displacement for P1S 2 prism , FRP ruptured in 4.94 and displacement 0.10mm

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112 (a) Figure 3 57: (a) Load displacement for P1S 3 prism, FRP debonding in 5.8kN and displacement 0. 09mm ( b ) Load displacement for P1S 4 prism , FRP debonding in 5.73kN and displacement 0.1mm

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113 (a) Figure 3 58: (a) Load displacement for P1S 5 prism, FRP debonding in 6.13kN and displacement 0.1mm ( b) Load displacement for all P1S prisms

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114 (a) (b) Figur e 3 59: (a) Top and side view for P2S prisms, (b) strain gauges location for P2S prisms

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115 (a) (b) Figure 3 60: (a) Load displacement for P2S 1 prism, FRP, debonding in 5.99kN and displacement 0.1 2 mm (b) Load displacement for P2S 2 prism FRP, debondi ng in 5.55kN and displacement 0.1mm

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116 (a) (b) Figure 3 61: (a) Load displacement for P2S 3 prism, FRP debonding in 5.87kN and displacement 0.08 mm ( b) Load displacement for P2S 4 prism , FRP debonding in 5.76kN and displacement 0.08mm

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117 (a) (b) Fi gure 3 62: (a) Load displacement for P2S 5 prism, FRP debonding in 5.05kN and displacement 0.1 mm ( b) Load displacement for all P2S prisms

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118 (a) (b) Figure 3 63: (a) Top and side view for P3S prisms, (b) strain gauges location for P3S prisms

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119 (a) (b) Figure 3 64: (a) Load displacement for P3S 1 prism, FRP debonding in 6.23kN and displacement 0. 2mm ( b) Load displacement for P3S 2 prism , FRP debonding in 6.99kN and displacement 0.16mm

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120 (a) (b) Figure 3 65: (a) Load displacement for P3S 3 prism, FRP debonding in 7.03kN and displacement 0.1 5 mm (b) Load displacement for P3S 4 prism , FRP debonding in 6.58kN and displacement 0.15mm

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121 (a) (b) Figure 3 66: (a) Load displacement for P3S 5 prism, FRP debonding in 5.06kN and displacement 0.14 mm ( b) Load displacement for all P3S prisms

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122 (a) (b) Figure 3 66 a : (a) Top and side view for P4S prisms, (b) strain gauges location for P4S prisms

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123 (a) (b) Figure 3 67: (a) Load displacement for P4S 1 prism, FRP debonding in 4.90kN and displa cement 0.15 mm ( b) Load displacement for P4S 2 prism , FRP debonding in 5.46kN and displacement 0.13mm

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124 (a) (b) Figure 3 68: (a) Load displacement for P4S 3 prism , FRP debonding in 6.26kN and displacement 0.1 2 mm , (b) Load displacement for P4S 4 prism , FRP debonding in 5.68kN and displacement 0.15mm

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125 (a) (b) Figure 3 69: (a) Load displacement for P4S 5 prism, FRP debonding in 4.68 kN and displacement 0.14 mm ( b) Load displacement for all P4S prisms

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126 (a) (b) Figure 3 70 : (a) Top and side v iew for P5S prisms, (b) strain gauges location for P5S prisms

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127 (a) (b) Figure 3 71: (a) Load displacement for P5S 1 prism, FRP debonding in 5.16kN and displacement 0.08 mm ( b) Load displacement for P5S 2 prism , FRP debonding in 4.47kN and displacemen t 0.16mm

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128 (a) (b) Figure 3 72: (a) Load displacement for P5S 3 prism, FRP debonding in 6.02kN and displacement 0.2mm ( b) Load displacement for P5S 4 prism , FRP debonding in 5.96kN and displacement 0.19mm

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129 (a) (b) Figure 3 73: (a) Load displac ement for P5S 5 prism, FRP debonding in 4.74kN and displacement 0.14mm ( b) Load displacement for all P5S prisms

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130 (a) (b) Figure 3 74: (a) strain gauges results for P1S, (b) strain gauge results for P2S

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1 31 (a) (b) Figure 3 75: (a) strain gauges resu lts for P3S, (b) strain gauge results for P4S

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132 (a) Figure 3 76: (a) strain gauges results for P5S

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133 (a) (b) Figure 3 76a: (a) Strain Profile for COT prism, (b) Strain profile for P1S Prism

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134 (a) (b) Figure 3 76 b: : (a) Strain Profil e for P2S prism, (b) Strain profile for P3S Prism

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135 (a) (b) Figure 3 76c: : (a) Strain Profile for P4S prism, (b) Strain profile for P5S Prism

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136 Figure 3 77: (a) Energy dissipation for COT, (b) Energy dissipation for P1S, (c) Energy dissipation fo r P2S, (d) Energy dissipation for P3S, (e)Energy dissipation for P4 S , (F) Energy dissipation for P5S

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137 (a) (b) Figure 3 7 7 a: (a) comparing between load carrying for three phases, (b) comparing between energy dissipation for three phases 9.03 9.84 10.27 10.08 10.63 9.65 9.71 9.83 10.03 10.12 5.79 5.64 6.38 5.4 5.27 0 2 4 6 8 10 12 1 2 3 4 5 Load (kN) Grooves Uwrap SMP 1.11 0.94 1.15 1.12 1.61 0.73 0.66 0.57 0.85 0.632 0.3 0.3 0.58 0.4 0.49 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 1 2 3 4 5 Energy Dissipation (kN.mm) Grooves Uwrap SMP

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138 (a) (b) (c) (d) Figure 3 77 b : (a) concrete cylinder test, (b) concrete cylinder test,(c)concrete block grooves preparation,(d)prism grooves preparation groove

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139 (a) (b) (c) (d) Figure 3 78: (a) Gripping Details , (b) prisms FRP placement, (c) COT failure, ( d) COT prism failure Fixture P rism

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140 (a) (b) (c) (d) Figure 3 79: (a)PG1 prism failure, (b)P1G prism failure, ( c) PG2 prism failure, (d) PG2 prism failure

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141 (a) (b) (c) (d) Figure 3 80 :(a) PG3 Test setup, (b) PG3 prism failure, ( c) PG3, PG4&PG5 prisms failure,(d)PG3,PG4,PG5 and COT prisms failure Coupon

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142 (a) (b) (c) (d) Figure 3 81 : (a)PG5 prism failure, (b)PG5 prism fail ure, ( c)P1U prism failure, (d) PIU prism failure

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143 (a) (b ) (c) (d) Figure 3 82 :(a) P2U prism failure, ( b) P2U prism failure, (c)P3U prism failure,(d)P3U prism failure

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144 (a) (b) (c) (d ) Figure 3 83 : (a)P4U prism failure, (b) P4U Prism failure, (c) P5U prism failure, ( d) P5U prism failure

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145 (a) (b) (c) (d) Figure 3 84: (a)P1S prism failure, (b) P1S prism failure, (c) P2S prism failure, ( d) P2S pris m failure

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146 (a) (b) (c) (d) Figure 3 85: (a)P3S prism failure, (b) P3S prism failure, (c) P4S prism failure, ( d) P4S prism failure

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147 (a) (b) (c) (d) Figure 3 86: (a), (b), (c)&(d ) P5S prisms failure

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148 CHAPTER FOUR BEHAVIOR OF CFRP STRENGTHENED BEAMS WITH MULTIPLE GROOVES 4.1 General Overview Many parts in structure failed due to a design error, seismic, hurricane, and fire, this cause damage in structure especially beams or slab or column. Common solution retrofit structure with parts to increase structure members stiffness, a universal solution using FRP sheet for beams, slabs, and columns, even with this type of maintenance still members strengthen with FRP need maintenance. On e of strengthening beam by FRP failed due to high shear strength, will discuss in this chapter how grooves reduce shear strength at the end and improve member to carry out more load. In this chapter will discuss RC beam behavior strengthen by FRP sheets a nd subjected to two points loads, will discuss load displacement behavior and crack propagation status. Beams prepared using Portland cement have compressive strength at 28 days 18 MPa m of flexural and 6mm steel bar formed as U shape used as stirrups as showing on Fig (4 1). Beams strengthen with FRP sheet has 900x100 mm, beams have parodic grooves to figure out grooves performance on load carrying capacity for beams and how reducing cr acks in beams.

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149 4.2 Experimental programm e 4.2.1 Test Matrix Eight beams were prepared and tested, one beam without grooves (COT ). One beam strengthens by FRP sheet 900*100 mm and glued by epoxy (COT_CFRP). One beam strengthens by FRP and has three periodic grooves from each end, two inches spacing between grooves center to center, grooves terminated with the edge of FRP sheet (BG3 0). One beam strengthens by FRP sheet and has three grooves from each end, two inches spacing between grooves center to center; grooves terminated 2 inches away from FRP sheet edge (BG3 2). One beam strengthened by FRP sheet and has three grooves from each end. Two inches spacing between grooves center to center, grooves terminated 4 inches away from FRP sheet edge (BG3 4), one bea m strengthens by FRP sheet, and has distributed grooves two inches spacing between grooves and terminated at FRP sheet edge BDG 0. One beam strengthens by FRP sheet and has distributed grooves two inches spacing between grooves and terminated at 2 inch es form FRP sheet edge BDG 2. One beam strengthens by FRP sheet and has distributed grooves two inches spacing between grooves and terminated at 4 inches form FRP sheet edge BDG 4. Grooves were 15mm depth, 20mm width and along beam width, 100mm grooves p repared by concrete saw instrument.

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150 4.2.2 Materials Concrete mixed by using mix design as shown in Table 3 2, using Portland cement, sand, aggregate and water. Steel cage has two reinforcement bars at the bottom and bends 90 degrees from end, 6 mm reinforc ement bar formed as U shape used for stirrups with spacing 3 in the center to center in mid span and two inches center to center at the edge of the steel cage, as shown in attached pictures. FRP glued by epoxy Mbrace 4500 hardener and resin with mix ratio 1:3 and left seven days for curing. Concrete cylinders were prepared while pouring concrete for beams and tested in 7 days and 28 days age , the compressive strength was 18.5 MPa as shown in Table 3 3. 4.2.3 Beams preparation Beams prepared and cast in t he laboratory, beams cast inside a metal frame with dimension 1200 mm (47 in) length, 100 mm (4 in) width, and 165 mm (6.5 in) height. Steel cage placed inside forms and elevated by spacer 25 mm thickness for concrete cover, cement, aggregate, sand, and th e water mixed by an electrical mixer and poured inside metal forms. Beams left in curing room for 28 days, then grooves created along the bottom face of beams by using an electrical saw. Faces smoothed by the electric grinder and prepared for strengthenin g. FRP sheet 900mm (36) in length by 100mm (4in) width, epoxy hardener and resin mixed with ratio 1:3 prepared to glue FRP to beam. Beams left seven days for curing. Strain gauges glued on FRP, three

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151 strain gauges from each side spaced by 50 mm (2in) from center to center, for beams have grooves septic tape fixed on the edge of the beam to avoid epoxy spill from grooves. 4.2.4 Test setup Beams setup and supported with span 1000 mm by using two rigid frames, two plates placed between the beam and framed to r educe load concertation at support. Two point load metal frame fixture with spacing 450mm between two point load used for test purpose with a load cell to measure applied force through test progress. DIC camera used and focused close on supporting side to monitoring cracks propagation through test progress. Three strain gauges were used at each edge of a beam and glued from termination end of FRP sheet spaced 50mm (2 in) center to center between each strain gauge. PI gauge fixed at the mid span of beam 2 5.4 mm (1 in) below the top face of a beam to measure compression strain and other PI gauge fixed 25.4 mm (1in) above bottom face of the beam to measure tensile strain in the beam. Linear potentiometers gauge used to measure displacement in a beam through test progress, all gauges connected to data acquisition device to record the result and save it in the computer. MTS machine 222 kN ( 50 kips) was used to apply load with rate 2 mm/min for all beams test.

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152 4.3 Results and discussion Table ( 4 2 ) showing su mmary test result for all RC beams, table (4 1) showing beams behavior through test progress, will discuss improvement in load carrying capacity, beam strain , and CFRP strain. 4.3.1 Load carrying capacity the load carrying capacity results obtained from test results for eight beams as shown below: The first beam was COT (without CFRP and grooves) beam, tested with four point load; a two point load applied on mid span of beam 225mm (8.8 in) from point load to mid span of the beam, load gradually increase d with rate 2 mm/min until beam failure. Figure (4 7) showing load displacement trend, in the early stage of test progress flexural crack, appeared in load 10 kN and flexural shear crack propagated at load 30 kN then beam failed at 47.2 kN, as shown in Fi gure (4 7). COT_CFRP ( beam without grooves and FRP sheet strengthened). FRP sheet 900mm length by 100mm width , glued to the beam and tested load rate 2 mm/min ; flexural crack appeared at load 20 kN then shear crack propagated at 45kN beam , then failed at l oad 57.1kN by concrete crushed in mid span, then CFRP plate peeled off, FRP showed increasing in load carrying 21.2% in comparing with COT beam. BG3 0 (beam has three grooves terminated with the end of FRP). Grooves 20mm width, 15mm depth, and 100 mm width with spacing 50 mm center to center, created in the bottom of concrete cover of the beam filled with epoxy and tested with 2mm/min load rate flexural

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153 crack propagated at load 23 kN, then flexural shear crack propagated at load 35.9 kN, then concrete crush ed and FRP peeled off. Beam failed at load 64.9 kN as shown in Figure (4 17), adding three grooves increased load carrying capacity 38 % in comparing with COT beam. BG3 2 (beam has three grooves terminated 2 in away from the end of FRP). Grooves 20mm width , 15mm depth and 100 mm width created in the concrete cover of the beam, fil led with epoxy and tested with load rate (2mm/min), flexural crack propagated at load 31 kN, then flexural shear crack propagated at load 49 Kn. Concrete crushed, and FRP peeled of f, and the beam failed at load 64.2 kN as shown in Figure (4 19), adding three grooves increased load carrying capacity 36.8 % in comparing with COT beam. BG3 4 (beam has three grooves terminated 4in away from the end of FRP). Grooves 20mm width, 15mm dept h, and 100 mm width created in the concrete cover of the beam, filled with epoxy and tested with load rate (2mm/min), flexural crack propagated at load 22 kN, then flexural shear crack propagated at load 35 kN. Concrete crushed, and FRP peeled off and the beam failed at load 63.9 kN, adding three grooves increased load carrying capacity 35.9 % in comparing with COT beam. BDG 0 (beam has distributed grooves terminated with the end of FRP). Grooves 20mm width, 15mm depth and 100 mm width created in the concre te cover of the beam, filled with epoxy and tested with load rate (2mm/min), flexural crack propagated at load 29.2 kN, flexural shear crack propagated at load 61.2 kN. Concrete crushed, and FRP peel off and beam failed at load 72.1 KN, adding distributed grooves with spacing 50mm from center to center of groove increased load carrying capacity 53.3 % in comparing with COT beam.

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154 BDG 2 (beam has distributed grooves terminated 2 in away from the end of FRP). Grooves 20mm width, 15mm depth , and 100 mm width cr eated in the concrete cover of the beam, filled with epoxy and tested with load rate (2mm/min), the a flexural crack propagate d at 25 kN then shear crack propagated at load 61.2 kN. Concrete crushed, and FRP peeled off and beam failed at load 69.8 kN, addi ng distributed grooves with spacing 50mm from center to center of groove increased load carrying capacity 48 % in comparing with COT beam. BDG 4 (beam has distributed grooves terminated 4 in away from the end of FRP). Grooves 20mm width, 15mm depth and 100 mm width created in the concrete cover of the beam, filled with epoxy and tested with load rate (2mm/min), flexural shear crack propagated at load 22.9 kN, and flexural shear crack propagated at 60.2 kN. Concrete crushed, and FRP peeled off and beam faile d at load 65.3 kN, adding distributed grooves with spacing 50mm from center to center of groove increased load carrying capacity 38.9 % in comparing with COT beam. 4.3.2 Failure mode Beam test results are showing improvement in load carrying capacity and f ailure mode for beams. For COT beam test, a flexural crack appeared early at 10 kN, and shear flexural crack began from support and propagated to both point load at 30 kN in each side of the beam. For COT_FRP beam with FRP flexural shear cracks propagated at load 20 kN, then concrete crushed near the top of mid span of the beam, this caused peeling off FRP sheet and

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155 adhesive, however this type of failure it a common failure for RC beams strengthened by FRP sheet. For BG3 beams and from tests results showing a combination of grooves and FRP sheet, reduced flexural cracks in beams with improvement in load displacement capacity, that happened because grooves reduced interfacial shear stress in adhesive, and peeling off concrete cover happened for thicker of th e adhesive layer. For BDG beams and from test results showing grooves improved load displacement capacity and reduced flexural cracks in beams, grooves and FRP sheets developed beam stiff and failure bega n in the weakest point in the beam (strengthen zone near support). 4.3.3 Comparison in f ailure mode for concrete blocks and beams This comparison based on failure mode of concrete blocks has grooves and beams, most prisms failed on FRP damage due to int erlock between epoxy and concrete blocks, some prisms failed on FRP rupture and concrete spilling because concentration interfacial stress between epoxy and concrete block exceed compressive strength for concrete blocks. Prisms have four grooves, and five grooves failed by FRP ruptured because increasing grooves reduced stress concentration over grooves, so the interfacial shear stress in groves lower than concrete compressive strength or equal to compressive strength, in this case, some cracks appeared in locations of grooves. Beams has three grooves failure mode differ than concrete blocks with three grooves, spilling in concrete cover for beams due to interfacial shear stress exceed compressive strength of

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156 concrete with improvement in load carrying capaci ty for beam comparing with beams without grooves. FRP is not ruptured comparing with concrete blocks because FRP sheet bounded by epoxy with concrete. Damage in concrete beams happened at a location of applied two points loads because concrete failed befor e debonding of FRP. For beams has continuous grooves comparing with prisms has four groves and more, showed same failure mode, beams failed without spilling in concrete cover due to reducing in interfacial shear stress between concrete and FRP, cracks app eared at the location for grooves and propagated toward point load location. Beams have continued grooves failure happened in the unstrengthen zone (between FRP termination edge and support). This type of failure happened because grooves counts and thickne ss of epoxy made beams to stiff and fai lure begin in the unstrengthen zone (zone did not cover by epoxy and FRP), with improvement in load carrying capacity comparing with beam without grooves. FRP is not ruptured comparing with concrete blocks because FRP sheet bounded by epoxy with concrete. Damage in concrete beams happened at a location of applied two points loads because concrete failed before debonding of FRP. 4.3.4 Crack propagation Figure (4 40) explain crack propagations with the applied load for beams has three grooves created at 0 inches from termination edge of FRP, and beams have continued grooves created at 0 inches from termination edge of FRP, in this figure focused on one main propagated crack in the beam. Continues grooves showed the mai n crack propagated at load

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157 level 61.2 kN, and propagation increased with applied load until failure, compared with the beam with three grooves showed crack propagated at load level 35.9 kN, and continued until beam failure. This confirmed creating grooves in beam concrete cover reduced flexural cracks in compare with control beam without grooves. Improvement in reducing cracks depends on grooves counts and location from termination edge of FRP.

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158 ( a) (b) Figure 4 1 : (a)Reinforcemen t Details for COT beam without FRP, (b) Reinforcement Details for COT _ FRP and without grooves

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159 (a) (b) Figure 4 2 : (a) Reinforcement Details for BG3 0 beam, (b) crack pattern for BG3 2 beam

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160 ( a) (b) Figure 4 3 :(a) Reinforcement Details for BG3 4 beam with FRP, (b) crack pattern for B DG 0 beam with FRP

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161 (a) (b) Figure 4 4 :(a) Reinforcement Details for B D G 2 beam with FRP, (b) crack pattern for B DG 4 beam with FRP

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162 Figure 4 5 : Beams Test setup

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163 Table 0 1 : Summary Beam s Test behavior BeamNO. Load level (kN) 10 20 20 30 30 40 40 50 50 60 >60 COT Flexural cracks at 10 kN Flexural cracks increase and propagate Flexural Shear cracks propa gate at 30 kN Concrete crush and beam fail at 47.2 kN ------COT_FRP Flexural cracks at 20 kN Flexural cracks increase and propagate flexural cracks propagate Shear cracks propagate at 45 kN and vertical cracks near fixed support at 52kN FRP debond at 57.1 kN BG3 0 ---Flexural cracks at 23 kN Flexural Shear cracks propagate at 35.9 kN Flexural Shear cracks increase and propagate Cracks propagate CFRP and concrete cover peeled off at 64.9 kN BG3 2 ------Flexural cracks at 31 kN Flexural Shear cracks propagate at 49 kN Cracks propagate FRP and concrete cover peeled off at 64.2 kN BG3 4 ---Flexural cracks at 22 kN Flexural shear cracks propagate 35 kN Flexural Shear cracks increase and propagate Cracks propagate FRP and concrete cover peel ed off at 63. 9 kN BDG 0 ---Flexural cracks at 29.2 kN Flexural cracks propagate Flexural cracks propagate Flexural shear cracks propagate 61.2 kN FRP and concrete cover peeled off at 72.1 kN BDG 2 ---Flexural cracks at 25 kN Flexural cracks propagate Flexural cracks propagate Flexural shear cracks propagate 61.0 kN CFRP and concrete cover debond at 69.8 kN BDG 4 ---Flexural crack appeared at 22.9 Flexural cracks increase and propagate Flexural cracks increase and propagate Shear cracks propagate a t 60.2 kN Failure due to shear cracks and concrete crush at 65.3 kN

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164 Table 0 2 : Summary beams test results Spec. No. Strengthening condition No.of Grooves Pu Kn (Kip ) Displacement m m (in) COT Unstrengthened 47.2 (10.58) 8. 0 ( 0.3 1 ) COT_CFRP Strengthened 57.1 ( 12.83) 7.2 (0.28) BG3 0 Strengt hened 3 Grooves 64. 9 (14.59) 6.8 (0.26) BG3 2 Strengthened 3 Grooves 64. 2 (14.38) 7.4 (0.29) BG 3 4 strengthened 3 Grooves 63. 9 (14.18) 8.59 (0.33) BDG 0 Strengthened Distributed Grooves 72.1 (16.18) 3.5 (0.13) BDG 2 Strengthened Distributed Grooves 69.8 (15.69) 6.93 (0.27) BDG 4 Strengthened Distributed Grooves 65.3 (14.69) 4.1 (0.16)

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165 (a) (b) Figure 4 6 : (a) Test result COT beam load displacement (b) PI gauges test result for COT beam

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166 (a) (b) (c) (d) (e) Figure 4 7 : COT beam failure flexural crack appeared at 10 K N and propagate d Flexural Shear cracks propagate at 30 kN Concrete crush , and beam fail at 47.2 Kn , (e) crack pattern for COT beam

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167 (a) (b) Figure 4 8 (a) Test result COT_CFRP beam load displacement (b) PI gauges test result for COT_CFRP beam

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168 ( a) (b) Figure 4 9 : (a) strain gauge result for COT_CFRP left side, (b) strain gauge result for COT_CFRP right side

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169 (a) (b) Figure 4 1 0 : (a) S train Gauges profile for COT_CFRP , (b) Crack Pattern for COT_CFRP

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170 (10 kn) 17.5% Pu (15 kn) 26.3% Pu (22.4 kn) 39% Pu (33.9 kn) 59.4% Pu ( 53.3 kn) 93.3.8% Pu ( 57.1 kn) 100% Pu Figure 4 1 1 : DIC capture for crack propagation in different load lev el for COT_CFRP

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171 (a) (b) (c) (d) (e) (f) Figure 4 1 2 : COT_CFRP beam failure flexural crack appeared at 2 0 KN and propagate d Flexural Shear cracks propagate at 45 kN Concrete crush , and beam fail at 57.1 kN

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172 (a) (b) Figure 0 1 3 : (a) load displacement test result BG3 0 beam (b) PI gauges test result for BG3 0 beam 0 10 20 30 40 50 60 70 80 -0.0025 -0.0015 -0.0005 0.0005 0.0015 0.0025 Load (kN) Strain B1-T B2-C

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173 (a) (b) Figure 0 1 4 : (a) strain gauge result for BG3 0 left side, (b) strain gauge result for BG3 0 right side

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174 (a) ( b) Figure 0 1 5 : (a) Strain Gauges profile for BG3 0 , (b) Crack pattern for BG3 0

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175 Exx (23) kn 35% Pu Exx (53) kn 81.5% Pu Exx (59.5) kn 91.6% Pu Exx (62) kn 95.6% Pu Exx(64) kn 99% Pu Exx(64.9) kn 100% Pu Figure 4 1 6 : DIC capture for crack propagation in different load level for BG3 0

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176 (a) (b) (c) (d) (e) (f) Figure 4 17 : BG3 0 beam failure flexural crack appeared at 2 3 KN and propagate d Flexural Shear cracks propagate at 53.9 kN Concrete crush , and beam fail at 64 .9 kN

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177 (b) Figure 4 18 : (a) load displacement result for BG3 2 beam, (b) PI gauges results for BG3 2

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178 (a) (b) (C) (D) ( e) Figure 4 19 : BG3 2 beam failure flexural crack appeared at 31 KN and propagate d Flexural Shear cracks propagate at 49 kN Concr ete crush , and beam fail at 64.2 K N , (e) Crack pattern for BG3 2

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179 (a) (b) Figure 0 2 0 : (a) load displacem e nt for BG 3 4 , (b) PI gauges result for BG 3 4 beam 0 10 20 30 40 50 60 70 80 -0.0025 -0.0015 -0.0005 0.0005 0.0015 0.0025 Load (kN) Strain B1-T B2-C

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180 (a) (b) Figure 4 2 1 : (a) strain gauges results for BG3 4 left side, (b) Strain gauge results for BG3 4 right side

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181 (a) (b) Figure 0 2 2 : (a) Strain gauge profile for BG3 4 , (b) crack pattern for BG3 4 Beam

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182 E xx ( 2 2.53) k N 35 % Pu Exx ( 3 5.25 ) kN 55.1 % Pu Exx ( 41 .53 ) kN 6 5% Pu Exx ( 50.12 ) kN 78 % Pu Exx (63.69 ) kN 99.9% Pu Exx (63. 9 ) kN 100% Pu Figure 4 2 3 : DIC capture for BG3 4 crack propagation in different load level

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183 (a) (b) (c) (d) (e) (f) Figure 4 2 4 : BG3 4 beam failure flexural crack appeared at 22 KN and propagate d Flexural Shear cracks propagate at 35 kN Concrete crush , and beam fail at 63.9 kN

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184 (a) (b) Figure 4 2 5 : (a) load displacement for BDG 0, (b) PI gauges result for BDG 0 beam

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185 (a) (b) Figure 0 2 6 : (a) Strain gauges results for BDG 0 left side, (b) strain gauges results for BDG 0 righ t side

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186 (a) (b) Figure 0 27 : (a) Strain gauges profile results for BDG 0 , (b) crack pattern for BDG 0 beam

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187 Exx (33.2) kN 45.9% Pu Exx (57.1) kN 79% Pu Exx (70.7) kN 9 8 % Pu Exx (71.2) kN 98.7 % Pu Exx (71.5) kN 99% Pu Exx ( 72.1) kN 100% Pu Figure 4 28 : DIC capture for crack propagation in different load level for BDG 0

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188 (a) (b) (c) (d) (e) (f) Figure 4 29 : BDG 0 beam failure flexural crack appeared at 29 .2 KN and propagate d , Flexural Shear cracks propagate at 61.2 k N Concrete crush , and beam fail at 72.1 kN

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189 (a) (b) Figure 4 3 0 : (a) Load displacement for BDG 2, (B) PI Gauge results for BDG 2

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190 (a) (b) Figure 0 3 1 : (a) Strain gauge results for BDG 2 Left side, (b) Strain gauge results for BDG 2 right side

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191 (a) (b) Figure 0 3 2 : (a) strain gauge result profile for BDG 2 beam, (b) Crack pattern for BDG 2

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192 Exx (61) kN 87% Pu Exx (64) kN 92% Pu Exx (68) kN 97% Pu Exx (69) kN 9 8.7 % Pu Exx (69. 5 ) kN 99 % Pu Exx ( 69.8 ) kN 100 % Pu Figure 4 3 3 : DIC capture for crack propagation in different load level for BDG 2

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193 (a) (b) (c) (d) (e) (f) Figure 4 3 4 : BDG 2 beam fail ure flexural crack appeared at 25 KN and propagate d , Flexural Shear cracks propagate at 61.0 kN Concrete crush and beam fail ed at 69.8 kN

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194 (a) (b) Figure 0 3 5 : Load displacement results for BDG 4, (b) PI gauges test result for BDG 4 beam

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195 (a) (b) Figure 0 3 6 : (a) strain gauge result for BDG 4 b eam left side, (b) Strain gauge result for BDG 4 beam right side

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196 (a) (b) Figure 0 37 : (a) strain gauge profile for BDG 4 beam , (b) crack pattern for BDG 4 Beam

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197 Exx (22.9) kN 35% Pu Exx (50) kN 76.5% Pu Exx ( 58 ) kN 88.8 % Pu Exx (60 .2 ) kN 9 2 . 0 % Pu Exx (65) kN 99% Pu Exx (65.3) kN 100% Pu Figure 4 38 : DIC capture for crack propagation in different load level for BDG 4

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198 (a) ( b) (c) (d) (e) (f) Figure 4 39 : BDG 4 beam failure flexural crack appeared at 22.9 KN and propagate d , Flexural Shear cracks propagate at 60 .2 kN Concrete crush , and beam fail at 65.3 kN

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199 (a) (b) Figure 0 40: (a) Crack propagation for BDG 0, (b) Crack propagation for BG3 0

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200 CHAPTER FIVE SUMMARY AND CONCLUSION This research focuses on rehabilitation of structural member by using FRP. Nowadays retrofit structural member by FRP and epoxy is a fantastic s olution for structure rehabilitation for FRP properties. FRP has low weight, high strength, an anisotropic material, durable material for construction, chemical resistance, high resistance to corrosion, fast cure, high strength resistance, low density, hig h elastic, low conductivity, high fatigue resistance and high impact resistance (Wang, Dai, & Harries, 2013). However, it does not need special tools for applying; it needs just cleaning the surface and making sure it is dry and glued to the surface by epo xy. FRP performance depends on bond stress between concrete members and FRP, as early mentioned in the literature review, many researchers studied the mechanism of bond behavior between FRP, adhesive and concrete. Concrete strength, thickness, the adhesive amount and concrete surface properties, all these conditions effect on bond stress between FRP and concrete. This research focuses on improving bond stress between FRP and concrete by modifying the concrete surface. Chapter three is explaining three phase s of modified surface of concrete blocks which are showing improvement in test results:

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201 Bond strength depends on many parameters, but according to this research changing properties for concrete block surface effects on bond stress between FRP and conc rete blocks. Creating grooves in the contact surface between FRP and concrete reduces interfacial strain and lead to increasing the load carrying capacity. Creating grooves reduces interfacial shear stress between FRP, adhesive and concrete block surface. Creating grooves changes the failure mode behavior for the concrete member from the debonding for unmodified concrete surface to FRP rupture or concrete crush for modified surface by grooves. Creating grooves leads to increase the load carrying capacity, and the increasing percentage depends on grooves numbers, a spacing between grooves, and grooves dimensions. Creating grooves increases energy dissipation, and the increase depends on grooves numbers and dimensions. Grooves are the best option to retrofit members; they increase member capacity and stiffness. Adding grooves in beams improves the load carrying capacity of the beam, the improvement depends on grooves numbers and locations from termination end of FRP. Adding grooves in beams increases beam stiffness and reduces displacement in mid span of a beam.

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202 Adding grooves in beams reduces flexural cracks in beams and failure occurs in the weak zone. Phase II concrete blocks strengthened by U wra p is showing improvement in load carrying capacity and failure mode: Adding U wrap shows improvement in load carrying capacity for concrete blocks. Improvement in load carrying capacity for concrete blocks strengthens by U wrap depends on the number of U wraps and locations. Adding U wrap over FRP glued to concrete reduces strain by distributing the stain over U wrap. Adding U wrap over FRP glued to concrete members increases energy dissipation. Adding U wrap over FRP changes failure mod e from debonding for members without U wrap to FRP rupture for members strengthened by FRP and U wrap. Comparing this phase with some topic use steel plate instead U wrap, this showed improvement in carrying capacity because CFRP U wrap will fully attach t o CFRP sheet comparing with steel plate. Use U wrap will reduce the cost of comparing with steel plate, U wrap need special tools and professional technician comparing with steel plate. Phase III concrete blocks strengthened by FRP, epoxy, and SMP is showing improvement in failure mode: concrete blocks strengthened by epoxy and SMP show improvement in failure mode comparing with epoxy failure.

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203 Load carrying capacity reduces in comparing with plain surface blocks because the combination of epoxy and SMP reduces epoxy area and SMP has low strength properties in comparing with epoxy properties. Adding SMP increases the energy dissipation in comparing with plain surface blocks. Blocks strengthened by epoxy and SMP show high displaceme nt in comparing with other phases. The failure mode for blocks strengthened by epoxy and SMP is FRP debonding for all specimens. In comparing with other phases, the FRP ruptures or ruptures with cracks in concrete. Beams strengthened by FRP and groove s shows improvement in load carrying capacity, strain reducing and failure mode: Increasing in load carrying capacity depends on grooves quantity and location from termination point of FRP. Displacement reduces in mid span of the beam. The f ailure mode for beams without grooves is debonding, but the failure mode for modified beams by FRP and grooves is crashing in concrete and FRP peeling off. Flexural cracks reduce for beams strengthened by FRP and grooves in comparing with COT beam.

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204 Re commendation for future research I recommend some topic to develop this research for future studying as show n below: Finite element analysis for interface stress between epoxy and concrete surface. Create new phase using steel plate instead of CFRP and com pare the result with U wrap phase .

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205 References 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. Täljsten, B. (1997). Defining ancho r lengths of steel and CFRP plates bonded to concrete. International Journal of Adhesion and Adhesives, 17(4), 319 327. Smith, S. T., & Teng, J. G. (2001). Interfacial stresses in plated beams. Engineering structures , 23(7), 857 871. Teng, J. G., Yuan, H., & Chen, J. F. (2006). FRP to concrete interfaces between two adjacent cracks: Theoretical model for debonding failure. International Journal of Solids and Structures, 43(18), 5750 5778. Bizindavyi, L., & Neale, K. W. (1999). Transfer lengths and bo nd strengths for composites bonded to concrete. Journal of composites for construction, 3(4), 153 160. Ebead, U. A., Neale, K. W., & Bizindavyi, L. (2004, December). On the interfacial mechanics of FRP strengthened concrete structures. In FRP Composite s in Civil Engineering CICE 2004: Proceedings of the 2nd International Conference on FRP Composites in Civil Engineering CICE 2004, 8 10 December 2004, Adelaide, Australia (p. 351). Taylor & Francis. Bakis, C. E., Ganjehlou, A., Kachlakev, D. I., Schup ack, M., Balaguru, P. N., Gee, D. J., ... & Kliger, H. S. ( 2002). Guide for the design and construction of externally bonded FRP systems for strengthening concrete structures. Reported by ACI Committee, 440(2002). Sayed Ahmed, E. Y., Bakay, R., & Shriv e, N. G. (2009). Bond strength of FRP laminates to concrete: a state of the art review. Electronic Journal of structural engineering, 9(1), 45 61. Properties of FRP Materials for Strengthening. Intern ational Journal of Innovative Science, Engineering & Technology, 1 (9). Kim, Y. J., LaBere, J., & Yoshitake, I. (2013). Hybrid epoxy silyl modified polymer adhesives for CFRP sheets bonded to a steel substrate. Composites Part B: Engineering, 51, 233 2 45.

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206 De Lorenzis, L., & Teng, J. G. (2007). Near surface mounted FRP reinforcement: An emerging technique for strengthening structures. Composites Part B: Engineering, 38(2), 119 143. Spacone, E., Filippou, F. C., & Taucer, F. F. (1996). Fibre beam colum n model for non linear analysis of R/C frames: Part I. Formulation. Earthquake engineering and structural dynamics, 25(7), 711 726. Kim, Y. J., Siriwardanage, T., & Kang, J. Y. (2014). Debonding Mitigation of CFRP Strengthened Steel Beams with Silyl M odified Polymer and CFRP Wrap Anchorage. Journal of Composites for Construction, 19(1), 04014022. Carse, A., Spathonis, M. J., Chandler, M. L., Gilbert, M. D., Johnson, M. B., UWS, A. J., & Pham, L. (2002). Review of strengthening techniques using exte rnally bonded fiber reinforced polymer composites. CRC for Construction Innovation, Brisbane . Tabbara, M., Chatila, J., & Awwad, R. (2005). Computational simulation of flow over stepped 15. pillways. Computers & structures, 83(27), 2215 2224. Bizindavy i, L., & Neale, K. W. (1999). Transfer lengths and bond strengths for composites bonded to concrete. Journal of composites for construction , 3 (4), 153 160. Triantafillou, T. C., & Plevris, N. (1992). Strengthening of RC beams with epoxy bonded fibre composite materials. Materials and Structures , 25 (4), 201 211. Matana, M., Nanni, A., Dharani, L., Silva, P., & Tunis, G. (2005, December). Bond performance of steel reinforced polymer and steel reinforced grout. In Proceedings of the International Symp osium on Bond Behaviour of FRP in Structures, BBFS (pp. 125 132). Rasheed, H. A., & Pervaiz, S. (2002). Bond slip analysis of fiber reinforced polymer strengthened beams. Journal of Engineering Mechanics, 128(1), 78 86. Nguyen, D. M., Chan, T. K., & Ch eong, H. K. (2001). Brittle failure and bond development length of CFRP concrete beams. Journal of Composites for Construction, 5(1), 12 17. Biscaia, H. C., Chastre, C., & Silva, M. A. (2012). Double shear tests to evaluate the bond strength between GF RP/concrete elements. Composite Structures, 94(2), 681 694. Debernardi, P. G., Guiglia, M., & Taliano, M. (2011). Shear strain in B regions of beams in service. Engineering Structures, 33(2), 368 379.

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207 Zhao, M., & Ansari, F. (2004, August). Bond proper ties of FRP fabrics and concrete joints. In 13th world conference on earthquake engineering, Vancouver, BC, Canada, Paper (No. 35). Nakaba, K., Kanakubo, T., Furuta, T., & Yoshizawa, H. (2001). Bond behavior between fiber reinforced polymer laminates and concrete. Structural Journal, 98(3), 359 367. Li, X., Gu, X., Song, X., Ouyang, Y., & Feng, Z. (2013). Contribution of U shaped strips to the flexural capacity of low strength reinforced concrete beams strengthened with carbon fibre composite sheet s. Composites Part B: Engineering, 45(1), 117 126. Mohammadi, T. (2014). Failure mechanisms and key parameters of FRP debonding from cracked concrete beams (Doctoral dissertation, Marquette University). Baky, H. A., Ebead, U. A., & Neale, K. W. (2007). Flexural and interfacial behavior of FRP strengthened reinforced concrete beams. Journal of Composites for Construction, 11(6), 629 639. Kim, Y. J., & Brunell, G. (2011). Interaction between CFRP repair and initial damage of wide flange steel beams sub jected to three point bending. Composite Structures, 93(8), 1986 1996. Khalifa, A., Gold, W. J., Nanni, A., & MI, A. A. (1998). Contribution of externally bonded FRP to shear capacity of RC flexural members. Journal of composites for construction, 2(4) , 195 202.