Citation
Effect of differential settlement on the behavior of reinforced concrete beams strengthened with carbon fiber reinforced polymer

Material Information

Title:
Effect of differential settlement on the behavior of reinforced concrete beams strengthened with carbon fiber reinforced polymer
Creator:
Al-Kubaisi, Aiham N.
Place of Publication:
Denver, CO
Publisher:
University of Colorado Denver
Publication Date:
Language:
English

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:
Li, Chengyu
Committee Members:
Kim, Yail Jimmy
Chang, Nien-Yin

Notes

Abstract:
Strengthening reinforced concrete members with carbon fiber reinforced polymer (CFRP) is widely used because it enhances the member’s capacity. Although extensive research has been conducted thus far. limited information exists when a CFRP-strengthened member interact with soil settlement. This research discusses soil-structure interaction with an emphasis on the effect of the differential settlement on the behavior of reinforced concrete beams strengthened with externally bonded (EB) CFRP sheets and near-surface-mounted (NSM) CFRP strips. In the first part of the experiment, the result of twenty-one beams are tested, including three supporting conditions. One side of the beam is fixed, and the other side has a roller so that differential settlement is simulated. Seven beams are tested under the condition of rigid support, seven under the condition of dry sand, and seven beams under the condition of submerged sand. Three unstrengthened beams are tested for comparison; nine beams strengthened with EB CFRP sheet, and nine beams strengthened with NSM CFRP strips. In the second part of the experimental work, ten continuous beams are tested under the same three different support conditions, but without fixed support including the same strengthening scheme. Monotonic/cyclic loadings are applied until the strengthened beams fail and their behavior is measured. The beams with CFRP strengthening show higher load carrying capacity and higher energy dissipation than those without CFRP strengthening. A relationship between the failure characteristics of the strengthened beams and the type of soil is established. The failure mode of the beams is controlled by the presence of CFRP sheets or CFRP strips.

Record Information

Source Institution:
University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
Copyright Aiham N. Al-Kubaisi. Permission granted to University of Colorado Denver to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

Downloads

This item is only available as the following downloads:


Full Text

PAGE 1

EFFECT OF DIFFERENTIAL SETTLEM ENT ON THE BEHAVIOR OF REINFORCED CONCRETE BEAMS STRENGTHENED WITH CARBON FIBER REINFORCED POLYMER b y A IHAM N. Al K UBAISI B.S., Nahrain University, 20 08 A thesis submitted to the Faculty of the Graduate School of th e University of Colorado in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering 2016

PAGE 2

ii This thesis for the Master of Science degree by A iham N. A l Kubaisi has been approved for the Civil Engineering b y Ch engyu Li , Chair Yail Jimmy Kim Nien Yin Chang December 1 7 , 2016

PAGE 3

iii Al Kubaisi, Aiham N. (M.S. , Civil Engineering) Effect of Differential Settlement on the Behavior of Reinforced Concrete Beams Strengthened with Carbon Fiber Reinforced Polymer Thesis directed by Professor Yail Jimmy Kim A BSTRACT Strengthening reinforced concrete members with c arbon f iber reinforced p olymer (CFRP) is widely used because it enhances the capacity. Although extensive research has been conducted thus far . limited information exists when a CFRP strengthened member interact with soil settlement. This research discusses soil structure interaction with an emphasis on the effect of the differential settlement on the behavior of reinforced concrete beams strengthened wi th externally bonded (EB) CFRP sheets and near surface mounted (NSM) CFRP strips . In the first part of the experiment, the result of twenty one beams are tested, including three supporting conditions. O ne side of the beam is fixed , and the other side has a roller so that differential settlement is simulated . S even beams are tested under the condition of rigid support, seven under the condition of dry sand , and seven beams under the condition of submerged sand . T hree unstrengthened beams are tested for compa rison ; nine beams strengthened with EB CFRP sheet, and nine beams strengthened with NSM CFRP strips. In the second part of the experimental work, ten continuous beams are tested under the same three different support conditions , but without fixed support i ncluding the same strengthening scheme. Monotonic /cyclic loading s are applied until the strengthened beams fail and the ir behavior is measured.

PAGE 4

iv The beams with CFRP strengt hening show higher load carrying capacity and higher energy dissipation than those without CFRP strengthening. A relationship between the failure characteristics of the strengthened beams and the type of soil is established . The failure mode of the beams i s controlled by the presence of CFRP sheets or CFRP strips . The form and content of this abstract are approved. I recommend its publication. Approved: Jimmy Kim

PAGE 5

v DEDICATION I dedicate this work to my mother and my family who supported me throughout my l ife and motivated me to challenge the difficulties of life and become the person who I am. I also dedicate this work to every brave Iraqi people who fight for my country and for freedom of people there.

PAGE 6

vi ACKNOWLEDGEMENTS This degree was a long journey f or me with a lot of new experiences of different kinds of stress and struggling. advice of many people. This thesis is a result of all efforts , discussions, and research of the group of pe ople who stand with me to make this work success and me . I am thankful for this opportunity of being in University of Colorado Denver / United States and get to know all those great people, peoples who effect my life and shape it to be better. On behalf of this, I must also acknowledge all those people whom I have them during this journey and who have led me to the path that I chose. First, I must take to opportunity to acknowledge and thank my mother for her endless love and support. For keeping in touch wi th me regardless of long distance and had a situation in my country. She prays for me and ha s implanted in m y high work ethics and confidence to prosper. I would also like to thank my brothers and sister for standing by my mother when I am gone and for sup porting me . I must acknowledge my advisor , Professor Yail Jimmy Kim with appreciation , for his patience, thoughts , and guidance that develop my knowledge and make my goals true . Also, I would like to acknowledge my geotec hnical advisor P rofessor Nien Yin Chang f or his generous encouragment and support. With much r espect, I would like to thank Dr. Chengyu Li for teaching me some classes and for being a member o f my committee I would like to thank my fellow student at the University of Colorado Denver for their friendship, support, encouragement, and assistance. Especially Ahmed Ibrahim, Ibrahim B um adian , Mohamed Bihiri , Thush a ra Siriwardanage , Abd A llah , and all others .

PAGE 7

vii I am also thankful to the technical team of the Faculty of Enginee ring Department, who helped me complete the experimental work and sharing ideas, discussion , and friendship. I would like to thank all the members of our lab Tom, Jack, Peter, and Christin , I would like to thank the Iraqi and Libyan society in Denv er for being great friends of mine and sharing good times and for their support and encouragement . Finally, I would like to thank and acknowledge t he Higher Committee for Education Development in Iraq (HCED) for sponsor ing me and nominating me to study abo ard and supporting me with a fully funded scholarship.

PAGE 8

viii TABLE OF CONTENTS I INTRODUCTION 1 1.1 General 1 1.2 Research Significance . . .. 2 1.3 Objec tives . 3 1.4 Scope ... . 3 1.5 Thesis outline 4 II LITERATURE REVIEW 6 2.1 Introduction .. 6 2.2 Background ... 6 2.3 Strengthen ing r einforced c oncrete s tructures . 7 2.4 Fiber r einforced p olymer (FRP) .. . . 9 General . 9 FRP types and properties ... .. 10 FRP technique 11 FRP ap plications 12 Failure mode of EB and NSM systems ... . .. 13 Previous study and r esearch on EB and NSM FRP strengthening system s . 14 2.5 Soil .. .. .. . 16 2.5.2 Soil laboratory test . 17 2.5.2.1 Sieve analysis .. .. . . 17 2.5.2.2 Plate test . 1 8 2.5.2.3 Determination of a water content ratio to get more settlement for experiment . 19

PAGE 9

ix III BEHAV IOR OF RC BEAMS STRENGTHENED WITH CFRP SHEETS AND STRIPS SUBJECTED TO DIFFERENTIAL SETTLEMENT OF SOIL 36 3.1 General overview .... .. .. 36 3.2 Experimental program . 37 Test specimens .. . 37 Materials .. 38 3.2.2.1 Concrete .. ... 38 3.2.2.2 Epoxy 38 3.2.2.3 CFRP . 38 Specimen preparation . 39 Test setup and instrumentation . 40 Test Matrix .. 41 3.3 Test results and discussion . 41 Test results for EB beams . 42 3.3.1.1 Load carrying capacity 42 3.3.1.2 Load displacement behavior ... 43 3.3.1. 3 Strain behavior of EB beams .. 45 3.3.1.4 CFRP strain .. 46 3.3.1.5 Soil settlement . 47 3.3.1.6 Energy dissipation 47 3.3.1.7 Failure mode 48 Test results for NSM beams 49 3.3.2.1 Load carrying capacity ... 49 3.3.2.2 Load displacement behavior 50

PAGE 10

x 3.3.2.3 Strain behavior of NSM beams ... 52 3.3.2.4 CFRP strain . . 53 3.3.2.5 Soil settlement . 53 3.3.2.6 Ene rgy dissipation . .. 54 3.3.2.7 Failure mode . . .. 54 Comparison between EB and NSM sy stem s under soil settlement .. 56 IV BEHAVIOR OF CONTINUOUS BEAMS STRENGTHENED WITH EB CFRP SHEETS AND NSM CFRP STRIPS SUBJECTED TO DIFFERENTIAL SETTLEMENT ... .. 121 4.1 General overview . 121 4.2 Experimental program . . 122 4.2.1 Test specimens . 122 4.2.2 Materials .. 123 4.2.3 Specimen preparation . .. 123 4.2.4 Test setup and instrumentation . .... 124 4.2.5 Tes t Matrix . ... 125 4.1 Test results and discussio ... . 125 4.2.6 Test results for unstren gthened continuous RC beams ... 126 4.2.6.1 Load carrying capacity 126 4.2.6.2 Load displacement behavio r ... 127 4.2.6.3 Strain behavior of unstrengthened beams ... 127 4.2.6.4 Energy dissipation ... .. 128 4.2.6.5 Failure mode 129 4.2.7 Test results for EB continuous RC beams .. 129 4.2.7.1 Load carrying capacity capacity ... 130

PAGE 11

xi 4.2.7.2 Load displacement behavior . 131 4.2.7.3 Strain behavior of EB beams .... 132 4.2.7.4 CFRP strain ... 134 4.2.7.5 Soil settlement .. 135 4.2.7.6 Energy dissipation 135 4.2.7.7 Failure mode .. 136 4.2.8 Test results for NSM beams 137 4.2.8.1 Load carry ing capacity capacity ... 138 4.2.8.2 Load displacement behavior ... .. 139 4.2.8.3 Strain behavior of N SM beams ... 140 4.2.8.4 CFRP strain 141 4.2.8.5 Soil settlement 142 4.2.8.6 Energy dissipation ... 142 4.2.8.7 Failure mode ... 143 V SUMMARY AND CONCLUSIONS 200 R EFERENCES. .. 207

PAGE 12

xii LIST OF TABLES TABLE 2.1 . Typical properties of common FRP Types according to (ACI C ommittee 440, 2004) ...... . .. . . 21 2.2. Sieve analysis test result . 21 2.3. Unified soil classification (Bowles, 1997) ..22 2.4. Range of modulus of subgrade reaction k s (Subramanian, 2010) and (Bowles, 997) 2.5. Modulus of 2.6. Modulus of subgrade reaction of soil with different water ratio at 9 mm settlement . 2 4 2.7. Modu lus of subgrade reaction of soil with v 3.1. Concrete mix design (21 MPa ) . 58 3.2. Compressive strength of concrete cylinders . ..58 3.3. Beam tests matrix . ..59 3. 4. Monotonic EB test results 3.5. Test results of beams bonded with EB C FRP sheet 3.6. Failure modes of beams bonded with EB C FRP sheet . ...61 3.7. Monotonic NSM test results .. .. 62 3.8. Test results of beams bonded with NSM CFRP strip .. . 62 3. 9 . Failure modes of beams bonded with NSM CFRP strips . ... 63 4.1. Compressive strength of concrete cylinder at 7 days ..145 4.2. Compressive strength of concrete cylinder at 10 days 145 4.3. 4.4. Failure modes of continuous RC beams

PAGE 13

xiii LIST OF FIGURES FIGURE 2.1. Jacketing column (Julio et al., 2003) . ..... 25 2.2. Retrofitting method of bolted steel plate proposed: (a) bolted steel plate (b) laterally restrained side plate(Su et al., 2011) 25 2.3. EB and NSM example (Nanni, 2005) 26 2.4. FRP types (Gün aslan et al., 2014) 27 2.5. Sieve analysis test: (a) Sand sample; (b) Dry sand in oven; (c) Sieve shaker and sieves; (d) measure the weight of sieve and reta ining sand using scale.. . . .28 2.6. Grain size distrib ution . 2.7. Plate test for dense sand: (a) Sand compaction tools; (b) sand compaction; (c) Test setup; (d) Plate, load cell, jack installation, and linear potentiometer . 2.8. Pressure settlement curve 2.9. Plate test for loose sand: (a) Test setup; (b) Plate, load cell, jack installation, and linear potentiometer 2.10. Pressure s ettlement . 2.11. Pressure settlement curve for loose sand:(a) dry sand. (b) 15% wc undrained; (c) 15% wc . . 2.11. Pressure settlement curve for loose sand(continued ):(d) 20% wc undrained; (e) 20% wc drained; (f) 25% wc undra ined; (g) 25% wc ......................................................................................... ...32 2.12. Modulus of Subgrade R eaction ..33 2.13. Optimum moist 2.14. Test for determination the best amount of water ratio for soil for specimen testing: (a) soil sample weighting; (b) water weighting; (c) test setup for drain soil; (d) sample of s

PAGE 14

xiv 2.14. Test for determination the best amount of water ratio for soil for specimen testing (continued): (e) sample of soil specimen after test with plate; (f) sample of soil specimen after removing the plate; (g) test setup for undrain ed soil; (h) submerged specim . . 3.1. Specimen dimensions and details (mm): (a) Cross section near hinge support; (b) C ross section near fix support; (c) Beam dimension and reinforcement detail; (d) Beam with groove dimension and reinforcement . 64 3.2. Specimen with CFRP bonded details (mm): (a) EB CFRP sheet; (b) NSM CFRP strip 65 3.3. Cylinder test for compressive strength 65 3.4. Steel cage fabrication: (a) bar cutting; (b) stirrup fabrication; (c) main steel bar bending; (d) steel bars after bending; (e) fabricated steel cage . . ... 66 3.5. Preparation: (a) wood Form; (b) mixer; (c) RC beams after stripping; (d) curing . 67 3.5. Preparation (continued): (e) cleaning surface; (f) gluin g CFRP sheets; (g) bonding CFRP strip . 68 . 3.6. Beam testing setup and scheme using hydraulic jack and rigid frame . .. 3.7. Beam testing setup and scheme using MTS machine and (F DS) support type . . .. 70 3.8. 1. Test result of UB 1: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression . 71 3.8.2 Test result for EB 2: (a) load displacement; (b) PI gage strain in tension; (c ) PI gage strain in compression ... .. 72 3.8.2 Test result for EB 2 (continued): (d) FRP strain at different locations; (e) FRP s train at different loading stages . 73 3.8.3. Test result for EB 3: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression 74 3.8.4. Test result for EB 4: :(a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in comp ression 75

PAGE 15

xv 3.8.5 Test result for UB 5: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2) ... ........................................... ......................... . . .. 76 3.8.6 Test result for EB 6: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2) . . . ... 77 3.8.7 Test result for EB 7: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m2) . 3.8.7 Test result for EB 7 (continued): (e) FRP strain at different locations; (f) FRP strain at different loading ... . . .. 79 3.8.8 Test result for EB 8: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2) ............ .. 3.8.9 Test result for UB 9: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m2) 3.8.10 Test result for EB 10: (a) lo ad displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m2) . 3.8.11 Test result for EB 11: (a) load displacemen t; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m2) 83 3.8.12 Test result for EB 12: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m2) . .. 84 3.8.12 Test result for EB 12 (continued): (e) FRP strain at different locations; (f) FRP strain at different loading stages . . ... 85 3.8.13 Energy dissipations for EB beams: (a) energy dissipation for (F RS); (b) energy dissipation for (F DS); (c) e nergy dissipation for (F WS), (d) average energy dissipation for each category . .. 86 3.9.1. Failure mode for UB 1: (a) flexural cracks at mid span at 10 kN loading and shear cracks at 30 kN; (b) co ncrete crush at 48kN; (c) beam deflection is clear; (d) beam failed by concrete crushing at 49.31 kN . ... 87

PAGE 16

xvi 3.9.2. Failure mode of EB 2: (a) flexural crack at mid span develop at 20 kN loading and sh ear cracks at 30 kN; (b) shear cracks develop and concrete crush at 45kN and FRP debond at its edge at 53kN; (c) CFRP debond and connect the shear crack; (d) beam failed by FRP debonding at its edge and . ... . 88 3.9.3. Failure mode of EB 3: (a) flexural crack at mid span develop at 30 kN loading; (b) shear cracks develop at 40 kN; (c) CFRP sheet with concrete cover are peeled out at 55 kN loading; (d) another view of peel out; (e) beam failed by FRP and concrete cover peel ou . . 89 3.9.4. Failure mode of EB 4: (a) flexural cracks at mid span at 18 kN; (b) and (c) shear cracks start developing at 32 kN; (d) beam fails due to CFRP sheet debonding at 59 kN near fixed support . 90 3.9.5. Failure mode of UB 5: (a) flexural crack at mid span develop at 20 kN loading and concrete crush at point load; (b) shear cracks develop at 35 kN , and Beam failed by concrete crush and shear cracks next to fixed end at point load at 48 kN . 91 3.9.6. Failure mode of E B 6: (a) flexural crack at mid span develop at 20 kN loading and shear cracks at fixed support side, concrete crush at point load about 45 kN then FRP sheet debond at 59 kN; (b) shear cracks develop on soil side too; (c) CFRP sheet debonding; (d) beam after it failed by FRP . .. 92 3.9.7. Failure mode of EB 7: (a) flexural crack at mid span develop at 25 kN loading; (b) s hear cracks develop at 45kN on both side from the edge of FRP sheet; (c) CFRP sheet debonding on soil side and concrete crush and spoiled out about 60 kN; (d) beam after it failed by FRP debonding and . . 93 3.9.8. Failure mode of EB 8: (a) flexural crack at mid span develop at 25 kN loading; (b) Shear cracks develop at 40kN on the fixed side; (c) shear cracks deve lop at 50 on the soil side from the edge of FRP sheet; (d) CFRP sheet debonding after connect with shear cracks at its edge near 94 3.9.8. Failure m ode of EB 8 (continued): (e) concrete crush at the area of FRP debonding and shear cracks at 66 kN; (f) an other side of FRP sheet connect shear cracks too . .. 95 3.9.9. Failure mode of UB 9: (a) flexural crack at mid span develop at 10 kN loading; (b) shear cracks develop at 35 kN on the fixed side; (c) concrete crush ed near point load at 48 kN; (d) beam fail due to concrete crush and sh . . 96

PAGE 17

xvii 3.9.10. Failure mode of EB 10: Flexural crack at mid span develop at 20 kN loading and shear cracks develop at 45 kN on the fixed side, then concrete crush ed near fix end at 73 kN . 97 3.9.11. Failure mode of EB 11: (a) flexural crack at mid span develop at load 20 kN; (b) sand settlement increase beam deflection; (c ) shear cracks develop at 47 kN on the fixed side, then concrete crush near point load at 50 kN, and finally CFRP debond near fix end at 63 kN; (d) beam after it fails 98 3.9.12. Failure mode of EB 12: (a) Flexural crack at fix end at 20 kN loading and shear cracks develop at 35 kN on the fixed side; (b) then shear crack develop and reach FRP edge then the beam fails finally by CFRP debonding near fix end at 6 5 kN; (c) concrete cover peeled off in top surface near shear cracks; (d) concrete cover with CFRP in bottom sur . ... 99 3.10.1. Test result of NSM 2: (a) load displacement; (b) PI gage strain in tens ion; (c) PI gage strain in compression . . 100 3.10.2. Test result of NSM 3: (a) load displacement; (b) PI gage strain in tension; (c) P I gage . ..101 3.10.3. Test result of NSM 4: (a) load displacement; (b) PI gage strain in tension; (c) P I gage strain 102 3.10.3. Test result of NSM 4 (continued): (e) FRP strain at different locations; (f) FRP stra in at different .. . . 103 3.10.4. Test result of NSM 6: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loade d area = 0.09 m 2 ) 104 3.10.5. Test result of NSM 7: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settl ement (loaded ar ea = 0.09 m 2 .... . 105 3.10.6. Test result of NSM 8: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settl ement (loaded area = 0.0 9 m 2 . ... 106 3.10.7. Test result of NSM 10: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area=0.09 m 2 ) .. . . .... .......................................... ............. . .................. .. . 107

PAGE 18

xviii 3.10.8. Test result of NSM 11: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure se ttlement (loaded area=0.09 m 2 .. 108 3.10.9. Test result of NSM 12: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settleme nt (loaded area=0.09 m 2 ) . .. 109 3.10.10. Energy dissipations for NSM beams: (a) energy dissipation for (F RS); (b) energy dissipation for (F DS); (c) energy dissipation for (F WS), (d) average energ y dissipation for each category 110 3.11.1. Failure mode of NSM 2: (a) flexural crack at mid span at 20 kN loading and shear cracks start and develop at 45 kN on the fixed side while ver tical cracks near fixed end have been seen clearly at 52 kN; (b) cracks develop near CFRP strip edge and the beam fails by CFRP debonding near hinge end at 62 kN; (c) CFRP strip debonding; (d) beam af ter fa . . 3.11.2. Failure mode of NSM 3: (a) flexural crack at mid span at 20 kN and vertical cracks near fix end at 39 kN while shear cracks start developing at 45 kN between mid span and suppo rt on both sides; (b) cracks develop near FRP strip edge and the beam fails by FRP debonding with concrete cover around it next to fixed end support at 67 kN; (c) other side view of debonding; (d) beam main steel reinforcement . . ... 112 3.11.3. Failure mode of NSM 4: (a) flexural cracks at mid span at 20 kN; (b) vertical cracks next to fix face at 50 kN and shear cracks start developing at 45 k N; (c) CFRP strip debond s with some of the concrete cover s at 73 kN; (d) test specimens after it fails due to CFRP debonding .. 113 3.11.4. Failure mode of NSM 6: (a) flexural crack at mid span at 25 kN and vertical cra cks near fix end at 25 kN; (b) shear cracks start developing at 45 kN between mid span and support on both sides and soil settlement increase; (c) cracks develop near CFRP strip edge and the beam fails by CFRP debonding with some concrete cover next to fixed end support at 72 kN; (d) cracks between fix end and mid span . .. 114 3.11.4. Failure mode of NSM 6 (continued): (e) Cracks between hinge support and mid span; (f) FRP strip debonding . . 115 3.11.5. Failure mode of NSM 7: (a) flexural crack at mid span at 20 kN and vertical cracks near fix end at 25 kN while Shear cracks start developing at 42 kN between mid span and support on both sides and soil settlement increase; (b) shear crack connect point load with the bottom edge of fix end at 59 kN; (c) beam fails at 61 kN due to shear cracks and concrete crush ed and spill out; (d) sand .. 116

PAGE 19

xix 3.11.6. Failure mode of NSM 8: (a) flexural crack at mid span at 24 kN and vertical cracks near fixed end at 29 kN while Shear cracks start developing at 31 kN between mid span and fixed support; (b) soil settlement increase and cracks increase and develop; (c) beam fails at 66 kN due to FRP strip debonding with concrete cover surrounding it on fix end sid e; (d) concrete . 17 3.11.7. Failure mode of NSM 10: (a) flexural crack at mid span at 7 kN and Shear cracks start developing at 37 kN between mid span and fixed support; (b) beam fails at 66 kN due to FRP strip debonding with concrete cover surrounding it on fix end side; (c) concrete cover spoiled out (d) FRP strip debonding . .. 118 3.11.8. Failure mode for NSM 11: (a) Vertical cracks next to fix face at 18 kN then flexural cracks at mid span at 23 kN and shear cracks start developing at 34 kN between mid span and fixed su pport while beam inclined due to soil settlement; (b) Cracks are increasing and developing; (c) Beam fails at 60 kN due to developing of shear cracks and concrete crushing ; (d) test .. 119 3.11.9. Failure mode for NSM 12: (a) flexural cracks at mid span at 17 kN then Vertical cracks next to fixed support face at 25 kN and shear cracks start developing at 45 kN between mid span and fixed support while; (b) cracks are increasing and developing near fix end side; (c) soil settlement increase and cracks increase on the same side of soil; (d) t est specimens after it fails at 65 kN due to developing of vertical cracks at fixed end . . . 120 4.1. Specimen dimensions and details (mm) : (a) cross section near mid span ; (b) cross section near hinge support; (c) beam dimension and reinforcement detail; (d) beam with groove dimension an d reinforcement . . . . .148 4.2. concrete test for compressive stre ngth: (a) c ylinder ready for the test ; (b) f ailure shape of tested 4.3. Beam preparation : (a) s tirrups Fabrication ; (b) bending main steel bar; (c) w ood form fa . . ... 4.3. Beam preparation (continued): (d) steel cages; ( e) casting b eams ; (f) curing beams; ( g) g luing C FRP sheets . ...151 4.4. T est set up for ( R R R ) support : (a) unstrengthening beam; ( b ) EB continuous RC b eams .

PAGE 20

xx 4.4. T est set up for ( R R R ) support (continued) : (c) NSM continuous RC b eams . ... ....153 4.5. T est set up for unstrengthening RC beam with ( R R S ) support 4.6.1. Test details and instrumentation for CUB 1: (a) test setup; (b) linear potentiometer; (c) PI gages and strain gages .. ...154 4.6.2. Test details and instrumentation for beam CU B 4: (a) test setup; (b) linear potentiometer to measure settlement of submerged soil with 25% of water ratio; (c) PI gages and s 4.7.1. Test result of CUB 1: (a) load displacement at span a; (b) load displacement at span b; (c) PI gage strain in tension at span a; (d) PI gage . . ..156 4.7.1. Test result of CUB 1(continued): (e) strain gage readings of concrete in compression at span a; (f) strain gage readings of concrete in compression at span b; (g) PI gage strain in tension at mid support; (h) strain gage readings of concrete in compression at mi d su pport . .157 4.7.2. Test result for CEB 2: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression . 4.7.2. Test result for CEB 2 (continued): (g) stra in gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in c ompression at mid support;(k) strain gages reading of FRP . ..159 4.7.3. Test result of CEB 3: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression . 4.7.3. Test result of CEB 3 (continued): (a) load displacement at span a; (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in compression at mid support;(k) strain gages reading of FRP in tension at mid support ;(l) loadin g scheme . .161

PAGE 21

xxi 4.7.4. Test result for CUB 4: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages re ading of concrete in compression at span a; (f) strain gages reading of concrete in . . 4.7.4. Test result for CUB 4(continued): (g) pressure settlement a t span b; (h) PI gages strain in tension at mid support; (i) strain gages reading of concrete in compression at . . ..163 4.7.5. Test result for CEB 5: (a) load displac ement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at spa n a; (f) strain gages reading of concrete in compression at span b 4.7.5. Test result for CEB 5 (continued): (g) strain gages reading of FRP at span a; (h) strain gages rea ding of FRP at span at span b; (i) pressure settlement at span b; (j) PI gages strain in tension at mid support; (k) strain gages reading of concrete in compression at mid support; 4.7.6. Test result for CEB 6: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in ...166 4. 7.6. Test result for CEB 6 (continued): (g) strain gages reading of FRP at span a; (h) strain gages reading of FRP at span at span b; (i) pressure settlement at span b; (j) PI gages strain in tens io . .. .167 4.7.6. Test result for CEB 6 (continued): (k) strain gages reading of concrete in compression at mid support;(l) strain gages reading of FRP at mid span ; ... 4.7.7. Test result for CNSM 7: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression . ..169

PAGE 22

xxii 4.7.7. Test result for CNSM 7(continued): (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in compression at mid support;(k) strain gages reading of C FRP . 4.7.8. Test result of CNSM 8: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) P I gages strain in tension at span b; (e) Strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compress . ..171 4.7.8. Test result of CNSM 8(continued): (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) str ain gages reading of concrete in compression at mid support;(k) strain gages reading of FRP . . . 4.7.9. Test result for CNSM 9: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in 4.7.9. Test result for CNSM 9(continued): (g) strain gages reading of FRP at span a; (h) strain gages reading of FRP at span at span b; (i) pressure settlement at span b; (j) PI gages strain in tension at mid support; (k) strain gages reading of concrete in compression at mid support; (l ... 4.7.10. Test result of CNSM 10: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in . ...175 4.7.10. Test resul t of CNSM 10(continued): (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) pressure settlement at span b;(j) PI gages strain in tension at mid 4.7.10. Test result of CNSM 10(continued): (k) strain gages reading of concrete in compression at mid support;(l) strain gages reading of FRP in tension at mid support; (

PAGE 23

xxiii 4.7.11. Energy dissipations for continuous beams: (a) energy dissipation for CUB 1 ; (b) energy dissipation for CEB 2 ; (c) energy dissipation for CEB 3; (d) ener gy dissipation for CUB 4; (e) energy dissipation for CEB 5; (f) energy dissipation for CEB . ..178 4.7.11. Energy dissipations for continuous beams (continued) : ( g ) energy dissipation for CNS M 7 ; ( h ) energy dissipation for CNSM 8 ; ( i ) energy dissipation for CNSM 9; ( j ) energy dissipation for CNSM . . ..179 4.8.1 Failure mode of CUB 1: (a) Flexural crack at mid support at 10 kN loading; (b) Flexur al cracks at mid span a at 10 kN; (c) Shear cracks at 38 kN; (d) Shear cracks develop after .. .180 4.8.1. Failure mode of CUB 1(continued): (e) flexural shear cracks at 78 kN; (f ) concrete crush at point load at 52kN; (g) cracks develop; (h) beam failed by concrete crushing at point load on span b a t 85.787 kN. .. . .181 4.8.2. Failure mode of CEB 2: (a) flexural cracks at mid span b at 20kN; (b) flexural crack at mid support at 20 kN; (c) concrete crush at point load on span b at 37 kN; (d) shear cracks at 50 kN; (e) shear cracks develop at 70 kN on span b; (f) local de bonding of FRP sheet at middle 182 4.8.2. Failure mode of CEB 2 (continued): (g) & (h) cracks develop Beam failed by concrete crushing near shear cracks o n span b at103.6 kN; 4.8.3. Failure mode of CE B 3: (a) flexural crack at mid span a at 20 kN and cycle 2; (b) flexural cracks span b at 27 kN and cycle 2; (c ) flexural cracks mid support at 30 kN and cycle 2; (d) beam defle . .184 4.8.3. Failure mode of CEB 3(continued): (e) beam deflection at span b; (f) shear cracks at 35 kN near mid su pport at span a at cycle 3; (g) FRP deboned at span a at 85 kN; (h) concrete crush at point load on span a at 117 kN at cycle 11; (i) beam after its fail by concrete . . 4.8.4. Failure mode of CUB 4: (a) flexural crack at mid support at 10 kN; (b) flexural cracks at both mid span (span a) at 10 30 kN; (c) shear crac ks at 30kN near mid support; (d) shear cracks develop at middle of both span (span a) at 50 kN; (e) deflection increase at span a; (f) soil . ..186

PAGE 24

xxiv 4.8.4. Failure mode of CU B 4 (continued ): (g) concrete crush at point load on span a at 78 kN; (h) beam hogging at mid support and Cracks developed; (i) beam after its fail by concrete crushing under point load on s pan a at . ..... ... 4.8.5. Failure mode of CEB 5: (a) flexural crack at mid support at 20 kN; (b) flexural cracks (span b) at both mid span at 30 kN; (c) shear cracks at 40 kN near mid suppo rt; (d) shear cracks (span b) develop at middle of both span after 70 kN; (e) soil settlement; (f) shear cracks developed and FRP 4.8.4. Failure mode of CEB 5 (continued) : (g) FRP parts deboned at middle support on span b; (h) beam hogging at middle support; (i) concrete crush at point load on span a at 117 kN ;(j) failure location at span a from other side view; (k) concrete spoil out at span a; (l) beam after its fail ..189 4.8.6. Failure mode of CEB 6: (a) flexural crack at mid support at 25 kN and cycle 2; (b) flexura l cracks (span b) at both mid span at 40 kN and cycle 4; (c) shear cracks at 55 kN and cycle 5 at mid span near soil on span b; (d) concrete crush near point load at span a at 70 kN and cycle 6; (e) shear cracks developed and FRP debonding at mid span at cycle 7; (f) FRP parts deboned at mid support and shear cracks developing at cycle ..190 4.8.6. Failure mode of CEB 6(continued): (g) shear cracks develop at mid span b; (h) FRP sheet at mid support damaged; (i) concrete crushing near mid support and hogging of beam on middle support at load 127 kN cycle 11 ; (j) beam after its fail by concre 4.8.7. Failure mode of CNSM 7: (a) flexural crack at mid support at 24 kN; (b) and (c) flexural cracks at both mid span (span a and span b) at 25 kN; (d) cracks transfer to other side of beam at mi d . ..192 4.8.7. Failure mode of CNSM 7 (continued): (e) shear cracks at 35 kN at mid span and both mid span; (f) concrete crush at mid span a at 119 kN near NSM CFRP strip; (g) CFRP strip after concr ete surrounding it are crushed; (h) beam after its fail by concrete . 4.8.8. Failure mode of CNSM 8: (a) flexural crack at mid support at 30 kN span a and cycle 3; (b) fle xural cracks at span b at 30 kN and cycle 3; (c) flexural cracks at mid support at 35 kN cycle 3; (d) shear cracks at 55 kN and cycle 5 at mid support; (e) shear cracks at span b at 58 kN . ..194

PAGE 25

xxv 4.8.8. Failure mode of CNSM 8(continued):(g) cracks develop at span a; (h) cracks develop at span b; (i) beam fails due to concrete c rushing after shear cracks reach NSM CFRP strip at mid span b at 109 kN ; (j) other view .195 4.8.9. Failure mode of CNSM 9: (a) flexural crack at span b at 30 kN; (b) flexural cracks at span a at 30 kN and at mid support at 25 kN; (c) shear cracks at 32 kN near mid support; (d) shear cracks (span a) develop at middle of both ... . ..196 4.8.9. Failure mode of CNSM 9( continued ): (e) cracks develop (span b); (f) beam fails due to shear cracks that propagate and top CFRP debonding at span a at 90.8 kN; (g) be am after its fail by concrete crushing and . 4.8.10. Failure mode of CNSM 10: (a) flexural crack at mid support at 0 kN and cycle 3; (b) flexural cracks at span a at 24 kN and cycle 3; (c) flexural cracks at span b at 34 kN cycle 5; (d) shear cracks at span b at 63 kN cycle 7; (e) shear cracks at 37 kN and cycle 8 at mid support; (f) shear cra cks at span a at 36 kN cycle 8; (g) shear cracks develop at span a and ..198 4.8.10. Failure mode of CNSM 10(continued): (h) CFRP debonding at span a at bottom surfaced of beam; (i) beam after it fails due to concrete crushing .

PAGE 26

xxvi N OTATION B1 Beam NO. 1 B1 DDS cont. Beam NO. 1 Dry Dense Sand (density=115.11 lb /ft 3 ) Unstrengthened beam B5 DLS FRP Beam NO. 5 Dry Loose Sand (density=94.67 lb/ft 3 ) beam Strengthened with FRP. C c Coefficient of curvature CEB 2 Continuous Externally bonded with FRP sheet strengthened beam NO.2 CEB 2 a C Continuous Externally bon ded FRP sheet strengthened beam NO.2 compressive strength at span a C u Coefficient of uniformity CUB 2 a T Continuous un strengthened beam NO.2 tensile strength at span a CUB 3 Continuous unstrengthen beam NO.3 (control beam) CNSM 2 Continuous near surf ace mounted/ FRP strip strengthened beam NO.2 D60 Diameter of particles corresponding to 60% fines DS 1 Dry sand reading at point 1 EB Externally bonded FRP EB 2 FRP sheet strengthened beam NO.2 EB 2 H1 FRP sheet strengthened beam NO.2 strain gages 1 r eading near hinge support EB 2 F6 FRP sheet strengthened beam NO.2 strain gages 6 reading near Fixed support

PAGE 27

xxvii EB 6 S avg . FRP sheet strengthened beam NO.6 average soil settlement of two point s on hinge support K act . Actual modulus of subgrade reaction tak en from 9 mm soil settlement K avg . Average modulus of subgrade reaction of three point s on the plate . K s Modulus of subgrade reaction NSM Near surface mounted FRP NSM 2 FRP strip strengthened beam NO.2 P The magnitude of load applying on beam during test P1 Point 1 Pu The magnitude of Maximum failure load of the beam during the test . UB 1 Unstrengthen beam s NO.1 wc% Water content ratio 20WS D1 20% water ratio added to dry soil and drained (water is allowed to discharged out of soil container) sa nd reading at point 1 20WS UD1 20% water ratio added to soil and undrained (water is not allowed to discharged out of soil container ) sand reading at point 1 b The deflection at mid span of the beam. s 1 The settlement of sand at the first point on hin ge support at corner. s. Avg. The average settlement of sand for two point s on support one at front left the edge of the support and the second at the back right side of support.

PAGE 28

1 CHAPTER I I NTRODUCTION 1.1 General Structures subjec t to many factors that affect its performance and may cause failure to it . One of these factors is a differential settlement of soil under the structure . Many of concrete structures have problems due to soil interaction that has a great impact on structural behavior. Nowadays, m any solutions are investigated and created by engineers and construct o rs . Different materials are presented in the construction market, like fiber reinforcement polymer (FRP) which is widely used in structural engineering applications. FRP are a new produc t that made of a composite material which consist s of glass, carbon, or aramid fibers embedded in a resin matrix. The fibers are to improve the tensile strength and stiffness, while the matrix joins the fibers together as one unit. CFRP are used for repair and rehabilitation of different structural element. CFRP is considered a promising solution for strengthening, improving and retrofitting of concrete structures (Esfahani, Kianoush, & Tajari, 2007) . This method of strengthe n ing is widely acceptable recently for its advantages. As a material, CFRP has a high strength weight ratio, great corrosion resistance, improved durability, easy to work with, and reducing long term maintenance costs (Wang, Dai, & Harries, 2013) . In addition , strengthening with CFRP doesn't need special tools to install it or some special technique. Therefore, the maintenance of concrete structure complete quickly, easily , and with cheaper cost (Orbanich, Dominguez, & Ortega, 2012) . For example, CFRP sheets are bonded to the exterior bottom surface of the beam (on tension fiber location) to increase flexural capacity. Like in bridges Girders rehabi litation, CFRP sheets is glued to the bottom of the beam . Traditionally, beams flexural

PAGE 29

2 capacity is carried only by reinforcement bars. CFRP can be used during construction to improve the capacity of the structural element. 1.2 Research Significance In the U nited States , different areas have shrinking or swelling soils that cause damages to different kind of structures like buildings and roads. Statically, these damages cost about 2.3$ billion which is more than twice cost of damages caused by an other nature hazard : flood, tornadoes, earthquakes, and hurricanes combined (Holtz & Hart, 1978) Surv e . The settlement of soil beneath structure largely impact its behavior. However, if the soil move s down or compres se s uniformly , it doesn't cause damage to the structure . But, when its settle in some parts of land or in a non uniform way , it may largely affect the structure. This unequal settlement defined as differe when the soil under structure is swelling, shrink or move away (Lahri & Garg, 2015) . The causes of differential settlement come from increasing or change in shape or kind of loads applied to structural element, change in soil properties during year seasons, drainage of water from soil mass, flooding , water leaks, erosion as in granular soil like sand, and root trees growing; all these causes let the differential settlement unavoidable (Lahri & Garg, 2015) (Bezih, Chateauneuf, Kalla, & Bacconnet, 2014) . The differential settlement cause increasing in axial forces, shear forces and bending moments of structur e and often counted one of many causes of structures failures (Lahri & Garg, 201 5) . These stresses impact the efficiency of the concrete element as a result of developing cracks due to tensile stresses. But, avoiding or decreasing these cracks could be achieved by making the right decision during the design process, material selectio n, and construction practices. Using CFRP is one of many solutions that will assure structure serviceability, increasing its service life, and preserve its shape.

PAGE 30

3 This study presents an experimental research that is examining the performance of reinforce ment concrete beam strengthened with CFRP sheet or strip . CFRP subjected to the effect of the differential settlement of one of its support. Also, shows how CFRP and concrete act under this situation, examine the load deflection relationship and observe th e impact of water presence in soil on the stiffness of soil. 1.3 Objectives This experimental research program primarily aims to investigate the flexural performance and efficiency of C FRP materials when it used for strengthening the Reinforcement concrete str uctures and increase its carrying capacity when it's under a differential settlement of soil. This can achieved by addressing specific objectives that include: 1. Observe the variation in failure load as the conditions of support and type of C FRP varies. 2. Inve stigate the strain of RC structures in both compression and tension zones and along C FRP sheet or strip . 3. Examine the modulus of subgrade reactions of soil under that structure and status of soil as dry or submerged in water. 4. Show the energy dissipation in RC structures strengthen with C FRP materials. 5. Present the failure mode s of the structures under these conditions. 1.4 Scope This thesis has concentrated on study behavior of RC structures strengthen with CFRP under a differential settlement of soil beneath i t. Three phases are conducted in this thesis depending on the type of CFRP strengthen and beams length. Phase 1 has 9 beams with 1 4 00mm length and CFRP sheet for strengthening and 3 unstrengthening RC beams . Phase 2

PAGE 31

4 has 9 beams with 1400mm length and CFRP strip strengthen . Phase 3 has 10 continuous beams with a total length of 2800 mm. A nother parameter was added which is the soil condition, which is sand soil. T he soil condition was dry loose or low density soil and loose submerged soil . This parameter is added to see the impact of soil settlement on the capacity of the structural element. All beams are tested in bending. 1.5 Thesis outline The contents of the thesis are briefly outlined below : Chapter 2: presents a review of literature related to previous r esearch on rehabilitation of concrete structures, strengthen methods used for it, CFRP types , technique and application, General behavior of concrete beam in flexural, and Soil effect on structures by the differential settlement. In addition , s ome soil tes ts conducted to determine the needed properties of soil used in the experiment . Chapter 3: describe details of the experimental program for short one span beams . It provides the results of the experimental investigations into the flexural behavior of the s trengthened RC beams under different support boundary condition s which include: Load Deflection behavior and failure mode, Load Strain behavior, Pressure Settlement of Soil behavior, Load FRP strain behavior, and Beam Energy Behavior. , including design and fabrication of test specimens, instrumentation, test setup, and procedures. Chapter 4: describe details of the experimental program for continuous beams over two spans . It provides the results of the experimental investigations into the flexural behavior of the strengthened RC beams under different support boundary conditions ; which include: Load Deflection behavior and failure mode, Load Strain behavior, Pressure Settlement of Soil

PAGE 32

5 behavior, Load FRP strain behavior, and Beam Energy Behavior., including design and fabrication of test specimens, instrumentation, test setup, and procedures Chapter 5: presents conclusions of the study and recommendations for future research References: referring to all previous papers and works that discussed in this study.

PAGE 33

6 CHAPTER II L ITERATURE REVIEW 2.1 Introduction This chapter presents a simple idea about a method for strengthen ing concrete structural member with CFRP against the soil settlement. In addition , it discus se s previous studies about the method of strengthen i ng concrete structures. The chapter also gives some information on CFRP materials, their types, properties and the purpose and technique of using this material. Then its move to present some papers on the general behavior of concrete elements in flexural. Furthermore , this chapter shows useful information on soil: types, properties, and its effect on concrete structures. The last part of the chapter discu s s the effect of the differential settlement on concrete structures and shows the reason of chosen this topic. 2.2 Background Reinforced concrete structures prove their excellent performance as they widely used in construction because of their structural behavior and durability. Concrete is a material that made by mixing cement, sand, aggregate, and water with a specific amount for each of them before hardening, which is a great advantage of this material. Concrete has one disadvantage k under tensile stresses and has high resistance to compressive stresses. To enhance concrete behavior under tensile stresses , steel bar s is added to it and thus create composite materials called reinforced concrete RC. Although RC structures ha ve many adv antage s and show great serviceability during its lifetime, RC member still get s deterioration or get damage due to many effects like environmental factors, sulfate attack, soil behavior beneath member, etc. sometimes that

PAGE 34

7 damage leads the RC member to fail and impact the whole structure. Therefore, it should replace the damaged member. This will cost more money, time and effort. Therefore, strengthen or rehabilitation are a good solution as it keep s the structure standi ng, increase its life cycle and the me mber capacity to an acceptable level, and it a good way to save money, time and effort. 2.3 S trengthen ing r einforced c oncrete s tructures The meaning of word strengthen ing simply is to make the thing stronger, and according t o make something stronger so that it will take more weight or force without breaking engineering , its meaning to increase the capacity and stiffness of structure to resist the external stresses or applied forces like shear stresses, fl exural stresses, extensive loading, moving loading, stresses due to change in elevation or position of structural member due to external impact like ground moving or soil settlement. Strengthening of RC structures can be done by either adding new structura l element or strengthening of an existing structural member. The need to strength or rehabilitee of the structure may arise at any time from the start of construction stage because of design errors, deficient concrete production, and poor execution process es; while during the structure service life because of external forces and environmental impact, changes or updates in structural functionality, etc . (J u lio , Branco, & Silva, 2003) . Strengthen ing technique used for each struct ur e depend on many factors like the cost/benefit study of each method and structural assessment, and structural behavior objectives. There are many methods and technique that used to strength concrete structures depend on the impacting forces and type of dam age the structure subject. For example, Uma Shankar .K, ( 2015 ) explain s in their paper a typical RC strengthen s technique by Jacketing RC

PAGE 35

8 beams, columns, and improving th e thickness of the slab . Reestablishment of cover and loose concrete. Or using steel plate to improve the strength of the structure . For footing, they suggest doing an extension of footing . E S Ju´ lio et all (Feb 2003) present the same method in their pap er for rehabilitation and strengthening columns using Reinforced concrete jacketing as shown in figure 2.1. This method particular work demands and has the benefit that its increase strength uniformly. This method can be explain ed just for a c olumn by adding and anchoring longitudinal bars to the footing , and slab crossing of these longitudinal bars, preparation of column surface, added stirrups with particular ly calculated spacing, temporary supports used for structure, and finally adding the new concrete. This method improve s the durability of the original structural element, but the corrosion and fire protections need other techniques in this method . Also , this method is highly influenced by details which explained in the paper . Also , the siz e of the member will increase . Another method for strengthening RC structures is using steel plate shown in figure 2.2. This method is used for retrofitting existing RC structural members. Su, Cheng, Wang, Siu, & Zhu ( 2011) summarized studies on this approach that conducted at the U niversity of Hong Kong. It shows how to develop this method to inhibit and resist local buckling of steel plate as sho wn in figure 2.2.b. The paper discu s ses strengthening RC members by this method for different cases: shear strengthening of coupling beams, flexural strengthening of floor beams, and axial strengthening of columns using an innovative post compression metho d. The result for each instanc e w as that using this approach for previous cases leads to increase shear strength by 40 90% for the first instanc e , and the ultimate strength increased by 32 59% for the second case, while the ultimate capacity rose by 17.9 t o 63.4 % for the last case . Ano ther method for strengthening is grout injections, insertions of steel reinforcement or prestressing .

PAGE 36

9 All these methods need skilled work and may disturb the function of structures, sometimes is not acceptable for structure a rchitectural heritage or historical value (Saileysh Sivaraja, Thandavamoorthy, Vijayakumar, Moses Aranganathan, & Dasarathy, 2013) Over last de cade, new materials enter the market and are widely used concrete in construction and rehabilitation of damaged structures like bridges, dams, building structures, parking garage, etc., which is called Fiber Reinforcement Polymer (FRP). This material is mo re durable and has high tensile strength, high elastic modulus with low weigh t and expected to have a longer life when it used in concrete structure rather than steel reinforcement (Täljsten & Blanksvärd, 2007) . These advantages led widely to use FRP in strengthening concrete structures. Externally bonded FRP system (EB) were introduced and used around the world for strengthening structures in the mid of 1980s, where research in Switzerland contribute in first externally bonded FRP system application for bridges strengthening (Setunge, Nezamian, & Lokuge, 2002) . Near Surface Mounted (NSM) were used later than externally bonded system as there is limited literature available on the first time using NSM FRP for structural strengthening. Fig ure 2.3 give an example o f both methods. However, there were laboratory studies reported in Warren (1998) (L De Lorenzis & Nanni, 2002) . 2.4 Fiber r einforced p olymer (FRP) Introduction FRP material as d efined in previous chapter and it is an emerging material that is used widely nowadays in the construction field. Types and names of FRP materials depend on the used fiber type. The types of FRP that can be easily found in the market are: Carbon fiber rein forced polymer (CFRP), Aramid fiber reinforced polymer (AFRP) and glass fiber reinforced polymer (GFRP). Figure 2.4 present these type in their sheet shape.

PAGE 37

10 This method of strengthen ing is widely acceptable recently for its advantages. As a material, CFRP has a high strength weight ratio, great corrosion resistance, improved durability, easy to work with, and reducing long term maintenance costs (Wang et al., 2013) . Also , strengthening with FRP doesn't need special tools to install it or some unique technique. Therefore, the maintenance of concrete structure complete quickly, e fficient ly , and with cheaper cost (Orbanich et al., 2012) . For example, CFRP sheets are bonded to the exterior bottom surface of the beam (on tension fiber location) to increase flexural capacity. Like in bridges Girders rehabilitation, CFRP sheets glued to the bottom of the beam . FRP are available in different size and shape. FRP types and properties Aramid and Carbon FRP are preferred in ACI 440.4R 04 standard. Typical properties of different types of FRP material are given in T able 2.1. Brief explanation o f these types below: Carbon Fibers (CFRP): nature of carbon fibers has different physical properties in different directions (anisotropic material). It has high strength, accepted creep level, high elastic modulus. Low conductivity and density, and chemical effects resistance. However , it has the low co mpressive strength . Glass fibers (GFRP): has high tensile strength compare to its light wei ght, low cost, salt water and chemical resistance (World et al., 2014) , and it is made using different type s of glass like E Glass, S Glass and C Glass (Günaslan et al., 2014) . Aramid Fibers (AFRP): The name of this type comes from the term of AROmaticpolyAMIDe which is synthetic organic fiber made of aromatic polyamides . It has

PAGE 38

11 excellent fatigue and creep s resistance. Also, it has a lower modulus, w eight , and cost than the CFRP. Six different types of fibers have been used to form AFRP rods: 1. Kevlar® the three most common available grade for structural applications in the market are Kelvar 29, Kelvar 49, and Kelvar 149 (Bagherpour, 2012). 2. Tw aron® 3. Technora® 4. Aropree® 5. FiBRA® 6. Rarafil® FRP technique FRP is widely used in structural industry for increasing the strength capacity of the structural element as its can be formed with a different shape, cheap material, strong and light weight material. This experiment uses two systems for strengthening with CFRP which are: externally bonded (EB) and near surface mounted (NSM) system. Externally bonded system was early used to strength damaged structures . FRP sheet can be made in one direction or multi directions and are bonded externally on a concrete surface . This system has two main techniques for strengthening which are: wet lay up FRP system and pre cure FRP system. Wet lay up system is done by bonding dry and flexible CFRP with epoxy resin s on a concrete surface , and it is done on site , and in this experiment . This technique is flexible, need a short time to be done, and installation cost is low. The second primary system is pre cured can be done by bonding rigid CFRP sheet that i s already saturated and pre cured before site application (BASF, 2007; Namrou, 2013 ; Siriwardanage, 2014) . Near su rface mounted (NSM) were used later than externally bonded system and attracted researcher and its practical

PAGE 39

12 applications increased. I n this system the first thing is to make grooves cut into a concrete cover for the element and then FRP reinforcement is e mbedded inside the groove and bonded using bonded agent like epoxy or cement grout. T his method or system w as used to be called (L. De Lorenzis & Teng, 2007) . Premature FRP debonding failure is a common failure for externally bonded FRP strengthening structures because of stress concentration at cut off point (Siriwardanage, 2014) . FRP applications FRP as a structural material has high demand because of its many advantages as discussed bef ore like low weight, easy to install, high tensile strength and durability, high resistance to corrosion and its availability in different sizes and shapes. All that make FRP one of the most promising and leading material in various applications. Many engi neers prefer to use this material (Barros & Fortes, 2005 ; Siri wardanage, 2014) . FRP is beeing used in construction application heavily due to its advantages. Also in the design of structures where the high strength and stiffness of FRP can be included and oriented in a way that satisf ies design demand (Materials, 1984) . FRP are used in repairing and rehabilitation of deteri o rated or damaged structures (Wu, Li, & Sakuma, 2006) . All advantage for this material encourage s researcher and eng ineers to expand research studies and experiments i n this field. More investigations and studies will be given in later sections. As shown before in previous sections , t he first time that the FRP materials used in concrete structures w ere in the mid of 195 0s. FRP reinforcing bars were produced and used in several applications in the 1980s like seawalls, roof deck for industrial places, and concrete floor slabs for buildings on aggressive chemical environments (Rizkalla, Hassan, & Hassan, 2003) . Exte rnally bonded system was used early. FRP material w as used in constructing and repairing bridges and buildings in Europe, North

PAGE 40

13 America, and Japan. C oncrete bridges reinforced for flexural strengthening was the first applications of externally bonded syste m that conducted research in Switzerland (Grace, 2003) . Failure mode of EB and NSM systems F ailure mode in RC beams strengthened with EB and NSM can be divided into many categories. In EB system failure mode may be interfacial debond ing and FRP sheet rupture . Wu and Yin ( 2003) present on their paper the cracking behavior and interfacial debonding fracture in strengthened concrete beams with EB system FRP. The paper s hows that properties of the adhesive and concrete have significantly affect ed the propagation type of cracks distribution on concrete. T wo typical failure mode with EB system were defined which are the macroscopic interfacial debonding of FRP concrete and the rupture of FRP sheets . For NSM many failure modes are observed. Most of them are presented here. The first one is debonding at FRP bar/strip adhesive interface which happened due to weakness in bonding between FRP and adhesive . The s econd type of fail ure is a cohesive shear failure within the adhesive that occurr ed when tensile strength of the adhesive is exceeded . The third failure type is debonding at adhesive concrete interface (most common failure) , which happen either due to pure interfacial failu re or shear cohesive shear failure in concrete, failure may occur due to adhesive cover splitting that happen when groove size is inadequate, and the last one is concrete splitting when the NSM strip is close to edge or failure due strength capacity of el ement itself (Pellegrino & Sena Cruz, 2015) and (Namrou, 2013) .

PAGE 41

14 Previous study and research on EB and NSM FRP strengthening system There is so many research that done about EB and NSM system. S ome of them are mentioned previously , and some of the research will be discuss ed here. CFRP can be used with different construction materials like concrete, steel , and timber. One of the earliest research is done by Meier ( 2000) . T he paper looks for explaining how advanced polymer matrix composite materials with its advantage can be used to repair deteriorated infrastructures. T he paper concludes that CFRP sheet and strips are one of the promising strengthening applications. A l so , CFRP is an excellent choice for rehabilitation of many problems in bridges. Laura De Lorenzis and Nanni ( 2002) observe the bond between NSM FRP rods and concrete by handling some f actors that affect bond performance which is the length of the bond , rod diameter, FRP material type, the arrangement o f rod surface, and size of the groove. Parretti & Nanni ( 2004) present on their paper NSM system for RC member and shows bond related problems, design recommendation for flexural a nd shear, and some design examples. I n addition , the paper provides a comprehensive protocol for intelligent using of NSM technology. Wu et al. ( 2006) proposed a novel hybrid EB FRP (carbon and glass) con crete structure , o n which CFRP glued to resist tensile load and GFRP glued as U wrap for shear and to prevent premature failure . The result from this work show s that this system and technique has improved the flexural behavior. L. De Lorenzis and Teng ( 2007) review on their paper a discussing of ex isting research on use NSM FRP system and characterize the gaps of knowledge and give some outlines directions for future studies . T he paper concludes that the work and research till now still limited to us e NSM FRP technique as there are many questions

PAGE 42

15 ne ed to be addressed a new technology. Y. Dong et al. (2011) study the performance of RC beams strengthening with EB CFRP unde r fatigue loading . O ne of the conclusion s from this study conclude that the standard or criterion for fatigue design of EB RC beams should be limited to steel reinforcement stress range and recommendations by ACI 215 (ACI 1995) , and AASHTO (2007) for fatig ue design of RC beams can be used with EB RC beams too. Kim, Hossain, & Harries ( 2013) present an experimen t to observe the behavior of Douglas Fir timber beams which are recovered from a 32 year old Quonset. T he beams strengthened with CFRP shows increasing in load carrying capacity about 184% and in deflection ductility about 165% . A lso the load distribution w as improved. Another paper by Kim & Bumadian ( 2016) study the e lectrochemical reactions for steel beams strengthened with CFRP sheets in an experimental program. T he paper suggests design recommendations for using CFRP strengthening (EB) system for steel members that expo sed to corrosive environment. Abdullah and Abdul Kadir ( 2016) explain in their paper the NSM system for RC beams as the best emerged technology for strengthening RC beams for shear and flexural. Kim and Siriwardanage ( 2016) present on their paper the behavior of NSM system for strengthening concrete member under thermal and mechanical loads . The study was done to observe the temperature dependent interfacial responses which impact the performance NSM system.

PAGE 43

16 2.5 Soil 2.5.1 General overview Soil can be defined as any natural stratum forming the outer part of earth crust, consisting of an accumulation of separated particles like mineral and organic matter together with inconstant amounts of wa ter and gas (mostly air) (Krstelj, 1994) . The soil is formed due to weathering and decay from solid rocks, tr ansportation of these soils is done by the wind , water , and glaciers and then form various landforms (Al Khafaji Andersland, O. B., 1992) . Fo r civil engineering, soil is material that made of particles of different shape and size with minor bonding between them to form a structure that can deform under applied artificial or natural forces. The s oil , in general, contain s three parts: particles ( solid), liquid which is in most times water, and air (Balkema, 2002) . One of a most important branch of engineering science is soil mechanics, which is used to solve many engineering problems in/with soil. The physical properties of soil can be identified by experiments (Krstelj, 1994) . From these properties, the behavior of soil can be mo stly predicted under the investigation of this paper. Soil can be easily classified into three categories: sand, silt, and clay. Soil are varied in their shape , so they classified according to their effective diameter. Clay has a diameter small than 0.002 mm, while sand and silt have different size limits in different classification systems. However, the upper limit of sand is 2 mm. P articles that have a size bigger than 2 mm are not consider ed as soil particles or part as they hardly impact the productivi ty of the soil . Particles with size (2 mm 7.5 cm) are called pebbles, (7.5 25 cm) are called cobbles, (25 60 cm) are stones, and particles with size (>60 cm) are called boulders (Osman, 2013) .

PAGE 44

17 Sand was chosen as soil for this experiment as its available in the laboratory and some of its properties. The most two properties of soil needed in this investigation is the soil classification and soil modulus of subgrade reaction (stiffness); which can be determined by two tests: Grain size analysis (sieve analysis) and plate test. These test s were direct ly performed to identify the soil type and control the sand properties for t he experimental work that will be discuss ed in next chapter. 2.5.2 Soil laboratory test 2.5.2.1 Sieve analysis Since the soil consists of grouping different particles that have various shape and size. This experiment is to identify the proportional particles, by dry mas s of each size range. This test usually is done by using standard sieves having inside diameter 203.2 mm (8 in). Each sieve has standard mesh opening (Al Khafaji Andersland, O. B., 1992) . After running the test, soil particles passed through sieve opening larger than its size. The bigger particles will return on the sieve . The soil is passed through many sieves arranged downward with their size opening decreasing. This experiment requires determining the percentage of soil particle passes through each sieve. The test data and results are shown in T able 2.2. Figure 2. 5 show the procedures that proceed to run this test and figure 2. 6 show the grap h of grain size distribution of test result on a logarithm scale. According to the data of test and as compared with T able 2.3, the result show s that the soil is poorly graded sand. The Uniformity Coefficient was calculated (C u ) as 3.245 , and the Coefficie nt of gradation ( Cc ) of the sand was 1 . 1 . The sand d ensity that used was 1546 Kg /m 3 .

PAGE 45

18 2.5.2.2 Plate test The soil stiffness is defined in term of the modulus of subgrade reaction which direct ly calculated based on the fo rmula below . K s s w here Ks are in (kN/m 3 to depth the soil settles. The test is done by applying load on a plate with dimension 300mm x s i tting horizontally on soil (Das, 2011) . The readings were recorded using data acquisition device with a load cell and three potentiometers. For testing , result to be consistent and within linear solution , the modulus of subgrade reaction K s is measured when the settlement reach es 9 mm. T wo specimens of dry sand were tested in the laboratory. The first one is dry sand specimen that was compacted using a circular plate with diameter of 304 mm (12 in) which were lifted and dropped from suitable height about 750 mm (30 in) for 75 tim es for each sand layer with depth of 150 mm (6 in) up to three layers of total depth of 450 mm (18 in) as shown in figure 2. 7 . (a) A nd (b). What t he density obtain s from this process was 1843.85 kg/m 3 (115.1079 lb/ft 3 ) which is denoted as a dense sand. W hi le the second specimen is dry sand without any compaction process and the density measured to be 1516.46 kg/m 3 (94.67 lb/ft 3 ) and denoted as loose sand. The test process and result for plate test of dense sand are shown in figure 2. 7 . (c) a nd (d) and fig ure 2. 8 . T he modulus of subgrade reaction for dense sand is 92,839.5 kPa as shown in T able 2.5. If this result compared with T able 2.4 , it indicate s that the sand is within dense sand as expected.

PAGE 46

19 For loose sand, the test set up is shown i n figure 2. 9 whil e the test result is provided in T able 2.5 and figure 2.1 0 . T he test result shows that the modulus of subgrade reaction of this sand is 13,595.33 kPa/m. W hich is mean that the sand is loose sand as it falls within the loose sand range shown in T able 2.4. f evident that the loose sand settle s more than dense sand under the same loading. T he loose sand is chosen for this experimental work. 2.5.2.3 Determination of a water content ratio to get more settlement for experiment Another parameter a dded to analysis which is water presence in soil impact. The p resence of water in soil has a significan t effect on soil properties which has an impact on the behavior of concrete structure set on the soil . To determine the amount of water needed to get a h igher settlement and lower modulus of subgrade reaction , a simple plate test was run in the laboratory for sand specimens that have a different amount of water. The amount of water is calculated as a weight ratio of the sand specimen and added to the sand specimen. A compacted mold was used with dimensions of 152.4 mm (6 in) diameter and 177.8 mm (7 in) height . This test has two categories. The first one is donated by drain sand on which water is allowed to drainage out from the mold opening during the test . The second category is denoted by un drain sand on which the water stays in the sand and prevented from draining out the mold. A multipurpose sealing wrap was used by covering the mold from its outside to close the opening and prevent water from coming ou t from mold opening during the test . Seven sand specimens were prepared with different water ratio, one dry sand and three water ratios 15%, 20%, and 25% with drain and un drainage conditions. However, the natural water content was between (4 6%) for all d ried sand that was used in this experimental work . It a higher ratio of water to the soil and water volume is bigger than mold volume . 20 kips MTS machine was used to apply the pressure on soil specimens, and two

PAGE 47

20 linear potentiometer s and load cell connected to data acquisition and the computer were installed to measure the settlement and load during the test . Figure 2.1 shows the test instrumentation, procedure , and specimens. The results of the test are provided in T able 2.6 for 9 mm settlement for consistent as mention before and figure 2.1 shows all test result as pressure settlement curves . The result shows that the 25% of water ratio added to soil under undrain ed condition gives the higher settlement and lowest modulus of subgr ade reaction. This ratio considered the best one that can be used for this experiment. And the soil with this ratio is donated by submerged soil as the water level is higher than the soil surface . Table 2.7 shows the m odulus of subgrade reaction of soil wi th variable water ratios at the same load 5kN for all tested specimens. And figure 2.1 2 presented the relation between K s calculated at 5 kN load and water ratio in soil. Another conclusion is soil with drain condition shows higher modulus of subgrade reac tion than soil without drainage as the sand particle filled the gaps of water volume and stick together which arrange the particles and make soil structure stronger. If a comparison is made between the graph of figure 2.1 2 and graph on figure 2.1 3 which re present optimum moisture content, they look similar , and that means that modulus of subgrade reaction is proportional to dry density for sandy soil.

PAGE 48

21 FRP type CFRP GFRP AFRP Young modulus 100 140 G P a 20 40 GPa 48 68 G P a Ultimate t ensile s trength 1 ,020 2,080 M P a 520 1,400 MPa 700 1,720 M P a Typical densit y 1.5 to 1.6 (g/cm 3 ) 1.2 to 2.1 (g/cm 3 ) 1.2 to 1.5 (g/cm 3 ) US Sieve No. Opening (mm) Mass r einterned on each sieve(g) Cumulative mass retained above each sieve (g) Percent finer 4 4.75 5.6 5. 6 99.08 10 2 131.4 137 77.6 40 0.425 318.3 455.3 25.57 60 0.25 73.8 529.1 13.5 200 0.075 74.2 603.3 1.37 Pan 0 8.4 611.7 0 Poorly graded sand (Bowles, 1997) * D60 (mm) 3.82 Cu=D60/D10 3.245 D30 (mm) 2.23 Cc= (D30) ^ 2 / (D10*D60) 1.1 D10 (mm) 1.177 * according to T able 2.1 on Page 32 Table 2.1. Typical properties of common FRP types according to ACI committee 440 (ACI, 2004 ) Table 2.2. Sieve analysis result

PAGE 49

22 Table 2.3. Unified soil classification (Bowles, 1997)

PAGE 50

23 Soil K s , kN/m 3 (kPa/m) Loose s and 4800 16 000 Medium dense sand 9600 80 000 Dense sand 64 000 128 000 Clay medium dense sand 32 000 80 000 Silty medium dense sand 24 000 48 000 Clay soil: q a 200 < q a q a > 800 kPa 12 000 24 000 24 0 00 48 000 > 48 000 Dense sand K 1 (kPa/m) --------P 1 (kN) --------K av. (kPa/m) 92,839.5 K 2 (kPa/m) --------P 2 (kN) --------K 3 (kPa/m) 92,839.5 P 3 (kN) 75.2 Loose sand K 1 (kPa/m) 15,828.53 P 1 (kN) 10.04 K av. (kPa/m) 13,595.33 K 2 (kPa /m) 12,214.21 P 2 (kN) 8.44 K 3 (kPa/m) 12,743.27 P 3 (kN) 8.44 Table 2. 4 . Range of modulus of subgrade reaction k s (Subramanian, 2010) and (Bowles, 1997) Table 2. 5 . Modulus of subgrade reaction of soil at 9 mm settlement wc% load 1 mm 2 mm K1 K2 wc% dry sand 5.011 5.096 5.702 1.0344 0.8893 0.000 dry sand 2 5.0107 6.47 5.967 0.8472 0.7932 0 15% 5.032 3.449 3.692 2.486 2.234 15.000 20% 5.0107 5.798 5.701 0.8865 0.8347 20 25% 5.0107 6.897 6.942 0.5389 0.5044 25 Table 2.4. Mod ulus of subgrade reaction of soil with different water ratio at 5kN

PAGE 51

24 Dry 0% wc K 1 (kPa/m) 9870 P 1 (kN) 6.98 K av. (kPa/m) 9,911.66 K 2 (kPa/m) 9,953.33 P 2 (kN) 7.06 UD 15% wc K 1 (kPa/m) 29,338 P 1 (kN) 20.73 K av. (kPa/m) 27,572.05 K 2 (kPa/m) 25,756.1 P 2 (kN) 18.33 D 15% wc K 1 (kPa/m) -----P 1 (kN) -----K av. (kPa/m) -----K 2 (kPa/m) -----P 2 (kN) -----UD 20% wc K 1 (kPa/m) 10,599.6 P 1 (kN) 7.5 K av. (kPa/m) 10,872.3 K 2 (kPa/m) 11,145 P 2 (kN) 7.88 D 25% wc K 1 (kPa/m) 38,688 P 1 (kN) 27.34 K av. (kPa/m) 38,719.15 K 2 (kPa/m) 38,750.3 P 2 (kN) 28.61 UD 25% wc K 1 (kPa/m) 8,443 P 1 (kN) 5.96 K av. (kPa/m) 8420.23 K 2 (kPa/m) 8,397.46 P 2 (kN) 5.93 D 25% wc K 1 (kPa/m) 23,891 P 1 (kN) 17.06 K av. (kPa/m) 23,025.1 K 2 (kPa/m) 22,159.2 P 2 (kN) 15.7 D: D rained soil; UD: Undrained soil; wc: water weight ratio that added to soil specimen wc load 1 ( mm ) 2 ( mm ) K1 (kPa/m) K2 (kPa/m) dry sand 5.011 6.501 5.731 9 , 818.57 11 , 137.77 5.032 3.449 3.692 18 , 586.75 17 , 363.41 5.0107 2.3194 2.216 27 , 5 20.29 28 , 804.41 5.0107 6.897 6.942 9 , 254.83 9 , 194.83 Table 2. 6 . Modulus of subg rade reaction of soil with different water ratio at 9 mm settlement wc% load 1 mm 2 mm K1 K2 wc% dry sand 5.011 5.096 5.702 1.0344 0.8893 0.000 dry sand 2 5.0107 6.47 5.967 0.8472 0.7932 0 15% 5.032 3.449 3.692 2.486 2.234 15.000 20% 5.0107 5.798 5.701 0.8865 0.8347 20 25% 5.0107 6.897 6.942 0.5389 0.5044 25 Table 2.4. Mod ulus of subgrade reaction of soil with different water ratio at 5kN Table 2. 7 . Modulus of subgrade reaction of soil with variable water ratios at 5kN wc% load 1 mm 2 mm K1 K2 wc% dry sand 5.011 5.096 5.702 1.0344 0.8893 0.000 dry sand 2 5.0107 6.47 5 .967 0.8472 0.7932 0 15% 5.032 3.449 3.692 2.486 2.234 15.000 20% 5.0107 5.798 5.701 0.8865 0.8347 20 25% 5.0107 6.897 6.942 0.5389 0.5044 25 Table 2.4. Modulus of subgrade reaction of soil with different water ratio at 5kN

PAGE 52

25 Figure 2.2. Retrofitting method with bolted steel plate : (a) bolted steel plate (b) laterally restrained side plate (Su et al., 2011) (a) (b) Figure 2.1. Jacket ed column (J u lio et al., 2003)

PAGE 53

26 Figure 2.3. EB and NSM examples (Nanni, 2005)

PAGE 54

27 Figure 2. 4 . FRP types (Günaslan et al., 2014)

PAGE 55

28 Figure 2.5. Sieve analysis: (a) sand sample; (b) dry sand in oven; (c) sieve shaker and sieves; (d) weight of sieve and retaining sand using a scale ( a ) ( b ) ( c ) ( d )

PAGE 56

29 99.08 77.6 25.57 13.5 1.37 0 20 40 60 80 100 0.01 0.1 1 10 Percent finer (%) Particle diameter (mm): log. scale Figure 2.6. Grain size distribution Figure 2.7. Plate test for dense sand: (a) sand compaction tools; (b) sand compaction; (c) test setup; (d) plate, load cell, jack installation, and linear potentiometer installation. ( a ) ( b ) ( d ) ( c )

PAGE 57

30 0 200 400 600 800 1,000 0 3 6 9 12 15 Pressure (kPa ) Settlement (mm) P1 P2 P3 Figure 2.8. Pressure settlement curve for dense sand ( b ) ( a ) Figure 2.9. Plate test for loose sand: (a) test setup; (b) plate, load cell, jack installation, and linear potentiometer installation

PAGE 58

31 0 100 200 300 400 500 600 0 10 20 30 40 50 60 Pressure (kPa) Settlement (mm) P1 P2 P3 Figure 2.10. Pressure settlem ent curve for loose sand ( a ) ( b ) ( c ) Figure 2.11. Pressure settlement curve for loose sand: (a) dry sand; (b) 15% wc undrained; (c) 15% wc drained y = 10.793x 2.11 y = 10.105x + 4.38 0 100 200 300 400 0 5 10 15 20 25 Pressure (kPa) Sand settlment (mm) DS P1 DS P2 y = 31.668x 24.537 y = 28.454x 29.764 0 100 200 300 400 0 5 10 15 20 25 Pressure (kPa) Sand settlment (mm) UD1 15% wc UD2 15% wc y = 41.207x 0.5314 y = 33.633x 8.6345 0 100 200 300 400 0 5 10 15 20 25 Pressure (kPa) Sand settlment (mm) D1 15% wc D2 15% wc

PAGE 59

32 ( d ) ( e ) ( f ) ( g ) Figure 2.11. Pressure settlement curve for loose sand (continued):(d) 20% wc undrained; (e) 20% wc drained; (f) 25% wc undrained; (g) 25% wc drained y = 10.633x + 0.0953 y = 11.293x 0.8968 0 100 200 300 400 0 5 10 15 20 25 P ( kPa ) Sand settlment (mm) UD1 20% wc UD2 20% wc y = 42.372x 34.358 y = 40.83x 14.225 0 100 200 300 400 0 5 10 15 20 25 P (kPa) Sand settlment (mm) S1 20% D S2 20% D y = 6.8655x + 9.8778 y = 6.4257x + 13.075 0 100 200 300 400 0 5 10 15 20 25 P ( kPa ) Sand settlment (mm) UD1 25% wc UD2 25% wc y = 20.821x + 29.056 y = 18.746x + 28.163 0 100 200 300 400 0 5 10 15 20 25 P ( kPa ) Sand settlment (mm) D1 25% wc D2 25% wc

PAGE 60

33 0 5,000 10,000 15,000 20,000 25,000 30,000 0 10 20 30 K ( kPa/m ) % wc K1 K2 Figure 2.12. Modulus of subgrade reaction water ratio Figure 2.13. Optimum moisture content

PAGE 61

34 Figure 2.14. Test for determination the bes t amount of water ratio for soil for specimen testing: (a) soil sample weighting; (b) water weighting; (c) test setup for drain soil; (d) sample of soil during test ( a ) ( b ) ( c ) ( d )

PAGE 62

35 ( e ) ( f ) ( g ) ( h ) Figure 2.14. Test for determination the best amount of water ratio for s oil for specimen testing (continued): (e) sample of soil specimen after test with plate; (f) sample of soil specimen after removing the plate; (g) test setup for undrain soil; (h) submerged specimen during test

PAGE 63

36 CHAPTER III B EHAVIOR OF RC BEAMS STRENGTHENED WITH CFRP SHEETS AND STRIPS SUBJ ECTED TO DIFFERENTIAL SETTLEMENT OF SOIL 3.1 General overview T his experimental program was conducted to investigate the flexural behavior of RC beams strengthening with CFRP subjected to differential settlement . In this program, two strengthening techniques with CFRP were used: E xternally Bonded (EB) CFRP sheets and near surface mounted (NSM) CFRP strips and three varied conditions for beam specimen support were included as fixed support and rigid hinge support (F RS), fix support and hinge support that set o n dry soil (F DS), and fix support and hinge support that set on submerged soil (F WS) . The amount of water that added to make sand submerged was determined previously in chapter two to be 25% of the sand weight added to the sand , and that was to observe t he effect of the presence of water on the behavior of strengthening beams with CFRP. T his chapter will describe all work related to this part of research on the following sections: S ection 3.2 provides a description of the experimental program which inclu de s the material properties of the RC beam specimens, soil used for test specimens, fabrication and preparation of test specimens, and experimental setup and instrumentation . S ections 3.3 and 3.4 present the result and discussion s for all six categories. T he r esults include Load Displacement behavior and failure mode, Load Strain in tension, Load Strain in compression, Pressure Settlement of s oil, Load FRP strain, and Energy dissipation up to peak failure load .

PAGE 64

37 3.2 Experimental program Test specimens Total of 2 1 RC beams ( 6 categories) were used in this program. The RC beams sample were made with a compressive strength of 21 MPa ( 3045.79 psi) and with dimensioned of each as following: 1400 mm (55.12 in) long x 165 mm (6.5 in) heights x 100 mm (4 in) wide . T he tension reinforcement s were made of two steel rebar no.3 with a diameter of 9.5 mm (0.375 in), located at an effective depth of 135 mm (5.3 in). T he steel rebar was bent at one end of RC beam to increase shear resistance capacity at the end of the bea m and it was bend on an other side to form compression reinforcement with a total length of 570 mm (22.44 in). shear stirrups were included using rebar no.2 with diameter of 6.35 mm (0.25 in) and with spacing at 76.2 mm (3 in) center to center. Figure 3.1 s hows the beam specimens dimensions and details. Nine of RC beam were having the groove of size 900 mm (35.4 in) x 25 mm (1 in) deep x 1.7 mm (0.5 in) wide at the middle of the bottom face of the beam as shown in figure 3.1 (d) . After concrete curing achiev ed, the NSM Aslan 500 TM CFRP strip with a dimensions 2mm (0.0079 in) thick x 16 mm (0.63 in) deep x 900 mm (35.4 in) long is inserted and bonded with conventional epoxy adhesive as shown in figure 3.2 (b) . A nd then curing apply for seven days. Also, nine RC beams having CFRP sheets with dimensions 900 (35.4 in) long x 100 mm (4 in) wide x 0.165 mm ( 0.006 5 in) thick. The CFRP sheets are externally bonded to the middle bottom face of the beams using the same conventional epoxy adhesive which shown in figure 3.2 (a). The rest 3 beams were left without strengthening.

PAGE 65

38 Materials 3.2.2.1 Concrete 21 MPa (3045.79 psi) concrete mix design was used to mix the concrete as illustrated in T able 3.1. T he water cement ratio of the mix design was 45%. T he concrete was mixed and p repared using an electrical mixer in the laboratory. C oncrete cylinder s were cast with the beams and tested for compressive strength after 28 days of curing. A compressive test machine was used to test cylindrical specimens with dimensions of 100 mm (4 in) diameter x 200 mm (8 in) height. F igure 3. 3 shows the concrete cylinder specimen after it tested (crushed) and machine reading. T he average compressive strength for cylindrical specimens was 21.29 MPa (3087.85 psi), and the results are listed in T able 3. 2 . 3.2.2.2 Epoxy Epoxy adhesive is a conventional bonding agent that is used with CFRP in many applications. T he epoxy that used to glue CFRP sheets and CFRP strips was Mbrace epoxy resin. T he epoxy adhesive has low glass transition temperature which is 71 C (160 F ). T he epoxy is made of two parts: a resin that has a blue color and a hardener that has no color (clear). T he mix ratio by weight between resin and hardener is 3:1 respectively. T he curing time of the epoxy mix blend is at least 7 days to enabl e it achieving its ultimate strength ( f epx ) of 55.2 MPa (8006 psi). T he elastic modulus ( E epx ) of cured adhesive is 3034 MPa (440 ksi ) (BASF Construction Chemicals, 2007) . 3.2.2.3 CFRP Two type of CFRP were used to strengthening RC beams: CFRP sheet and CFRP strip. CFRP sheet was attached to the tension face of RC beams by an epoxy adhesive. While a

PAGE 66

39 groove was made on tension face of RC beam and NSM Aslan 500 TM CFRP strips were embedded in the groove and bonded using epoxy adhesive, its surface is fabricated in a way to improve the bonding. CFRP materials have a high ultimate tensile strength which is 1,020 2,080 MPa (150 350 ksi ), and the young modulus of this material are 100 140 GPa (15,000 21,000 ksi ) (ACI C ommittee 440, 2004) . Specimen preparation RC beams with a dimension discussed above prepar ed in the laboratory. The process of fabricating the beam s is illustrated below: 1 The steel bars no.2 and no.3 are measured and marked then cut to the required length. The bars no.2 are bent to form the stirrups, and steel cage are formed by tying the stir rups bars with the main two no.3 reinforcement bars by using metallic wires, after that the stirrups are connected together from top by using the same type of wire to make sure that they are on the same alignment and standing vertically. Figure 3.4 illustr ate this process. 2 Wooden forms are manufactured and oiled as shown in figure 3.5 (a), then the steel cages are inserted inside the forms and ti ed without any movement. F oam has groove dimensions was us ed and installed in wooden form to make a groove on the bottom face of RC beams. 3 Concrete is mixed using electrical mixing machine shown in figure 3.5 (b) with particular mix design shown in T able 3.2. The concrete mix are prepared and cast in the form , wi th using a vibrator and knocking on the side of the form to make sure that the concrete can go through the steel cages, and then the form is opened after 24 hours [figure 3.5 (c)]. T he beams are moved to curing room [figure 3.5 (d)] .

PAGE 67

40 4 The bottoms surfaces o f RC beams that are strengthened with CFRP sheet were adjusted and softened using an electric grinder [figure 3.5 (e)] and cleaned from dust with an air compressor before bonding the CFRP sheet , and that was to enhances adhesion capacity and improve the st rength of bonding of CFRP. The epoxy was prepared by mixing the resin and hard e ner with 3:1 ratio as stated previously , then applied it to the portion of bottom concrete beam surface and the precut CFRP sheet was bonded to the concrete beam figure 3.5 (f). The beams left 7 days at room temperature for curing. And the same thing is done for FRP strip which embedded into the groove [figure 3.5 (g)]. Test setup and instrumentation A ll RC beams were supported on fixed support (rigid) from the left side and hin ge support from the right side. T he beams were supported with an effective span of 1100 mm (43.3 in) and tested under four point load until its failure. all tests were done either by using 20 Kip (88.96 kN) MTS machine or by using a hydraulic jack and rigi d frame. The flexural test was done by applying a monotonic load to simulate a static loading condition. T he test with MTS machine was controlled by displacement/time ratio which is 2 mm/min and the load applied at mid a span of the RC beams. T he tests th at run by using the hydraulic jack were controlled manually by applying the load at a constant time and pressure with one rise and press of jack lever arm every 10 sec. Figure 3.6 illustrate s test set up with hydraulic jack for (F RS) support , and Figure 3 . 7 show tes t set up with MTS machine for (F DS) support. The b lue load cell w as used to record the load reading at each stage of the test. Two PI gages also used to get the strain at mid span of the RC beams on tension and compression zones. In addition , three linear potentiometers were used to measure the deflection of the beam at its mid span and the settlement of soil. Strain gages were used in some tests to observe the

PAGE 68

41 strain on FRP sheet or FRP strip. All the above instrumentation was installed on the RC beams and connected to data acquisition device, which is used to get the data and record it by software to a computer system that is attach ed to the data acquisition. Test Matrix T otal of twenty one RC beams were tested at this level of experiments. N ine RC beams were strengthened with FRP sheets, and nine RC beams were strengthened with CFRP strips. T hree RC beams were kept with no strengthening as control beams . Table 3.3 lists all 21 RC beams tested with their test conditions. RC b eams s trengthene d with FRP sheet were denoted with EB referring to externally bonded system. RC beams strengthened with CFRP strips were denoted with NSM referring to the near surface mounted system. The unstrengthen RC beams were denoted with UB. 3.3 Test results and discuss ion T his section includes the results obtained from the experimental testing of RC beams that are strengthened with CFRP sheets and strips. T he results of the experiments include the curve s of load versus displacement or deflection of the beam at mid span , the load versus beams strain in tension at the mid span curve, the load versus beam strain in compression at the mid span curve, and energy dissipation up to peak failure load. In addition , some test result has the pressure versus soil settlement curve s . F urthermore the results have failure mode for each tested beams. Finally, these results are summarized and used to compare the performance a n d behavior of tested RC beams according to their testing conditions . The tested beams were set up as discuss above . The specimens are grouped into six categories according to their strengthening type EB or NSM and their support conditions type

PAGE 69

42 which are (F RS), (F DS), and (F WS). Table 3.3 show the test matrix as discuss above. The tests are monotonically loaded as f our point bending until failure occurred. A ll instrumentations are used as discussed before and all data were observed and recorded by using data acquisition system. Test results for EB beams All test result of all beams are shown in Figure 3.8 for eac h beam test individually. The final results also are presented in T able s 3.4 and 3.5. 3.3.1.1 Load carrying capacity T he load carrying capa bilities of the RC beams w ere observed during the test to study the behavior of strengthened beams with EB . The summary of t he results is indicated in T able the COV of tested beam specimens. T hree unstrengthened s ample s (control beams) were tested with different support conditions to s ee the effect of soil settlement on the behavior of RC beams. The result show s almost no effect on loading capacity of the beam that tested with (F RS) and beam s tested with (F DS). However, the presence of 25% water in soil reduce the stiffness of soil an d allows the RC beams with (F WS) to fail at a higher load than the beams supported with (F RS) and (F DS). The ratio of increasing in load capacity between RC beam that supported with (F RS) and the one that supported with (F WS) was 11.36%. While the eff ect of 25% water presence in soil on increasing load capacity , was 13% if we compare between cases (F WS) and (F DS). The result of RC beams strengthened with EB shows that EB beams fail at higher load capacity and have higher standard deviation and COV (6 8.458 kN, 6.56, and 0.0958)

PAGE 70

43 respectively when the support condition is (F WS) than the beams that supported by (F RS) (56.46 kN, 2.64, 0.0467) . T he ratio of increasing is 21.5%, The presence of water makes the effect of soil settlement obvious as the value s are more random over a full range as they have higher standard deviation and COV. The ratio is decreased to be 11.6% when there is no water in the soil (F DS) where the results are (63.04, 3.17, 0.0502). A comparison between unstrengthened RC beams and EB beams shows that the beam load capacity increased when EB system used as the results indicate that the ratio of increasing are 14.5% for (F RS) case, 29.7% for (F DS) case, and 24.67% for case (F WS). 3.3.1.2 Load displacement behavior The displacement of all beam specimen s w as measured from mid span of beams using a linear potentiometer. The load displacement of EB specimens with (F RS) results are provided on Figures 3.8.1 (a), 3.8.2 (a), 3.8.3 (a), and 3.8.4 (a). The results show that beams have similar loa d displacement behavior at an early stage of loading up to 20 kN. At load range between 20 40 kN, the UB 1 , and EB 4 are slightly stiffer than EB 2 and EB 3. But, after 40 kN when the concrete start to crush and steel rebar are yielding, UB 1 lose its stu ffiness while strengthen beams show higher stiffness at higher load capacity than UB 1 up to failure load. 1 fails with lower load and high displacement than other strengthened beams which hav e almost same displacement and a slight diff erence in loading capacity. The EB system increase s the loading capacity and stiffness of RC beams in case of (F RS). For beams with support condition (F DS), the load displacement results are provided on F igures 3.8.5 (a), 3.8.6 (a), 3.8.7 (a), and 3.8.8 (a). T he results show that the beams still have the same load displacement trend at very low loading up to 10kN. At loading stage between 10 30 kN, UB 5 and EB 7 exhibit higher stiffness (low displacement) than EB 6 and

PAGE 71

44 EB 8. After 30 kN UB 5 began to lose its stiffness gr adually until it fails at 48 kN, w hile EB 7 keep having a higher stiffness than other beams up to failure load. The significant results are that the EB beams tested i n this case show wide random values of displacement with moderate differe nces in loading capacity ; and that because of the effect of sand behavior and its settlement impact. In addition , other reason may be related to the fact that every beam owen its unique properties due to manufacturing and its geometry. However, the EB syst em increase s the load capacity and stiffness of RC beams in case of (F DS). Finally, for beams with support conditions of (F WS), the load displacement result are provided in F igures 3.8.9 (a), 3.8.10 (a), 3.8.11(a), and 3.8.12 (a). T he results show that the beams have different load displacement behavior from the beginning. EB 10 has the higher stiffness up to its failure load, then beam UB 9 that has slightly lower stiffness than EB 10. However, EB 11 and EB 12 behave similarly up to 30 kN, but after th at beam EB 11 show higher stuffiness than EB 12. In fact, the UB 9 applying the same load when the beam fails. And because of that the highest load that the machine reached considered the beam failure load. In t his case the impact of 25% water that make s soil submerged soil is obvious as it a ffects the test results and make s them varies. Both load and displacement var y in this case. The load carrying capacity and beam resistance to the settlement of the EB system in this case is increase d . In summary and if we compare between the three cases, it concludes that the EB system success to increase the load capacity of the RC beams with different support condition with more deflection. The EB beams show higher resistan ce to soil settlement and deflect more.

PAGE 72

45 3.3.1.3 Strain behavior of EB beams The strain of all beams w as measured using two PI gages that installed at one edge at mid span of the beam. The first one location is on compression zone at a distance 25 mm (1 in) from the top surface of the beam, and the second one installed in the tension zone at a distance 25 mm (1 in) from the bottom edge of the beam. The first category (F RS) are presented in F igures 3.8.1 (b) and (c), 3.8.2 (b) and (c), 3.8.3 (b) and (c), and 3.8. 4 (b) and (c) for tension and compression zones. The results show that all beams tension strain increase gradually and beams strengthened with EB system have low tension strain than the unstrengthened beam. The EB beams have the same tension strain at low loading stage up to 8kN, after that EB 4 tension strain increase clearly more than EB 2 and EB 3, however , reduce s the tensile strain of RC beam. For compression zone, strain in all beams ha s similar compres sion strain at initial load stage up to 10 kN except EB 2 which has lower strain. After that, each beam behaves in a different way , but in general , the compression strain with EB system is less than unstrengthened beams. The result of strain for the secon d category (F DS) are presented in F igures 3.8.5 (b) and (c), 3.8.6 (b) and (c), 3.8.7 (b) and (c), and 3.8.8 (b) and (c). their result show that the EB system decrease s the strain in tension zones. Even though they have a similar strain at early loading s tage up to 15 kN except for EB 8 which has the lower tension strain . However, the results for compression zone show that the strain in compression for EB system is higher than the strain of unstrengthen beam. The result of strain for the last category whic h is (F WS) are presented in F igures 3.8.9 (b) and (c), 3.8.10 (b) and (c), 3.8.11 (b) and (c), and 3.8.12 (b) and (c). T he results were almost

PAGE 73

46 similar tensile strain up to 8kN load. After that, the higher tensile strain was observed with beams EB 11 and E B 12 more than UB 9 and EB 10. In general conclusions, the tensile strain for beams with (F R) support is higher than the tensile strain of beams (F DS) and (F WS) support, which mean that settlement tend s to decrease the tensile strain of RC beams. Althou gh, there are some unaccurate and random values and behave of tested beams which may be due to beams manufacturing or incorrect instrumentations, and /or Geometry, the general picture of results is the EB system reduce the strain of RC beams. 3.3.1.4 CFRP strain Three beams with EB system have strain gages to measure strain along CFRP sheets. One for each support case. Six strain gages were glued to beams and spread three on the right next to fixed support and three on the left next to hinge support. The strain g ages have an equal distance of 150 mm (5.9 in) center to center along the CFRP sheet , and the center of the beam was left without strain gages. T he purpose of that is to inv e stigate the strain induced along the CFRP and compare between each two strain gages on both sides. The first case (F RS) EB 2 results show that the strain was higher on mid span than the strain on other locations. Also, the strain near hinge support was higher than the one near fixed support side i n all three locations . F inally , the stra in increase s gradually as the applied load increase in all locations . The second case (F DS) EB 7 show the same behav io r that in the first case . But with different strain values. The third case (F WS) has a problem with strain gage that is near the CFRP sh eet mid span on the side hinge support which was damaged at the beginning of the test. However, the results show that the strain near mid span is still higher than the strain near

PAGE 74

47 supports. But the strain near fixed end is great er than strain next hinge su pport. T he reason of that is that the s ett lement of soil trend to reduce the strain of CFRP sheet. 3.3.1.5 Soil settlement This section related only to second and third cases which are (F DS) and (F WS). The difference between these two cases is the presence of w ater with a weight ratio of 25% that make soil submerged under water surface level. This amount of water makes the modulus of subgrade reaction (stiffness) at very low level. The settlement in dry soil case show s that all beams have the same trend at the e arlier load stage that is expressed now as pressure (kPa). The reaction of support on soil was structurally calculated to be equal to (0.3181 P) where P is the applied load on beam. The pressure on soil is equal to the reaction devided by the cross section area of support. After that unstrengthened beam shows more settlement than EB beams. The settlement in submerged soil is higher , and the result indicate s that EB 10 and UB 9 have low settlement than EB 11 and EB 12. The result prove s that EB system prove s the flexural behavior of RC beams under the differential settlement. 3.3.1.6 Energy dissipation The e nergy dissipation was observed in this experiment . Figure 3.8.13 show s the energy dissipation bars for each specimen . For the first category (F RS) its shown tha t the energy dissipation of unstrengthened beam ( 791.90 kN.mm) is higher than those that are strengthened with EB system (average energy dissipation [E avg . ] is 636.05 kN.mm). However, for case two (F DS) and case three (F WS), the energy dissipation of un strengthened beam is less than those beams strengthened with EB system. The results for energy dissipation were (F DS) are ( 501.51 and 855.29 kN.mm) for (UB and EB avg. ) respectively, and for (F WS) are (722.58 and 1610.9 7 kN.mm) for UB and EB avg. respectiv ely. The conclusion is that e nergy

PAGE 75

48 dissipation of unstrengthened RC beams w ith rigid support w as higher than those unstrengthened within soil settlement . However, when EB system ha s used the beams with soil settlement sho w higher energy than those with rig id support. Also, the UB is higher than EB when the case is (F RS) and is lower when the case is (F DS) or (F WS). 3.3.1.7 Failure mode The failure mode is another parameter that been observed i n this experimental work. The failure mode of unstrengthened beams a nd EB beams is presented in Figure 3.9. Most EB ha s a similar failure mode. Table 3.6 show how the beams behave under loading at each loading stage during the whole test. In the first categories with (F RS), the unstrengthened beam UB 1 fail by having flex ural cracks at mid span which been observed at 10 kN, then shear cracks developed on both side s near the mid span area at 30 kN. The beam deflection increased and the beam finally fail by concrete crushing at point load at 49 kN. For EB 2, EB 3, and EB 4 t he failure of these beams also start by flexural cracks at mid span , but it was observed at higher loads than UB 1, (20, 30, and 18 kN) for (EB 2, EB 3, and EB 4) respectively. After that, shear cracks are observed at loads 30 kN with flexural cracks that increased at mid span and developed. Then each beam behaves on its own. EB 2 fails at load 53 kN when the shear cracks on hinge side support reach the edge of CFRP sheet and the point load causing CFRP debonding with concrete splitting. EB 3 fails at load 56 kN by concrete cracks propagate horizontally and then concrete cover with CFRP are peeled off from the fix support edge. EB 4 fails by microscopic interfacial of CFRP concrete near the fix end support. For the second category (F DS), the failure mode with all beams have similar behave at early load level, UB 5, EB 6, EB 7, and EB 8 show flexural cracks at mid span at 20 25 kN,

PAGE 76

49 then shear cracks develop at 30 40 kN. After that, the failure mode behavior change s . UB 5 fails due to shear crack propagation up to point load and concrete crushing at 48kN. EB 6 failure was similar to EB 3 by peeled off concrete cover with CFRP but with slightly higher load at 59.7 kN. EB 7 and EB 8 fail in a similar way as EB 2 and with the higher load by shear cracks propagat ion to upper beam surface and propagate down up to CFRP sheet then a small area of CFRP with a concrete cover split at 63.22 kN for EB 7 and 66 kN for EB 8 after the applying load exceed s the strength capacity of RC specimen. In the last category (F WS), UB 9 failure was similar to UB 5. However, failure load was higher as it fails at 55 kN, that because the settlement of soil tends to reduce the impact of load on RC beam and increase its loading resistance. EB 10 failure mode almost similar to that in EB 7 and EB 8 but with less damage to the beam and higher load failure which is 73 kN. While EB 11 and EB 12 failure mode look like failure mode of EB 2 but the final mode w as a failure in section capacity and CFRP sheet debonding. In summary, all beams show similar failure mode at an early level of loading. T he most failure mode in this experiment was a failure of beam strength capacity and CFRP debonding. The bonding interfacial between CFRP sheet and concrete show high strength . Test results for NSM beams A ll tests result for this system shown in figures 3.10 for each beam test individually. The final results also are presented in T able 3.7 and 3.8. 3.3.2.1 Load carrying capacity T he load carrying capa bilities of the RC beams w ere observed during t he test for this category too to study the behavior of strengthened beams with NSM . The summary of the

PAGE 77

50 results is indicated in T able beams, standard deviation and the COV of tested beam speci mens. The same three unstrengthened specimens (control beams) that tested before considered the reference specimens for this category too. RC beams strengthened with NSM shows that NSM beams fail at higher load capacity and have higher standard deviation and COV (67.95 kN, 5.43, and 0.0799) respectively when the support condition is (F RS) than the beams that supported by (F WS) (63.85 kN, 3, and 0.0469) which is opposite to the first category; the ratio of decreasing is 6.03%, The presence of water impact the values of standard deviation and COV too but not that much as in the first category. The ratio is also decrease d to be 2.25% when there is no water in the soil (F DS) but less than (F WS), the (F DS) results are (66.42, 5.27, and 0.0793). A compariso n between unstrengthened RC beams and NSM beams shows that the beam load capacity increased when NSM system used too as the results indicate that the ratio of increasing are 37.8% for (F RS) case, 36.67% for (F DS) case, and 16.28% for case (F WS). 3.3.2.2 Load di splacement behavior The displacement of all beams specimen w as measured from mid span of beams in a similar way that done with EB system. The load displacement of NSM specimens with (F RS) results are provided on F igures 3.8.1 (a), 3.10.1 (a), 3.10.2 (a), and 3.10.3 (a). The results show that beams have similar load displacement behavior at an early stage of loading up to 40 kN. After 40 kN where the steel rebar start s yielding and the concrete start to crush, UB 1 lose its stuffiness as presented before. However, strengthen beams with NSM system show higher stiffness and higher load carrying capacity than UB 1 up to failure load. In addition , the NSM

PAGE 78

51 beams have low deflection as compared with the unstrengthen beam. The NSM system increase s the loading cap acity and stiffness of RC beams in case of (F RS). For beams with support condition (F DS), the load displacement results are provided on F igures 3.8.5 (a), 3.10.4 (a), 3.10.5 (a), and 3.10.6 (a). T he results show that the beams still have the same load di splacement trend at low loading level except for NSM 7 which show lower stiffness that others. After 48 kN, UB 5 fails While NSM beams keep having higher load and deflection which mean stiffer than UB 5. NSM 6 fail at a higher load than others. The effect of settlement is show n through significant results that show wide random values of failure loading with low displacement differences. T he NSM system increases the load capacity and stiffness of RC beams in case of (F DS). In the last category (F WS), the l oad displacement results are provided in F igures 3.8.9 (a), 3.10.7 (a), 3.10.8(a), and 3.10.9 (a). T he results show that the beams have different load displacement behavior from the beginning as the water presence in soil reduce the modulus of subgrade re action of soil and impact the result of testing beams. NSM 11 show the lower stiffness as it deflects more than other beams under the same load while NSM 10 shows high stiffness. The effect of 25% water present in soil is clearly seen as it a ffects the te st results and make s them varies. Both load and displacement var y in this case. The NSM system , in this case , increase s the load carrying capacity and beam resistance to settlement. In summary and if we compare between the three cases, it concludes that th e NSM system success to increase the load capacity of the RC also beams as EB system did before with different support condition with more deflection. The NSM beams show higher resistance when the support is rigid more than with soil settlement.

PAGE 79

52 3.3.2.3 Strain beh avior of EB beams The strain of all beams w as measured during the test in a similar way as in EB system which is shown previously using two PI gages . The first category (F RS) are presented in F igures 3.8.1 (b) and (c), 3.10.1 (b) and (c), 3.10.2 (b) an d (c), and 3.10.3 (b) and (c) for tension and compression zones. The results show that all beams tension strain increase gradually and beams strengthened with NSM system have low tension strain than the unstrengthened beam. The NSM beams have different ten sion strain as NSM 3 beam shows the lowest tensile strain while NSM 4 shows the higher tensile strain but still lower than UB 1. NSM system reduce s the tensile strain of RC beam. For compression zone in RC beams, strain in all beams ha s similar compressio n strain at low load level up to 40 kN except NSM 2 which has higher strain. After that, each beam behaves in a different way , but in general , the compression strain with NSM system has a similar strain that in unstrengthened beams as the compression zone is carried by concrete section capacity. For the second category (F DS) the result of strain are presented in F igures 3.8.5 (b) and (c), 3.10.4 (b) and (c), 3.10.5 (b) and (c), and 3.10.6 (b) and (c). their result show that the NSM system decrease s the st rain in tension zones except for NSM 8 which shows higher strain than UB 5. Even though they have a similar strain at early loading stage up to 5 kN. However, the results for compression zone show that the strain in compression for NSM system is higher th an the strain of unstrengthen beam for this category too. The result of strain for the last category which is (F WS) are presented in F igures 3.8.9 (b) and (c), 3.10.7 (b) and (c), 3.10.8 (b) and (c), and 3.10.9 (b) and (c). T he results were almost similar tensile strain up to 10 kN load. After that, UB 9 shows higher tensile strain than NSM

PAGE 80

53 strain even when there is a settlement in soil. In general conclusions, the tensile strain for beams with (F DS) suppor t is lower than the tensile strain of beams (F DS) and both conditions are lower than the tensile strain in (F WS) support condition , which mean s that settlement tend s to increase the tensile strain of RC beams. T he general picture of results is the NSM sy stem reduce the tensile strain of RC beams , but it has higher compression strain . However, the settlement of soil reduces the tensile and compression strain of RC beams. 3.3.2.4 CFRP strain Three NSM beams have strain gages on its CFRP strip but only one NSM be am that tested with (F RS) was able to get data from . Six strain gages were glued to beams and spread three on the right next to fixed support and three on the left next to hinge support. The strain gages have an equal distance of 150 mm (5.9 in) center to center along the CFRP strips on one side of it. Although the beam has six strain gages on it, only four of them work properly. However, the result shows that the strain was higher on mid span than the strain on other locations. Also, the strain on hinge s upport side was higher than the one on fixed support side from the strain gages H3 and F4.finally the strain increase gradually as the applied load increase in all locations. 3.3.2.5 Soil settlement Same work and explanation deal with soil that present in the pr evious section with EB system is done her for NSM. The result of this section is vibrated due to the impact of soil . The first category with (F DS) show s that the UB 5 has less deflection and settlement as it fails at

PAGE 81

54 a lower load than the NSM beams which shows higher load, deflection, and settlement . All soil has a slightly different modulus of subgrade reaction but within the range of loose sand. The second category (F WS) show that UB 9 has higher deflection and settlement under same load level than NSM beams. 3.3.2.6 Energy dissipation Energy dissipation was observed in this experiment . Figure 3.10.10 shows the energy dissipation bars for each specimen . For the first category (F RS) it ' s shown that the energy dissipation of unstrengthened beam ( 791.90 kN.mm) is higher than those that are strengthened with NSM system (average energy dissipation [E avg . ] is 373 kN.mm). However, for case two (F DS), the energy dissipation of unstrengthened beam is also less than those beams strengthened with NSM system. The results for energy dissipation are ( 501.51 and 679.89 kN.mm) for (UB 5 and NSM avg. ) respectively. While for the last case with (F WS) the energy dissipation in UB 9 is less than the NSM avg. as the result was (722.58 and 627.6 kN.mm) for UB 9 and NSM avg. respectiv ely. The conclusion is that e nergy dissipation of unstrengthened RC beams w ith rigid support w as higher than those unstrengthened within soil settlement . While the energy dissipation of RC beams strengthened with NSM system shows the opposite as it is high er with soil settlement . 3.3.2.7 Failure mode The failure mode of unstrengthened beams is presented in F igures 3.9.1, 3.9.5, and 3.9.9 for each case ; and failure mode for NSM system is presented in F igures 3.11. Most NSM beams have a similar failure mode. Table 3.9 show how the NSM beams behave under loading at each loading level up to its failure load capacity.

PAGE 82

55 In the first category with (F RS), the unstrengthened beam UB 1 failure is explained in previously in section 3.3.1.7. The beam finally fails by concrete crushing at point load at 49 kN. For NSM 2, NSM 3, and NSM 4 they fail in a similar way by starting with flexural cracks at mid span at 20 kN. After that, shear cracks propagate , and flexural vertical cracks near fixed hinge propagate too at load level be tween 30 50 kN. The cracks propagate until failure of beams. The final failure mode is CFRP strip debonding with concrete cover for all three NSM beams. However, NSM 2 and NSM 4 failure were next to hinge support at load (62.5 kN and 73.4 kN) respectively. While NSM 3 failed at 67.9 and failure was near fixed support side. For the second category (F DS), the failure mode has similar behavior for NSM 6 and NSM 8. It starts with flexural cracks at 25 kN at mid span. Then flexural vertical cracks develop at lo ad level 30 40 kN next to fixed support face. Shear cracks propagate at 45 kN for NSM 6 and 31 kN for NSM 8. Both beams cracks propagate up to failure load at 71.8kN and 65.9 kN respectively. The final failure mode was CFRP with concrete cover debonding. N SM 7 fails with different behavior which start s by flexural cracks near mid span at 20 kN, then vertical cracks near fixed support face at 25 kN. Shear cracks propagate at 42 kN , and finally the beam fails by propagat ing of shear cracks near fixed end supp ort and concrete 7 fails due to concrete beam strength capacity befor e it fails with CFRP strip debonding. The last case with (F WS), UB 9 failure was at 55 kN by shear cracks propagation and concrete crushing. NSM 10 f ailure mode almost similar to that in NSM 6 and NSM 8 by CFRP strip and concrete cover debonding, but with concrete crushing and spilling out on compression zone of the beam near shear cracks and the load failure is 66.1 kN. While NSM 11 and NSM -

PAGE 83

56 12 failur e mode look like failure mode of NSM 7 by fails due to RC beam strength capacity before it fails by CFRP debonding at 60kN and 64.8 kN respectively. Finally, all beams show similar failure mode at an early level of loading. T he most failure modes in this p hase with NSM system was also a failure of beam strength capacity and CFRP debonding. The bonding interfacial between CFRP strips and concrete show high strength . Comparison between EB and NSM system under settlement of soil If a compa r ison is made between RC beams that strengthening with EB system and the one strengthening with NSM system under settlement condi t ion , the compr e ssive load capacity of EB system shows better behav io r under higher settlement while NSM system shows better behav io r with rigid sup port. Overall , both system s increase the load carrying capacity of the RC beams , and both of them are considered a good solution for repairing concrete structures. For load displacement comparison, although both system s show good behavior, but NSM system w ith (F RS) condition shows higher deflection under higher load carrying capacity than EB system. For (F DS) case, NSM system is still stiffer than EB system as it behaves with low deflection and higher load carrying capacity. And for the last case, even th ough the EB beams fails at higher load, but the NSM beams show higher stiffness at its deflect less than EB at the same loading. In general, NSM system show s more efficiency than EB system for load displacement behavior. For a strain of section comparison , the tensile strain in NSM system is lower than in EB system. But, the compression strain in NSM system is slightly higher than EB at higher load level. The strengthen system decrease the tensile strain and increase compression strain of RC beams. If the compar i son is made between EB system and NSM system for what are

PAGE 84

57 getting f ro m available readings, the result shows that the strain on EB CFRP sheet was higher than the strain in NSM CFRP strip. The comparison between EB system and NSM system shows that wit h dry soil (DS) EB system has lower deflection and settlement than NSM system. However, with submerged soil (WS) NSM system shows lower deflection and settlement as CFRP strip make the beam stiffer under the higher settlement . For energy dissipation differ ence with both systems, the highest energy dissipation was with EB WS case and the lowest one was with NSM RS case. The energy dissipation of EB system is higher than energy dissipation of NSM system for all cases. For failure mode co m parison between EB a nd NSM, both of them show similar trend by fails either by CFRP and concrete cover debonding or by the capacity strength of RC beams sections.

PAGE 85

58 W/C 45% Cement(kg/m 3 ) 380 Water (kg/m 3 ) 205 Aggregate (kg/m 3 ) 1200 Sand (kg/m3) 700 Specimen Compressive Load at 28 days (kN) Compressive Stress at 28 days ( MPa ) C1 173.7 22.13 C2 187.98 23.94 C3 139.9 17.8 Average compressive stress 21.29 Table 3.1. Concrete mix de sign (21 MPa) Table 3.2. Compressive strength of concrete cylinders

PAGE 86

59 Table 3.3. Beam test matrix Externally bonded (EB) Near surface mounted (NSM) Spec. No. Strengthening condition Support cond ition Spec. No. Strengthening condition Support condition UB 1 Unstrengthened Fix ed Rigid hinge support UB 1 Unstrengthen Fix ed Rigid hinge support EB 2 Strengthened Fix ed Rigid hinge support NSM 2 Strengthened Fix ed Rigid hinge support EB 3 Strengthene d Fix ed Rigid hinge support NSM 3 Strengthened Fix ed Rigid hinge support EB 4 Strengthened Fix ed Rigid hinge support NSM 4 Strengthened Fix ed Rigid hinge support UB 5 Unstrengthened Fix ed Hinge on dry sand UB 5 Unstrengthen Fix ed Hinge on dry sand EB 6 Strengthened Fix ed Hinge on dry sand NSM 6 Strengthened Fix ed Hinge on dry sand EB7 Strengthened Fix ed Hinge on dry sand NSM 7 Strengthened Fix ed Hinge on dry sand EB 8 Strengthened Fix ed Hinge on dry sand NSM 8 Strengthened Fix ed Hinge on dry sand UB 9 Unstrengthened Fix ed Hinge on submerged sand UB 9 Unstrengthen Fix ed Hinge on submerged sand EB 10 Strengthened Fix ed Hinge on submerged sand NSM 10 Strengthened Fix ed Hinge on submerged sand EB 11 Strengthened Fix ed Hinge on submerged sand NSM 11 Stren gthened Fix ed Hinge on submerged sand EB 12 Strengthened Fix ed Hinge on submerged sand NSM 12 Strengthened Fix ed Hinge on submerged sand

PAGE 87

60 Spec. No. Support condition P u (kN) Average P u (kN) Standard deviation Coefficients of variation UB 1 F RS 49.308 49.308 X X EB 2 F RS 53.835 56.46 2.64 0.0467 EB 3 F RS 56.435 EB 4 F RS 59.11 UB 5 F DS 48.596 48.596 X X EB 6 F DS 59.783 63.04 3.17 0.0502 EB7 F DS 63.222 EB 8 F DS 66.111 UB 9 F WS 54.910 54.910 X X E B 10 F WS 75.938 68.458 6.56 0.0958 EB 11 F WS 63.692 EB 12 F WS 65.744 Spec. No. Strengthening condition Support condition P u (kN) b (mm) S1 (mm) s 2 (mm) s avg. (mm) UB 1 Unstrengthened F RS 49.308 11.762 ------EB 2 Strengthened F RS 53.835 8.982 ------EB 3 Strengthened F RS 56.435 8.916 ------EB 4 Strengthened F RS 59.11 8.4 ------UB 5 Unstrengthened F DS 48.596 15.288 17.120 9.064 13.092 EB 6 Strengthened F DS 59.783 21.848 19.616 12.891 16.253 EB7 Strengthened F DS 63.222 13.481 11.688 14.416 13.052 EB 8 Strengthened F DS 66.111 32.844 33.813 6.824 13.495 UB 9 Unstrengthened F WS 54.910 22.000 3 1.000 25.400 28.200 EB 10 Strengthened F WS 75.938 44.258 67.902 66.970 67.436 EB 11 Strengthened F WS 63.692 26.775 40.650 47.207 43.929 EB 12 Strengthened F WS 65.744 39.747 63.049 63.484 63.267 Table 3. 4. Monotonic EB test results Table 3.5. Test results of beams bonded with EB C FRP sheet

PAGE 88

61 Beam NO. Load level (kN) 10 20 20 30 30 40 4 0 50 50 60 >60 UB 1 Flexural cracks at 10 kN Flexural cracks increase and propagate Shear cracks propagate at 30 kN Concrete crush and beam f ail at 49.31 kN ------EB 2 ---Flexural cracks at 20 kN Shear cracks propagate at 30 kN Cracks propagate Shear cracks propagate up to beam bottom edge near CFRP and CFRP debond at 53.83 kN ---EB 3 ------Flexural cracks at 30 kN and Shear cracks propagate at 40 kN CFRP and concrete cover peeled off at 56.4 kN ---EB 4 Flexural cracks at 18 kN Flexu ral cracks increase and propagate Shear cracks propagate at 32 kN Cracks propagate CFRP debond near fix support at 59.1 kN ---UB 5 ---Flexural cracks at 20 kN Shear cracks propagate at 35 kN Beam fails by concrete crush and Shear at 48.6 kN ------EB 6 ---Flexural cracks at20 kN Shear cracks propagate at 35 kN Concrete crush at 45 kN CFRP debond at 59.7 kN ---EB7 ---Flexural cracks at25 kN Flexural cracks increase and propagate Shear cracks propagate at 45 kN Concrete crush and spoiled ou t at 60 kN CFRP debond and concrete crush at 63.22 kN EB 8 ---Flexural cracks at25 kN Shear cracks propagate at 40 kN Cracks increase and propagate Cracks propagate CFRP debond and concrete crush at 66.1 kN UB 9 Flexural cracks at10 kN Flexural crack s increase and propagate Shear cracks propagate at 35 kN Concrete crush at 48 kN Beam fails by concrete crush and Shear at 55 kN ---EB 10 Flexural cracks at10 kN Flexural cracks increase and propagate Flexural cracks increase and propagate Shear cracks propagate at 45 kN Cracks increase and propagate Concrete crush near fix end at 75.9 kN EB 11 ---Flexural cracks at20 kN Flexural cracks increase and propagate Shear cracks propagate at 47 kN Concrete crush at 50 kN CFRP debond at 63.7 kN EB 12 ---F lexural cracks at20 kN Shear cracks propagate at 35 kN Cracks increase and propagate Cracks increase and propagate CFRP debond at 65.7 kN Table 3.6. Failure modes of beams bonded with EB CFRP sheet

PAGE 89

62 Spec. No. Support condition Pu(kN) Average Pu (kN) Standard deviation Coefficients of variation UB 1 Fix ed Rigid hi nge support 49.308 49.308 ----NSM 2 Fix ed Rigid hinge support 62.547 67.95 5.43 0.0799 NSM 3 Fix ed Rigid hinge support 67.903 NSM 4 Fix ed Rigid hinge support 73.41 UB 5 Fix ed Hinge on dry sand 48.596 48.596 ----NSM 6 Fix ed Hinge on dr y sand 71.899 66.42 5.27 0.0793 NSM 7 Fix ed Hinge on dry sand 61.381 NSM 8 Fix ed Hinge on dry sand 65.982 UB 9 Fix ed Hinge on submerged sand 54.91 54.91 ----NSM 10 Fix ed Hinge on submerged sand 66.195 63.85 3 0.0469 NSM 11 Fix ed Hinge on sub merged sand 60.467 NSM 12 Fix ed Hinge on submerged sand 64.881 Spec. No. Strengthening condition Support condition Pu(kN) b (mm) s avg. (mm) UB 1 Unstrengthened F RS 49.308 11.762 --NSM 2 Strengthened F RS 62.547 10.193 --NSM 3 Strength ened F RS 67.903 9.521 --NSM 4 Strengthened F RS 73.41 11.6 --UB 5 Unstrengthened F DS 48.596 15.288 13.092 NSM 6 Strengthened F DS 71.899 21.726 21.924 NSM 7 Strengthened F DS 61.381 20.007 28.223 NSM 8 Strengthened F DS 65.982 19.900 17.967 UB 9 Unstrengthened F WS 54.91 22 28.2 NSM 10 Strengthened F WS 66.195 16.677 22.9530 NSM 11 Strengthened F WS 60.467 22.639 36.323 NSM 12 Strengthened F WS 64.881 20.826 35.094 Table 3.8. Test results of beams bonded with NSM CFRP strip Table 3.7. Monotonic NSM test results

PAGE 90

63 Table 3. 9 . Failure modes of beams bonded with NSM FRP strips Beam NO. Loa d level (kN) 10 20 20 30 30 40 40 50 50 60 >60 UB 1 Flexural cracks at 10 kN Flexural cracks increase and propagate Shear cracks propagate at 30 kN Concrete crush and beam fail at 49.31 kN ------NSM 2 Flexural cracks at 20 kN Flexural cracks in crease and propagate flexural cracks propagate Shear cracks propagate at 45 kN and vertical cracks near fixed support at 52kN Cracks propagate CFRP debond at 62.5 kN NSM 3 Flexural cracks at 20 kN Flexural cracks increase and propagate Vertical cracks at fix support at 39 kN and Shear cracks propagate at 45 kN Cracks propagate CFRP and concrete cover peeled off at 67.9 kN NSM 4 Flexural cracks at 20 kN Flexural cracks increase and propagate Flexural cracks increase and propagate Shear cracks propaga te at 45kN and vertical cracks propagate at fix end at 50 kN CFRP and concrete cover peeled off at 73.4 kN UB 5 Flexural cracks at 20 kN Flexural cracks propagate Shear cracks propagate at 35 kN Beam fails by concrete crush and Shear at 48.6 kN ------NSM 6 ---Flexural cracks at 25 kN Vertical cracks propagate at 35 Kn near fixed end. Shear cracks at 45 kN Cracks propagate CFRP and concrete cover debond at 71.8 kN NSM 7 Flexural cracks at 20 kN Vertical cracks near fixed end at 25 kN Flexural cra cks increase and propagate Shear cracks propagate at 42 kN Cracks propagate Failure due to shear cracks and concrete crush at 61.3 kN NSM 8 ---Flexural cracks at24 kN and shear cracks at 29kN Shear cracks propagate at 31 kN Cracks increase and propagat e Cracks propagate CFRP and concrete cover debond at 65.9 UB 9 Flexural cracks at10 kN Flexural cracks increase and propagate Shear cracks propagate at 35 kN Concrete crush at 48 kN Beam fails by concrete crush and Shear at 55 kN ---NSM 10 Flexural c racks at 7 kN Flexural cracks increase and propagate Shear cracks propagate at 37 kN Cracks increase and propagate Cracks increase and propagate CFRP and concrete cover debond at 66.1kN NSM 11 Flexural cracks at 18 kN Vertical cracks near fixed end at 23 kN Shear cracks propagate at 34 kN Cracks propagate Cracks propagate Failure due to concrete crush and shear cracks at 60 kN NSM 12 Flexural cracks at 17 kN Vertical cracks near fixed end at 25kN Cracks increase and propagate Shear cracks propagate at 45 kN Cracks increase and propagate Failure due to connection of shear cracks with vertical cracks near fix end at 64.8 kN

PAGE 91

64 Figure 3 . 1 . Specimen dimensions and details (mm) : (a) cross section near hinge support; (b) cross section near fix support; (c) beam dimension and reinforc ement detail; (d) beam with groove dimension and reinforcement (d) ( c ) ( b ) ( a )

PAGE 92

65 ( b ) ( a ) Figure 3 . 2 . Specimen with CFRP details (mm ): (a) EB CFRP sheet; (b) NSM CFRP strip Figure 3.3. Cylinder test for compressive strength

PAGE 93

66 (a) ( b ) ( c ) ( d ) ( e ) Figure 3.4. Steel cage fabrication: (a) ba r cutting; (b) stirrup fabrication; (c) main steel bar bending; (d) steel bars after ben ding; (e) fabricated steel cage

PAGE 94

67 (b) (a) (c) ( d ) Figure 3.5. Preparation: (a) wood f orm; (b) mixer; (c) RC be ams after stripping; (d) curing

PAGE 95

68 Figure 3.5. Preparation (continued): (e) cleaning surface; (f) gluing CFRP sheets; (g) bonding CFRP strip ( e ) ( f ) ( g )

PAGE 96

69 Figure 3.6. Test setup with rigid support

PAGE 97

70 Figure 3.7. Test setup with dry sand (F DS)

PAGE 98

71 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0100 0.0200 0.0300 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain Figure 3.8. 1. Test result of UB 1: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression (a) ( b ) ( c )

PAGE 99

72 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0010 0.0020 0.0030 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) Figure 3.8.2 Test result for EB 2: (a) load displacement; (b) PI gage strain in tension; (c ) PI gage strain in compression

PAGE 100

73 ( d ) 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035 -600 -450 -300 -150 0 150 300 450 600 Strain Distance fom CL(mm) 20% Pu 40% Pu 60% Pu 80% Pu 100% Pu Hinge Fix ( e ) Figure 3.8.2 Test result for EB 2 (continued): (d) FRP strain at different locations; (e) FRP str ain at different loading stages

PAGE 101

74 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( c ) ( b ) Figure 3.8.3. Test result for EB 3: (a) load displacement; (b) PI gage strain in tension; (c ) PI gage strain i n compression

PAGE 102

75 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0030 0.0060 0.0090 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) Figure 3.8.4. Test result for EB 4 : :(a) load displacement; (b) PI gage strain in tension; (c ) PI gage strain in compression

PAGE 103

76 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.8.5 Test result for UB 5: (a) load displac ement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure ( kPa ) Sand settlement (mm) UB-5 S1 UB-5 S2 UB-5 S avg.

PAGE 104

77 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement(mm) 0 20 40 60 80 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.8.6 Test result for EB 6: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pres sure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure (kPa) Sand settlement (mm) EB-6 S1 EB-6 S2 EB-6 S avg.

PAGE 105

78 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain 0 20 40 60 80 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement(mm) (a) ( b ) ( c ) ( d ) Figure 3.8.7 Test result for EB 7: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure (kPa) Sand settlement (mm) EB-7 S1 EB-7 S2 EB-7 Savg.

PAGE 106

79 0 20 40 60 80 0.000 0.001 0.002 0.003 0.004 Load (kN) FRP strain EB-7 H1 EB-7 H2 EB-7 H3 EB-7 F4 EB-7 F5 EB-7 F6 Figure 3.8.7 Test result for EB 7 (continued): (e) FRP strain at different locations; (f) FRP str ain at different loading stages ( f ) ( e )

PAGE 107

80 0 20 40 60 80 0 10 20 30 40 50 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain Figure 3.8.8 Test result for EB 8: (a) load displacement; (b) PI gage strain in t ension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) (a) ( b ) ( c ) ( d ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure (kPa) Sand settlement (mm) EB-8 S1 EB-8 S2 EB-8 S avg.

PAGE 108

81 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.8.9 Test result for UB 9: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 20 40 Pressure ( kPa ) Sand settlement (mm) UB-9 S1 UB-9 S2 UB-9 S avg.

PAGE 109

82 0 20 40 60 80 0 10 20 30 40 50 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0002 0.0004 0.0006 0.0008 0.0010 Load (kN) Beam strain 0 20 40 60 80 -0.0005 -0.0003 -0.0001 0.0001 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.8.10 Test result for EB 10: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 50 Pressure ( kPa ) Sand settlement (mm) EB-10 S1 EB-10 S2 EB-10 S avg.

PAGE 110

83 0 20 40 60 80 0 10 20 30 40 50 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.8.11 Test result for EB 11: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 50 Pressure ( kPa ) Sand settlement (mm) EB-11 S1 EB-11 S2 EB-11 S avg.

PAGE 111

84 0 20 40 60 80 0.0000 0.0010 0.0020 0.0030 0.0040 Load (kN) Beam strain 0 20 40 60 80 0 10 20 30 40 50 Load (kN) Displacement (mm) 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.8.12 Test result for EB 12: (a) load displacement; (b) PI g age strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 50 60 70 Pressure ( kPa ) Sand settlement (mm) EB-12 S1 EB-12 S2 EB-12 S avg.

PAGE 112

85 0 20 40 60 80 0.000 0.001 0.001 0.002 0.002 0.003 Load (kN) FRP Strain EB-12 H1 EB-12 H2 EB-12 H3 EB-12 F4 EB-12 F5 EB-12 F6 0 0.0005 0.001 0.0015 0.002 0.0025 -600 -450 -300 -150 0 150 300 450 600 Strain Distance fom CL (mm) 20%Pu 40%Pu 60%Pu 80%Pu 100%Pu Hinge fix Figure 3.8.12 Test result for EB 12 (continued): (e) FRP strain at different locations; (f) FRP str ain at different l oading stages ( e ) (f)

PAGE 113

86 0 400 800 1200 1600 Energy ( kN. mm) UB-5 EB-6 EB-7 EB-8 0 500 1000 1500 2000 2500 Energy ( kN. mm) UB-9 EB-10 EB-11 EB-12 0 500 1000 1500 2000 Energy ( kN. mm) UB-1 EB-RS avg. UB-5 EB-DS avg UB-9 EB-WS avg. 0 200 400 600 800 1000 1200 Energy ( kN. mm) UB-1 EB-2 EB-3 EB-4 (a) ( b ) ( c ) ( d ) Figure 3.8.13 Energy dissipations for EB bea ms: (a) energy dissipation for F RS; (b) energy dissipation for F DS; (c) energy dissipation for F WS, (d) average energy diss ipation for each category

PAGE 114

87 (a) ( b ) ( c ) ( d ) Figure 3.9.1. Failu re mode for UB 1: (a) flexural cracks at mid span at 10 kN loading and shear cracks at 30 kN; (b) concrete crush at 48kN; (c) beam deflection is clear; (d) beam failed by concrete crush ing at 49.31 kN

PAGE 115

88 (a) ( b ) ( c ) ( d ) Figure 3.9.2. Failure mode of EB 2: (a) flexural crack at mid span develop at 20 kN loading and shear cracks at 30 kN; (b) shear cracks develop and concrete crush at 45kN and FRP debond at its edge at 53kN; (c) CFRP debond and connect the shear crack; (d) beam failed b y FRP debonding at its edge a nd concrete crushing at 53.83kN

PAGE 116

89 Figure 3.9.3. Failure mode of EB 3: (a) flexural crack at mid span develop at 30 kN loading; (b) shear cracks develop at 40 kN; (c) CFRP sheet with concrete cover ar e peeled out at 55 kN loading; (d) another view of peel out; (e) beam failed by FRP and con crete cover peel out at 56.4 kN ( a ) ( b ) ( c ) ( d ) (e)

PAGE 117

90 (a) ( b ) ( c ) ( d ) Figure 3.9.4. Failure mode of EB 4 : (a) flexural cracks at mid span at 18 kN; (b) and (c) shear cracks start developing at 32 kN; (d) beam fails due to CFRP sheet debond ing at 59 kN near fixed support

PAGE 118

91 Figure 3.9.5. Failure mode of UB 5: (a) flexural crack at mid span develop at 20 kN loading and concrete crush at point load; (b) shear cr acks develop at 35 kN; and Beam failed by concrete crush and shear cracks next to fi xed end at point load at 48 kN (a) ( b )

PAGE 119

92 Figure 3.9.6. Failure mode of EB 6: (a) flexural crack at mid span develop at 20 kN loading and shear cracks at fixed support s ide, concrete crush at point load about 45 kN then FRP sheet debond at 59 kN; (b) shear cracks develop on soil side too; (c) CFRP sheet debonding; (d) beam after failure by CFRP debonding at 59.78 kN (a) ( b ) ( c ) ( d )

PAGE 120

93 Figur e 3.9.7. Failure mode of EB 7: (a) flexural crack at mid span develop at 25 kN loading; (b) shear cracks develop at 45kN on both side from the edge of FRP sheet; (c) CFRP sheet debonding on soil side and concrete crush and spoiled out about 60 kN; (d) beam after failure by C FRP debonding an d concrete crushing at 63.22 kN (a) ( b ) ( c ) ( d )

PAGE 121

94 ( a ) ( b ) (c) ( d ) Figure 3.9.8. Failure mode of EB 8: (a) flexural crack at mid span develop at 25 kN loading; (b) Shear cracks develop at 40kN on the fixed side; (c) shear cracks develop at 50 on the soil side from the edge of FRP sheet; (d) CFRP sheet debonding after connect with shear cracks at its edge near fix side at 65 kN

PAGE 122

95 Figure 3.9.8. Failure mode of EB 8 (continued) : (e) concrete crush at the area of FR P debonding and shear cracks at 66 kN; (f) other side of FRP sheet connect shear cracks too (e) ( f )

PAGE 123

96 (a) ( c ) ( d ) ( b ) Figure 3.9.9. Failure mode of UB 9: (a) flexural crack at mid span develop at 10 kN loading; (b) shear cracks develop at 35 kN on the fixed side; (c) concrete crush near point load at 48 kN; (d) beam fail due to concrete crush and shear cracks between fixed side and nearest point load at 55 kN

PAGE 124

97 Figure 3.9.10. Failure mode of EB 10: Flexural crack at mid span develop at 20 kN loading and shear cracks develop at 45 kN on the fixed side, then concr ete crush near fix end at 73 kN (c) ( a ) ( b ) ( d )

PAGE 125

98 Figure 3.9.11. Failure mode of EB 11: (a) flexural crack at mid span develop at load 20 kN; (b) sand settl ement increase beam deflection; (c) shear cracks develop at 47 kN on the fixed side, then concrete crush near point load at 50 kN, and finally CFRP debond near fix end at 63 kN ; (d) beam after failure ( a ) ( b ) ( c ) (d)

PAGE 126

99 Figure 3.9.12. Failure m ode of EB 12: (a) Flexural crack at fix end at 20 kN loading and shear cracks develop at 35 kN on the fixed side; (b) then shear crack develop and reach FRP edge then the beam fails finally by CFRP debonding near fix end at 65 kN; (c) concrete cover peeled off in top surface near shear cracks; (d) concrete cover with CFR P in bottom surface peeled off ( a ) ( b ) ( c ) (d)

PAGE 127

100 0 20 40 60 80 0 5 10 15 20 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 Load (kN) Beam strain 0 20 40 60 80 -0.0020 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) Figure 3.10.1. Test result of NSM 2: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression

PAGE 128

101 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0001 0.0002 0.0003 0.0004 0.0005 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) Figure 3.10.2. Test result of NSM 3: (a) load displacement; (b) PI gage strain in tension; (c ) PI gage strain in compression

PAGE 129

102 0 20 40 60 80 0 5 10 15 20 25 30 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) Figure 3.10.3. Test result of NSM 4: (a) load displacement; (b) PI gage strain in tension; (c ) PI gage strain in c ompression

PAGE 130

103 0 20 40 60 80 0.000 0.002 0.004 0.006 0.008 Load (kN) FRP strain NSM-4 H1 NSM-4 H2 NSM-4 H3 NSM-4 F4 NSM-4 F5 NSM-4 F6 0 0.001 0.002 0.003 0.004 0.005 0.006 -600.00 -450.00 -300.00 -150.00 0.00 150.00 300.00 450.00 600.00 Strain Distance fom CL(mm) 20% Pu 40% Pu 60% Pu 80% Pu 100% Pu Hinge Fix Figure 3.10.3. Test result of NSM 4 (continued): (e) FRP strain at different locations; (f) FRP strain at diffe rent loading stages (d) ( e )

PAGE 131

104 0 20 40 60 80 0 20 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 Load (kN) Beam strain 0 20 40 60 80 -0.0025 -0.0020 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.10.4. Test result of NSM 6: (a) load displacement; (b) PI g age strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure ( kPa ) Sand settlement (mm) NSM-6 S1 NSM-6 S2 NSM-6 S avg.

PAGE 132

105 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0005 0.0010 0.0015 0.0020 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.10.5. Test result of NSM 7: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compress ion; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure (kPa) Sand settlement (mm) NSM-7 S1 NSM-7 S2 NSM-7 S avg.

PAGE 133

106 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0050 0.0100 0.0150 Load (kN) Beam strain 0 20 40 60 80 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain ( a ) ( b ) (c ) ( d ) Figure 3.10.6. Test result of NSM 8: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 Pressure (kPa) Sand settlement (mm) NSM-8 S1 NSM-8 S2 NSM-8 S avg.

PAGE 134

107 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0005 0.0010 0.0015 0.0020 Load (kN) Beam strain 0 20 40 60 80 -0.0020 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.10.7. Test result of NSM 10: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 50 Pressure (Mpa) Sand settlement (mm) NSM-10 S1 NSM-10 S2 NSM-10 S avg.

PAGE 135

108 0 20 40 60 80 0 10 20 30 40 50 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0005 0.0010 0.0015 0.0020 Load (kN) Beam strain 0 20 40 60 80 -0.0005 -0.0004 -0.0003 -0.0002 -0.0001 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.10.8. Test result of NSM 11: (a) load displacement; (b) PI gage strain in tension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 50 Pressure (kPa) Sand settlement (mm) NSM-11S1 NSM-11 S2 NSM-11 S avg.

PAGE 136

109 0 20 40 60 80 0 10 20 30 40 Load (kN) Displacement (mm) 0 20 40 60 80 0.0000 0.0005 0.0010 0.0015 0.0020 Load (kN) Beam strain 0 20 40 60 80 -0.0012 -0.0009 -0.0006 -0.0003 0.0000 Load (kN) Beam strain (a) ( b ) ( c ) ( d ) Figure 3.10.9. Test result of NSM 12: (a) load displacement; (b) PI gage strain in t ension; (c) PI gage strain in compression; (d) pressure settlement (loaded area = 0.09 m 2 ) 0 50 100 150 200 250 300 0 10 20 30 40 50 Pressure (kPa) Sand settlement (mm) NSM-12 S1 NSM-12 S2 NSM-12 S avg.

PAGE 137

110 0 200 400 600 800 1000 1200 Energy ( kN. mm) UB-1 NSM-2 NSM-3 NSM-4 0 200 400 600 800 1000 Energy ( kN. mm) UB-5 NSM-6 NSM-7 NSM-8 (a) ( b ) ( c ) ( d ) Figure 3.10.10. Energy dissipations for NSM bea ms: (a) energy dissipation for F R S; (b) energy dissipation for F DS ; (c) energy dissipation for F WS, (d) average energ y dissipation for each category 0 200 400 600 800 1000 Energy ( kN. mm) UB-9 NSM-10 NSM-11 NSM-12 0 200 400 600 800 1000 Energy ( kN. mm) UB-1 NSM-RS avg. UB-5 NSM-DS avg UB-9 NSM-WS avg.

PAGE 138

111 Figure 3.11.1. Failure mode of NSM 2: (a) flexural crack at mid span at 20 kN loading and shear cracks start and develop at 45 kN on the fixed side whi le vertical cracks near fixed end have been seen clearly at 52 kN; (b) cracks develop near CFRP strip edge and the beam fails by CFRP debonding near hinge end at 62 kN; (c) CFRP strip de bonding; (d) beam after failure (a) ( b ) ( c ) ( d )

PAGE 139

112 (a) ( b ) ( c ) ( d ) Figure 3.11.2. Failure mode of N SM 3: (a) flexural crack at mid span at 20 kN and vertical cracks near fix end at 39 kN while shear cracks start developing at 45 kN between mid span and support on both sides; (b) cracks develop near FRP strip edge and the beam fails by FRP debonding with concrete cover around it next to fixed end support at 67 kN; (c) other side view of debonding; (d ) beam main steel reinforcement

PAGE 140

113 (a) ( b ) ( d ) ( c ) Figure 3.11.3. Failure mode of NSM 4 : (a) flexural cracks at mid span at 20 kN; (b) vertical cra cks next to fix face at 50 kN and shear cracks start developing at 45 kN; (c) CFRP strip debond with some of concrete cover at 73 kN; (d) test specimens after failure due to CFRP debonding

PAGE 141

114 (a) (a) ( c ) ( d ) Figure 3.11.4. Failure mode of NSM 6: (a) flexural crack at mid span at 25 kN and vertical cracks near fix end at 25 kN; (b) shear cracks start developing at 45 kN between mid span and support on both sides and soil settlement increase; (c) cracks develop near CFRP strip edge and the beam fails b y CFRP debonding with some concrete cover next to fixed end support at 72 kN; (d) crack s between fix end and mid span

PAGE 142

115 (e) ( f ) Figure 3.11.4. Failure mode of NSM 6 (continued): (e) Cracks between hinge support and mid span; (f) FRP str ip debonding from its end

PAGE 143

116 (a) ( b ) ( c ) ( d ) Figure 3.11.5. Failure mode of NSM 7 : (a) flexural crack at mid span at 20 kN and vertical cracks near fix end at 25 kN while Shear cracks start developing at 42 kN between mid span and support on both sides and soil settlement increase; (b) shear crack connect point load with the bottom edge of fix end at 59 kN; (c) beam fails at 61 kN due to shear cracks and concrete crush and spill out; (d) sand settlement

PAGE 144

117 (a) ( b ) ( c ) ( d ) Figure 3.11.6. Failure mode o f NSM 8 : (a) flexural crack at mid span at 24 kN and vertical cracks near fixed end at 29 kN while Shear cracks start developing at 31 kN between mid span and fixed support; (b) soil settlement increase and cracks increase and develop; (c) beam fails at 66 kN due to FRP strip debonding with concrete cover surrounding it on fix end side; (d) concrete co ver with FRP strip is debonding

PAGE 145

118 (a) ( b ) ( c ) Figure 3.11.7. Failure mode of NSM 10 : (a) flexural crack at mid span at kN and Shear cracks start developing at 37 kN between mid span and fixed support; (b) beam fails at 66 kN due to FRP strip debonding with concrete cover surrounding it on fix end side; (c) concrete cover spoi led out (d) CFRP strip debonding ( d )

PAGE 146

119 (a) ( b ) ( c ) ( d ) Figure 3.11.8. Failure mode for NSM 11 : (a) Vertical cracks next to fix face at 18 kN then flexural cracks at mid span at 23 kN and shear cracks start developing at 34 kN between mid span and fixed support while beam inclined due to soil settlement; (b) Cracks are incre asing and developing; (c) Beam fails at 60 kN due to developing of shear cracks and concrete crushing; (d) test specimens after failure

PAGE 147

120 (a) ( b ) ( c ) ( d ) Figure 3.11.9. Failure mode for NSM 12 : (a) flexural cracks at mid span at 17 kN then Vertical cracks next to fixed support face at 25 kN and shear cracks start developing at 45 kN between mid span and fixed support while; (b) cracks are increasing and developing near fix end side; (c) soil settlement increase and cracks increase on the same side o f soil; (d) test specimens after it fails at 65 kN due to developing of vertical cr acks at fixed end support face

PAGE 148

121 CHAPTER IV B EHAVIOR OF CONTINUOUS BEAMS STRENGTHENED WITH EB CFRP SHEETS AND NSM CFRP STRIPS SUBJECTED TO DIFFERENTIAL SETTLEMENT 4.1 General overview This experimental p rogram is conducted to examine the flexural behavior of continuous RC beams strengthening with CFRP subjected to differential settlement in addition to the short one span RC beams discussed in the previous chapter . In this chapter , the RC beams have two sp an and same two strengthening techniques with CFRP were used here too but with some differences: E xternally Bonded (EB) CFRP sheets and near surface mounted (NSM) CFRP strips . The support conditions are only two for continuous beam specimen which is : rigid hinge sup port denoted as (R) and rigid hinge support on 25% w e sandy soil denoted as (S) so that there are two cases ( R R R ) and (R R S) . Two loading methods Monotonic and cyclic loading are used here too. This chapter will describe all work related to t his part of research on the following sections: S ection 4 .2 provides a description of the experimental program which includes the material properties of the RC beam specimens, soil used for test specimens, fabrication and preparation of test specimens, and experimental setup and instrumentation. S ections 4 .3 and present the result and discussions for all ten continuous RC beams . The results include load carrying capacity, l oad d isplacement behavior and failure mode, l oad s train in tension, load s train in compression, p ressure s ettlement of soil, l oad FRP strain, and e nergy dissipation up to peak failure load.

PAGE 149

122 4.2 Experimental program 4.2.1 Test specimens Total of 10 continuous RC beams were used in this program. The RC beams sample is made with similar compressive s trength of 21 MPa (3045.79 psi) of short beams, and with dimensioned of each as following: 2800 mm ( 110.24 in) long x 165 mm (6.5 in) heights x 100 mm (4 in) wide. The tension and compression reinforcements were made of two steel rebar no.3 with a dia meter of 9.5 mm (0.375 in), and on the same locat ion at an effective depth of 135 mm (5.3 in) for tension reinforcement . The compression reinforcement bars are located at 25 mm (1 in) from the top beam surface and located at both ends of the beam and its m id span with a total length of 570 mm (22.44 in) for each location . shear stirrups were included using rebar no.2 with diameter of 6.35 mm (0.25 in) and with spacing at 76.2 mm (3 in) center to center. Figure 4 .1 shows the beam specimens dimensions and de tails. Four of RC beam were having the groove of size 1100 mm (43.3 in) x 25 mm (1 in) deep x 1.7 mm (0.5 in) wide at the middle of the bottom face of the beam at each span and on center of beam on the middle top face as shown in figure 4.1 (d). After conc rete curing achieved, the NSM Aslan 500 TM CFRP strip with a dimensions 2mm (0.0079 in) thick x 16 mm (0.63 in) deep x 1100 mm ( 43.3 in) long is inserted and bonded with conventional epoxy adhesive as shown previously in figure 3 .2 (b). A nd then curing app ly for seven days. Also, four RC beams having CFRP sheets with dimensions 1100 ( 43.3 .4 in) long x 100 mm (4 in) wide x 0.165 mm (0.0065 in) thick. The CFRP sheets are externally bonded to the middle bottom face of the beams at each span and one more at th e center of beams at the top face. U wrap CFRP sheet is used here at both end of CFRP sheet to improve load carrying capacity, prevent CFRP sheet to debond early from its end, and improve RC beam resistance to shear stresses.

PAGE 150

123 The CFRP sheet is glued to RC beam using the same conventional epoxy adhesive which shown in figure 4 .2 ( g ). After gluing CFRP sheet and strips the beams left for a week (7 days) for curing the epoxy. The rest two beams were left without strengthening for comparison purposes . 4.2.2 Material s Same mix design, materials , and method that used previously is used in this section too. The only difference is using cement type three so the curing time is one week instead of 28 days. Concrete cylinders were cast with the beams and tested for compress ive strength after 7 days of curing and after 10 days . A compressive test machine also used to test cylindrical specimens with dimensions of 100 mm (4 in) diameter x 200 mm (8 in) height. figure 4 . 2 shows the concrete cylinder specimen after it tested (cru shed) and machine reading. the average compressive strength for cylindrical specimens was 18.75 MPa ( 2719.45 psi) for seven days curing and 31.69 MPa ( 4596.2459 psi) , and the results are listed in tables 4 . 1 and 4.2 respectively . 4.2.3 Specimen preparation RC beams with a dimension discussed above is manufactured and cast in the laboratory. The same process of fabricating a concrete beam illustrated in the previous chapter is used here. Steel cages and Wood frame are fabricated in the laboratory. Two hooks f or each RC beam were fabricated and connected to steel cage so the carrying the beam be easy using the crane in the laboratory. All beams were cast and cured in the laboratory in the similar previous way , and all process are shown in figure 4.3.

PAGE 151

12 4 4.2.4 Test setup and instrumentation All RC beams have two span and three supports. T wo support conditions are used here (R R R) and (R R S) to simulate the differential settlement of soil as it is in reality when part of the structure set on weak soil or some soil prope rties change on the part of ground the structure set on . T he continuous RC beams were supported with an effective two span s of 1 3 00 mm ( 51.18 in) and tested under four point load until failure happened . A ll tests were done by using a hydraulic jack and rig id frame. The flexural test was done by applying a monotonic load to simu late a static loading condition or by applying cyclic loading. T he tests were controlled manually by applying the load at a constant time and pressure with one rise and press of jack lever arm every 10 sec. For cyclic loading, the percentage of 0.1 of failure load capacity of specimens that been tested with monotonic load at same conditions is chosen to apply load on each cycle. This percentage increases 0.1 each cycle up to load capac ity of the previous spaceman that tested with monotonic loading. I f the last one is loaded until the beam fails. Figure 4 . 4 illustrates test set up with hydraulic jack for ( R R R ) support, and Figure 4 . 5 illustrate tes t set up for ( R R S) support. The b lue load cell was used to record the load reading at each stage of the test. Three PI gages also used to get the tension strain at both mid span and mid support of the RC beams on tension zones. While three strain gages were used at the same locations but on compression , fiber to get compression strain of continuous RC beam at these locations . Another three s train gages were used to observe the strain on the middle of FRP sheet or FRP strip. In addition , three linear pot entiometers were used to measure the deflection of the beam at its mid span and the settlement of soil. All the above instrumentation was installed on the RC beams and connected to data acquisition device, which is used to get the data and record it by sof tware to

PAGE 152

125 a computer system that is connected to the data acquisition in a similar way that done for previous short beams . The details and instrumentation of each continuous RC beams are provided in figures 4.6. 4.2.5 Test m atrix T otal ten continuous RC beams were tested i n this phase of experiments. Four continuous RC beams were strengthened with EB FRP sheets, and Four continuous RC beams were strengthened with NSM CFRP strips. Two continuous RC beams were kept with no strengthening as control beams for compa rison purposes . Table 4 .3 lists information about the continuous RC beams tested with their test conditions. RC Beams strengthened with FRP sheet were denoted with C EB referring to continuous beam externally bonded system. RC beams strengthened with CFRP s trips were denoted with C NSM referring to continuous beam with the near surface mounted system. A nd unstrengthen continuous RC beams were denoted with C UB. 4.1 Test results and discussion T he results obtained from the experimental testing of continuous RC bea ms that are strengthened with CFRP sheets and strips , and the unstrengthened beams are presented in this section . T he results of the experiments include the curves of load versus displacement or deflection of the beam at both mid span of beam , the load ver sus beams strain in tension at both mid span of the beam , the load versus beam strain in compression at both mid span of the beam , and energy dissipation up to peak failure load for both spans . Also , some test result has the pressure versus soil settlement curves at span b . Furthermore the results have failure mode

PAGE 153

126 for each tested beams. Finally, these results are summarized and used to compare the performance and behavior of tested continuous RC beams according to their testing parameters . The tested beams were set up as discuss above. The specimens are grouped into three categories according to their strengthening type : unstrengthened, EB , and NSM. T he subcategories are the other parameters which are: their support conditions type which include s ( R R R ) an d (R R S). Table 4 .3 show the test matrix as discuss above. The tests also are either monotonically or cyclically loaded as four point bending until failure occurred. A ll instrumentations are used as discussed before and all data were observed and recorded by using data acquisition system. 4.2.6 Test results for unstrengthened continuous RC beams Two RC are shown in F igures 4 . 7.1 and 4.7.4 for each beam test individually. The final results also are shown in T able 4.3 . 4.2.6.1 Load carry ing capacity The load carrying capacity of unstrengthened continuous RC beams w as observed to study the behavior of RC continuous beams under rigid supports and settlement of soil, then compared with strengthened beams . M onotonic concentrated load s were a pplied on both beams. The result demonstrate s almost no effect on loading capacity of the beam that tested with ( R R R ) and beam s tested with ( R R S) as the first beam fails at 85.8 kN, while the second beam with settlement fails at 84.5 kN . The ratio of d ecreasing in compressive load capacity due to soil settlement is 1.5 % which low ratio .

PAGE 154

127 4.2.6.2 Load displacement behavior The displacement of the continuous RC beam specimen s was measured from both mid span s of the beam using a linear potentiometer. The load di splacement of unstrengthened specimen CUB 1 with ( R R R ) result s are provided i n F igure s 4 . 7 .1 (a) and (b), and the result of unstrengthened specimen CUB 4 with (R R S) are provided i n F igure s 4.7.4 (a) and (b). The results show that beams have similar loa d displacement behavior at an early stage of loading up to 20 kN in all spans of beams . At load range between 20 6 0 kN, spans of both beams show same stiffness and behaviors except span b of C UB 4 that shows low stiffness due to soil settlement. After tha t , each span behave s different ly until failure of beams. Both beams fail at (R R) span part. The deflection is varying between spans and it ' s higher at failed spans than the other span. However, CUB 4 span with soil show s higher deflection than CUB 1 un f ailed span due to soil settlement. But the opposite with failed spans where CUB 1 span b deflected more than CUB 4 span a. In summary, the soil settlement has a slight effect on failure load of unstrengthened beams while it allows spanning deflect more. 4.2.6.3 S train behavior of unstrengthened beams The strain of these beams w as measured using three PI gages that installed at one edge at both mid span s and mid support of the beam on tension zones at a distance 25 mm (1 in) from beam edge , while for compression z ones, strain gages were gluing to the three locations . For first beam CUB 1 ( R R R) , the results are presented in F igures 4 . 7 .1 ( c ) , ( d ), (e), (f), (g) and (h) for tension and compression zones. The results show that the tension strain near mid support w as higher than tension strain near both mid spans. The tension strain at failure span b is higher than tension strain at span a. for compression strain, the strain on span b and mid support have almost similar behavior. While span a has the higher compress ion strain .

PAGE 155

128 The result CUB 4 (R R S) are presented in F igures 4.7.4 ( c ) , ( d ), (e), (f), (g) and (h) for tension and compression zones . T he tension strain at mid support is higher than the tension strain at both mid spans. Both mid span tension strains be have similarly up to about 50 kN. Then the behavior change and after that tension strain at span a become higher than the one on span b. T he reason is that the soil settlement tend s to decrease tension strain of beam area near the settlement . The compressi on strain in all three locations ha s similar behaviors at early load level up to 10 kN. However, at higher load , the compression strain at span b is higher than other locations as the settlement of soil increase compression strain of area on a beam near th e settlement . In general conclusions, tension strain of beam on the mid support area is higher than mid span area. While the tension strain near failure span is higher than tension strain near the other mid span. The settlement of soil decreases tension st rain of mid span that subjected to settlement and increase the compression strain of the same location. 4.2.6.4 Energy dissipation Energy dissipation was observed in this experiment. Figure 4 . 7 . 11 show the energy dissipation bars for each specimen . For the first beam CUB 1, it ' s shown that the energy dissipation of span b (failure span) ( 1294.28 kN.mm) is higher than the energy dissipation of span a (422.78 kN.mm). For the beam CUB 4, the result obtained from test present that energy dissipation of failure span a is (881.93 kN.mm ) which is higher than the energy dissipation of span b (471.09 kN.mm ) which have a settlement energy dissipation of unstrengthened continuous RC beams with the rigid support of failure spans w as higher than those unstreng thened within soil settlement . However, the energy dissipation of non failed span under settlement w as slightly higher than the one with rigid support.

PAGE 156

129 4.2.6.5 Failure mode The failure mode is one of the parameters that been observed on this part of experimental work. The failure mode of CUB 1 beams and CUB 4 beams is provided in Figures 4.8.1 and 4.8.4. B oth beams have a similar failure mode. Table 4.4 show how each beam behave s under loading at each loading level during the test. T he unstrengthened beam C UB 1 wi th (R R R) support fail s b y having flexural cracks at mid support at 10 kN , then flexural cracks at both mid span develop at 27 kN (at span b first). S hear cracks developed on mid support at 3 8 kN. Cracks propagate and the shear cracks at mid span b at 52 kN and at span a at 73 kN. Finally, the cracks propagate and concrete crushing at 83 kN at point load of span b and beam fails at 85.8 kN due to concrete crushing at span b. S hear cracks propagate at span a at 72 kN The unstrengthened beam CUB 4 with (R R S) support has failure behavior start with flexural cracks at mid support at 10 kN at tension zone, while flexural cracks at mid span a at 29kN and at mid span b at30 kN. Shear cracks propagate at mid support at 36 kN and at mid span a at 67 kN and at m id span b at 69 kN. Concrete crushed at point load on span a at 78 kN. The beam fails at 84.5 kN by concrete crushing at span a. In summary, both unstrengthened beams show similar failure mode at an early level of loading and at ultimate loading . T he settl ement of soil has slightly impact on unstrengthened continuous beams as the beam show high stiffness to resist settlement. 4.2.7 Test results for EB continuous RC beams F igures 4 . 7.2, 4.7.3, 4.7.5, and 4.7.6 for each beam test individually. The final results also are shown in T able 4.4 too .

PAGE 157

130 4.2.7.1 Load carrying capacity The load carrying capacity of th ese EB strengthened beams were monitored during the test. The summary of the results is indicated in T able 4.3 which provid e the ultimate failure load of continuous . The ultimate failure load carrying capacity of this category is higher than ultimate failure loads of unstrengthened beams. The compressive failure load carrying capacity for CEB 2 with conditi on (R R R) support and the monotonic load was 103.6 kN. The ratio of increase in load carrying capacity with this strengthening method is 20.74 %. For continuous strengthened RC beams CEB 3 that has cyclic loading the ultimate load carrying capacity obtain ed from the experiment beam show more resistance to failure with cyclic loading than with monotonic loading for EB system. T he ratio of increase is 27.5%. CEB 5 with (R R S) condition and monotonic loading show ultimate failur e loads 117.1 kN under sand settlement conditions. The ratio of increasing is 36.48%. T he soil settlement increases the load carrying capacity. However, CEB 6 with (R R S) supports and cyclic loading conditions provide ultimate load carrying capacity 127.4 3 kN. The cyclic loading with the settlement of soil increase s the load carrying capacity of strengthened RC beams by 23%. The settlement of soil decreases the loading of EB beams with cyclic loading. In summary, the EB system improve s the load carrying c apacity of continuous beams even though with the settlement and/or under cyclic loading. T he settlement of soil increases the load carrying capacity under monotonic loading and decreases it under cyclic loading. EB beams fail with high load carrying capaci ty under cyclic loading.

PAGE 158

131 4.2.7.2 Load displacement behavior The displacement of all beams specimen w as measured from mid span in a similar way of previous ly tested beams above . The load provided on F igures 4.7.2 (a) and ( b) , 4.7.3 (a) and (b) , 4.7.5 (a) and (b) , and 4.7.6 (a) and (b) . A ccording to the data above, found that for CEB 2 the deflection at span b is slightly higher than the deflection at span b. A lthough both span s ha ve similar condition and geometry , but span a shows stiffness than span b. T he reason of that is due to human errors (inaccuracy) or the aggregate particles distribution in the concrete mix. The load deflection behavior for span b is similar than the load behavior of CUB 1 up to 60 kN when the shear cracks propagate for both beams and steel start yielding. After that EB system increase stiffness of beams by reducing the deflection of the beam to more than half and increase load carrying capacity. CEB 3 load displacement, both spans show simila r behavior on the first cycles of loading up to 80 kN, then span b becomes stiffer than span a. the beam stiffness decreases slightly after each cycle and the deflection increase. The beam shows high ultimate load capacity and deflection than CEB 2 and CUB 1. EB system shows more resistance to fails with cyclic loading. For CEB 5 which supported as (R R S) fails at span a (R R). T he span a behaves similar way as the CUB 1 and CEB 2 up to about 70 kN , w hile span b deflect more at the same loading levels as there is soil settlement. However, CEB 5 has similar behavior like CUB 4 for both spans up to 55 kN. Then CEB 5 become stiffer. EB system enhance s the behavior of continuous RC beams under a differential settlement of soil. CEB 5 has higher load failure th an CUB 1, CEB 2 , and CUB 4.

PAGE 159

132 CEB 6 load displacement behavior is examined , and the result shows that span a is stiffer than span b as span b has soil settlement which impact s its behavior. T he beam stiffness decreases slightly after each cycle as the defle ction increase. Span b deflect more than span a after failure as the soil settle more even though the failure happens at span a. H owever CEB 6 fail at higher load, mid span deflections, and soil settlement than CUB 4 and CEB 5 that have similar conditions. Also, it has higher load and deflection than CUB 1 and CEB 2. However, it shows lower load and deflection than CEB 3 under cyclic loading. clear that the EB system success to increase the load capacity of the RC beams under these differen t condition s . EB system increase s the stiffness of RC beams. The EB beams show higher resistance to so il settlement and deflect more. EB system shows high resistance to cyclic loading. 4.2.7.3 Strain behavior EB beams The strain of all beams w as measured using th ree PI gages to measure tension strain that installed at one edge at both mid span and one at mid support of the beam all at the tension zones . While three strain gages are used to measure compression strain at the same location but at compression zones. A ll instrumentations are installed at a 25 mm (1 in) from top or bottom surface of the beam. The data of the tested EB beams are presented as graphs of load strain on F igures 4.7.2 , 4.7.3 , 4.7.5 , and 4.7.6 . For CEB 2, both mid spans strain in tension and compression show similar behavior at early load level up to about 40 kN as the steel reinforcement start to yield and concrete cracks developed. Tension strain at mid support is higher than both mid spans tension strain . However, compression strain is lowe r than mid spans strain. Span b show higher tension and compression strain than span a as the failure happen in that span. Both compression strain and

PAGE 160

133 tension strain in all locations of CEB 2 are less than the strains in CUB 1. EB system reduce s the strain of continuous RC beams with (R R R) support and monotonic load conditions. For CEB 3, span a has low strain than span b in tension and compression although the failure happens at span a. Span b strain increase more than span a strain after each cycle loa ding. T he strain on mid support is higher than the strain of both spans in tension and compression zones. EB system with cyclic loading has slightly higher strain than EB system with monotonic loading , a s it subject to fatigue after re loading several tim es. CEB 5 beam has similar behavior for tension and compression strain on both mid spans up to about 25 kN. Then, tension strain of span b become lower than the tension on span a as the soil settlement impact takes place. The tension strain of mid support is higher than both mid spans at the same load level, while the compression strain is lower than both mid spans. The soil settlement reduces the EB RC beams strain at all locations as CEB 5 compared with CEB 2. EB system with sand settlement conditions a lso reduces the strain in all locations of continuous RC beams. For CEB 6 that has cyclic load and sand settlement , strain at mid support is highest here too. Tension strain at span a is higher than tension strain at span b as a result of soil settleme nt effect. While, compression strain at span b is height than at span a. EB continuous beams tension and compression strain span are lower with soil settlements as a comparison between CEB 3 and CEB 6, while the mid support strain is higher. The cyclic lo ad increases the strain of EB RC beams. In summary, EB system reduce s the strain of continuous RC beams. Strain in tension zone at mid support is higher than strain at mid spans , w hile compression strain is lower at mid -

PAGE 161

134 support. Cyclic loading increases th e strain of continuous RC beams strengthened with EB system, while soil settlement reduce s it. 4.2.7.4 CFRP strain All EB beams have strain gages on CFRP sheets, one on the middle of each sheet at both mid spans and mid support. T he purpose of that is to inv e stig ate the strain induced on the CFRP and compare the three location and with other beams. The result of strain gages reading is shown within F igures 4.7.2 , 4.7.3 , 4.7.5 , and 4.7.6 . C EB 2 results show that CFRP strain at span a is higher than CFRP strain at s pan b. CFRP strain readings near mid support location are vibrated as it ' s great er than mid spans CFRP sheets at early loading level up to 30 kN, then it become s lower than the other location up to 60 kN.After that, it become s higher than both mid spans. CEB 3 strain of CFRP on span a is the higher strain than span b and mid support CFRP sheet. W hile CFRP strain at mid support was the lowest values. CFRP strain of CEB 3 at mid spans is higher than CFRP strain of CEB 2 at the same locations, while CFRP strai n of mid support of CEB 3 is lower than CFRP strain of CEB 2 at the same location. Cyclic loading increase the strain of CFRP. For CEB 5, the strain of CFRP at mid support is higher than those on mid spans. Mid spans CFRP strain show s similar behav io r unde r loading. However, the value of CFRP strain of span a was higher at failu re load capacity than CFRP strain value at mid span b. S oil settlement tend to decreases the CFRP strain at mid spans . H owever , the CFRP strain at mid suppo r t is higher with soil set t le ment . For CEB 6 the CFRP strain at mid support is higher than other locations up to failure load. The CFRP strain at both mid spans show s similar behav io r to the last cycle of loading

PAGE 162

135 where CFRP strain of span b become higher than CFRP of span a as the beam fails at span a and the effect of soil sett le ment . The s train of CFRP at mid span b for CEB 3 is higher than CEB 6 sett le ment reduce the strain induced at CFRP at mid span. While the strain of CFRP at mid support of CEB 6 is highe r than the strain of CFRP of CEB 3. Finally cyclic loading increase CFRP strain. 4.2.7.5 Soil settlement This section deal s with CUB 4, CEB 5, and CEB 6. The reaction of support on soil was structurally calculated to be equal to (0.178 P) where P is the applied l oad on beam. The result illustrates that settlement of soil under EB system is higher than settlement under the unstrengthened beam as EB system carry a higher load. The settlement of EB system with cyclic loading also is higher than EB system under monoto nic loading as its failure load is higher. 4.2.7.6 Energy dissipation Energy dissipation was observed in this experiment and its provided in F igure 4.7.11 . CEB 2 show low energy dissipation (217.34 kN.mm) for span a and (264.86 kN.mm) at failure span b, which i s lower than energy dissipation of CUB 1. However, CEB 3 with cyclic loading and rigid supports shows higher energy dissipation (2247.32 kN.mm) at failure span a and (1163.41 kN.mm) . CEB 5 energy dissipation results are (507.42 kN.mm) at failure span a and (1736.35 kN.mm) at span b that has soil settlement which is higher than CEB 2. EB system for continuous RC beams shows higher energy dissipation with soil settlement than with rigid supports. CEB 6 energy dissipation result are (1127.47 kN.mm) at span a a nd (2100,59 kN.mm)

PAGE 163

136 at failure span b which are higher than CEB 5. Cyclic loading with soil settlement is also increase d energy dissipation of EB strengthened continuous RC beams. EB system show s lower energy dissipation with rigid support and higher energy dissipation with soil settlement than unstrengthened continuous RC beams. 4.2.7.7 Failure mode The last thing to discuss in this section is failure modes. The failure mode of EB strengthening RC continuous beams is provided for all beams through F igures 4.8.2, 4. 8.3, 4.8.5, and 4.8.6. All EB RC continuous beams have similar final failure modes as observed by concrete crushing that because the section of RC continuous beam reach es its ultimate capacity . Table 4.4 show how the beams behave under loading at each load ing level during the test. CEB 2 start to fail under loading by having flexural cracks at mid support at 21 kN loading level and span b at 22 kN then flexural cracks developed at mid span a at 34 kN. The cracks propagate and shear crack is observed near m id support at 50 kN and another one at span a at 51 kN , w hile shear cracks propagate at span b at 70 kN. CFRP sheets start to have local debonding at its mid span in all three locations after 80 kN loading. Finally, the beam fails by concrete crushing at s pan b near shear cracks at 103.6 kN. After that, concrete spoiled out. CEB 3 beam failure mode look s similar to CEB 2 with slight differences. The beam has flexural cracks at span a at 20 kN at load cycle 3, then on the same cycle flexural cracks near mid span b at 27 kN , w hile flexural cracks at mid support propagate at 30 kN. On load cycle 4, shear crack is observed at 35 kN loading near mid support. while shear cracks at span a start at 58 kN on cycle 6. Shear cracks at span b happen on cycle 7 at 65 k N. At cycle 9, CFRP sheet near mid support debond s at its mid span at 85 kN. Concrete start to crush at cycle

PAGE 164

137 10 at 100 kN loading level. Cracks propagate and beam finally fails at 132 kN by concrete crushing and spoiled out at cycle 11 which are loaded th e beam up to its failure. CEB 5 failure mode start s by flexural cracks at mid support at 23 kN and near mid span b at 34 kN. After that , shear crack was observed at 48 kN near mid support and flexural cracks near mid span a at 50 kN. Shear cracks happene d near span a at 67 Kn while it propagate s at span b at 70 kN. Then CFRP sheet near mid support has local debonding at 88 kN near its mid span. CFRP sheet has rupture d parts at 110 kN near mid support. Finally, beam fails by concrete crushing at 117 kN , a nd after that , it ' s spoiled out. CEB 6 beam also has similar failure behavior. The beam starts to have flexural cracks at 28 kN on cycle 2. Flexural cracks propagate at span b at 45 kN at cycle 4, and at mid span a at 58 kN at cycle 6. Shear cracks are ob served at cycle 6 at span b at 34 kN, at mid support at 48 kN, and at span a at 62 kN. CFRP sheet debond s at its mid span at 50 kN at cycle 7 then its start to rapture at 90 kN at cycle 10. The beam fails finally by concrete crushing near mid support at sp an b side at 127 kN at cycle 11. In summary, all beams show similar fai lure modes which w ere a failure of beam strength capacity by concrete crushing . The bonding interfacial between CFRP sheet and concrete show high strength as is start ing to debond at hi gher loading level . 4.2.8 Test results for NSM beams F igures 4.7 for each beam test individually. The final results also are shown in T able 4.3 .

PAGE 165

138 4.2.8.1 Load carrying capacity The load carrying capacity of CNSM RC beams was collected using data acquisition during the test . The summary of the results is indicated in T able 4.3 ultimate The results prove that the ultimate load capacity of CNSM s ystem is higher than the ultimate load carrying capacity of unstrengthened continuous RC beams. The ultimate compressive load carrying capacity of CNSM 7 with (R R R) support and the monotonic load was 119.6 kN. Therefore, the ratio of increasing in load c arrying capacity is 39.4%. NSM system shows higher load than EB system with these conditions. The result show s that the ration of increasing in load capacity of NSM system is 15.4% compared to EB system. For CNSM 8 under cyclic loading, the load carrying c apacity is still high, although it ' s lower than CNSM 7 with the monotonic load. The cyclic loading reduces the load carrying capacity of NSM continuous RC beams. NSM load carrying capacity is lower than EB load carrying capacity too. CNSM 9 shows lower lo ad carrying capacity than CNSM 7 due to the impact of soil soil settlement (CUB 4) as the ratio of increase is 7.45%. While CNSM 10 under cyclic loading show lower load car rying capacity than other CNSM tested beams. and cyclic loading decrease the load carrying capacity of NSM system. In summary, the NSM system provide s high load carrying capacity of continuous beams. However, settlement of soil and/or cyclic loading decrease the load carrying capacity. EB beams show better load carrying capacity behavior than NSM and the most effective reason is due to the presence of U wrap.

PAGE 166

139 4.2.8.2 Load displacement behavior The displacement of all beams specimen w as measured from mid span of beams in a similar way that done with EB system. The result of load displacement behavior for testing continuous NSM strengthening RC beams are provided through F igures 4.7.7 (a) and (b) , 4.7.8 (a) and (b) , 4.7.9 (a) and (b) , and 4.7.10 (a) and (b). Beam CNSM 7 has similar behavior for load displacement of both its spans at early load level up to 20 kN as they have similar properties and geometry. However, beam start deflects more at span b after the load increase until failure o f beam happened at span a. NSM system show s less stiffness than unstrengthened beams at early load level. But after the steel yield and concrete start to crack, NSM show higher stiffness as it has less deflection. Although CEB 2 shows stiffer behavior tha n NSM 7, the last one fails at higher load capacity and deflection. NSM 8 with cyclic loading show more stiffness under high load as it deflects less. B oth beam span shows similar behavior at lower load level and slight differences at higher load level. it shows better behavior than EB system even though the failure load is less. NSM system show s better behavior than EB system with rigid support. For continuous NSM strengthening RC beams under soil settlement conditions, CNSM 9 spans behave different ly due to soil settlement impact on span b which make it deflect more under the same loading. A lthough CNSM 9 show more deflection than CUB 4, its fails under higher load. CNSM 9 fails at lower load and higher deflection than CEB 5 with similar conditions. CNSM 10 under cyclic loading fails at lower loading, deflection, and soil settlement than CNSM 9. Although it shows higher stiffness than EB system , but it fails under low loading capacity.

PAGE 167

140 In summary, NSM system improves the load displacement behavior of cont inuous RC beams. NSM system show s better behavior at rigid support condition while EB system is better with soil settlement and/or cyclic loading. 4.2.8.3 Strain behavior of NSM beams The strain behavior was measured in a similar way of EB system. The data of th e tested NSM beams are presented as graphs of load strain within F igures 4.7.7 , 4.7.8 , 4.7.9 , and 4.7.10 . For CNSM 7, the highest tensile strain was at mid support, while the lowest compressive strain was i n the same location. The tensile strain on span a is higher than on span b as the failure also happens at span a. while compression strain at span a is lower than span b. CNSM system for continuous RC beams tend s to decrease the tensile and compression strain of beam in all three locations that measured . CNSM at this conditions ha s similar compression and tensile strain behavior as CEB system with slight differences that are more obvious on tension zone but still small. CNSM 8 have a similar strain on all locations at early loading level , and that start to varies as the load increase. Mid support has the highest tensile strain at failure load while mid span b has the highest compression strain than others at failure load as the beam fail at span b with concrete crushing. Although EB system and NSM system almost have similar strain behavior in all locations, EB system shows higher strain than CNSM system. Also , obvious that strain with cyclic load is higher than with monotonic load. CNSM system is tested under soil settlement condition ; CNSM 9 strain behave s differently at all locations due to soil settlement impact. However, strain at span a was the highest as the failure happens there. Soil settlement decreases the strain at span b. In general, NSM system reduce s the strain for continuous RC beams. N SM system shows lower strain behavior than EB system under soil settlement for continuous RC beams. CNSM 10 under

PAGE 168

141 cyclic loading shows higher strain at its mid support than other locations. NSM system with cyclic loading and soil settlement show lower stra in behavior than EB system for continuous RC beam. In summary, NSM system reduce s the strain of continuous RC beams. Strain in tension zone at mid support is higher than strain at mid spans. Cyclic loading increases the strain of continuous RC beams streng thened with both NSM and EB system, while soil settlement reduce s it. 4.2.8.4 CFRP strips strain behavior All CNSM beams have strain gages on there CFRP strips, one on the middle side of each strip at both mid spans and the mid support location. The result of st rain gages reading is presented within F igures 4.7.7 , 4.7.8 , 4.7.9 , and 4.7.10 . CNSM 7 beam result shows that at early load level CFRP strain at mid support is higher than other locations up to 80 kN where the concrete crushed and steel yield. After that t he strain of CFRP at mid span a become higher until failure of the beam at span a. CNSM 7 CFRP strain show s better strain behavior than CEB 2 CFRP strain which means strain in CFRP strip is less than strain induced in CFRP sheet. CNSM 8 CFRP strain data pr esent that strain of CFRP strip is similar to first load level and cycles, after that the CFRP strain at mid span b is higher than other locations. The strain start increases as the cycle number increase d . As mentioned before, cyclic loading increases the strain of CFRP. CFRP strip strain of CNSM 9 under soil settlement on span b effect shows that all location has similar CFRP strain behavior at low loading level up to 10 kN. After that, the strain of CFRP at middle support become higher than others. The s t rain of CFRP at span b is less than the one at span a as the soil settlement effect take place. CNSM 7 mid support shows

PAGE 169

142 strain behavior better than CNSM 9 as it has low strains values. While soil settlement on span b make s a strain of CNSM 9 CFRP lower t han the strain of CFRP of CNSM 7. With soil settlement conditions, NSM system also show s better strain behavior than EB system. CNSM 10 under cyclic loading mid support CFRP strip strain is higher than other locations, while the strain of CFRP at span b is the lowest due to soil settlement effect. CFRP strip strain under cyclic loading and soil settlement shows better behavior than CFRP sheet. 4.2.8.5 Soil settlement The soil settlement under NSM strengthening continuous RC beams behavior are shown within same fig ures for CNSM RC beams. Even though the water ratio in sandy soil was controlled and the density of the sandy soil also controlled, the soil still has different behavior for each test. Soil under CEB beams is stiffer than soil under CNSM RC beams while the soil under the unstrengthened continuous RC beam has behavior that falls between both previous soil s . Soil subgrade reaction modulus under cyclic loading for CNSM system is lower than soil under monotonic loading, while opposite behavior happened with soi l under EB beam system. 4.2.8.6 Energy dissipation Energy dissipation was calculated and its shown in F igure 4.7.11 . I ts observed that energy dissipation with cyclic loading is less than energy dissipation with monotonic loading under both condition s of rigid su pport and with the sand settlement. CNSM 7 show s moderate energy dissipation compared to other tested beams as its v alues were (750.4 kN.mm) for failed span a and (840.2 kN.mm) for span b. W hich are higher than energy dissipation of CEB 2. CNSM 8 shows low er values of energy dissipation (233.08 kN.mm) for span a and (417.2

PAGE 170

143 kN.mm) for span b where the failure happened. These result s show that the energy dissipation behavior of NSM beam with rigid support are opposite to that of EB system under loading type conditions. The result of CNSM 9 is (171.2 kN.mm) for span a where the failure happened and (868.95 kN.mm) for span b. T hat mean for continuous NSM RC beams energy dissipation is higher with soil settlement, and it ' s lower than EB system. For CNSM 10 the e nergy dissipation for span a is (80.64 kN.mm) and for span b is (466.2 kN.mm) . T hese are less than values of CEB energy dissipation than EB system for continuous beams. 4.2.8.7 F ailure mode The failure is observed , and it provided in Figures 4.8.7 , 4.8.8 , 4.8.9 and 4.8.10 for each case, Most NSM beams have a similar failure mode. Table 4.4 show s how these beams behave under loading at each loading level up to its failure load cap acity. For CNSM 7 the failure mode starts with flexural cracks at mid support at 24 kN, span a at 26 kN, and span b at38 kN. After that, shear cracks propagate at mid support at 45 kN, at span a at 55 kN, and at span b at 65 kN. Then cracks propagate until concrete crush ing happened at span a at 119.6 kN around shear cracks and NSM strip. Then it ' s spilled out. CNSM 8 has flexural cracks at cycle loading 3 at mid support at 25 kN and at both mid spans a and b at 35 kN. Shear cracks appear at mid support a t cycle 5 at 56 kN, while it propagates at span b at cycle 8 at 58 kN. Shear crack propagate at span a at cycle 10 at 88 kN. The fails by concrete crushing at span a near NSM and shear cracks at 109 kN and cycle 11. For CNSM 9 the failure mode starts with a shear crack at mid support at 25 kN, then shear cracks at mid span a and span b at 30 kN. However, the shear crack propagates near mid -

PAGE 171

144 support at 32 kN and at span a at 48 kN while it appear s on span b at 78 kN as the soil settle more and beam deflection become more obvious. Althou gh the deflection is more at span b, the failure happened at span a at 90.8 kN by CFRP debonding and concrete crushing. For the last beam CNSM 10 failure mode starts with a flexural crack at mid support at 20 kN during cycle 3. Another flexural crack appears near mid span a at 24 kN on the same cycle . While flexural crack near mid span b happened late at load 34 kN and cycle 5. At cycle 7, the shear crack prop a gate s at span b at 63 kN, while shear cra c ks at span a and mid suppo rt propagate at cycle 8 within load 36 kN. Finally, CFRP strip with concrete surrounding it debond at span a then concrete crushing at 87.2 kN and during cycle 10. Finally, all beams show similar failure mode at an early level of loading. T he most failure modes with NSM system was also a failure of beam strength capacity by concrete crushing Preceded by CFRP debonding for two of them . The bonding interfacial between CFRP strips and concrete show high strength . For failure mode comparison between EB and NSM , both of them show similar trend by fails either by CFRP and concrete cover debonding or by the capacity strength of RC beams sections.

PAGE 172

145 Specimen Compressive Load at 7 days (kN) Compressive Stress at 7 days ( MPa ) CC1 167.96 21.39 C C2 138.6 17.66 CC3 135.13 17.21 Average compressive stress 18.75 Specimen Compressive Load (kN) Compressive Stress (M P a) CC4 308.79 39.33 CC5 235.8 30.04 CC6 201.771 25.7 Average compressive stress 31.69 Table 4.1. Compressive strength of concrete cylinder at 7 days Table 4.2. Compressive strength of concrete cylinder at 10 days

PAGE 173

146 Beam No. Beam condition Support type Fa ilure load (kN) Def. at failure span a (kN) Def. at failure span b (mm) Soil settlement (mm) Span failed CUB 1 U* R R R 85.8 6.5 17.5 X b (R S) CEB 2 S R R R 103.6 3.2 4.2 X b (R S) CEB 3 Cyclic S R R R 132.1 25.6 16.2 X a (R R) CUB 4 U R R S 84.5 12 .2 8.7 10.9 a (R R) CEB 5 S R R S 117.1 6.5 20 31.4 a (R R) CEB 6 Cyclic S R R S 127.43 12.3 46 55 b (R S) CNSM 7 S R R R 119.6 10 11.6 X a (R R) CNSM 8 Cyclic S R R R 109.2 4.75 5.9 X a (R R) CNSM 9 S R R S 90.8 4.6 14.7 26 a (R R) CNSM 10 Cyclic S R R S 87.2 1.5 9 13.5 a (R R) * U means unstrengthened RC beams an d S means strengthened RC beams Table 4.3. Test results of continuous beams

PAGE 174

147 Beams NO. Load level (kN) 0 20 2 0 40 40 60 60 80 80 100 > 100 C UB 1 FC at 10 kN FC at span a and b at 27 kN while SC at mid support at 38 kN FC a 40 kN, and SC b 52 kN, while CC at point load Cracks propegate Beam fails CC b 85.8 kN ---CEB 2 ---FC b 22 kN, FC mid supp 21 kN, FC a 34 kN SC mid sup 50 kN, SC a 51kN SC b 70 kN Local debond CFRP 0 kN all Fails CC b 103.6 kN CEB 3 FC a 20 kN C3, FC b 27 kN C3. FC mid sup 30kN C4 SC mid sup 35 kN C 4, SC a 58 kN C6 SC b 65kN C7 CFRP debond mid sup 85 C10, CC a 100 kN C10 Cracks propagate Fails CC a 132 kN CUB 4 FC mid sup 10 kN FC a 29 kN, FC b 30 kN, SC mid sup 36 kN SC a 67 kN, SC b 6 9kN CC a 78 kN Beam fails CC a 84.5 ---CEB 5 ---FC mid sup 23 kN, FC b 34kN FC a 50 kN, SC mid sup 48 kN SC a 67 kN, SC b 70kN CFRP debond mid sup 88kN CFRP rapture 110 kN, fails CC 117 kN CEB 6 ---FC mid sup 22kN C2 FC b 45kN C4, FC a 58kN C6 SC b 34kN C6, SC mid sup 48kN C6, SC a 62 kN C6 CFRP debond mid sup 50kN C7 CFRP rapture mid sup 90kN C10, fails mid sup CC 127kN C11 CNSM 7 ---FC mid sup 24kN, FC a 26kN, FC b 38kN SC mid sup 45kN, SC a 55kN SC b 65kN Cracks propagate Fails CC a 119.6k N CNSM 8 ---FC a&b 30kN C3, FC mid sup 35kN C3 SC mid sup 56kN C5, SC b 58kN C8 Cracks propagate SC a 88kN C10 Fails CC b 109 kN C11 CNSM 9 ---FC mid sup 25kN, FC a&b 30kN, SC mid sup 32kN SC a 48kN SC b 78kN CFRP debond & CC a 90.8 ---CNSM 1 0 FC mid sup 20kN C3 FC 24kN C3, FC b 34kN C5 Cracks propagate SC b 63kN C7, SC a 36 kN C8, SC mid sup 37kN C8 CFRP debond & CC a 87.2kN C10 ---Notation FC: Flexural cracks. SC: Shear cracks. CC: Concrete crush. mid sup: mid support. a : span a. b: span b. C2: cycle 2 Table 4.4 . Failure modes of continuous RC beams

PAGE 175

148 Figure 4 . 1 . Specimen dimensions and details (mm) : (a) cross section near mid span; (b) cross section near hinge support; (c ) beam dimension and reinforcement detail; (d) beam with groove dimension and reinforcement. (a) ( b ) ( c ) ( d )

PAGE 176

149 Figure 4.2. Concrete test for compressive stre ngth: (a) c ylinder ready for test ; (b) failed cylinders (a) ( b )

PAGE 177

150 (a) ( b ) ( c ) Figure 4.3. Beam preparation : (a) s tirrups f abrication ; (b) bending main steel bar; (c) w ood f orm

PAGE 178

151 ( d ) ( e ) ( f ) ( g ) Figure 4.3. Beam preparation (continued): (d) steel cages; ( e) casting b eams ; (f) curing beams; ( g) g luing C FRP sheets

PAGE 179

152 Figure 4.4. T est set up for ( R R R ) support : (a) unstrengthened beam; ( b ) EB continuous RC b eams ( a ) ( b )

PAGE 180

153 ( c ) Figure 4.4. T est set up for ( R R R ) support : (c) NSM continuous RC b eams Figure 4.5. T est set up for unstrengthening RC beam with ( R R S ) support

PAGE 181

154 Figure 4.6. 1. Test details and instrumentation for CUB 1: (a) test setup; (b) linear potentiometer; (c) PI gages and strain gages ( a ) ( b ) ( c )

PAGE 182

155 Span a Span b Figure 4.6.2. Test details and instrumentation for beam CU B 4: (a) test setup; (b) linear potentiometer to measur e settlement of submerged soil with 25% of water ratio; (c) PI gages and strain gages ( a ) ( b ) ( c )

PAGE 183

156 0 20 40 60 80 100 120 0 5 10 15 20 25 30 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0 5 10 15 20 25 30 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain ( a ) ( b ) ( c ) ( d ) Figure 4.7.1. Test result of CUB 1: (a) load displacement at span a; (b) load displacement at span b; (c) PI gage strain in tension at span a; (d) PI gage strain in tension at span b

PAGE 184

157 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain Figure 4.7.1. Test result of CUB 1(continued): (e) strain gage readings of concrete in compression at span a; (f) strain gage readings of concrete in compression at spa n b; (g) PI gage strain in tension at mid support; (h) strain gage readings of concrete in compression at mid support ( e ) ( f ) ( g ) ( h )

PAGE 185

158 0 20 40 60 80 100 120 0 2 4 6 8 10 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0 2 4 6 8 10 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain Figure 4.7.2. Test result for CEB 2 : (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b ( a ) ( b ) ( c ) ( d ) ( e ) ( f )

PAGE 186

159 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 0.0080 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 0.0080 Load (kN) FRP strain 0 20 40 60 80 100 120 -0.0004 -0.0003 -0.0002 -0.0001 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 Load (kN) FRP strain Figu re 4.7.2. Test result for CEB 2 (continued): (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in compression at mi d support;(k) strain gages reading of FRP in tension at mid support ( g ) ( h ) ( i ) ( j ) ( k )

PAGE 187

160 0 20 40 60 80 100 120 140 0 10 20 30 40 50 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 140 0 10 20 30 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) Beam strain 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain Figure 4.7.3. Test result of CEB 3: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b ( f ) ( e ) ( c ) ( d ) ( a ) ( b )

PAGE 188

161 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0004 -0.0003 -0.0002 -0.0001 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 140 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0 1000 2000 Load (kN) Time (sec.) Figure 4.7.3. Test result of CEB 3 (continued): (a) load displacement at span a; (g) strain g ages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in compression at mid support;(k) strain gages reading of FRP in tension at m id support ;(l) loading scheme ( g ) ( h ) ( i ) ( j ) ( k ) ( l )

PAGE 189

162 0 20 40 60 80 100 120 0 5 10 15 20 25 30 Load (kN) Displacement (mm) Span a 0 20 40 60 80 100 120 0 5 10 15 20 25 30 Load (kN) Displacement (mm) Span b 0 20 40 60 80 100 120 -0.0010 0.0010 0.0030 0.0050 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0001 0.0019 0.0039 0.0059 Load (kN) Beam strain ( a ) ( b ) ( c ) ( d ) 0 20 40 60 80 100 120 -0.0040 -0.0020 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain ( e ) ( f ) Figure 4.7.4. Test result for CUB 4: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b

PAGE 190

163 0 20 40 60 80 100 120 0.0000 0.0030 0.0060 0.0090 0.0120 0.0150 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0030 -0.0020 -0.0010 0.0000 0.0010 Load (kN) Beam strain ( g ) ( h ) ( i ) Figure 4.7.4. Test result for CUB 4(continued): (g) pressure settlement at span b; (h) PI gages strain in tension at mid support; (i) strain gages reading of concrete in compression at mid support 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 Pressure (kPa) Sand settlement (mm)

PAGE 191

164 0 20 40 60 80 100 120 0 4 8 12 16 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0 4 8 12 16 20 24 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain Figure 4.7.5. Test result for CE B 5: (a) load displacement at span a; (b) load di splacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b ( a ) ( b ) ( c ) ( d ) ( e ) ( f )

PAGE 192

165 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0012 -0.0009 -0.0006 -0.0003 0.0000 0.0003 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) FRP strain ( g ) ( h ) ( i ) ( j ) ( k ) ( l ) Figure 4.7.5. Test result for CE B 5 (continued): (g) strain gages reading of FRP at span a; (h) strain gages reading of FRP at span at span b; (i) pressure settlement at span b; (j) PI gages strain in tension at mid support; (k) strain ga ges reading of concrete in compression at mid support; (l) strain gages reading of FRP at mid span 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 Pressure (kPa) Sand settlement (mm)

PAGE 193

166 0 20 40 60 80 100 120 140 0 3 6 9 12 15 Load (kN) Displacement(mm) 0 20 40 60 80 100 120 140 0 10 20 30 40 50 60 70 Load (kN) Displacement(mm) 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0020 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0010 -0.0007 -0.0004 -0.0001 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain ( a ) ( b ) ( c ) ( d ) ( e ) ( f ) Figure 4.7.6. Test result for CEB 6: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) P I gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b

PAGE 194

167 0 20 40 60 80 100 120 140 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0.0000 0.0020 0.0040 0.0060 0.0080 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) Beam strain ( g ) ( h ) ( i ) ( j ) Figure 4.7.6. Test result for CEB 6 (continu ed): (g) strain gages reading of FRP at span a; (h) strain gages reading of FRP at span at span b; (i) pressure settlement at span b; (j) PI gages strain in tension at mid support 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 Pressure (kPa) Soil settlement (mm)

PAGE 195

168 0 20 40 60 80 100 120 140 -0.0020 -0.0015 -0.0010 -0.0005 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 140 0.0000 0.0030 0.0060 0.0090 0.0120 0.0150 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0 500 1000 1500 2000 2500 Load (kN) Time (sec.) ( k ) (l ) ( m ) Figure 4.7.6. Test result for CEB 6 (continued): (k) strain ga ges reading of concrete in compression at mid support;(l) strain gages reading of FRP at mid span; (m) loading scheme

PAGE 196

169 0 20 40 60 80 100 120 0 4 8 12 16 20 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0 4 8 12 16 20 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain (a ) (b ) (c ) (d ) (e ) (f ) Figure 4.7.7. Test result for CNSM 7: (a) load displacement at span a; (b) load displacement at span b; (c) PI gag es strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b

PAGE 197

170 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 0.0080 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0004 -0.0003 -0.0002 -0.0001 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain (g ) (h ) (i ) (j ) (k ) Figure 4.7.7. Te st result for CNSM 7 (continued): (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in compression at mid support;( k) strain gages reading of FRP in tension at mid support

PAGE 198

171 0 20 40 60 80 100 120 140 0 5 10 15 20 25 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) Beam strain 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0009 -0.0006 -0.0003 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 140 -0.0040 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 140 0 3 6 9 12 15 Load (kN) Displacement (mm) (a ) (b ) (c ) (d ) (e ) (f ) Figure 4.7.8. Test result of CNSM 8: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) Strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b

PAGE 199

172 0 20 40 60 80 100 120 140 0.0000 0.0010 0.0020 0.0030 Load (kN) FRP strain 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0050 0.0100 0.0150 0.0200 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0006 -0.0004 -0.0002 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 140 0.0000 0.0050 0.0100 Load (kN) FRP strain Figure 4.7.8. Test result of CNSM 8 (continued): (g) strain gages reading of FRP in tension at span a; (h) strain gages reading of FRP in tension at span b; (i) PI gages strain in tension at mid support;(j) strain gages reading of concrete in compression at mid support;(k) strain gage s reading of FRP in tension at mid support ;(l) loading scheme (g ) (h ) (i ) (j ) (k ) (l ) 0 20 40 60 80 100 120 140 0 500 1000 1500 2000 2500 3000 3500 Load (kN) Time (sec.)

PAGE 200

173 0 20 40 60 80 100 120 0 4 8 12 16 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0 5 10 15 20 25 30 35 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0.0000 0.0010 0.0020 0.0030 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0030 -0.0020 -0.0010 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (d ) (c ) (e ) (f ) (a ) (b ) Figure 4.7.9. Test result for CNSM 9: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages str ain in tension at span b; (e) strain gages reading of concrete in compression at span a; (f) strain gages reading of concrete in compression at span b

PAGE 201

174 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0012 -0.0009 -0.0006 -0.0003 0.0000 0.0003 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0030 0.0060 0.0090 0.0120 Load (kN) FRP strain (g ) (h ) (i ) (j ) (k ) (l ) Figure 4.7.9. Test result for CNSM 9 (continued): (g) strain gages reading of FR P at span a; (h) strain gages reading of FRP at span at span b; (i) pressure settlement at span b; (j) PI gages strain in tension at mid support; (k) strain gages reading of concrete in compression at mid support;(l) strain gages reading of FRP at mid span 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 Pressure (kPa) Soil settelment (mm)

PAGE 202

175 0 20 40 60 80 100 120 0 2 4 6 8 10 Load (kN) Displacement(mm) 0 20 40 60 80 100 120 0 2 4 6 8 10 12 Load (kN) Displacement (mm) 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0005 0.0010 0.0015 0.0020 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0010 -0.0005 0.0000 Load (kN) Beam strain 0 20 40 60 80 100 120 -0.0010 -0.0005 0.0000 Load (kN) Beam strain (a ) (b ) (c ) (d ) (e ) (f ) Figure 4.7.10. Test result of CNSM 10: (a) load displacement at span a; (b) load displacement at span b; (c) PI gages strain in tension at span a; (d) PI gages strain in tension at span b; (e) strain gages reading of co ncrete in compression at span a; (f) strain gages reading of concrete in compression at span b

PAGE 203

176 0 20 40 60 80 100 120 0.0000 0.0010 0.0020 0.0030 0.0040 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 0.0080 Load (kN) FRP strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 0.0060 Load (kN) FRP strain (g ) (h ) (i ) (j ) Figure 4.7.10. Test result of CNSM 10 (continued): (g) strain gages reading of FRP in tension at span a; (h) strain gag es reading of FRP in tension at span b; (i) pressure settlement at span b;(j) PI gages strain in tension at mid support 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 Pressure (kPa) Settelment (mm)

PAGE 204

177 0 20 40 60 80 100 120 -0.0005 -0.0003 -0.0001 Load (kN) Beam strain 0 20 40 60 80 100 120 0.0000 0.0020 0.0040 Load (kN) FRP strain 0 20 40 60 80 100 120 0 150 300 450 600 750 Load (kN) Time (sec.) (k ) (l ) (m ) Figure 4.7.10. Test result of CNSM 10 (continued): (k) strain gages reading of concrete in compres sion at mid support;(l) strain gages reading of FRP in tension at mid support; (m) loading scheme

PAGE 205

178 0 500 1000 1500 Energy ( kN. mm) CUB-1 a CUB-1 b 0 100 200 300 Energy ( kN. mm) CEB-2 a CEB-2 b 0 1000 2000 3000 Energy ( kN. mm) CEB-3 a CEB-3 b 0 300 600 900 Energy ( kN. mm) CUB-4 a CUB-4 b 0 500 1000 1500 2000 Energy ( kN. mm) CEB-5 a CEB-5 b 0 1000 2000 3000 Energy ( kN. mm) CEB-6 a CEB-6 b Figure 4.7.11. Energy dissipations for continuous beams: (a) energy dissipation for CUB 1 ; (b) energy dissipation for CEB 2 ; (c) energy dissipatio n for CEB 3; (d) energy dissipation for CUB 4; (e) energy dissipation for CEB 5; (f) energy dissipation for CEB 6 (a ) (b ) (c ) (d ) (e ) (f )

PAGE 206

179 0 300 600 900 Energy ( kN. mm) CNSM-7 a CNSM-7 b 0 200 400 600 Energy ( kN. mm) CNSM-8 a CNSM-8 b 0 300 600 900 Energy ( kN. mm) CNSM-9 a CNSM-9 b 0 200 400 600 Energy ( kN. mm) CNSM-10 a CNSM-10 b Figure 4.7.11. Energy dissipations for continuous beams (continued) : ( g ) energy dissipation for CNSM 7 ; ( h ) energy dissipation for CNSM 8 ; ( i ) energy dissipation for CNSM 9; ( j ) energy dissipation for CNSM 10 (g ) (h ) (i ) (j )

PAGE 207

180 Figure 4.8.1 Failure mode of CUB 1: (a) flexural crack at mid support at 10 kN loading; (b) flexural cracks at mid span a at 10 kN; (c) shear cracks at 38 kN; (d) shear cracks develop after 52 kN ( a ) ( b ) ( c ) ( d )

PAGE 208

181 Figure 4.8.1. Failure mode of CUB 1(continued): (e) flexural shear cracks at 78 kN; (f) concrete crush at point load at 52kN; (g) cracks develop; (h) beam failed by concrete crushing at point load on span b at 85.787 kN. ( e ) ( f ) ( g ) ( h )

PAGE 209

182 Figure 4.8.2. Failure mode of CEB 2 : (a) flexural cracks at mid span b at 20kN; (b) flexural crack at mid support at 20 kN ; (c) concrete crush at point load on span b at 37 kN; (d) shear cracks at 50 kN; (e) shear cracks develop at 70 kN on span b; (f) local de bonding of CFRP sheet at middle of both span and mid support at 80 kN ( f ) ( e ) ( a ) ( b ) ( c ) ( d )

PAGE 210

183 ( g ) ( h ) ( i ) Figure 4.8.2. Failure mode of CEB 2 (c ontinued): (g) & (h) cracking and concrete crushing near shear cracks on span b at103.6 kN; (i) beam after failure.

PAGE 211

184 Figure 4.8.3. Failure mode of CE B 3: (a) flexural crack at mid span a at 20 kN and cycle 2; (b) flexural cracks span b at 27 kN and cycle 2; (c) flexural cracks mid support at 30 kN and cycle 2; (d) beam deflection at span a. ( a ) ( b ) ( c ) ( d )

PAGE 212

185 ( e ) ( f ) ( g ) ( h ) Figure 4.8.3. Failure mode of CE B 3 (continued): (e) beam deflection at span b; (f) sh ear cracks at 35 kN near mid support at span a at cycle 3; (g) FRP deboned at span a at 85 kN; (h) concrete crush at point load on span a at 117 kN at cycle 11; (i) beam after its fail by concrete crushing on span a. ( i )

PAGE 213

186 ( a ) ( b ) ( c ) ( d ) ( e ) ( f ) Figure 4.8.4. Failure mo de of CU B 4: (a) flexural crack at mid support at 10 kN; (b) flexural cracks at both mid span (span a) at 10 30 kN; (c) shear cracks at 30kN near mid support; (d) shear cracks develop at middle of both span (span a) at 50 kN; (e) deflection increase at spa n a; (f) soil settlement.

PAGE 214

187 Figure 4.8.4. Failure mode of CU B 4 (continued): (g) concrete crush at point load on span a at 78 kN; (h) beam hogging at mid support and cracks developed; (i) concrete crushing under point load on span a at 84.5kN. ( g ) ( h ) ( i )

PAGE 215

188 ( a ) ( b ) ( c ) ( d ) ( e ) ( f ) Figure 4.8.5. Failure mode of CE B 5: (a) flexural crack at mid support at 20 kN; (b) flexural cracks (span b) at both mid span at 30 kN; (c) shear cracks at 40 kN near mid support; (d) shear cracks (span b) develop at middle of both span after 70 kN; (e) soil settlement; (f) shear cracks developed and FRP debonding at span b.

PAGE 216

189 ( g ) ( h ) ( i ) ( j ) ( k ) ( l ) Figure 4.8.4. Failure mode of CE B 5 (continued): (g) CFRP parts deboned at middle support on span b; (h) beam hogging at middle support; (i) concrete crush at point load on span a at 117 kN ;(j) failure location at span a from other side view; (k) concrete spoil out at span a; (l) c oncrete crushing on span a

PAGE 217

190 Figure 4.8.6. Failure mode of CEB 6: (a) flexural crack at mid support at 25 kN and cycle 2; (b) flexural cracks (span b) at both mid span at 40 kN and cycle 4; (c) shear cracks at 55 kN and cycle 5 at mid span near soil on span b; (d) concrete crush near point load at span a at 70 kN and cycle 6; (e) shear cracks developed and FRP debonding at mid span at cycle 7; (f) FRP parts debonded at mid support and shear cracks developed at cycl e 8 ( a ) ( b ) ( c ) ( d ) ( e ) ( f )

PAGE 218

191 (g ) (h ) (i ) (j ) Figure 4.8.6. Failure mode of CEB 6 (continued): (g) shear cracks develop at mid span b; (h) FRP sheet at mid support damaged; (i) concrete crushing near mid support and hogging of beam on middle support at load 127 kN cycle 11 ; (j) beam after its fail by concrete crushing.

PAGE 219

192 (a ) (b ) (c ) (d ) Figure 4.8.7. Failure mode of CNSM 7: (a) flexural crack at mid support at 24 kN; (b) and (c) flexural cracks at both mid span (span a and span b) at 25 kN; (d) cracks transfer to other side of beam at mid support.

PAGE 220

193 (e ) (f ) (g ) (h ) Figure 4.8.7. Failure mode of CNSM 7 (continued): (e) shear cracks at 35 kN at mid span and both mid span; (f) concrete crush at mid span a at 119 kN near NSM CFRP strip; (g) C FRP strip after concrete surrounding it are crushed; (h) beam after its fail by concrete crushing.

PAGE 221

194 (a ) (b ) (c ) (d ) (e ) (f ) Figure 4.8.8. Failure mode of CNSM 8: (a) flexural crack at mid support at 30 kN span a and cycle 3; (b) flexural cracks at span b at 30 kN and cycle 3; (c) flexural cracks at mid support at 35 kN cycle 3; (d) shear cracks at 55 kN and cycle 5 at mid support; (e) shear cracks at span b at 58 kN cycle 8; (f) shear cracks at span a at 88 kN cycle 10.

PAGE 222

195 (g ) (h ) (i ) (j ) Figure 4.8.8. Failure mode of CNSM 8(continued):(g) cracks develop at span a; (h) cracks develop at span b; (i) beam fails due to concrete crushing after shear cracks reach NSM CFRP strip at mid span b at 109 kN. (j) another vie w of failure.

PAGE 223

196 Figure 4.8.9. Failure mode of CNSM 9: (a) flexural crack at span b at 30 kN; (b) flexural cracks at span a at 30 kN and at mid support at 25 kN; (c) shear cracks at 32 kN near mid support; (d) shear cracks (spa n a) develop at middle of both span of at 48 kN. (a ) (b ) (c ) (d )

PAGE 224

197 (e ) (f ) (g ) Figure 4.8.9. Failure mode of CNSM 9(continuoued): (e) cracks develop (span b); (f) beam fails due to shear cracks that propagate and top CFRP debonding at span a at 90.8 kN; (g) beam after its fail by concrete crushing and CFRP debonding on span a.

PAGE 225

198 (a ) (b ) (c ) (d ) (e ) (f ) Figure 4.8.10. Failure mode of CNSM 10: (a) flexural crack at mid support at 0 kN and cycle 3; (b) flexural cracks at span a at 24 kN and cycle 3; (c) flexural cracks at span b at 34 kN cycle 5; (d) shear cracks at span b at 63 kN cycle 7; (e) shear cracks at 37 kN and cycle 8 at mid support; (f) shear cracks at span a at 36 kN cycle 8; (g) shear cracks racks develop at span a and top CFRP strip debond with concrete cover at 87 kN at cycle 10.

PAGE 226

199 Figure 4.8.10. Failure mode of CNSM 10 (continued): (h) CFRP debonding at span a at bottom surfaced of beam; (i) beam after it fails due to concrete crushing after shear cracks reac h NSM CFRP strip. (g ) (h ) (i )

PAGE 227

200 CHAPTER V SUMMARY AND CONCLUSIONS T his thesis report s an experimental program to investigate the behavior of externally bonded (EB) and near surface mounted (NSM) strengthening system s with CFRP sheets and strips for reinforcement concrete members under differential settlement . Strengthening is and emerging solution to gain back the capacity and performance of that element. S trengthening o f CFRP system is a proven technique for the rehab ilitation of many structures like bridges, parking structures , and buildings . CFRP is used in preference because of it is durable , high tensile strength, and high elastic modulus with low weight. T he follow ings conclusion are drawn : Limited research studies have been conducted in the area of studying the behavior of CFRP structures under differential settlement. R esearch investigate s the capacity of strengthen ed concrete beam s with CFRP and the ir behavior un der concentrated load, cyclic load, and fatigue . FRP is a promising material as it has many advantages like low weight, easy to install, high tensile strength and durability, high resistance to corrosion . CFRP reduce s the cost of rehabilitation and help s designer s enhance the performance of constructed members in an affordable manner. As the EB system w as used earlier than the NSM system, NSM has been less research ed than EB. However, as the NSM system proves its high efficiency in some applications, mor e sea rch has been conducted with NSM system s recently. NSM system s for concrete members show better strength and performance than EB system s in many cases .

PAGE 228

201 In chapter three, the performance of EB and NSM system for reinforcement concrete beams under a set tlement of soil were tested with two phase s experimental program that conducted to examine the performance of RC beams strengthening with CFRP sheet and strips . T he test result s show the conclusion below: For EB system: Beams strengthening with EB system s how higher load capacity than the unstrengthen RC beams. Settlement of soil beneath the beam increase its load failure capacity and increase its deflection. The presence of water in soil reduce the modulus of subgrade reaction (stiffness) of that soil and allow the RC beams to deflect more and fails with higher load capacity. The EB system increase s the carrying load capacity and reduce s the beam deflection in case of rigid support, while the deflection and stiffness of EB RC beam increase in case of soil s ettlement increase. RC beams with rigid support show higher strain than RC beams with the settlement . EB system in RC beams reduce s the tensile and compression strain of the element. CFRP strain in tension zones show s higher value near mid span. These val ue s decrease as the distance from the mid span increase. The strain of CFRP near rigid hinge side is higher than the strain of CFRP near fixed support.

PAGE 229

202 Settlement of soil tend to reduce the CFRP sheet strain, and that can be shown clearly in the case of (F WS) support on which, the strain of CFRP sheet was higher near hinge support that set on soil submerged in water than the strain near fixed support. EB system proves the behavior of RC beam under a settlement of soil . The energy dissipation of unstrengthe n RC beams is higher that EB RC beams with rigid support conditions. Soil settlement decrease s the energy dissipation of unstrengthening RC beams. However, its increase the energy dissipation of strengthening RC beams as it fails at higher load. Failure mo des show different behaviors for EB system and RC beams according to test parameters. All beams failure modes were similar at early load level. The failure mode of unstrengthened RC beams with different support conditions was the same by propagat ing of she ar cracks then concrete crush. Most EB RC beams failed due to CFRP debonding with or without concrete cover and concrete crush. For NSM system: Beams strengthening with NSM system show higher load capacity than the unstrengthen RC beams. The NSM system inc rease s the carrying load capacity and reduce s the beam deflection in case of rigid support and in the case of submerged soil , while the deflection and stiffness of NSM RC beam increase in case of dry soil settlement. NSM show higher resistance when support is rigid.

PAGE 230

203 Settlement of soil tend s to increase the tensile strain of RC beams. NSM system in RC beams reduce the tensile strain of RC beams and increase the compression strain of the element. CFRP strip strain in tension zones show s higher value near mid span. These value s decrease as the distance from the mid span increase. The strain of CFRP strip near rigid hinge side is higher than the strain of CFRP near fixed support. NSM system proves the behavior of RC beam under a settlement of soil. The energy d issipation of unstrengthen RC beams is higher that NSM RC beams with rigid support conditions. Dry s oil settlement decreases the energy dissipation of unstrengthening RC beams. However, its increase the energy dissipation of strengthening RC beams as it fa ils at higher load. The s ubmerged soil has different behave with energy dissipation than dry soil as it increases energy dissipation for un strengthening RC beams and decrease s it for NSM system. Failure modes show two behaviors for NSM system CFRP strip wi th concrete cover debonding and failure due to section strength capacity. Both system s improve the flexural behavior of RC beams. Compressive load capacity of RC beams under a settlement of soil is higher with EB system than NSM system. While with rigid su pport NSM shows better behavior. NSM system is stiffer than EB system as it shows low deflection and higher load carrying capacity.

PAGE 231

204 NSM system has lower tensile strain than in EB system. H owever , the compression strain in NSM system is slightly higher than EB at higher load level. The strengthen systems decrease the tensile strain and increase compression strain of RC beams. For strain along CFRP for both system s , the NSM system has lower CFRP strain than EB system. Energy dissipation with EB system is high er than with NSM system. NSM system show s more efficiency than EB system for load displacement behavior. In chapter four , the performance of EB and NSM system for continuous reinforcement concrete beams under a settlement of soil were examined as ten conti nuous RC beams were examined to observe the performance of RC beams strengthening with CFRP sheet and strips . T he test result s show the conclusion below: For unstrengthened continuous RC beams: Soil settlement decrease s the load carrying capacity of the be am by 1.5% and increase the span deflection. The tension strain at mid support area is higher than the tension at both mid spans. The tension strain at failure at span b (where a failure occurs) is higher than other location while the compression strain at the other span a is higher than span b. Soil settlement decrease s the tension strain of the span next to it. The energy dissipation of unstrengthened continuous RC beams has lower values when it ' s subjected to soil settlement than whe n it set on rigid sup ports. The continuous RC beams ha ve similar final failure modes as it fails due to section capacity by concrete crushing.

PAGE 232

205 E B strengthening system for continuous RC beams conclusion are: EB system improve s the load carrying capacity of continuous RC beams f or all assigned conditions. EB system show s higher load carrying capacity under cyclic loading. Also, soil settlement increases the load carrying capacity of EB RC continuous beams. EB system increase s the stiffness of con tinuous RC beams and shows good l oad displacement behavior. EB system with continuous RC beams show s acceptable resistance to settlement and cyclic loading. The continuous RC beam strain is reduced when EB system is used . Cyclic loading increases the strain of continuous EB RC beams while soil settlement reduces it. Cyclic loading increases the CFRP sh eet strain. However, soil settlement decreases the stain of CFRP sheet. Soil settle more with EB RC beams than unstrengthened beams as EB system carry a higher load. EB continuous RC beams sh ow low energy dissipation with rigid support condition. However, it has higher energy dissipation under soil settlement and with cyclic loading . EB continuous RC beams have similar failure modes as they failed by concrete crushing, some of them have CFRP r apture with concrete crushing. U wrap show effective enhancement for RC continuous beam strengthened with EB as it prevents CFRP sheet to debond from its end and improve RC beam resistance to shear stresses.

PAGE 233

206 The bonding interfacial between CFRP sheet and concrete show high strength as is start ing to debond from mid span at higher load level. For continuous RC beam strengthening with NSM system, the conclusions are: NSM system shows high load carrying capacity for continuous RC beams. However, soil settlem ent and/or cyclic loading decrease it for this system. NSM system improve s the load displacement behavior of RC beams , especially with rigid support conditions. But, EB system show s better behavior under soil settlement and/or cyclic loading. NSM system re duce s the RC beam strain. The strain of CFRP strip is lower than the strain induced in CFRP sheet. Some conclusions for cyclic load and soil settlement in EB is also the same for NSM system for strain in beams and CFRP. Soil settlement behavior for each te st is different even though the water ratio and density is controlled . Energy dissipation of continuous NSM RC beams under cyclic loading is lower than energy dissipation under monotonic load for both rigid support and soil settlement conditions. NSM syste m for continuous beams under soil settlement and cyclic loading has low energy dissipation than EB system. Failure modes for NSM system are similar to that in EB system. H owever , EB system failure mode is noisier.

PAGE 234

207 R EFERENCES Abdullah, A. H., & Abdul Kadir, M. (2016). NSM FRP Reinforcement for Strengthening Reinforced Concrete Beams Overview, 17. ACI committee 440. (2004). Guide for the design and construction of externally bonded FRP systems for strengthening existing structures . ACI committee 440 . Al Khafaji Andersland, O. B., a W. (1992). Geotechnical Engineering and Soil Testing, 695. Balkema. (2002). Soil Mechanics Basic Concepts And Engineering Applications. Barros, J. A. O., & Fortes, A. S. (2005). F lexural strengthening of concrete beams with CFRP laminates bonded into slits . Cement and Concrete Composites , 27 (4), 471 480. http://doi.org/10.1016/j.cemconcomp.2004.07.004 BASF Construction Chemicals. (2007). MBrace Composite Strengthening Systems Inte lligent solutions from . Bezih, K., Chateauneuf, A., Kalla, M., & Bacconnet, C. (2014). Effect of soil structure interaction on the reliability of reinforced concrete bridges. Ain Shams Engineering Journal , 6 (3), 755 766. http://doi.org/10.1016/j.asej.2015 .01.007 Bowles, J. E. (1997). Foundation Analysis and Design Fifth Edition . Engineering Geology (Vol. 20). http://doi.org/10.1016/0013 7952(84)90010 3 Colorado Geological Survay /Damages. (n.d.). Retrieved from http://coloradogeologicalsurvey.org/geologi c hazards/swelling soils/damages/ Das, B. M. (2011). GEOTECHNICAL ENGINEERING HANDBOOK . J. Ross Publishing. De Lorenzis, L., & Nanni, A. (2002). Bond between near surface mounted fiber reinforced polymer rods and concrete in structural strengthening. ACI Structural Journal , 99 (2), 123 132. http://doi.org/10.14359/11534 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. http://do i.org/10.1016/j.compositesb.2006.08.003 Dong, Y., Ansari, F., & Karbhari, V. M. (2011). Fatigue performance of reinforced concrete beams with externally bonded CFRP reinforcement. Structure and Infrastructure Engineering , 7 (3), 229 241. http://doi.org/10. 1080/15732470802383669

PAGE 235

208 Esfahani, M. R., Kianoush, M. R., & Tajari , a. R. (2007). Flexural behaviour of reinforced concrete beams strengthened by CFRP sheets. Engineering Structures , 29 , 2428 2444. http://doi.org/10.1016/j.engstruct.2006.12.008 Grace, N. F. (2003). ENVIRONMENTAL / DURABILITY EVALUATION OF FRP COMPOSITE Lawrence Technological University . Strengthening, 1 (9), 656 660. Holtz, G., & Hart, S. (1978). Home Construction on Shrinkage and Swelling Soil. American Socity of Civil Engineering . Julio, E. S., Branco, F., & Silva, V. D. (2003). Structural rehabilitation of columns with reinforced concrete jacketing. Progress in Structural Engineering and Materials , 5 (1), 29 37. http://doi.org/10.1002/pse.140 Kim, Y. J., & Bumadian, I. (2016). Electrochemical reactions for steel beams strengthened with CFRP sheets. Engineering Structures , 125 , 471 480. http://doi.org/10.1016/j.engstruct.2016.07.029 Kim, Y. J., Hossain, M., & Harries, K. A. (2013). CFRP strengthening of timber beams recovered from a 32year old quonset: E lement and system level tests. Engineering Structures , 57 , 213 221. http://doi.org/10.1016/j.engstruct.2013.09.028 Kim, Y. J., & Siriwardanage, T. (2016). Thermomechanical Behavior of Near Surface Mounted Carbon Fiber Reinforced Polymer Concrete Interface . ACI Structural Journal , 113 (2), 239 250. http://doi.org/10.14359/51687944 Krstelj, I. (1994). Manual of soil laboratory testing. Soil Dynamics and Earthquake Engineering , 13 (2), 147. http://doi.org/10.1016/0267 7261(94)90007 8 Lahri, A., & Garg, V. (20 15). EFFECT OF DIFFERENTIAL SETTLEMENT ON FRAME FORCES A PARAMETRIC STUDY. Lorenzis, L. De, & Nanni, a. (2002). Strengthening of Reinforced Concrete Structures with Near Surface Mounted FRP Rods Previous Work on NSM Rods. ACI Structural Journal , 1948 , 1 8. Retrieved from http://www.concrete.org/Publications/InternationalConcreteAbstractsPortal.aspx?m=det ails&i=11534 Materials, C. (1984). Constituent Materials and Properties, 41 70. Meier, U. R. S. (2000). Composite Materials in Bridge Repair. Applied C omposite Materials , 75 94.

PAGE 236

209 Namrou, A. R. (2013). an Experimental Investigation Into the . University of Colorado Denver. Nanni, a. (2005). Fiber Reinforced Polymer Composites for Infrastructure Strengthening From Research to Practice. University of Miss ouri . Retrieved from http://www6.miami.edu/cici/Documents/Conferences/2004/CF 2004 Nanni 2.pdf Orbanich, C. J., Dominguez, P. N., & Ortega, N. F. (2012). Strengthening and repair of concrete foundation beams with carbon fi ber composite materials. Materials and Structures , 45 (11), 1693 1704. http://doi.org/10.1617/s11527 012 9866 6 Osman, K. T. (2013). Soils Principles, Properties and Management . Springer Dordrecht Heidelberg New York London. http://doi.org/10.1007/978 94 0 07 5663 2 Parretti, R., & Nanni, A. (2004). Strengthening of RC Members Using Near Surface Mounted FRP Composites: Design Overview. Advances in Structural Engineering , 7 (6), 469 483. http://doi.org/10.1260/1369433042863198 Pellegrino, C., & Sena Cruz, J. (2015). Design Procedures for the Use of Composites in Strengthening of Reinforced Concrete Structures: State of the Art Report of the RILEM Technical Committee 234 DUC . http://doi.org/10.1007/978 94 017 7336 2 Rizkalla, S., Hassan, T., & Hassan, N. (200 3). Design recommendations for the use of FRP for reinforcement and strengthening of concrete structures. , 16 28. http://doi.org/10.1002/pse.139 Saileysh Sivaraja, S., Thandavamoorthy, T. S., Vijayakumar, S., Moses Aranganathan, S., & Dasarathy, A. K. (2013). Preservation of historical monumental structures using fibre reinforced polymer (FRP) Case studies. Procedia Engineering , 54 , 472 479. http://doi.org/10.1016/j.proeng.2013.03.043 Setunge, S., Nezamian, A., & Lokuge, W. (20 02). Review of strengthening techniques using externally bonded fiber reinforced polymer composites, 59. Siriwardanage, T. (2014). Mechanochemical investigation into bond performance of an NSM CFRP strengthening system at elevated temperatures, 184. Su, R. K. L., Cheng, B., Wang, L., Siu, W. H., & Zhu, Y. (2011). Use of bolted steel plates for strengthening of reinforced concrete beams and columns. The IES Journal Part A: Civil & Structural Engineering , 4 (2), 55 68. http://doi.org/10.1080/19373260.2011.56 7816 Subramanian, N. (2010). Properties of Soils. Design of Steel Structures , 1396 1400.

PAGE 237

210 Täljsten, B., & Blanksvärd, T. (2007). Mineral Based Bonding of Carbon FRP to Strengthen Concrete Structures. Journal of Composites for Construction , 11 (2), 120 128 . http://doi.org/10.1061/(ASCE)1090 0268(2007)11:2(120) Uma Shankar .K, A. P. . . & P. K. . . (2015). Rehabilitation and Retrofitting of Building Structures. BEST: International Journal of Management, Information Technology and Engineering (BEST: IJMITE) , 3 (1), 5 10. Retrieved from http://www.bestjournals.in/view_archives.php Wang, W. W., Dai, J. G., & Harries, K. a. (2013). Performance Evaluation of RC Beams Strengthened with an Externally Bonded FRP System under Simulated Vehicle Loads. Journal of Bridg e Engineering , 18 (1), 76 82. http://doi.org/10.1061/(ASCE)BE.1943 5592.0000324 World, T., Architectural, L., Sculpture, F., Great, T., Resort, A., & Island, P. (2014). A r c h i t e c t u r a l 903.454.0904 p r o d u c t s. Wu, Z., Li, W., & Sakuma, N. ( 2006). Innovative externally bonded FRP/concrete hybrid flexural members. Composite Structures , 72 (3), 289 300. http://doi.org/10.1016/j.compstruct.2004.12.002 Wu, Z., & Yin, J. (2003). Fracturing behaviors of FRP strengthened concrete structures. Enginee ring Fracture Mechanics , 70 (10), 1339 1355. http://doi.org/10.1016/S0013 7944(02)00100 5