seismic retrofit of low-ductile columns through...

SEISMIC RETROFIT OF LOW-DUCTILE COLUMNS THROUGH CONCRETE

JACKETING WITH INOXYDABLE REINFORCEMENT

YOUSEF KARIMI VAHED

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Doctor of Philosophy (Civil Engineering)

Faculty of Civil Engineering

Universiti Teknologi Malaysia

JULY 2017

iii

DEDICATION

"Specialty Dedicated To...

M y Beloved Father, M other, Wife, daughters, Sisters, and B rothers

Thanks for all the love, support, motivation and always being there

whenever I need you

M y Supervisors

Dr. Sophia C. Alih

And

Dr. Mohamadreza Vafaei

For their guidance and assistance throughout the whole thesis"

iv

ACKNOW LEDGEM ENT

Praise to God almighty, the compassionate and the merciful, who has created

mankind with wisdom and given them knowledge.

At first, I would like to thank my main supervisor and advisor, Dr. Sophia C.

Alih, for his kind encouragement, earnest guidance, appreciative advices, and

friendly motivations. I also wish to thank my co-supervisor Dr. Mohammadreza

Vafaei, for them grateful advices and impetus. Without continuous support from my

main supervisor and my co-supervisor, this research would not be the same as

presented in this thesis.

In second, I would like to thank the Dean, head of structure and materials

department and all lecturers and staff of the faculty of civil engineering UTM for the

facilities provided by them that support me to do this research.

Last but not least, I want to express grateful thanks to my family; my father

and mother, my wife, my daughters, my sisters and brothers for their unlimited

supports. Without their consistent supports and encouragement, it was impossible for

me to accomplish this work.

v

ABSTRACT

Retrofit of structures often is an inevitable task especially when buildings are not designed for seismic actions or their design has followed older design codes. Many retrofit strategies have been proposed and practiced by previous researchers. Usage of fiber reinforced polymer [FRP], steel jacketing and reinforcement jacketing are among the most common retrofitting methods. For reinforcement jacketing, carbon steel has been widely employed by engineers, however, only a few applications of inoxydable reinforcements can be found in the literature. Moreover, when it comes to reinforcement jacketing, connection between the interface of original column and the jacket plays an important role and has attracted the attention of many researchers. Load transfer mechanism between original column and jacket is another field of study which has not been addressed in previous research. In this study application of inoxydable rebars for seismic retrofit of Reinforced Concrete (RC) columns was investigated. Two new connectors were used to increase the integrity between the original column and jacket. Load transfer mechanism between original column and jacket is another topic addressed in this research. This study included experimental and numerical analysis. For experimental study, 8 full scale RC columns were constructed and retrofitted with different reinforcement jacketing configurations. Numerical studies investigated the effect of different axial forces on the obtained results from experimental test. Results indicated that regardless of the employed retrofit configurations, the retrofitted columns have higher initial stiffness and ultimate strength compared to unretrofitted columns. However, the retrofitted columns showed significantly lower ductility ratio when compared with un-retrofitted columns. All the retrofitted columns displayed a brittle failure mode in which spalling of concrete at the base of columns occurred without yield or buckling of reinforcements. Results indicated that confined jackets have higher ultimate strength and stiffness compared to un-confined jackets. However, they showed a lower ductility ratio when compared with un-confined jackets. It was observed that, when internal angle connection was used for retrofit, the highest ultimate strength, post-yield stiffness and effective stiffness were achieved. Monitoring the strain distribution between jackets and original columns revealed that confinement in jackets reduced the strain in the longitudinal reinforcement of original columns more than un-confined jackets. Strain values in the stirrups of confined jackets were significantly smaller than that of un-confined jackets. Strain ratios on the surface of concrete of confined jackets were larger than that of unconfined jackets. It is concluded that the proposed connectors have improved the ultimate strength of retrofitted columns as compared to conventionally retrofitted column, as they were unable to elevate the ultimate strengths to the level of a monolithic column.

vi

ABSTRAK

Pengubahsuaian struktur sering kali merupakan tugas yang tidak dapat dielakkan terutamanya apabila bangunan tidak direka untuk tindakan seismik atau reka bentuknya menggunakan kod reka bentuk yang lebih lama. Banyak kaedah pemulihan struktur telah dicadangkan dan diamalkan oleh penyelidik terdahulu. Penggunaan polimer bertetulang gentian [FRP], pembungkus keluli dan pembungkus tetulang adalah antara kaedah pengubahsuaian yang paling biasa. Untuk pembungkus tetulang, keluli karbon telah digunakan secara meluas oleh para jurutera, bagaimanapun, hanya beberapa aplikasi pembasmian anti-karat yang dapat ditemui dalam kajian terdahulu. Lebih-lebih lagi, untuk kaedah pembungkus bertetulang, hubungan antara tiang dan pembungkus memainkan peranan penting dan telah menarik perhatian ramai penyelidik. Mekanisma pemindahan beban antara tiang dan pembungkus konkrit merupakan salah satu bidang yang masih belum diterokai oleh penyelidik terdahulu. Dalam kajian ini, penggunaan keluli anti-karat untuk pemulihan tiang konkrit berterulang terhadap beban gempa bumi dikaji. Dua jenis penyambung telah digunakan untuk meningkatkan integriti antara tiang dan pembungkus. Mekanisma pemindahan beban antara tiang dan pembungkus konkrit merupakan salah satu topik yang turut dikaji dalam kajian ini. Kajian ini melibatkan kerja-kerja makmal dan analisis berangka. Untuk kajian eksperimen, 8 tiang konkrit berterulang berskala penuh telah dibina dan dipasang dengan konfigurasi pembungkus bertetulang yang berbeza. Analisis berangka mengkaji kesan penggunaan beban paksi yang berbeza terhadap keputusan yang diperolehi daripada kajian makmal. Keputusan kajian menunjukkan bahawa tanpa mengira konfigurasi baik pulih yang digunakan, tiang yang diubahsuai mempunyai kekukuhan awal yang lebih tinggi, kekuatan muktamad dan anjakan berbanding dengan tiang yang tidak diubahsuai. Walau bagaimanapun, tiang yang diubahsuai menunjukkan nisbah kemuluran yang rendah berbanding dengan tiang yang tidak diubahsuai. Semua tiang yang diubahsuai memaparkan sifat kerapuhan di mana pemisahan konkrit pada dasar tiang berlaku tanpa alah atau lengkokan pada tetulang. Keputusan kajian menunjukkan bahawa pembungkus terkurung mempunyai kekuatan dan kekukuhan yang lebih tinggi berbanding pembungkus tidak terkurung. Walau bagaimanapun, ia menunjukkan nisbah kemuluran yang lebih rendah jika dibandingkan dengan pembungkus terkurung. Telah diperhatikan bahawa, apabila sambungan sudut dalaman digunakan untuk kerja pengubahsuaian, kekuatan muktamad yang tertinggi, kekakuan pasca-lengkokan, dan kekakuan berkesan telah dicapai. Pemerhatian terhadap agihan terikan antara pembungkus dengan tiang mendedahkan bahawa pengurungan dalam pembungkus telah mengurangkan terikan dalam tetulang membujur lebih daripada pembungkus tidak terkurung. Nilai terikan pada tetulang pengikat dalam pembungkus terkurung adalah jauh lebih rendah daripada pembungkus tidak terkurung. Nisbah terikan pada permukaan konkrit untuk pembungkus terkurung juga lebih besar daripada pembungkus tidak terkurung. Dapat disimpulkan bahawa penyambung yang dicadangkan telah meningkatkan kekuatan muktamad tiang yang diubahsuai berbanding tiang yang dipasang secara konvensional, kerana penyambung ini tidak dapat meningkatkan kekuatan muktamad ke tahap tiang monolitik.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOW LEDGEM ENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xiii

LIST OF FIGURES xvi

LIST OF ABBREVIATIONS xxiv

LIST OF SYMBOLS xxv

LIST OF APPENDICES xxix

1 INITRODUCTION 1

1.1 Introduction 1

1.2 Problem statement and motivation for research 4

1.3 Objectives of the study 6

1.4 Research Scope 7

1.5 Significant of the research 8

1.6 Outline of the Thesis 8

2 LILITERATURE REVIEW 10

2.1 Introduction 10

2.2 Types of seismic induced damage to column 11

2.3 Seismic codes requirement 15

2.3.1 American Concrete Institute (ACI) 15

2.3.1.1 Reinforcement details for columns 15

2.3.1.2 Stirrup and tie hooks 16

2.3.1.3 Minimum bend diameters 17

2.3.1.4 Spacing limits for reinforcement 18

2.3.1.5 Cast-in-place concrete (non-prestressed) 18

2.3.2 Eurocode8 (EN1998-1) 19

2.3.2.1 Design for DC M 19

2.3.2.2 Design for DC H 22

2.4 Seismic retrofit of columns using fiber-reinforced polymer 24

2.4.1 Behavior of Low-Ductile Reinforced Concrete

Columns with FRP Jackets 25

2.4.1.1 Axial Behaviour 25

2.4.1.2 Lateral Behavior 28

2.4.2 Advantages and Disadvantages of the Use of FRP

Materials 43

2.5 Seismic retrofit of columns using steel plates 44

2.5.1 Experimental Behavior of Steel Jacketed

Reinforced Concrete Columns 44

2.5.2 Advantages and disadvantages of the use of steel

jacket 52

2.6 Seismic retrofit of columns using reinforcement jacketing 53

2.6.1 Experimental Behavior of Concrete Jacketed

Reinforced Concrete Columns 54

2.6.2 Interface preparation in concrete jacketing 62

2.6.3 Advantages and disadvantages of the concrete

jacketing 64

2.7 Application of inoxydable rebar in structures 65

2.7.1 Experimental tests on behaviour of inoxydable

rebar in concrete columns 67

2.7.2 Advantage of inoxydable steel 71

2.8 Analytical analysis 722.9 Summary 76

viii

ix

RRESEARCH M ETHODOLOGY 78

3.1 Introduction 78

3.2 Research Design 78

3.3 Experimental studies 80

3.3.1 Size, scale and material properties of

experimentally tested specimens 81

3.3.2 Determination of construction stages 92

3.3.3 Instrumentation and test set up 99

3.3.3.1 LVDTs 100

3.3.3.2 Strain Gages 101

3.3.3.3 Load cells 104

3.3.4 Experimental Test setup 105

3.3.5 Material test 107

3.3.5.1 Concrete test 108

3.3.5.2 Tensile strength test of reinforcements 110

3.3.5.3 Tests on epoxy glue 112

3.3.6 Loading protocol 114

3.3.7 Numerical studies 115

EXPERIM ENTAL RESULTS AND ANALYSIS 116

4.1 Introduction 116

4.2 Failure mechanism of tested specimens 117

4.2.1 Un-retrofitted columns 118

4.2.1.1 Specimen Number 1 118

4.2.1.2 Specimen number 2 119

4.2.2 Column retrofitted by conventional method 121

4.2.2.1 Unconfined Specimen 121

4.2.2.2 Confined Specimen 123

4.2.3 Column retrofitted by external rod connector 125



4.2.4 Column retrofitted by internal angle connector 128



4.3 Hysteresis loops and backbone curves 132

3

4


4.3.1.1 Specimen number 1 133



4.3.2.1 Un-confined Specimen 136








4.4 Bilinear representations of backbone curves 145













4.5 Stiffness Degradation 159





4.6 Energy dissipation capacity 165

4.6.1 Un- retrofitted columns 166




x

xi

4.7 Strain distribution in the retrofitted specimens 171

4.7.1 Strain distribution under axial loading 171

4.7.1.1 Column retrofitted by conventional method 172

4.7.1.2 Column retrofitted by external rodconnector 174

4.7.1.3 Column retrofitted by internal angleconnector 176

4.7.2 Strain distribution in the elastic range under

combination of axial and lateral loads 179




4.7.3 Strain distribution at ultimate strength 187




4.8 Summary 194

5 NUM ERICAL ANALYSIS AND DISCUSSION 197


5.2 Finite Element Simulation 197

5.2.1 Selection of Appropriate Software 198

5.2.1.1 Finite element (FE) modeling inANSYS software 198

5.2.1.2 ANSYS Solution Control 209

5.3 Validation of finite element model 210

5.3.1 Un-retrofitted column 210




5.3.4 Concluding remark on validation of software 215

5.4 Study on seismic behavior of low-ductile and high

ductilecolumn 216

xii

5.5 Effects of axial force on cyclic behavior of

experimentally tested columns 217

5.5.1 Un-retrofitted column 217




5.5.5 Concluding remark on the effect of axial load

intensity 224

5.6 Calculation of lower and upper bound ultimate strength

of retrofitted column 224

6 CONCLUSION 228


6.2 Seismic Behavior of Low Ductile RC Columns 228

6.3 Effectiveness of reinforcement jacketing for seismic

retrofit of low ductile column 229

6.4 Study on load transfer mechanism between original

column and jackets 231

6.5 Development of new connectors 231

6.6 Contribution to knowledge 232

6.7 Recommendation for future works 233

REFERENCES 234

Appendices A - B 243-286

xiii

TABLE NO.

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

2.10

2.11

2.12

2.13

3.1

3.2

LIST OF TABLES

TITLE

Minimum diameter of bend (Committee et al., 2008)

Tolerances of d (Committee et al., 2008)

Limitation for cover for reinforcement (Committee et al., 2008)

Typical strength and stiffness values for material used in retrofitting (Gunaslan, Kara§in, & Oncu, 2014)

Experimental results of axial tests of columns confined with CFRP jackets (Demers, 1995)

Experimental results of full scale axial tests of reinforced concrete columns confined with CFRP and GFRP jackets (Kestner et al. 1997).

Experimental investigation of reinforced concrete columns with FRP jackets retrofits (Walkup, 1998)

Experimental investigations of steel and CFRP column retrofits conducted at UCSD (Seible, Priestley, & Innamorato, 1995)

Experimental investigations of steel and GFRP column retrofits conducted at UCSD (Priestly et al., 1992)

Experimental investigations of reinforced concrete columns with steel jacket retrofits (Walkup, 1998).

Details of Steel Jacketing (Waghmare, 2011).

Detail for Reinforced Concrete Jacketing (Waghmare, 2011)

Mechanical Properties of Some Reinforcing Bar Alloys (McGurn, 1998)

Type of specimens tested in this study

Position of LVDTs

PAGE

17

17

19

25

26

28

29

34

38

46

48

57

67

83

101

xiv

3.3 Installation height of strain gauges measured from the topof foundation 104

3.4 Average compressive strength of concrete used infoundation, original column and jacket 109

3.5 Calculation of E value and Poisson's ratio of concreteof original column and jacket 110

3.6 Tensile strength test results for Plain Rebar(R8 and R20), Ribbed Rebar (Y10 and Y20) andinoxydable steel rebar (S20) 112

3.7 Result of pull out test 114

4.1 Type of specimens tested in this study 117

4.2 Crack numbers and their corresponding drift values for CC1 119

4.3 Crack numbers and their corresponding drift values for CC2 121

4.4 Crack numbers and their corresponding drift values forJCMU 123

4.5 Crack numbers and their corresponding drift values forJCMC 124

4.6 Crack numbers and their corresponding drift values forJERU 126

4.7 Crack numbers and their corresponding drift values forJERC 128

4.8 Crack numbers and their corresponding drift values forJIAU 130

4.9 Crack numbers and their corresponding drift values forJIAC 131

4.10 Crack members and their corresponding drift values forall samples 131

4.11 Force and displacement for all samples 145

4.12 Extracted parameters from the idealized backbone curvefor CC1 148

4.13 Extracted parameters from the idealized back bone curvefor CC2 149

4.14 Extracted parameters from the idealized back bone curvefor JCMU 151

4.15

4.16

4.17

4.18

4.19

4.20

4.21

4.22

4.23

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

xv

Extracted parameters from the idealized back bone curve for JCMC 152

Extracted parameters from the idealized back bone curve for JERU 154

Extracted parameters from the idealized back bone curve for JERC 155

Extracted parameters from the idealized back bone curve for JIAU 157

Extracted parameters from the idealized back bone curve for JIAC 158

Extracted parameters from the idealized back bone curve for all samples 159

Stiffness degradation of all samples 165

cumulative energy dissipation for all samples 171

Summary of obtained experimental results 196

Coefficient of friction and adhesion values 208

Comparison between initial stiffness, ultimate load and displacement of columns. 215

Result of FE models with different axial load for CC 218

Result of FE models with different axial load for JCMU 219

Result of FE models with different axial load for JCMC 220

Result of FE models with different axial load for JERU 221

Result of FE models with different axial load for JERC 222

Result of FE models with different axial load for JIAU 223

Result of FE models with different axial load for JIAC 224

xvi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Retrofitting methods for columns (a) reinforced concretejacketing, (b) steel jacketing, (c) FRP wrapping. 2

1.2 Reinforced concrete jacketing; a) jacketing of columns and beams (Sabu and Pajgade, 2012), b) jacketing of columnsand foundations (ENUICA et al.) 3

2.1 Potentially inadequate reinforcing columnsdetails (Walkup, 1998) 12

2.2 Full length diagonal shear cracks resultingfrom short-column behaviour (Baiet al.,2003) 13

2.3 Damage to non-ductile columns (Bai et al., 2003) 14

2.4 a) Stiffness against displacement for all specimens. b)Dissipated energy rate for all specimens. c) Cumulative dissipated energy for all specimen (Konstantinos G.Vandoros & Dritsos, 2008). 59

2.5 Alternative methods for connecting old columns to jackets a) bent down bars, b) usage of dowels, c) Welded jacketstirrup geometry (Vandoros and Dritsos, 2008). 64

2.6 Details of the plastic hinge at the final stage (Franchi et al.,2006) 68

2.7 Repair and retrofitting of pier (Albanesi et al., 2008) 71

2.8 Square RC section reinforced with a RC jacket 71

2.9 Stress-strain curve for concrete of core 71

2.10 Repair and retrofitting of pier (Albanesi et al., 2008)

condition in a RC jacketed section 75

3.1 Research methodology employed in this study 79

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

3.10

3.11

3.12

3.13

3.14

3.15

3.16

3.17

3.18

xvii

a) Reinforcement details, b) section details 82

Design of the CC; a) column dimension and reinforcement detailing, b) reinforcement skeleton, c) whole column. 84

Design of the JCMU; a) dimension and rebar detailing, b) reinforcement skeleton, c) reinforcement for jacketing, d) completed retrofitted column. 85

Design of the JCMC; a) dimension and rebar detailing, b) reinforcement skeleton, c) reinforcement for jacketing, d) completed retrofitted column. 86

Design of the JERU; a) dimension and rebar detailing, b) reinforcement skeleton, c) reinforcement for jacketing, d) completed retrofitted column. 87

Design of the JERC; a) dimension and rebar detailing, b) reinforcement skeleton, c) reinforcement for jacketing, d) completed retrofitted column. 88

Design of the JIAU; a) dimension and rebar detailing, b) reinforcement skeleton, c) reinforcement for jacketing, d) completed retrofitted column. 89

Design of the JIAC; a) dimension and rebar detailing, b) reinforcement skeleton, c) reinforcement for jacketing, d) completed retrofitted column. 90

Set up of internal angle connector 91

Set up of external angle connector 92

Construction stage of foundation; a) reinforcement mesh, b) concrete pouring 94

Set up of original column's reinforcement 95

Construction stages of retrofitted columns; a) pouring of concrete, b) concrete casting, c) curing of specimens 96

Preparation for jacketing; a) epoxy glue, b)injecting epoxyc)using core machine to made holes 97

Set up of jacket reinforcement; a) preparing reinforcement of jackets b) installed reinforcing cages into the hole. 98

Construction and curing of jacket's concrete; a) columns ready to be concreted, b) section of jacket, c) concrete pouring, d) concrete curing. 99

The position of LVDT s 100

xviii

3.19

3.20

3.21

3.22

3.23

3.24

3.25

3.26

3.27

3.28

3.29

3.30

4.1

4.2

4.3

4.4

4.5

Type of LVDT use in experimental test 101

Strain gauge set up; a) strain gauge on foundation rebars, b) fastening column concrete strain gauge and column reinforcement strain gauges 102

Location of strain gauges; a) rebars of original column, b) concrete surface of original column, c) rebars of jackets, d) surface of concrete jacket. 103

Load cell installation 105

Details of an instrumented specimens 107

compressive test of concrete 108

Test of modulus of elasticity of concrete 109

Tensile strength test; a) rebars specimen, b) tensile strength testing machine, c) specimens after testing. 111

Stress-strain curves of three samples of inoxydablesteel reinforcement bars, 20mm diameter 111

Stress-strain curves of three samples of ribbed carbon steel

reinforcement bars, 20mm diameter 112

Pull out test on epoxy glue; a) prepared samples, b) test set up, c) failure of the sample 113

The employed load protocol according to FEMA 461 (Agency, 2007) 115

Layout of loading direction 117

Crack patterns for CC1 a) crack pattern in S direction, b) crushing of concrete at ultimate load, c) exposing of longitudinal reinforcement. 119

Crack patterns for CC2 a) Crack pattern in S direction b)Crushing of concrete at ultimate load c) Exposing of longitudinal reinforcement 120

Crack patterns for JCMU a) Crack pattern in S direction b) Crushing of concrete at ultimate lad c) Exposing of longitudinal reinforcement 122

Crack patterns for JCMC (a) Crack pattern in S direction b) Crushing of concrete at ultimate load c) Exposing of longitudinal reinforcement. 124

4.6

4.7

4.8

4.9

4.10

4.11

4.12

4.13

4.14

4.15

4.16

4.17

4.18

4.19

4.20

4.21

4.22

4.23

4.24

4.25

4.26

4.27

xix

Crack patterns for JERU (a) Crack pattern in S direction b) Crushing of concrete at ultimate load c) Exposing of longitudinal reinforcement 126

Crack patterns for JERC (a) Crack pattern in S direction b) Crushing of concrete at ultimate load c) Exposing of longitudinal reinforcement 128

Crack patterns for JIAU (a) Crack pattern in S direction (b) Crushing of concrete at ultimate load c) Exposing of longitudinal reinforcement 129

Crack patterns for JIAC (a) Crack pattern in S direction b) Crushing of concrete at ultimate load c) Exposing of longitudinal reinforcement 131

Hysteresis loop of CC1 134

Backbone curves of CC1 134

Hysteresis loop of CC2 135

Backbone curve of CC2 135

Hysteresis loop of JCMU 137

Backbone curve of JCMU 137

Hysteresis loop of JCMC 138

Backbone curve of JCMC 138

Hysteresis loop of JERU 140

Backbone curve of JERU 140

Hysteresis loop of JERC 141

Backbone curve of JERC 141

Hysteresis loop of JIAU 143

Backbone curve of JIAU 143

Hysteresis loop of JIAC 144

Backbone curve of JIAC 144

Idealized force displacement curve adopted from FEMA356 (FEMA, 2000) 146

Bilinear representation of backbone curve for CC1 147

xx

4.28 Bilinear representation of backbone curve for CC2 149

4.29 Bilinear representation of backbone curve for JCMU 150

4.30 Bilinear representation of backbone curve for JCMC 152

4.31 Bilinear representation of backbone curve of JERU 153

4.32 Bilinear representation of backbone curve for JERC 155

4.33 Bilinear representation of backbone curve for JIAU 157

4.34 Bilinear representation of backbone curve of JIAC 158

4.35 Stiffness degradation of CC 160

4.36 Stiffness degradation of JCM 162

4.37 Stiffness degradation of JER 163

4.38 Stiffness degradation of JIA 165

4.39 Schematic view of energy 166

4.40 Cumulative Energy dissipation for CC 167

4.41 Cumulative Energy dissipation of JCM 168

4.42 Cumulative energy dissipation curve of JER 169

4.43 Cumulative energy dissipation curve of JIA 170

4.44 Strain ratios under axial load for longitudinal reinforcement of JCM 173

4.45 Strain distribution under axial load for transverse reinforcement of JCM 173

4.46 Strain distribution under axial load for concrete of JCM 174

4.47 Strain ratios under axial load for longitudinal reinforcement of JER 175

4.48 Strain distribution under axial load for transverse reinforcement of JER 176

4.49 Strain distribution under axial load for concrete of JER 176

4.50 Strain distribution under axial load for longitudinalreinforcement of JIA 178

xxi

4.51

4.52

4.53

4.54

4.55

4.56

4.57

4.58

4.59

4.60

4.61

4.62

4.63

4.64

4.65

4.66

4.67

4.68

4.69

4.70

Strain distribution under axial load for transverse reinforcement of JIA 178

Strain distribution under axial load for concrete of JIA 179

Strain distribution in the elastic range under axial andlateral loads for longitudinal reinforcement of JCM 181

Strain distribution in the elastic range under axial andlateral loads for transverse reinforcement of JCM 181

Strain distribution in the elastic range under axial andlateral loads for concrete of JCM 182

Strain distribution in the elastic range under axial andlateral loads for longitudinal reinforcement of JER 183

Strain distribution in the elastic range under axial andlateral loads for transverse reinforcement of JER 184

Strain distribution in the elastic range under axial andlateral loads for concrete of JER 184

Strain distribution in the elastic range under axial andlateral loads for longitudinal reinforcement of JIA 186

Strain distribution in the elastic range under axial andlateral loads for transverse reinforcement of JIA 186

Strain distribution in the elastic range under axial andlateral loads for concrete of JIA 187

Strain distribution at ultimate strength for longitudinal reinforcement of JCM 188

Strain distribution at ultimate strength for transverse reinforcement of JCM 189

Strain distribution at ultimate strength for concrete of JCM 189

Strain distribution at ultimate strength for longitudinalreinforcement of JER 191

Strain distribution at ultimate strength for transverse of JER 191

Strain distribution at ultimate strength for concrete of JER 192

Strain distribution at ultimate strength for longitudinalreinforcement of JIA 193

Strain distribution at ultimate strength for transverse of JIA 194

Strain distribution at ultimate strength for concrete of JIA 194

xxii

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

5.10

5.11

5.12

5.13

5.14

5.15

5.16

Stress-strain curve for un-confined concrete with 30MPa compressive strength

Stress-strain curve of reinforcement with 20mm diameter

Simplified stress-strain curve used for the concrete of jackets

Solid element used for simulating nonlinear behavior of concrete

LINK8 3-D spar elements (Reproduced from ANSYS manual version 14.0)

Finite element model of CC; a) concrete sections, simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Finite element model of JCMU; a) concrete sections simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Finite element model of JCMC; a) concrete sections simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Finite element model of JIAU; a) concrete sections simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Finite element model of JIAC; a) concrete sections simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Finite element model of JERU; a) concrete sections simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Finite element model of JERC; a) concrete sections simulated by SOLID65 element, b) reinforcements simulated by LINK8 element

Bond-slip curve for ribbed reinforcement embedded in concrete [ANSYS manual, ver16]

Boundary conditions of supports

Interface shear stress distribution(Lampropoulos and Dritsos, 2011)

Comparison of FE model and experimental tests for CC; a) hysteresis loops, b) backbone curve

199

200

200

201

202

202

203

203

204

204

205

205

207

207

209

211

xxiii

5.17 Comparison between results of FE model and experimentaltest of JCMU; a) hysteresis loops, b) backbone curve 212

5.18 Comparison between results of FE model and experimentaltest of JCMC; a) hysteresis loops, b) backbone curve 212

5.19 Comparison between results of FE model and experimentaltest of JERU; a) hysteresis loops, b) backbone curve 213

5.20 Comparison between results of FE model and experimentaltest of JERC; a) hysteresis loops, b) backbone curve 213

5.21 Comparison between results of FE model and experimentaltest of JIAU; a) hysteresis loops, b) backbone curve 214

5.22 Comparison between results of FE model and experimentaltest of JIAC; a) hysteresis loops, b) backbone curve 214

5.23 Backbone curve of high ductile and low-ductile unretrofitted column under cyclic load 216

5.24 Backbone curves of CC 217

5.25 Backbone curves of JCMU 218

5.26 Backbone curves of JCMC 219

5.27 Backbone curves of JERU 220

5.28 Backbone curves of JERC 221

5.29 Backbone curves of JIAU 222

5.30 Backbone curves of JIAC 223

5.31 Hysteresis loops for un-confined condition ofmonolithic retrofitted column 225

5.32 Hysteresis loops for confined condition ofmonolithic retrofitted column 226

5.33 Hysteresis loop of original column 227

5.34 Hysteresis loop of jacket 227

xxiv

LIST OF ABBREVIATIONS

ACI - American Concrete Institute

CFTP - Carbon Fiber Reinforcement Polymer

FE - Finite Element

FEMA - Federal Emergency Management Agency

FEM - Finite Element Method

FRP - Fiber Reinforced Polymer

GFRP - Glass Fiber Reinforced Polymer

LVDT - Linear Variable Displacement Transducer

RC - Reinforced Concrete

SS - Stainless Steel

DC L - Low Ductility Class

DC M - Medium Ductility Class

DC H - High Ductility Class

CCDF - Conventional Curvature Ductility Factor

HSW - High Strength Wire

SCC - Consolidating Concrete

LCC - Life Cyclic Cost

xxv

LIST OF SYMBOLS

s,req

s,prov

Astc

Astj

As

As

Ag

Ast

bc

bo

bo

bi

Cj

Cc

dc

Do

dbL

db

d

Ec

Esce

cross section area of the legs in the core and jacket stirrups

cross section area of the legs in the core and jacket stirrups

requirement reinforcement

provisions reinforcement

gross area of section

total area of longitudinal reinforcement

gross cross-sectional width

width of confined core (to the centerline of the hoops)

minimum dimension of the concrete core

distance between consecutive engaged bars

compressive force in the concrete jacket

compressive force in the concrete core

distance of the resultant compressive force in the concrete jacket

from the neutral axis

diameter of confined core

minimum diameter of longitudinal bars

reinforcement diameter

distance from extreme compression fiber to centroid of longitudinal

tension reinforcement

elastic modulus of concrete

secant modulus of concrete

xxvi

Fj - forces in tension steel of the jacket

F'j - forces in compression steel of the jacket

Fc - forces in tension steel of the core

F'c - forces in compression steel of the core

fysc - yield stress of stirrups in the core

fysj - yield stress of stirrups in the jacket

fcu - stress corresponding to stirrup fracture strain

fc,min - minimum compressive strength of the old or the new concrete in MPa

fcc - maximum principal compressive stress by jacketing

fcc - compressive strength of confined concrete

fc0 - strength of unconfined concrete

ho - depth of confined core (to the centerline of the hoops)

hc - gross cross-sectional depth

hc - largest cross-sectional dimension of the column,

hcr - height of the critical region

hs - clear story height

K - confinement ratio

Ke - effective lateral stiffness

Ki - elastic lateral stiffness of the building in the direction under

consideration

Ke - effective lateral stiffness of the building in the direction under

consideration

lcr - the length of the critical region

lcl - clear length of the column

xxvii

n - total number of longitudinal bars laterally engaged by hoops or

cross ties,

Proc - axial strength of RC jacketed column by considering confinement

q - behaviour factor

s - spacing of hoops

s - sliding in mm at the interface

sfu - maximum value of sliding at the interface

T1 - fundamental period of the building

Te - period of upper limits of the constant spectral acceleration branch

Ti - effective fundamental period (in seconds) in the direction under

consideration calculated by elastic dynamic analysis

x - normalized strain

Vy - effective yield strength

a - confinement effectiveness factor

Ssy,d - design value of tension steel strain at yield,

s - axial strain

Scc - axial strain corresponding to the peak stress in confined concrete

Sc0 - strain of unconfined concrete

scc - the strain corresponding to the peak stress, fcc

p,1 - coefficient of friction or the initial value of the coefficient of

friction when considering cyclic loading

- required value of CCDF

Vd - normalized design axial force

Ps - longitudinal reinforcement ratio

Py - longitudinal reinforcement ratio at yield conditions

O1

Oc

Oc

Tf

Tfud

^c

^s

normal stress at the interface or the initial value of the normal stress

at the interface in Mpa

normal stress at the interface in Mpa

compressive stress in the concrete

roughened interface shear stress in Mpa

ultimate value of the shear stress in Mpa

concrete resistance factors

steel resistance factors

xxviii

xxix

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Material tests results 259

B Results of measured strain values 284

CHAPTER 1

INTRODUCTION

1.1 Introduction

It is well known that many buildings designed based on older codes may be

susceptible to severe damage during strong earthquakes. Older buildings have been

structurally designed for much lower seismic actions compared to buildings that are

designed today. This is because the relevant seismic codes have been continually

revised as knowledge about seismic behavior has increased.

Many reinforced concrete frame structures that are built prior to the 1970's

were designed for either gravity loads alone, or combination of gravity loads and

wind loads. Seismic loads often were not considered in the design of these structures.

Reinforcing details used in these structures are now recognized as the cause of low-

ductile failure modes under seismic loading. As a result, poor performance of these

structures is anticipated and observed under moderate to severe seismic loading.

Columns as structural members that transfer gravity loads to foundations play

significant role in structural stability. However, due to the poor reinforcing details,

and lack of consideration of seismic loads in the initial design, columns are often

found to be vulnerable in low-ductile reinforced concrete structures.

In addition to the above mentioned reasons, column retrofitting are necessary

and inevitable due to changes in building's functionality, changes in architectural

plans and designs that have not considered forces attributed to collision or explosion.

2

Jacketing is a method often used to retrofit reinforced concrete columns.

Columns may be jacketed through addition of reinforced concrete, steel plates, or

various types of fiber reinforced polymer (FRP) materials. Jackets may be used to

restore (in the case of damaged or deteriorated columns), maintain, or increase axial

load capacity, flexural capacity, and/or shear capacity. Figure 1.1 displays a

schematic view of three different retrofit methods for columns. Among retrofit

methods of columns, reinforced concrete jacketing has received increasing attention

especially for practical application. Low cost, simplicity and reliability are the most

important factors for such widespread application in real projects. Figure 1.2 shows

some real retrofit cases where RC jacketing is employed for retrofit of columns.

Previous studies indicated significant increase in strength and stiffness of retrofitted

RC elements through jacketing.

Figure 1.1 Retrofitting methods for columns (a) reinforced concrete jacketing, (b) steel jacketing, (c) FRP wrapping.

3

(a) (b)

Figure 1.2 Reinforced concrete jacketing; a) jacketing of columns and beams (Sabu and Pajgade, 2012), b) jacketing of columns and foundations (ENUICA et al.)

In spite of advantages that RC jacketing offers, application of this retrofit

strategy has privilege for normal environmental condition. Conventional carbon steel

used in reinforcing bars is a corrodible material, therefore, in a harsh environmental

condition, like piers of bridges or columns constructed inside sea water undergoes a

rapid decay. One solution to this problem is the usage of inoxydable rebars that can

resist against corrosion even under a harsh environmental condition.

Despite having higher strength and higher ductility compared to the

conventional carbon steel, the usage of inoxydable steel for jacketing has not yet

being explored. In fact, the application of this type of reinforcement is still new in the

construction industry and limited study has been conducted. It is noteworthy that so

far conducted research on RC jacketing (Dritsos, et. al., 1997; Julio, et. al., 2003;

Julio, et. al., 2005; Kaliyaperumal & Sengupta, 2014; Vandoros & Dritsos, 2008)

has only utilized the conventional carbon steel as the longitudinal bars.

In addition to the superior mechanical properties as compared to carbon steel,

inoxydable rebar has an inherent anti-corrosion characteristic which priorities its

usage for harsh environment (Alih & Khelil, 2012).

4

Currently, there are six standards used for inoxydable rebar, namely US:

ASTM A955/A955M - 03b, France: XP A35-014 France, Denmark: National

Standards & Official Admissions DS 13080 & DS 13082, UK: BS6744: 2001,

Finland: SFS - 1259, and Germany and Italy codes. In construction works, the

inoxydable steel is employed for several reasons. Not only it is resistant to corrosion,

but also, it has a high ductility which increases the energy dissipation in cyclic

loading cases. The austenitic type of this steel is investigated by researcher in order

to identify their behavior as reinforcement bar in composite concrete beam. Various

types of inoxydable steel are categorized in regard to thermal treatment and chemical

compositions.

This research investigates the cyclic behaviour of retrofitted columns by RC

jacketing using inoxydable steel. Ductility, energy dissipation capacity, yield and

ultimate load bearing capacity of eight full-scale columns retrofitted with different

configuration of connectors between original column and jacket were studied

experimentally. Numerical studies were performed in order to investigate the effect

of different gravity load on the seismic behavior of the retrofitted columns.

1.2 Problem statem ent and motivation for research

It can be shown that columns are in need of retrofit when one of the following

conditions arises:

1. New structures that may include unsafe columns due to bad workmanship or

due to errors in modeling and design. Such cases, although not very frequent,

have to be dealt with taking into consideration the need to preserve the shape

and size of the column without altering the intended functional use of the

structure and at the same time without compromising to the structural

integrity and safety of the structure.

2. The need to place additional loads on columns due to the change in building

usage, this includes either the permission to add more floors, or the change of

the allowed occupational use of the structure. Such changes are known to

happen, especially in largely populated area.

5

3. Aging of old structures due to deterioration of concrete, corrosion of

reinforcing steel bars or both, which leads to the loss of strength of columns

and the inability to carry design loads. These structures may be of historical

or monumental values and could be considered as part of our heritage, or they

could be ordinary structures that simply cost less to repair and maintain than

to demolish and reconstruct.

4. Occasionally some structures, or part of them, are subjected to accidents,

such as fire or a car collision with one or more of the columns in a car park or

a highway bridge, which leads to reduction of column carrying capacity.

5. Buildings that have not been designed for seismic load or they have been

designed based on older version of current seismic codes.

One popular solution to strengthen RC column is to place jackets around the

structural elements. Jackets have been constructed using steel plates, reinforced

concrete and fibre-reinforced polymer (FRP) composites.

FRP composites and steel plates are basically applied to increase shear

capacity and ductility of column. These methods are very effective in avoiding

columns bond failure with insufficiently lapped of longitudinal reinforcement,

although, they offer little enhancement to the flexural and axial strength of an

element. As well as, in appropriating if there is a requirement of considerable

increase in stiffness. For such condition concrete jacketing has the privilege and can

satisfy demand for increase in axial and flexural strength. Furthermore, in many

countries, where reinforced concrete known as most used material for structures,

engineers prefer the strengthening solution of adding new material such as concrete.

The reason is engineers are more familiar with this type of construction and

availability of local experienced contractors and personnel.

However, one of the beneficial construction practice is placing reinforced

concrete jackets and a number of studies have been presented (Dritsos et al., 1997;

Julio et al., 2003; Julio et al., 2005; Kaliyaperumal & Sengupta, 2014; Vandoros &

Dritsos, 2008) there are many unresolved matters indicating the usage of RC

jacketing. While the main aim of any retrofit method is to increase the structural

capacity of elements, durability of the employed technique is also of great

importance. One of the major concerns for RC jacketing is the corrosion of

6

employed reinforcing rebars. Almost all of past studies have concentrated on the

usage of normal reinforcement (i.e. carbon steel) and less attention has been paid to

inoxydable rebars, which are durable for use in harsh environmental conditions like

piers of bridges and columns constructed in seawater. Inoxydable rebars have higher

yield and ultimate strength and their ductility is often more than normal

reinforcements. Therefore, due to difference in the mechanical properties of

inoxydable rebars compared to normal rebars, obtained results from past studies may

not be applicable for jacketing using inoxydable steel rebars. This implies that, new

studies are required to investigate dynamic behavior of RC columns retrofitted by

inoxydable reinforcement.

In addition, a review of literature shows that, when it comes to RC jacketing,

the load transfer mechanism between the original column and RC jacket has not been

well researched. This issue is of great importance especially for retrofitted columns

that suffer from inadequate lap splice. One more issue when using concrete jacketing

for retrofit is the integrity between the original column and the jacket. An ideal

retrofitted column should have axial force and bending moment capacities similar to

a monolithic element. However, due to slippage between the body of jacket and

original column, retrofitted columns have lower bending moment and axial force

capacities compared to original columns. While research and practice engineers have

suggested different connector to reduce the slippage rate, still new studies for

developing better connectors are needed. Moreover, in this research, new connectors

are introduced to increase the bond between the original column and concrete jacket.

1.3 Objectives of the study

The main aim of this study is to investigate dynamic behavior of RC columns

retrofitted with inoxydable steel jackets. The main aim of this research is to address

the above-mentioned problems through a series of experimental and numerical

studies. The specific objectives of this research are as follow:

7

a) To investigate seismic behavior (i.e. energy dissipation capacity, stiffness

degradation and failure mechanism) of low ductile RC columns with

inadequate overlap length.

b) To evaluate the effectiveness of inoxydable reinforcement jacketing for

seismic retrofit of low ductile RC columns through numerical and

experimental studies.

c) To investigate the load transfer mechanism between original low ductile

column and the surrounding jacket through and experimental studies.

d) To develop new connectors between original low ductile column and the

surrounding jacket and examine their effectiveness through experimental

studies.

1.4 Research Scope

The present study focuses on the retrofitting of concrete columns through

reinforcement jacketing. Experimental works are conducted on eight full scale

columns with the height of 2000mm and cross sectional size of 200mm by 200mm.

The compressive strength of concrete used in this study range from 20MP to 30MPa.

The yield and ultimate stress of employed ribbed reinforcement bars for 8,10 and

20mm sizes are 508 to 533 N/mm and 598 to 700 N/mm2 respectively. The yield and

ultimate stress of inoxydable reinforcement bars used in jackets are 346 and

639N/mm2, respectively; however, the yield and ultimate stress of plain

reinforcement bars used in retrofitted column are 371 and 454N/mm2, respectively.

Plain reinforcement bars were used for the retrofitted columns. For jackets and

foundations ribbed bars were used. In the retrofitted columns, the overlap length of

reinforcement was selected based on the recommendation of British standard.

The cyclic loading applied to columns followed the load protocol suggested

by the FEMA461. The axial force used in combination with the cyclic load amounted

to 100 kN. Inoxydable steel rebars used for jackets were implanted into the

foundation using epoxy glue of Hilty Company. The reinforcement bars used in

jackets were inserted as per recommendation of Hilty Company. For numerical

studies, Ansys software Ver. 16 was employed in this research.

8

1.5 Significant of the research

This study deals with the retrofit of columns. The outcome of this research

can be used to increase the life time of structures and prevent the possibility of

sudden collapse due to seismic actions.

In addition, since this study is devoted to the use of inoxydable rebars for the

purpose of retrofit, the findings of this research is of great importance for countries

like Malaysia in which the environmental condition can easily corrode the normal

reinforcement used for the retrofit of columns. This study also elevates our

knowledge about dynamic behavior of retrofitted columns. The invented connectors

in this study can be also used to improve the seismic behavior of retrofitted columns

with inadequate lap splice. Since the application of inoxydable bars in the retrofit of

columns has not been researched, this study provides new findings for practical

application of inoxydable bar.

1.6 Outline of the Thesis

This thesis consists of six chapters. The organization of this thesis is as

below:

Chapter 1 describes an introduction to the work, describes research objectives

and the scope of work, and explains significance and motivation of this research.

Chapter 2 presents a literature review on the dynamic behavior of retrofitted

structures. The existing retrofit techniques are described in this chapter.

Chapter 3 describes the research methodology which is employed to achieve

the defined objectives. It also describes research design procedure. The details of the

selected retrofitted columns, performed tests and procedure in the numerical analysis

are explained in this chapter.

Chapter 4 presents the obtained results of the proposed retrofit technique for

column based on the experimental tests. The failure mechanism of columns, change

9

in the stiffness and ductility of columns before and after retrofitting are explained in

this chapter.

Chapter 5 describes a series of numerical analysis used to improve our

understanding about dynamic characteristics of retrofitted columns. Calibration of

finite element models are presented in this chapter. Moreover, the effect of different

axial load on the cyclic behavior of retrofitted columns is presented in this chapter.

Chapter 6 summarizes the work of this thesis. The research finding,

contribution of the thesis and the recommendations for future work are also

described in this chapter.

REFERENCES

Aboutaha, R. S. (1994). Seismic retrofit of non-ductile reinforced concrete columns

using rectangular steel jackets. University of Texas at Austin.

Aboutaha, R. S., Engelhardt, M. D., Jirsa, J. O., & Kreger, M. E. (1996). Retrofit of

concrete columns with inadequate lap splices by the use of rectangular steel

jackets. Earthquake Spectra, 12(4), 693-714.

AboutahaI, R. S. (1996). Seismic retrofit of R/C columns using steel jackets. ACI

Special Publication, 160.

Achillopoulou, D., Rousakis, T., & Karabinis, A. (2012). Force transfer between

existing concrete columns with reinforced concrete jackets subjected to axial

loading. Paper presented at the 15th World Conference on Earthquake

Engineering.

Agarwal, B. D., Broutman, L. J., & Chandrashekhara, K. (2006). Analysis and

performance of fiber composites: John Wiley & Sons.

Albanesi, T., Lavorato, D., Nuti, C., & Santini, S. (2008). Pseudo-dynamic tests on

repaired and retrofitted bridge. Paper presented at the Proceedings of The 14th

World Conference on Earthquake Engineering, Beijing, China.

Alih, S., & Khelil, A. (2012). Behavior of inoxydable steel and their performance as

reinforcement bars in concrete beam: Experimental and nonlinear finite element

analysis. Construction and Building Materials, 37, 481-492.

ASSOCIATION, C. S. (2004). Design of concrete structures, Canadian Standard

Association.

BALLINGER, C., MAEDA, T. & HOSHIJIMA, T. (1993). Strengthening of

reinforced concrete chimneys, columns and beams with carbon fiber reinforced

plastics. Special Publication, 138, 233-248.

Bett, B. J., Klingner, R. E., & Jirsa, J. O. (1988). Lateral load response of

strengthened and repaired reinforced concrete columns. ACI Structural Journal,

85(5).

235

Bousias, S., Spathis, A.-L., & Fardis, M. N. (2007). Seismic retrofitting of columns

with lap spliced smooth bars through FRP or concrete jackets. Journal of

Earthquake Engineering, 11(5), 653-674.

Buyukozturk, O., & Au, C. (2005). Effect of fiber orientation and ply mix on FRP-

confined concrete. Paper available online at http://web. mit.

edu/istgroup/ist/documents/orientationPlyMix.

CAMPIONE, G., FOSSETTI, M., GIACCHINO, C. & MINAFo, G. (2014). RC

columns externally strengthened with RC jackets. Materials and Structures, 47,

1715-1728.

Cercone, L., & Korff, J. (1997). Putting the wraps on quakes. Civil Engineering,

67(7), 60.

Chai, Y. H., Priestley, M. N., & Seible, F. (1994). Analytical model for steel-

jacketed RC circular bridge columns. Journal of Structural Engineering, 120(8),

2358-2376.

ChaiI, Y. H., Priestley, M. N., & Seible, F. (1991). Seismic retrofit of circular bridge

columns for enhanced flexural performance. ACI Structural Journal, 88(5).

Chakrabarti, A., Menon, D., & Sengupta, A. K. (2008). Handbook on Seismic

Retrofit of Buildings: Alpha Science International, Limited.

Choi, E., Chung, Y.-S., Park, K., & Jeon, J.-S. (2013). Effect of steel wrapping

jackets on the bond strength of concrete and the lateral performance of circular

RC columns. Engineering Structures, 48, 43-54.

Choi, E., & Kim, M.-C. (2008). A New Steel Jacketing Method for Concrete

Cylinders and Comparison of the Results with a Constitutive Model. International

Journal of Railway, 1(2), 72-81.

Committee, A., Institute, A. C., & Standardization, I. O. f. (2008). Building code

requirements for structural concrete (ACI 318-08) and commentary.

Cramer, S., Covino, B., Bullard, S., Holcomb, G., Russell, J., Nelson, F., . . . Soltesz,

S. (2002). Corrosion prevention and remediation strategies for reinforced

concrete coastal bridges. Cement and Concrete Composites, 24(1), 101-117.

Demers, M. (1995). Determination des parametres influengant le comportement des

colonnes en beton confinees par une enveloppe mince en composite d'avant-

garde.

http://web

236

Deus, J., Freire, L., Montemor, M., & Novoa, X. (2012). The corrosion potential of

stainless steel rebars in concrete: Temperature effect. Corrosion Science, 65, 556

560.

Dritsos, S., Taylor, C., & Vandoros, K. (1997). Seismic strengthening of reinforced

concrete structures by concrete jacketing. Paper presented at the Proceedings of

the 7th International Conference on Structural Faults and Repair.

Dritsos, S., Vandoros, K., & Taylor, C. (1998). Shaking table tests on a retrofitted,

small scale, reinforced concrete model. Paper presented at the Proceedings of the

6th SECED Conference on Seismic Design Practice into the Next Century,

Oxford, UK.

Duarte, R., Castela, A., Neves, R., Freire, L., & Montemor, M. (2014). Corrosion

behavior of stainless steel rebars embedded in concrete: an electrochemical

impedance spectroscopy study. Electrochimica Acta, 124, 218-224.

Emmons, P., & Vaysburd, A. (2000). Concrete Repair at the Threshold of the 21st

Century: Focus on Strengthening of Existing Structures. Special Publication, 185,

121-140.

ENUICA, C., BOB, C., DAN, S., BADEA, C. & GRUIN, A. Solutions for Bond

Improving of Reinforced Concrete Columns Jacketing.

Ersoy, U., Tankut, A. T., & Suleiman, R. (1993). Behavior of jacketed columns. ACI

Structural Journal, 90(3).

Eurocode, E. (1993). 3: Design of steel structures-Part 1.2: General rules-Structural

fire design. Brussels: European Committee for Standardization. DD ENV, 1-2.

Fitzwilliam, J., & Bisby, L. A. (2010). Slenderness effects on circular CFRP

confined reinforced concrete columns. Journal of Composites for Construction,

14(3), 280-288.

Franchi, A., Crespi, P., Bennani, A., & Farinet, M. (2006). Stainless Steel Rebar for

Seismic Applications Advances in Engineering Structures, Mechanics &

Construction (pp. 255-264): Springer.

Freire, L., Carmezim, M., Ferreira, M. a., & Montemor, M. (2010). The passive

behaviour of AISI 316 in alkaline media and the effect of pH: A combined

electrochemical and analytical study. Electrochimica Acta, 55(21), 6174-6181.

Georgiadis, A. S., Sideris, K. K., & Anagnostopoulos, N. S. (2009). Properties of

SCC produced with limestone filler or viscosity modifying admixture. Journal of

materials in civil engineering, 22(4), 352-360.

237

Gomes, A., & Appleton, J. (1998). Repair and strengthening of reinforced concrete

elements under cyclic loading. Paper presented at the 11th European Conference

on Earthquake Engineering.

Gunaslan, S. E., Kara§in, A., & Oncu, M. E. (2014). Properties of FRP Materials for

Strengthening. International Journal of Innovative Science, Engineering &

Technology, 1(9).

HARMON, T. & SLATTERY, K. Advanced composite confinement of concrete.

Advanced composite materials in bridges and structures, 1992. 299-306.

Harries, K., Ric1es, J.M., Sause, R., and Pessiki, S.P.,. (1998a). Seismic Retrofit and

Rehabilitation ofNon-Ductile Reinforced Concrete Columns Using Fi~er

Reinforced Compostie Jackets. Literature Review, Lehigh University Earthquake

Engineering Research Report.

Hexcel-FyfeCo. (1996). Tyfo-S Fibrwrap System. Promotional Package.

Hidalgo, P. A., et al. (2002). "Seismic behavior of squat reinforced concrete shear

walls." Earthquake Spectra 18(2): 287-308.

HOWIE, I. & KARBHARI, V. Effect of materials architecture on strengthening

efficiency of composite wraps for deteriorating columns in the North-East.

Infrastructure: New Materials and Methods of Repair, 1994. ASCE, 199-206.

Institution, B. S. (2004). Eurocode 2: Design of Concrete Structures: Part 1-1:

General Rules and Rules for Buildings: British Standards Institution.

Julio, E. N., & Branco, F. A. (2008). Reinforced concrete jacketing-Interface

influence on cyclic loading response. ACI Structural Journal, 105(4), 471.

Kaliyaperumal, G., & Sengupta, A. K. (2009). Seismic retrofit of columns in

buildings for flexure using concrete jacket. ISET Journal of Earthquake

Technology.

Kaliyaperumal, G., & Sengupta, A. K. (2014). Seismic behaviour of concrete

jacketed columns in buildings. Proceedings of the ICE-Structures and Buildings,

167(9), 534-543.

Kaplan, H., & Yilmaz, S. (2012). Seismic strengthening of reinforced concrete

buildings: INTECH Open Access Publisher.

KARTHIK, M. M. & MANDER, J. B. 2010. Stress-block parameters for unconfined

and confined concrete based on a unified stress-strain model. Journal of

Structural Engineering, 137, 270-273.

238

Kestner, J. T. (1998). Rehabilitation of reinforced concrete columns using fiber

reinforced polymer composite jackets.

Khaloo, A., Javid, Y., & Tazarv, M. (2008). Experimental Study of the Internal and

External (FRP) Confinement Effect on Performance of Compressive Concrete

Members. Paper presented at the 14th World Conference on Earthquake

Engineering (14th WCEE).

Kiousis, P. D., & Whitcomb, B. L. (2007). Study on the Use of Self-consolidating

Concrete for the Repair of the Mead Bridges on I-25: Colorado Department of

Transportation, Research Branch.

LAMPROPOULOS, A. & DRITSOS, S. E. (2011). Modeling of RC columns

strengthened with RC jackets. Earthquake Engineering & Structural Dynamics,

40,1689-1705.

Lavorato, D., & Nuti, C. (2015). Pseudo-dynamic tests on reinforced concrete

bridges repaired and retrofitted after seismic damage. Engineering Structures, 94,

96-112.

Lei, X., Pham, T. M., & Hadi, M. N. (2012). Comparative behaviour of FRP

confined square concrete columns under eccentric loading.

Li, J., Gong, J., & Wang, L. (2009). Seismic behavior of corrosion-damaged

reinforced concrete columns strengthened using combined carbon fiber-

reinforced polymer and steel jacket. Construction and Building Materials, 23(7),

2653-2663.

Li, Y. F., Hwang, J. S., Chen, S. H., & Hsieh, Y. M. (2005). A study of reinforced

concrete bridge columns retrofitted by steel jackets. Journal of the Chinese

Institute of Engineers, 28(2), 319-328.

Lynn, A. C., Moehle, J. P., Mahin, S. A., & Holmes, W. T. (1996). Seismic

evaluation of existing reinforced concrete building columns. Earthquake Spectra,

12(4), 715-739.

MANDER, J. B., PRIESTLEY, M. J. & PARK, R. (1988). Theoretical stress-strain

model for confined concrete. Journal of structural engineering, 114, 1804-1826.

MANUAL, A. U. S. 2000. Ansys. Inc. Modeling, CFX, 11.

Marlapalle, V., Salunke, P., & Gore, N. (2014). Analysis & design of RCC jacketing

for buildings. International Journal of Recent Technology and Engineering, 3, 62

63.

239

McGurn, J. (1998). Stainless steel reinforcing bars in concrete. Paper presented at the

Proceedings of the international conference on corrosion and rehabilitation of

reinforced concrete structures, Orlando.

MERGOS, P. E. & BEYER, K. (2014). Loading protocols for European regions of

low to moderate seismicity. Bulletin of Earthquake Engineering, 12, 2507-2530.

MINAFo, G. (2015). A practical approach for the strength evaluation of RC columns

reinforced with RC jackets. Engineering Structures, 85, 162-169.

NANNI, A., NORRIS, M. & BRADFORD, N. (1993). Lateral confinement of

concrete using FRP reinforcement. Special Publication, 138, 193-210.

Niall, D., Holmes, N., & O'Shea, C. (2014). Active confinement of weakened

concrete columns.

Nosho, K., Stanton, J., & MacRae, G. (1996). Retrofit of rectangular reinforced

concrete columns using Tonen Forca tow sheet carbon fiber wrapping. Report

No. SGEM, 96-92.

Osada, K., Ono, S., Yamaguchi, T., and Ikeda, S. (1996). Seismic Reinforcement of

RC Bridge Peir with Carbon Fiber Sheet. Proceedings of the Japan-USA Bridge

Seminar, Buffalo, NY, October 1996.

Ozcan, O., Binici, B., & Ozcebe, G. (2010). Seismic strengthening of rectangular

reinforced concrete columns using fiber reinforced polymers. Engineering

Structures, 32(4), 964-973.

Ping, G., Elliott, S., Beaudoin, J., & Arsenault, B. (1996). Corrosion resistance of

stainless steel in chloride contaminated concrete. Cement and Concrete Research,

26(8), 1151-1156.

Priestly, M., Seible, F., & Fyfe, E. (1992). Column seismic retrofit using

fiberglass/epoxy jackets. SEQAD Report to Fyfe Associates.

Reinhart, T. J. (1987). Engineered materials handbook: ASM international.

Rodriguez, M., & Park, R. (1994). Seismic load tests on reinforced concrete columns

strengthened by jacketing. ACI Structural Journal, 91(2).

Rodsin, K. (2015). Brittle Shear Failure Prevention of a Non-ductile RC Column

using Glass Fiber Reinforced Polymer (GFRP). Procedia Engineering, 125, 911

917.

Rousakis, T. C., Karabinis, A. I., & Kiousis, P. D. (2007). FRP-confined concrete

members: Axial compression experiments and plasticity modelling. Engineering

Structures, 29(7), 1343-1353.

240

Saadatmanesh, H., Ehsani, M. R., & Jin, L. (1996). Seismic strengthening of circular

bridge pier models with fiber composites. ACI Structural Journal, 93(6).

Saadatmanesh, H., Ehsani, M. R., & Li, M.-W. (1994). Strength and ductility of

concrete columns externally reinforced with fiber composite straps. ACI

Structural Journal, 91(4).

SABU, J. & PAJGADE, P. (2012). Seismic Evaluation of Existing Reinforced

Concrete Building. International Journal of Scientific & Engineering Research, 3,

1-8.

Sadeghian, P., Rahai, A. R., & Ehsani, M. R. (2010). Experimental study of

rectangular RC columns strengthened with CFRP composites under eccentric

loading. Journal of Composites for Construction, 14(4), 443-450.

Saraswathy, V., & Song, H. W. (2005). Performance of galvanized and stainless steel

rebars in concrete under macrocell corrosion conditions. Materials and Corrosion,

56(10), 685-691.

Seible, F., Priestley, M., & Innamorato, D. (1995). Earthquake Retrofit of Bridge

Columns With Continuous Carbon Fiber Jackets. Volume 2. Design Guidelines.

Sezen, H., & Miller, E. A. (2010). Experimental evaluation of axial behavior of

strengthened circular reinforced-concrete columns. Journal of Bridge

Engineering, 16(2), 238-247.

Sideris, K. K. (2007). Mechanical characteristics of self-consolidating concretes

exposed to elevated temperatures. Journal of materials in civil engineering, 19(8),

648-654.

Stoppenhagen, D. R., Jirs, J. O., & Wyllie Jr, L. A. (1995). Seismic repair and

strengthening of a severely damaged concrete frame. ACI Structural Journal,

92(2).

Su, R., & Wang, L. (2012). Axial strengthening of preloaded rectangular concrete

columns by precambered steel plates. Engineering Structures, 38, 42-52.

Tassios, T. (1986). Fundamental mechanisms of force-transfer across reinforced

concrete critical interfaces. Paper presented at the CEB Workshop, West

Germany.

Tassios, T. P., & Vintzeleou, E. N. (1987). Concrete-to-Concrete Friction. Journal of

Structural Engineering.

241

Teng, J., Lu, J., Lam, L., & Xiao, Q. (2011). Numerical simulation of FRP-jacketed

RC columns subjected to cyclic loading Advances in FRP Composites in Civil

Engineering (pp. 820-823): Springer.

Thermou, G., Pantazopoulou, S., & Elnashai, A. (2007). Flexural behavior of brittle

RC members rehabilitated with concrete jacketing. Journal of Structural

Engineering, 133(10), 1373-1384.

TODESCHINI, C. E., BIANCHINI, A. C. & KESLER, C. E. Behavior of concrete

columns reinforced with high strength steels. Journal Proceedings, 1964. 701

716.

Tsonos, A. G. (1999). Lateral load response of strengthened reinforced concrete

beam-to-column joints. ACI Structural Journal, 96, 46-56.

Vandoros, K. (2005). Experimental investigation of the behaviour of columns

strengthened with reinforced concrete jackets under cyclic loads. Doctor

dissertation. Greece: Department of Civil Engineering. University of Patras.

Vandoros, K. G., & Dritsos, S. E. (2006a). Axial preloading effects when reinforced

concrete columns are strengthened by concrete jackets. Progress in Structural

Engineering and Materials, 8(3), 79-92.

Vandoros, K. G., & Dritsos, S. E. (2006b). Interface treatment in shotcrete jacketing

of reinforced concrete columns to improve seismic performance. Structural

Engineering and Mechanics, 23(1), 43-61.

Vandoros, K. G., & Dritsos, S. E. (2008). Concrete jacket construction detail

effectiveness when strengthening RC columns. Construction and Building

Materials, 22(3), 264-276. doi: 10.1016/j.conbuildmat.2006.08.019

Waghmare, S. P. B. (2011). Materials and jacketing technique for retrofitting of

structures. International Journal of Advanced Engineering Research and Studies,

1(1), 15-19.

Walkup, S. L. (1998). Rehabilitation of non-ductile reinforced concrete building

columns using fiber reinforced polymer jackets.

Walraven, J. (1988). Aggregate Interlock and Dowel Action under Monotonic and

Cyclic Loading: Delft University Press.

Wang, Y.-f., & Wu, H.-l. (2010). Size effect of concrete short columns confined with

aramid FRP jackets. Journal of Composites for Construction, 15(4), 535-544.

Wei, Y., & Wu, Y.-F. (2014). Compression behavior of concrete columns confined

by high strength steel wire. Construction and Building Materials, 54, 443-453.

242

WILLAM, K. & WARNKE, E. Constitutive model for the triaxial behavior of

concrete. Proceedings, international association for bridge and structural

engineering, 1975. ISMES, Bergamo, Italy, 1-30.

Xiao, Y., & Wu, H. (2003). Retrofit of reinforced concrete columns using partially

stiffened steel jackets. Journal of Structural Engineering, 129(6), 725-732.

XXsysTechnologies. (1996). Robo-Wrapper - Carbon Fiber Jacketing Technology

for Seismic Retrofit ofFreeway Bridge Columns,. Promotional Package.

Zoghi, M. (2013). The international handbook of FRP composites in civil

engineering: CRC Press.

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