ABSTRACT

COSKUN, HILMI. Construction of SIMCON Retrofitted Reinforced Concrete Columns.

(under the direction of Dr. Michael L. Leming)

There is a growing interest on infrastructure retrofitting due to updated seismic codes

and increased service loads. There may be some economical reasons or preservation needs

to strengthen a structure instead of demolishing it. For strengthening purposes alternatives

include steel jacketing and Fiber Reinforced Plastic (FRP) wrapping. This study focuses on

Slurry Infiltrated Mat Concrete (SIMCON) as an option for strengthening of reinforced

concrete columns.

Before SIMCON is applied routinely for strengthening of a column, however, certain

critical construction and constructibility factors affecting the jacketed column behavior must

be resolved. In this study, the frost durability of SIMCON was examined, factors associated

with the construction of a SIMCON jacket were identified, the influence of these factors on

service load and ultimate state behavior were evaluated, the criticality of these factors was

determined, and general guidelines for the construction or design of SIMCON jackets on

existing columns were developed. In addition, an approximate cost of SIMCON jackets for

existing reinforced concrete columns was developed in order to evaluate the economic

viability of the SIMCON jacket.

SIMCON exhibited satisfactory deicer salt scaling resistance, even without the

presence of entrained air. No significant effect of cracking on scaling was observed.

Several construction aspects of jacketing were studied analytically. Bonding was not

found to be necessary for SIMCON jacketing of a column. The most important factor is the

end connections of a SIMCON jacket for load and moment transfer. Other critical factors

were thickness and strength tolerances of SIMCON jacket.

The construction costs of SIMCON jacket were estimated based on available data.

This and some other strengthening technique cost data showed that SIMCON jacketing is an

economically viable technique.

CONSTRUCTION OF SIMCON RETROFITTED

REINFORCED CONCRETE COLUMNS

by

HILMI COSKUN

A dissertation submitted to the Graduate Faculty ofNorth Carolina State University

in partial fulfillment of therequirements for the Degree of

Doctor of Philosophy

CIVIL ENGINEERING

Raleigh

2002

APPROVED BY

_________________________ _________________________

Dr. Sami Rizkalla Dr. David W. Johnston

_________________________ _________________________

Dr. Amir Mirmiran Dr. Michael L. Leming

Chair of Advisory Committee

ii

BIOGRAPHY

Hilmi Coskun was born in Eskisehir, Turkey in 1967. He got his elementary and

secondary education in Eskisehir and graduated from Demiryol Meslek Lisesi, (Railways

High School) in 1984. He received his Bachelor of Science degree in Civil Engineering from

Anadolu University in September of 1988.

Hilmi worked as a civil engineer in TCDD (Turkish State Railways) from 1988 to

1993. He won a scholarship in 1993 from the Turkish Government to pursue his Masters

and Ph.D. degrees from universities abroad. He joined the masters degree program in the

Civil Engineering Department at Old Dominion University, Norfolk, Virginia, USA in 1995.

There he studied the flexural behavior of thermoplastic beams under the direction of Dr. Zia

Razzaq, and received his M.S. degree in December 1997.

Hilmi started his Ph.D. degree program at North Carolina State University, Raleigh,

North Carolina, USA in January of 1998. He conducted his studies under the directions of

Dr. Michael L. Leming and completed the doctoral studies in the Summer of 2002.

iii

ACKNOWLEDGMENTS

My special thanks are extended to Dr. Leming for his guidance throughout my

studies. Furthermore, I want to thank Dr. Johnston and Dr. Rizkalla for their helps and

supports. I also would like to thank Dr. Krstulovic and Dr. Mirmiran for their helpful

suggestions.

I am grateful to Mustafa Kemal University, Turkey, which provided the financial

support for my studies. Support provided by NCSU Civil Engineering Department during

my last year of studies is gratefully acknowledged. I appreciate help of Mr. Jerry Atkinson

from the Constructed Facilities Laboratory during my experiments.

Last but not least, I would like to thank my wife, Meltem Coskun. Certainly I have

been gifted with her support and patience. I want to thank my daughters Ipek Pinar and Ezgi

Zeynep. Their smiles and hugs gave me happiness and encouraged me on my work. I would

also like to thank my family who send their prayers.

iv

TABLE OF CONTENTS

LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x

LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

LIST OF SYMBOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii

I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

II. LITERATURE REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1 Fiber Reinforced Concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2 SIMCON Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.1 Mechanical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.2 Durability Concerns with HPFRCC . . . . . . . . . . . . . . . . . . . . . 12

2.2.3 Drying Shrinkage of SIFCON . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.3 Slurry Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.3.1 Slurry Mixture Proportioning . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.3.2 Slurry Infiltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.4 SIMCON Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

III. SCOPE OF THE STUDY AND RESEARCH METHODOLOGY . . . . . . . . 26

3.1 Scope of the Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.2 Research Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.2.1 Investigation of Deicer Salt Scaling Resistance of SIMCON . 28

3.2.2 Identification of Factors Related to Design and Construction . 29

v

3.2.2.1 Methodology of Identification of Factors . . . . . . . . . . 29

3.2.2.2 Identification of Factors Affecting the Behavior of

SIMCON Jacketed Columns . . . . . . . . . . . . . . . . . . . . 30

3.2.3 Cost Analysis of SIMCON Jacketing . . . . . . . . . . . . . . . . . . . 34

IV. DURABILITY PERFORMANCE OF SIMCON . . . . . . . . . . . . . . . . . . . . . . 36

4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4.2 Experimental Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4.2.1 Main Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

4.2.2 Mixture Used in the Experimental Study . . . . . . . . . . . . . . . . . 39

4.2.3 SIMCON Specimen Preparation and Testing . . . . . . . . . . . . . 42

4.2.4 Air Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

4.2.4.1 Test Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

4.2.4.2 Results of Microscopic Examination . . . . . . . . . . . . . . 49

4.3 Test Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.3.1 Scaling Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.3.2 Effects of Cracking on Frost Durability . . . . . . . . . . . . . . . . . . 51

4.3.3 Corrosion of Fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

V. ANALYTICAL EVALUATION OF DESIGN AND CONSTRUCTION

FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.2 Identification of Factors to Be Evaluated . . . . . . . . . . . . . . . . . . . . . . . 58

vi

5.2.1 Identification of Design Factors with Significant Construction

Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.2.1.1 Bond Between SIMCON and Reinforced Concrete

Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.2.1.2 SIMCON End Connections . . . . . . . . . . . . . . . . . . . . . 59

5.2.1.3 Removal of Load on Existing Reinforced Concrete

Column Prior to Jacketing . . . . . . . . . . . . . . . . . . . . . . 60

5.2.1.4 Thin Wall Buckling of SIMCON Jacket . . . . . . . . . . . 61

5.2.2 Identification of Factors Occurring During Construction . . . . 62

5.2.2.1 Routine Variations in SIMCON Strength . . . . . . . . . . 62

5.2.2.2 Routine Variations in SIMCON Jacket Thickness . . . 63

5.2.2.3 Non-Concentric Placement of the SIMCON Jacket

During Construction (Centering) . . . . . . . . . . . . . . . . . 63

5.2.2.4 Location and Strength of Fiber Mat Seams . . . . . . . . . 64

5.3 Analytical Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

5.3.1 Analytical Methods Used For Evaluation of Factors . . . . . . . . 65

5.3.2 Determination of Criticality of the Factors . . . . . . . . . . . . . . . 66

5.3.3 Cross Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

5.3.4 Material Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

5.3.5 Assumptions for Structural Modeling . . . . . . . . . . . . . . . . . . . 78

5.4 Overview of Analytical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

5.4.1 Moment-Curvature Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 79

vii

5.4.2 Application of Moment-Curvature Analysis to Available

Test Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

5.4.3 Column Axial Load-Moment Interaction Diagrams . . . . . . . . 87

5.4.4 The Effects of Tolerances on Reinforced Concrete Section . . 89

5.5 Analysis of the Behavior of SIMCON Jacketed Reinforced

Concrete Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.6 Results of Evaluation of Selected Construction Factors . . . . . . . . . . 102

5.6.1 Bond Between SIMCON and Reinforced Concrete Column . 102

5.6.2 Removal of Load on Existing Reinforced Concrete Column

Prior to Jacketing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

5.6.3 The Effects of Routine Strength Variations of SIMCON . . . 118

5.6.4 The Effect of Routine Variations in SIMCON Thickness . . . 123

5.6.5 The Effect of Displacement of the SIMCON Jacket During

Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

5.6.6 Effects of SIMCON Seams . . . . . . . . . . . . . . . . . . . . . . . . . . 134

5.6.7 Thin Wall SIMCON Jacket . . . . . . . . . . . . . . . . . . . . . . . . . . 140

5.6.8 SIMCON Jacket End Connections . . . . . . . . . . . . . . . . . . . . . 144

5.7 Summary of Analytical Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 147

5.7.1 Summary of Analytical Evaluation of Selected Factors . . . . 147

5.7.2 Modification of Strength Reduction Factor for SIMCON

Jacketed Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

5.8 Conclusions and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . 152

viii

VI. COMPARISON OF ALTERNATIVE STRENGTHENING TECHNIQUES

AND COST ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

6.2 Confinement by Jackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

6.2.1 Steel Jackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

6.2.2 FRP Jackets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

6.2.3 Reinforced Concrete Jackets . . . . . . . . . . . . . . . . . . . . . . . . . . 163

6.2.4 Demolishing the Existing Reinforced Concrete Column and

Building a New Reinforced Concrete Column . . . . . . . . . . . 165

6.2.5 Adding a Steel Tube or Column Next to the Existing Member 166

6.3 Cost Analysis of SIMCON Jacketed Columns . . . . . . . . . . . . . . . . . . 166

6.3.1 Assumptions in Estimating Project Management Costs . . . . . 167

6.3.2 Work Breakdown Structure of SIMCON Jacketed Reinforced

Concrete Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

6.3.3 Cost Analysis of SIMCON Jacketed Reinforced Concrete

Column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

6.3.4 Cost Data of Alternative Strengthening Techniques . . . . . . . 180

6.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

VII. CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . 183

7.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

7.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

ix

APPENDIX A SIMCON MATERIAL PROPERTIES . . . . . . . . . . . . . . . . . . 198

A.1 SIMCON Tensile Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

A.2 SIMCON Compressive Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

APPENDIX B SIMCON SCALING TEST SPECIMENS . . . . . . . . . . . . . . . 202

APPENDIX C RESULTS OF EVALUATION OF DESIGN AND

CONSTRUCTION FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . 210

x

LIST OF TABLES

2.1 Slurry mixture proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.1 Research methodology matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.1 Scaling test variables and SIMCON specimens’ properties . . . . . . . . . . . . . . 40

4.2 Slurry mixture proportions by mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.3 Compression strength of slurries with and without air entrainment . . . . . . . . 45

5.1 Cross section configurations used in the analysis . . . . . . . . . . . . . . . . . . . . . . 76

5.2 The effects of tolerances for reinforced concrete column . . . . . . . . . . . . . . . . 92

5.3 Statistical evaluation of analytical results . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

6.1 Crew labor hours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

6.2 Equipment costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

6.3 Slurry material costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

6.4 Material costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

6.5 SIMCON jacket costs for the retrofit of a single reinforced concrete column 179

6.6 The likely high cost for SIMCON jacketing of a single reinforced

concrete column . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

A.1 Average values of SIMCON tensile tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

A.2 Specific values to be used in equations for predicting injected SIMCON

specimens’ compression stress-strain response . . . . . . . . . . . . . . . . . . . . . . . 200

C.1 The effect of reinforcement placement on maximum moment capacities

of reinforced concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

xi

C.2 The effect of reinforcement placement on axial load capacities of reinforced

concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

C.3 The effect of routine variations in concrete strength on maximum moment

capacities of reinforced concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

C.4 The effect of routine variations in concrete strength on axial load capacities

of reinforced concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

C.5 The effect of dimensional tolerances of concrete on maximum moment

capacities of reinforced concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

C.6 The effect of dimensional tolerances of concrete on axial load capacities

of reinforced concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

C.7 The increase in maximum moment capacities of reinforced concrete

sections provided by the SIMCON jacket . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

C.8 The increase in axial load capacities of reinforced concrete sections provided

by the SIMCON jacket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

C.9 The effect of bonding of SIMCON jacket in maximum moment capacities . . 219

C.10 The effect of existing load on maximum moment capacities . . . . . . . . . . . . . 220

C.11 The effect of existing load on axial load capacities . . . . . . . . . . . . . . . . . . . . . 223

C.12 The effect of routine strength variations of SIMCON on maximum

moment capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

C.13 The effect of routine strength variations of SIMCON on axial load capacities 228

C.14 The effect of routine thickness variations of SIMCON on maximum

moment capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

xii

C.15 The effect of routine thickness variations of SIMCON on axial load

capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

C.16 The effect of non-concentric placement of SIMCON during construction

on maximum moment capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237

C.17 The effect of non-concentric placement of SIMCON during construction

on axial load capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

C.18 The effect of reduced strength SIMCON seams and seam locations

on maximum moment capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244

C.19 The effect of reduced strength SIMCON seams and seam locations

on axial load capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

xiii

LIST OF FIGURES

2.1 Comparison of load-deflection curves of SIFCON, ordinary FRC with 2% steel

fibers, and the plain matrix loaded in three-point bending (Naaman, 1992) . . 5

2.2 SIMCON mat cut from a roll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 Load-deflection behavior of SIFCON compared to SIMCON loaded in

three-point bending (Hackman, 1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.4 SIMCON mat roll as delivered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.5 Concrete surface decay in the form of scaling in the presence of deicing

chemicals (ACI 201, 1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.6 Drying shrinkage of SIFCON and plain, unreinforced slurry (Balaguru and

Shah, 1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.7 Ultimate compressive stress versus water/(cement+fly ash) ratios

(Mondragon, 1987) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.8 Ultimate compressive stress at 30 day versus fly ash/(cement+fly ash) ratios

(Mondragon, 1987) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.9 (a) Marsh flow cone and (b) plate cohesion meter (Marrs and Bartos, 1996) 22

2.10 Flexural behavior of composite slabs with SIMCON tensile layer

(Bayasi, 1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.11 Experimental moment-curvature diagram of reinforced concrete-SIMCON

composite beams (Krstulovic, 1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.1 SIMCON specimen for deicing salt scaling test . . . . . . . . . . . . . . . . . . . . . . . 43

xiv

4.2 Time-temperature graph of freezing environment . . . . . . . . . . . . . . . . . . . . . . 44

4.3 Slurry cube cuts for microscopical examination of the air void system . . . . . 47

4.4 Entrained air bubbles in hardened slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.5 Rust stains on the side surface of specimen A13CR-9 . . . . . . . . . . . . . . . . . . . 54

4.6 0.7 inch (18 mm) deep cut from specimen A13CR-9 . . . . . . . . . . . . . . . . . . . . 55

5.1 Definitions of Pn,max and Mo,max . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

5.2 Cross sections used in analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

5.3 Reinforcement steel stress-strain relationship . . . . . . . . . . . . . . . . . . . . . . . . . 73

5.4 Concrete stress-strain relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

5.5 SIMCON stress-strain relationship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

5.6 Curved beam-column and curvature, n = g / d . . . . . . . . . . . . . . . . . . . . . . . . 80

5.7 Reinforced concrete beam-column cross section, strains and internal forces . 82

5.8 Comparison of experimental and analytical moment-curvature diagrams of

reinforced concrete-SIMCON composite beams (Krstulovic, 1997) . . . . . . . . 85

5.9 Calculation of axial load-moment values for a SIMCON jacketed,

reinforced concrete column section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

5.10 Perfect bond between reinforced concrete and SIMCON . . . . . . . . . . . . . . . . 94

5.11 Perfectly bonded section strains and internal forces . . . . . . . . . . . . . . . . . . . . 96

5.12 Reinforced concrete section capacities are compared to perfectly bonded

SIMCON jacketed section capacities based on cross-section type . . . . . . . . . 98

5.13 Axial load-moment interaction diagram: square column . . . . . . . . . . . . . . . . 100

5.14 Axial load-moment interaction diagram: circular column . . . . . . . . . . . . . . . 101

xv

5.15 Axial load capacity ratios of SIMCON jacketed sections to reinforced

concrete sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

5.16 No bond between reinforced concrete and SIMCON . . . . . . . . . . . . . . . . . . 104

5.17 Strains and internal forces for non-composite SIMCON jacketed

reinforced concrete section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

5.18 Superposed moment-curvature of unbonded section . . . . . . . . . . . . . . . . . . . 107

5.19 Unbonded and perfectly bonded cases of square section . . . . . . . . . . . . . . . . 108

5.20 Unbonded and perfectly bonded cases of circular section . . . . . . . . . . . . . . . 109

5.21 Maximum moment ratios of unbonded sections to those of perfectly bonded

sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

5.22 Moment-curvature of square section with initial strain of 0.1% . . . . . . . . . . 116

5.23 Moment-curvature of circular section with initial strain of 0.1% . . . . . . . . . 117

5.24 Effects of initial existing strain on maximum moments . . . . . . . . . . . . . . . . 119

5.25 Effects of initial strain on axial load capacity ratios . . . . . . . . . . . . . . . . . . . 120

5.26 Effects of SIMCON routine strength variations on maximum moments . . . . 122

5.27 Effects of SIMCON routine strength variations on axial load capacity ratios 124

5.28 Effects of SIMCON thickness variations on maximum moments . . . . . . . . . 126

5.29 Effects of routine variations in SIMCON thickness on axial load capacity

ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

5.30 Non-concentrically placed SIMCON jacket around reinforced

concrete member . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

5.31 Effects of non-concentric placement of SIMCON on maximum moments . . 132

xvi

5.32 Effects of non-concentric placement of SIMCON on axial load capacity

ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

5.33 Fiber mat seam locations on a SIMCON jacketed column . . . . . . . . . . . . . . 135

5.34 Analyzed fiber mat seam locations on a SIMCON jacketed column when

SIMCON is placed longitudinally . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

5.35 Effects of SIMCON seams on maximum moments . . . . . . . . . . . . . . . . . . . . 138

5.36 Effects of SIMCON seams on axial load capacity ratios . . . . . . . . . . . . . . . . 139

5.37 Thin wall circular SIMCON tube local buckling critical stress . . . . . . . . . . . 142

5.38 Thin wall square SIMCON tube local buckling critical stress . . . . . . . . . . . . 143

5.39 Epoxy grouted gap between SIMCON jacket pedestal and slab . . . . . . . . . . 146

6.1 Column retrofit to increase confinement with steel hoops (Xanthakos, 1996) 158

6.2 Column retrofit using steel plate encasement (Xanthakos, 1996) . . . . . . . . . . 159

6.3 The REPLARK method for polymer composite wrapping of

columns (Hollaway and Head, 2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

6.4 Xxsys Technologies for polymer composite wrapping of columns

(Hollaway and Head, 2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

6.5 Strengthening a column with reinforced concrete jacket (Xanthakos, 1996) . 164

B.1 Specimen A11NC-3 after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . . 202

B.2 Specimen A12CR-6 after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . . . 203

B.3 Specimen A13CR-9 after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . . 204

B.4 Specimen A14NC-10 after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . 205

B.5 Specimen N21CR-5a after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . 206

xvii

B.6 Specimen N22NC-6a after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . 207

B.7 Specimen N23CR-7a after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . 208

B.8 Specimen N24NC-8a after scaling resistance test . . . . . . . . . . . . . . . . . . . . . . 209

xviii

LIST OF SYMBOLS

Abbreviations

ACI American Concrete Institute

ASCE American Society of Civil Engineers

ASTM American Society for Testing and Materials

EPA Environmental Protection Agency

FRC Fiber Reinforced Concrete

FRP Fiber Reinforced Polymer

HPFRCC High Performance Fiber Reinforced Cement Concrete

HRWRA High Range Water Reducing Admixture

ksf kips per square foot

ksi kips per square inch

kPa kilo Pascal

mm millimeter

MPa Mega Pascal

n.a. neutral axis

OSHA Occupational Safety and Health Administration

psf pounds per square foot

psi pounds per square inch

r.c. reinforced concrete

R.H. relative humidity

SIFCON Slurry Infiltrated Fiber Concrete

xix

SIMCON Slurry Infiltrated Fiber Mat Concrete

Nomenclature

A area

As area of reinforcement

b width of square cross section

C compressive force

CC concrete compressive force

CR reinforcement compressive force

CSIMCON SIMCON compressive force

D diameter of circular cross section

dc distance of concrete element from the neutral axis

ds distance of reinforcement from the neutral axis

dSIMCON distance of SIMCON element from the neutral axis

Es modulus of elasticity of reinforcement (Young’s modulus)

Esh strain-hardening modulus

e eccentricity of axial load at end of column

F degree Fahrenheit

fy specified yield strength of reinforcement

fc calculated stress in concrete

fct calculated tensile stress in concrete

fc! specified compressive strength of concrete

xx

fs calculated stress in reinforcement

fSIMCON calculated stress in SIMCON

fu ultimate stress

h full depth of square cross section

I moment of inertia

l height of column

M moment

MU ultimate moment

MCC Moment of concrete compressive force

MCR Moment of reinforcement compressive force

MCSIMCON Moment of SIMCON compressive force

MTC Moment of concrete tensile force

MTR Moment of reinforcement tensile force

MTSIMCON Moment of SIMCON tensile force

P nominal axial load

PU ultimate axial load

R radius of curvature

T tensile force

TC concrete tensile force

TR reinforcement tensile force

TSIMCON SIMCON tensile force

t thickness

xxi

Vf volume of fibers

xt distance from extreme tension fiber of section to neutral axis

x! distance from extreme compression fiber of section to neutral axis

g unit strain

gc concrete compressive strain

gsh strain at onset of strain hardening

gy yield strain

F calculated stress

D ratio of reinforcement to concrete area

N strength reduction factor

n curvature

CHAPTER I

INTRODUCTION

1.1 OVERVIEW

A research program directed by the National Science Foundation [1995] stated that

due to aging, overexposure, and other factors, many of the civil infrastructure systems, which

constitute a major portion of U.S. national wealth, are rapidly deteriorating as a result of

environmental factors and fatigue and are becoming more vulnerable to catastrophic failure.

The report calls for the development of novel, cost effective methods for infrastructural

repair and retrofit as an essential factor in economical well-being and sustainable

development (NSF 95-52, 1995).

As the number of civil infrastructure systems increases worldwide, the number of

deteriorated buildings and structures also increases. Complete replacement is likely to be an

increasing financial burden and might certainly be a waste of natural resources if upgrading

or strengthening is a viable alternative (Hollaway & Leeming, 1999).

Many reinforced concrete buildings and structures need repair or strengthening to

increase their load carrying capacities or enhance ductility under seismic loading (Naaman

& Reinhardt, 1995; Hollaway & Leeming, 1999). As an example, bridge piers designed

using currently obsolete criteria may need to be upgraded to meet existing requirements.

2

Other factors, such as inadequate transverse confinement or flaws in structural design may

also contribute to structural deficiency. Additionally, a structure may need to be upgraded

to limit deflections or to control cracking due to changes in service conditions. Moreover,

a column may need to be strengthened to support one or more added floors (Newman, 2001).

Strengthening may be required due to changes in use or chosen to extend useful life

while minimizing capital outlay. In these situations, strengthening can be advantageous

compared to (a) demolishing the structure or member and constructing a new one, or (b)

restricting use, limiting imposed loads, and continuously monitoring the structure.

Strengthening of reinforced concrete structures will typically include column

strengthening since the failure of a column has serious consequences for structural stability

(ACI 318, 2002). Alternatives for column strengthening may include:

a) Section enlargement,

b) Steel wrapping,

c) FRP wrapping, and

d) Wrapping with High Performance Fiber Reinforced Cement Composites

(HPFRCC).

1.2 PROBLEM STATEMENT

Slurry Infiltrated Mat Concrete (SIMCON) is one type of HPFRCC which can be

used to improve both load carrying capacity and ductility of reinforced concrete columns.

However, certain critical construction and constructibility factors affecting the SIMCON

jacketed column behavior, including the frost durability of SIMCON, must be resolved

3

before this technology can be applied routinely. Consequently, the goal of this research was

to identify factors associated with the construction of a SIMCON jacket, evaluate the

influence of these factors on service load and ultimate state behavior, determine which of

these factors are critical to the performance of the SIMCON jacket, and develop general

guidelines for the construction or design of SIMCON jackets on existing columns. In

addition, an approximate cost of SIMCON jackets for existing reinforced concrete columns

was developed in order to compare with approximate costs of alternative strengthening

techniques.

4

CHAPTER II

LITERATURE REVIEW

2.1 FIBER REINFORCED CONCRETES

Fiber reinforced concrete (FRC) has been used since the 1960's (ACI 544.1, 1996),

although use was generally limited to warehouse floor or pavement overlays. Steel, glass,

carbon, and polymers have been used commercially as fibers in concrete (ACI 544.1, 1996).

These fibers are produced in many shapes and sizes and are added to concrete in several

ways. The fiber volume in typical, commercially available fiber reinforced concrete usually

varies between 2% to 4%. Despite the fact that FRC is used for a variety of applications such

as tunnel linings, hydraulic structures, and explosion resistant structures (ACI 544.3, 1993),

the lack of design guidelines and mixing problems in the field have limited their use in

structural applications.

High Performance Fiber Reinforced Cement Composites (HPFRCC) were developed

in the 1990's to improve performance characteristics of fiber reinforced concrete (Naaman

and Reinhardt, 1995). In a special HPFRCC application termed Slurry Infiltrated Fiber

Concrete (SIFCON), steel fibers are placed inside a mold and then infiltrated by a high

strength, cementitious slurry. Although SIFCON can achieve higher strength and energy

absorption values under compression than plain concrete (Figure 2.1), this requires a

relatively large amount of fibers, about 12% to 15% (Hackman, et al, 1992), which is very

5

Figure 2.1 Comparison of load-deflection curves of SIFCON,ordinary FRC with 2% steel fibers, and the plainmatrix loaded in three-point bending (Naaman,1992)

6

difficult to achieve outside the laboratory. Providing the fibers as a mat (Figure 2.2), which

is then infiltrated by a high strength slurry, a new type of HPFRCC, called Slurry Infiltrated

Mat Concrete (SIMCON) can be produced.

Basic performance parameters given by Bartos [1992] for ordinary fiber reinforced

concrete are also applicable for HPFRCCs including SIMCON. Bartos identified the

parameters for fresh FRC as mobility or flowability, compactability, surface finishability,

retention of workability, and density. Briefly, hardened FRC parameters are strength,

toughness, deformation and dimensional stability, density, permeability, heat retention, and

electrical resistance, surface appearance and ability to accept surface treatments, durability.

With SIMCON, the same strength and energy absorption capacity can be achieved

as with SIFCON at a lower fiber volume (Figure 2.3). SIMCON also has other advantages.

Stainless steel is used to form the fiber mat, so little or no corrosion will take place. By

having the steel fibers in the form of a mat (Figure 2.4), placement and handling on a

construction site are considerably easier (Krstulovic and Al-Shannag, 1999b). The main

disadvantage is the initial cost because stainless steel is expensive. However, this initial cost

can be justified by increased service life due to very little corrosion and the utilization of a

lower volume of fibers. With SIMCON, 3% to 5% fiber volume can easily be attained. The

ratio of fiber length to fiber diameter is called the fiber aspect ratio. The higher the fiber

aspect ratio, the finer the cracks in FRC. The fiber aspect ratio can be as high as 400 for

SIMCON, about four times that of conventional fiber reinforced concrete (Hackman, et al,

1992).

Limited test data on ordinary steel fiber reinforced concrete shows that steel fibers

7

Figure 2.2 SIMCON mat cut from a roll

8

• • " • • 0

• ~ • -• - ~ • • % • • 0

f." • • • • -. ~ • -• e ~ • 0

.Ii • e • • -->-;)1 •

" ~ • • 0 ~

~~ • :5 N

~ I

~ .• : a - ~ • c v • • 0 c

~ ~El · -• ~ • ~

"x • ~ - -~

~ • " , ~. 0 • • -.li . ~ • ~ • !!,o: -• jj U • 0 • ~-• II .!! c • • Ii • -• >"' " -• c S~ .\ . 0

: ZUl 0 •• oJ.!

- • ~ ~l!l / ~.: " .. _B 0 'Ii ]f .. en (/} 0 • - -• N • " • I • 0 •

~ l • ~., - g ~

" ~ 0 l • • - .. • - ~ • S • 1 • 0 • • •

....... ", .. - 0 >' • 0 ~ - - ~ " 0

I I II I II 00

~ 8 ~ ~ ~ ~ § ~ 0 0

~ " • , • " " --(N 8vv·v- QI t ) q I 'PI!Ol Ii?JnlGl::I

9

Figure 2.4 SIMCON fiber mat roll as delivered

10

in cracked concrete may become subject to corrosion (ACI 544.1R, 1996). Fibers used in

SIMCON are stainless steel fibers directly shaped from molten metal using a chilled wheel

(Hackman, et al, 1992). Using stainless steel fibers should help to minimize the corrosion

of fibers in service compared to other ferrous based fibers.

2.2 SIMCON MATERIAL PROPERTIES

Material properties of HPFRCCs include the behavior under compression and

tension. The primary concerns associated with HPFRCCs’ long-term performance are frost

durability, creep and shrinkage, and changes in the mechanical properties under load.

2.2.1 Mechanical Properties

Material properties of SIMCON under compression, tension and flexural loading

have been investigated by several researchers. Beams made of SIMCON and SIFCON were

tested under flexural loading by Hackman, et al [1992]. SIMCON beams with 5.7% fiber

volume achieved about the same flexural capacity as SIFCON beams with 14% fiber volume

(Figure 2.3). This effectiveness of SIMCON was attributed to using longer (9.5 inch [240

mm]) fibers in mat compared to the shorter (1 inch [25 mm]) SIFCON fibers.

The size and pattern of cracks are also different between ordinary reinforced concrete,

SIFCON and SIMCON. The cracks in ordinary reinforced concrete and SIFCON are usually

large and connected. However, the cracks in SIMCON are small in width (hairline) and

disconnected. The crack density in SIMCON is greater than in both reinforced concrete and

SIFCON (Krstulovic, et al, 1995a).

11

The tensile behavior of SIMCON was examined by Krstulovic, et al [1995a].

SIMCON with a fiber volume of 5% reached 2300 pounds per square inch (psi) (15.9 MPa)

at 1.1% of strain in direct tension tests. Krstulovic [1996] also investigated SIMCON under

compression and shear. Under compression, SIMCON with a 5% fiber volume reached

11000 psi (75.8 MPa). Based on these investigations, Krstulovic [1996] developed models

for SIMCON under tension and compression. He noted that SIMCON has a unique potential

for use in repair and retrofit of existing structures. The material properties of SIMCON are

given in Appendix A.

The effects of fiber orientation on SIMCON compressive strength were investigated

by Krstulovic, et al [1999b]. The test results showed no difference between compressive

strengths of specimens with different fiber orientations. This behavior is opposite to the

behavior observed with other fiber reinforced concretes, such as SIFCON behavior under

compression. The compressive strengths of SIFCON and conventional FRC are lower when

fibers are aligned transversely to the load than when the fibers are aligned parallel to the load

(Balaguru and Shah, 1992). The apparent insensitivity of compressive strength of SIMCON

to the fiber orientation was explained by two factors;

a) the scatter in the angle of fiber orientation within the mat and,

b) the longer length of fibers in the mat compared to the length of fibers used in

SIFCON or ordinary fiber concrete.

SIFCON tensile strength was shown to be sensitive to fiber orientation (Mier et al,

1992). Mier found that the SIFCON tensile strength was higher when fibers were aligned

parallel to load. No data is available on the fiber orientation effect on SIMCON tensile

12

strength. Although some fiber orientation effect is expected, that effect may not be as

pronounced as in SIFCON because of the fiber mat characteristics.

2.2.2 Durability Concerns with HPFRCC

Durability can be defined as the ability of a material, or a structure made of this

material, to remain operationally suitable over the design life of the material or structure.

The American Concrete Institute (ACI) provides many well established guidelines related

to concrete durability. ACI 201 [1992] discusses several important causes of concrete

deterioration. When concrete is exposed to freeze-thaw cycles in the presence of deicing

chemicals, the concrete may exhibit surface distress in the form of scaling or pitting as shown

in Figure 2.5. Concrete which has satisfactory resistance to rapid freezing and thawing may

still exhibit scaling.

Mehta [1993] lists the negative effects of deicing salts on concrete as: “(1) an

increase in the degree of saturation of concrete due to the hygroscopic character of salts;

(2) an increase in the disruptive effect when the supercooled water in pores eventually

freezes; (3) the development of differential stresses caused by layer-by-layer freezing of

concrete due to salt concentration gradients; (4) temperature shock as a result of dry

application of deicing salts on concrete covered with snow and ice; and (5) crystal growth

in supersaturated solutions in pores.”

Lankard [2001] concludes that scaling is often a problem because strength criteria is

relied on more than w/c ratio in residential construction. Lankard gives examples of types

of scaling deterioration and provides guidance for the scaling resistance of concrete,

13

Figure 2.5 Concrete surface decay in the form of scalingin the presence of deicing chemicals (ACI201, 1992)

14

emphasizing the importance of w/c ratio. He also recognizes the role of aggregate and

curing on scaling resistance of concrete.

A report published by ACI Committee 544 [1996] gives examples of applications of

fiber reinforced concrete. According to ACI 544, steel fiber reinforced concrete, exposed to

deicing salt, showed minimum corrosion of fibers and no adverse effects. It is reported that

the fibers on the surface showed minimum corrosion, however, the fibers in the interior

remained mostly intact.

2.2.3 Drying Shrinkage of SIFCON

One of the primary concerns associated with HPFRCCs’ long-term performance is

drying shrinkage behavior. No experimental data was found in the published literature

examining the creep or shrinkage behavior of SIMCON. However, limited test data on

ordinary steel FRC indicate that the presence of fibers reduces the shrinkage strains

(Balaguru and Shah [1992]). Shrinkage strains obtained using cement paste and melt extract

steel fibers, the same type of fibers used in SIMCON mats, were about 50% of the strains

obtained for cement paste at 500 days. According to Balaguru, the drying shrinkage strains

of SIFCON vary from 0.0002 to 0.0005 as shown in Figure 2.6. It was shown that the

shrinkage of SIFCON stops after about 28 days, while the shrinkage of cement paste typically

continues even after 160 days. The magnitude of SIFCON shrinkage strain is slightly lower

than that of typical normal-weight concrete. The addition of sand to the SIFCON matrix

reduces shrinkage considerably (Balaguru and Shah [1992]).

15

Figure 2.6 Drying shrinkage of SIFCON and plain,unreinforced slurry (Balaguru and Shah, 1992)

16

2.3 SLURRY PROPERTIES

SIMCON and SIFCON are composite materials since they consist of fibers and a

matrix. Composed of cementitious material placed as slurry, a very high volume of fibers

is used to produce SIMCON. Therefore, the slurry must have certain characteristics,

including high flowability for good infiltration, typically obtained by using a High Range

Water Reducing Admixture (HRWRA), a small maximum size aggregate, usually sand sized

or smaller. In addition, a high strength obtained by using a low water/cementitious materials

(w/cm) ratio and silica fume, and a high paste are common.

2.3.1 Slurry Mixture Proportioning

Silica fume is frequently used in the SIMCON slurry to improve strength. It is often

used in much greater quantities than in conventional concrete. Table 2.1, which shows the

slurry mixture proportions used in several studies, indicates silica fume contents of 10% to

15% are routine, in excess of the limit recommended in ACI 318 (2002) to control scaling

for exposure to deicer salts. Using silica fume, especially in these quantities, requires a

HRWRA in order to provide a highly fluid slurry, to ensure better infiltration into the fiber

mat.

Similar to ordinary concrete mixtures, the water to cement, or water to cementitious

materials ratio (w/cm), is a critical factor in the compressive strength of the slurry. If the

w/cm decreases, the compressive strength increases (Figure 2.7), but flowability of the

mixture may be decreased (Mondragon, 1987). Mondragon also found that increasing the

amount of cement in the cementitious materials increases the compressive strength (Figure

Table 2.1 Slurry mixture proportions used by researchers (amounts are by mass)

17

Sand W/CM S/CM HRWRA

fc!

ksi (MPa)

Mineral Admixtures

(by mass of cement) Reference

#250 0.31 0.6 4 16.5 (114) Microsilica§ (30%) Krstulovic [1999b]

#250 0.31 0.6 3 NR Solid Microsilica (4.5%) Krstulovic [1995]

#250 0.46 0.6 1.5 NR Solid Microsilica (4%) Krstulovic [1999a]

#250 0.31 0.6 4.5 11.8 (81) Microsilica§ (30%) "

#50-70 0.30 0.6 4 NR Microsilica§ (30%) Naaman and Reinhardt [1995]

0 0.35 0 3 NR 0 "

C 109 0.36 1.0 3 NR 0 "

C 109 0.40 1.5 3 NR 0 "

#270 0.40 0.6 4 NR Microsilica§ (30%) "

#20-30 0.45 1.0 3 NR 0 "

#50-70 0.45 1.0 3 NR 0 "

#270 0.45 0.6 3 NR Fly Ash (20%) "

#270 0.47 0.6 3 NR 0 "

#270 0.55 0.6 3 NR 0 "

#270 0.55 0.6 3 NR Fly Ash (50%) "

0 0.30 0 4.8 11 (76) Solid Microsilica (10%) Balaguru and Kendzulak [1987]

0 0.27 0 3 9* (62) Fly Ash (40%) Mondragon [1987]

0 0.43 0 3 5* (34) Fly Ash (40%) "

0 0.30 0 3 3-14* (21-97) Fly Ash (0-100%) "

0 0.40 0 3 3-11* (21-76) Fly Ash (0-100%) "

0 0.30 0 3 7.5-17.0 (52-117) Fly Ash (20%) Homrich and Naaman [1987]

Table 2.1 cont’d Slurry mixture proportions used by researchers (amounts are by mass)

18

Sand W/CM S/CM HRWRA

fc!

ksi (MPa)

Mineral Admixtures

(by mass of cement) Reference

0 0.35 0 2 6.0-13.5 (41-93)

Fly Ash (20%) +

Microsilica§ (20%) "

0 0.30 0 4

6.0-12.5

(41-86)

Fly Ash (20%) +

Microsilica§ (30%) "

0 0.26 0 4 10.0-17.5 (69-121) Fly Ash (25%) Homrich and Naaman [1987]

0 0.35 0 3 NR 0 Akers and Bayasi [1994]

W/CM=Water/Cementitious Materials; S/CM=Sand/Cementitious Materials; HRWRA=High Range Water Reducing Admixtures in percent by weight

of cem ent; NR: Not Reported; * see Figures 2.6 and 2 .7

The numbers given under the column “sand” conform to ASTM Standard E-11, “Standard Specification for Wire-Cloth Sieves for Testing Purposes”

#20-30 : graded to pass a 850 µm (No.20) sieve and be retained on a 600 µm (No.30) sieve

#50-70 : graded to pass a 300 µm (No.50) sieve and be retained on a 212 µm (No.70) sieve

#250 : graded to pass a 68 µm (No.250) sieve; #270 : graded to pass a 53 µm (No.270) sieve

(1000 µm =1000 micrometer = 1 mm)

C109 refers to ASTM Standard C-109 “Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. Or 50-mm Cube Specimens)”

19

2.8) of the slurry. Tests conducted by Balaguru and Kendzulak [1987] suggest that sand can

be added up to a ratio of 1:1.5 (cement : sand) before slurry strength is adversely affected.

Some researchers (Vandergerghe, 1992) suggested the use of a factory-prepared dry mixture

requiring only the addition of water on site to insure better control and consistency.

2.3.2 Slurry Infiltration

In laboratory experiments to date, SIFCON or SIMCON has been produced by first

placing the fibers or the fiber mat in a mold and then infiltrating the fibers or the fiber mat

with a slurry mixture by gravity while external vibration is applied. However, application

of external vibration can pose a difficulty in practice. Marrs and Bartos [1996] investigated

self-compacting slurry mixtures for SIFCON. Their research included comparison of the

ability of different slurry mixtures to infiltrate fibers, and using flow cone and plate cohesion

meter, shown in Figure 2.9, to predict the infiltration. They concluded that the flow cone is

not a reliable test method for predicting the infiltration, however, a plate cohesion meter can

be useful for infiltration prediction.

2.4 SIMCON APPLICATIONS

The possible use of SIMCON in different shapes for repair and retrofit of reinforced

concrete beams were investigated by Krstulovic [1995]. SIMCON retrofitted beams showed

improvements in terms of stiffness, moment capacity, and energy absorption capacity.

Composite slabs using SIMCON as the tensile element with a concrete topping for stiffness,

were tested under three point bending by Bayasi [1995] (see Figure 2.10). In Bayasi’s tests,

20

Figure 2.7 Ultimate compressive stress versus water/(cement+fly ash) ratios(Mondragon, 1987)

21

Figure 2.8 Ultimate compressive stress at 30 day versusfly ash/(cement+fly ash) ratios (Mondragon, 1987)

22

Figure 2.9 (a) Marsh flow cone and (b) plate cohesion meter (Marrsand Bartos, 1996)

23

Figure 2.10 Flexural behavior of composite slabs with SIMCONtensile layer (Bayasi, 1995)

24

delamination cracks were observed close to the supports where high shear forces exist.

SIMCON was also used as a shear reinforcement by Krstulovic, et al [1999a] to

replace stirrups. In his study, several reinforced concrete beams without stirrups were

retrofitted with SIMCON jackets. He investigated shear span-to-depth ratio and bonding

between the SIMCON jacket and concrete. Krstulovic concluded that a SIMCON jacket can

be used effectively in place of stirrups. Krstulovic found that behavior of beams with

unbonded SIMCON jackets showed no substantial difference compared to beams which had

bonded SIMCON jackets even though at the higher load levels beyond the elastic response

of the beam, measured strains in the SIMCON jackets differed from analytical values that

might have indicated debonding of SIMCON. The explanation given by Krstulovic was that

at low load levels there might be friction between the SIMCON and concrete, possibly

increased by the drying shrinkage of SIMCON which led to binding of the unbonded jacket

to the reinforced concrete beam.

Krstulovic, et al [1997] also used SIMCON in different configurations with

reinforced concrete beams as shown in Figure 2.11. Krstulovic observed that delamination

of SIMCON top and bottom layers in two configurations were limiting factors in those two

beam failures. However, the failure of a beam, encased on three sides with SIMCON, was

initiated with the tensile failure of SIMCON. When the three-sided SIMCON jacket with

1 inch (25 mm) was used, it was reported that the maximum moment exhibited an average

of two times the reference values of reinforced concrete only section.

25

Figure 2.11 Experimental moment-curvature diagram of reinforcedconcrete-SIMCON composite beams (Krstulovic, 1997)

26

CHAPTER III

SCOPE OF THE STUDY AND

RESEARCH METHODOLOGY

3.1 SCOPE OF THE STUDY

The scope of this study was developed based on the literature survey and needed

information about the effects of construction on the in-service behavior of reinforced

concrete columns retrofitted with SIMCON jackets.

The literature suggested that the tensile and compressive behavior of SIMCON are

well established (Krstulovic, et al, 1995a; Krstulovic, 1996; Krstulovic, et al, 1999b). The

limited information available on SIMCON and concrete composite beam tests show that the

ultimate behavior is closely related to the composite beam cross section geometry. When

SIMCON is used only as a layer at the top or the bottom of a beam, bonding between

SIMCON and concrete becomes important (Bayasi, 1995; Krstulovic, et al, 1997). The

behavior of composite members with SIMCON jackets covering three or four faces of the

section were reported to be relatively insensitive to bonding at least up to the service load

level (Krstulovic, et al, 1997; Krstulovic, et al, 1999a).

No information was found in the literature examining the utilization of SIMCON to

strengthen or retrofit a reinforced concrete column. In particular, no information was found

27

regarding the sensitivity of SIMCON behavior, a relatively thin structural element composed,

in part, of a high strength cementitious slurry, to routine variations found in construction

materials in place or to routine construction practices which may affect design procedures

or construction and quality control requirements. If SIMCON is to be used to strengthen

columns, the effects of certain construction issues, including connection details and on-site

fabrication techniques, must be resolved.

Since SIMCON jacketing may be used in an unprotected environment, such as bridge

piers, there is a need for assessing the durability of SIMCON to frost. Because no research

data was found regarding the durability of SIMCON to frost attack or deicer scaling, the

freeze-thaw scaling durability of SIMCON when exposed to deicing salts needed to be

examined.

No information was found regarding the installed costs of SIMCON jackets.

Information is needed on cost in order to compare the economic viability of SIMCON jackets

with alternative jacketing options, such as Fiber Reinforced Plastic (FRP) wrapping and steel

jacketing.

3.2 RESEARCH METHODOLOGY

This study was conducted in three phases. The first phase examined the deicer

scaling durability of SIMCON. In the second phase, the construction of typical SIMCON

jackets was examined to identify characteristics, anticipated variability and consequences of

the construction process which could affect the structural behavior of the SIMCON jacket.

The effects were then analyzed, using simple structural models, to determine the likely

28

outcomes of those routine construction processes on load carrying capacity. The third phase

developed cost estimates of SIMCON jackets for comparison with alternative strengthening

techniques. The cost estimates were developed with sufficient accuracy to simply determine

if the technique was at least economically feasible. The cost estimate will, of course, vary

depending on the specifics of the project. An overview of this study is given in Table 3.1 as

a research methodology matrix. The parameters given in the table are not detailed; additional

levels and details are provided in subsequent chapters.

Table 3.1 Research Methodology Matrix

Investigated Parameter Methodology

Deicer salt scaling resistance of

SIMCON, ASTM C672

Experimental investigation to determine frost

resistance and entrained air requirements

Design and construction factors

Identify factors and evaluate those factors

analytically;

provide recommendations for design or

construction controls where appropriate

Cost analysis of SIMCON jackets Estimate the cost of a typical SIMCON jacket

application and compare with other typical

retrofit alternatives

3.2.1 Investigation of Deicer Salt Scaling Resistance of SIMCON

The first section of this study examined the deicer salt scaling durability of SIMCON

specimens. Acceptable frost durability of SIMCON was considered one of the critical factors

29

for the use of SIMCON jackets. The experimental evaluation of deicer salt scaling of

SIMCON was conducted following ASTM C672 procedures.

a) The effect of cracking of SIMCON on its scaling durability was examined on

specimens after cracks were induced using third point loading.

b) The presence of fibers and the process of placing the slurry may affect the in-place

air content in SIMCON. The very low water to cementitious materials ratio should mitigate

the frost damage somewhat, however. The sensitivity of air content on deicer salt scaling

resistance of SIMCON was planned to be examined by conducting ASTM C672 tests on

SIMCON which was similar except that either the material contained entrained air, or it did

not. The intended air content was in excess of 7%, which would have been minimal for a

paste. The actual air content obtained was considerably lower, however. While the results

are discussed in detail in Chapter 4, the low air content actually obtained proved to be

sufficient for this study.

3.2.2 Identification of Factors Related to Design and Construction

3.2.2.1 Methodology of Identification of Factors

In the second phase, construction factors which were likely to affect the behavior of

SIMCON jacketed reinforced concrete columns were identified and evaluated. This phase

was conducted in four parts. The first part involved identification of potential construction

effects or features which could affect behavior. The second part consisted of determining

the likely levels of the identified factors to be used in subsequent analysis. The third part

consisted of conducting simple structural analysis to determine both the relative effects of

30

the construction feature on the structural behavior and sensitivity of the structural behavior

to anticipated variation.

In this study, the construction factors identified in the first part were evaluated

predominantly using moment-curvature diagrams and short column axial load-moment

interaction diagrams. These are well established methods and can predict the non-linear

behavior of reinforced concrete. They are simple and ease to use compared to some other

methods such as finite element analysis. These analytical methods are appropriate for this

study since the primary purpose was to identify factors which would need to be resolved in

order to effectively use SIMCON jacketing in retrofit applications.

The last part of this phase consisted of ranking the effects as to “critical”, meaning

that routine variation could have a significant effect on the structural behavior which could

be critical either in service or in attaining the nominal, design load; “important”, meaning

that the effect was significant but could be easily controlled either in the design or using

simple quality control tests in construction; and “non-critical”, meaning that the effect was

not significant or did not cause unacceptable deviation from the nominal load carrying

capacity compared to conventional construction tolerances. For those effects which were

found to be critical or important, recommendations regarding control of the construction

process or needs for additional research were provided.

3.2.2.2 Identification of Factors Affecting the Behavior of SIMCON Jacketed Columns

The factors affecting the performance of SIMCON jacketed columns may be

considered in two categories, those factors which must be considered in the design stage,

31

such as whether to require a fully bonded jacket, and those factors which affect the behavior

and must be considered in establishing tolerances, such as whether routine variations in

dimensions or thickness provide acceptable behavior in service.

The desired dimensions and characteristics for any element are chosen at the design

stage. Similarly, with SIMCON jacketing, the designer can choose varying SIMCON

thicknesses and strength to fit the conditions and requirements. In reinforced concrete

structure design, there are certain assumptions which may not be applicable to SIMCON

jacketing, however. For instance, perfect bond is usually assumed between reinforcement

and concrete. This assumption has been validated in many cases in reinforced concrete

building. This assumption may not be valid with a new material and method like SIMCON

jacketing. Further, any attempt to make the SIMCON jacketing perfectly bonded to concrete

columns may not be fully beneficial or even necessary. Another example involves load

transfer at column-beam connections. In most reinforced concrete designs, these joints are

designed to be capable of transferring the moments, axial loads, and shear forces. SIMCON

jacket slab connections need to be examined to ensure adequate load transfer.

Another factor determined at the design stage could be whether to relieve the column

from existing loads or not. The backshoring of the existing floor system may be beneficial

in terms of more load carrying capacity in the column. However, if the costs outweigh

benefits, then jacking prior to the application of the SIMCON jacket need not be specified.

Hence, the investigation of effects of existing loads on SIMCON jacketed columns was

needed.

All construction practices and materials vary from ideal conditions even when they

32

are closely monitored to conform. The use of tolerances provides formal limits to these

variations. In reinforced concrete structures, these tolerances are usually provided by ACI

guidelines and specifications. The sensitivity of SIMCON jacketed columns to those

tolerances needed to be examined.

The minimum thickness of SIMCON is chosen by designer for expected loading

conditions considering the practical limitations of handling and forming the SIMCON jacket.

The fiber mats are commercially produced in 1 and 2 inch thicknesses, thicker SIMCON

jackets may be produced by applying several mats on each other. A thin SIMCON jacket

found adequate for expected loads may fail under compression with thin wall buckling.

Therefore, using the thin wall buckling example, the minimum thickness which would occur

in practice needed to be determined so that analysis of the structural effects could be

determined.

ACI 318 (ACI, 2002) specifies tolerances for concrete strength along with many

others. Some reductions from concrete design strength are tolerable. Routine variation

exists between the design and the in-place strength of concrete due to many variables, such

as materials and placement of concrete. The strength of concrete may be also affected by

frost damage. Therefore, the effects of the reduced SIMCON strength on the behavior of

SIMCON jacketed column needs to be examined. In this respect, the SIMCON strength

evaluation due to frost damage was conducted as explained in Chapter 4.

Routine variations in SIMCON thickness can be expected due to mishandling and

formwork dimension variations. Hence, the variations in thickness need to be examined.

Tolerances for dimensions and locations for reinforced concrete structures are given in ACI

33

117 (ACI, 1990). However, the tolerances given in ACI 117 may not be applicable to

SIMCON jackets due to factors, such as, a) the SIMCON jacket is a thin material compared

to existing column dimensions, b) the fiber mat compressibility is limited physically.

In addition, other factors affected by construction methods were examined, which

were not found in any published data. For example, the non-concentric placement of the

SIMCON jacket, that is, slightly off-center placement, may occur due to lack of control and

needs to be examined. The non-concentric placement of SIMCON means that some sides

of the jacket would be thinner than other sides and could affect behavior. The seams in the

SIMCON jacket due to fiber mat placement may also affect the behavior of jacketed

columns. Those effects should be examined.

After considering the typical tolerances and requirements and likely SIMCON

construction practices, the following items were identified as factors which needed to be

evaluated:

a) Bond between the SIMCON jacket and the reinforced concrete column,

b) Removal of load on existing reinforced concrete column prior to jacketing,

c) Routine variations in the SIMCON slurry strength,

d) Routine variations in the SIMCON jacket thickness,

e) Non-concentric placement of the SIMCON jacket,

f) Location and strength of fiber mat seams,

g) Thin wall buckling of the SIMCON jacket, and

h) SIMCON end connections to transfer end moments; bearing on the concrete slab

or beam where SIMCON transfers the additional axial load.

34

These were selected after preliminary analysis. Additional factors arising from a detailed

analysis were expected. The identification of these additional factors, the determination of

critical research needs, design criteria or construction control requirements constitute the

primary focus of this study. This preliminary list was not necessarily considered to be

exhaustive, pending detailed analysis, but was considered to be a critical step in the

acceptance of SIMCON as a feasible alternative for strengthening existing elements, both

technically for strength and durability, and economically.

3.2.3 Cost Analysis of SIMCON Jacketing

In the third phase, cost estimates for a routine SIMCON jacket application were

conducted. These costs were compared to the costs of selected alternative strengthening

techniques already used in practice. SIMCON costs, as installed, were based on a reasonable

work breakdown structure for this type of application using construction cost data commonly

available. The costs of alternative strengthening techniques, including FRP wrapping and

steel jacketing, were obtained from available construction cost data. This cost estimate was

not intended to provide detailed costs, since these are extremely sensitive to specific project

requirements. The cost estimate was provided simply to compare to the very broad ranges

found for alternative techniques to determine if the SIMCON alternative was at least

economically viable.

All phases of this study are clearly interrelated. The results of the deicer salt scaling

resistance of SIMCON, for example, may determine its criticality during construction. The

35

results obtained from analytical evaluation of selected factors may determine their criticality

and therefore their effects on construction costs. The interrelationships of critical or

important factors were also examined. Recognizing that identification and classification

required both subjective and objective evaluations, it was anticipated that a primary product

of this study was to help establish a priority of future research needs.

36

CHAPTER IV

DURABILITY PERFORMANCE OF SIMCON

4.1 OVERVIEW

SIMCON may be applied to columns, beams, or bridge piers as a jacket to improve

the capacity of the original structural member. When these applications occur in an exposed

environment, such as highway bridges and exterior elements in a structure, the durability of

SIMCON jacket must be considered. Since SIMCON is a low water/cement ratio material,

it should be more durable in aggressive media, all else being equal. SIMCON used to

strengthen highway bridge piers may be subjected to deicer chemical exposure, which is

more severe than simple frost attack of saturated concrete. This chapter describes the

experimental study conducted to assess the deicer salt scaling resistance of SIMCON jacket

material in freeze and thaw cycles.

4.2 EXPERIMENTAL PROCEDURES

The choice of experimental procedure to assess the frost resistance of a SIMCON

jacket around the concrete column was based on the characteristics of the SIMCON matrix,

a high strength slurry, and possible exposure conditions.

37

ASTM C666 “Standard Test Method for Resistance of Concrete to Rapid Freezing

and Thawing” (ASTM, 2002) evaluates the resistance of aggregate and paste under rapid

freezing and thawing. Several studies (Aïtcin, 1998; Pigeon, et al, 1991) have found that low

w/c ratio mixtures generally have good resistance to rapid freezing and thawing, even with

minimal air contents. Some studies have found reduced scaling resistance in very low w/c

ratio mixtures, especially when these mixtures contain a relatively large quantity of mineral

admixtures, including silica fume (Johnston, 1992; Biledaou and Malhotra, 1997). ACI 318

“Building Code Requirements for Structural Concrete and Commentary” (ACI, 2002)

prohibits the use of more than 10% silica fume in concrete exposed to deicing salts in order

to control scaling. Therefore, ASTM C672 (2002) was selected as a more representative

method of evaluating the response of SIMCON to frost attack.

ASTM C672 “Standard Test Method for Scaling Resistance of Concrete Surfaces

Exposed to Deicing Chemicals” (ASTM, 2002) measures the resistance of concrete to scaling

in the presence of deicing chemicals. This test is conducted at realistic, but high freezing

rates and is considered to be more indicative of frost resistance in service. This test also has

limitations, however. Durability is determined by visual ranking. The rating of scaling is

somewhat subjective, although the standard contains guidance.

The study was originally developed as factorial design with two factors and two

replicates for each condition. As seen in Table 2.1, the slurry mixtures used in this study had

similar proportions to those in other studies. Therefore, it was decided to focus this study

on critical factors other than water/cement ratio, or other properties of the slurry mixture.

Consequently, only a single mixture, similar to that proposed by Krstulovic [1999] was used.

38

Since this study is intended to investigate the frost durability of the matrix, only one volume

of fibers is used. The possible effects of different volumes of fibers may be considered in

future research.

4.2.1 Main Variables

The experimental variables considered to be most critical were the level of air

entrainment and the presence of cracks in the specimen. High strength concretes typically

contain lower air contents for frost protection. Air contents specified in ACI 301 and 318

can be reduced by 1% for concrete with a specified compressive strength greater than 5000

psi (34 MPa). Since SIMCON uses a very high strength slurry, it was desired to examine

the sensitivity of the frost resistance of the material to air content which can affect strength.

For this study, two extremes in air content were to be investigated in order to achieve, if

possible, a clear indication of the difference in behavior, due to the limitations of the usual

rating system. Some studies, using rapid freezing and thawing tests rather than deicer salt

scaling, have indicated that non-air entrained concrete provides acceptable durability if the

w/c ratio is very low (Aïtcin, 1998). No information was found for very low w/c ratio

materials (less than 0.30) undergoing deicer salt scaling tests. The use of non-air entrained

specimens in the test matrix would permit simultaneous examination of this phenomenon for

a very low w/c ratio slurry containing a significant quantity of silica fume, exposed to deicer

solutions. A high air content, achieved by using the maximum dosage recommended by the

manufacturer, and the worst possible condition, non-air-entrained, were selected as the two

experimental conditions for this variable.

39

The SIMCON jacket is expected to be cracked in service. The application of load or

the effects of restrained shrinkage will induce cracking. The cracks in SIMCON are typically

very fine and closely spaced, as would be expected with a high steel ratio composed of small

diameter, dispersed reinforcement (Krstulovic and Malak 1997; Krstulovic and Al-Shannag,

1999). These fine cracks are small enough to have significant capillary suction and large

enough that water can enter freely. The effects of freezing on finely cracked concrete have

not been established. In addition, the small diameter reinforcement could corrode in the

severe deicing salt exposure of ASTM C672, contributing to scaling, since they are close to

the surface, or causing additional cracking. It was believed to be critical to assess the

behavior of the cracked SIMCON simultaneously exposed to salt solution and freezing and

thawing cycles. The test matrix therefore included two specimens of each set of four which

were cracked before they are subjected to freezing and thawing cycles. Table 4.1 displays

the variables and properties of SIMCON specimens. To improve statistical power, two

specimens were tested for each variable.

4.2.2 Mixture Used in the Experimental Study

The SIMCON slurry mixture proportions used in this part of the study are given in

Table 4.2. If the specimen is air entrained, then, the amount of air entraining admixture

given in Table 4.2 is added to the mixture, otherwise no air entraining admixture is added.

40

Table 4.1 Scaling test variables and SIMCON specimens’ properties

specimen no * air entrained cracked

A11NC-3 Y N

A14NC-10 Y N

A12CR-6 Y Y

A13CR-9 Y Y

N21CR-5a N Y

N23CR-7a N Y

N22NC-6a N N

N24NC-8a N N

* A=air entrained; N=no air entrainment; NC=not cracked; CR=cracked

Table 4.2 Slurry mixture proportions by mass

Wi/Wc [1]

Portland cement; Type III 1.0

Added water to the mixture 0.31

#250 Ottawa silica sand 0.60

Microsilica slurry [2] 0.30

High range water reducing admixture [3] 0.04

Air entraining admixture [4] 3 oz/100 lb (200 mL/100 kg)

[1] Wi=the mass of material; Wc= the mass of cement

[2] Microsilica slurry contains 49.7% solids

[3] HRWRA, ADVA 100, produced by W.R. Grace & Co. and meets ASTM C494,

Type F. One gallon weighs approximately 8.3 lbs (1.06 kg/L)

[4] Air entraining admixture, Daravair 1000, W.R.Grace &Co. and meets ASTM

C260.

41

The ratio of water to cementitious materials was 0.40 as shown in Equation 4.1.

water water added to the mixture + water in the microsilica slurry ))))))))))))))) = ))))))))))))))))))))))))))))))))))))))))) cementitious materials portland cement + silica fume in the microsilica slurry

0.31 + 0.15 = )))))))) = 0.40 (4.1) 1.0 + 0.15

The ratio of silica fume to cementitious materials was 0.13 as shown in Equation 4.2.

silica fume Silica fume in the microsilica slurry ))))))))))))))) = )))))))))))))))))))))))))))))))))))))))cementitious materials Portland cement + silica fume in the microsilica slurry

0.15 = )))))))) = 0.13 (4.2) 1.0 + 0.15

The desired air content was chosen assuming a severe exposure to frost attack. The

desired air content was selected to be some amount in excess of 6%. Neville [1997] states

that in the presence of a high proportion of ultrafine aggregate materials, and with low

water/cement ratios, more admixture is required. Therefore, the maximum addition rate of

air entraining admixture recommended by the manufacturer was used.

The volume of fibers, Vf, of SIMCON specimens was 1.6%. This steel fiber volume

ratio was selected to ensure that the steel fiber mats were infiltrated fully by the slurry

mixture under gravity, while maintaining a quantity sufficiently high to demonstrate any

contribution to deicer salt scaling and sufficiently low that any benefit from reinforcement

was minimized. Therefore, a reasonable worst-case scenario was investigated.

42

4.2.3 SIMCON Specimen Preparation and Testing

SIMCON slab specimens were prepared according to ASTM C672 specifications.

As shown in Figure 4.1, 12 in. by 12. in (305 mm×305 mm) SIMCON mats were prepared

and infiltrated by the slurry mixtures under gravity. Meanwhile, 2 in.×2 in.×2 in. (51 mm×51

mm×51 mm) slurry mixture cubes were prepared to determine their compressive strengths.

After casting, all the specimens were covered with a plastic sheet and left at room

temperature in a laboratory environment. After 24 hours, the specimens were demolded and

submerged in a lime-water bath for 14 days. All the specimens were then air dried for 14

days after removal from the water. At the 28th day after casting, four of the specimens were

cracked under three point bending (see Table 4.1). Crack widths ranged from 0.010 in.

(0.254 mm) to 0.024 in. (0.610 mm), and were 0.016 in. (0.406 mm) on average. At this

time, silicon dams were formed on the surface to hold the calcium chloride solution.

Slurry cubes were tested in compression at 28 days. The slurry containing the air

entraining admixture had an average compressive strength of 8350 psi (57.6 MPa); the non-

air entrained slurry had an average compressive strength of 12160 psi (83.9 MPa) as shown

in Table 4.3. The calcium chloride solution was prepared in accordance with ASTM C672,

such that each 100 mL of solution contained 4 g of anhydrous calcium chloride (5.345 oz per

gallon). The specimens were covered to a depth of ¼ in. (6 mm) with calcium chloride

solution at 28 days after casting. The specimens were then frozen for 16 to 18 hours and

thawed for 6 to 8 hours in air. Two of the applied freeze and thaw 7-day cycles are shown

in Figure 4.2 as an example. Between each cycle, the solution was checked and maintained

at the proper depth daily. Every fifth cycle, specimens were flushed with fresh water and the

43

Figure 4.1 SIMCON specimen for deicing salt scaling test

44

Figure 4.2 Time-temperature graph of freezing environment

45

solution replaced.

Table 4.3 Compression strength of slurries with and without air entrainment

Non-air entrained 10680 psi (73.6 MPa)

Fcomp,avg = 12160 psi (83.9 MPa)Non-air entrained 12910 psi (89.0 MPa)

Non-air entrained 12700 psi (87.6 MPa)

Non-air entrained 12710 psi (87.6 MPa)

Non-air entrained 11820 psi (81.5 MPa)

Air entrained 7950 psi (54.8 MPa)

Fcomp,avg = 8350 psi (57.6 MPa)Air entrained 9140 psi (63.1 MPa)

Air entrained 8030 psi (55.4MPa)

Air entrained 8270 psi (57.0 MPa)

4.2.4 Air Content

4.2.4.1 Test Method

Methods such as ASTM C231 or C173 (ASTM, 2002) are typically used to determine

the air contents of fresh concrete. However, the air content of the fresh concrete was not

measured due to several reasons. First, the volume required for testing using these methods

is quite large. While a smaller quantity could have been used, it was decided to determine

the air content of the hardened slurry, after infiltration, due to possible detrimental effects

on the air void system due to the fiber mat. Therefore, microscopic examination of both

hardened slurry specimens and specimens taken from slabs after testing, which included the

fiber mat, was used to determine the total air content, the average spacing factor, and the

specific surface of the air void system.

46

The air contents of hardened slurry cubes were determined microscopically according

to ASTM C457 “Standard Test Method for Microscopical Determination of Parameters of

the Air-Void System in Hardened Concrete” (ASTM, 2002) except that the depth between

adjacent slices was smaller than required, possibly reducing the precision somewhat but

certainly not enough to affect the results of this study, since no coarse aggregate was used.

ASTM C457 specifies that a sample have a minimum area of 7 in2 (45 cm2) of

finished surface for microscopic measurement. Since the cubes could provide only about 3

in2 (19 cm2), they were sliced into three pieces as shown in Figure 4.3 to provide the required

area. The surfaces were polished using silicon carbide abrasives. Typical air voids are

shown in Figure 4.4.

After the scaling test of the SIMCON slabs was completed, specimens A11NC-3,

A12CR-6, N21CR-5a, and N24NC-8a were cut and microscopic analysis of the air-void

system was conducted. Due to the steel fibers in the specimens, the specimens could not be

polished as required by ASTM C457. The air void analysis of these sections was not

conducted, therefore, strictly in accordance with the standard. The results are acceptable for

this study, however, for several reasons. First, due to the very fine structure of the slurry

matrix, which contained no aggregate, the saw cut surface provided a relatively smooth

surface for examination. Second, it was not necessary to determine the air content with high

precision. The purpose of the analysis was simply to compare the air content of the

SIMCON specimen with that of the slurry cube, due to concern that by infiltrating the slurry

through the fibers, the entrained air content would change.

47

Figure 4.3 Slurry cube cuts for microscopical examination of the air-void system

48

Figure 4.4 Entrained air bubbles in hardenedslurry

49

4.2.4.2 Results of Microscopic Examination

Using a 50× microscope, the modified point count method (ASTM C457, Procedure

B) revealed the total air content of the hardened slurry cubes containing air entrained

admixture, averaged 2.5%. The spacing factor (L6), a critical factor in the ability of an air-

void system to provide protection against frost attack, was found to be 3.96 mm (0.156 in.).

The maximum spacing value recommended for frost durability is 0.2 mm (0.008 in.) for

moderate exposure (ACI 201, 1992). The specific surface, ", the surface area of the air voids

divided by their volume, was found to be 2.9 mm-1 (73 in-1). The specific surface is usually

in the range of 25 to 50 mm-1 (600 to 1100 in-1) (ACI 201, 1992) for concrete with acceptable

frost resistance. All of these indicate an air void system which does not meet the minimum

recommended standards for frost protection of conventional concrete.

Microscopic analysis of the non-air entrained slurry cube found no entrained or

entrapped air voids. A higher power magnification would probably have revealed at least

a few air voids in the slurry matrix (ASTM C457, 2002), however the lack of voids detected

with 50× magnification is significant. This finding indicates excellent consolidation even

with simple gravity infiltration as well as the lack of entrained air.

Microscopic analysis revealed that the nominally air entrained specimens taken after

testing, A11NC-3 and A12CR-6, had air contents of 2.5% on average, which was identical

to the air content found in air entrained slurry cubes, therefore, it appears that using simple

gravity infiltration does not affect the air content significantly. In addition, this indicates that

much higher additions of air entraining agent are required to provide a high air content with

this mixture.

50

It was surprising to find very low air contents in the slurry cubes and SIMCON

specimens because the quantity of air-entraining agent used was sufficient to easily produce

an excess of entrained air in conventional concrete. The low air content found in the

hardened cement paste may be due to mixing the slurry for a long time after adding the air

entraining admixture, the high amount of silica fume in the mixture or both. The high

fluidity of the slurry may have also contributed to the low air content. Very high slumps can

result in a reduction in air content in conventional concrete under certain conditions. This

was not anticipated due to the low w/c ratio and the fact that the fluidity was due to the use

of a HRWR, however, it could have played a role. It was surprising to find essentially no air

in the non-air entrained slurry specimens, since some entrapped air can usually be found in

all mortars, especially in the absence of vibration.

The microscopic determination of air content of the hardened slurry cubes was

completed well before the end of the C672 testing phase. It was decided to continue the

deicer salt scaling test program for several reasons, even though the air entrained SIMCON

specimens did not meet ACI recommendations for air content. The test was already

underway at this point and both the air entrained and the non-air entrained specimens had

exhibited satisfactory resistance so far. In addition, this would permit evaluation of the

durability to deicer salt scaling with a minimal air content.

4.3 TEST RESULTS AND DISCUSSION

4.3.1 Scaling Resistance

All SIMCON specimens showed good scaling resistance. The SIMCON specimens

51

had a scaling rating of 1 or 2 which corresponds to light scaling. Visual observations of test

specimens showed no difference in specimen scaling due to air entrainment or due to

cracking. Photographs taken after the test are included in Appendix B (see Figure B.1 to

Figure B.8).

Although the recommended air contents were not achieved, the low water/cement

ratio used in the production of SIMCON provided a hardened mixture with very low

permeability, which is an important factor in resistance to frost attack and deicer scaling

resistance. This testing program showed that air entrainment is apparently not necessary for

frost scaling resistance, therefore no additional tests were conducted incorporating higher air

contents.

The lack of scaling was apparently a paste phenomenon. It was originally speculated

that at least two factors might affect the deicer salt scaling resistance of the SIMCON. The

presence of the fibers might reduce scaling somewhat by holding the paste together at the

surface and resisting the stresses due to temperature, moisture or salt gradients. Alternately,

the slurry directly over the fibers could be expected to flake off preferentially at a relatively

early stage, and deeper flaking would be expected between fibers. The lack of this type of

flaking indicates that the excellent deicer salt scaling resistance observed was due to the high

quality of the slurry. The presence of the fibers had little, if any, effect, however.

4.3.2 Effects of Cracking on Frost Durability

After the scaling test, crack widths of cracked specimens were measured. No

significant widening of cracks was observed. Either cracks were not affected by the freeze

52

and thaw cycles, or the effect was negligible and changes in crack widths could not be

detected, or the number of freeze-thaw cycles were not sufficient to produce any significant

effect on the cracks. Since there should be a number of fibers bridging cracks, they should,

in the absence of corrosion, distribute the expansive stresses. The high quality of the slurry

may have contributed to the lack of effects of expansion of cracks noted. It may be

concluded that the presence of cracks did not affect the deicer salt scaling resistance of

SIMCON specimens.

4.3.3 Corrosion of Fibers

Another interesting result of the scaling resistance test was the opportunity to evaluate

corrosion of the fibers. The fiber mat is made of Type 304 stainless steel fibers. Type 304

is a general-purpose grade stainless steel, having good corrosion resistance and formability

(Sedriks, 1996). This type of stainless steel contains approximately 18% chromium, which

prevents the formation of rust in unpolluted atmospheres. Generally, the corrosion resistance

of stainless steel is provided by a very thin surface layer, known as the “passive layer”, which

is self-healing provided oxygen is available (Sedriks, 1996). Compared to some other types

of stainless steels, Type 304 is attacked to a greater extent in the presence of chlorides but

produces little loss of steel by corrosion (Chandler and Bayliss, 1985). In situations when

the protective film layer on steel cannot be reformed, pitting corrosion may occur, however.

This is more serious in immersed conditions, and even worse when the chloride

concentration of a solution is significant, which increases the pitting (Sedriks, 1996).

As shown in Figure 4.5, SIMCON test specimens showed numerous rust stains on

53

their sides. Figure 4.6 also shows a slice taken 0.7 in. (18 mm) deep from the same surface

shown in Figure 4.5. In Figure 4.5, the rust stains are clearly noticeable on protruding

strands of fiber, however, as shown in Figure 4.6, corrosion does not penetrate past the

surface. Corrosion was generally less on the surfaces (top of specimen) covered with

calcium chloride solution than on the sides of the specimens. The reason could be chloride

solution spills or contamination from adjacent specimens. The sides were continuously

exposed to oxygen while ponded surfaces were not, which may have also affected the

corrosion. Since, at the field, SIMCON will be exposed to deicer salt sprays and air, it is

possible too see some rust develop on the fibers protruding from the SIMCON jacket

surfaces. This may become a visual problem, therefore, needs to be investigated.

No difference was noted in corrosion between the cracked and uncracked specimens.

In cracked samples, no significant corrosion was noted on the fibers located in the cracks.

Although the cracks (ranging from 0.010 in. (0.254 mm) to 0.024 in. (0.610 mm), and on

average 0.016 in. (0.406 mm)) were equal to or sometimes larger than the maximum

tolerable crack width suggested in ACI 224 (1980), which is 0.016 in. (0.41 mm), the

stainless steel fibers incorporated in a dense, low w/c ratio matrix successfully resisted the

corrosive effect of calcium chloride solution for the duration of the test. Therefore, it may

be concluded that the SIMCON slabs exhibited excellent resistance to the corrosion of

embedded steel fibers in a severe salt exposure including multiple cycles of freezing and

thawing. The high quality matrix appears to provide adequate passivation of the stainless

steel reinforcement although additional, longer term studies, including the effects of

carbonation, should be conducted.

54

55

56

4.4 CONCLUSIONS

1. The SIMCON specimens, exposed to freezing-and-thawing cycles in the presence of

deicer salt, exhibited very slight scaling, indicating good to excellent resistance.

2. Air entrainment was not found to be required for satisfactory resistance to deicer salt

scaling, probably due to the very low w/c ratio used.

3. Excellent deicer salt scaling resistance was obtained even though the silica fume content

(13% of total cementitious materials), was higher than the limits (10%) recommended in ACI

318 (ACI, 2002).

4. Based on microscopic analyses on the slurry cubes and SIMCON specimens, excellent

consolidation was achieved with simple gravity infiltration.

5. The lack of entrained air in slurry cubes revealed by microscopic analysis indicates that

much higher additions of air entraining agents are required to provide a high air content with

this mixture.

6. The presence of cracks did not affect deicer salt scaling or corrosion.

7. Corrosion was observed only on fibers which were not embedded, the high quality matrix

apparently provides satisfactory protection, or passivation, for stainless steel fibers, at least

for the duration (approximately 2 months) of this severe test.

8. Corrosion may at least become a visual problem where the SIMCON is exposed to deicer

salt solutions.

57

CHAPTER V

ANALYTICAL EVALUATION OF

DESIGN AND CONSTRUCTION FACTORS

5.1 OVERVIEW

This chapter begins with a discussion of the identification of construction factors

which could affect the behavior of SIMCON jacketed columns in service or at ultimate load.

This is followed by an overview of the cross sections and materials used in the evaluation.

After that, the methods used for analysis are briefly described. Later, based on given

materials properties and geometries, the construction factors are evaluated using these

analytical methods, and the results compared to each other and to published results.

Several construction and constructibility factors affecting the behavior of SIMCON

jacketed reinforced concrete columns were identified and evaluated in this study. For the

identification and selection of factors related to construction and design of SIMCON, either

relevant ACI specifications and guidelines were referenced or possible critical aspects which

may be encountered in a SIMCON strengthening project were examined.

58

5.2 IDENTIFICATION OF FACTORS TO BE EVALUATED

5.2.1 Identification of Design Factors with Significant Construction Effects

Several factors were identified which, although they are clearly design issues, might

have a significant effect on the construction process itself. These factors were examined to

determine if their effects on the predicted behavior of the SIMCON jacketed column would

be critical. The factors identified included the effects of bonding between the jacket and the

column, the removal of existing load prior to construction, the requirement for end

connections between the jacket and the horizontal structural element and the potential for

thin wall buckling of the jacket.

5.2.1.1 Bond Between SIMCON and Reinforced Concrete Column

Investigation of bonding of SIMCON to concrete was considered important because

bonding affects the ultimate behavior of composite beams. When the SIMCON is placed as

a layer on top or at the bottom of reinforced concrete beam, delamination can occur. When

SIMCON was placed around various concrete sections in bending, it was found that

unbonded and bonded behavior differs slightly (Krstulovic, et al 1997 and 1999a).

In the literature review section, it was shown that SIFCON exhibits drying shrinkage

in the order of 0.02% to 0.05% after 21 days of casting. It may be reasonable to expect

similar shrinkage behavior from SIMCON. This type of shrinkage may have affected results

of unbonded SIMCON jackets in experiments conducted by Krstulovic, et al [1997 and

1999a]. Those SIMCON jackets demonstrated no difference in bonded and unbonded

behavior at least up to service load levels. Therefore, one may expect, even in the absence

59

of special bonding techniques, a reasonable bond to be developed between SIMCON and

concrete due to SIMCON drying shrinkage.

It was anticipated that bonding of a SIMCON jacket to a column may not pose a

problem. But this factor was identified as potentially critical since bonding also would

clearly affect the costs of construction as well as the column behavior. If the bonding were

found to be critical, then a good bond between SIMCON and concrete had to be ensured

rather than simply assumed due to differential shrinkage. To develop a good bond capacity,

a method similar to concrete-steel composite construction such as inserting studs into

concrete column or some other alternative method could be employed. If analysis shows that

the bonding is not critical, costs will be lower. An unbonded jacket would also prevent

possible damage to the existing concrete column by inserting studs.

5.2.1.2 SIMCON End Connections

SIMCON jacketing is anticipated in situations where an increase in both axial load

and the bending moment capacity of a column is desired. These capacity increases require

tensile and compressive forces to be developed in the SIMCON, and those forces must be

adequately transferred by connections between the SIMCON jacket ends and the slab or

beam to which it is attached. For example, the compressive forces may cause a punching

shear failure in a slab or localized crushing of the surface, because at ultimate load the

compressive stresses in the high strength SIMCON may exceed the bearing capacity of the

concrete in the connecting slab or beam which was probably placed with a lower strength,

commodity grade, commercial concrete.

60

Constructing SIMCON pedestal and capital at the ends of the SIMCON jackets may

be required to transfer and distribute the SIMCON compressive forces to the beams or slabs.

The tensile connections may be constructed in several ways, including the use of drilled

anchors or an epoxy agent. If longitudinal shrinkage is expected to be a problem, one

solution might be to leave a gap at the top of the jacket and later fill the gap with epoxy or

cementitious non-shrink grout after an adequate curing and drying period to avoid additional

tensile stresses due to the drying shrinkage of the SIMCON. Low fire resistance, creep, and

shear resistance properties of epoxy should be considered, however.

Another connection scheme could involve using steel collars at the ends. In this case,

although an adequate steel collar can be designed to resist loads, consideration should be

given to connection of the steel collar-SIMCON jacket to the concrete slab or footing.

Related concerns include the need to place anchors within the SIMCON, column and the

slab, and means for ensuring load transfer to the SIMCON jacket. These factors will clearly

affect the construction sequence requirements, and cost of a SIMCON jacket.

5.2.1.3 Removal of Load on Existing Reinforced Concrete Column Prior to Jacketing

It is reasonable to assume that in many cases the column to be strengthened is in an

older structure. It is known that an axially loaded, reinforced concrete column subjected to

constant load experiences a gradual but significant redistribution of stress with time; the

concrete stress decreases while the steel stress increases (Park and Pauley, 1975). If the load

is removed quickly, both the steel and the concrete undergo an instantaneous elastic recovery.

However, since the load carried by the steel has increased, while that for the concrete has

61

decreased due to creep, the steel tries to recover more than the concrete. The steel therefore

retains some residual compression while the concrete becomes stressed in tension, which

may cause cracking. The use of backshores to remove the external load on the reinforced

concrete column may create cracking in the column before the SIMCON jacket is applied.

The use of or the lack of backshores may affect the ultimate load behavior of SIMCON

jacketed columns. If analysis indicates that the removal of existing column load does not

have a significant effect on the behavior of SIMCON jacketed column, then backshoring

need not to be specified, and clearly the lack of backshores would decrease costs.

5.2.1.4 Thin Wall Buckling of SIMCON Jacket

One of the limiting factors in design of thin walled compression members is buckling

(AISC, 1995). Since SIMCON is an axially loaded, thin element, it may fail by local

buckling. The likelihood of thin wall buckling even may become greater if the SIMCON is

placed non-concentrically around the column, or if the SIMCON is thinner in one spot or

another due to routine construction variation. Another factor affecting thin wall buckling of

SIMCON jacket may be the bond between SIMCON and concrete. If SIMCON is perfectly

bonded to concrete, then the risk for thin wall buckling of SIMCON is reduced because of

the adhesion to the concrete. Therefore, the criticality of this factor depends in part on the

findings regarding criticality of bond. Thin wall buckling of the SIMCON jacket may be

controlled by specifying a greater thickness or establishing appropriate tolerances, if

required.

62

5.2.2 Identification of Factors Occurring During Construction

A number of factors were identified which would occur during construction and

which could affect behavior or, by logical extension, the design. Many of these factors

involve routine construction tolerances. The factors identified included variations in strength

of the SIMCON slurry, variations in thickness of the SIMCON jacket, variations in centering

the SIMCON jacket, and location of the fiber mat seams.

5.2.2.1 Routine Variations in SIMCON Strength

Routine variations in the properties of the constituents and variations in the

placement of the SIMCON slurry will cause the strength of the SIMCON to differ from

design strength. Slight changes in the water/cement ratio lead to variations in strength (see

Figure 2.7). The strength reduction could also be caused by frost damage. While this was

considered to be potentially problematic in the original development of factors, the likelihood

of serious damage due to frost attack was found to be minimal (see Chapter 4).

The lower strength may cause changes in ultimate axial load and moment capacities.

In ACI 318 [2002], the strength reduction factor for columns is lower than that for beams

because the strength of the concrete has a greater effect on the strength of a column than on

a beam. The anticipated strength variations of SIMCON jacket, when used to strengthen a

column will affect the capacity of the jacket-column system. If the effects of routine strength

variation do not have a significant effect on the ultimate load capacity, then routine variations

in strength of SIMCON may be permitted. Otherwise, additional constraints on construction

or a more conservative strength reduction factor may be required.

63

5.2.2.2 Routine Variations in SIMCON Jacket Thickness

SIMCON thickness may be affected by several factors at the construction site. These

factors include: (a) tolerances in the formwork dimensions as built or erected, (b) excessive

clamping forces on the formwork, and (c) bulging in formwork due to slurry injection

pressures.

SIMCON thickness may effect the behavior in several ways: (a) the ultimate axial

load capacity will be directly effected, (b) a thinner jacket may cause thin wall buckling of

the SIMCON jacket under compression, and (c) an enlarged SIMCON area will increase the

stiffness of a jacketed column. Since the SIMCON jacket is relatively thin, routine

construction tolerances may be too lenient requiring more stringent dimensional tolerances

or modifications in design requirements.

5.2.2.3 Non-Concentric Placement of the SIMCON Jacket During Construction (Centering)

Due to routine placement operations, formwork, and therefore the fiber mat, may be

placed non-concentrically around the existing column, that is, the jacket will not be centered

on the column. These variations in placement may affect the behavior in two ways: (a) the

moment carrying capacity of the column may be negatively affected, and (b) if the non-

concentric placement occurs in such a way that the thinner part is axially loaded excessively,

this may cause thin wall buckling of SIMCON. Again, the effects of multiple tolerances

must be examined.

64

5.2.2.4 Location and Strength of Fiber Mat Seams

According to Krstulovic, et al [1999b], SIMCON was not found to be sensitive to

fiber orientation under compression. SIMCON may also not be very sensitive to fiber

orientation under tension because of the scatter in orientation of the fibers in a mat.

Therefore, the fiber mat may be chosen to be placed in any way as long as it is feasible to do

so at the construction site. The method used to wrap the fiber mat around the concrete

column may pose another concern, however. The fiber mat seams may have less strength

due to fiber concentration and the difficulty of achieving good infiltration with the slurry if

the seams overlap. If the fiber mat is left butt-ended against itself this may contribute to

lower strength at that seam location. Therefore, seams may affect axial load and bending

moment capacities. Placement of seams one way or another may also have an impact on

construction practice.

The fiber mat rolls are commercially provided in 4 feet (1.22 m) widths. These rolls

can be either longitudinally wrapped or in discreet rings around the column. If the column

is wrapped longitudinally with a mat, then seams are placed longitudinally.

One issue to consider is the difficulty or ease in placing the mat using any one of

these three methods. If the mat is wrapped around the column beginning from the bottom,

it may be easier to place the upper portion by resting on the mat below. Spiral placement

may cause some waste in cutting the mat at the column bottom and top, however this may

be preferable because of the continuity provided. If the column wrapped is very large,

however, it may become necessary to place the mat in discreet rings, one on top of the other.

In this case, seams may be staggered. Analysis may indicate the importance of seams and

65

also help resolve the placement of seams.

Clearly, some precautions against seam opening during slurry injection must be

provided to avoid an unreinforced seam. Experimental work appears to indicate that this

potential problem can be avoided by tying the mat securely in place with tie wire.

5.3 ANALYTICAL METHODOLOGY

5.3.1 Analytical Methods Used For Evaluation of Factors

The factors selected for investigation were evaluated in terms of their effects on

ultimate load and service load behavior of SIMCON jacketed columns. The cross sections

and materials were selected from the most typical cross section types and materials of

reinforced concrete columns reasonably found in a majority of structures. The effects of

selected factors were evaluated on otherwise identical columns. For evaluation of the

factors, several methods were employed. These methods included moment-curvature

diagrams, short column axial load-moment interaction diagrams, and thin wall buckling

solutions.

Short column axial load-moment interaction (Pn-Mn) diagrams are the common

procedures for the basis of design procedure for reinforced concrete columns. Moment-

curvature (M-n) diagrams can also be calculated assuming varying axial loads. In this study,

however, moment-curvature (Mo-n) diagrams were examined only for zero axial load

condition. These procedures usually involve straight-forward computations. Therefore,

these two analytical tools were primarily employed in this study. Some representative axial

load-moment interaction and moment-curvature diagrams were shown for selected factors,

66

but evaluation of factors were based on axial load capacities (Pn,max) from Pn-Mn diagrams

(see Figure 5.1.a), and maximum moments (Mo,max) from Mo-n diagrams (see Figure 5.1.b).

Although the curvature values from the Mo-n diagrams could also be used for evaluation in

addition to Pn,max and Mo,max comparisons, after preliminary analysis, it was decided that they

would not provide as much insight as Pn,max and Mo,max comparisons, and therefore were not

used. The following factors were evaluated using Pn-Mn and Mo-n diagrams; a) bonding

between SIMCON and reinforced concrete, b) removal of the load on an existing reinforced

concrete column prior to jacketing, c) routine variations in SIMCON design strength, d)

routine variations in SIMCON jacket design thickness, e) non-concentric placement of

SIMCON jacket, and f) location and strength of fiber mat seams. The results were

graphically given in this chapter. The tabulated results are provided in Appendix C for the

evaluated factors.

Thin wall buckling of SIMCON jacket evaluation was based on the solutions of

Timoshenko [1961] for elastic structures. SIMCON end connections were evaluated by

comparing possible alternatives.

5.3.2 Determination of Criticality of the Factors

Once the factors were evaluated, their effects were compared to the effects of

appropriate ACI tolerances on the reinforced concrete column sections which were used in

this study. The ACI strength and dimensional tolerances were applied to square and circular

reinforced concrete column cross sections, and the effects of the tolerances on the columns

were determined analytically. The criticality of the factors was established based on

67

Figure 5.1 Definitions of Pn, max and Mo, max

Moment (Mol

o,mox ~

M ................. ,,-....--........

• • E c ,

Curvcture (,.,l 0)

68

comparison of the results of the analysis of the behavior of the SIMCON jacketed columns.

If a factor produced effects similar to those found with conventional concrete column

performance, using routine tolerances, then the level of the factor used in analysis was

determined to be satisfactory. If the effect of a factor was found to be negligible, then the

factor was considered “not important”. If analysis indicated the factor was important or

critical to the composite behavior of the SIMCON jacketed column, appropriate tolerances,

construction requirements, or guidance or design limitations were suggested where possible.

If a solution to the problem could not be determined on the basis of this study, additional

research was recommended. As noted above, a significant result of this study was to

prioritize future research needs, if any, to permit the application of this product and technique

in practice.

5.3.3 Cross Sections

Two cross sections, a square and a circular section, as shown in Figure 5.2, were

analyzed to find their moment-curvature curves and axial load-moment interaction diagrams.

In addition, biaxially loaded, square sections, as shown in Figure 5.2, were also analyzed.

These cross sections were chosen as representative of two distinct types of cross sections and

were therefore expected to exhibit at least somewhat different behavior. The cross section

dimensions were selected to represent those commonly found in column members which

might be encountered in retrofit operations. The size of each cross section was chosen to

provide a similar gross area of concrete; a 16 in. by 16 in. (400 mm by 400 mm) square and

18 in. (460 mm) diameter circular cross section were analyzed.

69

Figure 5.2 Cross sections used in analysis

70

Figure 5.2 cont’d Cross sections used in analysis

71

Figure 5.2 cont’d Cross sections used in analysis

72

(5.1)

(5.2)

ACI 318 Sec.10.9.1 (ACI, 2002) limits the reinforcement area to not less than 0.01

times the gross area and not greater than 0.08 times the gross area. The most economical and

therefore commonly found range of reinforcement ratio is from 3% to 6% (MacGregor,

1997). In the analysis, two reinforcement ratios, 2% and 4% of the gross area were

examined. The cross sections, reinforcement ratios and SIMCON jacket thicknesses used

in the analysis are presented in Table 5.1.

5.3.4 Material Characteristics

Reinforcement steel, concrete and SIMCON material stress-strain relationships used

in the analysis are given in Figures 5.3, 5.4, and 5.5, respectively.

The concrete in the existing column was assumed to have a nominal 5000 psi (34

MPa) compressive strength. The concrete compressive stress-strain relationship is assumed

to be parabolic (ACI 318, 2002), and given by the Equation 5.1.

where fc is compressive stress, fc! is compressive strength, g is strain, and go is the strain at

which compressive strength is attained and equal to 0.2%. Also, the concrete tensile stress-

strain relationship is assumed to be parabolic, and given by the Equation 5.2.

73

Figure 5.3 Reinforcement steel stress-strain relationship

74

Figure 5.4 Concrete stress-strain relationship

75

Figure 5.5 SIMCON stress-strain relationship

76

where fct is tensile stress, fct! is tensile strength equal to { fc! /10 }, gt is tensile strain, got is the

strain at which tensile strength is attained and taken equal to 0.02%.

Table 5.1 Cross section configurations used in the analysis

Cross section reinforcement

Section designation (see Figure 5.2) SIMCON jacket thickness

SQ11 SQ1 8#7 1 inch (25.4 mm)

SQ12 SQ2 8#7 1 inch (25.4 mm)

SQ13 SQ1 8#10 1 inch (25.4 mm)

SQ14 SQ2 8#10 1 inch (25.4 mm)

SQ21 SQ1 8#7 2 inches (50.8 mm)

SQ22 SQ2 8#7 2 inches (50.8 mm)

SQ23 SQ1 8#10 2 inches (50.8 mm)

SQ24 SQ2 8#10 2 inches (50.8 mm)

CIR11 CIR 8#7 1 inch (25.4 mm)

CIR12 CIR 8#7 1 inch (25.4 mm)

CIR21 CIR 8#10 2 inches (50.8 mm)

CIR22 CIR 8#10 2 inches (50.8 mm)

BI11 BI1 8#7 1 inch (25.4 mm)

BI12 BI2 8#7 1 inch (25.4 mm)

BI13 BI1 8#10 1 inch (25.4 mm)

BI14 BI2 8#10 1 inch (25.4 mm)

BI21 BI1 8#7 2 inches (50.8 mm)

BI22 BI2 8#7 2 inches (50.8 mm)

BI23 BI1 8#10 2 inches (50.8 mm)

BI24 BI2 8#10 2 inches (50.8 mm)

#7 bar = 7/8 inch (22 mm) nominal diameter; #10 bar = 10/8 inch (32 mm) nominal diameter;

Column reinforcement is typically Grade 60 steel conforming to ASTM 615 standard

(ASTM, 2002). The reinforcement steel stress-stain relationship is given by Equations 5.3.a,

b, and c.

77

(5.3.c)

(5.3.a)

(5.3.b)

where F is stress, g is strain, E is elasticity modulus equal to 29000 ksi (200 GPa), gy is the

yield strain equal to 0.025%, fy is the yield stress equal to 60 ksi (414 MPa), gsh is the initial

strain hardening strain equal to 0.5%, Esh is the elasticity modulus at the beginning of strain

hardening equal to 1100 ksi (7,584 MPa), fu is the maximum stress equal to 90 ksi (621

MPa), and gu is the ultimate strain equal to 9%.

SIMCON stress-stain relationships under compression and tension are given in

Appendix A. Since the purpose of the analysis is to determine the criticality of several

factors, only one volume of fibers (Vf) was used in analysis. In this study, material properties

of SIMCON with a fiber volume, Vf of 5% was used. It was assumed that for strengthening

a column, the maximum benefit could be achieved using a SIMCON jacket which has the

highest practicable strength.

The characteristic tensile values of SIMCON used in analysis are; the 28 day ultimate

tensile strength, Ftu, equals 2300 psi (15.9 MPa), the strain at the maximum stress, gtu, equals

78

1.12%, and the tensile elastic modulus, Et, equals 3400 ksi (23.4 GPa). The characteristic

compression values are; the 28 day ultimate compressive strength, Fcu, equals 11000 psi (75.8

MPa), the strain at the maximum stress, gcu, equals 0.58%, and the compressive elastic

modulus, Ec, equals 3610 ksi (24.9 GPa).

5.3.5 Assumptions for Structural Modeling

In this study, the following assumptions are made;

1) plane sections remain plane after loading, i.e. strain distribution is linear across

the section,

2) the stresses in concrete, steel and SIMCON can be computed from appropriate

stress-strain diagrams,

3) perfect bond exists between the reinforcing steel and the concrete,

4) the concrete fails in compression at a strain of 0.3% (ACI 318, 2002),

5) any concrete strength increase due to spiral reinforcement and SIMCON jacketing

confinement can be conservatively neglected,

6) the concrete tensile strength is taken into consideration, and tensile strength is

assumed to be 10% of compressive strength,

7) transverse shear deformations can be neglected, that is no shear failure precedes

bending failure or axial compression failure, and

8) only a gradually increasing, static load occurs.

79

(5.4)

5.4 OVERVIEW OF ANALYTICAL METHODS

Conventional, commonly employed structural models were used in the analysis of

members. Since the purpose of this study was to identify and evaluate the effects of

construction factors on behavior, the use of simple, well established models is appropriate.

In this section, the basis for these models and analytical procedures are reviewed. The

analyses were conducted using two programs written and developed by the author to

determine the moment-curvature and axial load-moment interaction behavior of SIMCON

jacketed reinforced concrete columns.

5.4.1 Moment-Curvature Analysis

The moment-curvature diagrams were prepared using a successive approximation

approach based on strain compatibility and equilibrium. Strain compatibility means that the

stress at any point on the cross-section must correspond to the strain at that point. The

equilibrium is satisfied by balancing the internal forces with the external forces acting on the

member. Curvature, n, is calculated as given in Equation 5.4 (Timoshenko and Young,

1968).

where g is the strain at a distance d from the neutral axis as shown in Figure 5.6, at a given

load.

The following steps are followed for calculation of moment-curvature for a simple

80

Figure 5.6 Curved beam-column and curvature, n = g / d

81

(5.5)

(5.6)

(5.7)

reinforced concrete section (MacGregor, 1997; Park and Pauley, 1975):

a) Assume a strain value, gc for the extreme compression fiber of the concrete as

shown in Figure 5.7.

b) Assume an initial x', the distance from the extreme compression fiber to the

neutral axis.

c) Find the strains in each reinforcement steel at a distance di from the extreme

compression fiber by using the Equation 5.5.

d) Determine the stresses in reinforcement steel. Calculate the tensile forces, TR and

the compressive forces, CR on each reinforcement using Equations 5.6.

e) Using the appropriate stress-strain diagrams, compute the concrete compression

force, CC and tension force, TC by Equations 5.7 and 5.8, respectively.

82

Fig

ure

5.7

Rei

nfor

ced

conc

rete

bea

m-c

olum

n cr

oss

sect

ion,

str

ains

and

int

erna

l fo

rces

83

(5.8)

(5.10)

(5.11)

f) Check equilibrium of internal forces by Equation 5.9,

CC + CR = TC + TR (5.9)

g) If equilibrium is not satisfied, choose another x' value and follow steps from (b)

through (f).

h) When equilibrium is satisfied, the internal resisting moment is determined by

multiplying the internal forces by their distance from the cross-section centroid as given by

Equations 5.10 through 5.14.

Moments of internal forces in the reinforcement can be found using Equation 5.10.

Moments of compressive and tensile internal forces in concrete are found using

Equations 5.11 and 5.12, respectively.

84

(5.12)

The internal resisting moment of the section is found by summing the above

moments, as shown in Equation 5.13,

M = MCC + MCR + MTC + MTR (5.13)

i) Determine the curvature using Equation 5.4.

5.4.2 Application of Moment-Curvature Analysis to Available Test Data

Moment-curvature analysis was used by Krstulovic [1997] to predict the behavior of

SIMCON-reinforced concrete composite beams. The method described in Section 5.4.1 was

applied to test data provided by Krstulovic [1997]. Figures 5.8.a and b show the comparison

of Krstulovic’s test data and analytical results. As shown in Figure 5.8.a, the analytical

prediction is very similar to the experimental results. The specimen with the SIMCON

placed at the bottom of the section behaved as predicted up to the point where the SIMCON

debonded. After debonding and the loss of the contribution of the SIMCON, the moment

capacity dropped rapidly. A reliable prediction of the load at debonding should not be

expected due to the large number of factors affecting it, such as the surface roughness,

adhesion and friction between surfaces, for which little, if any, accurate data exists.

When the SIMCON is placed on top of the section as shown in Figure 5.8.b, the bond

85

Figure 5.8.a Comparison of experimental and analytical moment-curvature diagramsof reinforced concrete-SIMCON composite beams (Krstulovic, 1997)

86

Figure 5.8.b Comparison of experimental and analytical moment-curvature diagramsof reinforced concrete-SIMCON composite beams (Krstulovic, 1997)

87

forces may be increased due to induced friction under the load. Debonding was reported to

occur soon after the flexural capacity of the composite beam was reached (see Figure 5.8.b).

Likewise, when SIMCON was placed on three sides of the beam in a U-shaped

configuration, no debonding was reported. Therefore, it may be concluded that the shape of

SIMCON and loading conditions are important for bonding capacity to develop.

Maximum moments ratios between predicted and observed behavior were 13% and

14% for SIMCON placed on the compression zone or in a U-shaped configuration,

respectively. These differences may originate from slight differences in SIMCON material

properties. In the analysis, the SIMCON tensile and compressive strength values given by

Krstulovic were used, although these values are not necessarily exactly the same as those of

the tested materials since the reported values were the average tensile and compressive

strengths for a given fiber volume. Since the results are conservative, however, the analytical

model appears to be appropriate. For the comparison of design and construction factors in

this study, the results using conventional analytical techniques appear to be adequate.

5.4.3 Column Axial Load-Moment Interaction Diagrams

The following procedure was used to determine axial load-moment interaction curves

for columns using the requirements of strain compatibility and equilibrium.

a) Assume the strain value for concrete extreme compression fiber as 0.3% (ACI-

318, 2002) as shown in Figure 5.9,

b) Assume a value for x', the distance from the extreme compression fiber to the

neutral axis,

88

Figure 5.9 Calculation of axial load-moment values for aSIMCON jacketed, reinforced concrete columnsecton

89

c) Calculate strains and stresses in the reinforcement and concrete,

d) Determine the compressive and tensile forces in each material from their stress-

strain relationships as explained in moment-curvature procedure,

e) Sum up Pn using the Equation 5.14,

Pn = CC + CR + TC + TR (5.14)

f) Compute the internal resisting moment, Mn by multiplying the internal forces by

their distance from the centroid of cross-section as given by Equation 5.15, and

Mn = MCC + MCR + MTC + MTR (5.15)

g) Construct the axial load-moment interaction curve by varying the neutral axis

location and computing the resulting Pn and Mn values.

5.4.4 The Effects of Tolerances on Reinforced Concrete Section Behavior

The analytical procedures for determining moment-curvature and axial load-moment

interaction diagrams were used for reinforced concrete columns without a SIMCON jacket

to establish acceptance criteria for the evaluation of factors for a SIMCON jacketed column.

The cross sections in Table 5.1 and materials properties given in Section 5.3.4 were used.

Tolerances must be established for concrete strength as with any other specified,

measurable quantity. ACI 318 [2002] provides acceptance criteria for concrete. These

90

acceptance criteria effectively establish tolerances for the compressive strength of concrete

(Cutshall, Leming, and Johnston, 1999). If an individual test strength falls 500 psi (3.4 MPa)

below the specified value of fc! when fc! is 5000 psi (34.5 MPa) or less, then the Engineer of

Record must ensure that the load-carrying capacity of the structure is not jeopardized. Using

this acceptance criteria as the strength tolerance and applying it to the columns used in this

study, the effects of a strength reduction of 500 psi, or at least 10% of the compressive

strength of the concrete could be compared.

ACI 318 (ACI, 2002) gives the strength reduction factor for columns as 0.65 at the

design stage. For the evaluation of existing structures, a strength reduction factor of 0.8 is

appropriate for columns, if the dimensions of the column and the characteristics of the

materials, including the strengths of the concrete and the reinforcement, have been

established. Therefore, an 80%-65%=15% reduction in strength of the element, as designed,

is attributable to variation in material properties and dimensional control. Since the

contributions of dimensional tolerances are relatively minor for the columns, the primary

factors contributing to the difference in the strength reduction factors are material variation

(Cutshall, Leming and Johnston, 1999). Since the yield strength of the steel routinely

exceeds the specified value (Park and Pauley, 1975), much, although certainly not all, of the

difference in the strength reduction factor in practice is often attributable to concrete material

variation.

Significantly, when the strength value to be used in this calculation is based on core

tests, the core strengths, after any adjustment for length to diameter ratio, are further adjusted

as provided in ACI 318, Section 5.6.5.4, that is, with a 15% addition to the average measured

91

strength value. Considering these factors, a 15% reduction in strength was used as the lowest

reasonable strength tolerance for this investigation. Clearly this is not a complete or rigorous

analysis of safety factors or tolerances. These factors do, however, indicate that a 10%

strength tolerance is conservative and a 15% strength tolerance is very reasonable for the

purposes of comparing the effects of routine construction variation of SIMCON jackets to

conventional concrete columns, and therefore determining whether a particular construction

or design effect is critical, important or appears to be within expected values.

Another important comparison was developed using the dimensional tolerances for

columns given in ACI 117 (ACI, 1990) and tolerances on placement of longitudinal

reinforcing steel taken from ACI 318, Chapter 7 (ACI, 2002). Since these tolerances are

used to help control variation in construction, they also can be used to help establish the

effects of routine variation in construction. The tolerances used are appropriate for the

column sizes used in this study. Reinforced concrete columns should be constructed to

within -3/8 in (-10 mm) (ACI 117, 1990). Reinforcement should be placed within “d-1/2 in”

(d-13 mm) (ACI 318, 2002).

To evaluate the effects the axial load and maximum moment capacities of the

sections with the strength equal to design value and zero tolerances were determined. The

results were provided in Appendix C for all cross-sections, and for all investigated variables.

Then these values were compared to the values obtained for the sections with the given

tolerances. The ratios were then averaged for all the sections and tabulated as shown in

Table 5.2. The values show the increase (with a plus sign) or decrease (with a minus sign)

in capacities in percent. The biggest effect on axial load capacity is the decrease in

92

compressive strength of concrete (11% reduction). The decrease in column dimensions

causes a reduction of 3.5% axial load capacity. These are clearly expected because the

column axial load capacity is directly related to concrete compressive strength and the area

of concrete.

The maximum moment ratios are more sensitive to the variations in reinforcement

placement and concrete strength. The effects of reinforcement placement and concrete

strength tolerances cause 5.8% and 3.1% reductions in maximum moments, respectively.

The area of the concrete does not have a large effect on maximum moment.

Table 5.2 The Effects of Tolerances for Reinforced Concrete Column

Maximum MomentRatio (Mo,max)

Axial Load CapacityRatio (Pn,max)

Concrete strength tolerance,

0.85fc!

average !3.1 !11

maximum -4.8 -12.2

minimum -1.6 -9.7

Dimensional tolerances,

!3/8 in. (!10 mm)

average !0.8 !3.5

maximum -3.6 -4.0

minimum 0.1 -2.8

Reinforcement placement,

d!1/2 in. (d!13 mm)

average !5.8 0.1

maximum -7.4 0

minimum -2.9 0.3

Total of averages -9.8 -14.4

Combined effects of tolerances -9.9 -13.3

"d" is the distance between the most compressed fiber and the bottom reinforcement

These tolerances can occur simultaneously, so that their combined effects were also

93

given in Table 5.2. Using only these three minimal, and conservative effects, assuming

linearity, variations in the load carrying capacity of the SIMCON jacket, due to construction

and design effects, or construction tolerances, should be such that the moment capacity

(Mo,max) of the SIMCON jacketed column is not reduced by more than about 10% and the

axial load capacity (Pn,max) of the SIMCON jacketed column is not reduced by more than

about 15%, the effects may be considered to be within expected variation.

5.5 ANALYSIS OF THE BEHAVIOR OF SIMCON JACKETED REINFORCED

CONCRETE COLUMNS

The effect of SIMCON strengthening on the behavior of reinforced concrete column

was determined before the evaluation of the construction factors using Pn-Mn and Mo-n

diagrams. These diagrams improved the understanding of structural behavior but the primary

purpose was to provide a reference for comparing the effects of construction factors in

subsequent analysis.

These diagrams were determined by assuming that the SIMCON jacket was perfectly

bonded to the reinforced concrete column. At a construction site, the perfect bonding

assumption may hold true at least up to service load level due to the expected shrinkage of

SIMCON and also expected friction between SIMCON and concrete due to irregularities in

their surfaces. Perfect bond between the reinforced concrete beam and the SIMCON jacket,

resulting in a composite action with no slippage, is shown in Figure 5.10. This composite

action arises from the fact that the cross section of a composite member whose sections

consist of different materials behaves as a single plane if sufficient compatibility exists along

94

Fig

ure

5.10

Per

fect

bon

d be

twee

n re

info

rced

con

cret

e an

d S

IMC

ON

95

(5.16)

(5.17)

(5.19)

the interface of two materials.

In the perfect bond case, strains in the reinforced concrete and the SIMCON jacket

are determined as shown in Figure 5.11. Internal compressive and tensile forces generated

in the SIMCON are given in Equation 5.16 and 5.17, respectively. Also, equilibrium must

be satisfied, resulting in Equation 5.18.

CC + CR + CSIMCON = TC + TR + TSIMCON (5.18)

The internal resisting moments produced by the SIMCON jacket are given by

Equations 5.19 and 5.20 for compressive and tensile internal forces.

96

Fig

ure

5.11

Per

fect

ly b

onde

d se

ctio

n st

rain

s an

d in

tern

al f

orce

s

97

(5.20)

Consequently, the total internal moment can be found by Equation 5.21.

M = MCC + MCR + MTC + MTR + MC,SIMCON + MT,SIMCON (5.21)

The ratios of maximum moment (Mo, max) values of bonded SIMCON jacketed

sections to reinforced concrete sections with varying thicknesses of SIMCON are shown in

Figure 5.12. For the given cases and based on the analysis, the SIMCON jacket would

greatly improve the maximum moment capacity. This improvement is highly dependent on

the thickness of SIMCON jacket. With a 2 in. (51 mm) thick SIMCON jacketing, the

maximum moment capacity of the existing reinforced concrete increases approximately two

times or more. With a 1 in. (25 mm) thick SIMCON, however, the maximum moments

appears to increase by 30% to 70% of the maximum moments achieved by the existing

reinforced concrete sections. Figure 5.12 shows also the effects of cross section type on

maximum moment capacity increase. As seen from the figure, there is little difference in

results between square, circular, and biaxially loaded square sections, as expected. The

analysis indicates that the moment capacity increase of SIMCON jacketed circular sections

may be relatively less than that of square sections, however. This may be explained by the

98

Figure 5.12 Reinforced concrete section capacities are compared to perfectlybonded SIMCON jacketed section capacities

99

relatively greater area of SIMCON which contributes more tensile and compressive forces

on the top and bottom of square sections than those of circular section. The maximum

moment with zero axial load (Mo, max) increase provided by the SIMCON jacket is related

mostly to the SIMCON tensile capacity. The maximum moment (Mo, max) is increased by the

additional tensile forces of the SIMCON jacket.

Axial load-moment (Pn-Mn) interaction diagrams for representative SIMCON

jacketed square and circular sections are shown in Figures 5.13 and 5.14, respectively. The

addition of the SIMCON jacket would, of course, improve the axial load capacity of both

square and circular sections. In the square section, shown in Figure 5.13, the axial load

capacity provided by 2 in. thick SIMCON is roughly equal to the axial load capacity provided

by 1 in. thick SIMCON, as expected. Similar results were found for circular section axial

load and moment capacity (see Figure 5.14). There are slight differences between the square

and circular sections, however.

For two different thicknesses of SIMCON jacket, the parallelism below the balanced

axial loads shown for circular section was not observed for the square section columns. The

explanation for this behavior is related to the differences in reinforcement ratios. The square

section has a low reinforcement ratio compared to the high reinforcement ratio of circular

section. Since the reinforcement ratio is low, the SIMCON tensile capacity is reached

quickly in the square section. In the circular section with the high reinforcement ratio,

however, the SIMCON tensile capacity is not reached quickly because the reinforcement

continues to provide additional tensile forces to match the additional compression force

provided by the SIMCON. Therefore, while the capacity increase in columns with a circular

100

Figure 5.13 Axial load-moment interaction diagram: square column

101

Figure 5.14 Axial load-moment interaction diagram: circular column

102

section with high reinforcement ratio and with 1 in. to 2 in. thick SIMCON jackets is roughly

equal, it is not so for columns with a square cross-section.

The axial load capacity (Pn,max) ratios of SIMCON jacketed sections to reinforced

concrete sections are shown in Figure 5.15. With a 2 in. (51 mm) thickness of SIMCON, it

may be possible to reach more than one and a half times the axial load capacity of the

reinforced concrete sections used in this study, alone, although the increase in axial load

capacity may be only approximately 30% with a 1 in. (25 mm) thick SIMCON jacket.

These results were anticipated. No unexpected behavior was uncovered in the

analysis. This and routine program verification checks indicated that the programs were

sound, the structural models appeared to be appropriate, and the results could be used for

comparison of the construction effects.

5.6 RESULTS OF EVALUATION OF SELECTED CONSTRUCTION FACTORS

5.6.1 Bond Between SIMCON and Reinforced Concrete Column

The unbonded SIMCON jacketed section should behave similarly to an unbonded

beam (see Figure 5.16). In this case, unlike in Figure 5.10, shear forces do not exist on the

contact surfaces because the reinforced concrete and the SIMCON react to loads

independently. The law of superposition was used to determine the moment-curvature of the

unbonded section (Kozak, 1991). This superposition requires two additional assumptions

to the general procedure described in Section 5.5: (a) the distribution of strains throughout

the depth of reinforced concrete and SIMCON jacket is linear as shown in Figure 5.16, and

(b) the reinforced concrete and the SIMCON jacket have equal deflections, that is, the

103

Figure 5.15 Axial load capacity ratios of SIMCON jacketed sections to reinforcedconcrete sections

'~,---------------------------------,

0

~1 , " 0 ~ 0 , , , TI ~

" "'1.4 , c c

V c c •

•

c

c c .

V

V V

•

v V

V V

c square

• circular

V

biaxial

"~--------------+---------~~~ SIMeON thickness=1 in SIMeON thickness=2 in

104

Fig

ure

5.16

No

bond

bet

wee

n re

info

rced

con

cret

e an

d S

IMC

ON

105

curvatures are the same in both members at all points along their length at all times.

The first step in determining the moment-curvature of the unbonded section is the

calculation of the M-n curves for both the reinforced concrete and the SIMCON jacket

separately, as shown in Figure 5.17. Then, the final moment-curvature curve for the

unbonded section is obtained by adding the moments of the reinforced concrete and the

SIMCON jacket together at the same curvature values, as shown in Figure 5.18.

Representative square and circular sections of perfectly bonded and unbonded

moment-curvature (Mo-n) relationships are shown in Figures 5.19 and 5.20, respectively.

Analysis indicates that there may be only a slight difference in the behaviors of bonded and

unbonded sections, at least up to service load levels. As seen from the figures, the failure of

the bonded square and circular sections will occur at greater ultimate curvature values than

would happen with an unbonded SIMCON jacket. For both square and circular sections,

analysis indicates that the maximum moments (Mo,max) achievable with unbonded sections

are close to but slightly less than those with bonded sections. The difference between

maximum moments obtained with unbonded and bonded jackets is greater for columns with

square cross-section than for the columns with a circular cross-section, however. The greater

ductility with the square cross-section, bonded SIMCON jacket system is due to the

utilization of reinforcement yielding coupled with the increased compression capacity

provided by the SIMCON.

The difference in moment-curvature behavior (Mo-n) of the unbonded square and

circular cross-sections shown in Figures 5.19 and 20 is due to differences in the behavior of

the SIMCON elements. The behavior of the SIMCON hollow box (~) is not identical to the

106

Fig

ure

5.17

Str

ains

and

int

erna

l fo

rces

for

non

-com

posi

te S

IMC

ON

jac

kete

d re

info

rced

con

cret

e se

ctio

n

107

Figure 5.18 Superposed moment-curvature of unbondedsection

D Unbonded SeCb()1

/ /

/

,-----,+0 Reinforced Concrete

SIMeON

Unbonded section

a Reinforced concrete

~ ------. ,/~

.. " "\" .. ... /

.. " " .............. ,....... SIMeON

,

Curvaure, !p

108

Figure 5.19 Unbonded and perfectly bonded cases of square section

109

Figure 5.20.a Unbonded and perfectly bonded cases of circular section with lowreinforcement ratio

110

Figure 5.20.b Unbonded and perfectly bonded cases of circular section with a highreinforcement ratio

111

SIMCON hollow tube (±). Analysis indicates that the SIMCON hollow tube is more ductile

than the hollow box although their moment capacities (Mo,max) are essentially the same. This

can be explained by the tensile forces provided by these sections. With the hollow box,

when the area at the bottom of section ruptures under tension, it causes a sudden reduction

in the area providing the tensile forces. With the hollow tube, the reduction in area under

tension is more gradual, therefore, the maximum moment is achieved at greater ductility.

The moment-curvature behavior of the composite member, assuming an unbonded condition,

is therefore directly related to the behavior of the SIMCON jacket.

The maximum bending moment (Mo,max) ratios of unbonded sections to bonded

sections for all cross sections are shown in Figure 5.21. As seen from the figure, the ratios

are similar for a given cross section. The unbonded square sections may achieve only

approximately 85% of moment capacity (Mo,max) of the bonded sections, while that ratio is

more than about 90% for circular and biaxially loaded square sections. Moment-curvature

analysis indicates that bonding is not critical for circular sections but likely to be important

for square sections. The average losses in maximum moment ratios (Mo,max) are 7.8% for 1

in. (25 mm) SIMCON jacket and 10.2% for 2 in. (50 mm) SIMCON jacket. The difference

is due to the greater bonded maximum moment capacity achieved with the 2 in. (50 mm)

thick SIMCON jacket when fully bonded.

These maximum moment ratios are equal to or less than those obtained with

reinforced concrete sections which had a 10% loss in maximum moment capacities. Since

the moment capacities achievable with an unbonded jacket are approximately the same as

with the allowable effects of construction tolerances on reinforced concrete, it may be

112

Figure 5.21 Maximum moment ratios of unbonded sections to those of perfectlybonded sections

113

concluded that the bonding effect is not critical for maximum moment capacities.

The axial load capacities (Pn,max) of unbonded and bonded SIMCON jacketed section

should be the same, as long as there is no gap left between the SIMCON jacket ends and the

slab at the top and bottom of the column. Since the axial load capacity (Pn,max) is the sum of

stress times the areas of contributing materials in both cases, the axial load capacity ratios

(Pn,max) of the unbonded SIMCON jacketed sections to the bonded sections may be taken

equal to one.

It is reasonable to anticipate the behavior of the SIMCON jacketed sections in the

field to lie between the two extremes of perfectly bonded and perfectly unbonded behavior.

Perfectly bonded composite action requires horizontal shear transfer between the reinforced

concrete and the SIMCON. Although in the analysis of the unbonded section, it was

assumed that no bond exists, in reality there may be some bond between SIMCON and

reinforced concrete due to adhesion or induced friction in part due to SIMCON shrinkage and

roughness of the interface. Adhesion and friction can function only up to some load level

so that a mechanical shear connector would be required to ensure perfectly bonded composite

action. Since the bond between the concrete and SIMCON is not critical in an axially loaded

column, the use of drilled in shear studs or other type of mechanical shear connectors is not

recommended in order to avoid any damage caused by those in concrete.

Another possible disadvantage of a perfectly bonded jacket is due to the effects of

drying shrinkage of the SIMCON. If the SIMCON jacket is perfectly bonded to existing

concrete which has already undergone shrinkage, the shrinkage of the SIMCON will be

restrained and cause unnecessarily high tensile stresses in the SIMCON jacket, creating

114

cracking.

Although the effect of unbonded behavior in axial load capacities (Pn,max) can be

ignored provided that there is no gap between SIMCON jacket end and slab, in practice all

columns are designed to carry some moment, meaning that SIMCON jacketed column also

should be designed to carry some moments. Unbonded behavior, however, causes a loss in

moment capacities (Mo,max) ofapproximately 10%, which is within the limits established in

Section 5.4.4. Therefore, an unbonded behavior of the SIMCON jacket may be assumed

since bonding of the SIMCON causes additional cost and concerns with the reliability of

bonding mechanisms in a bonded jacket. On the other hand, since the unbonded design

computations are more time consuming than the bonded design, the possible losses in load

carrying capacities can easily and best be handled by conducting a bonded design using a

strength reduction factor. A recommendation for a strength reduction factor will be provided

after evaluation of other critical factors.

5.6.2 Removal of Load on an Existing Reinforced Concrete Column Prior to Jacketing

When a SIMCON jacket is applied in the field, it may not be feasible or advisable to

remove the load on the existing reinforced concrete member. The effect of this factor on

design and construction was evaluated by examining the behavior of the SIMCON jacketed

column with different levels of compression strains in the existing concrete.

For service load levels, the stress does not exceed the elastic limit of the concrete

which typically occurs at 40 to 45% of the ultimate compressive strength, and occurs at

around 0.04% strain assuming a parabolic stress-strain curve. While a parabolic shape is

115

often assumed to ease computation of strain at various stresses, the true stress-strain behavior

of concrete is more complex. The elastic strain in the concrete at the end of the elastic range

is generally close to 0.02% (Park and Pauley, 1975; Neville, 1997). Assuming a 0.04% strain

provides a conservative result.

For the first level of existing strain, creep of concrete and SIMCON shrinkage effects

are considered together. Concrete undergoes a long term creep effect under constant

loading. It is not unrealistic to assume that the creep strains are equal to about 0.01% for a

typical column in service for more than five years (Park and Pauley, 1975). Therefore, the

concrete strain may be reduced to approximately 0.03% at service load levels. When the

SIMCON jacket is applied, this is the likely compressive strain in the concrete, hence this

was studied as the first level of this factor.

It may also be assumed that the SIMCON jacket experiences a longitudinal shrinkage

strain equal to 0.03% which is comparable to the shrinkage of SIFCON (Balaguru and Shah,

1992). Assuming a reasonable bond between the SIMCON and concrete at these relatively

low stress levels, due to radial shrinkage, this shrinkage strain may be added to the existing

concrete strain of 0.03%. A second level of 0.06% residual compressive strain was chosen.

For the third level, a limit value of 0.75fc! was chosen. At this limit, concrete begins

to disintegrate (Park and Pauley, 1975). This stress corresponds to approximately 0.1%

strain for conventional strength concrete. Therefore, 0.1% compressive strain was chosen

as the third level.

Figure 5.22 and 5.23 show the effect of 0.1% existing strain on reinforced concrete

on moment curvature curves for square sections and for circular sections, respectively, as

116

Figure 5.22 Moment-curvature of square section with initial strain of 0.1%

cc No initial concrete strain

CC \

~

/ /' , C "" V Concrete initial

,

rj strain is 0 1 %

C ~

If C:-" / Reinforced

concrete on~ W

>1 SI~CON t- 2

C

C CO " curvature (1/in)*1000

117

Figure 5.23 Moment-curvature of circular section with initial strain of 0.1%

No ini; ial , concrete strain 7/

~ ,

/ / Initial concrete ~

/ / strain is 0 1 %

,

0 '-V Reinforced , conc i ete on~

SIj'lCON t- 2 C

cc

0 z

CC " l' " 0 0

CC 0

curvature (1/in)*1000

118

examples. In these figures, moment-curvature (Mo-n) curves, including the existing load

when the SIMCON jacket is applied, are compared to curves without an existing load. As

seen from the figures, the maximum moment capacity (Mo,max) is approximately the same in

both cases.

Figure 5.24 shows the maximum moment ratios (Mo,max) for jacketed members with

and without initial preloading strains. Analysis indicates that the biggest decrease in

maximum moments occurs with an initial strain of 0.1%. The effects of 0.03% and 0.06%

strain levels are relatively close to each other and are approximately 96% of the maximum

moments (Mo,max) achievable with unloaded reinforced concrete.

The effect of existing strains on axial load capacity ratios (Pn, max) are shown in Figure

5.25. Similar to Mo, max ratios, the biggest effect occurs with an initial strain of 0.1%.

It is reasonable to assume that most of the applications involving a SIMCON jacket

will be in retrofit situations, and, the existing strains should not reach more than about

0.04%. Therefore, it should not be necessary to jack up the slab and relieve the existing

column load. If the column has undergone considerable loading, it may be advisable to

relieve the load prior to application of the jacket, however. If this is not feasible or desired,

the effects on the pre-existing loads must be considered in the design; the resulting stress

conditions for the concrete and the reinforcing steel can be important and must be

investigated.

5.6.3 The Effects of Routine Strength Variations of SIMCON

All construction materials exhibit variations in properties, and the SIMCON slurry

119

Figure 5.24 Maximum moment ratios of the sections with an initial existing strains

120

Figure 5.25 Effect of initial strain on axial load capacity ratios

121

may attain a lower strength than assumed in the design as a result of either routine, random

variation or assignable causes during construction. The reasons for this may include, but are

not limited to, improper batching, mixing, placing or curing procedures. The slurry used in

the SIMCON jacket is a relatively high strength, but homogeneous material. Slight

differences in water/cement ratio would have a disproportionate effect on strength compared

to conventional concrete. Guidelines for using high strength concrete (ACI 363, 1992) are

appropriate, as a minimum. The effects of variation in material properties on the behavior

of the SIMCON jacket were examined to determine if SIMCON jackets were more sensitive

to routine strength tolerances than other typical reinforced concrete elements.

In order to determine the sensitivity of SIMCON jacketing to variations in strength,

a 15% strength reduction was selected. As discussed in Section 5.4.4, a 15% reduction

would be routine under conventional construction controls. Since the SIMCON uses a high

strength slurry, a 10% strength reduction is also selected as a minimum level consistent with

ACI 318 (2002). Therefore, the effects of both 10% and 15% strength reductions were

investigated.

The maximum moment (Mo, max) ratios are shown in Figure 5.26. As seen from the

figure, the maximum moments are proportional to the strength of SIMCON. On average, 6%

to 9% loss in maximum moment was found with 1 in. thick and 2 in. thick SIMCON jackets,

respectively, with a 10% strength reduction of the SIMCON slurry. Using a 15% strength

reduction, 9% and 13% losses were found for the 1 in. thick and 2 in. thick SIMCON jackets,

respectively. Comparing these maximum moment (Mo,max) results to those obtained with the

total effects of tolerances for reinforced concrete column, shown in Table 5.2, the 15%

122

Figure 5.26 Effects of SIMCON routine strength variations on maximum moments

123

strength reduction in SIMCON strength appears to be acceptable.

Axial load capacity (Pn, max) ratios are shown in Figure 5.27. A loss of axial load

capacity was found with reduced SIMCON jacket strength. The losses in average were 3%

for 1 in. thick SIMCON to 5% loss for 2 in. thick SIMCON for a 15% reduction in strength.

In comparison to the reinforced concrete column, shown in Table 5.2, the losses in axial load

capacities of SIMCON jacketed column appears to be acceptable when the SIMCON jacket

has only 85% of design strength.

Since the columns are designed to carry axial load, the use of 15% strength reduction

for SIMCON slurry is recommended as a minimum limit, however, considering all the other

critical factors, a greater strength reduction factor can be recommended at the conclusions

of this chapter. Also, it is not unreasonable to assume that the retrofit project is conducted

one column at a time, so that the slurry for each column will constitute one batch. Therefore,

one batch-one column testing may be acceptable for testing of slurry strength. As with ACI

318, acceptance criteria may be established as 0.90 fc!.

5.6.4 The Effect of Routine Variations in SIMCON Thickness

The effect of routine variations of SIMCON thickness were examined using several

thickness levels. These levels were chosen as 10% and 20% reductions and 10% and 20%

increases in the original SIMCON jacket thicknesses. These levels were chosen as

reasonable variations encountered in construction practice and to examine the sensitivity of

thicknesses on load carrying capacities. Of course, for load carrying capacities the lower

limits, that is, thinner SIMCON jackets, are more important than the upper limits.

124

Figure 5.27 Effects of SIMCON routine strength variations on axial load capacityratios

125

The lower limit of reduction in thickness was chosen as 20% because it is reasonable

to assume that the thickness of fiber mat may not be reduced more than this due to difficulty

in compressing the fiber mat during construction. With a simple test, consisting of clamping

the mat between two plates and measuring the thickness obtained, it was found that, on

average, the mats could be pressed in to 40% of their original thicknesses. After

compression, when released the fiber mat returns to its original thickness. Although it was

found that the mat could be compressed up to 40%, this value was not used in analysis

because considerable pressure is required to achieve this degree of compaction, and would

not be developed in practice without extraordinary means. In addition, overall thickness

control, discussed below would preclude this degree of compaction.

It was assumed that, the strength of the SIMCON with a compressed mat up to 20%

was reasonably close to a strength of a SIMCON with uncompressed mat. Also, since the

purpose of this study was to examine the sensitivity of column behavior to different levels

of factors, the chosen levels should be adequate for this purpose. This finding does indicate,

however, that additional steps will be required during construction to ensure adequate control

of thickness of the fiber mat.

The effects of SIMCON thickness variations on maximum moment ratios (Mo,max) are

shown in Figure 5.28. As expected, analysis indicates that any increase or decrease in

SIMCON jacket thickness will cause an increase or decrease in maximum moments,

respectively. For example, a 10% decrease in thickness causes approximately 6% loss in

maximum moments. The critical factor, of course, is the 20% reduction in thickness. A

reduction in thickness of 20% reduces the maximum moments by about 12%. The moment-

126

Figure 5.28 Effects of SIMCON thickness variations on maximum moments

127

curvature analysis also indicates that increased thickness causes an increase in flexural

moment capacity (see Figure 5.28), approximately 10%, which was not considered at the

design stage. This increase in flexural capacity may attract more loads to a jacketed column

when subjected to certain type of loading and, therefore, may cause an unanticipated type of

failure.

Axial load capacity ratios (Pn,max) affected by thickness variations are shown in Figure

5.29. The figure indicates that an axial load capacity loss of 7% on average occurs if the

thickness is reduced 20%.

The maximum thickness tolerance (20%) used in this part of the study corresponds

to approximately 1/4 in. for 1 in. thick SIMCON and approximately 3/8 in. for 2 in. thick

SIMCON jacket. The dimensional tolerances for reinforced concrete columns are !3/8 in. for

columns having a dimension greater than 12 in. (ACI 117, 1990). The effects of the !3/8 in.

tolerance for reinforced concrete column was shown to produce a 3.5% loss in axial load

capacity and 0.8% loss in maximum moment capacities (see Table 5.2). The effects of

thickness tolerances on SIMCON jacketed column capacities appears to be far greater than

the effects of thickness tolerances on reinforced concrete capacities which is not unexpected.

This can be explained by the difference in concrete and SIMCON strengths. Since the

SIMCON jacket is much stronger and thinner than the concrete column, any variations in

strength or in thickness cause a more profound effect on the behavior of SIMCON jacketed

column.

The important effect of thickness tolerance and the possibility of extreme

compression of the fiber mat can be controlled relatively easily at the construction site,

128

Figure 5.29 Effects of routine variations in SIMCON thickness on axial load capacityratios

129

provided that attention is given to the SIMCON thickness prior to slurry injection. The

thickness of the SIMCON mat can be maintained with a simple procedure, such as inserting

a thin steel rod through the fiber mat at the injection holes prior to slurry injection and

measuring the distance between concrete surface and the formwork at several locations.

Once any adjustments have been made, the fiber mat can be injected with a slurry. Although

this method provides quick assurance, it does not guarantee the occurrence of non-

conformities due to statistical variations, therefore a reduced strength factor in design can be

employed. Although the effects of thickness variation can be estimated reasonably well, and

controlled reasonably simply, due to the difficulty in achieving the necessary accuracy on

site, a control limit of 20% reduction in thickness is more appropriate for SIMCON jackets

equal and less than 2 in. thick and 10% reduction in thickness for SIMCON jackets more

than 2 in. thick. Since the determination of the strength reduction factor depends on not only

the variations in thickness but also other effects, such as the variation in strength, the

appropriate strength reduction factor to be used for the design of SIMCON jacketed columns

is discussed later in this chapter after reviewing the effects of other factors.

5.6.5 The Effect of Displacement of the SIMCON Jacket During Construction

Examples of non-concentrically located SIMCON jackets are shown in Figure 5.30.

Since the voids will be filled with slurry in all cases, this results in a difference in thickness

of the SIMCON jacket, which would also affect the volume of fibers, Vf , somewhat and

could therefore affect the SIMCON characteristics. These effects in Vf can be ignored,

however, since the compression strength of the slurry would not change and the total quantity

130

Figure 5.30 Non-concentrically placed SIMCON jacketaround reinforced concrete member

t: thickness o f SIMCON jacket lOp of th e sections are th e m ost compressed part

131

of steel is not changed, so the tensile capacity of the jacket would not be affected.

Different SIMCON thicknesses were considered at different longitudinal locations

to investigate their effect on SIMCON jacketed member behavior (see Figure 5.30). Two

distinct cases with two levels were examined. One of the cases involves compression of the

SIMCON jacket at the top of the section where the concrete is subjected to compression. In

that case, the SIMCON jacket is thinner than specified at the top of the section. The other

case represents the opposite of the first case, that is, the SIMCON jacket is compressed and

became thinner at the bottom of the section where the concrete is the least compressed. The

thickness levels were chosen to represent the similar conditions outlined in Section 5.6.4.

Both cases were examined using 10% and 20% reductions in the thickness of the compressed

SIMCON jacket section.

The maximum moment ratios (Mo,max) are shown in Figure 5.31. As seen from the

figure, the maximum moments vary within a range of 2% and are 0.3% in average. The

effects are very small; the scatter of results may be attributed in part to the precision of

analytical results.

Axial load capacity ratios (Pn,max) are shown in Figure 5.32. The axial load capacity

ratios are within the range of 0.3%. Even in the most extreme cases, 80% variations in

placement location, the effect is approximately 5%.

The effects of eccentric placement, where the SIMCON jacket is not centered

precisely, may be ignored as long as the differences do not result in a change of thickness

greater than 20%. Comparing this finding to the results obtained in examing thickness alone,

it is clear that the critical element in construction is to control the thickness. The method

132

Figure 5.31 Effects of non-concentric placement of SIMCON on maximum moments

133

Figure 5.32 Effects of non-concentric placement of SIMCON on axial load capacity ratios

134

to check the thickness of fiber mat should also provide the necessary control of concentric

placement of fiber mat by satisfying the same thickness of the mat all around the reinforced

concrete column.

5.6.6 Effects of SIMCON Seams

SIMCON is commercially available as rolls as shown in Figure 2.4. When applied

in-situ, columns can be jacketed longitudinally, along the perimeter, or spirally with these

rolls. In any of these procedures, the edges of rolls can introduce a line of weakness as

shown in Figures 5.33.a and 5.33.b. The effect of seams was represented in this analysis by

using a lower material properties along that portion of SIMCON. To investigate the effect

of seams, the following assumptions were made: (a) the SIMCON seam has an effective

width (the width of the weakness) of 4 in. (100 mm), (b) along the weak line, the

compressive and tensile properties of the SIMCON are assumed to be 90% and 85% of their

respective design strengths as discussed in Section 5.6.3. The selection of the width of seam

was based on previous work conducted by Krstulovic [2001] and assumed to be a reasonable

balance between not affecting the behavior of a column too much and minimizing the

amount of fiber mat used on the seam line, that is doubling the fiber mat used in the seam

area. Since the fiber mat volume is doubled, the slurry infiltration of fibers in this region

may become troublesome and therefore some parts may not be infiltrated by slurry causing

reduced strength at the seams.

In this study, SIMCON seams were presumed to be placed along the long axis of the

reinforced concrete column as shown in Figure 5.33.a. If the SIMCON rolls are placed

135

Figure 5.33 Fiber mat seam locations on a SIMCONjacketed column

~",W//h '0 W/////'W//////fi

I; I I

I I I I I "'I I I I I I I I

Fiber m at seam

ow". • ,,) SIMeON roll '5 placed

longitud inall y around a co lumn

" WY///////-W'//////////h

I : I I r· I .~ I I ,

7' I , I I I

Fib ermatseams

I : ~ w/,w//////////////, "

b) SIMeON roll is placed as d iscreete rings around a column

136

spirally around the column, as shown in Figure 5.33.b, then it can be assumed that those

seams may become critical section and these sections may be analyzed similar to the section

investigated in Section 5.6.3. As shown in Figure 5.34, seams will be located on the

compression side, on the tension side, and in the middle.

The effects of lower strength seams on maximum moments (Mo,max) are shown in

Figure 5.35. If the seam has 90% strength of specified, then the loss in maximum moments

may reach 2%. The loss in maximum moments may be 5% in average, however, if the seam

strength is only 85% of the specified strength and if the seam is at the tension side. Figure

5.35 shows the effect of seam location on maximum moment ratios (Mo,max). The maximum

moments will be affected most by the seams located on the tension loaded part of SIMCON.

The effects of seam strengths on axial load capacities (Pn,max) are shown in Figure

5.36. Analysis indicates that, if the seam has 90% of the specified strength, then the loss in

axial load capacities may reach 0.6%. The loss in axial load capacity will be even lower,

1.2%, if the seam strength is 85% of the specified strength. The axial load capacities may

be most affected by the seams located on the compression area of the SIMCON.

Analysis indicates that the existence of SIMCON seams has very little effect on axial

load capacities. The presence of seams on the tensile side of SIMCON jacket, however, may

cause some significant effect on maximum moment capacities (Mo,max), if the seam has only

85% strength. Although analysis indicates that seam strength is not critical for axial load

capacities, clearly, the expansion of existing concrete under compression, and increased

ductility under certain loading conditions may cause tensile forces perpendicular to seams

and separation of the seams. One possible solution to increase the tensile capacity of seams

137

Figure 5.34 Analyzed fiber mat seam locations on a SIMCONjacketed column when SIMCON is placedlongitudinally

R"; rf orced co"",", _,

SIMeON jacket ~ __

~) SI MeON seam is on side

b) SI MeON seam is on cOOlp;essi rn side

c) SI MeON seam is on tensi rn side

"f' is SIMeON j;.cket thickness

138

Figure 5.35 Effects of SIMCON seams on maximum moments

139

Figure 5.36 Effects of SIMCON seams on axial load capacity ratios

140

(Eq. 5.22)

(Eq. 5.23)

is sewing the ends of fiber mat rolls together with a tie wire. Since the model did not address

this type of failure, conservative approach is suggested and additional research is

recommended to investigate the separation of SIMCON seams under these conditions.

5.6.7 Thin Wall SIMCON Jacket

Because SIMCON will be applied as a thin member around a concrete section, local

buckling of the SIMCON under compressive load may occur, leading to a premature failure.

The local buckling would appear as a localized failure in the form of a wrinkle or indentation

on the compression side of the SIMCON jacket subjected to bending (Timoshenko, 1961).

Local buckling of thin plates and thin shells under uniform compression in the axial

direction were investigated by Timoshenko [1961], assuming that the local buckling behavior

of elastic materials has a sine-wave shape. He provides estimates of the critical buckling

stress for thin plates and thin shells as given by Equations 5.22 and 5.23 respectively.

where E is the elasticity modulus, < is Poison ratio, t is thickness, b is width, and r is radius.

An inspection of Equations 5.22 and 5.23 reveals that resistance to local buckling is

a function of the diameter-to-thickness or width-to-thickness ratio and independent of the

141

length of the column. The local buckling effect increases as the diameter or width-to-

thickness ratio increases (Cook, 1999; Troitsky, 1982).

Equations 5.22 and 5.23 were applied to thin SIMCON shells. Although SIMCON

is not a precisely elastic material (see Figure 5.5), by adapting a strain limiting criteria the

sensitivity to likelihood of buckling can be assessed using linear elastic methods.

Application of these formulas to SIMCON jackets are given in Figures 5.37 and 5.38 for

circular and square sections, respectively. As seen from Figure 5.37, for a circular SIMCON

jacket with diameter-to-thickness (D/t) ratios greater than 380, the critical stress becomes

lower than the SIMCON compressive strength. For a square SIMCON jacket the critical

stress becomes lower than SIMCON compressive stress for the width-to-thickness (b/t) ratios

of greater than 33 as shown in Figure 5.38.

When the critical buckling stress becomes lower than the compressive strength, it is

likely that SIMCON tube or box will buckle locally. Assume that as a minimum, 1 in. (25

mm) thick SIMCON is used for the strengthening of the column sections used in this study.

For the circular column, the diameter-to-thickness ratio of SIMCON jacket would be 18 in./1

in. =18. For the square column, the width-to-thickness ratio of SIMCON jacket would be

16 in./ 1 in. =16. Since these column sizes are typical for buildings, the minimum likely

thickness of a SIMCON tube would not cause a thin wall buckling. However, with the ratio

of 16 very close to 33 for a SIMCON box, it may be possible to see some thin wall buckling.

The likelihood of buckling will be increased by the reduction in thickness, and non-

concentric placement of SIMCON. If the thickness of SIMCON reduced 20% due to the

routine variations then the width-to-thickness ratio for the square column becomes 16 in./0.8

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Figure 5.37 Thin wall circular SIMCON tube local buckling critical stress

143

Figure 5.38 Thin wall square SIMCON box local buckling critical stress

144

in. =20. This width-to-thickness ratio is closer to critical buckling stress as seen in Figure

5.38.

Since the SIMCON is a thin box or tube subjected to axial compression, the designer

should be aware of the possible thin wall buckling of the SIMCON jacket. In order to

mitigate the possibility of the thin wall buckling problem, the SIMCON jacket thickness may

need to be increased to reduce the width/diameter-to-thickness ratio for a given situation.

In this study, no minimum thickness of SIMCON jacket was recommended against the

possibility of the thin wall buckling problem because the given minimum thickness may not

satisfy the required width/diameter-to-thickness ratio for larger cross-sections. Since at the

design stage, the thin wall buckling problem can be avoided by selecting appropriate

SIMCON dimension, it can be concluded that the thin wall buckling is not a critical factor.

5.6.8 SIMCON Jacket End Connections

As seen in the previous sections, SIMCON jacketing may greatly enhance the axial

load-moment capacity of column sections. In order to achieve those enhancements, however,

the continuity of the load transfer from the SIMCON jacket to the reinforced concrete beam

or slab must be ensured. For this reason, the transfer of tensile forces and compressive forces

in SIMCON jacket to the existing frame or slab must be addressed.

Krstulovic, et al, [2000] and Dogan, et al, [2000] investigated the seismic behavior

of reinforced concrete beam-column connections by continuous jacketing with SIMCON.

Their research involved strengthening a newly constructed, cross shaped (\) joint. In the

actual frames, however, the joints have three or more beams and a slab connecting to it.

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Thereby, although continuous jacketing with SIMCON seems to be capable of transferring

the loads, the constructibility of such system in actual frames will be very labor intensive and

costly.

A balanced failure of SIMCON jacketed section is assumed to occur when the

reinforcement yields in tension and the concrete reaches its maximum strength in

compression. The compressive strength of concrete used in slabs and beams in many

buildings may be assumed to be approximately 4000 psi (27.6 MPa), while the compressive

strength of SIMCON ranges between 9500 to 11000 psi (65.5 to 75.8 MPa). In this case,

since SIMCON has a much higher compressive strength than the concrete in the beam or

slab, the compression load in SIMCON jacket may cause crushing of the slab or beam at the

point of contact with the SIMCON jacket.

If the compressive strength of the SIMCON jacket is fully utilized, then the stress in

the concrete on which the SIMCON jacket is seated must be reduced to acceptable levels.

Therefore, to distribute the compression load from the SIMCON jacket, a pedestal or capital,

an extension of the SIMCON jacket, should be included, as shown in Figure 5.39.

In addition to axial loads, the end moments of the SIMCON jacketed column should

also be transferred from the SIMCON jacket to the reinforced concrete slab, beam or footing.

Some sort of connection must exist between the end of the SIMCON jacket to transfer the

tensile forces in SIMCON. Conceivably, this connection may be satisfied with epoxy

grouting, a thickened edge or using steel collars, or placing dowels in the concrete slab before

placing the SIMCON jacket.

As an example of a connection an epoxy grouting procedure given here may be

146

Figure 5.39 Epoxy grouted gap between SIMCON jacket pedestaland slab

147

followed. While constructing the SIMCON jacket, a narrow gap may be left intentionally

between the SIMCON pedestal and the concrete slab by placing a foam strip and after curing

of the SIMCON, removing the foam strip. After curing of SIMCON jacket, this gap may be

enclosed with a reusable form and injected with a Type IV epoxy (ASTM C882, 2002) to

bond SIMCON jacket to concrete slab. Nevertheless, considerations should be given to the

possible effects of fire to the epoxy, creep of epoxy, and shearing effect on epoxy. Type IV

epoxy is specified to be used in load bearing applications for bonding hardened concrete to

hardened concrete. The minimum bond strength of this type of epoxy is specified as 1000

psi (7 Mpa) and the compressive strength is specified as 10000 psi (70 MPa) (ASTM C882,

2002). Using these values and considering the tensile and compressive strengths of

SIMCON, the determination of required area of the pedestal is straight forward.

Although the design of the SIMCON jacket end connections were found to be critical

factor, their design requires the necessary design values to be known. The design is,

however, outside the scope of work for this study, which was to identify critical factors in

design or construction, develop reasonable methods to control these factors and to prioritize

research needs where solutions were not feasible or design conditions were not known with

sufficient accuracy. Clearly the design and behavior of the end connections are critical

research needs.

5.7 SUMMARY OF ANALYTICAL EVALUATION

5.7.1 Summary of Analytical Evaluation of Selected Factors

The results of analytical evaluation of selected factors are provided in Table 5.3. In

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the table, the average values of analyzed sections were presented. The results were given for

two different SIMCON thicknesses because the behavior of the column is generally strongly

affected by the SIMCON thickness. The investigated factors were arranged by their effects

on column behavior.

In the table, the unbonded to bonded axial load capacities are not given but are equal

to one. This is closely related to the end conditions of the SIMCON jacket, however.

Therefore, the end connections appear to be the most important factor because of their effect

on load transfer mechanism. Although some possible solutions were discussed, the end

connection details require more detailed investigation regarding constructibility and their

effects.

The data in Table 5.3 indicate that the next most critical factor was thickness of the

SIMCON jacket. The variations in the SIMCON jacket are found to be important for the

maximum moments and axial load capacities, therefore they should be closely monitored at

the construction site. Thickness of the SIMCON jacket should be checked at several point

around the section and along the column. This procedure not only assures uniform thickness

but also should ensure the concentric placement of SIMCON, and should be employed to

verify the thickness prescribed in the specifications. Thin, steel rod may be inserted through

the form and the fiber mat and the distance from concrete surface to the surface of the fiber

mat measured. The slurry injection port openings may be used for access through the form.

The routine variations in SIMCON strength are the next important factor on

maximum moments (Mo,max) and axial load capacities (Pn,max) as seen in Table 5.3. The

strength of the slurry should be closely monitored. Based on findings in 5.6.3 and

Table 5.3 Statistical evaluation of selected analytical results

149

PARAMETERMAXIMUM MOMENT

RATIO (Mo,max)AXIAL LOAD CAPACITY

RATIO (Pn,max)

t=1 in t=2 in t=1 in t=2 in

Improvement in reinforced concrete due to bonded jacket 52.0 119.6 28.9 62.5

Bonding (perfectly bonded/unbonded) -7.8 -10.2 0* 0*

Thickness variations thickness is 80% -7.9 -13.3 -4.8 -8.6

thickness is 90% -4.1 -7.0 -2.4 -4.4

thickness is 110% 4.2 7.2 2.5 4.5

Strength tolerances strength is 90% -3.3 -5.1 -1.9 -3.2

strength is 85% -5.8 -9.1 -2.8 -4.7

Removal of existing load prestrain is 0.03% -4.4 -3.0 -1.7 -6.0

prestrain is 0.06% -5.5 -4.7 -2.0 -6.0

prestrain is 0.1% -8.2 -8.4 -2.7 -9.1

Non-concentric placement top thickness is 90% -0.2 -0.4 -0.2 -0.3

top thickness is 110% 0.2 0.3 0.3 0.4

top thickness is 80% -0.1 -0.3 -0.4 -0.6

top thickness is 120% 0.5 1.3 0.5 0.9

Fiber mat seams seam at top strength 90% -0.4 -0.7 -0.3 -0.6

seam at top strength 85% -2.6 -1.9 -0.6 -1.0

seam at side strength 90% -0.5 -0.4 -0.3 -0.5

seam at side strength 85% -3.0 -2.6 -0.5 -0.8

seam at bottom strength 90% -0.8 -1.3 -0.3 -0.5

seam at bottom strength 85% -4.4 -5.2 -0.5 -1.0

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summarized in Table 5.3, the use of 10% strength acceptance criteria, as currently required

in ACI 318 for high strength concrete is acceptable.

The presence of existing loads on the column during jacketing appears to be an

important factor for the behavior. The cost of SIMCON jacketing will increase due to

jacking if the removal of existing loads is chosen to benefit the capacity increase, although

this increase in capacity would be marginal compared to routine variations in SIMCON

strength and thickness. Therefore, it is recommended that the SIMCON jacket be applied

without removal of existing loads, with the loss of capacity incorporated in the design phase.

The effects of routine variations in centering of SIMCON are within established range

of the effects of dimensional tolerances on the reinforced concrete column.

The effects of SIMCON seams with reduced strength are within the limits established

in 5.4.4. The potential problems include separation of seams due to barreling of jacket and

rotation of unreinforced fractured edges in compression. Stitching of the fiber mat edges

may provide a possible solution for these problems, additional research is recommended,

however.

5.7.2 Modification of Strength Reduction Factor for SIMCON Jacketed Column

ACI 318 [2002] gives strength reduction factors (N) to compensate for the

uncertainties in estimation of strength of structural members. The strength reduction factor

for a column with reinforcement other than spiral is given as 0.65 in Section 9.3.2 of ACI

318. The suitability of this factor for SIMCON jacketed columns needs to be addressed.

The effects of some factors investigated in this study are small, however, several are

151

significant, such as the effects of thickness variations and strength tolerance. Although

thickness control can be easily established in the field with a gauge and strength can be

maintained by testing, due to the relatively large effects caused by these factors, which could

occur simultaneously, it would appear prudent to adopt a more restrictive strength reduction

factor until sufficient research has been conducted.

The total of losses for thickness tolerance of 80%, strength tolerance of 85%, the

assumption of existing strain in the column as 0.06%, and the biggest effects of other factors

were divided by the axial load capacity increase in the jacketed reinforced concrete column.

Based on the results in Table 5.3, the axial load capacity loss ratio to total capacity increase

in reinforced concrete with 2 in. thick SIMCON jacket is

and with 1 in. thick SIMCON jacket is

These are equivalent to strength reduction factors of 0.67 and 0.63, respectively. These

results indicates that the axial load capacities of SIMCON jacketed columns with the applied

tolerances will achieve only about 65% of the axial load capacity over the axial load capacity

of the reinforced concrete jacketed with a SIMCON. Similar ratios were also found for

reductions in maximum moment capacities.

Based on these ratios, the strength reduction factor (N), 0.65 given in current ACI 318

152

for columns could be used as a minimum for the design of SIMCON jacket. Considering the

other factors, however, such as uncertainties in end connections, and seam behavior which

need future research, and the importance of columns in structures, it may not be unreasonable

to use a more conservative strength reduction factor such as 0.60, pending additional

research.

5.8 CONCLUSIONS AND RECOMMENDATIONS

1. Analysis indicates that the SIMCON jacket may greatly improve the maximum moment

capacity of a reinforced concrete column; increases of one and a half times or more of the

original reinforced concrete section capacity were found for typical SIMCON thicknesses and

. Based on analysis, SIMCON thickness plays an important role in axial load capacities.

With 2 in. (51 mm) thickness of SIMCON jacket applied on the column types used in this

study, it may be possible to reach more than one and half times the axial load capacity of

reinforced concrete section itself.

2. The following factors in design of SIMCON jacketed columns were identified and

evaluated:

a) Bond Between SIMCON and Reinforced Concrete Column: There does not appear

to be a significant difference in axial load capacities of bonded and unbonded section

provided that there is no gap left between the SIMCON jacket and slab. Therefore, an

unbonded SIMCON jacket can be used for strengthening due to additional cost by bonding

of the SIMCON and concerns with the reliability of bonding mechanisms in a bonded jacket

b) SIMCON jacket end connections: The end connections appear to be the most

153

important factor because of their effect on load transfer mechanism. Although some possible

solutions were discussed, the end connection details require more detailed investigation

regarding constructibility and their effects.

c) Removal of load on existing reinforced concrete column prior to jacketing:

Analysis indicates that the presence of existing loads on the column during jacketing is an

important factor for the behavior. It is recommended, however, the SIMCON jacket may be

applied without removal of existing loads, with the loss of capacity incorporated in the

design phase with an appropriate strength reduction factor because of the increased cost of

the SIMCON jacketing with jacking and backshoring.

d) Thin wall buckling of SIMCON jacket: The SIMCON jacket is a thin box or tube

subjected to axial compression, so that there is a possibility of thin wall buckling of the

SIMCON jacket. The thin wall buckling problem can be avoided, however, at the design

stage by selecting appropriate SIMCON dimensions, therefore it was concluded that the thin

wall buckling is not a critical factor.

3. The following factors in construction of SIMCON jacketed columns were identified and

evaluated:

a) Routine variations in SIMCON strength: Analysis indicates that the use of 10%

strength acceptance criteria, as currently required in ACI 318 for high strength concrete is

acceptable for the routine variations in SIMCON strength. It is recommended that the

strength of the slurry should be maintained by testing.

b) Routine variations in SIMCON jacket thickness: Based on analysis, the variations

in the SIMCON jacket were found to be important for the maximum moments and axial load

154

capacities, therefore they should be closely monitored at the construction site.

c) Non-concentric placement of the SIMCON jacket during construction: Based on

analysis, the effects of routine variations in centering of SIMCON are within established

range of the effects of dimensional tolerances on the reinforced concrete column.

d) The effects of location and strength of fiber mat seams: The effects of SIMCON

seams with reduced strength are within the limits established for the effects of dimensional

tolerances on the reinforced concrete column. There are potential problems with seams,

however, including separation of seams due to barreling of jacket and rotation of

unreinforced fractured edges in compression. Therefore, additional research is

recommended.

4. The strength reduction factor, (N), 0.65 given in ACI 318 for reinforced concrete columns

may be used as a minimum for the design of SIMCON jacket. It may not be unreasonable,

however, to use a more conservative strength reduction factor such as 0.60 for SIMCON

jacketed column design considering the uncertainties in end connections and seam behavior,

which need additional research, and the importance of columns in structures, pending

additional research.

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CHAPTER VI

COMPARISON OF ALTERNATIVE STRENGTHENING

TECHNIQUES AND COST ANALYSIS

6.1 OVERVIEW

The utility of any material, element, device or configuration depends on both

economical and technical feasibility. In this chapter, the economic viability of a SIMCON

jacket, applied as a retrofit to an existing column, is compared to several other widely

available alternatives. These alternatives are not exactly equivalent technically. The increase

in moment capacity of the FRP alternative (Teng, et al, 2002) is not the same as that

provided by the SIMCON jacket, for example. In addition, costs are very site specific in

terms of working conditions, site location and access, and technical specifications, to name

just a few factors. Only an approximate comparison of costs, ir order to determine economic

feasibility, was required, therefore, a detailed cost estimate was neither necessary nor

possible.

Since no estimates of in-place costs of SIMCON jacket were available, a simple

analysis was considered which could be used to determine the general economic feasibility

of the SIMCON jacket, in comparison with the very broad cost estimates of alternatives

156

available in the literature or quoted in practice. It is significant to note that the cost estimate

could be prepared only after identifying those critical elements of design or construction

which would significantly affect behavior and which would therefore affect construction

requirements. As an example, the lack of a requirement to ensure bonding between the

jacket and the column means that no cost was involved, in material or in on-site fabrication,

for this particular aspect.

Typical technically similar alternatives for strengthening a column include;

a) Confinement by jackets made of

- SIMCON,

- Steel,

- Fiber Reinforced Plastics (FRP), or

- Reinforced concrete (RC)

b) Demolishing the existing reinforced concrete column and building a new

reinforced concrete column.

c) Strengthening not the individual member but the structure by adding a steel tube

or an additional column next to the existing member, reducing the load on the existing

column and increasing the capacity of the structure.

6.2 CONFINEMENT BY JACKETS

Wrapping is an effective method in confining concrete, increasing the usable

compressive strength of both the concrete core and cover regions of the columns, resulting

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in a greater load carrying capacity with a higher strain capacity at failure. It also provides

additional support against buckling of the longitudinal bars in the original column. Cost

estimates of these alternatives are given in 6.3.4.

6.2.1 Steel Jackets

Confinement by various types of steel elements, including strand, hoops and plates

formed into tubes, has been shown to be effective in enhancing the ductility of reinforced

concrete, allowing the seismic performance of concrete members to be upgraded (Yuping,

et al, 2000). Although the ductility is increased, the axial load capacity does not change

significantly due to the small area (the cover over the existing column) confined by the steel

elements. Another major concern in using steel jackets is the potential for corrosion; other

concerns include intentional or accidental damage to the strand in service, and behavior of

steel under high tensile stress during a fire.

Xanthakos [1996] gives examples of confinement of reinforced concrete bridge

columns by steel hoops as shown in Figure 6.1. In this application, concrete is confined by

prestressing the steel hoops with a special turnbuckle. In another application, steel jackets

were used to strengthen a reinforced concrete column as shown in Figure 6.2 (Xanthakos,

1996). The steel shell is welded around the column and the annular space between the

column and the steel jacket is filled with grout.

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Figure 6.1 Column retrofit to increase confinement with steelhoops (Xanthakos, 1996)

159

Figure 6.2 Column retrofit using steel plate encasement(Xanthakos, 1996)

We lded joint

· - ·· l ·· - ·~Ex.istin g . ori gin a l

rei nforce d I concrste co lum n

I

+ ____ Ne w stse l Jad<et

Grout filled space

•_--- bet ww n column it-- and steel Jacket

ELEVATION

'--... ,.."" Annula r space fill ed wi t h grout

~ Stesl jackst

Sectlcn A-A

Original B"is ting rein forced con cre t e co l um n

160

6.2.2 FRP Jackets

Fiber Reinforced Polymer (FRP) jackets are made by wrapping fibers around the

columns and providing an epoxy coating. These jackets are either (a) in-situ fabricated

jackets that involve hand (see Figure 6.3) or automated machine placement (see Figure 6.4)

of epoxy saturated fabrics on the surface of the existing concrete or (b) prefabricated

composite jacketing shells, applied similarly to steel jackets.

Considerable research has been conducted on FRP strengthening of reinforced

concrete structures (ACI 440, 1996). The disadvantages of FRP typically cited include;

a) lack of universally accepted design procedures,

b) high material cost,

c) vulnerability to mechanical damage, and damage by vandalism (although such

damage is more likely to be localized, and repair may be easier than with steel),

d) notch sensitivity,

e) premature failure at corners while wrapping square columns,

f) the use of toxic materials for bonding, requiring more careful storage than

traditional construction materials,

g) low fire resistance of organic binders,

h) degradation of organic binders under ultraviolet light,

i) low durability of glass fibre reinforcement in alkali environments, and

j) potential for increased galvanic corrosion since carbon fiber is a conductor of

electricity and composites in which it is used may be highly noble relative to some metals.

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Figure 6.3 The REPLARK method for polymer composite wrapping ofcolumns (Hollaway and Head, 2001)

162

Figure 6.4 Xxsys Technologies for polymer composite wrapping of columns(Hollaway and Head, 2001)

163

Advantages of FRP include high tensile strength, light weight, ease of handling,

reduced construction period, no corrosion of the fibers, ability to prestress, and lack of

anchor problems (ACI 440R, 1996; Hollaway and Leeming, 1999).

Tests conducted by Chaallal and Shahawy [2000] indicate that FRP wrapping

provides approximately a 70% increase in moment capacity and approximately a 30%

increase in the axial load capacity of columns mainly due to the concrete confinement effect.

There is still a need to develop suitable confining models for FRP wraps. The primary

advantage of FRP wrapped columns is the increased ductility of the column.

6.2.3 Reinforced Concrete Jackets

Strengthening of a reinforced concrete column can be achieved using conventional

reinforced concrete elements. Xanthakos [1996] shows this type of strengthening (see Figure

6.5). With this option, the flexural capacity of the column will be increased, similar to

SIMCON jacketing. Xanthakos draws attention to the necessity of dowels of sufficient

length to develop the required connection strength. Another potential problem is the

shrinkage of the new concrete. Since, as shown in the figure, the new concrete is

mechanically bonded to the old concrete, the new concrete will be prevented from shrinking

and therefore may crack. This cracking, in turn, may cause corrosion of reinforcement.

Using reinforced concrete as a strengthening material may be comparatively cheaper

than others because of familiarity of procedures and availability of materials. Due to the

relatively high thickness of this alternative, a substantial penalty may be incurred by the

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Figure 6.5 Strengthening a column with reinforced concrete jacket(Xanthakos, 1996)

165

owner, however.

In commercial buildings, the lease payment ($ per time period) is based on the lease

rate ($ per square feet) and the usable floor area. The usable floor area is determined as the

gross area less the area of columns, narrow offsets and can include restricted areas such as

dead spots near doors. This factor is, of course, one of the driving factors for the use of high

strength concrete columns in tall buildings in major metropolitan areas. High strength

concrete columns are inherently more expensive per square foot of area occupied than

conventional strength concrete columns. They are economically feasible only when a high

lease rate is charged.

6.2.4 Demolishing the Existing Reinforced Concrete Column and Building a New

Reinforced Concrete Column

In some cases, the existing reinforced concrete column may have been severely

damaged, due to corrosion, frost attack, or excessive loading. In some other cases, the

column might be defective due to construction errors. In these cases, it may not be

economically feasible or technically possible to put a jacket around the column and

strengthen it, and replacement with a new column is required. The existing column loads

will be transferred to temporary shores, and the column will be replaced by a new one. The

potential problems include shrinkage of the new concrete and providing sufficient load and

moment transfer at the end connections. This option is especially attractive for a single

column replacement rather than replacing all floor columns. The familiarity of the design

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procedures and availability of materials is also another appealing factor for this option.

6.2.5 Adding a Steel Tube or Column Next to the Existing Member

Occasionally, a column, deficient due to the reasons given in 6.2.4, may be chosen

to be left in-place but with an additional column added to relieve the loads on existing one.

The reasons for this option may include, but is not limited to, the limited floor area to place

the temporary shores, or to save the time spent while waiting for the curing of the

replacement reinforced concrete column. In that sense, the simplest material will be a steel

tube because it will not shrink and can be installed in a very short time. It is assumed that

this option is performed inside the building where the corrosion problem is minimal,

however, in this case, the fire protection of steel tube should be considered. Another material

for the additional column can be precast reinforced concrete. The advantage of reinforced

concrete column is its fire resistance. Whether steel or reinforced concrete, the load transfer

connections and requirement of footings and removal of floor slab present challenging

problems in design and construction. Another disadvantage is the usable floor space lost to

the additional column in office buildings.

6.3 COST ANALYSIS OF SIMCON JACKETED COLUMNS

Cost estimates are prepared, in general, by estimating labor costs, equipment costs,

which are based on pro-rated capital costs or rental fees, material costs, overhead costs, profit

and contingency. The overhead costs are normally broken down into project management

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and site costs, and general and administrative (G&A) costs, which include the costs of

estimating, billing, non-job-specific insurance or liability costs and primary management

costs. Contingency is often included in overhead costs and, for preliminary estimates or

reporting purposes, the combined overhead and contingency costs, plus profit, are given as

a simple mark-up value.

6.3.1 Assumptions in Estimating Project Management Costs

One of the most variable and difficult to estimate costs for general use is the cost

associated with project management. The costs used in this study were estimated based on

available data. The following considerations are listed by Xanthakos [1996] in developing

these costs for retrofitting columns:

1) The strengthening method is not an emergency repair but a planned decision to

upgrade the structure to a particular level of service, at a particular point and time.

2) If the structure is located in an urban area, additional time constraints and

measures to protect the pedestrians will imply additional costs, including restrictions such

as working hours.

3) The proposed improvement is planned during the prime construction months. If

this is not the case, additional costs mut be allocated to cover contingencies such as proper

curing, weather related delays, and so on.

4) Normal accessability is provided to site.

5) If necessary, the structure can be closed to use.

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6) Removal costs of construction debris are not excessive.

7) Materials and necessary equipment are locally available.

8) The structure is adaptable to the proposed improvement; if heavier loads must be

carried by the columns then modifications of beams and associated elements are possible.

9) OSHA/EPA regulations do not overly restrict operations.

Other factors which can affect the costs include:

1) Costs attributed to a functional deficiency such as load posting or clearance

restriction. Although this is primarily a cost to the owner, or the user, it can also affect the

price quoted by the contractor.

2) A need for sequencing the strengthening considering structural integrity and

safety. Strengthening may need to follow the load path meaning that slabs and beams may

have to be strengthened first followed by columns and finally footings. Again, this is

primarily a cost of retrofitting to the owner which may not be significantly affected by the

specific type of retrofit alternative selected but which could affect the sequence of operations

and access and therefore affect the price quoted by the contractor.

3) Protection of exposed elements during the project may be needed.

4) Characteristics of materials, such as waste and workable life, storage requirements,

shelf life, amount of quantity to be stored, and protective clothing requirements will clearly

affect the cost of materials, the cost of labor and project management costs..

5) Requirements for specially trained crews, particularly when dealing with hazardous

substances.

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6) Degree of repetition or market demand. This is a significant factor in many cases.

Equipment capitalization costs may be spread over more projects, “learning curve” behavior

and crew productivity may increase, costs associated with uncertainty and risk may be

reduced, and, of course, competition in a larger market may reduce prices.

6.3.2 Work Breakdown Structure of SIMCON Jacketed Reinforced Concrete Column

A Work Breakdown Structure (WBS) for strengthening a reinforced concrete column

with a SIMCON jacket was developed composed of two principle tasks:

Task 1: Analytical study and design, which included

Step 1: Analysis of the structure or elements,

Step 2: Selection of the construction system(s) to be used, and

Step 3: Planning and procurement, and

Task 2: Installation of SIMCON jacket, which included

Step 1: Mobilization,

Step 2: Preparation of existing reinforced concrete column,

Step 3: Preparation of steel fiber mat,

Step 4: Preparation and injection of slurry mixture into the steel fiber mat,

Step 5: Curing, and

Step 6: Demobilization, clean-up and close-out.

Work descriptions of these tasks are as follows:

Step 1.1 Structural Analysis: Analyze the jacket, considering the findings of this

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study. Determine the required SIMCON jacket properties and thickness.

Step 1.2 Selection of the construction system(s) to be used: Select the formwork type,

including material and bracing requirements to achieve the required

dimensional tolerances. Assuming that most formwork will be custom built,

it may be feasible to use a round fiber formwork such as SonoTubes®

(Krstulovic, 2001) for circular columns. For rectangular or square column

sections, formwork can be manufactured of steel, plywood, composite or

wood faced metal. Due to the low viscosity and lack of coarse aggregate and

the need for close dimensional tolerances, the formwork should be designed

for full hydraulic head plus pumping pressure.

Step 1.3 Planning and procurement: Procure selected materials including formwork,

steel fiber mat and slurry ingredients. Limited production facilities for the

steel fiber mat, procurement of this material may require a considerable lead

time. Initiate the approval process by the engineer of record.

Step 2.1 Mobilization: Set up the job site, job office, provide necessary access control

or fall protection devices, bring in required equipment, establish access for

utilities, trash disposal and sanitation.

Step 2.2 Preparation of existing reinforced concrete column: It was previously shown

that there is little difference in column behavior between a perfectly bonded

and an unbonded SIMCON jacket. Therefore, no special preparation of the

existing concrete column surface is needed. Nevertheless, cleaning the

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surface of debris, dirt, and any loose concrete should be done as a matter of

good practice.

Step 2.3 Preparation of steel fiber mat: Determine the required dimensions, and cut the

fiber mat. Place the mat around the existing column and hold the mat in-

place around the column using tie wires. Place the formwork around the

column, with access ports for the slurry injection (one at bottom, one at the

middle, and one at the top for a typical, one story column height) (Krstulovic,

2001).

Step 2.4 Prepare the slurry mixture using appropriate quantities of cement, water,

silica sand, HRWR, and silica fume for the column. Mix and inject by

pressure. Vibrate the formwork externally for good compaction.

Step 2.5 Cure the SIMCON jacket: Remove the formwork 36 to 48 hours after slurry

injection and provide acceptable curing such as by applying curing

compound. The time, 36 to 48 hours, in the form is temperature dependent

and is needed due to the retardation commonly encountered using the high

dosages of HRWR used to obtain the low viscosity of the SIMCON slurry

required for infiltration of the mat.

Step 2.6 Demobilization, clean-up and close-out: Clean up the job site. Dismantle and

remove equipment, tools and control devices. Conduct final tasks to ensure

quality. Complete and process required paperwork.

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6.3.3 Cost Analysis of SIMCON Jacketed Reinforced Concrete Column

Cost data was calculated by summing the labor, equipment, and material costs. Most

of the data, including labor hours, equipment, and material usage were estimated based on

previous SIMCON related research conducted at the Constructed Facilities Laboratory

(CFL), at North Carolina State University (NCSU). Whenever possible, costs were taken

from RSMeans Building Construction Cost Data book (RSMeans, 2002), other costs were

obtained from suppliers.

To analyze the costs associated with SIMCON jacketing of a reinforced concrete

column, several additional assumptions were made, in order to compare costs of other

strengthening technologies. Using data obtained from the California Department of

Transportation (CalTrans) for FRP and steel jackets: (a) the reinforced concrete columns to

be strengthened are bridge columns, (b) the columns have dimensions of 25 in by 25 in (635

mm by 635 mm), and are 20 ft (6.096 m) high, and (c) the crew consists of a foreman, two

skilled workers, and a common laborer. Direct labor hour estimates are shown in Table 6.1.

The total of 20 hours shown in Table 6.1 is the estimated labor hours spent by the

crew on one column. The costs for crew members were taken from RSMeans data book

[2002] and included the costs of workers’ compensation insurance and fixed overhead.

Therefore the direct labor costs were calculated as follows:

20 hr× (1×$43.90 + 2×$41.30 + 1×$31.60) = 20 × ($158.10) = $3,162 per column

Table 6.2 shows the estimated equipment costs for SIMCON jacketing of one bridge

column. While these costs appear to be precise, they are very approximate figures based on

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reasonable procedures expected to be employed in a SIMCON jacketing project.

For a single column, the estimated slurry costs are shown in Table 6.3. The slurry

composition was similar to that used by Krstulovic [1999b], as given in Table 2.1, and to the

slurry used in this study in the deicer salt scaling test. The total material costs, used for a

single column jacket, were estimated as shown in Table 6.4. The slurry costs estimated in

Table 6.3 were used to complete Table 6.4.

Table 6.1 Crew Labor Hours

Job descriptions

Crew hours

per column

cleaning concrete column with high pressure water

assume no grease and no paint on column surface

1.5

prepare a dike to hold the contaminated water; prepare water pump;

pressure wash the column; pack the water pump and move

Preparation and placing the steel fiber mat 4

unroll the fiber mat; measure and cut the mat; hold the mat in place

on column and tie it

Formwork 4

assume use rented reusable forms; move forms, clean them; apply

form release; lift, place, and clamp forms; adjust forms and seal

Prepare slurry mixture and inject into the fiber mat 4

Strip forms, clean, and move 1.5

Prepare end connections and install at both ends 3

Clean the workplace 2

Total 20

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Table 6.2 Equipment costs

Description Costs per column

pressure pump to clean the column $5

power tools to cut the mat, to clean, erect, and clean forms $10

hand tools $5

reusable formwork, rented $330

forklift to move and lift the forms $450

scaffolding, rented $100

mixer for slurry $75

grout pump for slurry $75

Total $1,050

Table 6.3 Slurry material costs

Wi/Wc lbs / ft3 lbs per column# $ / lb Costs per column

cement 1 56.00 1477.8 0.08 $118

water 0.31 17.40 459.2 0.01 $5

silica sand 0.6 33.50 884.1 0.10 $88

silica fume slurry* 0.3 16.80 443.4 1.00 $443

HRWR** 0.04 0.06 1.6 1.14 $2

Total $656

# per column volume=20 ft×12×(4×25 in)×2 in thickness = 48,000 in3 = 27.8 ft3;

minus fiber volume; (use Vf =5% ); 0.95×27.8 = 26.39 ft3

* silica fume slurry consists of 49.7% solids

** assume HRWR is 8.8 lb/gal and 10 $/gal, bulk

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Table 6.4 Material costs

Description Costs per column

water to clean column, and a disposal fee $20

steel fiber mat* $227

tie wire $5

slurry (from Table 6.3) $656

end connections made of steel collars, incl. bolts and anchors $100

Total $1,008

* the price of the steel mat was assumed to be 1.00 $/lb based on discussions with

the manufacturer; one roll is 100 ft long and 4 ft wide; one roll weighs

approximately 500 lbs; for one column (20 ft×100/12 ft )×1.05 = 175 ft2 mat

required; one roll is enough for (400 ft2 / 175 ft2) 2.2 columns; 500 lbs / 2.2

columns= 227 lbs mat for one column

Other alternatives for the end connections of SIMCON jacket clearly exists, and this

structural detail needs further investigation (see Section 5.6.8). For the purposes of this part

of the study, an approximate, but representative value of the end connections was needed.

It was assumed that a steel collar, connected to the SIMCON jacket by bolts acting as shear

studs and connected to the concrete slab or beam by drilled anchors, would be used.

With a new technology like SIMCON, it is difficult to estimate overhead accurately

or assign a reasonable profit. General and administrative (G&A) costs include expenses such

as home office expenses, including estimating costs, billing expenses and salaries of the

executives, as well as a non-project-specific insurance costs. The project overhead costs are

related to the job and include job office expenses, storage, site protection, and control

176

expenses, and project engineer and superintendent salaries. Assuming that additional risk

related costs, such as insurance, legal fees and management costs are assigned specifically

to the project, a customary percent of direct costs (labor plus equipment plus materials)

would appear to be reasonable for the purposes of this study. However, in order to be

somewhat conservative, a value of 5% of direct costs, which is slightly high but within the

expected range for a smaller project, was used. It is important to note, however, that this

value was chosen assuming several columns would be retrofitted rather than just one. A

single, isolated column would be more expensive. Since the comparison to be made in the

next section used values based on retrofit of several columns, this assumption is valid.

Assigning all project specific risks to the project overhead and considering the

significant management time of both the project engineer and a superintendent on-site means

that project overhead will be relatively large. In addition, a number of costs not normally

encountered by smaller contractors, working on small dollar value jobs, will be incurred.

The contract will clearly require a performance and payment bond and will probably include

a bid bond. In addition, job risk, assigned directly to the project, even though it may be

covered in the home office coverage, can be expected to be high for this type of work, at least

initially.

Another factor contributing to the project overhead will be the relatively high

management costs anticipated, again at least initially. While these costs are normally

factored in to project overhead estimates, they are separated in this study to simplify the

estimate process. Considering that, at least initially, and being conservative in nature, on a

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job with several columns, the project engineer or superintendent will be required full-time

for each column, and, simplistically, one column can be completed, on average, each day,

the direct cost of management can be estimated as 45 $/hr ×8 hr/day = $360 per column.

It is important to note the difference in price between the project management

engineer and the design fee. The project engineer cost is given directly since overhead and

profit are added separately. The design fee includes overhead, including errors and

omissions insurance, business permits, and office expenses, profit, and routine right-to-build

permits.

After excluding management and risk costs, the other project overhead expenses

appear to be routine. In order to be conservative however, a value of 9% of the direct costs

was used. This is the approximate value that might be expected in building construction,

including supervisory costs, and so is reasonable but conservative.

Total mark-up (overhead plus profit) in many routine, moderate sized, commercial

construction projects varies from about 12% to less than 20%. For smaller jobs, the mark-up

can be higher due to cash flow considerations, but would not exceed 25%, except in highly

risky work, which this is not. The profit in most large project, sealed bid work varies

between 1 and 2%, but profitability, as measured by discounted return on expenditures, is

approximately 10 to 15%, or roughly the value of mark-up. Profit for a small, short-time

construction job is given as 10% of total costs by RSMeans [2002]. For a high risk project

and with little competition, profit could be as high as 15 to 20% (Peurifoy, 1975). Since the

SIMCON jacketing is a new technique, it could be seen as high risk, however the

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construction itself is relatively straightforward and, with a competition expected from

strengthening techniques such as steel jacketing or FRP wrapping, it is not unreasonable to

use 10% profit in the estimate.

These assumptions result in a mark-up of 30% of direct costs of construction. This

value is high, but not completely unreasonable for a small project. Since the intent of this

part of the study was to compare economic feasibility in a very general manner, a

conservative approach is reasonable.

The time estimate for design of the SIMCON jacket was estimated based on analysis

used in this study. The engineering effort will take more time than required for a normal

concrete structure for which readily available design guidelines exist, however, an estimate

of 5 hours was believed to be reasonable. Due to the uncertainty of the estimate, and to be

conservative, one working day (8 hours) was used to estimate the total cost. The engineering

costs for one column is about 15% of total costs, which is not unreasonable, compared to

reinforced concrete design, given the degree of technical knowledge and lack of experience.

The total cost for a SIMCON jacket for a typical column can therefore be broken

down as shown in Table 6.5.

Since these calculations were done for 20 ft high column, for a unit length of column

the rounded approximate cost is $8,000 / 20 ft � $400 / ft (.$1,300 / m). This figure is the

most likely cost for a SIMCON jacketing of a single column. To determine the sensitivity

of the cost, the following calculations were performed:

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Table 6.5 SIMCON jacket costs for the retrofit a single reinforced concrete column

Construction

Direct Labor

Equipment (from Table 6.2)

Material (from Table 6.4)

$3,160

$1,050

$1,010

Subtotal (DL+E+M) $5,220

Overhead (G&A) (5%) $260

Project Overhead (9% + $360) $830

Profit (10%) $520

Subtotal $6,830

Design Fees (8 hours @ 150$/h) $1,200

TOTAL COST: SINGLE COLUMN $8,030

(Figures are rounded to the nearest $10)

The biggest percentage of the total cost is the direct labor costs in Table 6.5. The

direct labor cost is also usually the most variable cost component in a construction project.

Therefore, the direct labor cost of SIMCON jacketing in Table 6.5 is assumed to be doubled,

conservatively. Another variation in cost may be caused by the increase in fiber mat cost

which could be assumed to be doubled, again, conservatively. With these assumptions, the

total cost for a single column SIMCON jacketing is shown in Table 6.6. For a unit length

of 20 ft high column, the likely high cost is approximately $12,230 / 20 ft � $610 / ft

(.$2,000 / m). Therefore, the cost for a typical column SIMCON jacketing may range from

$1,300 per meter to $2,000 per meter.

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Table 6.6 The likely high cost for SIMCON jacketing of a single reinforced

concrete column

Construction

Direct Labor

Equipment (from Table 6.2)

Material (from Table 6.4)

$6,320

$1,050

$1,240

Subtotal (DL+E+M) $8,610

Overhead (G&A) (5%) $430

Project Overhead (9% + $360) $1,130

Profit (10%) $860

Subtotal $11,030

Design Fees (8 hours @ 150$/h) $1,200

TOTAL COST: SINGLE COLUMN $12,230

(Figures are rounded to the nearest $10)

Since the SIMCON jacketing is very new technology at the time of this study, its use

has been limited to laboratory research. Therefore, there has been no reliable cost data for

SIMCON related construction based on field applications. With the acceptance and

increased use of the SIMCON as a strengthening technique, more reliable cost data should

be available for better estimates.

6.3.4 Cost Data of Alternative Strengthening Techniques

Approximate cost data were provided by the California Department of Transportation

for selected bridge column strengthening alternatives (personal communication, 2002);

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1) Carbon fiber jackets for a column or pier cost $1,500 / m for 0.8 m in diameter

to $2,500 / m 1.0 m in diameter in place.

2) Steel shell column casings cost $4/kg - $6/kg complete and in place. In order to

compare the costs, the cost for steel shell casing must be converted to $ per length. To

convert the $ per kg to $ per m figures, CalTrans suggested that each steel casing may be

assumed to be 1/2 in. (12 mm) thick. The steel shell casing costs in this case are $1,000/m -

$1,880/m.

The costs of carbon fiber jacketing and steel shell jacketing alternatives are

comparable to the range of values of $1,300/m-$2,000/m found for SIMCON jacket

suggesting that the SIMCON is an economically feasible alternative.

At the beginning of this chapter, alternatives for strengthening the columns, including

reinforced concrete jacket, replacement, and adding a new column were briefly discussed.

Although these methods appear to be simple and straight forward because of the familiarity

of the materials and procedures, they may present more design and construction challenges

than they solve. In addition, in many cases, they cause a loss of revenue due to lost of usable

floor space because of increased column dimensions or added column. Clearly, the

replacement and adding a new column alternatives are not truly strengthening techniques,

therefore it was not considered for cost comparison.

Among the alternatives, the reinforced concrete jacket may have advantages

comparable to other types of jacketing of a column. The direct labor costs for reinforced

concrete jacketing should be similar to SIMCON jacketing because both procedure involve

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similar crew jobs. The equipment costs can also be expected similar. The only difference

may occur in material costs due to use of ordinary reinforcement steel and ordinary concrete,

although the mixture of concrete used in reinforced concrete jacket should be appropriately

designed so that it can be easily pumped. While the overhead costs can be similar, the design

fees should be lower than that of SIMCON jacketing because of familiar design procedures

for reinforced concrete. Although the costs for reinforced concrete jacket appear to be lower

than other alternatives, these costs may be offset by increased column sizes and therefore

reduced leaseable floor area. Since it was assumed that the alternatives to SIMCON

strengthening are mainly FRP and steel jackets, the cost of concrete jacketing was not

considered.

6.4 CONCLUSIONS

Based upon the costs assumed in this analysis, the SIMCON jacketing appears to

have a reasonable cost compared to other strengthening alternatives.

Considering the technical limitations and possibility of improved moment or axial

load capacity, the SIMCON jacket alternative appears to be economically viable. In

particular, the marginal cost of the additional moment or load capacity may be much lower

than several available alternatives.

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CHAPTER VII

CONCLUSIONS AND RECOMMENDATIONS

7.1 CONCLUSIONS

1. The SIMCON specimens, exposed to freezing-and-thawing cycles in the presence of

deicer salt, exhibited very slight scaling, indicating good to excellent resistance.

2. Air entrainment was not found to be required for satisfactory resistance to deicer salt

scaling, probably due to the very low w/c ratio used.

3. Excellent deicer salt scaling resistance was obtained even though the silica fume content

(13% of total cementitious materials), was higher than the limits (10%) recommended in ACI

318 (ACI, 2002).

4. Based on microscopic analyses on the slurry cubes and SIMCON specimens, excellent

consolidation was achieved with simple gravity infiltration.

5. The lack of entrained air in slurry cubes revealed by microscopic analysis indicates that

much higher additions of air entraining agents are required to provide a high air content with

this mixture.

6. The presence of cracks did not affect deicer salt scaling or corrosion.

7. Corrosion was observed only on fibers which were not embedded, the high quality matrix

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apparently provides satisfactory protection, or passivation, for stainless steel fibers, at least

for the duration (approximately 2 months) of this severe test.

8. Corrosion may at least become a visual problem where the SIMCON is exposed to deicer

salt solutions.

9. Analysis indicates that the SIMCON jacket may greatly improve the maximum moment

capacity of a reinforced concrete column. Based on analysis, SIMCON thickness plays an

important role in axial load capacities. With 2 in. (51 mm) thickness of SIMCON jacket

applied on the column types used in this study, it may be possible to reach more than one and

half times the axial load capacity of reinforced concrete section itself for square column sizes

of 16 in. (410 mm), and circular column sizes of 18 in. (460 mm).

10. The following factors in design of SIMCON jacketed columns were identified and

evaluated:

a) Bond Between SIMCON and Reinforced Concrete Column: There does not appear

to be a significant difference in axial load capacities of bonded and unbonded section

provided that there is no gap left between the SIMCON jacket and slab. Therefore, an

unbonded SIMCON jacket can be used for strengthening due to additional cost by bonding

of the SIMCON and concerns with the reliability of bonding mechanisms in a bonded jacket

b) SIMCON jacket end connections: The end connections appear to be the most

important factor because of their effect on load transfer mechanism. Although some possible

solutions were discussed, the end connection details require more detailed investigation

regarding constructibility and their effects.

185

c) Removal of load on existing reinforced concrete column prior to jacketing:

Analysis indicates that the presence of existing loads on the column during jacketing is an

important factor for the behavior. It is recommended, however, the SIMCON jacket may be

applied without removal of existing loads, with the loss of capacity incorporated in the

design phase with an appropriate strength reduction factor because of the increased cost of

the SIMCON jacketing with jacking and backshoring.

d) Thin wall buckling of SIMCON jacket: The SIMCON jacket is a thin box or tube

subjected to axial compression, so that there is a possibility of thin wall buckling of the

SIMCON jacket. The thin wall buckling problem can be avoided, however, at the design

stage by selecting appropriate SIMCON dimensions

11. The following factors in construction of SIMCON jacketed columns were identified and

evaluated:

a) Routine variations in SIMCON strength: Analysis indicates that the use of 10%

strength acceptance criteria, as currently required in ACI 318 for high strength concrete is

acceptable for the routine variations in SIMCON strength. It is recommended that the

strength of the slurry should be controlled by testing.

b) Routine variations in SIMCON jacket thickness: Based on analysis, the variations

in the SIMCON jacket were found to be important for the maximum moments and axial load

capacities, therefore they should be closely monitored at the construction site.

c) Non-concentric placement of the SIMCON jacket during construction: Based on

analysis, the effects of routine variations in centering of SIMCON are within established

186

range of the effects of dimensional tolerances on the reinforced concrete column.

d) The effects of location and strength of fiber mat seams: The effects of SIMCON

seams with reduced strength are within the limits established for the effects of dimensional

tolerances on the reinforced concrete column. There are potential problems with seams,

however, including separation of seams due to barreling of jacket and rotation of

unreinforced fractured edges in compression. Therefore, additional research is

recommended.

12. The strength reduction factor, (N), 0.65 given in ACI 318 for reinforced concrete

columns may be used as a minimum for the design of SIMCON jacket. It may not be

unreasonable, however, to use a more conservative strength reduction factor such as 0.60 for

SIMCON jacketed column design considering the uncertainties in end connections and seam

behavior, which need additional research, and the importance of columns in structures,

pending additional research.

13. Based upon the costs assumed in this analysis, the SIMCON jacketing appears to have

a reasonable cost compared to other strengthening alternatives.

14. Considering the technical limitations and possibility of improved moment or axial load

capacity, the SIMCON jacket alternative appears to be economically viable. In particular,

the marginal cost of the additional moment or load capacity may be much lower than several

available alternatives.

7.2 RECOMMENDATIONS

187

One of the goals of this study was to identify the research needs before the SIMCON

jacketing is used routinely for strengthening of reinforced concrete columns. Therefore,

based on analysis, the following needs are identified and prioritized:

1. Design and construction of SIMCON jacket end connections.

2. The behavior of SIMCON seams, separation under tension, and buckling in compression.

3. Thin wall buckling behavior of SIMCON jacket.

4. The strength reduction factor, (N),for the design of SIMCON jacket.

5. Reliable cost data for SIMCON related construction based on field construction work

measurements.

6. Durability related to corrosion of fibers in exposure tests.

188

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198

(Eq. A.1)

(Eq. A.2)

APPENDIX A

SIMCON MATERIAL PROPERTIES

A.1 SIMCON TENSILE STRENGTH

The tensile stress-strain relationship of SIMCON before maximum stress is given by

Equation A.1.

where Ftu is the 28 day ultimate tensile strength and gtu is the strain at the ultimate

(maximum) stress. The value of A in Equation A.1 is obtained from Equation A.2.

where Et is the composite elastic modulus.

Some experimentally obtained values of Ftu, gtu, and Et by Krstulovic are given in

Table A.1.

The stress-crack opening relationship of SIMCON after the ultimate (maximum)

tensile stress is given by Equation A.3.

199

(Eq. A.3)

Table A.1. Average values of SIMCON tensile tests (Krstulovic [1997])

Volume of fibers

Vf (%)

Elastic modulus

Et (ksi) [GPa]

Ultimate stress

Ftu (psi) [MPa]

Strain at ultimate stress

gtu (%)

0 2050 [14.1] 175 [1.2] 0.02

2.16 2629 [18.1] 1025 [7.1] 1.003

3.24 2812 [19.4] 1429 [9.9] 1.43

4.31 2947 [20.3] 1760 [12.1] 1.001

5.39 3437 [23.7] 2321 [16.0] 1.122

M' 13 ! 2Vf (Eq. A.4)

* ' h(g ! gtu) (Eq. A.5)

where * is the width of the crack opening, h is the length of specimen, L is the fiber length,

M is an experimentally determined coefficient, and Vf is volume fraction of fibers.

A.2 SIMCON COMPRESSION STRENGTH

The compression stress-strain relationship of SIMCON before maximum stress is

given by Equation A.6.

200

(Eq. A.6)

(Eq. A.7)

where Fcu is the 28 day ultimate compression strength and gcu is the strain at the ultimate

(maximum) stress. The value of A in Equation A.6 is obtained from Equation A.7.

where Ec is the composite elastic modulus.

Some experimentally obtained values of Fcu, gcu, and Ec for injected slurry specimens

by Krstulovic are given in Table A.2.

Table A.2. Specific values to be used in Equations A.6 and A.7 to predict injected

SIMCON specimens’ compression stress-strain response (Krstulovic [1999])

Vf (%)

Ec (ksi)

[GPa]

Fcu (psi)

[MPa] gcu (%)

Fif (psi)

[MPa] gif (%)

Fasy (psi)

[MPa]

2.16 3766

[26.0]

9450

[65.2]

0.44 8000

[55.2]

0.58 3000

[20.7]

4.31 4011

[27.7]

10650

[73.4]

0.51 8660

[59.7]

0.83 4400

[30.3]

5.39 3613

[24.9]

11080

[76.4]

0.58 9000

[62.1]

0.96 5000

[34.5]

201

(Eq. A.8)

(Eq. A.9)

(Eq. A.10)

Fif and gif in Table A.2 are the stress and strain at the inflection point on the

descending portion of stress-strain relation. Fasy in Table A.2 is the asymptotic value of the

compressive stress in the postpeak region.

The stress-strain relationship of SIMCON after the ultimate (maximum) compressive

stress is given by Equation A.8, A.9, and A.10.

202

APPENDIX B

SIMCON SCALING TEST SPECIMENS

203

Fi~re B.2 Spec1men A 12CR -6 aft er scaling r eslSlanc e Ie sl

204

Fi~re B.3 Sp ee1men A 13CR -9 after scaling r eslSlane e les I

205

Fi~re B.4 Spec1men A 14NC-l0 after scaling r eSiStance te st

206

Fi~re B.5 Sp ec1men N21CR-5a aft er scaling reslStance t est

207

o 1 2

Fi~re B.6 Sp eC1m en N22NC-6a aft er scaling r eS! slane e Ie st

208

Fi~re B.7 Sp ec1men N23CR-7a aft er scaling reslStance t est

209

Fi~re B.8 Spec1men N24NC-8a afl er scaling r eslSlanc e Ie sl

210

APPENDIX C

RESULTS OF EVALUATION OF DESIGN

AND CONSTRUCTION FACTORS

Table C.1 The effect of reinforcement placement on maximum moment capacities of reinforced concrete sections

Section designation1: no change2: d-1/2 in.

Mo, max

(kips.ft) Mo, max,2 / Mo, max,1

SQ01 1 151.54

SQ02 1 294.21

SQ03 1 151.48

SQ04 1 289.18

CIR01 1 151.44

CIR02 1 271.75

BI01 1 156.41

BI02 1 259.27

BI03 1 154.18

BI04 1 259.48

SQ01 2 145.36 0.959

SQ02 2 281.51 0.957

SQ03 2 142.37 0.940

SQ04 2 267.81 0.926

CIR01 2 147.11 0.971

CIR02 2 256.63 0.944

BI01 2 145.80 0.932

BI02 2 240.70 0.928

BI03 2 143.25 0.929

BI04 2 240.93 0.929

211

Table C.2 The effect of reinforcement placement on axial load capacities of reinforced concrete sections

Section designation1: no change2: d-1/2 in.

Pn, max

(kips) Pn, max,2 / Pn, max,1

SQ01 1 1443285

SQ02 1 1736969

SQ03 1 1448708

SQ04 1 1736621

CIR01 1 1874788

CIR02 1 2171659

BI01 1 1486669

BI02 1 1773892

BI03 1 1486779

BI04 1 1774472

SQ01 2 1446479 1.0022

SQ02 2 1737042 1.0000

SQ03 2 1451164 1.0017

SQ04 2 1736831 1.0001

CIR01 2 1874730 1.0000

CIR02 2 2171540 0.9999

BI01 2 1488578 1.0013

BI02 2 1777938 1.0023

BI03 2 1489695 1.0020

BI04 2 1780647 1.0035

212

Table C.3 The effect of routine variations in concrete strength on maximum moment capacities of reinforced concrete sections

Sectiondesignation

0: reference1: 0.90fc’2: 0.85fc’3: 0.75fc’

Mo, max

(kips.ft)

Mo, max, 1 / Mo,

max, 0

Mo, max, 2 / Mo,

max, 0

Mo, max, 3 / Mo,

max, 0

SQ01 0 151.54

SQ02 0 294.21

SQ03 0 151.48

SQ04 0 289.18

CIR01 0 151.44

CIR02 0 271.75

BI01 0 156.41

BI02 0 259.27

BI03 0 154.18

BI04 0 259.48

SQ01 1 149.9 0.989

SQ02 1 291.45 0.991

SQ03 1 149.57 0.987

SQ04 1 285.84 0.988

CIR01 1 149.14 0.985

CIR02 1 264.81 0.974

BI01 1 151.9 0.971

BI02 1 250.9 0.968

BI03 1 149.83 0.972

BI04 1 253.17 0.976

SQ01 2 148.92 0.983

SQ02 2 289.4 0.984

SQ03 2 148.74 0.982

SQ04 2 282.32 0.976

CIR01 2 147.93 0.977

CIR02 2 261.46 0.962

BI01 2 149.21 0.954

213

Sectiondesignation

0: reference1: 0.90fc’2: 0.85fc’3: 0.75fc’

Mo, max

(kips.ft)

Mo, max, 1 / Mo,

max, 0

Mo, max, 2 / Mo,

max, 0

Mo, max, 3 / Mo,

max, 0

BI02 2 246.94 0.952

BI03 2 147.21 0.955

BI04 2 249.49 0.962

SQ01 3 146.99 0.970

SQ02 3 286.72 0.975

SQ03 3 147.76 0.975

SQ04 3 274.16 0.948

CIR01 3 145.7 0.962

CIR02 3 254.31 0.936

BI01 3 144.06 0.921

BI02 3 238.09 0.918

BI03 3 142.58 0.925

BI04 3 239.34 0.922

Table C.4 The effect of routine variations in concrete strength on axial load capacities of reinforced concrete sections

Sectiondesignation

0: reference1: 0.90fc’2: 0.85fc’3: 0.75fc’

Pn, max

(kips)

Pn, max, 1 /Pn, max, 0

Pn, max, 2 /Pn, max, 0

Pn, max, 3 /Pn, max, 0

SQ01 0 1443285

SQ02 0 1736969

SQ03 0 1448708

SQ04 0 1736621

CIR01 0 1464783

CIR02 0 1747226

BI01 0 1486669

BI02 0 1773892

214

Sectiondesignation

0: reference1: 0.90fc’2: 0.85fc’3: 0.75fc’

Pn, max

(kips)

Pn, max, 1 /Pn, max, 0

Pn, max, 2 /Pn, max, 0

Pn, max, 3 /Pn, max, 0

BI03 0 1486779

BI04 0 1774472

SQ01 1 1325428 0.918

SQ02 1 1624232 0.935

SQ03 1 1330890 0.919

SQ04 1 1623919 0.935

CIR01 1 1345750 0.919

CIR02 1 1630742 0.933

BI01 1 1365939 0.919

BI02 1 1655741 0.933

BI03 1 1366052 0.919

BI04 1 1656325 0.933

SQ01 2 1267038 0.878

SQ02 2 1567864 0.903

SQ03 2 1271982 0.878

SQ04 2 1567568 0.903

CIR01 2 1286234 0.878

CIR02 2 1572500 0.900

BI01 2 1305574 0.878

BI02 2 1596665 0.900

BI03 2 1305688 0.878

BI04 2 1597252 0.900

SQ01 3 1151857 0.798

SQ02 3 1455127 0.838

SQ03 3 1154164 0.797

SQ04 3 1454866 0.838

CIR01 3 1167201 0.797

CIR02 3 1458043 0.834

BI01 3 1184845 0.797

215

Sectiondesignation

0: reference1: 0.90fc’2: 0.85fc’3: 0.75fc’

Pn, max

(kips)

Pn, max, 1 /Pn, max, 0

Pn, max, 2 /Pn, max, 0

Pn, max, 3 /Pn, max, 0

BI02 3 1478514 0.833

BI03 3 1184961 0.797

BI04 3 1479105 0.834

Table C.5 The effect of dimensional tolerances of concrete on maximum moment capacities of reinforced concrete sections

Section designation1: reference

2:-3/8 inMo, max

(kips.ft)Mo, max, 2 / Mo, max, 1

SQ01 1 151.54

SQ02 1 294.21

SQ03 1 151.48

SQ04 1 289.18

CIR01 1 151.44

CIR02 1 271.75

BI01 1 156.41

BI02 1 259.27

BI03 1 154.18

BI04 1 259.48

SQ01 2 151.68 1.001

SQ02 2 293.11 0.996

SQ03 2 150.95 0.997

SQ04 2 288.16 0.996

CIR01 2 146.86 0.970

CIR02 2 261.86 0.964

BI01 2 156.48 1.000

BI02 2 258.97 0.999

BI03 2 154.31 1.001

BI04 2 259.56 1.000

216

Table C.6 The effect of dimensional tolerances of concrete on axial load capacities of reinforced concrete sections

Section designation1: reference

2:-3/8 inPn, max

(kips)Pn, max, 1 /Pn, max, 0

SQ01 1 1443285

SQ02 1 1736969

SQ03 1 1448708

SQ04 1 1736621

CIR01 1 1464783

CIR02 1 1747226

BI01 1 1486669

BI02 1 1773892

BI03 1 1486779

BI04 1 1774472

SQ01 2 1385577 0.960

SQ02 2 1682518 0.969

SQ03 2 1391509 0.961

SQ04 2 1682153 0.969

CIR01 2 1415069 0.966

CIR02 2 1697728 0.972

BI01 2 1428414 0.961

BI02 2 1714605 0.967

BI03 2 1428392 0.961

BI04 2 1714557 0.966

Table C.7 The increase in maximum moment capacities of reinforced concrete sections provided by the SIMCON jacket

Section designation0: rc only

1: bonded SIMCONMo, max (kips.ft) Mo, max,1 / Mo, max,0

SQ01 0 168

SQ02 0 309

SQ03 0 163

217

Section designation0: rc only

1: bonded SIMCONMo, max (kips.ft) Mo, max,1 / Mo, max,0

SQ04 0 295

CIR01 0 184

CIR02 0 322

BI01 0 157

BI02 0 259

BI03 0 155

BI04 0 259

SQ11 1 272 1.619

SQ12 1 437 1.414

SQ13 1 272 1.669

SQ14 1 431 1.461

CIR11 1 276 1.501

CIR12 1 425 1.322

BI11 1 265 1.688

BI12 1 369 1.425

BI13 1 262 1.690

BI14 1 366 1.413

SQ21 1 402 2.393

SQ22 1 587 1.900

SQ23 1 411 2.521

SQ24 1 589 1.997

CIR21 1 392 2.133

CIR22 1 562 1.748

BI21 1 412 2.624

BI22 1 521 2.012

BI23 1 409 2.639

BI24 1 517 1.996

218

Table C.8 The increase in axial load capacities of reinforced concrete sections provided by the SIMCON jacket

Section designation0: rc only

1: bonded SIMCONPn, max

(kips) Pn, max,1 / Pn, max,0

SQ01 0 1443285

SQ02 0 1736969

SQ03 0 1448708

SQ04 0 1736621

CIR01 0 1464783

CIR02 0 1747226

BI01 0 1486669

BI02 0 1773892

BI03 0 1486779

BI04 0 1774472

SQ11 1 1928317 1.336

SQ12 1 2225476 1.281

SQ13 1 1928139 1.331

SQ14 1 2225128 1.281

CIR11 1 1874788 1.280

CIR12 1 2171659 1.243

BI11 1 1942984 1.307

BI12 1 2239726 1.263

BI13 1 1942974 1.307

BI14 1 2239706 1.262

SQ21 1 2482656 1.720

SQ22 1 2780458 1.601

SQ23 1 2482556 1.714

SQ24 1 2780262 1.601

CIR21 1 2350755 1.605

CIR22 1 2648395 1.516

BI21 1 2492410 1.677

BI22 1 2789978 1.573

BI23 1 2492405 1.676

BI24 1 2789967 1.572

219

Table C.9 The effect of bonding of SIMCON jacket in maximum moment capacities

Section designation 1: bonded; 2: unbonded Mo, max (kips.ft) Mo, max,2 / Mo, max,1

SQ11 1 272

SQ12 1 437

SQ13 1 272

SQ14 1 431

CIR11 1 276

CIR12 1 425

BI11 1 265

BI12 1 369

BI13 1 262

BI14 1 366

SQ21 1 402

SQ22 1 587

SQ23 1 411

SQ24 1 589

CIR21 1 392

CIR22 1 562

BI21 1 412

BI22 1 521

BI23 1 409

BI24 1 517

SQ11 2 230 0.846

SQ12 2 381 0.872

SQ13 2 238 0.876

SQ14 2 358 0.830

CIR11 2 273 0.991

CIR12 2 411 0.967

BI11 2 256 0.966

BI12 2 350 0.948

BI13 2 254 0.970

BI14 2 349 0.954

SQ21 2 355 0.883

SQ22 2 495 0.844

SQ23 2 350 0.852

220

Section designation 1: bonded; 2: unbonded Mo, max (kips.ft) Mo, max,2 / Mo, max,1

SQ24 2 469 0.796

CIR21 2 385 0.982

CIR22 2 523 0.931

BI21 2 387 0.939

BI22 2 471 0.904

BI23 2 385 0.941

BI24 2 469 0.908

Table C.10 The effect of existing load on maximum moment capacities

Sectiondesignation

existing strain:0: 0%; 1: 0.03%;2: 0.06%; 3: 0.1%

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

SQ11 0 272

SQ12 0 437

SQ13 0 272

SQ14 0 431

CIR11 0 276

CIR12 0 425

BI11 0 265

BI12 0 369

BI13 0 262

BI14 0 366

SQ11 1 260 0.96

SQ12 1 412 0.94

SQ13 1 264 0.97

SQ14 1 416 0.96

CIR11 1 249 0.90

CIR12 1 378 0.89

BI11 1 260 0.98

BI12 1 365 0.99

BI13 1 258 0.98

BI14 1 362 0.99

221

Sectiondesignation

existing strain:0: 0%; 1: 0.03%;2: 0.06%; 3: 0.1%

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

SQ11 2 263 0.97

SQ12 2 413 0.94

SQ13 2 263 0.97

SQ14 2 412 0.96

CIR11 2 246 0.89

CIR12 2 372 0.88

BI11 2 253 0.96

BI12 2 358 0.97

BI13 2 252 0.96

BI14 2 354 0.97

SQ11 3 264 0.97

SQ12 3 404 0.92

SQ13 3 266 0.98

SQ14 3 400 0.93

CIR11 3 238 0.86

CIR12 3 358 0.84

BI11 3 241 0.91

BI12 3 343 0.93

BI13 3 239 0.91

BI14 3 340 0.93

SQ21 0 402

SQ22 0 587

SQ23 0 411

SQ24 0 589

CIR21 0 393

CIR22 0 562

BI21 0 412

BI22 0 521

BI23 0 409

BI24 0 517

SQ21 1 397 0.99

SQ22 1 564 0.96

SQ23 1 408 0.99

222

Sectiondesignation

existing strain:0: 0%; 1: 0.03%;2: 0.06%; 3: 0.1%

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

SQ24 1 572 0.97

CIR21 1 375 0.96

CIR22 1 514 0.91

BI21 1 402 0.98

BI22 1 510 0.98

BI23 1 400 0.98

BI24 1 506 0.98

SQ21 2 397 0.99

SQ22 2 567 0.97

SQ23 2 403 0.98

SQ24 2 573 0.97

CIR21 2 373 0.95

CIR22 2 502 0.89

BI21 2 388 0.94

BI22 2 493 0.95

BI23 2 386 0.94

BI24 2 489 0.95

SQ21 3 405 1.01

SQ22 3 566 0.96

SQ23 3 398 0.97

SQ24 3 561 0.95

CIR21 3 356 0.91

CIR22 3 476 0.85

BI21 3 359 0.87

BI22 3 460 0.88

BI23 3 357 0.87

BI24 3 456 0.88

223

Table C.11 The effect of existing load on axial load capacities

Sectiondesignation

existing strain:0: 0%; 1: 0.03%;2: 0.06%; 3: 0.1%

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ11 0 1928317

SQ12 0 2225476

SQ13 0 1928139

SQ14 0 2225128

CIR11 0 1874788

CIR12 0 2171659

BI11 0 1942984

BI12 0 2239726

BI13 0 1942974

BI14 0 2239706

SQ11 1 1903681 0.987

SQ12 1 2200841 0.989

SQ13 1 1903504 0.987

SQ14 1 2200493 0.989

CIR11 1 1852992 0.988

CIR12 1 1818409 0.837

BI11 1 1918096 0.987

BI12 1 2214838 0.989

BI13 1 1918086 0.987

BI14 1 2214818 0.989

SQ11 2 1864565 0.967

SQ12 2 2161724 0.971

SQ13 2 1864388 0.967

SQ14 2 2161376 0.971

CIR11 2 2115280 1.128

CIR12 2 2052648 0.945

BI11 2 1878636 0.967

BI12 2 2175378 0.971

BI13 2 1878626 0.967

BI14 2 2175358 0.971

SQ11 3 1793647 0.930

SQ12 3 2090807 0.939

224

Sectiondesignation

existing strain:0: 0%; 1: 0.03%;2: 0.06%; 3: 0.1%

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ13 3 1793470 0.930

SQ14 3 2090458 0.939

CIR11 3 2100038 1.120

CIR12 3 2601509 1.198

BI11 3 1809634 0.931

BI12 3 2103982 0.939

BI13 3 1809745 0.931

BI14 3 2103962 0.939

SQ21 0 2482656

SQ22 0 2780458

SQ23 0 2482556

SQ24 0 2780262

CIR21 0 2350755

CIR22 0 2648395

BI21 0 2492410

BI22 0 2789978

BI23 0 2492405

BI24 0 2789967

SQ21 1 2429247 0.978

SQ22 1 2727050 0.981

SQ23 1 2429148 0.978

SQ24 1 2726854 0.981

CIR21 1 1755776 0.747

CIR22 1 2149863 0.812

BI21 1 2438659 0.978

BI22 1 2736226 0.981

BI23 1 2438653 0.978

BI24 1 2736215 0.981

SQ21 2 2344137 0.944

SQ22 2 2641939 0.950

SQ23 2 2344037 0.944

SQ24 2 2641743 0.950

CIR21 2 2304414 0.980

225

Sectiondesignation

existing strain:0: 0%; 1: 0.03%;2: 0.06%; 3: 0.1%

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

CIR22 2 2231727 0.843

BI21 2 2354460 0.945

BI22 2 2651202 0.950

BI23 2 2354450 0.945

BI24 2 2651182 0.950

SQ21 3 2189071 0.882

SQ22 3 2486873 0.894

SQ23 3 2188971 0.882

SQ24 3 2486677 0.894

CIR21 3 2528598 1.076

CIR22 3 2396910 0.905

BI21 3 2203400 0.884

BI22 3 2500142 0.896

BI23 3 2203391 0.884

BI24 3 2500122 0.896

Table C.12 The effect of routine strength variations of SIMCON on maximum moment capacities

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

SQ11 0 272

SQ12 0 437

SQ13 0 272

SQ14 0 431

CIR11 0 276

CIR12 0 425

BI11 0 265

BI12 0 369

BI13 0 262

BI14 0 366

SQ11 1 248 0.96

226

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

SQ12 1 400 0.97

SQ13 1 250 0.95

SQ14 1 406 0.97

CIR11 1 241 0.96

CIR12 1 373 0.98

BI11 1 255 0.97

BI12 1 361 0.98

BI13 1 253 0.97

BI14 1 358 0.98

SQ11 2 240 0.93

SQ12 2 393 0.95

SQ13 2 244 0.92

SQ14 2 400 0.96

CIR11 2 235 0.93

CIR12 2 368 0.96

BI11 2 251 0.95

BI12 2 357 0.97

BI13 2 248 0.95

BI14 2 353 0.96

SQ11 3 229 0.88

SQ12 3 380 0.92

SQ13 3 232 0.88

SQ14 3 387 0.93

CIR11 3 224 0.89

CIR12 3 359 0.94

BI11 3 241 0.92

BI12 3 348 0.94

BI13 3 239 0.91

BI14 3 345 0.94

SQ21 0 402

SQ22 0 587

SQ23 0 411

SQ24 0 589

227

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

CIR21 0 393

CIR22 0 562

BI21 0 412

BI22 0 521

BI23 0 409

BI24 0 517

SQ21 1 372 0.94

SQ22 1 536 0.95

SQ23 1 380 0.94

SQ24 1 542 0.95

CIR21 1 350 0.93

CIR22 1 500 0.96

BI21 1 389 0.95

BI22 1 500 0.96

BI23 1 387 0.95

BI24 1 496 0.96

SQ21 2 360 0.91

SQ22 2 521 0.92

SQ23 2 365 0.90

SQ24 2 530 0.92

CIR21 2 338 0.90

CIR22 2 490 0.94

BI21 2 379 0.92

BI22 2 489 0.94

BI23 2 376 0.92

BI24 2 486 0.94

SQ21 3 334 0.85

SQ22 3 492 0.87

SQ23 3 335 0.82

SQ24 3 501 0.87

CIR21 3 314 0.84

CIR22 3 469 0.90

BI21 3 357 0.87

228

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Mo, max

(kips.ft)Mo, max,1 / Mo, max,0

Mo, max,2 / Mo, max,0

Mo, max,3 / Mo, max,0

BI22 3 469 0.90

BI23 3 355 0.87

BI24 3 465 0.90

Table C.13 The effect of routine strength variations of SIMCON on axial load capacities

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ11 0 1928317

SQ12 0 2225476

SQ13 0 1928139

SQ14 0 2225128

CIR11 0 1874788

CIR12 0 2171659

BI11 0 1942984

BI12 0 2239726

BI13 0 1942974

BI14 0 2239706

SQ11 1 1889208 0.980

SQ12 1 2186368 0.982

SQ13 1 1889031 0.980

SQ14 1 2186019 0.982

CIR11 1 1840284 0.982

CIR12 1 2137155 0.984

BI11 1 1903689 0.980

BI12 1 2200432 0.982

BI13 1 1903680 0.980

BI14 1 2200412 0.982

SQ11 2 1869972 0.970

SQ12 2 2167132 0.974

229

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ13 2 1869795 0.970

SQ14 2 2166783 0.974

CIR11 2 1823935 0.973

CIR12 2 2120806 0.977

BI11 2 1884356 0.970

BI12 2 2181098 0.974

BI13 2 1884346 0.970

BI14 2 2181078 0.974

SQ11 3 1832487 0.950

SQ12 3 2129647 0.957

SQ13 3 1832310 0.950

SQ14 3 2129298 0.957

CIR11 3 1790788 0.955

CIR12 3 2087659 0.961

BI11 3 1846653 0.950

BI12 3 2143396 0.957

BI13 3 1846644 0.950

BI14 3 2143376 0.957

SQ21 0 2482656

SQ22 0 2780458

SQ23 0 2482556

SQ24 0 2780262

CIR21 0 2350755

CIR22 0 2648395

BI21 0 2492410

BI22 0 2789978

BI23 0 2492405

BI24 0 2789967

SQ21 1 2397273 0.966

SQ22 1 2695075 0.969

SQ23 1 2397173 0.966

SQ24 1 2694879 0.969

CIR21 1 2277644 0.969

230

Sectiondesignation

strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’; 3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

CIR22 1 2574515 0.972

BI21 1 2407401 0.966

BI22 1 2704365 0.969

BI23 1 2407391 0.966

BI24 1 2704354 0.969

SQ21 2 2355329 0.949

SQ22 2 2653131 0.954

SQ23 2 2355229 0.949

SQ24 2 2652935 0.954

CIR21 2 2242569 0.954

CIR22 2 2539440 0.959

BI21 2 2366485 0.949

BI22 2 2663228 0.955

BI23 2 2366476 0.949

BI24 2 2663208 0.955

SQ21 3 2273765 0.916

SQ22 3 2571567 0.925

SQ23 3 2273665 0.916

SQ24 3 2571371 0.925

CIR21 3 2172927 0.924

CIR22 3 2469798 0.933

BI21 3 2286705 0.917

BI22 3 2583448 0.926

BI23 3 2286696 0.917

BI24 3 2583428 0.926

231

Table C.14 The effect of routine thickness variations of SIMCON on maximum moment capacities

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

SQ11 1 272

SQ12 1 437

SQ13 1 272

SQ14 1 431

CIR11 1 276

CIR12 1 425

BI11 1 265

BI12 1 369

BI13 1 262

BI14 1 366

SQ11 2 236 0.91

SQ12 2 386 0.93

SQ13 2 238 0.90

SQ14 2 390 0.93

CIR11 2 229 0.91

CIR12 2 357 0.94

BI11 2 239 0.91

BI12 2 345 0.94

BI13 2 238 0.91

BI14 2 342 0.93

SQ11 3 247 0.95

SQ12 3 400 0.97

SQ13 3 250 0.95

SQ14 3 403 0.97

CIR11 3 241 0.96

CIR12 3 369 0.97

BI11 3 252 0.95

BI12 3 357 0.97

BI13 3 249 0.95

BI14 3 354 0.97

232

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

SQ11 4 273 1.05

SQ12 4 427 1.03

SQ13 4 276 1.05

SQ14 4 431 1.03

CIR11 4 263 1.05

CIR12 4 395 1.04

BI11 4 277 1.05

BI12 4 382 1.04

BI13 4 275 1.05

BI14 4 379 1.04

SQ11 5 287 1.11

SQ12 5 440 1.07

SQ13 5 290 1.10

SQ14 5 446 1.07

CIR11 5 275 1.09

CIR12 5 409 1.07

BI11 5 290 1.10

BI12 5 396 1.07

BI13 5 288 1.10

BI14 5 393 1.07

SQ21 1 402

SQ22 1 587

SQ23 1 411

SQ24 1 589

CIR21 1 393

CIR22 1 562

BI21 1 412

BI22 1 521

BI23 1 409

BI24 1 517

SQ21 2 340 0.86

SQ22 2 499 0.89

233

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

SQ23 2 346 0.85

SQ24 2 508 0.89

CIR21 2 323 0.86

CIR22 2 462 0.89

BI21 2 346 0.84

BI22 2 454 0.87

BI23 2 344 0.84

BI24 2 451 0.87

SQ21 3 364 0.92

SQ22 3 532 0.94

SQ23 3 371 0.91

SQ24 3 539 0.94

CIR21 3 348 0.93

CIR22 3 490 0.94

BI21 3 378 0.92

BI22 3 486 0.93

BI23 3 375 0.92

BI24 3 483 0.94

SQ21 4 433 1.10

SQ22 4 600 1.07

SQ23 4 426 1.05

SQ24 4 608 1.06

CIR21 4 402 1.07

CIR22 4 552 1.06

BI21 4 445 1.09

BI22 4 557 1.07

BI23 4 443 1.09

BI24 4 553 1.07

SQ21 5 448 1.13

SQ22 5 637 1.13

SQ23 5 467 1.15

SQ24 5 644 1.12

234

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

CIR21 5 429 1.14

CIR22 5 586 1.13

BI21 5 481 1.18

BI22 5 595 1.14

BI23 5 479 1.18

BI24 5 592 1.15

Table C.15 The effect of routine thickness variations of SIMCON on axial load capacities

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

SQ11 1 1928317

SQ12 1 2225476

SQ13 1 1928139

SQ14 1 2225128

CIR11 1 1874788

CIR12 1 2171659

BI11 1 1942984

BI12 1 2239726

BI13 1 1942974

BI14 1 2239706

SQ11 2 1826092 0.947

SQ12 2 2123251 0.954

SQ13 2 1825914 0.947

SQ14 2 2122903 0.954

CIR11 2 1785052 0.952

CIR12 2 2081923 0.959

BI11 2 1842464 0.948

235

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

BI12 2 2137066 0.954

BI13 2 1842575 0.948

BI14 2 2137046 0.954

SQ11 3 1876922 0.973

SQ12 3 2174081 0.977

SQ13 3 1876745 0.973

SQ14 3 2173733 0.977

CIR11 3 1829697 0.976

CIR12 3 2126568 0.979

BI11 3 1891368 0.973

BI12 3 2188110 0.977

BI13 3 1891358 0.973

BI14 3 2188090 0.977

SQ11 4 1980275 1.027

SQ12 4 2277435 1.023

SQ13 4 1980098 1.027

SQ14 4 2277087 1.023

CIR11 4 1920325 1.024

CIR12 4 2217197 1.021

BI11 4 1995172 1.027

BI12 4 2291914 1.023

BI13 4 1995162 1.027

BI14 4 2291894 1.023

SQ11 5 2032798 1.054

SQ12 5 2329958 1.047

SQ13 5 2032621 1.054

SQ14 5 2329609 1.047

CIR11 5 1966309 1.049

CIR12 5 2263180 1.042

BI11 5 2047931 1.054

BI12 5 2344673 1.047

BI13 5 2047922 1.054

236

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

BI14 5 2344653 1.047

SQ21 1 2482656

SQ22 1 2780458

SQ23 1 2482556

SQ24 1 2780262

CIR21 1 2350755

CIR22 1 2648395

BI21 1 2492410

BI22 1 2789978

BI23 1 2492405

BI24 1 2789967

SQ21 2 2248571 0.906

SQ22 2 2546374 0.916

SQ23 2 2248472 0.906

SQ24 2 2546178 0.916

CIR21 2 2154700 0.917

CIR22 2 2451572 0.926

BI21 2 2264681 0.909

BI22 2 2561423 0.918

BI23 2 2264671 0.909

BI24 2 2561403 0.918

SQ21 3 2364433 0.952

SQ22 3 2662235 0.957

SQ23 3 2364333 0.952

SQ24 3 2662039 0.957

CIR21 3 2251568 0.958

CIR22 3 2548439 0.962

BI21 3 2376480 0.953

BI22 3 2673222 0.958

BI23 3 2376471 0.953

BI24 3 2673202 0.958

SQ21 4 2604229 1.049

237

Sectiondesignation

SIMCON thickness:1: reference

2:0.8 t; 3:0.9 t;4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

SQ22 4 2902559 1.044

SQ23 4 2604165 1.049

SQ24 4 2902433 1.044

CIR21 4 2455248 1.044

CIR22 4 2752888 1.039

BI21 4 2613353 1.049

BI22 4 2910921 1.043

BI23 4 2613348 1.049

BI24 4 2910910 1.043

SQ21 5 2730005 1.100

SQ22 5 3028334 1.089

SQ23 5 2729941 1.100

SQ24 5 3028209 1.089

CIR21 5 2561603 1.090

CIR22 5 2859244 1.080

BI21 5 2736727 1.098

BI22 5 3034907 1.088

BI23 5 2736724 1.098

BI24 5 3034899 1.088

Table C.16 The effect of non-concentric placement of SIMCON during construction on maximum moment capacities

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

SQ11 1 272

SQ12 1 437

SQ13 1 272

SQ14 1 431

CIR11 1 276

238

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

CIR12 1 425

BI11 1 265

BI12 1 369

BI13 1 262

BI14 1 366

SQ11 2 265 1.02

SQ12 2 414 1.00

SQ13 2 268 1.01

SQ14 2 417 1.00

CIR11 2 256 1.02

CIR12 2 381 1.00

BI11 2 263 1.00

BI12 2 364 0.99

BI13 2 262 1.00

BI14 2 362 0.99

SQ11 3 262 1.01

SQ12 3 414 1.00

SQ13 3 264 1.00

SQ14 3 418 1.00

CIR11 3 254 1.01

CIR12 3 382 1.00

BI11 3 264 1.00

BI12 3 367 0.99

BI13 3 261 1.00

BI14 3 364 0.99

SQ11 4 258 1.00

SQ12 4 411 1.00

SQ13 4 262 0.99

SQ14 4 416 1.00

CIR11 4 251 1.00

CIR12 4 378 0.99

BI11 4 263 1.00

239

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

BI12 4 372 1.01

BI13 4 261 1.00

BI14 4 369 1.01

SQ11 5 254 0.98

SQ12 5 412 1.00

SQ13 5 260 0.99

SQ14 5 418 1.00

CIR11 5 250 0.99

CIR12 5 374 0.98

BI11 5 262 1.00

BI12 5 375 1.02

BI13 5 260 0.99

BI14 5 371 1.01

SQ21 1 402

SQ22 1 587

SQ23 1 411

SQ24 1 589

CIR21 1 393

CIR22 1 562

BI21 1 412

BI22 1 521

BI23 1 409

BI24 1 517

SQ21 2 412 1.04

SQ22 2 567 1.01

SQ23 2 412 1.01

SQ24 2 575 1.00

CIR21 2 388 1.03

CIR22 2 523 1.01

BI21 2 406 0.99

BI22 2 505 0.97

BI23 2 404 0.99

240

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Mo, max

(kips.ft)Mo, max,2 /Mo, max,1

Mo, max,3 /Mo, max,1

Mo, max,4 /Mo, max,1

Mo, max,5 /Mo, max,1

BI24 2 501 0.97

SQ21 3 405 1.03

SQ22 3 567 1.01

SQ23 3 412 1.01

SQ24 3 572 1.00

CIR21 3 382 1.02

CIR22 3 521 1.00

BI21 3 409 1.00

BI22 3 512 0.98

BI23 3 407 1.00

BI24 3 509 0.98

SQ21 4 381 0.96

SQ22 4 566 1.00

SQ23 4 396 0.98

SQ24 4 574 1.00

CIR21 4 374 1.00

CIR22 4 512 0.99

BI21 4 410 1.00

BI22 4 530 1.02

BI23 4 408 1.00

BI24 4 527 1.02

SQ21 5 389 0.99

SQ22 5 565 1.00

SQ23 5 382 0.94

SQ24 5 572 1.00

CIR21 5 374 1.00

CIR22 5 506 0.97

BI21 5 410 1.00

BI22 5 540 1.04

BI23 5 407 1.00

BI24 5 536 1.04

241

Table C.17 The effect of non-concentric placement of SIMCON during construction on axial load capacities

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

SQ11 1 1928317

SQ12 1 2225476

SQ13 1 1928139

SQ14 1 2225128

CIR11 1 1874788

CIR12 1 2171659

BI11 1 1942984

BI12 1 2239726

BI13 1 1942974

BI14 1 2239706

SQ11 2 1923923 0.998

SQ12 2 2221082 0.998

SQ13 2 1923745 0.998

SQ14 2 2220734 0.998

CIR11 2 1871851 0.998

CIR12 2 2168722 0.999

BI11 2 1938589 0.998

BI12 2 2235331 0.998

BI13 2 1938579 0.998

BI14 2 2235311 0.998

SQ11 3 1932703 1.002

SQ12 3 2229863 1.002

SQ13 3 1932526 1.002

SQ14 3 2229514 1.002

CIR11 3 1884516 1.005

CIR12 3 2181387 1.004

BI11 3 1947371 1.002

BI12 3 2244113 1.002

BI13 3 1947362 1.002

BI14 3 2244093 1.002

242

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

SQ11 4 1919521 0.995

SQ12 4 2216681 0.996

SQ13 4 1919344 0.995

SQ14 4 2216332 0.996

CIR11 4 1869048 0.997

CIR12 4 2165920 0.997

BI11 4 1934187 0.995

BI12 4 2230929 0.996

BI13 4 1934177 0.995

BI14 4 2230909 0.996

SQ11 5 1937082 1.005

SQ12 5 2234241 1.004

SQ13 5 1936905 1.005

SQ14 5 2233893 1.004

CIR11 5 1894415 1.010

CIR12 5 2191287 1.009

BI11 5 1951751 1.005

BI12 5 2248493 1.004

BI13 5 1951741 1.005

BI14 5 2248473 1.004

SQ21 1 2482656

SQ22 1 2780458

SQ23 1 2482556

SQ24 1 2780262

CIR21 1 2350755

CIR22 1 2648395

BI21 1 2492410

BI22 1 2789978

BI23 1 2492405

BI24 1 2789967

SQ21 2 2474793 0.997

SQ22 2 2773052 0.997

243

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

SQ23 2 2474694 0.997

SQ24 2 2772926 0.997

CIR21 2 2344133 0.997

CIR22 2 2641004 0.997

BI21 2 2484547 0.997

BI22 2 2782114 0.997

BI23 2 2484541 0.997

BI24 2 2782103 0.997

SQ21 3 2490497 1.003

SQ22 3 2788300 1.003

SQ23 3 2490398 1.003

SQ24 3 2788104 1.003

CIR21 3 2372414 1.009

CIR22 3 2669285 1.008

BI21 3 2501384 1.004

BI22 3 2798126 1.003

BI23 3 2501374 1.004

BI24 3 2798106 1.003

SQ21 4 2468554 0.994

SQ22 4 2766883 0.995

SQ23 4 2468490 0.994

SQ24 4 2766758 0.995

CIR21 4 2338594 0.995

CIR22 4 2635465 0.995

BI21 4 2476662 0.994

BI22 4 2774229 0.994

BI23 4 2476657 0.994

BI24 4 2774218 0.994

SQ21 5 2498318 1.006

SQ22 5 2796120 1.006

SQ23 5 2498218 1.006

SQ24 5 2795924 1.006

244

Sectiondesignation

SIMCON thickness atcompression area:

1: reference; 2:0.8 t3:0.9 t; 4:1.1 t; 5:1.2 t

Pn, max

(kips)Pn, max,2 / Pn, max,1

Pn, max,3 / Pn, max,1

Pn, max,4 / Pn, max,1

Pn, max,5 / Pn, max,1

CIR21 5 2395302 1.019

CIR22 5 2692173 1.017

BI21 5 2512170 1.008

BI22 5 2808912 1.007

BI23 5 2512160 1.008

BI24 5 2808892 1.007

Table C.18 The effect of reduced strength SIMCON seams and seam locations on maximum moment capacities

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

SQ11 0 0 272

SQ12 0 0 437

SQ13 0 0 272

SQ14 0 0 431

CIR11 0 0 276

CIR12 0 0 425

BI11 0 0 265

BI12 0 0 369

BI13 0 0 262

BI14 0 0 366

SQ21 0 0 402

SQ22 0 0 587

SQ23 0 0 411

SQ24 0 0 589

CIR21 0 0 393

CIR22 0 0 562

BI21 0 0 412

245

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

BI22 0 0 521

BI23 0 0 409

BI24 0 0 517

SQ11 1 1 259 0.9980

SQ12 1 1 412 0.9983

SQ13 1 1 263 0.9970

SQ14 1 1 417 0.9969

CIR11 1 1 249 0.9910

CIR12 1 1 381 0.9983

BI11 1 1 264 1.0000

BI12 1 1 369 0.9996

BI13 1 1 261 0.9965

BI14 1 1 365 0.9973

SQ21 1 1 393 0.9951

SQ22 1 1 563 0.9985

SQ23 1 1 404 0.9945

SQ24 1 1 572 0.9980

CIR21 1 1 370 0.9864

CIR22 1 1 518 0.9970

BI21 1 1 409 0.9988

BI22 1 1 519 0.9969

BI23 1 1 406 0.9966

BI24 1 1 515 0.9969

SQ11 1 2 259 0.9996

SQ12 1 2 411 0.9959

SQ13 1 2 262 0.9936

SQ14 1 2 416 0.9964

CIR11 1 2 249 0.9879

CIR12 1 2 381 0.9970

BI11 1 2 263 0.9983

BI12 1 2 369 0.9983

246

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

BI13 1 2 260 0.9948

BI14 1 2 366 0.9982

SQ21 1 2 392 0.9920

SQ22 1 2 562 0.9978

SQ23 1 2 403 0.9913

SQ24 1 2 572 0.9980

CIR21 1 2 367 0.9794

CIR22 1 2 516 0.9932

BI21 1 2 408 0.9960

BI22 1 2 518 0.9946

BI23 1 2 406 0.9961

BI24 1 2 514 0.9945

SQ11 1 3 259 0.9985

SQ12 1 3 412 0.9976

SQ13 1 3 262 0.9944

SQ14 1 3 416 0.9954

CIR11 1 3 247 0.9798

CIR12 1 3 379 0.9931

BI11 1 3 262 0.9950

BI12 1 3 368 0.9956

BI13 1 3 260 0.9950

BI14 1 3 365 0.9956

SQ21 1 3 389 0.9863

SQ22 1 3 562 0.9963

SQ23 1 3 401 0.9873

SQ24 1 3 571 0.9958

CIR21 1 3 363 0.9686

CIR22 1 3 513 0.9869

BI21 1 3 407 0.9928

BI22 1 3 516 0.9917

BI23 1 3 404 0.9929

247

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

BI24 1 3 513 0.9917

SQ11 2 1 259 1.0000

SQ12 2 1 413 1.0000

SQ13 2 1 263 0.9959

SQ14 2 1 417 0.9978

CIR11 2 1 252 0.9996

CIR12 2 1 382 0.9998

BI11 2 1 263 0.9984

BI12 2 1 370 1.0006

BI13 2 1 261 0.9984

BI14 2 1 366 0.9983

SQ21 2 1 394 0.9985

SQ22 2 1 564 1.0000

SQ23 2 1 406 0.9986

SQ24 2 1 572 0.9976

CIR21 2 1 374 0.9964

CIR22 2 1 520 0.9997

BI21 2 1 410 1.0001

BI22 2 1 519 0.9974

BI23 2 1 407 1.0001

BI24 2 1 516 0.9991

SQ11 2 2 259 1.0000

SQ12 2 2 413 1.0000

SQ13 2 2 263 0.9959

SQ14 2 2 417 0.9978

CIR11 2 2 251 0.9955

CIR12 2 2 382 0.9998

BI11 2 2 264 1.0010

BI12 2 2 369 0.9997

BI13 2 2 261 0.9976

BI14 2 2 366 0.9997

248

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

SQ21 2 2 394 0.9985

SQ22 2 2 562 0.9964

SQ23 2 2 406 0.9986

SQ24 2 2 572 0.9976

CIR21 2 2 373 0.9961

CIR22 2 2 520 0.9995

BI21 2 2 409 0.9990

BI22 2 2 519 0.9978

BI23 2 2 407 0.9990

BI24 2 2 516 0.9978

SQ11 2 3 259 0.9993

SQ12 2 3 412 0.9966

SQ13 2 3 263 0.9959

SQ14 2 3 417 0.9978

CIR11 2 3 250 0.9952

CIR12 2 3 382 0.9996

BI11 2 3 263 0.9993

BI12 2 3 369 0.9981

BI13 2 3 262 0.9994

BI14 2 3 366 0.9980

SQ21 2 3 394 0.9971

SQ22 2 3 562 0.9963

SQ23 2 3 405 0.9972

SQ24 2 3 570 0.9952

CIR21 2 3 372 0.9925

CIR22 2 3 519 0.9972

BI21 2 3 409 0.9990

BI22 2 3 518 0.9952

BI23 2 3 407 0.9991

BI24 2 3 515 0.9969

SQ11 3 1 258 0.9947

249

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

SQ12 3 1 410 0.9936

SQ13 3 1 261 0.9914

SQ14 3 1 416 0.9948

CIR11 3 1 251 0.9956

CIR12 3 1 381 0.9968

BI11 3 1 263 0.9984

BI12 3 1 369 0.9991

BI13 3 1 261 0.9985

BI14 3 1 366 0.9991

SQ21 3 1 393 0.9942

SQ22 3 1 559 0.9924

SQ23 3 1 403 0.9914

SQ24 3 1 567 0.9902

CIR21 3 1 373 0.9937

CIR22 3 1 517 0.9947

BI21 3 1 409 0.9974

BI22 3 1 519 0.9965

BI23 3 1 406 0.9974

BI24 3 1 516 0.9983

SQ11 3 2 257 0.9892

SQ12 3 2 410 0.9922

SQ13 3 2 261 0.9891

SQ14 3 2 414 0.9912

CIR11 3 2 250 0.9954

CIR12 3 2 380 0.9941

BI11 3 2 263 0.9976

BI12 3 2 369 0.9986

BI13 3 2 261 0.9977

BI14 3 2 366 0.9986

SQ21 3 2 391 0.9907

SQ22 3 2 557 0.9877

250

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Mo, max

(kips.ft)Mo, max, 1 /Mo, max, 0

Mo, max, 2 /Mo, max, 0

Mo, max, 3 /Mo, max, 0

SQ23 3 2 401 0.9863

SQ24 3 2 565 0.9854

CIR21 3 2 371 0.9907

CIR22 3 2 517 0.9940

BI21 3 2 407 0.9938

BI22 3 2 518 0.9957

BI23 3 2 405 0.9937

BI24 3 2 516 0.9974

SQ11 3 3 255 0.9848

SQ12 3 3 407 0.9863

SQ13 3 3 259 0.9807

SQ14 3 3 412 0.9865

CIR11 3 3 249 0.9915

CIR12 3 3 379 0.9912

BI11 3 3 262 0.9960

BI12 3 3 368 0.9976

BI13 3 3 260 0.9925

BI14 3 3 366 0.9977

SQ21 3 3 387 0.9810

SQ22 3 3 553 0.9810

SQ23 3 3 384 0.9462

SQ24 3 3 561 0.9788

CIR21 3 3 370 0.9864

CIR22 3 3 514 0.9882

BI21 3 3 406 0.9911

BI22 3 3 517 0.9939

BI23 3 3 404 0.9909

BI24 3 3 514 0.9938

251

Table C.19 The effect of reduced strength SIMCON seams and seam locations on axial load capacities

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ11 0 0 1928317

SQ12 0 0 2225476

SQ13 0 0 1928139

SQ14 0 0 2225128

CIR11 0 0 1874788

CIR12 0 0 2171659

BI11 0 0 1942984

BI12 0 0 2239726

BI13 0 0 1942974

BI14 0 0 2239706

SQ21 0 0 2482656

SQ22 0 0 2780458

SQ23 0 0 2482556

SQ24 0 0 2780262

CIR21 0 0 2350755

CIR22 0 0 2648395

BI21 0 0 2492410

BI22 0 0 2789978

BI23 0 0 2492405

BI24 0 0 2789967

SQ11 1 1 1924020 0.9978

SQ12 1 1 2221180 0.9981

SQ13 1 1 1923843 0.9978

SQ14 1 1 2220831 0.9981

CIR11 1 1 1872485 0.9988

CIR12 1 1 2169356 0.9989

BI11 1 1 1938879 0.9979

BI12 1 1 2235621 0.9982

BI13 1 1 1938870 0.9979

BI14 1 1 2235601 0.9982

252

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ21 1 1 2473085 0.9961

SQ22 1 1 2770887 0.9966

SQ23 1 1 2472985 0.9961

SQ24 1 1 2770691 0.9966

CIR21 1 1 2344734 0.9974

CIR22 1 1 2642374 0.9977

BI21 1 1 2483171 0.9963

BI22 1 1 2780738 0.9967

BI23 1 1 2483165 0.9963

BI24 1 1 2780727 0.9967

SQ11 1 2 1924852 0.9982

SQ12 1 2 2222011 0.9984

SQ13 1 2 1924675 0.9982

SQ14 1 2 2221663 0.9984

CIR11 1 2 1871394 0.9982

CIR12 1 2 2168266 0.9984

BI11 1 2 1939332 0.9981

BI12 1 2 2236074 0.9984

BI13 1 2 1939322 0.9981

BI14 1 2 2236054 0.9984

SQ21 1 2 2475544 0.9971

SQ22 1 2 2773346 0.9974

SQ23 1 2 2475444 0.9971

SQ24 1 2 2773150 0.9974

CIR21 1 2 2343386 0.9969

CIR22 1 2 2641026 0.9972

BI21 1 2 2485014 0.9970

BI22 1 2 2782582 0.9973

BI23 1 2 2485009 0.9970

BI24 1 2 2782570 0.9973

SQ11 1 3 1924928 0.9982

253

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ12 1 3 2222088 0.9985

SQ13 1 3 1924751 0.9982

SQ14 1 3 2221740 0.9985

CIR11 1 3 1870987 0.9980

CIR12 1 3 2167858 0.9983

BI11 1 3 1939330 0.9981

BI12 1 3 2236072 0.9984

BI13 1 3 1939320 0.9981

BI14 1 3 2236052 0.9984

SQ21 1 3 2474589 0.9968

SQ22 1 3 2772392 0.9971

SQ23 1 3 2474490 0.9968

SQ24 1 3 2772196 0.9971

CIR21 1 3 2342731 0.9966

CIR22 1 3 2640372 0.9970

BI21 1 3 2483919 0.9966

BI22 1 3 2781487 0.9970

BI23 1 3 2483914 0.9966

BI24 1 3 2781475 0.9970

SQ11 2 1 1921300 0.9964

SQ12 2 1 2218460 0.9968

SQ13 2 1 1921123 0.9964

SQ14 2 1 2218111 0.9968

CIR11 2 1 1870515 0.9977

CIR12 2 1 2167386 0.9980

BI11 2 1 1936259 0.9965

BI12 2 1 2233001 0.9970

BI13 2 1 1936250 0.9965

BI14 2 1 2232981 0.9970

SQ21 2 1 2467029 0.9937

SQ22 2 1 2764831 0.9944

254

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ23 2 1 2466929 0.9937

SQ24 2 1 2764635 0.9944

CIR21 2 1 2340527 0.9956

CIR22 2 1 2637963 0.9961

BI21 2 1 2477286 0.9939

BI22 2 1 2774854 0.9946

BI23 2 1 2477281 0.9939

BI24 2 1 2774842 0.9946

SQ11 2 2 1922622 0.9970

SQ12 2 2 2219781 0.9974

SQ13 2 2 1922444 0.9970

SQ14 2 2 2219433 0.9974

CIR11 2 2 1869205 0.9970

CIR12 2 2 2166076 0.9974

BI11 2 2 1937000 0.9969

BI12 2 2 2233742 0.9973

BI13 2 2 1922622 0.9969

BI14 2 2 2233722 0.9973

SQ21 2 2 2470984 0.9953

SQ22 2 2 2768786 0.9958

SQ23 2 2 2470884 0.9953

SQ24 2 2 2768590 0.9958

CIR21 2 2 2338652 0.9949

CIR22 2 2 2636292 0.9954

BI21 2 2 2480303 0.9951

BI22 2 2 2777871 0.9957

BI23 2 2 2480298 0.9951

BI24 2 2 2777859 0.9957

SQ11 2 3 1922716 0.9971

SQ12 2 3 2219875 0.9975

SQ13 2 3 1922539 0.9971

255

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

SQ14 2 3 2219527 0.9975

CIR11 2 3 1868579 0.9967

CIR12 2 3 2165450 0.9971

BI11 2 3 1936961 0.9969

BI12 2 3 2233703 0.9973

BI13 2 3 1936951 0.9969

BI14 2 3 2233683 0.9973

SQ21 2 3 2469353 0.9946

SQ22 2 3 2767155 0.9952

SQ23 2 3 2469253 0.9946

SQ24 2 3 2766959 0.9952

CIR21 2 3 2337653 0.9944

CIR22 2 3 2635293 0.9951

BI21 2 3 2478441 0.9944

BI22 2 3 2776008 0.9950

BI23 2 3 2478435 0.9944

BI24 2 3 2775997 0.9950

SQ11 3 1 1915616 0.9934

SQ12 3 1 2212775 0.9943

SQ13 3 1 1915439 0.9934

SQ14 3 1 2212427 0.9943

CIR11 3 1 1866016 0.9953

CIR12 3 1 2162887 0.9960

BI11 3 1 1931209 0.9939

BI12 3 1 2227951 0.9947

BI13 3 1 1931199 0.9939

BI14 3 1 2227931 0.9947

SQ21 3 1 2454112 0.9885

SQ22 3 1 2751914 0.9897

SQ23 3 1 2454012 0.9885

SQ24 3 1 2751718 0.9897

256

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

CIR21 3 1 2331102 0.9916

CIR22 3 1 2628255 0.9924

BI21 3 1 2466026 0.9894

BI22 3 1 2763593 0.9905

BI23 3 1 2466020 0.9894

BI24 3 1 2763582 0.9905

SQ11 3 2 1918025 0.9947

SQ12 3 2 2215184 0.9954

SQ13 3 2 1917848 0.9947

SQ14 3 2 2214836 0.9954

CIR11 3 2 1864593 0.9946

CIR12 3 2 2161464 0.9953

BI11 3 2 1932625 0.9947

BI12 3 2 2229367 0.9954

BI13 3 2 1932615 0.9947

BI14 3 2 2229347 0.9954

SQ21 3 2 2461939 0.9917

SQ22 3 2 2759741 0.9925

SQ23 3 2 2461839 0.9917

SQ24 3 2 2759545 0.9925

CIR21 3 2 2329061 0.9908

CIR22 3 2 2626701 0.9918

BI21 3 2 2471770 0.9917

BI22 3 2 2769338 0.9926

BI23 3 2 2471765 0.9917

BI24 3 2 2769327 0.9926

SQ11 3 3 1917652 0.9945

SQ12 3 3 2214811 0.9952

SQ13 3 3 1917475 0.9945

SQ14 3 3 2214463 0.9952

CIR11 3 3 1863634 0.9941

257

Sectiondesignation

seam location:0: no seam;

1:@compressionside; 2:@side;

3:@tension side

seam strength:0: fc’; 1: 0.90 fc’;

2: 0.85 fc’;3: 0.75 fc’

Pn, max

(kips)Pn, max,1 / Pn, max,0

Pn, max,2 / Pn, max,0

Pn, max,3 / Pn, max,0

CIR12 3 3 2160505 0.9949

BI11 3 3 1931785 0.9942

BI12 3 3 2228527 0.9950

BI13 3 3 1931775 0.9942

BI14 3 3 2228507 0.9950

SQ21 3 3 2457799 0.9900

SQ22 3 3 2755602 0.9911

SQ23 3 3 2457700 0.9900

SQ24 3 3 2755406 0.9911

CIR21 3 3 2326986 0.9899

CIR22 3 3 2624626 0.9910

BI21 3 3 2466923 0.9898

BI22 3 3 2764491 0.9909

BI23 3 3 2466918 0.9898

BI24 3 3 2764480 0.9909