Structural Behavior of Hybrid & Ductal Decked Bulb T Beams Prestressed with CFCC

STRUCTURAL BEHAVIOR OF HYBRID & DUCTAL DECKED BULB T-BEAMS
PRESTRESSED WITH CARBON FIBER COMPOSITE CABLES
By
Ranjit Kumar Sharma
A Thesis Submitted to the
Department of Civil Engineering in
Partial Fulfillment of the Requirements for the Degree of
Master of Science in Civil Engineering
at
LAWRENCE TECHNOLOGICAL UNIVERSITY
Southfield, Michigan
May, 2015
© Ranjit Kumar Sharma. All rights reserved.

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ABSTRACT
Based on the current infrastructure conditions and performance, the American Society of Civil
Engineers (ASCE) has rated the United States bridges with a mediocre Grade Point Average
(GPA) of C+
in the scale of A to F according to their recent 2013 America’s infrastructure report
card (ASCE 2013). The United States so far has 607,380 bridges, out of which 66,749 bridges are
structurally deficient and 84,748 bridges are functionally obsolete, i.e. one in every nine bridges
is deficient and requires immediate rehabilitation. An estimated Federal Highway Administration
(FHWA) report (ASCE 2013) indicates, United States needs $20.5 billion annually for the next
fifteen years in order to eliminate the present deficient backlog. However, the nation currently
receives only $12.8 billion annually to mitigate deficient bridges (ASCE 2013). The primary
reasons behind the deterioration of prestressed concrete bridges as per Precast/Prestressed
Concrete Institute (PCI) reports (2004) are; a) increase in the volume of traffic, b) low durability
of conventional concrete, and, c) corrosion of steel reinforcement. Bridges made of side-by-side
box beam do not provide any space between the beams for visual inspection of any progressive
damage and maintenance of critical elements, which increases the risk of bridge failure. In
addition, conventional precast bridge system consumes excessive onsite time for the preparation
and construction of cast-in-place deck system that disrupts the flow of traffic.
To address the present issues in the bridge industry, several engineers have discovered numerous
innovative materials and novel construction techniques as an alternative solution to enhance
service life span of prestressed concrete bridges. The most significant breakthrough in the field of
concrete technology based on strength is the development of Ultra High Performance Concrete
(UHPC) and Fiber Reinforced Polymer (FRP). Both of these are the latest innovative material in
the field of construction and have gained the popularity across the globe due to their outstanding
characteristic properties of superior strength, excellent durability and long-term stability.
However, in reality, these innovative materials has a very limited number of applications, mostly
due to their high unit rate of production in comparison with locally available inexpensive
traditional construction material. Therefore, it is of utmost importance to initiate a research
investigation to increase the applications of these innovative materials by exploiting their superior
characteristic properties in an optimized structure.

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The research study presented in this thesis introduces state-of-the-art long lasting corrosion-free
decked bulb T-beams constructed from UHPC and prestressed with CFCC strands. These beams
anticipate to a) reduce the construction cost of bridge girders employing UHPC and FRP by
introducing the concept of hybridization and optimization without compromising their structural
behavior, b) eliminate the use of transverse reinforcement both in the critical shear span or in the
entire span of the beam, c) mitigates sudden shear and flexural failure of FRP prestressed bridge
girders employing conventional concrete and reinforcement, d) accelerate onsite construction of
bridges with inbuilt deck, e) reduces overall bridge maintenance cost by using corrosion-free
CFCC strands, and, f) reduces the risk of bridge failure by providing space between the beams for
visual inspection of critical elements. The two types of beams proposed in this present
investigation are: hybrid beam and ductal beams. The hybrid beam brings the concept of hybrid
formulation between two different types of concrete i.e. UHPC as fiber reinforced concrete in a
dense cementitious packed mix and High Strength Concrete (HSC) as conventional concrete with
minimum 28th
day average compressive strength of 9,000 psi (62.05 MPa) at different zones/spans
along the length of the beam to mitigate potential sudden shear failure by increasing inelastic
energy absorption and shear capacity of the beam. The hybrid beam was constructed by placing
UHPC without stirrups in the shear span of the beam at both ends which are critical to the shear
stresses. Whereas, the middle span of the beam which is critical for flexure was constructed with
HSC with stirrups. On the other hand, the ductal beam brings the concept of section optimization
of full UHPC beam section and suggests an under-reinforced FRP prestressed UHPC beam section
as an alternative approach to mitigating potential sudden flexural failure of under-reinforced FRP
prestressed HSC beam. Further, in order to investigate the structural performance of both the
hybrid and ductal beams, a comprehensive experimental program was conducted under varying
load configuration to evaluate shear and flexural behavior. Four shear load mechanisms with shear
span-to-depth (a/d) ratios of 3.0, 4.0, 5.0 and 6.0 were investigated on four end span of two hybrid
beams while two shear load mechanisms of a/d ratios of 3.0 and 4.0 were conducted on two end
span of one ductal beam. Also, both hybrid and ductal beam mid spans were tested under four-
point bending. The behavior of each test beam was evaluated experimentally in terms of deflection,
strain in concrete, strain in the CFCC prestressed strands, ductility ratio, crack patterns, crack
width, cracking force, ultimate failure load and the mode of shear and flexural failure. Further, the
experimental results of the test beams were compared with the experimental results of a similarly

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reinforced HSC beams investigated by Rout (2013) and Grace et al. (2015) under similar load
configurations. This facilitated a comparative assessment on the structural performance of these
beams under shear and flexural load. In addition, a comparative study was carried out between the
results obtained through the experimental investigation and analytical methods using applicable
design guidelines and codes for UHPC.
The outcomes of research investigations showed that UHPC is efficient in replacing shear
reinforcement in simply supported CFCC prestressed HSC beams. The UHPC can be utilized to
replace shear reinforcement either partially or completely throughout the span without
compromising the structural behavior as exhibited by similarly reinforced HSC beams with
traditional shear reinforcement. In addition, the behavior of all the test beams outperform by
exhibiting similar or higher ductility, resistance to cracking, ultimate shear and flexural capacity.
Further, with the increase in a/d ratio, UHPC present in the critical shear span of the hybrid beams
attributed to changing the catastrophic mode of shear failure to a more ductile shear/flexural mode
of failure. Whereas, the Rout’s (2013) HSC beams exhibited same catastrophic shear failure
irrespective of a/d ratio.
Further, upon comparison of experimental results of all test beams with analytical predicted values,
it was observed that French code AFGC (2002) and Japanese code JSCE (2006) provided similar
shear capacity. In addition, an analytical calculation developed in the present research
investigation to predict the flexural capacity and the behavior of the ductal beam slightly
overestimated the flexural capacity and the behavior.
Therefore, the decked bulb T-beam constructed with UHPC and prestressed with CFCC as
investigated in the present study promises a viable solution to mitigate potential sudden shear and
flexural failure of HSC beams prestressed with CFCC. This is achieved by eliminating shear
reinforcement either partially or completely throughout the span without compromising overall
structural performance. In addition, the hybrid and the ductal decked bulb T-beams exploits the
superior properties of UHPC and CFCC material by optimizing and hybridizing the section which
in turn reduces the higher initial cost of constructing bridges employing these materials.

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STRUCTURAL BEHAVIOR OF HYBRID & DUCTAL DECKED BULB T-BEAMS
PRESTRESSED WITH CARBON FIBER COMPOSITE CABLES
Ranjit Kumar Sharma
Advisor: Nabil F. Grace, Ph.D., P.E.
University Distinguished Professor,
Dean, College of Engineering,
Director of Center for Innovative Material Research (CIMR),
Lawrence Technological University, Southfield, U.S.A.
Date

vi
DEDICATION
I dedicate this thesis to my mother Sonmati Devi for giving me life and my
friend Gayatree Rath as a source of inspiration.

vii
ACKNOWLEDGEMENTS
I would like to express my earnest thanks to Dr. Nabil F. Grace, Dean of Engineering,
University Distinguished Professor, and Director, Center for Innovative Materials Research
(CIMR) at Lawrence Technological University (LTU). His guidance, encouragement, vision, and
innovative thinking have always been a constant source of inspiration for me in my studies.
I am greatly indebted to Dr. Mena Bebawy, Research Scientist, and Adjunct Professor,
LTU, for his technical help and persistence. His assistance and constructive criticism did help in
shaping this thesis. Also, I would like to convey my special thanks to all my instructors and faculty
members at LTU, for making me understand the intricacies of civil engineering in a much easier
manner.
Special thanks go to all the previous researchers here at CIMR, LTU, Prince Baah,
Soubhagya K. Rout and Marc Kasabasic for their excellent and outstanding research commitment
towards the development of decked bulb T-beam bridge system. The present research investigation
considered their experimental finding and took it a step forward towards the development of the
innovative decked bulb T-beam bridge system.
All the experimental work was performed at Structural Testing Center (STC) and CIMR,
LTU. I would like to acknowledge for the facilities provided by the testing center. I also sincerely
thank the U.S. Department of Transportation, Tokyo Rope Mfg. Co. Ltd., Japan, and Lafarge North
America for providing Ultra High Performance Concrete (UHPC) for providing the required fund
and materials to conclude this research.
I would take this opportunity to convey my sincere thanks to all my colleagues at LTU,
Ephrem Kassahun Zegeye, Charles Elder, Neil Waraksa, Brittany Schuel, Shane Hansen, Jordan
Britz, Craig Przytulski, Alan Killeward, Samuel Adjei, Abinash Acharya, Hassan Ernest Razak,
Kathy Gilman, Bridgett Bailiff, and Tamara Botzen for their help and support during my research
investigation. Finally, I would like to thank my parents and friends for their love and support during
all the stages of my life. I would like to express my sincere appreciation towards my father, for his
infinite sacrifices and prayers throughout my life.

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TABLE OF CONTENTS
ABSTRACT.................................................................................................................................... ii
DEDICATION............................................................................................................................... vi
ACKNOWLEDGEMENTS.......................................................................................................... vii
TABLE OF CONTENTS.............................................................................................................viii
LIST OF FIGURES ...................................................................................................................xviii
LIST OF TABLES..................................................................................................................... xxiv
CHAPTER 1 INTRODUCTION.................................................................................................... 1
1.1 Statement of the Problem...................................................................................................... 1
1.2 Hybrid and Ductal Precast Prestressed Decked Bulb T-Beams............................................ 3
1.3 Motivation............................................................................................................................. 5
1.4 Research Significance........................................................................................................... 6
1.5 Research Objectives.............................................................................................................. 8
1.6 Scope of Work ...................................................................................................................... 8
1.7 Thesis Outline....................................................................................................................... 9
CHAPTER 2 LITERATURE REVIEW ....................................................................................... 10
2.1 Introduction......................................................................................................................... 10
2.2 Available Innovative Materials for Prestressed Bridge Girders ......................................... 11
2.2.1 Concretes.................................................................................................................. 11
2.2.1.1 Ultra High Performance Concrete (UHPC).............................................. 12
2.2.1.1.1 Types of UHPC and mix design ................................................ 12
2.2.1.1.2 Composition of UHPC............................................................... 14
2.2.1.1.3 Fiber Reinforcement .................................................................. 15
2.2.1.1.4 Mixing of UHPC........................................................................ 15
2.2.1.1.5 Placement of UHPC................................................................... 16

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2.2.1.1.6 Curing of UHPC ........................................................................ 18
2.2.1.1.7 Material Properties of UHPC..................................................... 18
2.2.1.1.8 Corrosion of steel fibers in UHPC............................................. 19
2.2.1.1.9 Cost of UHPC Production.......................................................... 20
2.2.2 Reinforcement.......................................................................................................... 20
2.2.2.1 Fiber Reinforced Polymers (FRPs)........................................................... 22
2.2.2.1.1 Carbon Fiber Composite Cable (CFCC).................................... 22
2.2.3 Application of UHPC............................................................................................... 23
2.2.4 Application of FRPs................................................................................................. 24
2.3 Bond Strength of Ultra High Performance Concrete (UHPC)............................................ 25
2.3.1 Bond strength between UHPC and conventional concretes .................................... 26
2.3.2 Bond strength between UHPC and reinforcement................................................... 27
2.4 Structural Behavior of FRP Prestressed Bridge Girders..................................................... 28
2.4.1 Flexural Behavior of FRP prestressed Bridge Girders ............................................ 29
2.4.1.1 Factors affecting flexural failure of FRP prestressed concrete beam ....... 30
2.4.1.1.1 Ductility or Energy Absorption in FRP Prestressed Concrete
Beams........................................................................................................ 30
2.4.1.2 Previous Research on Flexural Performance of Prestressed Concrete
Beams.................................................................................................................... 33
2.4.1.2.1 Previous Research on Flexural Performance of FRP Prestressed
Concrete Beams ........................................................................................ 33
2.4.1.2.2 Previous Research on Flexural Performance of Prestressed
UHPC Beams............................................................................................ 35
2.4.2 Shear Behavior of FRP prestressed Bridge Girders................................................. 37
2.4.2.1 Background of shear stress in concrete beam........................................... 38
2.4.2.2 Shear Transfer mechanism in a concrete beams....................................... 40

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2.4.2.3 Factors Affecting Shear Failure................................................................ 41
2.4.2.3.1 Shear Span-to-Depth Ratio ........................................................ 41
2.4.2.3.2 Size Effect.................................................................................. 42
2.4.2.3.3 Concrete Strength....................................................................... 44
2.4.2.3.4 Shear Reinforcement.................................................................. 44
2.4.2.3.5 Longitudinal Reinforcement ...................................................... 46
2.4.2.3.6 Effect of Prestressing Force....................................................... 47
2.4.2.3.7 Effect of Openings in the Web................................................... 47
2.4.2.3.8 Loading Conditions.................................................................... 48
2.4.2.4 Shear cracking and failure of prestressed concrete beams........................ 48
2.4.2.4.1 Diagonal Tension Failure........................................................... 49
2.4.2.4.2 Shear Compression Failure........................................................ 49
2.4.2.4.3 Web Crushing Failure................................................................ 50
2.4.2.4.4 Shear Tension Failure ................................................................ 51
2.4.2.5 Previous Research on Shear Performance of Prestressed Concrete Beams
............................................................................................................................... 51
2.4.2.5.1 Previous Research on Shear Performance of Prestressed Concrete
Beams with Stirrups.................................................................................. 51
2.4.2.6 Previous Research on Shear Performance of Prestressed UHPC Beams . 56
2.5 Summary............................................................................................................................. 57
CHAPTER 3 AVAILABLE DESIGN GUIDELINES FOR UHPC ............................................ 58
3.1 Introduction......................................................................................................................... 58
3.2 Material Behavior of Concrete............................................................................................ 59
3.2.1 Stress-Strain Behavior of Conventional Concrete................................................... 59
3.2.1.1 ACI 318/AASHTO Model........................................................................ 59
3.2.2 Stress-Strain Behavior of Ultra High Performance Concrete (UHPC).................... 61

xi
3.2.2.1 French Model developed by AFGC and Setra.......................................... 61
3.2.2.2 Australian Model developed by Gowripalan and Gilbert (2000) ............. 64
3.2.2.3 US Federal Highway Administration (FHWA) Models........................... 65
3.2.2.4 Stress–Strain Behavior of UHPC by Vande Voort et al. (2008)............... 66
3.2.2.5 Comparison of stress-strain models.......................................................... 67
3.3 Flexural Analysis and Design of UHPC Section................................................................ 68
3.3.1 Flexural Analysis and Design of Non-Prestressed UHPC Beams........................... 69
3.3.2 Flexural Analysis and Design of Prestressed UHPC Beams ................................... 71
3.3.2.1 Nawy’s Model (2008)............................................................................... 71
3.3.2.2 Garcia’s Model (2007).............................................................................. 72
3.4 Shear Design of UHPC Section.......................................................................................... 75
3.4.1 Shear Design according to AFGC and Setra............................................................ 76
3.4.2 Shear Design according to JSCE ............................................................................. 78
3.4.3 Shear Design According to Australian Guidelines .................................................. 81
3.4.4 Shear Design Recommended by Graybeal (2006)................................................... 83
CHAPTER 4 EXPERIMENTAL PROGRAM............................................................................. 85
4.1 Introduction......................................................................................................................... 85
4.2 Design Concept and Beam Detail....................................................................................... 85
4.3 Material Used for Construction .......................................................................................... 93
4.3.1 Longitudinal Reinforcement .................................................................................... 93
4.3.2 Transverse Reinforcement ....................................................................................... 94
4.3.3 Concrete................................................................................................................... 97
4.3.4 Transverse Conduits................................................................................................. 99
4.4 Construction of Decked Bulb T beams............................................................................. 100
4.4.1 Construction of Reinforcement Cage..................................................................... 100

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4.4.2 Construction of Modular Deck System.................................................................. 103
4.4.3 Fabrication of Decked Bulb T Shape Formwork................................................... 106
4.4.4 Placement of Reinforcement Cage within Formwork ........................................... 108
4.4.5 Prestressing of CFCC Strands................................................................................ 110
4.4.6 Placement of Concretes.......................................................................................... 114
4.4.7 Curing of Concrete................................................................................................. 118
4.4.8 Deforming, Prestress Transfer and Beam Stacking............................................... 119
4.4.9 Concrete Compressive Strength Test..................................................................... 122
4.5 Instrumentation ................................................................................................................. 125
4.5.1 Strain Gages........................................................................................................... 126
4.5.2 Force Transducers (Load Cells)............................................................................. 126
4.5.3 Linear Motion Transducers.................................................................................... 127
4.5.4 Linear Variable Differential Transducer................................................................ 127
4.5.5 Data Acquisition System........................................................................................ 128
4.6 Instrumentation of Decked Bulb T Beams........................................................................ 130
4.7 Experimental Testing........................................................................................................ 135
4.7.1 Experimental Testing of Decked Bulb T beams in Shear...................................... 139
4.7.2 Experimental Testing of Decked Bulb T beams in Flexure................................... 145
4.7.3 Decompression Load Test of the Beam................................................................. 148
CHAPTER 5 RESULTS AND DISCUSSION........................................................................... 149
5.1 General Outline................................................................................................................. 149
5.2 Behavior of Decked Bulb T Beams Tested in Shear ........................................................ 150
5.2.1 Modes of Failure.................................................................................................... 152
5.2.2 Pattern of Crack Development and Shear Force-Crack Width Response.............. 158
5.2.3 Applied Load-Deflection and Shear Force–Deflection Response......................... 164

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5.2.4 Cracking Force and Ultimate Failure Force........................................................... 166
5.2.5 Shear Force-Concrete Compressive Strains Response .......................................... 169
5.2.6 Ductility Ratio........................................................................................................ 173
5.3 Flexural Behavior of Decked Bulb T Beams.................................................................... 179
5.3.1 Beam HB-100-Mid-0SS ........................................................................................ 180
5.3.2 Beam DB-132-Mid-0ES ........................................................................................ 185
CHAPTER 6 COMPARISON OF RESULTS............................................................................ 191
6.1 General Outline................................................................................................................. 191
6.2 Comparison between Experimental Results of Beams Tested in Shear ........................... 192
6.2.1 Effect of a/d Ratio on Shear Force–Deflection Response ..................................... 194
6.2.2 Effect of a/d Ratio on Cracking and Ultimate Shear Resistance ........................... 196
6.2.3 Effect of a/d Ratio on Ductility Ratio.................................................................... 198
6.2.4 Effect of a/d Ratio on the Modes of Shear Failure ................................................ 199
6.3 Comparison between Experimental Results of Beams Tested in Flexure........................ 200
6.3.1 Introduction............................................................................................................ 200
6.3.2 Comparison of applied load-deflection response................................................... 202
6.3.3 Comparison of cracking load, ultimate load and nominal moment capacity......... 203
6.3.4 Ductility Ratio........................................................................................................ 205
6.4 Comparison between Experimental and Analytical Results............................................. 206
6.4.1 Introduction............................................................................................................ 206
6.4.2 Comparison between Experimental and Analytical Results in Shear.................... 206
6.4.3 Comparison between Experimental and Analytical Results in Flexure................. 209
CHAPTER 7 SUMMARY AND CONCLUSIONS................................................................... 211
7.1 Research Summary ........................................................................................................... 211
7.2 Conclusion ........................................................................................................................ 212

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CHAPTER 8 RECOMMENDATIONS...................................................................................... 214
8.1 Recommendation for Future Studies ................................................................................ 214
REFERENCES ........................................................................................................................... 216
APPENDIX A: ANALYTICAL CALCULATIONS FOR DECKED BULB T BEAMS ......... 233
A.1 Ductal Beam Design ........................................................................................................ 234
A.1.1 Design of Ductal Beam in Flexure........................................................................ 236
A.1.1.1 Concrete Properties................................................................................ 236
A.1.1.2 Cross Sectional Properties ..................................................................... 237
A.1.1.3 Reinforcement Properties....................................................................... 243
A.1.1.3.1 Longitudinal Reinforcement Properties.................................. 243
A.1.1.3.2 Transverse Reinforcement Properties ..................................... 244
A.1.1.4 Prestress Loss Calculations.................................................................... 244
A.1.1.4.1 Initial Prestressing Force in the Beam .................................... 244
A.1.1.4.2 Prestress Loss Calculation from Experimental Decompression
Load ........................................................................................................ 244
A.1.1.4.3 Prestress Loss Calculation from Experimental Cracking Load
................................................................................................................. 245
A.1.1.4.4 Prestress Loss Calculation as per AASHTO (2010)............... 247
A.1.1.4.5 Effective Prestressing Force in the Beam ............................... 248
A.1.1.5 Stress Check during Prestress Transfer.................................................. 248
A.1.1.5.1 Stress at Mid Span................................................................... 248
A.1.1.5.2 Stress at Support...................................................................... 249
A.1.1.5.3 Stress Limit as per ACI 440.4R-04 (2004) ............................. 249
A.1.1.5.4 Stress Limit as per AASHTO (2010)...................................... 249
A.1.1.5.5 Stress Check as per ACI 440.4R-04 (2004) and AASHTO
(2010)...................................................................................................... 250

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A.1.1.6 Calculations for Neutral Axis Depth...................................................... 250
A.1.1.7 Calculations for Balanced Neutral Axis Depth...................................... 259
A.1.1.8 Mode of Flexural Failure ....................................................................... 259
A.1.1.9 Calculations for Nominal Flexural Moment.......................................... 260
A.1.1.10 Calculations for Ultimate Flexural Load for the Beam........................ 260
A.1.1.11 Calculations for Cracking Moment and Cracking Load for the Beam 260
A.1.1.12 Calculations for Camber ...................................................................... 261
A.1.2 Design of Ductal Beam in Shear........................................................................... 261
A.1.2.1 Shear Capacity as per JSCE (2006) ....................................................... 262
A.1.2.2 Shear Capacity as per AFGC (2002)...................................................... 262
A.1.2.3 Shear Capacity as per Canadian Code – Almansour and Lounis (2009)263
A.1.2.4 Shear Capacity as per Australian Code – Gowripalan and Gilbert (2010)
............................................................................................................................. 264
A.2 Hybrid Beam Design........................................................................................................ 265
A.2.1 Design of Hybrid Beam in Flexure....................................................................... 266
A.2.1.1 Concrete Properties................................................................................ 266
A.2.1.2 Cross Sectional Properties ..................................................................... 267
A.2.1.3 Reinforcement Properties....................................................................... 273
A.2.1.3.1 Longitudinal Reinforcement Properties.................................. 273
A.2.1.3.2 Transverse Reinforcement Properties ..................................... 274
A.2.1.4 Prestress Loss Calculations.................................................................... 274
A.2.1.4.1 Initial Prestressing Force in the beam..................................... 274
A.2.1.4.2 Prestress Loss Calculation from Experimental Decompression
Load ........................................................................................................ 275
A.2.1.4.3 Prestress Loss Calculation from Experimental Cracking Load
................................................................................................................. 276

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A.2.1.4.4 Prestress Loss Calculation as per AASHTO (2010)............... 277
A.2.1.4.5 Effective Prestressing Force in the Beam ............................... 278
A.2.1.5 Stress Check during Prestress Transfer.................................................. 279
A.2.1.5.1 Stress at Mid Span................................................................... 279
A.2.1.5.2 Stress at Support...................................................................... 279
A.2.1.5.3 Stress Limit as per ACI 440.4R-04 (2004) ............................. 279
A.2.1.5.4 Stress Limit as per AASHTO (2010)...................................... 280
A.2.1.5.5 Stress Check as per ACI 440.4R-04 (2004) and AASHTO
(2010)...................................................................................................... 280
A.2.1.6 Calculations for Balanced Reinforcement Ratio.................................... 280
A.2.1.7 Calculations for Balanced Neutral Axis Depth...................................... 282
A.2.1.8 Calculation for the Reinforcement Ratio of the beam ........................... 283
A.2.1.9 Mode of Flexural Failure ....................................................................... 284
A.2.1.10 Calculations for Nominal Flexural Moment........................................ 284
A.2.1.10.1 Calculation for the Depth of Neutral Axis as per Grace and
Singh (2002) Approach........................................................................... 284
A.2.1.10.2 Calculation for the Depth of Neutral Axis as per Traditional
Strain Compatibility Method .................................................................. 286
A.2.1.11 Calculations for Nominal Capacity of the Section............................... 288
A.2.1.12 Calculations for Ultimate Flexural Load for the Beam........................ 289
A.2.1.13 Calculations for Cracking Moment and Cracking Load for the Beam 289
A.2.1.14 Calculations for Camber ...................................................................... 289
A.2.2 Design of Hybrid Beam in Shear.......................................................................... 290
A.2.2.1 Shear Capacity as per JSCE (2006) ....................................................... 291
A.2.2.2 Shear Capacity as per AFGC (2002)...................................................... 291
A.2.2.3 Shear Capacity as per Canadian Code – Almansour and Lounis (2009)292

xvii
A.2.2.4 Shear Capacity as per Australian Code – Gowripalan and Gilbert (2010)
............................................................................................................................. 292

xviii
LIST OF FIGURES
Figure 1.1.1 Deficient bridges in USA (according to national bridge inventory, FHWA)............. 1
Figure 1.1.2 Corrosion of prestressed strand in box beam bridge (Naito et al. 2006).................... 2
Figure 2.2.1 Optimized model of UHPC in comparison with conventional concrete (Nishikawa
and Morita 2006)........................................................................................................................... 14
Figure 2.2.2 Typical sequence of mixing of UHPC (Graybeal 2006) .......................................... 16
Figure 2.2.3 Formation of joint due to un-proper mixing and flow of UHPC (Alessandro 2013)17
Figure 2.2.4 Two ways of UHPC placement (Courtesy: Kim et al. 2008)................................... 17
Figure 2.2.5 Proper alignment of fibers to restrict cracks in flexural members (D’Alessandro,
2013) ............................................................................................................................................. 17
Figure 2.2.6 Construction of bridge street bridge (Grace et al. 2002).......................................... 25
Figure 2.4.1 Typical shear & bending stress profile (Naaman 2004)........................................... 38
Figure 2.4.2 Principal stresses presented by Mohr’s circle for non-prestressed and prestressed
concrete element along neutral axis (Naaman 2004).................................................................... 39
Figure 2.4.3 Effect of shear span-to-depth (a/d) ratio on shear strength of concrete beam without
shear reinforcement (Laskar et al. 2010) ...................................................................................... 42
Figure 2.4.4 Types of crack formation along the span of the beams (Gilbert & Mickleborough
2005) ............................................................................................................................................. 49
Figure 2.4.5 Shear compressions failure (Rout 2013) .................................................................. 50
Figure 2.4.6 Progression of crack and web crushing failure in concrete beam under shear load setup
(Heckmann, 2008)......................................................................................................................... 50
Figure 2.4.7 Shear diagonal failure (Tadros et al. 2011) .............................................................. 51
Figure 2.4.8 Various types of failure modes observed in test beams (Park and Naaman 1999) (a)
shear-tendon rupture failure; (b) shear-tension failure; (c) shear-compression failure; and (d)
flexural-tension failure.................................................................................................................. 53
Figure 2.4.9 Experimental results of test beams investigated by Rout (2013) ............................. 55
Figure 3.2.1 Equivalent Whitney stress block recommended by ACI/AASHTO ........................ 60
Figure 3.2.2. Strain hardening (a) and strain softening (b) Law of AFGC and Setra (2002) for
UHPC at the serviceability limit state........................................................................................... 62
Figure 3.2.3. Stress-strain relationship for ductal section (a) with reinforcement and (b) without
reinforcement (Gowripalan and Gilbert 2000) ............................................................................. 64

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Figure 3.2.4. Stress-Strain behavior of UHPC according to (a) Garcia (2007) Model and (b)
Graybeal (2008) Model................................................................................................................. 65
Figure 3.2.5 Trilinear stress – strain behavior of UHPC given by Vande Voort et al. (2008) ..... 67
Figure 3.2.6. Modified AFGC-Setra Stress-Strain Model developed by Steinberg (2010).......... 68
Figure 3.3.1. Flexural Strain and Stress Distribution for Non-Prestressed UHPC Beam (Almansour
and Lounis, 2009) ......................................................................................................................... 70
Figure 3.3.2. Experimental and simplified stress strain behavior of UHPC (Garcia 2007) ......... 73
Figure 3.3.3. Internal Stress Behavior for Prestressed UHPC Section (Garcia 2007).................. 74
Figure 4.3.1. Carbon Fiber Composite Cable (CFCC) Roll ......................................................... 94
Figure 4.3.2. Stirrup type A [Dimension in inch (mm)]............................................................... 95
Figure 4.3.3. Stirrup type B [Dimension in inch (mm)] ............................................................... 95
Figure 4.3.4. Stirrup type C [Dimension in inch (mm)] ............................................................... 96
Figure 4.3.5. Mixing of ingredient and production of UHPC for the construction of beams at Center
for Innovative Material Research (CIMR), LTU.......................................................................... 98
Figure 4.3.6. Fabrication of transverse conduit used in hybrid beams at interior diaphragm ...... 99
Figure 4.4.1. Process of construction of hybrid beam reinforcement cage over wooden zig..... 101
Figure 4.4.2. Completed hybrid beam reinforcement cage......................................................... 102
Figure 4.4.3 Various components of modular deck system........................................................ 104
Figure 4.4.4 Completion of modular deck system construction ................................................. 105
Figure 4.4.5. Fabrication of decked bulb T beam shape formwork from styrofoam.................. 107
Figure 4.4.6 Construction of hybrid beam formwork with reinforcement cage......................... 109
Figure 4.4.7 Construction of ductal beam with reinforcement cage........................................... 110
Figure 4.4.8 Various components of anchorage system to prestress CFCC strands................... 111
Figure 4.4.9 Process involved in pretensioning of prestressing strands of beams...................... 112
Figure 4.4.10 Placement of concrete in hybrid beam ................................................................. 115
Figure 4.4.11 Placement of UHPC in ductal beam..................................................................... 116
Figure 4.4.12 Measurement of workability of HSC (Cone Test) ............................................... 117
Figure 4.4.13. Measurement of workability of UHPC................................................................ 117
Figure 4.4.14 Curing of beam..................................................................................................... 118
Figure 4.4.15 Deforming, prestress transfer and stacking of hybrid beam................................. 119
Figure 4.4.16 Deforming, prestress transfer and stacking of ductal beam ................................. 120

xx
Figure 4.4.17 Monitoring of prestressing force in ductal beam.................................................. 121
Figure 4.4.18 Concrete cylinders for compressive strength test................................................. 122
Figure 4.4.19 Increase of average compressive strength of concrete with curing...................... 124
Figure 4.4.20 Increase of average split tensile strength of UHPC with curing .......................... 124
Figure 4.4.21 Failure of concrete cylinders under compression and tension.............................. 125
Figure 4.5.1 Typical linear strain gage (Vishay Instruments, http://www.vishaypg.com/micro-
measurements/stress-analysis-strain-gages/linear-pt250-2) ....................................................... 126
Figure 4.5.2 Load cell used for monitoring forces...................................................................... 127
Figure 4.5.3 Linear Motion Transducer...................................................................................... 127
Figure 4.5.4 Typical rosette arrangement of LVDT on web of the beam................................... 128
Figure 4.5.5 Data acquisition system.......................................................................................... 129
Figure 4.5.6 Typical setup of data acquisition system during experimental investigation......... 130
Figure 4.6.1 Typical external instrumentation on the hybrid beam............................................ 131
Figure 4.6.2 Typical external instrumentation on the ductal beam............................................. 132
Figure 4.6.3 Typical internal instrumentation on the ductal beam ............................................. 132
Figure 4.7.1 Chronological order of experimental test conducted on beams ............................. 137
Figure 4.7.2 Schematic presentation of experimental test conducted on the hybrid beam and ductal
beam............................................................................................................................................ 138
Figure 4.7.3 Typical shear test setup for decked bulb T beams.................................................. 139
Figure 4.7.4 Shear test setup for beam HB-100-3-0SS............................................................... 140
Figure 4.7.8 Shear test setup for beam DB-132-3-0ES .............................................................. 144
Figure 4.7.9 Shear test setup for beam DB-132-4-0ES .............................................................. 145
Figure 4.7.10 Typical flexure test setup for decked bulb T beams............................................. 146
Figure 4.7.11 Typical setup of hybrid beam for flexure test ...................................................... 147
Figure 4.7.12 Typical setup of ductal beam for flexural test...................................................... 147
Figure 4.7.13 Strain gage installed on the soffit of the beam for decompression test................ 148
Figure 5.2.1 Shear diagonal failure observed in beam HB-100-3-0SS....................................... 153
Figure 5.2.2 Shear diagonal failure observed in beam HB-100-4-0SS....................................... 154

xxi
Figure 5.2.3 Compression flexural failure observed in beam HB-100-5-0SS............................ 155
Figure 5.2.4 Compression flexural failure observed in beam HB-100-6-0SS............................ 156
Figure 5.2.5 Diagonal shear failure observed in beam DB-132-3-0ES ...................................... 157
Figure 5.2.6 Diagonal shear failure of observed in beam DB-132-4-0ES.................................. 158
Figure 5.2.7 Crack pattern observed in beam HB-100-3-0SS .................................................... 161
Figure 5.2.8 Crack pattern observed in beam HB-100-4-0SS .................................................... 161
Figure 5.2.9 Crack pattern observed in beam DB-132-3-0ES.................................................... 162
Figure 5.2.10 Crack pattern observed in beam DB-132-4-0ES.................................................. 162
Figure 5.2.11 Shear force – crack width of hybrid beams at a/d ratio of 3 and 4....................... 162
Figure 5.2.12 Shear force – crack width of ductal beams at a/d ratio of 3 and 4 ....................... 163
Figure 5.2.13 Comparison of crack width development between UHPC and HSC in hybrid beam
at a/d ratios of 4........................................................................................................................... 163
Figure 5.2.14 Applied load – deflection response of all hybrid beams tested in shear at varying a/d
ratio ............................................................................................................................................. 165
Figure 5.2.15 Shear force – deflection response of hybrid beams failed in shear at a/d ratio of 3
and 4............................................................................................................................................ 165
Figure 5.2.16 Shear force – deflection response for ductal beam in shear at varying a/d ratio.. 166
Figure 5.2.17 Cracking load and ultimate failure load of all hybrid beams tested in shear at varying
a/d ratios...................................................................................................................................... 168
Figure 5.2.18 Cracking shear forces for all hybrid beam and ultimate shear force for the hybrid
failed in shear at varying a/d ratio............................................................................................... 168
Figure 5.2.19 Comparison of cracking and ultimate shear resistance of ductal beams tested in shear
at varying shear span-to-depth ratio............................................................................................ 169
Figure 5.2.20 Comparison between maximum concrete compressive strains observed along the
span at three different locations for hybrid beams tested in shear at varying a/d ratio............... 171
Figure 5.2.21 Shear force – maximum top flange concrete compressive strain response for hybrid
beams tested in shear at varying shear span-to-depth ratio......................................................... 172
Figure 5.2.22 Shear force – top flange concrete compressive strain observed in ductal beam tested
in shear at varying shear span-to-depth ratio .............................................................................. 172
Figure 5.2.23 Shear force–tensile strain response of bottom prestressing strand of ductal beam
tested in shear at varying a/d ratio .............................................................................................. 173

xxii
Figure 5.2.24 Ductility ratio for beam HB-100-3-0SS ............................................................... 175
Figure 5.2.25 Ductility ratio for beam HB-100-4-0-SS.............................................................. 175
Figure 5.2.28 Ductility ratio for beam DB-132-3-0ES............................................................... 177
Figure 5.2.29 Ductility ratio for beam DB-132-4-0ES............................................................... 177
Figure 5.2.30 Comparison between ductility ratios experienced by hybrid test beams in shear at
varying shear span-to-depth ratio................................................................................................ 178
Figure 5.2.31 Comparison between ductility ratios experienced by ductal test beams in shear at
varying shear span-to-depth ratio................................................................................................ 178
Figure 5.3.1 Crack pattern observed in beam HB-100-Mid-0SS before ultimate flexural test .. 182
Figure 5.3.2 Applied load – deflection response for beam HB-100-Mid-0SS ........................... 182
Figure 5.3.3 Flexural compression failure of beam HB-100-Mid-0SS ...................................... 183
Figure 5.3.4 Applied load-concrete compressive strain response for beam HB-100-Mid-0SS.. 183
Figure 5.3.5 Applied load-tensile strain response for HB-100-Mid-0SS ................................... 184
Figure 5.3.6 Applied load – Concrete strain at the soffit for beam HB-100-Mid-0SS............... 184
Figure 5.3.7 Applied load – deflection response for beam DB-132-Mid-0ES........................... 187
Figure 5.3.8 Crack pattern observed in beam DB-132-Mid-0ES ............................................... 187
Figure 5.3.9 Flexural tension failure of the beam DB-132-Mid-0ES......................................... 188
Figure 5.3.10 Applied load – Concrete compressive strain response for DB-132-Mid-0ES ..... 189
Figure 5.3.11 Applied load – Tensile strain response for DB-132-Mid-0ES............................. 189
Figure 5.3.12 Ductility ratio for beam DB-132-Mid-0ES .......................................................... 190
Figure 5.3.13 Applied load – Concrete strain at the soffit for beam HB-100-Mid-0SS............. 190
Figure 6.2.1 Comparison of shear force – deflection response of hybrid beams and HSC beams
reinforced with CFCC stirrups as investigated by Rout (2013) under similar a/d ratios............ 195
Figure 6.2.2 Comparison of shear force – deflection response of hybrid beams and HSC beams
reinforced with steel stirrups as investigated by Rout (2013) under similar a/d ratios............... 196
Figure 6.2.3 Comparison of cracking and ultimate shear forces of hybrid, ductal & HSC beams
investigated by Rout (2013) under similar a/d ratios.................................................................. 197
Figure 6.3.1 Comparison between applied load – deflection response of ductal and HSC beams
investigated by Grace et al. (2015) under similar flexure load setup ......................................... 203

xxiii
Figure 6.3.2 Comparison between cracking load, ultimate load and nominal moment capacity of
ductal and HSC beams investigated by Grace et al. (2015) under similar flexure load setup.... 204

xxiv
LIST OF TABLES
Table 2.2.1 Mix design of various types of UHPC (Russell and Graybeal, 2013)....................... 13
Table 2.2.2 Tensile strength of UHPC according to various test (Graybeal 2006) ...................... 18
Table 2.4.1 Failure modes for FRP reinforced beams based on energy ratio (Grace et al. 1998) 32
Table 3.2.1 Stress – Strain behavior of UHPC by Vande Voort et al. (2008).............................. 66
Table 4.3.1. Material properties of longitudinal reinforcement used in beams............................ 93
Table 4.3.2. Material properties of transverse reinforcement used in beams ............................... 96
Table 4.3.3. Mix design for HSC per cubic yard (Mc Coig Co., MI)........................................... 97
Table 4.3.4. Mix design for UHPC per cubic yard (Lafarge, North America)............................. 97
Table 4.4.1. Material properties of styrofoam used in the construction of beams...................... 106
Table 4.4.2 Elongation measured on prestressing strands .......................................................... 113
Table 4.4.3. Average strength of concrete cylinders .................................................................. 123
Table 4.6.1 Various sensor types & their respective locations in the beam ............................... 133
Table 4.7.1 Nomenclature of test beams..................................................................................... 137
Table 5.2.1 Summary of experimental results of all test beams in shear.................................... 151
Table 5.2.2 Summary of concrete strain experienced by all test beams in shear ....................... 171
Table 5.2.3 Comparison between ductility ratios experienced by all test beams in shear varying
shear span-to-depth (a/d) ratio .................................................................................................... 179
Table 6.2.1 Comparison of experimental results of hybrid beam and HSC decked bulb T beams
investigated by Rout (2013) in shear .......................................................................................... 194
Table 6.2.2 Summary of inelastic energy, elastic energy and ductility ratio experienced by hybrid
beams and HSC beams tested in shear........................................................................................ 199
Table 6.3.1 Comparison between ductal and HSC beams tested in flexure ............................... 202
Table 6.3.2 Summary of inelastic energy, elastic energy and ductility ratios experienced by ductal
and HSC beams tested in flexure................................................................................................ 205
Table 6.4.1 Comparison between experimental and analytical results of hybrid and ductal beams
tested in shear.............................................................................................................................. 209
Table 6.4.2 Comparison between experimental and analytical results for the hybrid and ductal
beams tested in flexure................................................................................................................ 210

1
CHAPTER 1 INTRODUCTION
1.1 Statement of the Problem
One out of nine bridges in the United States is rated structurally deficient (ASCE 2013) and needs
major improvement ranging from deck replacement to complete reconstruction. According to a
recent 2013 America’s infrastructure report cards conducted by the American Society of Civil
Engineers, the United States consists of 607,380 bridges, out of which 66,749 bridges are
structurally deficient and 84,748 bridges are functionally obsolete (ASCE 2013). Figure 1.1.1
shows the statistics of structurally deficient and functionally obsolete bridges till 2012. Thus, based
on the present state of condition and performance, the United States bridges hold a Grade Point
Average (GPA) score of C+
from the scale of A to F and need $20.5 billion each year to eliminate
backlog of bridge deficiency by the year 2028 as estimated by the Federal Highway Administration
(FHWA). Therefore, in future applications, design engineers seeks a new and better way to build
bridges which require less maintenance and budget over a longer period.
Figure 1.1.1 Deficient bridges in USA (according to national bridge inventory, FHWA)
0
100
200
300
400
500
600
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
0
100
200
300
400
500
600
NumberofBridges(inthousands)
Year
NumberofBridges(inthousands)
# Total Bridges # Structural Deficient # Funtional Obsolete # Total Deficient Bridges

2
Since 1950, steel prestressed side-by-side box-beam bridges have been a popular choice of precast
prestressed bridges. This type of bridges was preferred due to its typical cross-sectional properties
of smaller beam depth-to-span ratio. According to Precast Concrete Institute (PCI), the primary
reasons for the gradual deterioration of the service lifespan of the bridges are mainly due to a)
increase in the vehicle sizes, weights and traffic volumes; b) faster degradation of conventional
concrete due to their low strength and durability, and c) the most important factor is the corrosion
of steel reinforcement due to severe environmental conditions. Figure 1.1.2 shows corrosion of
prestressed steel stands in the box beam bridge system (Naito et al. 2006).
Figure 1.1.2 Corrosion of prestressed strand in box beam bridge (Naito et al. 2006)
In today’s 21st
century of groundbreaking advancement in the field of research and development,
various engineers have found several alternative bridge beam cross-sections followed by different
methodologies for the construction and numerous types of innovative materials to address the
aforementioned problems associated with the bridge construction industry. The significant
breakthrough in the concrete technology so far with the greatest power to transform product design
and service life of the precast concrete industry in the U.S. is Ultra High Performance Concrete
(UHPC) as a concrete and Fiber Reinforced Polymer (FRP) as a reinforcement. Both of these
materials are relatively new in the field of construction. Their superior performance in terms of
strength, durability, long-term stability exhibited a greater ability to produce groundbreaking and
innovative structure which is still under research. In addition, FRP possesses immense potentials

3
and advantages over steel as a reinforcement, owing to their distinguishable properties such as
non-corrosive nature, low relaxation, superior in fatigue, lighter in weight and higher ultimate
tensile strength or higher strength to weight ratio. But due to FRP linear stress-strain material
characteristics, all structural element either longitudinally (reinforced/prestressed strands) or
transversely (stirrups) or both reinforced with FRP are prone to catastrophic brittle failure with a
sign of abrupt rupture of either strands or stirrups or both without showing any yielding, unlike
steel. Therefore, all FRP reinforced/prestressed structural elements are encouraged for over-
reinforced design section (ACI 440.1R-06 2006) to prefer a more comparatively ductile failure
through concrete compression flexural failure. Similarly, in order to prevent sudden collapse of
the concrete structure by shear due to lack of proper and adequate placement of stirrups (either
steel or FRP) (Mitchell et al. 2011), beam sections were mostly over-reinforced with stirrups to
resist maximum anticipated shear stresses. This possibly changes the catastrophic shear failure into
a more favorable flexural failure with sufficient warning of failure in terms of large noticeable
deflection and cracking prior to collapse.
1.2 Hybrid and Ductal Precast Prestressed Decked Bulb T-Beams
The present research investigation introduces two state-of-the-art long lasting corrosion free
innovative precast prestressed decked bulb T beams prestressed with Carbon Fiber Composite
Cables (CFCC) as a replacement to traditional HSC box beams or T beams exhibiting potential
sudden shear and flexural failure. The two types of CFCC prestressed decked bulb T beam
proposed through the present research investigation are: hybrid beam, and ductal beam. These
beams are efficiently constructed with Ultra High Performance Concrete (UHPC) without using
stirrups either at critical shear span or throughout the entire span of the beam. The hybrid and
ductal beam adopt the state-of-the-art decked bulb T beam design as proposed by Grace et al.
(2012) for precast prestressed beams. Bridges made of side-by-side box beam lack space for
inspections to the critical elements which leads to the unexpected failure of the bridge. Thus, Grace
et al. (2012) proposed decked bulb T-beam bridge system which are inbuilt with deck and provides
space underneath the bridge system for inspection. The hybrid beam is constructed by placing
UHPC without stirrups in the critical shear span of the beam at both ends. The middle flexural
span of the beam was constructed with High Strength Concrete (HSC) with stirrups. The hybrid
beam address the use of UHPC without shear stirrups in the critical shear span of CFCC

4
reinforced/prestressed decked bulb T beams to mitigate potential sudden shear failure of the
bridges. Whereas, the ductal beam mitigates potential sudden flexural failure of under-reinforced
CFCC prestressed decked bulb T beams without using any shear reinforcement throughout the
span. In addition, ductal beam efficiently reduces the beam cross-sectional area and designed as
under-reinforced beam in order to reduce the consumption of expensive UHPC and CFCC
material. Further, the ductal and hybrid beams were easy to build, long lasting and require less
maintenance.
In total, hybrid and ductal beams proposes following eight advantages as listed below:
Advantage 1: Mitigates either the shear or flexural sudden failure of FRP reinforced/prestressed
bridge system by enhancing their shear capacity, inelastic energy absorption and deflection with
profound cracking or warning of failures before collapse.
Advantage 2: Efficient utilization of the expensive UHPC and CFCC materials. The consumption
of UHPC is reduced either by reducing the cross-sectional area of the beam or by employing only
within the highly stressed regions such as critical shear span along the beam length. The amount
of reinforcement is reduced by reducing the cross-sectional area of the beam. Thus, building an
efficient, stronger and lighter bridge girders.
Advantage 3: Eliminates shear stirrups either partially in the critical shear span or completely
throughout the entire span. This makes the construction of reinforcement cage easier and faster.
This also helps in solving the workability issues such as the development of concrete voids or
honeycombs due to the congestion of the reinforcement cage.
Advantage 4: Increase in the span-to-depth ratio of the beam. The use of UHPC which possesses
superior characteristic compressive and tensile strength in comparison with HSC in the critical
shear span of the beam increases the ability of the beam to sustain higher bursting forces generated
due to higher prestressing force in the beam leading to lighter and longer beams.
Advantage 5: Replaces the traditional corrosive steel reinforcement with Carbon Fiber Composite
Cables (CFCC) which are non-corrosive, low relaxation, lighter in weight and higher in ultimate
tensile strength properties.

5
Advantage 6: Generates the valuable experimental research data for the UHPC beam section
reinforced/prestressed with FRP for the development of a unified design guidelines and codes.
Advantage 7: Provides a sufficient gap on both sides and bottom of the hybrid or ductal beam
bridge system for the passage of utilities and helps in visual inspection and maintenance of any
progressive damage caused due to corrosion.
Advantage 8: Provides an inbuilt deck on bridge girders which eliminates the on-site preparation
and construction time. Thus, it accelerates on-site construction of bridge and involves less
disruption in the normal flow of traffic.
1.3 Motivation
Even after decades of experimental research and latest use of highly sophisticated computational
tools, the shear transfer mechanism has always been a complex phenomenon to understand in depth
due to the involvement of large number of variables. The shear behavior of structural members has
always been a point of discussion among researchers, and even it becomes worse when several
issues associated with the use of stirrups are involved in the studies such as: (a) shear capacity of
a section increases with decreasing the spacing between the stirrups. However, various code limit
the minimum spacing or maximum use of stirrups to avoid the congestion of reinforcement cage,
b) Vulnerability of steel stirrups towards corrosion, c) Reduction in tensile strength of CFCC
stirrups due to bend effect (Rout 2013), d) limitation on the maximum spacing of stirrups to avoid
wider shear cracks especially in prestressed concrete section. The use of steel fibers in
reinforced/prestressed concrete members is a viable alternative solution for increasing the shear
capacity of the section without using stirrups. According to Imam et al. (1997), the shear capacity
of concrete section increases comparatively at a higher rate with increasing the amount of steel
fiber than increasing in their nominal flexural capacity (Mn). Depending upon the percentage of
use of steel fibers, steel fibers are capable of increasing the shear capacity up to their nominal
flexural capacity (Mu = 100% Mn) (Russo et al. 1991) which ultimately leads to more of a ductile
shear/flexural failure. Thus, the mode of sudden brittle shear failure in a beam can be mitigated
into a ductile flexural failure by utilizing steel fibers in a normal strength concrete section.
According to Park and Naaman (1999), prestressed concrete beams with fiber reinforced polymer
(FRP) tendons are susceptible to shear-tendon rupture failure. The shear-tendon rupture failure is

6
a unique mode of failure caused due to rupture of tendon initiated by dowel shear action acting on
the shear-cracking plane. This phenomenon is observed due to the FRPs linear stress-strain
characteristics and low shear resistance in transverse direction. Park and Naaman (1999) also
recommended that addition of steel fibers in the concrete section can possibly reduce the unique
shear-tendon rupture failure of FRP reinforced/prestressed concrete beams by enhancing their
section shear capacity. Padmarajaiah and Ramaswamy (2001) conducted a rigorous experimental
and analytical work on 13 fully/partially prestressed high-strength concrete beams to study the
influence of fiber content, location of fiber, and the presence/absence of stirrups within the shear
span on the shear behavior of the beam. It was reported that the beams having fibers located only
within the shear span and over the entire cross-section exhibited a similar load-deformation
response and ultimate load to that of beams which had fibers over the entire span. The presence of
fibers within the shear span altered the brittle shear failure to more of a ductile flexure failure.
Thus, it was recommended that the stirrups can be replaced with an equivalent amount of fibers in
the shear span without compromising the overall structural performance of the member. Therefore,
in order to overcome the corrosion problems of steel and the issues on the use of stirrups, it is a
peak time to propose a structure with an innovative design which utilizes the newly developed
construction material i.e. UHPC and CFCC in a more efficient and economical way in solving this
present issues in bridge construction. In addition to the above point, Taylor et al. (2011) conducted
a life cycle cost analysis for bridge girders and recommended that UHPC are expected to provide
at least twice the service life and low cost of maintenance as expected from the conventional
strength concrete compensating the higher initial investment in long term. Similarly, Grace et al.
(2012) demonstrated through the life cycle cost analysis that CFRP bridges are more cost effective
and maintenance free than the traditional steel bridges.
1.4 Research Significance
The present research investigation presents a new technique to construct bridge girders by adopting
the state-of-art decked bulb T-beam design proposed by Grace et al. (2012) for precast prestressed
concrete beams. Newly developed materials i.e. UHPC as concrete and CFCC as reinforcement,
is used in the present research investigation in the construction of bridge girder. The present
research investigation brings an idea of efficient and economical use of costly material through
section hybridization and optimization. Through this novel concept, in addition to the earlier

7
advantages of decked bulb T-beams such as inbuilt deck and open spaces between beams for
inspection and utilities, these proposed decked bulb T-beams make an attempt to mitigate potential
sudden shear and flexural failures of FRP prestressed beams individually by utilizing UHPC and
CFCC efficiently and economically. In order to satisfy the motive of the research investigation,
two kinds of beams are proposed and named as the hybrid and the ductal beams. The hybrid beam
brings the concept of hybrid formulation between two different types of concrete i.e. UHPC and
HSC at different zone/span along the length of the beam to mitigate catastrophic shear failure by
increasing inelastic energy absorption and shear capacity of the beam. On the other hand, ductal
beam brings the concept of section optimization of full UHPC beam section and suggests an
alternative approach to mitigate potential sudden flexural failure for under-reinforced FRP
reinforced/prestressed beam section. Due to the enhanced tensile capacity and the involvement of
steel fibers in the UHPC, it is anticipated that the under-reinforced UHPC beam with FRP
reinforcement will tend to increase the energy absorption or ductility ratio of the beam and will
exhibit more of a ductile flexural failure with ample signals or warning of aloud fiber pullouts
along with excessive cracks and deflection before collapse. The objective behind the study of
ductal beam is to decrease the consumption of UHPC and CFCC reinforcement by reducing the
cross-sectional area in comparison with hybrid beam and cut down the cost of construction by
saving costlier materials and labor manpower. In addition, partial or complete elimination of shear
stirrups in the hybrid and ductal beams also helps in easier and faster construction of reinforcement
cage. The partial or complete elimination of stirrups also relieves concrete workability issues such
as the development of voids or honeycombs which are caused due to improper placement of
concrete in the congested reinforcement cage.
At present, there is no extensive research conducted in the past to mitigate sudden shear and
flexural failure of FRP reinforced/prestressed concrete. In addition, there are no domestic and
international unified design guidelines and codes for the construction of bridge beams with UHPC
and FRPs. Therefore, the experimental data generated through the present research investigation
on these proposed beams will help in developing unified design guidelines and codes for the UHPC
beam section reinforced/prestressed with FRP. Finally, the observed experimental results were
compared with various applicable available design guidelines and codes to determine their level
of conservatism. Therefore, it is of utmost importance and necessary to conduct a complete

8
research investigation on the structural behavior of CFCC decked bulb T-beam constructed with
UHPC and prestressed with CFCC for the Accelerated Bridge Construction (ABC) industry.
1.5 Research Objectives
The primary objective of this research investigation is to mitigate the potential sudden flexural and
shear failure of FRP reinforced/prestressed decked bulb T-beams by employing UHPC and CFCC.
In order to accomplish the objective of the study, the following study was carried out as outlined
below:
A) To study the effect of change in the shear span-to-depth ratio on the shear behavior,
cracking shear resistance, ultimate shear capacity and their modes of failure on the hybrid
and ductal beam.
B) To examine the effect of eliminating shear stirrups either partially or completely in a CFCC
prestressed decked bulb T-beams.
C) To evaluate the flexural behavior, cracking and the ultimate flexural capacity of hybrid and
ductal beams.
D) To compare the experimental results of the hybrid and ductal beams with the experimental
results of a similarly reinforced HSC beams investigated by Rout (2013) & Grace et al.
(2015).
E) To compare the various applicable design guidelines and code for predicting the shear and
flexural capacities of UHPC beams prestressed with CFCC.
1.6 Scope of Work
The scope of present research study consisted of conducting experimental investigation and
analytical analysis on decked bulb T-beams constructed with UHPC and reinforced/prestressed
with CFCC. The experimental investigation included construction of two hybrid beams and one
ductal beam. All three beams were 41 ft. (12.25 m) long, with effective span of 40 ft. (12.19 m).
Both the hybrid and ductal beams were subjected to different shear and flexural load configuration.
Further, to provide a better comparative assessment on the performance of the beams under shear
and flexural load, the experimental results of the hybrid and ductal beams were compared with the
experimental results of a similarly reinforced HSC beams investigated by Rout (2013) and Grace
et al. (2015) under similar load configurations. An analytical calculation was developed which

9
determines the flexural capacity of the ductal beam. Finally, a comparative study was carried out
between the results obtained through the experimental investigation and the analytical methods
using applicable design guidelines and codes for UHPC.
1.7 Thesis Outline
The detailed outline of the thesis is described as follows:
Chapter 2: This chapter presents the available literature on the material characteristic of UHPC
and FRP/CFCC and the flexural/shear behavior of reinforced and prestressed concrete
members built from these material.
Chapter 3: This chapter deals with the available design guidelines for the flexural/shear design of
prestressed/reinforced concrete members with FRP and UHPC.
Chapter 4: A detailed experimental investigation is presented in this chapter, including detail
description of the materials used, construction, instrumentation, test setup, and the test
procedure of the hybrid and ductal decked bulb T-beams.
Chapter 5: This chapter presents the detailed discussion of the experimental results for each
individual test conducted on hybrid and ductal beams.
Chapter 6: This chapter compares the experimental test results of the hybrid and the ductal beams
tested in shear and flexure with HSC decked bulb T-beams investigated Rout (2013)
and Grace et al. (2015) tested under similar load configurations. And finally, the
experimental results of both hybrid and ductal beams were compared with predicted
results obtained from available design guidelines and codes.
Chapter 7: This chapter presents the summary and conclusions based on the research investigation.
Chapter 8: This chapter presents recommendations for future studies.
Appendix A: Detailed flexural/shear design calculations according to the applicable design
guidelines and code are presented in this appendix.

10
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction
The prestressed concrete industry has witnessed different types of alternative concrete and
reinforcement for decades. One of the greatest technological and research breakthrough in the field
of construction is the evolution of Ultra High Performance Concrete (UHPC) as the strongest fiber
reinforced concrete with minimum compressive strength of 21 ksi (144.8 MPa) and Fiber
Reinforced Polymer (FRP) as the non-corrodible reinforcement. Both of these emerging materials
possess huge potentials in terms of strength, durability and long term stability. Their ability to
produce revolutionary innovative structures are still under research. Presently, both materials have
limited market application, primarily due to the unavailability of unified design guidelines and
limited research data. Because of the above mentioned issues, the cost of both innovative materials
is extremely high as compared to other available construction materials and carries a very less
limited market application. Hence, the best possible way to increase their market application is by
developing a unique, innovative, and an optimized structure by exploiting the use of these costlier
materials according to their needs and locations. At the same time, these innovative structures
should also provide a very similar or superior behavior than the structures built with the traditional
materials before. Thus, it is of utmost importance to propose an optimized design of the structure
which aims at significantly reducing the cost of construction without compromising the structural
behavior.
Therefore, the present research investigation focuses on prestressed concrete bridge girders by
introducing the concept of hybridization and optimization of expensive concrete and reinforcement
i.e. UHPC and CFCC, respectively. These bridge girders should mitigate catastrophic shear and
flexural failure of CFCC prestressed High Strength Concrete (HSC) bridge girders by increasing
section capacity and inelastic energy absorption. Further, the structural behavior of these beams
are studied under various loading scenarios; shear and flexural load respectively. The present
chapter reviews literature in four broad categories such as available innovative material for
prestressed concrete beams construction, application of available innovative material, bond
strength of UHPC, and the structural behavior of FRP prestressed concrete beams. The subsequent
sections therefore reviews all the available literature currently accessible through various technical
journals published by the American Society of Civil Engineers (ASCE), the American Concrete

11
Institute (ACI), the Transportation Research Board (TRB), the Precast Prestressed Concrete (PCI),
and proceedings of national and international conferences. Section 2.2 discusses various types and
grades of concrete and reinforcements available till date in the market for the construction of
precast prestressed concrete bridges. Section 2.3 discusses various applications of the available
innovative materials towards the development of Accelerated Bridge Construction (ABC)
industry. Section 2.4 discusses the bond strength of UHPC. Lastly, section 2.6 discusses the
structural behavior of prestressed concrete beams constructed from various types and grades of
concrete and reinforcement, and the factors which affects their behavior.
2.2 Available Innovative Materials for Prestressed Bridge Girders
Prestressed concrete is mainly composed of concrete and prestressed reinforcement with or
without non-prestressed reinforcement. In today’s 21st
century of groundbreaking advancement in
the field of research and development, engineers have found several types of innovative concrete
and reinforcement to address the various challenges associated with the bridge construction
industry as mentioned earlier. The most significant concrete technological breakthrough yet with
the greatest power to transform design and service life of the precast prestressed concrete industry
is the development of UHPC as concrete and FRP as reinforcement. Both of these are newly
developed emerging materials in the field of construction. Their superior performance in terms of
strength, durability, long term stability showed an ability to produce groundbreaking, innovative
structure which is still undefined and undiscovered by researchers. Following section in this
chapter will discuss in detail various types and material characteristics of concrete and
reinforcement as a construction material for precast prestressed concrete bridges currently
available in the market.
2.2.1 Concretes
Due to technological breakthrough and research advancement, there has been a consistent
development in the concrete technology. Concrete can be classified as Normal Strength Concrete
(NSC), High Strength Concrete (HSC), Ultra High Performance Concrete (UHPC), etc. ACI 363R-
92 defines HSC as concrete which are made using conventional material, admixture, and
techniques, having specified compressive strength for design of at least 6,000 psi (40 MPa).
Subsequent sub-sections discusses Ultra High Performance Concrete (UHPC) which is important
in the present research investigation.

12
2.2.1.1 Ultra High Performance Concrete (UHPC)
Ultra High Performance Concrete (UHPC) is defined as a concrete having characteristic strength
in excess of 20 ksi (150 MPa) using steel fibers that result in a ductile behavior. Due to a very low
water-cement ratio of less than 0.25 (Nematollahi et al. 2012), major portion of portland cement
particles in UHPC remain un-hydrated and unreacted, making it to behave as fine aggregates with
a particle size ranging from 150 μm to 600 μm. AFGC-SETRA (2002) defines UHPC as “concrete
matrix having compressive strength above 21.7 ksi (150MPa) and internally reinforced with fiber
to ensure non-brittle behavior, with very low water to cementitious material ratio and with minimal
or no coarse aggregates”. Graybeal (2006) defines UHPC class materials as “cementitious-based
composite materials with discontinuous fiber reinforcement, compressive strengths above 21.7 ksi
(150 MPa), pre- and post-cracking tensile strengths above 0.72 ksi (5 MPa), and enhanced
durability via their discontinuous pore structure”. While according to the United States ongoing
ACI 239 design guidelines (2011), UHPC is definition as “concrete that has a minimum specified
compressive strength of 22 ksi (150 MPa) with specified durability, tensile strength, ductility and
toughness requirements; fibers are generally included to achieve specified requirements”. This
section is further subdivided into a multiple number of sub-sections which define characteristic
properties of UHPC.
2.2.1.1.1 Types of UHPC and mix design
Ultra High Performance Concrete (UHPC) is the concrete of new generation which is also known
as Rapid Powder Concrete (RPC) (Nematollahi et al. 2012). In Early 1990s, two separate groups
from France discovered UHPCs. Eiffage group in corporation with Sika created BSI while
Boygues in partnership with Lafarge produced Ductal. Both of these materials have the same
material properties. They both exhibit similar behavior with the only difference in their name. In
1986, Aarup reported a special fiber reinforced high performance concrete called CRC and was
developed by Aalborg Portland. A new class of UHPC material called Cor-Tuf was reported by
the U.S. Army Corps of Engineer at Engineer Research and Development Center. The present
research investigation uses Ductal as the main type of UHPC since Lafarge is the major distributor
in the North America. Depending upon the types of suppliers, various types of concrete mix design
for UHPC exist. Russell and Graybeal (2013) carried out a detailed study to analyze various types
of UHPC and their mix design currently available in the market as presented by the Table 2.2.1.

13
Table 2.2.1 Mix design of various types of UHPC (Russell and Graybeal, 2013)
Supplier
Material
Ductal
(by Lafarge)
CRC
(by Aalborg
Portland)
UHPC
(by Teichmann et al. 2002)
Cor-Tuf
(by US army corps
of engineers)
CEMTEC
(by Rossi)
Mix 1 Mix 2
lb/yd3
(kg/m3
)
(% by Weight)
% by Weight lb/yd3
(kg/m3
) lb/yd3
(kg/m3
) % by Weight lb/yd3
(kg/m3
)
Portland Cement 1200 (712) (28.5) 1.0 1235 (733) 978 (580) 1.0 1770 (1050)
Fine Sand 1720 (1020) (40.8) 0.92 1699 (1008) 597 (354) 0.967 866 (514)
Silica Flour - - - - 0.277 -
Silica Fumes (390) (231) (9.3) 0.25 388 (230) 298 (177) 0.389 451 (268)
Ground Quartz* (355) (211) (8.4) 0.25
308 (183) 503 (131)
- -
0 (0) 848 (325)
HRWRA** (51.8) (30.7) (1.2) 0.0108 55.5 (32.9) 56.2 (33.4) 0.0171 74 (44)
Basalt - - 0 (0) 1198 (711) - -
Accelerator (50.5) (30.0) (1.2) - - - - -
Steel Fibers (263) (156) (6.2) 0.22 to 0.31 327 (194) 324 (192) 0.31 1446 (858)
Water (184) (109) (4.4) 0.18 to 0.20 271 (161) 238 (141) 0.208 303 (180)
Water-Binder Ratio - - 0.19 (0.19) 0.21 (0.21) - -
* Teichmann et al. 2002 considered two design mix and subdivided ground quartz into two groups, ** HRWRA = High Range Water
Reducing Admixture

14
2.2.1.1.2 Composition of UHPC
The characteristics strength of concrete is highly affected by their mix design and mixing of their
constituent such as cements, aggregates and additives. UHPC shows exceptional durability and
strength due to its optimized selection, proportioning and mixing of constituent materials. UHPC
constituent are optimized to produce the minimum void ratio. The largest granular material is fine
sand having size ranging from 15 µm to 600 µm. The main characteristic component of UHPC are
silica fume and quartz flour which have the smallest particle size of 1 µm and 10 µm, respectively.
Silica fumes and quartz flour are mainly responsible for enhancing UHPC mechanical and
durability properties when compared to other types of concrete by filling small interstitial spaces
or voids as showed in the Figure 2.2.1. Silica fume is a pozzolanic material which produces
additional binder material called calcium silica hydrate upon reacting with calcium hydroxide.
Calcium silica hydrate increases cohesion properties of fresh concrete as well as decreases
segregation and bleeding of fresh concrete (Nishikawa and Morita 2006). UHPC consists of finely
graded homogenous concrete matrix composed of fine sand having largest particle size range
between 150 µm and 600 µm, cement particle with average diameter of 15 µm, crushed quartz
with an average diameter of 10 µm and silica fume having the smallest size of 1 µm which fill up
the voids/interstitial spaces. 0.5 in long dispersed steel fibers present in UHPC acts as 3
dimensional reinforcements and helps in enhancing ductile properties of concrete by increasing
residual tensile strength.
Figure 2.2.1 Optimized model of UHPC in comparison with conventional concrete (Nishikawa
and Morita 2006)
Conventional Concrete UHPC

15
2.2.1.1.3 Fiber Reinforcement
Four different kinds of fiber reinforcement are widely used in UHPC and they are straight steel
fibers, deformed steel fibers, high modulus polyvinyl alcohol (PVA) and polypropylene. Ju et al.
(2009) conducted an experimental pullout test to study the effect of variation of steel fibers by
volume on its bond strength with concrete matrix. Based on polynomial regression test, it was
concluded that a maximum bond performance was achieved at 15% of fiber volume. But usually,
2% by volume of steel fibers are usually added to the matrix (Richard and Cheyrezy 1995). Typical
steel fibers have a diameter of 0.008 in. and a length of 0.5 in., covered with brass coating (Richard
and Cheyrezy 1995; Lafarge 2013). Due to the addition of fibers to concrete, it has been proved
that ductility of the concrete members increases (Rossi 2001). The ability of fibers to bridge
individual cracks enhances structural element ductility. Unlike conventional concrete, the stress
required to widen cracks depends upon tensile strength of fibers bridging cracks, concrete tensile
stress and the stress required for fibers to pullout (Mindess et al. 2003; Shaheen and Shrive 2007).
Also according to Richard et al. (1995), addition of fibers leads to increase in compressive strength
as compared to unreinforced UHPC material by stabilizing compressive stresses by means of
internal confinement. Al-Azzawi (2011) confirmed that an increase of 1% fiber volume, leads to
an increase of compressive strength by 5%.
2.2.1.1.4 Mixing of UHPC
Mixing of UHPC is more complicated than that of conventional concrete because UHPC
constituents have to be added in a specific order within time interval. Figure 2.2.2 illustrates the
sequence for the addition of various types of constituents of UHPC with their limiting time frame
of mixing. The procedure of mixing UHPC covered in the present research investigation was
adopted from Graybeal (2006). All components of UHPC are weighted in advance and half of the
High Range Water Reducer (HRWR) or superplasticizer with water is added to premix within 2
minutes. After 1 min, remaining 50% of the superplasticizer is added to mix within 30 second.
After 1 minute, accelerator is added to the mix within a time frame of 1 minute. UHPC is mixed
continuously until the mix turned into a thick paste and once thick paste is achieved. Steel fibers
are added to the mix within a minute and mixing continued until fibers well spread in the mix.
Fibers are usually added at the time when the entire mix seems to be workable.

16
Figure 2.2.2 Typical sequence of mixing of UHPC (Graybeal 2006)
2.2.1.1.5 Placement of UHPC
Kim et al. (2008) conducted several studies using the photographic techniques and the four point
bending test for evaluating the effect of placement of UHPC and the direction of flow on fiber
orientation, dispersion and on its tensile behavior. Their studies showed that the way of placement
of UHPC and direction of flow produces a significant difference of about 50% in developing
UHPC maximum tensile strength. Favorable properties are only obtained when the flow of UHPC
is oriented parallel to the direction of the principal tensile stresses. Further, UHPC does not
consolidate considerably when it flows horizontally by itself during its placement (JSCE 2004;
Nachuk 2008), disturbing the continuity of fiber alignment along the direction of flow at the
intersection as showed in Figure 2.2.3. Nachuk (2008) conducted an experimental investigation on
the effect of vertical placement of UHPC on their strength and concluded that there was no
noticeable decrease on their strength. But, according to AFGC and Setra (2002) UHPC should not
be dropped from a height greater than 1.65 ft. (0.5 m) in order to prevent segregation of fibers from
the matrix. Also in order to protect any formation of skinny thin dry layer on the surface, UHPC
should be poured continuously without any interruption. In exceptional cases, water misting and
All components of
UHPC are weighted
Ductal Premix
added to mixer and
mixed for 2 min
50% of
Superplasticizer
with water added to
premix within 2 min
Remaining 50% of
Superplasticizer with
water added to premix
within 30 Sec
Accelerator are
addded to mix
within 1 min
Steel fibers are
added to mix within
1 min
UHPC

17
agitation through external vibration were recommended when a fresh batch of UHPC was poured
over an older layer of UHPC. Different types of orientation of steel fibers in UHPC result in wide
variation in their strength. Depending upon the orientation of steel fiber, there are two possible
ways of UHPC placement. The first way of placing UHPC is to flow from one end of a form to
the other end (Graybeal 2009) as showed in Figure 2.2.4 (a). This is the most preferred way of
placing UHPC for flexural member because fiber align along the flow path making it more efficient
in bridging flexural cracks. Also, aligns the steel fibers along the principal axis for tensile stresses
at the bottom of the section as showed in Figure 2.2.5. While Figure 2.2.4 (b) shows the second
way of placing UHPC where UHPC is placed transversely to the longitudinal direction of
specimen.
Figure 2.2.3 Formation of joint due to un-proper mixing and flow of UHPC (Alessandro 2013)
Figure 2.2.4 Two ways of UHPC placement (Courtesy: Kim et al. 2008)
Figure 2.2.5 Proper alignment of fibers to restrict cracks in flexural members (D’Alessandro,
2013)
(A
)
(B
)
Placement of UHPC from one end
to the other end of the form
Placement of UHPC transversely to
longitudinal direction of member

18
2.2.1.1.6 Curing of UHPC
After the completion of UHPC placement, curing of UHPC is carried out by covering with a plastic
sheet to prevent loss of moisture through evaporation. Generally, UHPC takes longer initial time
to set as compared to conventional concrete and therefore formwork are removed after certain
specific time depending upon the desired gain of concrete strength. Properties of UHPC are highly
influenced by their method of curing. In order to obtain a higher strength, UHPC is cured with
steamed under controlled temperature and humidity. Ductal is treated under 95% of relative
humidity with a controlled temperature of 194ºF continuously for 48 hours (Graybeal 2006) which
includes 2 hours of increasing temperature and steam, 44 hours of constant temperature and
relative humidity and last two hours of decreasing temperature and steam.
2.2.1.1.7 Material Properties of UHPC
UHPC possesses a superior compressive strength which ranges between 20 to 80 ksi (Graybeal
2006; Lafarge 2013; Richard and Cheyrezy 1995). Graybeal (2006) conducted an experimental
test to study the effect of concrete specimen dimensions on the compressive strength of UHPC. It
was observed that the compressive strength of 2 in. cubic sample of UHPC gives higher
compressive strength than 2in. diameter 4 in. long UHPC cylinder. Tensile strength of UHPC is
usually above 1.45 ksi (Chanvillard and Rigaud 2003), which is considerably higher than those of
conventional concrete. Graybeal (2006) conducted an experimental test to obtain the tensile
strength of UHPC specimen through split tensile strength of cylinders, flexural testing of prism,
direct tension test of notched and un-notched cylinders, and uniaxial tension of briquettes. Table
2.2.2 shows results concluded by Graybeal (2006).
Table 2.2.2 Tensile strength of UHPC according to various test (Graybeal 2006)
Method of Test Tensile Strength (ksi)
First crack split tension test on cylinders 1.58
Ultimate split tension test on cylinders 3.51
First crack flexural test on prism 1.43
Direct tension test on notched cylinders 1.6
Direct tension test on un-notched cylinders 1.43
Uniaxial tension of briquettes 1.22

19
Since modulus of elasticity of any concrete depends upon its compressive strength, UHPC shows
a higher modulus of elasticity as compared to conventional concrete. ACI 318-11 gives the
following equation to calculate elastic modulus (EC) of normal concrete having compressive
strength Cf ′ (psi):
)(57000 psifE CC
′= Equation 2.2.1
The above equation is only applicable for concrete having compressive strength less than 6000 psi
and hence it’s not applicable UHPC. Since the equation given by ACI 318-11 was not appropriate
for concrete above 6000 psi compressive strength, American code ACI 363R-92 proposed another
equation to evaluate modulus of elasticity of concrete having compressive strength in the range of
3000 psi to 12000 psi as given below:
1000000)(40000 +′= psifE CC Equation 2.2.2
For predicting modulus of elasticity of high strength concrete, Ma et al. (2004) also proposed an
equation as given below:
3 )(525000 psifE CC
′= Equation 2.2.3
Both of the above equation 2.2.2 and 2.2.3 predicts modulus of elasticity of UHPC with an
accuracy level of 95.7% and 88.1% to that of the experimental test data of ductal conducted by
Graybeal (2007). UHPC in comparison with HSC possesses a very high compressive and tensile
strength with superior durability. This property of UHPC is attributed due to its very low water-
to-cement ratio and its densely packed characteristic mix design without coarse aggregates. The
presence of randomly distributed steel fibers between 2 to 12% (by volume) serves as 3
dimensional reinforcements at micro-level and also helps to increase its mechanical characteristics
(Almansour and Lounis, 2009).
2.2.1.1.8 Corrosion of steel fibers in UHPC
Oxidation of steel fibers located on the outer surface of the concrete may show some rust stain but
are not structurally considerable. Experimental investigation conducted by Voo (2006) showed
that the corrosion of steel fibers in an aggressive environment did not allowed rusting of steel fibers

20
beyond a depth of 2 mm from the outer surface of the concrete, because UHPC matrix is at least
20 times more impermeable than conventional concrete which restricts the deeper infiltration of
oxygen, moisture and chloride ions. Thus, rusting of steel fibers stops at the top surface and does
not spread deeper into the concrete. However, steel fibers expand by 30% of its original volume
due to rusting, but due to the smaller size of the steel fibers, this increase in the volume of the steel
fibers is not adequate to produce substantial internal stress to cause spalling of UHPC. Hence, at
serviceability conditions, the possibility of rusting of the internal steel fibers is insignificant (Voo,
2006).
2.2.1.1.9 Cost of UHPC Production
Although UHPC possess higher compressive and tensile capacity, it has been used in a very limited
application. The United States has only very few large-scale UHPC bridge girders. The governing
factor which overshadows the extensive use of UHPC is its high cost and limited available research
data. The cost of UHPC is almost ten times more than the cost of conventional concrete per unit
volume (Homeland Security Science and Technology 2010). The principal governing factors for
the cost of UHPC is its high cost of production and quality control, lack of industry knowledge,
undeveloped standards and design codes which preclude its extensive usages in more common
engineering applications. In order to increase the mass production and cost effective use of the
material, performance based design and optimization of UHPC structural members are highly
essential and demands further research such as; (a) Elimination of shear reinforcement to attain
maximum flexural capacity; (b) optimization of section; (c) Different types of fiber orientation
affecting strength; (c) applicability of existing traditional concrete models for cracking and post-
cracking behavior of UHPC; (d) applicability and accuracy of existing methods of predicting shear
and flexural resistance of UHPC.
2.2.2 Reinforcement
Since concrete is weak in tension, reinforcements are provided to resist the tensile stresses to avoid
cracking as discussed earlier. Basically, a concrete structure can be reinforced by either continuous
or discontinuous types of reinforcement. Since the section 2.2.1.1.3 explained steel fibers
(discontinuous) reinforcement types in detail, the present section discusses only longitudinal
(continuous) reinforcement type. And, the most popular and traditional material for longitudinal

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