Transfer Length in Bulb-Tee Girders Constructed with 
Self-Consolidating Concrete 
 
by 
 
Emily Louise Dunham 
 
 
 
 
A thesis submitted to the Graduate Faculty of 
Auburn University 
in partial fulfillment of the 
requirements for the Degree of 
Master of Science 
 
Auburn, Alabama 
August 6, 2011 
 
 
 
 
Keywords: anchorage, bond, debonding, prestressed concrete, prestressing steel 
 
 
Copyright 2011 by Emily Louise Dunham 
 
 
Approved by 
 
Robert W. Barnes, Chair, James J. Mallett Associate Professor of Civil Engineering 
Anton K. Schindler, Associate Professor of Civil Engineering 
James S. Davidson, Associate Professor of Civil Engineering 
 
ii 
 
Abstract
 
This thesis is focused on the transfer bond behavior of self-consolidating concrete 
(SCC) relative to conventionally vibrated concrete (CVC) in full-scale, plant-cast, 
prestressed concrete bulb-tee girders of implementation in Alabama bridges.  The study 
involved twelve girders: six BT-54 girders?three SCC and three CVC?and six BT-72 
girders?three SCC and three CVC.  All of the concrete used in the study was considered 
high-strength with values of approximately 8,300 psi at the time of prestress transfer.  
Unlike the previous phases, for the first time, this study also considered partially 
debonded strands and their performance in SCC.  Two different standard strand diameters 
were investigated. 
It was found that the results from the girders cast with SCC produced longer 
transfer lengths than those cast with CVC.  The larger cross-sections and less violent 
methods of prestress release resulted in shorter transfer lengths.  Transfer lengths grew 
over time. 
Transfer length expressions given by both ACI and AASHTO standards greatly 
overestimated the transfer lengths in comparison to the measured values.  In general the 
predicted values were roughly twice those measured in the study primarily because of the 
high-strength concretes used.  In addition, the expressions did not take into account 
several of the parameters that can have a significant effect on the transfer length, 
particularly concrete strength.  Consequently, an expression proposed by Levy (2007) 
iii 
 
produced the best overall representation of the trends seen in these girders and in prior 
related studies.
iv 
 
Acknowledgements 
 
I would like to thank Dr. Barnes for so many of his hours used in teaching, 
guiding, and sharing of his wisdom.  Not only did it have a tremendous effect on quality 
of this thesis, but he has also taught me invaluable things about being a structural 
engineer.  I would also like to thank Graduate Research Assistants Tom Hadzor, Brandon 
Johnson, Brian Rhett, Sam Keske, Wes Bullock, and Morgan Ellis for the time and 
portions of their lives they dedicated in helping to produce the test specimens, as well as 
the reading and recording of countless data points.  Not only did their help make this 
project feasible, but it became an adventure. 
This project would also have been impossible without the generous funding from 
the Alabama Department of Transportation and the help from the men at the Hanson 
Prestress Plant in Pelham, Alabama.  Their patience to allow us to interrupt their work 
routines in order to teach us the fabrication process will be valuable for years to come. 
Many thanks are also due to my wonderful family: Mom and Dad in Texas, 
Christian, and my Auburn family as they encouraged and supported me throughout this 
process.  Finally, may all the praise and glory go to the Lord who makes all things 
possible and brought me to Auburn for such a time as this. 
v 
 
Table of Contents 
 
Abstract ............................................................................................................................... ii 
Acknowledgements ............................................................................................................ iv 
List of Tables ...................................................................................................................... x 
List of Figures ................................................................................................................... xii 
List of Abbreviations ....................................................................................................... xvi 
Chapter 1 Introduction ........................................................................................................ 1 
1.1 Background ............................................................................................................. 1 
1.2 Research Objectives ................................................................................................ 3 
1.3 Research Scope ....................................................................................................... 4 
1.4 Organization of Thesis ............................................................................................ 4 
1.5 Notation................................................................................................................... 5 
Chapter 2 Review of Transfer Bond Behavior and Self-Consolidating Concrete in 
Precast/Prestressed Concrete Members ............................................................. 7 
2.1 Introduction ............................................................................................................. 7 
2.2 Definitions............................................................................................................... 8 
2.2.1 Transfer Length .............................................................................................. 8 
2.2.2 Flexural Bond Length .................................................................................... 8 
2.2.3 Development Length ...................................................................................... 9 
2.2.4 Debonded Strands ........................................................................................ 10 
vi 
 
2.2.5 Self-Consolidating Concrete ........................................................................ 12 
2.3 Code Provisions for Anchorage of Fully Bonded Strands .................................... 13 
2.3.1 ACI 318-08 .................................................................................................. 13 
2.3.2 AASHTO ..................................................................................................... 15 
2.3.3 Background of Anchorage Equations for Fully Bonded Strands................. 16 
2.3.4 Recent Research on Transfer Bond in Prestress SCC .................................. 17 
2.3.4.1 Girgis and Tuan (2005) ....................................................................... 18 
2.3.4.2 Ozyildirim (2008) ............................................................................... 19 
2.3.4.3 Staton et al. (2009) .............................................................................. 19 
2.3.4.4 Ziehl et al. (2009) ................................................................................ 21 
2.3.4.5 Pozolo and Andrawes (2011) .............................................................. 21 
2.4 Code Provisions for Anchorage of Partially Debonded Strands ........................... 22 
2.4.1 Code Provisions ........................................................................................... 22 
2.4.2 Background of Transfer Length Equations for Partially-Debonded Strands 24 
2.4.3 Previous Studies Associated with Partially Debonded Strands ................... 25 
2.4.3.1 Russell and Burns (1993) .................................................................... 25 
2.4.3.2 Barnes, Burns, and Kreger (1999) ...................................................... 26 
2.5 Previous Research Associated with this Study ..................................................... 27 
2.5.1 Concentrically Prestressed Prisms (Swords 2005) ...................................... 28 
2.5.2 Eccentrically Prestressed T-Beams (Levy 2007) ......................................... 29 
2.5.3 Prestressed AASHTO Type I Girders (Boehm 2008) .................................. 30 
2.6 Transfer Bond Theory ........................................................................................... 31 
2.6.1 Bond Mechanisms ........................................................................................ 31 
vii 
 
2.6.1.1 Adhesion ............................................................................................. 32 
2.6.1.2 Friction ................................................................................................ 32 
2.6.1.3 Mechanical Resistance ........................................................................ 33 
2.6.2 Bond Factors ................................................................................................ 33 
2.6.2.1 Time-Dependent Effects ..................................................................... 34 
2.6.2.2 Member Cross-Section........................................................................ 34 
2.6.2.3 Concrete Strength................................................................................ 35 
2.6.2.4 Prestressing Strand .............................................................................. 36 
2.6.2.5 Method of Stress Transfer ................................................................... 37 
2.6.2.6 CVC versus SCC................................................................................. 37 
2.7 Summary ............................................................................................................... 38 
Chapter 3 Design and Construction of Experimental Specimens ..................................... 41 
3.1 Introduction ........................................................................................................... 41 
3.2 Specimen Identification ........................................................................................ 41 
3.3 Specimen Design .................................................................................................. 43 
3.3.1 Strand Arrangement ..................................................................................... 45 
3.3.2 Nonprestressed Reinforcement Arrangement .............................................. 52 
3.4 Material Properties ................................................................................................ 54 
3.4.1 Concrete ....................................................................................................... 55 
3.4.2 Prestressing Strand ....................................................................................... 59 
3.4.3 Nonprestressed Steel Reinforcement ........................................................... 60 
3.5 Specimen Fabrication............................................................................................ 61 
3.5.1 Casting Configuration of Precast, Prestressed Bridge Girders .................... 61 
viii 
 
3.5.2 Fabrication of Precast, Prestressed Bridge Girders ...................................... 63 
Chapter 4 Transfer Length Test Program ......................................................................... 79 
4.1 Introduction ........................................................................................................... 79 
4.2 Test Procedure ...................................................................................................... 79 
4.2.1 Cast-In-Place DEMEC Mounting System ................................................... 80 
4.2.2 Specimen Preparation .................................................................................. 82 
4.2.3 Concrete Surface Strain Measurement......................................................... 87 
4.3 Determination of Transfer Length ........................................................................ 90 
4.3.1 Construction of Surface Compressive Strain Profiles ................................. 91 
4.3.2 Determination of Average Maximum Strain: End Transfer Zones ............. 94 
4.3.3 Determination of Average Maximum Strain: Debonded-Strand Transfer 
Zones ......................................................................................................... 99 
4.3.4 Precision of Results.................................................................................... 101 
Chapter 5 Results and Discussion ................................................................................... 103 
5.1 Results and Discussions ...................................................................................... 103 
5.1.1 Transfer Length Results of Fully Bonded Strands ..................................... 103 
5.1.2 Transfer Length Results Partially Debonded Strands ................................ 106 
5.1.3 Effect of Time ............................................................................................ 106 
5.1.4 Effect of Debonding Strands ...................................................................... 110 
5.1.5 Effect of Placement Sequence and Beam Orientation ............................... 112 
5.1.6 Normalization of Results ........................................................................... 115 
5.1.7 Effect of Concrete Strength ....................................................................... 118 
5.1.8 Effect of Concrete Type?CVC versus SCC ............................................. 119 
ix 
 
5.1.9 Effect of Strand Size .................................................................................. 125 
5.1.10 Effect of Cross-Section Size .................................................................... 128 
5.2 Comparison of Test Data with Design Expressions ........................................... 132 
5.2.1 ACI 318-08, Section 12.9 .......................................................................... 133 
5.2.2 AASHTO Standard and ACI 318-08 Shear Provisions ............................. 135 
5.2.3 AASHTO LRFD ........................................................................................ 137 
5.2.4 Levy (2007) ................................................................................................ 139 
5.2.5 Summary of Code Comparisons ................................................................ 143 
Chapter 6 Summary and Conclusions ............................................................................. 145 
6.1 Summary ............................................................................................................. 145 
6.2 Conclusions ......................................................................................................... 147 
6.3 Recommendations for Future Study ................................................................... 150 
References ....................................................................................................................... 151 
Appendix A: Notation ..................................................................................................... 155 
Appendix B: Special Provision ....................................................................................... 156 
Appendix C: Moustafa/Logan Pullout Testing Procedure and Results .......................... 179 
Appendix D: Fully Bonded Compressive Strain Profiles ............................................... 188 
Appendix E: Debonded Strand Compressive Strain Profiles ......................................... 201 
 
x 
 
List of Tables 
 
Table 3-1: Summary of Concrete Mixtures ...................................................................... 56 
Table 3-2: Fresh Concrete Properties ............................................................................... 57 
Table 3-3: Hardened Concrete Properties ......................................................................... 58 
Table 3-4: Summary of Concrete Properties .................................................................... 59 
Table 5-1: Summary of Transfer Length Results and Properties for Fully Bonded Strands
............................................................................................................................. 105 
Table 5-2: Summary of Transfer Length Results and Properties for Debonded Strands 106 
Table 5-3: Time Effects on Transfer Length of Bulb-Tee Girders ................................. 108 
Table 5-4: Effect of Time on Transfer Lengths in SCC ................................................. 110 
Table 5-5: Comparison of Transfer Lengths of Fully Bonded and Debonded Strands .. 111 
Table 5-6: Comparison of Transfer Lengths Based Upon Placement Sequence ............ 113 
Table 5-7: Comparison of Transfer Lengths Based Upon Beam Orientation ................ 114 
Table 5-8: Comparison of SCC and Conventional Mixture Transfer Length Results .... 119 
Table 5-9: Comparison of SCC and Conventional Mixture Results of Fully Bonded 
Strands................................................................................................................. 120 
Table 5-10: Comparison of SCC and Conventional Mixture Results of Debonded Strands
............................................................................................................................. 121 
Table 5-11: Paired SCC and CVC Girder Ends and Comparisons with Respect to Girder 
Depth ................................................................................................................... 122 
xi 
 
Table 5-12: Paired SCC and CVC Girder Ends and Comparisons with Respect to 
Placement Sequence............................................................................................ 123 
Table 5-13: Paired SCC and CVC Girder Ends and Comparisons with Interior and 
Exterior Girder Ends ........................................................................................... 123 
Table 5-14: Comparison of Normalized ? Values .......................................................... 125 
Table 5-15: Transfer Lengths as a Function of Strand Diameter .................................... 126 
Table 5-16: Transfer Length ? Values as a Function of Strand Diameter ...................... 127 
Table 5-17: Transfer Lengths as a Function of Strand Diameter and Concrete Type .... 128 
Table 5-18: Summary of Normalized ? Values .............................................................. 130 
Table 5-19: Recommended Transfer Length Equations by Levy (2007) ....................... 140 
Table 5-20: Summary of Code Provision Comparison ................................................... 144 
xii 
 
List of Figures
 
Figure 1-1: Precast/Prestressed Concrete Bulb-Tee Bridge Girder .................................... 2 
Figure 2-1: Development of Steel Stress in a Pretensioned Member ............................... 10 
Figure 2-2: Draped Strands ............................................................................................... 11 
Figure 2-3: Debonded Strands .......................................................................................... 12 
Figure 2-4: Concentrically Prestressed Singe- and Double-Strand Cross Sections .......... 28 
Figure 2-5: Eccentrically Prestressed Concrete T-beam Cross Section ............................ 29 
Figure 2-6: Prestressed AASHTO Type I Girder Cross Section ...................................... 31 
Figure 2-7: Hoyer Effect ................................................................................................... 33 
Figure 3-1: Specimen Identification ................................................................................. 42 
Figure 3-2: Typical BT-54 Girder Cross Section ............................................................. 44 
Figure 3-3: Typical BT-72 Girder Cross Section ............................................................. 45 
Figure 3-4: Mild Steel and Strand Arrangement for BT-54 Girder at End of Span ......... 47 
Figure 3-5: Mild Steel and Strand Arrangement for BT-54 Girder at Midspan ............... 48 
Figure 3-6: Mild Steel and Strand Arrangement for BT-72 Girder at End of Span ......... 49 
Figure 3-7: Mild Steel and Strand Arrangement for BT-72 Girder at Midspan ............... 50 
Figure 3-8: Profile and Hold-Down of Draped Strands for BT-54 Girder ....................... 51 
Figure 3-9: Profile and Hold-Down of Draped Strands for BT-72 Girder ....................... 51 
Figure 3-10: Mild Steel Spacing in BT-54 Girders .......................................................... 53 
Figure 3-11: Mild Steel Spacing in BT-72 Girders .......................................................... 53 
xiii 
 
Figure 3-12: End of Span Steel Configuration ................................................................. 54 
Figure 3-13: Typical Surface Condition of Prestressing Strand ....................................... 60 
Figure 3-14: Casting Configuration of Three BT-54 Girders ........................................... 62 
Figure 3-15: Casting Configuration of Two BT-54 Girders ............................................. 62 
Figure 3-16: Casting Configuration of BT-72 Girders ..................................................... 62 
Figure 3-17: Plastic Sheathing on Debonded Strands....................................................... 64 
Figure 3-18: DEMEC System Tied into Steel Cage ......................................................... 65 
Figure 3-19: Formwork Being Put into Place ................................................................... 66 
Figure 3-20: Concrete Delivery Vehicle Placing Concrete .............................................. 67 
Figure 3-21: CVC Placement ............................................................................................ 68 
Figure 3-22: External Vibrator.......................................................................................... 69 
Figure 3-23: External Vibration Track ............................................................................. 69 
Figure 3-24: Internal Vibration of Concrete ..................................................................... 70 
Figure 3-25: Placement of Self-Consolidating Concrete .................................................. 71 
Figure 3-26: Concrete Surface Roughening ..................................................................... 72 
Figure 3-27: Curing Blankets and Placement of Weatherproof Tarp ............................... 73 
Figure 3-28: Removal of Side Forms................................................................................ 74 
Figure 3-29: Flame Cutting ............................................................................................... 75 
Figure 3-30: Flame Cutting Sequence for BT-54 Girders ................................................ 76 
Figure 3-31: Flame Cutting Sequence for BT-72 Girders ................................................ 76 
Figure 3-32: Transporting BT-54 Girder to the Storage Yard .......................................... 77 
Figure 3-33: Girder Support Conditions in Storage Yard ................................................. 78 
Figure 4-1: Assembled DEMEC Mounting System ......................................................... 81 
xiv 
 
Figure 4-2: Fully Assembled DEMEC Mounting System ................................................ 81 
Figure 4-3: DEMEC Screw ............................................................................................... 82 
Figure 4-4: Location of Areas Analyzed for Transfer Length, BT-54 and BT-72 ........... 83 
Figure 4-5: Final Location of DEMEC Bar Prior to Casting ............................................ 84 
Figure 4-6: Exposed DEMEC Strip Immediately After Form Removal .......................... 85 
Figure 4-7: Removal of Foam Adhesive ........................................................................... 85 
Figure 4-8: Removal of Metal DEMEC Bar ..................................................................... 86 
Figure 4-9: DEMEC Strip after Metal Bar Removed and DEMEC Points Started .......... 87 
Figure 4-10: Finalized DEMEC Target Installation ......................................................... 87 
Figure 4-11: DEMEC Strain Gauge and Reference Bar ................................................... 88 
Figure 4-12: Performing DEMEC Strain Measurement ................................................... 89 
Figure 4-13: Compressive Strain Profile .......................................................................... 90 
Figure 4-14: Assignment of Surface Compressive Strain Values .................................... 92 
Figure 4-15: Compressive Strain Profile for End Transfer Zone (Girder End 52-2S-A-F)
............................................................................................................................... 94 
Figure 4-16: 100% AMS of Concrete Surface Strains (Girder End 52-2S-A-F) .............. 95 
Figure 4-17: Transfer Lengths with 95% AMS for End Transfer Zone (Girder End 54-2S-
A-F) ....................................................................................................................... 97 
Figure 4-18: Creep and Shrinkage Data............................................................................ 99 
Figure 4-19: 100% AMS of Concrete Surface Strains for Debonded Strand (Girder End 
72-4S-A-D) ......................................................................................................... 100 
Figure 4-20: Transfer Lengths with 95% AMS for Debonded-Strand Transfer Zone 
(Girder End 72-4S-A-D) ..................................................................................... 101 
xv 
 
Figure 5-1: Effect of Time on Transfer Lengths ............................................................. 107 
Figure 5-2: Transfer Length as a Function of Tendon Prestress and Concrete Strength at 
Transfer of Fully Bonded Strands ....................................................................... 117 
Figure 5-3: Transfer Length as a Function of Tendon Prestress and Concrete Strength at 
Transfer of Debonded Strands ............................................................................ 118 
Figure 5-4: Effect of Cross-Section Size on Transfer Lengths ....................................... 130 
Figure 5-5: Normalized ? Values with Respect to Member Depth ................................ 131 
Figure 5-6: Comparison to ACI Expression for Fully Bonded Strands .......................... 134 
Figure 5-7: Comparison to ACI Expression for Debonded Strands ............................... 134 
Figure 5-8: Comparison to AASHTO Standard and ACI 318-08 Section 11.3.4 
Expression for Fully Bonded Strands ................................................................. 136 
Figure 5-9: Comparison to AASHTO Standard and ACI 318-08 Section 11.3.5 
Expression for Debonded Strands ....................................................................... 136 
Figure 5-10: Comparison to AASHTO LRFD Expression for Fully Bonded Strands ... 138 
Figure 5-11: Comparison to AASHTO LRFD Expression for Debonded Strands ......... 138 
Figure 5-12: Comparison to Levy Expression for Fully Bonded Strands ...................... 141 
Figure 5-13: Comparison to Levy Expression for Debonded Strands ............................ 142 
xvi 
 
List of Abbreviations 
 
AASHTO American Association of State Highway and Transportation Officials 
ACI American Concrete Institute 
ALDOT Alabama Department of Transportation 
AMS Average maximum strain 
BT-54 Bulb-tee girder 54 in. in height 
BT-72 Bulb-tee girder 72 in. in height 
DEMEC Demountable, mechanical (points and gauges) 
GGBF Ground-granulated blast-furnace (slag) 
HSC High-strength concrete 
HRWR High-range water reducing (admixture) 
NASP North American Strand Producers 
PCA Portland Cement Association 
SCC Self-consolidating concrete 
SCM  Supplementary cementing material 
VDOT  Virginia Department of Transportation 
VMA  Viscosity-modifying admixture 
VSI  Visual stability index 
1 
 
Chapter 1 Introduction 
1.1 Background
The precast/prestressed concrete industry is one that has grown rapidly in the past 
several decades, from playing its first major role in rebuilding after World War II to 
being one of the leading participants in the construction industry today.  This type of 
construction has show great durability, along with fairly easy construction, reduced 
construction time, and cost efficiency as a result of the repeatability that is the key to the 
industry?s nature.  Any number of members and shapes can be reliably cast in large 
quantities that can then be used on the construction site.  One of the most common shapes 
are girders, typically used in bridge design.  Figure 1-1 shows a typical bulb-tee bridge 
girder being moved from a prestressing bed to the storage yard.  As research continues to 
find new ways of improving this process, the industry becomes even more advanced.  
One new development in the precast industry is the use of self-consolidating concrete 
(SCC). 
2 
 
 
Figure 1-1: Precast/Prestressed Concrete Bulb-Tee Bridge Girder 
Originating in Japan in the 1980s, SCC was created to be more workable and 
more convenient when placing concrete while providing a more durable concrete 
(Okamura and Ouchi 1999).  Due to its fluid nature and the fact that it can deform under 
its own weight when wet, the concrete can flow into small areas and through 
reinforcement without the aid of vibration or other human interference.  This not only 
leads to easier placement of the concrete, but it reduces the amount of labor involved, as 
well as increasing the level of safety for the workers.  As a result, SCC is very attractive 
to the precast/prestressed concrete industry. 
However, as a newer product, many entities are wary of using SCC until a full 
understanding of its behavior and structural integrity is understood.  One particular area 
of concern is the interaction between the prestressing strand and the concrete, as this is a 
vital aspect of any precast/prestressed member.  Alleviation of this concern will speed 
widespread implementation of SCC. 
3 
 
In order to address some of these issues, the Alabama Department of 
Transportation (ALDOT) sponsored an investigation performed by the Auburn 
University Highway Research Center.  The study explored the use of SCC in 
precast/prestressed bridge girders by first looking at many different aspects of the issue at 
a small scale before applying the results to larger projects with increasingly narrow 
scopes until a thorough understanding of the topic was achieved.  As the last phase of the 
investigation, information found from earlier investigations was applied to the production 
of full-scale, bulb-tee bridge girders for actual bridge construction.  In this case, a bridge 
will be constructed on State Route 22 over Hillabee Creek in Tallapoosa County, 
Alabama, two spans of which will be supported by SCC girders.  The remaining two 
spans will be supported by conventionally vibrated concrete (CVC) girders. 
1.2 Research Objectives 
The focus of this thesis was on the prestress bond behavior of SCC girders 
relative to that of CVC girders as expressed in the transfer length of the prestressing 
strand.  This relationship was determined by monitoring the girders and assessing their 
performance, which was then compared to previous investigations as well as to 
requirements set forth by the American Association of State Highway and Transportation 
Officials (AASHTO). 
Five characteristics, previously not addressed in other studies, were included 
when establishing the defining aspects of the project.  First, the bulb-tee girder shape was 
used at is a very common shape used for bridge construction.  Second, a large cross 
section was examined as many test specimens and small full-size girders have been 
examined, but nothing as large as the BT-72 girders.  Third, the amount of prestressing in 
4 
 
the cross section was maximized as previous projects only included minimal prestressing 
in order for the specimen to be tested in a laboratory environment.  Also, the presence of 
debonded strands wanted to be examined.  Finally, the girders were to be produced using 
standard plant production methods with minimal research influence in order to mimic 
girders that would be created for the construction of any bridge. 
1.3 Research Scope 
Twelve of the twenty-eight bulb-tee girders cast for use within the bridge over 
Hillabee Creek were selected for evaluation.  The girders were PCI bulb-tee girders 54 in. 
tall (BT-54) and PCI bulb-tee girders 72 in. (BT-72) tall, which were 97 ft 2 in. and 134 
ft and 2 in. long, respectively.  Six of the girders, three of each size, were cast using SCC.  
The remaining six, which were also composed of three girders of each size, were cast 
with CVC.  After the girders were fabricated, transfer lengths were measured after release 
of the prestressing strand, as well as at 7 days and 28 days after release. 
1.4 Organization of Thesis 
The results of a literature review performed in relation to transfer length and SCC 
are summarized in Chapter 2.  The pertinent definitions and code provisions dictating the 
calculations used to predict the transfer lengths based upon ACI?s Building Code 
Requirements for Structural Concrete (ACI 318-08) and Commentary, AASHTO?s 
Standard Specifications for Highway Bridges (2002), and AASHTO?s LRFD Bridge 
Design Specifications (2010) are outlined.  Bond theory is also discussed in relation to 
transfer length, describing the mechanisms through which the strand anchorage is 
provided, along with various different factors that can influence the transfer length.  In 
5 
 
addition, results from previous studies looking at transfer lengths in both CVC and SCC 
are presented to support and further the knowledge base on this subject. 
Information that describes the specimens in this experimental study is outlined in 
Chapter 3.  Detailed descriptions of the girders are presented, including sizes, 
dimensions, and reinforcement configuration.  The material properties of the concretes, 
prestressing strand, and mild steel are given, along with information on the components 
and manufacturers of the products.  Finally, a detailed description is given of the process 
of girder production and preparation for testing. 
The transfer length testing program is detailed in Chapter 4.  An improved method 
for measuring the transfer length is explained in full detail, including how the materials 
were fabricated that were then used in testing, along with how the measurements were 
taken.  The method used to analyze the raw measurements and determine the transfer 
lengths is described.   
The outcomes of the study are described in Chapter 5.  Comparisons and 
conclusions are drawn from the results collected, and related to the three previous phases 
of research.  In addition, many of the factors influencing the transfer length described in 
Chapter 2 are addressed in light of the results found in the investigation. 
Finally, an overview of the study and the important and noteworthy results 
gathered from the research is given in Chapter 6. 
1.5 Notation 
AASHTO?s LRFD Bridge Design Specifications (2010) has become the 
governing specification used in association with precast/prestressed concrete bridge 
6 
 
girders.  Consequently, the notation used within the specification was also used in 
association with this thesis.  A description of the notation used is listed in Appendix A. 
 
7 
 
Chapter 2 Review of Transfer Bond Behavior and Self-Consolidating Concrete in 
Precast/Prestressed Concrete Members 
2.1 Introduction
Prestressed concrete members rely on adequate anchorage of the prestressing 
strand within the concrete.  If this anchorage fails, the integrity of the member will be 
compromised with the possibility of a catastrophic failure.  This loss of anchorage is 
likely to result in significantly reduced shear or flexural resistance.  Consequently, it is 
important to not only understand anchorage, but it is also necessary to understand its 
different aspects, the various factors than can affect the quality of the anchorage, and 
consequently, understand how to use this information to properly design and produce safe 
members. 
This chapter addresses anchorage of prestressing strand by means of bond.  First, 
definitions and descriptions are given for key terms used throughout the study.  The 
history and implications of current code provisions dictating aspects of strand anchorage 
are provided, as well as the presentation of different mechanisms and factors that could 
influence the quality of strand anchorage.  In addition, the findings of recent research 
regarding transfer bond in SCC are summarized. 
8 
 
2.2 Definitions 
In order to establish a basis of understanding, the following definitions are given 
based on current code provisions to describe key terms that are used throughout, and are 
essential to, this study. 
2.2.1 Transfer Length 
In order to produce an effectively prestressed member, the force applied to the 
prestressing strands prior to casting must be transferred to the concrete after it has 
hardened by releasing the strands, which is referred to as release or transfer.  The 
resulting stress in the prestressing strands after transfer, fpt, is less than the original 
jacking force due to losses from strand chuck seating, steel relaxation, and elastic 
shortening of the concrete. The entirety of the prestress force cannot be transferred to the 
concrete at the end surface of the member; it is transferred gradually over a finite distance 
of embedded strand.  The measurable distance from the end of the girder to the location 
at which the full effective prestress force is developed in the concrete is considered the 
transfer length, lt (ACI 318-08, Section R12.9).  The mechanisms by which the force is 
transferred through bond are discussed in Section 2.6. 
2.2.2 Flexural Bond Length 
As a prestressed member undergoes external loading, additional force must be 
transferred into the prestressing steel to counteract the forces being exerted upon the 
member.  The maximum steel stress that must be resisted to achieve the nominal flexural 
strength, Mn, is denoted fps. The flexural bond length, lfb, is the additional distance 
beyond the transfer length required for fps to be developed in the member (ACI 318-08, 
9 
 
Section R12.9).  Since external loading was not applied to the specimens in this thesis, 
flexural bond lengths were not examined. 
2.2.3 Development Length 
The development length, ld, is the total distance from the end of the beam to the 
location at which the design strength of the reinforcement, fps, is developed (ACI 318-08, 
Section 2.2).  In terms of prestressed members, this is the sum of the transfer length and 
the flexural bond length.  Figure 2-1graphically displays this quantity, along with transfer 
length and the flexural bond length.  It also charts the changes in the prestressing stresses 
as the strand becomes further embedded.  While development length is not investigated 
directly as part of this study, it is of importance because if the length of bonded tendon at 
a specific section is less than the development length, the member will never be able to 
achieve fps and the corresponding nominal flexural strength (Barnes, Burns, and Kreger 
1999). 
  
10 
 
 
 
 
 
 
 
 
 
Figure 2-1: Development of Steel Stress in a Pretensioned Member 
(Barnes, Burns, and Kreger 1999, from ACI 318R-99, Fig. R12.9) 
2.2.4 Debonded Strands 
To optimize a prestressed section, a large prestressing force is typically applied 
close to the bottom of the member.  When these strands are released, a resulting tensile 
force is created on the top side of the member and large compressive stresses are induced 
at the bottom of the member.  Near the middle of the member span, these stresses are 
counteracted by the self-weight of the girder.  However, at the ends of the member, the 
tensile or compressive stresses can be so large that the concrete in these regions may be 
compromised.  To prevent such an effect, some of the prestressing strand may be draped 
and anchored at a higher location towards the end of the beam while held at a lower 
location at the center of the beam, as seen in Figure 2-2.  Other times, strands are 
lt lfb 
ld
Distance From Free End of Strand 
11 
 
prevented from bonding to the concrete at the end of a beam, which is referred to as 
partial debonding, which can be seen in Figure 2-3.  To debond strands, plastic sheathing 
is placed around the strands for a prescribed distance from the end of the beam prior to 
casting, preventing a bond from being created between the strand and the concrete, 
resulting in reduced effective prestressing at the girder ends.  In many cases, both 
methods are implemented to adequately reduce the prestressing effects in the concrete in 
the end regions.  As the strand exits the sheathing and becomes bonded to the concrete, it 
too will exhibit transfer and flexural bond lengths, both of which are measureable 
quantities. 
 
Figure 2-2: Draped Strands 
 
Draped Strands 
12 
 
 
Figure 2-3: Debonded Strands 
2.2.5 Self-Consolidating Concrete 
Self-consolidating concrete (SCC) is a type of concrete that is defined as ?a 
highly flowable, yet stable concrete that can be spread readily into place and fill the 
formwork without any consolidation and without undergoing significant separation? (PCI 
2003).  In addition to this definition, Girgis and Tuan  (2005) list three characteristics that 
further describe SCC: ?flow ability (the ability to fill all spaces in formwork under its 
own weight), passing ability (ability to fill spaces around reinforcing bars and other 
reinforcement under its own weight), and resistance to segregation (composition 
remaining uniform throughout transportation and placement).?  In light of these 
characteristics, the advantages of using this type of concrete are that typically it is of a 
better quality and has an increased production rate over conventional concrete (Naito, 
Parent, and Brunn 2006).  This is achieved by the fact that the concrete can consolidate 
itself and does not require additional workers to vibrate the concrete, which also 
Plastic Sheathing over 
Debonded Strands 
13 
 
improves safety measures for the individuals working in concrete production facilities.  
However, there are also concerns about the performance of SCC, including concerns 
about the possibility of segregation, poor air-void system, shrinkage, and reduced bond 
strength between strands and concrete (Ozyildirim 2008).  Consequently, the transfer 
bond performance of this type of concrete in prestressed girders was of particular interest 
and was the main focus of this research study. 
2.3 Code Provisions for Anchorage of Fully Bonded Strands 
Different design codes specify different methods on how the various lengths 
associated with prestressing anchorage are calculated.  The following sections 
summarizes the current code provisions of ACI?s Building Code Requirements for 
Structural Concrete (ACI 318-08), AASHTO?s Standard Specifications for Highway 
Bridges (2002), and AASHTO?s LRFD Bridge Design Specifications (2010). 
2.3.1 ACI 318-08 
ACI?s Building Code Requirements for Structural Concrete (ACI 318-08) directly 
address the development of prestressing strand in Section 12.9 of the code.  As part of 
this section, the development length equation is given as: 
 g1864g3031 g3404g4672 g3033g3291g3280g2871g2868g2868g2868g4673g1856g3029 g3397g4672g3033g3291g3294g2879g3033g3291g3280g2869g2868g2868g2868 g4673g1856g3029 Equation 2-1 
Where: fpe is the effective stress in the prestressing steel in psi, 
 fps is the stress in the steel which produces the nominal moment in psi, and 
 db is the strand diameter in inches. 
14 
 
The commentary for Section 12.9.1 goes on to explain that Equation 2-1 is made 
up of two components: the first term, which represents the transfer length, and the second 
term, which may be used to determine the flexural bond length.  Consequently, the 
equation for the transfer length of any prestressed member is described as: 
 g1864g3047 g3404g4672 g3033g3291g3280g2871g2868g2868g2868g4673g1856g3029  Equation 2-2 
Commentary in Section R12.9 indicates that there are external factors which 
could produce shorter transfer lengths.  These include strands with slightly rusted 
surfaces (as opposed to bright strands) and using a gentle release method.  The effects of 
these and other factors are further addressed in Section 2.5. 
However, Section 12.9 is not the only provision in ACI 318-08 which addresses 
the calculation of transfer length.  In Section 11.3.4 and 11.3.5, provisions dealing with 
the shear strength of a member based upon the concrete in prestressed members, it states 
that the transfer length shall be assumed as the following for prestressing strand: 
 g1864g3047 g3404uni0035uni0030g1856g3029 Equation 2-3 
where again, db is the diameter of the strand in inches.  Thus, the simplified form of 
Equation 2-3 gives a value equal to the transfer length of Equation 2-2 when fpe is 
equivalent to 150 ksi.  As this may be a low assumption of the effective stress given 
today?s practices, it could result in a shorter transfer length estimation, which, when used 
to calculate the nominal shear capacity in the end region of a member, could result in an 
overestimation of the available strength. 
15 
 
2.3.2 AASHTO 
There are currently two different AASHTO code provisions in use for bridge 
design, the first being the Standard Specifications for Highway Bridges (2002) and the 
other the LRFD Bridge Design Specifications (2010).  While many institutions are 
moving towards the newer LRFD Specifications, there are still entities, including 
ALDOT, which still use the Standard Specifications whenever allowed.  As both codes 
are in use and address the topics of interest, the provisions of each are examined in the 
following section. 
Section 5.11.4 of the AASHTO LRFD Bridge Design Specifications (2010), 
entitled ?Development of Prestressing Strand,? details the requirements for transfer 
length.  It is stated that the stress in the strand at the end of the section can be considered 
zero, which then varies linearly to the end of the transfer length at which point the stress 
is equivalent to fpe.  This is the same definition as that given in Section 2.2.1 of this 
thesis.  It is then stated in Section 5.11.4. that 
 g1864g3047 g3404uni0036uni0030g1856g3029 Equation 2-4 
This simple expression agrees with Equation 2-2 when a value of fpe equal to 180 
ksi is assumed.  As fps is usually less than 180 ksi, this is a more conservative estimate of 
transfer length than the ACI 318-08 expressions. 
AASHTO?s Standard Specifications for Highway Bridges (2002) does not 
directly address transfer length as the LRFD Bridge Design Specifications does.  Instead, 
a similar clause to that of ACI 318-08 can be found amongst the shear provisions for 
prestressed concrete.  In Section 9.20.2.4, the Standard Specifications allow the following 
assumption to be made for the transfer length for sections using prestressing strand: 
16 
 
 g1864g3047 g3404uni0035uni0030g1856g3029 Equation 2-5 
As with Section 11.3.4-11.3.5 of ACI 318-08, this expression is given for use in 
calculating the nominal shear capacity of a girder.  Thus, the shorter predicted transfer 
length of Equation 2-5, is less conservative for strength design than that of Equation 2-2 
or Equation 2-4. 
2.3.3 Background of Anchorage Equations for Fully Bonded Strands 
As explained by Barnes, Burns, and Kreger (1999), the history of the 
development length equations presented above for both the ACI and AASHTO codes are 
based on the research and reports of Hanson and Kaar (1959) and Kaar, LaFraugh, and 
Mass (1963), which were done through the Portland Cement Association (PCA).  
Between the two studies, 83 pretensioned beams were examined and tested for 
performance in relation to strand size, embedment length, strand slip, strand surface 
condition, reinforcement percentage, time, transfer length, and concrete strength (Barnes, 
Burns, and Kreger 1999). 
Tabatabai and Dickson (1995) explored the history of development length 
equation and how it evolved from the research done by Hanson and Kaar (1959) and 
Kaar, LaFraugh, and Mass (1963), along with a study performed by the American 
Association of Railroads.  As part of the efforts of the ACI Prestressed Concrete 
Committee, Alan H. Mattock derived equations that represented the relationships for the 
transfer length, flexural bond length, and the development length based on the results of 
the PCA research.  The committee then took the relationship and modified it to create the 
expression published in the 1963 ACI 318 (Barnes, Burns, and Kreger 1999).  The 
expression for the development length (in ksi units) was: 
17 
 
 g1864g3031 g3404g4672g1858g3043g3046 g3398g2870g2871g1858g3043g3032g4673g1856g3029 Equation 2-6 
This is functionally equivalent to Equation 2-1 (in psi units), which has been 
altered only in terms of units and arrangement of terms since 1963.  The transfer length 
portion of Equation 2-6 was functional equivalent to Equation 2-2.  However, in the 
corresponding ACI 318R-63 commentary, it was stated that this value for transfer length 
was to be an average value rather than a conservative design value (Tabatabai and 
Dickson 1995).  Furthermore, Barnes, Burns, and Kreger (1999) compared the original 
PCA transfer length data to the resulting code expression (Equation 2-2), and found that 
Equation 2-2 underestimated the transfer length for approximately 90 percent of the 
specimens.  This shift from a mean value to an average underprediction was the result of 
using the effective long-term prestress after all losses (fpe) in the code equation rather 
than the effective prestress at transfer (used in the original analysis by Mattock). 
Tabatabai and Dickson (1995) go on to describe a clause found in a draft for the 
1963 ACI 318 which is thought to be the origin of Equation 2-3.  The clause allowed the 
transfer length to be taken as 50db for members containing ?steel with a clean surface, 
released gently to a stress of 150 ksi? (Bennett 1963), resulting in the shear design 
provisions found in ACI 318 Section 11.3.4 and 11.3.5. 
2.3.4 Recent Research on Transfer Bond in Prestress SCC 
While code provisions provide recommendations by which to predict the transfer 
length, a long train of research has been performed in this area.  The following sections 
examine previous studies that investigated the accuracy of these provisions with respect 
18 
 
to prestressed members cast with SCC.  Additional studies were summarized by Swords 
(2005), Levy (2007), and Boehm (2008). 
2.3.4.1 Girgis and Tuan (2005) 
From the University of Nebraska-Lincoln, Girgis and Tuan (2005) examined three 
projects which incorporated similar bulb-tee girder shapes: NU1100, NU900, NU1350, as 
well as similar concrete mixtures that included two SCC mixtures and a conventional 
mixture.  The conventional mixture was the same as the second SCC mixture, but did not 
contain any viscosity-modifying admixture (VMA) and contained a reduced amount of 
high-range water reducing (HRWR) admixture, both of which are used to achieve desired 
concrete properties for SCC.  The concrete strength at transfer for the three projects was 
6490 psi and 5980 psi for the two SCC mixtures and 6970 psi for the CVC mixture.  
The girders contained 0.6-inch, low-relaxation prestressing strand which was 
tested according to Moustafa pullout test specifications.  The average results were 
approximately the same as the Moustafa pullout test benchmark for SCC Mix 1 (43.4 k 
compared to the benchmark of 43.2 which was scaled up for 0.6 in. stand).  SCC Mix 2 
had a significantly higher pullout strength of 54.2 k, which was higher than the Moustafa 
benchmark.  The CVC had strand pullout strength of 48.0 k. 
Surface concrete strain measurements were taken with a demountable, mechanical 
(DEMEC) gauge for this study, with measurements being taken at 3, 7, 14, and 28 days 
after casting.  The 95% maximum strain method was employed to determine the transfer 
length, which is fully described in Chapter 5. 
After analysis, it was found that the recommendations made by ACI 318 and the 
AASHTO specifications in Equations 2-3, 2-4, and 2-5 were underestimations of the 
19 
 
transfer lengths found in the SCC.  The transfer length of Mix 1 was 36 inches, which 
barely adhered to the provisions of AASHTO LRFD of 60db , but 50db was an 
underestimation.  Mix 2 of SCC had a transfer length of 43 inches, a value that exceeded 
all recommendations.  It was found however, that the CVC mixture did adhere to the 
limitations.  Consequently, it was hypothesized that the presence of the VMA in the SCC 
adversely affected the transfer bond, creating longer transfer lengths. 
2.3.4.2 Ozyildirim (2008) 
At the request of the Virginia Department of Transportation (VDOT), the Virginia 
Transportation Research Council performed a study led by Ozyildirim (2008) on using 
SCC in bulb-tee bridge girders.  The bulb-tee shape was selected as it provided a more 
efficient design for use in long span bridges, as well as allowing for wider girder spacing 
than the AASHTO I-beam shapes.  As a result, the constructed bridge on Route 33 over 
the Pamunkey River in West Point, Virginia contained eight 45-inch bulb-tee girders cast 
with SCC in one span and an adjacent span constructed with CVC. 
Two identical girders were cast with SCC for use in testing, with 28-day concrete 
strengths of 8340 psi and 8800 psi.  No information was given about the concrete strength 
of the test girders at release or any results of pullout tests that may have been performed.  
The girders were 60 ft in length and contained draped strands.  The transfer lengths were 
determined and found to be less than the predicted values established from the code 
provisions. 
2.3.4.3 Staton et al. (2009) 
A study was performed at the University of Arkansas considering the effects of 
SCC in prestressed beams.  Consequently, twenty prestressed concrete beams with fully 
20 
 
bonded strands were cast using two different SCC mixtures and one conventional 
mixture, all of which were high-strength concretes.  The SCC mixtures had 28-day 
concrete strengths of 10,260 psi to 14,420 psi, and the conventional-slump concrete had 
strengths of 10,700 psi to 13,100 psi.  All of the strands were released when the concrete 
strength was 5900 psi to 9850 psi.  The beams had a 6.5 in. x 12 in. cross-section, were 
18 feet in length, and contained two 0.6 in. diameter, 270 ksi, low-relaxation, seven-wire 
strands.  The strand was tested in accordance to the North American Strand Producers 
(NASP) strand-bond test and found an average of 21 k was required to achieve an end 
slip of 0.100 inch. 
The beams were cast on site at the university using a laboratory mixer.  Given the 
size of the mixer, a single batch of concrete was made and placed before a second batch 
was made and the forms were filled, with no more than forty-five minutes passing 
between the final placement of the first batch and the initial placement of the second 
batch.  Consequently, it was necessary to use limited internal vibration in the SCC beams 
in order to remove the thin crust that formed during the time between the placement of 
the two batches. 
DEMEC strain gauges were used to determine the surface compressive strains, 
with measurements taken at 3, 5, 7, 14, and 28 days after release, which was done by 
gradual release to prevent damage to the ends of the beams that could result from a 
sudden method of release. 
At the conclusion of the study, it was found that the transfer lengths of the beams 
tested were approximately 60 percent of those predicted based upon the code provisions 
21 
 
provided by ACI 318-05 and AASHTO LRFD, indicating that the recommended 
expressions for transfer length were conservative for strength design. 
2.3.4.4 Ziehl et al. (2009) 
The University of South Carolina conducted a study with three AASHTO Type III 
prestressed girders which were 59 ft 2 in. in length and cast with lightweight SCC which 
had 28-day compressive strengths which ranged from 6826 psi to 9167 psi, and an 
average release strength of approximately 6000 psi.  Results of any pullout tests, if 
performed, were not given.  Among other aspects of the study, the three girders were 
tested with respect to their transfer lengths.  DEMEC points were used with both digital 
and analog strain gauges to collect the compressive surface strains of the concrete before 
and after transfer.  No long-term measurements were taken.  As with the other studies, the 
95% average maximum strain (AMS) was utilized to determine the transfer lengths. 
After interpreting the analysis results, it was found that even lightweight SCC 
adhered to the AASHTO LRFD provisions.  It was found that the transfer lengths were 
equivalent to 44db, which was less than 60db.  While the team realized that the three 
girders were a limited research sample, it still appeared that the code provisions were 
conservative for strength design. 
2.3.4.5 Pozolo and Andrawes (2011) 
At the University of Illinois at Urbana-Champaign, a different approach was taken 
to examining transfer lengths.  Pozolo and Andrawes (2011) performed an extensive 
overview of previous research projects performed with SCC and used finite element 
modeling to estimate the transfer lengths.  However, a single SCC box girder was cast to 
collect experimental results.  Bond quality was explored by performing fifty-six Moustafa 
22 
 
pullout tests in both SCC and CVC.  It was found that the difference between the first slip 
of the strands in the two types of concrete varied by 10 percent for all of the tests with 
first slip occurring at approximately 27 k.  In order to discount any affects due to the 
variation of concrete strength, all the results were normalized and specific concrete 
strengths were not reported.  As with the other studies, once the girder had been cast and 
the prestressing force was released, at which point the concrete strength was 
approximately 4000 psi, DEMEC gauges and points were used in conjunction with the 
95% AMS method to determine the transfer length.  As with the other studies, the ACI 
and AASHTO limitations on the extent of the transfer length encompassed the results, 
again proving the provisions to be conservative for strength design. 
2.4 Code Provisions for Anchorage of Partially Debonded Strands 
In many larger prestressed members, it is necessary to include partially debonded 
strands in the design.  The following sections summarize the code provisions of ACI?s 
Building Code Requirements for Structural Concrete (ACI 318-08), AASHTO?s Standard 
Specifications for Highway Bridges (2002), and AASHTO?s LRFD Bridge Design 
Specifications (2010) concerning anchorage of debonded strands. 
2.4.1 Code Provisions 
ACI?s Building Code Requirements for Structural Concrete (ACI 318-08) (2008) 
does mention adjustments in the equations pertaining to the lengths associated with the  
development of the prestressing strand that are to be made in the presence of debonded 
strands.  In section 12.9.3, it is stated that the development length, as shown in Equation 
2-1, shall be doubled in situations when the precompressed tensile zone goes into tension 
under service load conditions.  It thus follows that for members in which tension is never 
23 
 
developed under service loads, the development length need not be doubled.  In addition 
to this, the Commentary indicates that ?for the analysis of sections with debonded strands 
at locations where strand is not fully developed, it is usually assumed that both the 
transfer length and the development length are doubled? (ACI 318 2008). 
AASHTO LRFD Bridge Design Specifications (2010) also addresses the presence 
of partially debonded strands in Section 5.11.4.3 in situations in which the precompressed 
tensile zone is in tension when being subjected to service loads.  While this section 
addresses the allowable amount and location of the debonded strands, as well as the 
adjustments to be made to the development length equation in the presence of debonding, 
the transfer length once a debonded strand becomes bonded to the surrounding concrete 
is not addressed.  The only modification made to Equation 5.11.4.2-1 of Section 5.11.4.2 
of the code, which calculates the development length, is a modification factor of two.  
Since nothing is mentioned regarding the associated transfer length for debonded strands, 
it is unclear whether the transfer length should also be multiplied by the modification 
factor of two along with development length or if it remains the same as for fully bonded 
strands. 
Section 9.28.3 of the AASHTO Standard Specifications for Highway Bridges 
(2002) requires that the development length, based upon the development length equation 
specified in Section 9.28.1, be doubled.  As with the AASHTO LRFD and ACI codes, 
this is only for situations in which the member is subjected to tensile forces in the 
precompressed tensile zone under service loads and only in areas with debonded strands.  
However, as with the LRFD provisions, the AASHTO Standard Specifications gives no 
24 
 
guidance for how to address the transfer lengths within these zones.  The resulting 
implications for the transfer lengths of partially debonded strands are unclear. 
2.4.2 Background of Transfer Length Equations for Partially-Debonded Strands 
ACI 318-08 cites two investigations in the commentary as part of the background 
for the provisions of debonded strands.  In the first study, Kaar and Magura (1965) 
studied the behavior of five girders, three of which were subjected to static and dynamic 
loads until failure, and two girders which were subjected to shear loading until failure.  It 
was found that a girder with twice the development length for debonded strands 
performed the same as one with draped strands when subjected to flexural loads tested to 
failure.  At the same time, a girder with only a single development length developed fared 
significantly worse.  When tested for shear capacity, a girder with twice the development 
length again performed similarly to a girder with draped strands, resulting in the code 
provisions suggesting a development length of twice that of fully bonded strands. 
Rabbat et al. (1979) looked at the effect of fatigue loads on debonded strands in 
two different service load scenarios: the first, when the bottom fiber was stressed to zero 
tension, and the other when it was stressed touni0020uni0036g3493g1858g1314g3030 under service-load cycles.  It was 
found that in the cases in which tension was not developed at service loads, a single 
development length was adequate, but when tension was developed in the bottom fiber of 
the test specimens, twice the development length was needed.  It was after these finding 
were published that the 1983 code began to stipulate that the development length for 
debonded strands need only be doubled in cases in which the precompressed tensile zone 
would be in tension under the service loads. 
25 
 
2.4.3 Previous Studies Associated with Partially Debonded Strands 
While there has not been much research performed for debonded strands in SCC, 
previous researchers have investigated debonded strands and their performance in 
convention-slump concrete when compared with fully bonded strands.  This section looks 
at two of these studies. 
2.4.3.1 Russell and Burns (1993) 
Guidelines for debonding strands were available in the early 1990s but were based 
on engineering judgment rather than on experimentation.  Consequently, a study at the 
University of Texas was performed by Russell and Burns (1993) examining the benefits 
and feasibility of debonding strands as an alternative to draping strands.  Draped strands 
are created by stressing and then lowering the hold-down points, a process which has 
caused flawed strands to fail.  It has been seen that these are areas of weakness as hold-
down point apparatuses can fail and strands have snapped as a result of the higher forces.  
Not only do debonded strands not experience the additional stresses, but all that is 
required to construct them is to jacket the strands in a plastic sheathing, which is an easier 
and simpler procedure than draping the strands.  The goal of the study was to be able to 
provide guidelines for the use of partially debonded strands based upon experimental 
evidence. 
From the experimental results of the static tests performed on I-shaped beams, it 
was found that members with debonded strands were sensitive to cracking.  Slip occurred 
as cracks formed, due to flexure or web shear, within the transfer zones of the debonded 
strands.  It was found that beams containing staggered debonding, at which the debonded 
length varied from strand to strand, performed better than those with debonded lengths 
26 
 
that were uniform.  This was attributed to the fact that beams with concurrent debonding 
were more susceptible to cracking which then led to bond failures. 
The experimental measurements taken by Russell and Burns (1993) indicated 
problems within the code provisions.  It was determined that the provisions were too 
restrictive for debonded strands and in many cases were misleading in such a way that 
would permit unsafe designs.  As a result, recommendations were made to isolate the 
debonded strands to ensure they never experienced any cracking.  An expression was 
given which would limit the debonded length in simply supported members, and thus 
prevent cracking in these regions, and can be seen in Equation 2-7. 
 g3013g3277g2878g3013g3295g3020g3043g3028g3041 g3407g2869g2870g3436uni0031g3398g3495uni0031g3398g3014g3278g3293g3014
g3296
g3440 Equation 2-7 
Where: Lb is the debonded length in inches 
 Lt is the transfer length in inches 
 Mcr is the cracking moment in kip-inches 
 Mu is the ultimate moment in kip-inches 
Which can then be simplified for highway bridge girders and become: 
 g1838g3029 g3397g1838g3047 g3407uni0030uni002Euni0031uni0036g1499g1845g1868g1853g1866 Equation 2-8 
2.4.3.2 Barnes, Burns, and Kreger (1999) 
Barnes, Burns, and Kreger (1999) also performed a study at the University of 
Texas at Austin which examined the anchorage behavior of 0.6 in. strands arranged in a 2 
in. grid pattern within AASHTO Type I I-Beams.  As part of the investigation, several 
different debonded configurations were examined.  While it was determined that 
debonding was an effective method of reducing extreme concrete stresses after the 
27 
 
release of the prestressing strand, it was found that the transfer lengths of the debonded 
strands were no longer than comparable fully bonded strands. 
Special care has to be taken to ensure that the debonded strands are fully 
developed in flexural members.  As transfer zones with debonded strands are nearer the 
center of the beam than transfer zones of fully bonded strands, there is an increased risk 
that critical cross-sections are located within the transfer zone for the partially debonded 
strands.  If cracking occurs in these areas, the anchorage of the debonded strands can be 
compromised and the structural integrity of the beam can be impaired. 
In addition, Barnes, Burns, and Kreger (1999) recommended that in relation to 
development length of partially debonded strands, the prestressing strand behaved 
similarly to cutoff bars in reinforced concrete.  Consequently, debonded strands should 
also be subjected to the code provisions dictating the limitations on terminating 
nonprestressed reinforcement.  Meanwhile, another way to properly guarantee adequate 
anchorage of the debonded strands is to ensure cracking does not occur across the bonded 
length of strand within 20db of the transfer length.  Consideration of these ideas offers an 
alternative explanation for the anchorage failures of debonded strands experienced in the 
previous studies.  Further study was recommended to simplify the design provisions for 
anchorage of partially debonded strands. 
2.5 Previous Research Associated with this Study 
The research presented in this study is an extension of an earlier study examining 
the potential implementation of self-consolidating concrete in precast, prestressed bridge 
girders.  Consequently, the three earlier studies of transfer bond in Alabama SCC are 
outlined in the following sections. 
28 
 
2.5.1 Concentrically Prestressed Prisms (Swords 2005) 
Swords began the extended study by examining thirty-six concentrically 
prestressed concrete specimens.  The 10-foot long prisms were cast from five different 
concrete mixtures, which included one CVC mixture and four SCC mixtures.  The SCC 
mixtures included high-strength and low-strength mixtures using Class C fly ash as an 
admixture, and high-strength and low-strength mixtures utilizing ground-granulated 
blast-furnace (GGBF) slag.  Six prisms were cast using each mixture, three of which were 
prestressed with a single strand, and three which were prestressed with two strands 
spaced at 2 in. on center (Swords 2005).  The configurations of these prisms can be seen 
in Figure 2-4.  An additional set of six prisms were cast from high-strength SCC with fly 
ash admixture because the first set had an air content that exceeded ALDOT?s 
specifications for maximum allowable air content. 
 
 
Figure 2-4: Concentrically Prestressed Singe- and Double-Strand Cross Sections 
(Swords 2005) 
As a result of having thirty-six prisms, seventy-two transfer zones were 
considered as a transfer length was measured at each end of a prism.  The strands were 
flame cut, and mechanical strain gauges were used to measure the surface strains in the 
? in. Oversized Grade 
270 Low-Relaxation 
Seven-Wire Strand 
29 
 
concrete.  The strains were then analyzed to determine the transfer lengths.  Transfer 
lengths were determined at four different ages: immediately after transfer, 2?4 days after 
transfer, 7 days after transfer, and 28?46 days after transfer. 
2.5.2 Eccentrically Prestressed T-Beams (Levy 2007) 
Levy continued the study by testing sixteen T-beams with two ?-inch ?special? 
strands.  Four different concrete mixtures were utilized to cast the beams, one of which 
was CVC, and three were SCC mixtures.  The mixtures were the same as those used by 
Swords in 2005, with the exception that the high-strength SCC mixture with Class C fly 
ash was not used.  Four beams with varying lengths of 9 ft 8 in., 13 ft 0 in., 16 ft 4 in., 
and 23 ft 0 in. were cast from each concrete mixture.  The cross section utilized for the 
project was constant throughout and can be seen in Figure 2-5. 
 
Figure 2-5: Eccentrically Prestressed Concrete T-beam Cross Section  
(Levy 2007) 
30 
 
The prestressing strand was released by flame-cutting and was done in such a way 
that a live end and a dead end were created.  As a result, thirty-two transfer zones were 
created, each of which were determined from measured concrete surface strains.  
Measurements were taken immediately after transfer of the prestressing to the concrete 
and 4 days after transfer. 
2.5.3 Prestressed AASHTO Type I Girders (Boehm 2008) 
To ensure the results from the previous small-scale tests could be applied to full-
scale bridge girders, Boehm studied the behavior of six prestressed AASHTO Type I 
girders.  Three concrete mixtures were used to cast the 40-foot long girders, including 
one CVC mixture and two SCC mixtures.  Two girders were cast of each mixture: CVC, 
high-strength SCC utilizing GGBF slag, and moderate-strength SCC utilizing GGBF 
slag.  These were the same mixtures used by both Swords (2005) and Levy (2007).  SCC 
containing Class C fly ash was not used as part of the investigation.  A typical cross 
section of the girders observed can be seen in Figure 2-6. 
31 
 
 
Figure 2-6: Prestressed AASHTO Type I Girder Cross Section  
(Boehm 2008) 
Twelve transfer zones were created after flame-cutting the strands.  The surface 
strains were once again measured using a DEMEC gauge with measurements taken 
immediately after the transfer of the prestressing force to the concrete, as well as at 
intervals ranging from 3 days to 3 months. 
2.6 Transfer Bond Theory 
There are several issues that could be considered when examining the transfer 
length.  First, there are the mechanisms by which the bond is actually created between the 
strand and the concrete.  There are also many factors that can have an effect on the 
quality of the mechanisms.  The mechanisms and factors are discussed in this section. 
2.6.1 Bond Mechanisms 
In order for transfer lengths to be developed, stress from the prestressing strand 
has to be transfer into the concrete.  This is accomplished through transfer bond stress.  
(2) ?? ? Strands 
(6) ?? ? Strands #3 Confining bars 
(ends only) 
#4 or #5 Stirrups 
32 
 
Hanson and Kaar (1959) identified three mechanisms by which the prestressing strand 
becomes bonded to the concrete: adhesion, friction, and mechanical resistance. 
2.6.1.1 Adhesion 
Adhesion is the mechanism in which the concrete literally ?sticks? to the 
prestressing strand.  Not only is it a weak bond that is easily broken, but the strand almost 
always experiences some slip relative to the concrete near the end of the member, 
breaking the bond that had been developed.  Consequently, adhesion plays a minor role in 
the development of the transfer bond stress (Barnes, Grove, and Burns 2003). 
2.6.1.2 Friction 
As some slip does occur between the strand and the concrete, friction plays a 
much larger role than adhesion and is considered the primary mechanism in creating the 
transfer bond stress (Hanson and Kaar 1959).  This is achieved through the Hoyer Effect, 
which is illustrated in Figure 2-7.  This form of friction is a result of the Poisson Effect.  
As the prestressing strand is stretched, the strand diameter decreases creating a smaller 
strand.  With the steel held in this position, the concrete is cast around the strands and 
allowed to harden.  When the strand is released, it tries to expand back to its original 
shape, but it cannot expand without compressing the hardened concrete.  Consequently, 
radial compressive stresses result, which allow for stress transfer from the prestressing 
steel to the concrete through friction. 
33 
 
 
Figure 2-7: Hoyer Effect 
2.6.1.3 Mechanical Resistance 
A smooth wire is incapable of providing any mechanical resistance.  However, 
given the helical pattern of a seven-wire strand of prestressing, the strand can provide 
mechanical resistance via a bearing stress.  Once the concrete is hardened and strands 
released, the ridges of the strand can push against the grooves cast around the strand, 
allowing for the stress in the prestressing strand to be transferred to the concrete and 
prevent sliding (Levy 2007).  In the experiments done by Hanson and Kaar (1959), it was 
seen that members with the seven-wire strand were able to develop larger moments, even 
after general bond slip had occurred, than members that contained individual smooth 
strands. 
2.6.2 Bond Factors 
In addition to the mechanisms that create the bond, Hanson and Kaar (1959) 
identify several factors also affecting the quality of bond, and thus the transfer length.  
The main factors that contribute to this are the amount of prestress, surface condition of 
34 
 
the strand, strength of the concrete, and the method of stress transfer.  Yet it was also 
seen that the concrete strength, percentage of steel, and the embedment length are 
interrelated terms which must all be considered and taken into account during the design 
process.  These mechanisms and factors are described in the following sections. 
2.6.2.1 Time-Dependent Effects 
Barnes, Grove, and Burns (2003) report that studies dating back to 1951 have 
experienced effects relating to time.  Typically, the transfer lengths continue to grow for a 
few days after release, after which it continues to grow at a much slower rate, with 
measurements taken as many as thirty months after release.  Most of these affects can be 
attributed to the long-term properties of creep and shrinkage in the concrete and 
relaxation in the prestressing steel (Barnes, Grove, and Burns 2003).  As these factors 
continue to alter the state of the concrete, the interaction between the concrete and steel 
varies as well. 
Results presented by Staton et al. (2009) concluded that the time-dependent 
effects were more prominent in CVC rather than SCC, which was ?attributed to less time-
dependent softening of the concrete grip on the strands compared with the high-strength 
concrete (HSC) transfer-length growth? (Staton et al. 2009). 
2.6.2.2 Member Cross-Section 
Research performed by Levy (2007) and Boehm (2008), when compared to that 
done by Swords (2005), documented the effect of cross-sectional size on the transfer 
length.  It was found that as the cross-section increased, the transfer length decreased.  
Levy fabricated T-beams which were 24 in. in width and 15 in. in height which were then 
compared to Swords? 6 in. x 4 in. prisms.  When the transfer lengths were compared, 
35 
 
Levy?s transfer lengths were 36 percent smaller than those recorded by Swords (2005).  
Consequently, Boehm (2008) compared the results collected from the transfer lengths of 
AASHTO Type I girders to Levy?s results, finding that the transfer lengths were 31 
percent shorter than the T-beams and 56 percent shorter than the prisms. 
2.6.2.3 Concrete Strength 
As the strand initially bears on the concrete, an inelastic response is created and 
cracking occurs in the concrete in the local region directly around the strand.  The amount 
and extent of this effect is dictated by the tensile capacity and the stiffness of the 
concrete.  Both the stiffness and tensile capacity of the concrete can be approximated as 
being proportional to the square root of the concrete compressive strength.  Based upon 
this theory and experimental results, Mitchell et al. (1993) suggested that the transfer 
length should be inversely proportional to the square root of the compressive strength 
(Barnes, Grove, and Burns 2003). 
Many experimental transfer length testing programs performed over the last fifty 
years, including Hanson and Kaar (1959) and Barnes, Burns, and Kreger (1999), found 
correlations between concrete strength and the transfer length.  However, a newer study 
conducted by Staton et al. (2009) using SCC indicated that there was not a correlation 
between the concrete strength and the transfer length.  Unlike the other studies examined, 
the study performed by Staton et al. (2009) did not vary the concrete strengths based on 
variations in the concrete mixtures, but rather releasing the prestressing strand at varying 
concrete strengths given how long it had been since casting.  This method of varying the 
concrete strength has much less effect on the transfer length than variation of 28-day 
concrete strength (i.e. variation of the mixture proportions).  Consequently, the study 
36 
 
does not provide enough evidence to conclude that the concrete strength does not affect 
transfer lengths, especially as studies performed on SCC and CVC by Swords (2005), 
Levy (2007), and Boehm (2008) indicate that there is a direct correlation over a wide 
range of concrete strengths. 
2.6.2.4 Prestressing Strand 
As can be seen strictly from Equations 2-3, 2-4, and 2-5, an important factor is the 
strand diameter, as this is the only variable included in all of these equations.  This is a 
result of the fact that as the diameter changes, so does the amount of surface area that can 
come into contact with the concrete.  On the other hand, because the cross-sectional area 
of the strand increases with the square of the diameter, the amount of force that must be 
transferred over this surface area outpaces the increase in surface area.  As a result?for 
the same level of prestress?the transfer length increases with the diameter. 
Evidence has also presented itself that the quality of the strand surface condition 
can also have an effect on the transfer length.  The theory accredits weathered strands as 
having more frictional resistance than strand that is pristine, thus reducing the transfer 
length.  However, as described by Martin and Scott (1976), it is considered impractical to 
incorporate the added advantage of weathered strand as it is not a feature that can be 
manufactured, nor is there a way to dictate the length of exposure required to achieve the 
proper amount of weathering (Barnes, Grove, and Burns 2003).  Furthermore, although 
Barnes, Burns, and Kreger (1999) observed that weathered strands had a shorter average 
transfer length than nonweathered strands, several specimens with weathered strands 
exhibited longer transfer lengths than the control specimens.  Thus, the dispersion of the 
results with weathered strands was too large to result in a reliable design advantage. 
37 
 
2.6.2.5 Method of Stress Transfer 
There are generally two categories of prestress transfer methods: sudden release 
and gradual release.  As the name indicates, sudden release typically involves the cutting 
of the strand.  A gradual release can be accomplished by moving the block in which the 
strands are anchored allowing the strand to relax slowly, or a sudden release may be 
performed at one location prior to releasing any of the other strands.  By doing this, the 
remaining ends would then be considered a gradual release as the majority of the stress 
has already been released.  Numerous studies have shown that transfer lengths associated 
with sudden release methods result in longer transfer lengths, which is credited to the 
?dynamic effect associated with the transfer of energy from the strand to the concrete 
member? (Barnes, Grove, and Burns 2003). 
Staton et al. (2009) reported a lack of correlation between the live-end and dead-
end transfer lengths recorded.  However, this is due to the fact that a gradual release 
method was employed. 
2.6.2.6 CVC versus SCC 
Limited information is currently available for the bond performance of SCC, as 
this type of concrete is still relatively new and has yet to gain widespread acceptance.  
However, there has been a push to move towards this type of concrete and, as a result, 
more studies have been performed examining the properties. 
Swords (2005), Levy (2007), and Boehm (2008) each found the transfer lengths in 
girders cast with SCC to be longer that those found in girders cast with CVC.  When 
looking at values obtained from girders cast with concrete with less than 30 percent 
GGBF slag, it was found that the transfer lengths in the SCC were 28 percent, 4 percent, 
38 
 
and 7 percent longer than the transfer lengths in CVC for each of the studies, 
respectively. 
Staton et al. (2009) reported minimal differences in transfer lengths between the 
first type of SCC cast and the HSC.  While it appeared that the transfer lengths in SCC 
girders were slightly shorter, a statistical analysis showed that the transfer lengths for the 
two concrete types were the same.  For the second type of SCC, transfer lengths were 
found to be statistically shorter than HSC. 
A study at Lehigh University by Naito, Parent, and Brunn (2006) examined the 
use of SCC in bulb-tee girders.  Two concrete mixtures were utilized, one being SCC and 
the other CVC, with each mixture being cast into two 45 in. tall bulb-tee girders, which 
resulted in four girders 35 ft in length.  Analysis of the girders found that the difference 
between the transfer length in the SCC was 0.1 inches shorter than that of CVC, again 
indicating that SCC and CVC are interchangeable. 
Results found by Ozyildirim (2008) also indicated that the same methods used for 
the design of girders with CVC can also be used for the design of girders cast with SCC. 
Finally, Ziehl et al. (2009) found that in lightweight SCC, the transfer lengths 
associated with the SCC were 15 percent greater than those found for the corresponding 
high-strength lightweight concrete. 
2.7 Summary 
There are many aspects of transfer lengths that must be considered when 
performing any type of analysis or study.  Of the two major organizations that 
recommend methods of predicting transfer lengths for design, three different approaches 
are supplied, two of which rely strictly on the diameter of the strand being used, and one 
39 
 
which also takes into account the stress in the strand.  However, it is known that there are 
many other factors that can affect the transfer lengths in SCC.  Even so, all results except 
for one situation indicated that the current code provisions provided a safe estimate of the 
transfer length, even though in many cases it was a significant overestimation. 
ACI and AASHTO also address the presence of debonded strands, but only 
briefly, and not with respect to transfer length.  Due to the lack of any additional 
information, it may be assumed that the transfer length of a debonded strand?measured 
from the end of the debonded length?is the same as that of a fully bonded strand at the 
end of a member when not under service loads that create tension in the precompressed 
tensile zone. 
It was also seen that there were three different mechanisms through which the 
stress in the strand can be transferred to the concrete.  The most effective mechanism was 
friction, which manifested its self through the Hoyer Effect.  Through these mechanisms, 
there were also several factors that played a role in the effectiveness of the mechanisms 
which included time-dependent issues, member cross section, concrete strength, 
properties and characteristics of the prestressing strand, method of prestress transfer, and 
type of concrete (CVC of SCC).  Of these, it was determined that the concrete strength, 
prestressing strand diameter, and method of prestress transfer had the largest impact on 
the transfer lengths. 
From recent research it was also seen that even though the transfer lengths in SCC 
were sometimes found to be longer than those in CVC, they still generally adhered to the 
guidelines set forth by the design codes.  However, it was still of interest to further 
40 
 
explore the effects of SCC in large, full-scale girders in comparison to the test specimens 
previously examined, as well as the behavior of the transfer lengths of debonded strands.
41 
 
Chapter 3 Design and Construction of Experimental Specimens 
3.1 Introduction
While casting the girders in the fall of 2010 for the four-span bridge on State 
Route 22 over Hillabee Creek in Tallapoosa County, Alabama, twelve of the twenty-eight 
girders were instrumented for use in this study of transfer bond behavior.  All of the 
girders were PCI Bulb-Tee girders and were plant-cast with either a conventionally 
vibrated concrete (CVC) mixture or with a self-consolidating concrete (SCC) mixture.  
Two different girder sizes were cast: BT-54 with a length of 97 ft 10 in. and BT-72 with a 
length of 134 ft 2 in.  The twelve girders selected to undergo analysis included three BT-
54 girders of CVC, three BT-54 girders of SCC, three BT-72 girders of CVC, and three 
BT-72 girders of SCC.  Further details about the design and fabrication of the girder 
specimens are presented in this chapter. 
3.2 Specimen Identification 
In order to distinguish the twelve girders and the specific transfer zone location 
being referred to, a specimen identification system was developed and can be seen in 
Figure 3-1. 
42 
 
 
Figure 3-1: Specimen Identification 
The first distinguishing factor for the girders is the height of the specimen in 
question.  Half of the girders were 54 in. in height and the other half were 72 in. in 
height, corresponding to the designation BT-54 and BT-72 respectively.  A numbering 
scheme was established by the precast concrete producer to number the girders from 1 to 
14 for the BT-54 girders and 1 to 14 for the BT-72 girders to aid during the erection 
process.  These identification numbers were also applied to the girder specimens so that 
associations between each girder and their final location within the finished bridge were 
possible if ever needed. 
Girders 1 through 7 of both the 54 in. and 72 in. girders were cast using SCC, 
designated with an ?S?, and girders 8 through 14 were cast with CVC, designated with a 
?C?.  It was then necessary to distinguish between the two ends of each girder as both 
ends were utilized to collect transfer length data.  The mark end, which was located on 
the east end of the girder when on the casting line in the plant and should be the 
43 
 
southwest end of the girder in the actual bridge, is denoted by an ?A?.  The non-marked 
end is denoted ?B?. 
Finally, two different strand-bonding zones were under investigation in several of 
the members: the transfer zone for the fully bonded strands and the transfer zone for the 
debonded strands.  The fully bonded transfer strands at the end of each girder consisted of 
twenty-two strands at the bottom of the member.  This region is designated ?F?.  
Debonded strands in the bottom of each girder were covered with a plastic sleeve for a 
length of 10 feet measured from the girder end.  The resulting transfer zone for these 
partially debonded strands is denoted ?D?.  For strain measurement purposes, it was also 
necessary to distinguish between the north and south faces of the girder while the girder 
was sitting in the prestressing bed at the plant. 
 3.3 Specimen Design 
Figure 3-2 and Figure 3-3 show the standard dimensions of a BT-54 girder and a 
BT-72 girder respectively.  The BT-54 girders were 97 ft 10 in. in length and the BT-72 
girders were 134 ft 2 in.  In addition to these dimensions, each girder was skewed in 
order for the bridge to have the proper orientation once constructed.  As a result, every 
girder, regardless of it being a BT-54 girder or a BT-72 girder, had a 15 degree skew. 
44 
 
 
Figure 3-2: Typical BT-54 Girder Cross Section 
?? Chamfer 
3?-6? 
2?-2? 
4?-6? 
2? 
3.5? 
2? 
3?-0? 
4.5? 
6? 
2? 
1?-6? 
6? 
10? 
45 
 
 
Figure 3-3: Typical BT-72 Girder Cross Section 
3.3.1 Strand Arrangement 
Given the difference in size and length between the BT-54 girders and the BT-72 
girders, it was necessary to have two different strand arrangements for each of the 
girders.  All strands were seven-wire, Grade 270, low-relaxation strands and were either 
?-inch strands or ?-inch ?special? strands.  The BT-54 girders contained a total of forty 
strands: twenty-eight ?-inch diameter strands in the bottom of the section tensioned to 
30,980 pounds each, eight ?-inch diameter strands draped along the length of the 
3?-6? 
?? Chamfer 2?-2? 
3.5? 
2? 2? 
4.5? 
6? 
4?-6? 
6?-0? 
10? 
6? 
2? 
1?-6? 
46 
 
member tensioned to 30,980 pounds each, and four ?-inch diameter top strands lightly 
tensioned to 5,000 pounds each. 
The BT-72 girders had the same strand arrangement, but had ten additional 
draped strands, and incorporated ?-inch ?special? strand.  Specifically, it contained 
twenty-eight ?-inch ?special? diameter strands in the bottom of the section tensioned to 
33,800 pounds each, eighteen ?-inch ?special? diameter strands draped along the length 
of the member tensioned to 33,800 pounds each, and four ?-inch diameter top strands 
lightly tensioned to 5,000 pounds each. 
This corresponded to a specified jacking stress (fpj) of 202.5 ksi for the draped and 
the bottom strands and 32.7 ksi for the top strands in both cross sections.  The specific 
location of each strand at both midspan and at the end of the section can be seen in Figure 
3-4 and Figure 3-5 for the BT-54 girders, and Figure 3-6 and Figure 3-7 for the BT-72 
girders.  In addition, the draping profiles can be seen in Figure 3-8 and Figure 3-9. 
47 
 
 
Figure 3-4: Mild Steel and Strand Arrangement for BT-54 Girder at End of Span 
 
 
 
(28) ?? ? Strands 
(4) ?? ? Strands 
(8) ?? ? Strands 
(draped) 
8? 
2? 
2?-4? 
2.5? 
2? 
9.5? 
2? 
3 @ 2? 
1?-0? 1?-0? 2? 8? 
11 @ 2? 
Debonded 
Strands 
Horizontal #4 
Bars in End 
Regions 
Bar S #4 
Bar D #3 
Bar V #3 
Bar Z #5 
48 
 
 
Figure 3-5: Mild Steel and Strand Arrangement for BT-54 Girder at Midspan 
(28) ?? ? Strands 
(4) ?? ? Strands 
(8) ?? ? Strands 
(draped) 
8? 
2? 
3?-5.5? 
2.5? 
2? 
2? 
4 @ 2? 
1?-0? 1?-0? 2? 8? 
11 @ 2? 
Bar Z #5 
Bar S #4 
49 
 
 
Figure 3-6: Mild Steel and Strand Arrangement for BT-72 Girder at End of Span 
8? 
3 @ 2? 
2.5? 
2? 2? 
9.5? 
2? 
8 @ 2? 
3?-0? 
1?-0? 1?-0? 2? 8? 
11 @ 2? 
(28) ?? ? Special Strands 
(4) ?? ? Strands 
(18) ?? ? Special 
Strands (draped) 
Bar Z #6 
Bar S #4 
Bar V #3 
Debonded 
Strands 
Horizontal #4 
Bars in End 
Regions 
50 
 
 
Figure 3-7: Mild Steel and Strand Arrangement for BT-72 Girder at Midspan 
 
8? 
9 @ 2? 
2.5? 
2? 2? 
9.5? 
2? 
4?-1.5? 
1?-0? 1?-0? 2? 8? 
11 @ 2? 
(28) ?? ? Special Strands 
(4) ?? ? Strands 
(18) ?? ? Special 
Strands (draped) 
Bar Z #5 
Bar S #4 
 
 
 
51
 
 
 
Figure 3-8: Profile and Hold-Down of Draped Strands for BT-54 Girder 
 
 
Figure 3-9: Profile and Hold-Down of Draped Strands for BT-72 Girder 
 
C.L. Hold-Down 
Point 22?-0? 
67?-1? 
C.L. Hold-Down 
Point 16?-0? 
48?-11? C 
L 
C L 
 
52 
 
It was also necessary to debond some strands to satisfy allowable stress limits.  
Consequently, four strands were debonded for a distance of 10 ft from the end of the 
girder in the BT-54 girders, and six strands were debonded for the same length in the BT-
72 girders.  This was accomplished by sheathing the strands with a plastic casing and 
sealing with tape.  The debonded strands are denoted with a circle around the strand in 
the figures above. 
3.3.2 Nonprestressed Reinforcement Arrangement 
The configuration of nonprestressed steel, used to resist shear forces and 
anchorage zone forces, was the same for both bulb-tee girder shapes, the only difference 
being the spacing and distances over which the mild steel reinforcing bars were placed.  
There were four different shapes used in the steel cages which included Z-bars, bottom 
steel confinement (D-bars), straight bars (S-bars), and V-bars.  These shapes and their 
location within the cross section can be seen in Figure 3-4 through Figure 3-7.  The 
spacing at which the mild steel is placed throughout the girder is visible in Figure 3-10 
and Figure 3-11. 
In addition to the mild steel spaced throughout the length of the girder, there were 
six additional S-bars in the BT-54 girders and fourteen S-bars in the BT-72 girders which 
were placed in each end of the girder.  The additional bars were placed horizontally, 
parallel to the prestressing strands, and ran from the end of the girder into the web of the 
section for a distance of 52 in. in the BT-54 girders and 72 in. in the BT-72 girders.  The 
vertical location of the bars can be seen in the cross-section diagrams: Figure 3-4 and 
Figure 3-6, as well as the longitudinal placement in Figure 3-10 and Figure 3-11. 
 
 
 
 
53
 
   
Figure 3-10: Mild Steel Spacing in BT-54 Girders 
 
 
Figure 3-11: Mild Steel Spacing in BT-72 Girders 
38 @ 17 5/8? 
18 @ 4? 
18 @ 4? 8 @ 12? 
6 @ 18? 
6 @ 18? 
14 S Bars #4 
43 @ 14 3/4? 
S Bar #4 
 
V Bar #3 
 
D Bar #3 
 
Z Bar #5 
 
4 @ 6? 
Z Bar #5 
D Bar #3 
V Bar #3 
14 @ 4? 
14 @ 4? 5 @ 10? 7 @ 12? 27 @ 14 5/8? 
4 @ 6? 
6 @ 18? 
6 @ 18? 
6 S Bars #4 
S Bar #4 38 @ 17 7/16? 
C L 
C L 
 
54 
 
Given the large spalling and bursting stresses that result from anchorage of the 
prestressing forces, the mild steel was heavily concentrated in the ends of the girders in 
order to counteract the effects any cracking in the region may induce.  This can be seen in 
the fact that the spacing of the steel in the girder ends is much denser than at midspan, as 
well as the fact that the bottom confining steel and the V-bars are only located in these 
regions, as can be seen in Figure 3-12. 
 
Figure 3-12: End of Span Steel Configuration 
3.4 Material Properties 
The material properties of all the components used in the construction of the bulb 
tee girders are discussed in this section.  The materials include CVC, self-consolidating 
concrete, prestressing strand, and nonprestressed reinforcement. 
 
55 
 
3.4.1 Concrete 
Two different concrete mixtures were used in the fabrication of the bulb-tee 
girders, all of which was mixed on site at Hanson Pipe & Precast prestressing plant in 
Pelham, Alabama.  The concrete mixtures were designed by the contractor to satisfy the 
special provision for the prestressed bridge girders, which can be seen in Appendix B.  
The two concrete mixtures included CVC and SCC, both of which included Type III 
portland cement.  All of the admixtures were supplied by W.R. Grace and included an 
air-entraining admixture (Darex AEA EH), a hydration-stabilizing admixture (Recover), 
a viscosity-modifying admixture (V-Mar 3), and a high-range water reducing admixture 
(ADVA Cast 575).  The admixtures are presented in terms of ounces per cubic yard.  
Besides differences in the amounts of admixtures added, the SCC contained #78 
limestone, whereas the CVC contained #67 limestone.  Summaries of the components 
used in each mixture can be seen in Table 3-1.  After casting the BT-54 girders, the plant 
personnel felt that the SCC mixture could be improved upon, which was reflected by the 
slight variation in the BT-72 SCC mixture, which included double the amount of VMA. 
  
 
56 
 
Table 3-1: Summary of Concrete Mixtures 
Item 
BT-54 BT-72 
SCC CVC SCC CVC 
Water Content (pcy) 266 238 265 234 
Cement Content (pcy) 758 696 760 708 
GGBF Slag Content (pcy) 134 124 135 125 
w/cm 0.30 0.29 0.30 0.28 
SSD Coarse Agg. #78 (pcy) 1528 0 1550 0 
SSD Coarse Agg. #67 (pcy) 0 1923 0 1950 
SSD Fine Agg. (pcy) 1384 1163 1370 1179 
s/agg (by weight) 0.48 0.38 0.47 0.38 
Air-Entraining Admixture (oz/cy) 0.3 0.3 0.2 0.2 
HRWR Admixture (oz/cy) 11 8 11 7 
Viscosity-Modifying Admixture (oz/cy) 2 0 4 0 
Hydration-Stabilizing Admixture (oz/cy) 2 1 2 1 
Total Air Content (%)* 4.1 4.2 4.0 3.2 
*Average of air content determined from fresh test results. 
It was necessary to batch large quantities of each mixture during any given girder 
placement, thus, a representative sample were taken at the beginning, middle, and end of 
the casting process for each mixture each day.  Fresh concrete properties were tested, the 
results of which can be seen in Table 3-2.  Traditional data were collected for the CVC 
mixtures, including the slump, air content, and unit weight of the concrete.  Additional 
properties collected for the SCC included the slump flow, visual stability index (VSI) 
rating, and T-50 test result.  The slump and slump flow values reported were from tests 
performed by Auburn University researchers for research purposes only, while the slump 
and slump flow values taken for concrete acceptance purposes were not included.  
Occasionally, the first batch of concrete was rejected by ALDOT inspectors because of 
test results that were outside of the acceptable ranges which are defined in Appendix B. 
 
57 
 
Table 3-2: Fresh Concrete Properties 
Beam Sample No Unit Weight Slump Slump Flow Air T50 VSI (lbs) (in.) (in.) (%) (sec.) 
54-2S 
1 149.1 - 28.00 3.3 - 1.5 
2 - - 27.50 4.4 - 1.0 
3 - - 26.00 4.5 - 1.0 
54-4S 
1 - - 27.00 2.6 7 1.0 
2 - - 26.00 3.0 6 1.0 
3 - - 27.00 4.6 8 1.0 
54-7S 1 - - 26.00 5.5 7 1.5 2 - - 26.00 4.2 8 1.5 
54-8C 1 - 9.00 - 4.5 - - 2 - 8.75 - 3.9 - - 
54-11C 
1 - 8.50 - 4.2 - - 
2 - 9.00 - 4.5 - - 
3 - 8.75 - 4.4 - - 
54-13C 
1 152.3 9.00 - 3.9 - - 
2 153.2 10.00 - 4.0 - - 
3 - 8.75 - 4.0 - - 
72-2S 
1 149.8 - 22.50 4.2 9 1.0 
2 - - 24.00 3.7 10 1.0 
3 - - 22.00 3.8 15 1.0 
72-4S 
1 - - 26.00 3.3 8 1.0 
2 - - 26.00 4.3 9 0.0 
3 - - 23.00 4.8 14 0.0 
72-7S 
1 150.1 - 25.00 3.7 10 0.0 
2 - - 23.00 4.5 10 0.0 
3 - - 24.00 3.8 11 0.0 
72-8C 
1 - 8.50 - 4.0 - - 
2 - 9.00 - 4.3 - - 
3 - 8.75 - 3.5 - - 
72-11C 
1 153.4 8.50 - 3.6 - - 
2 - 9.00 - 3.1 - - 
3 - 9.00 - 3.5 - - 
72-13C 
1 - 9.00 - 3.1 - - 
2 - 9.00 - 2.5 - - 
3 - 9.25 - 3.1 - - 
 
 
 
58 
 
During casting, representative 6-inch by 12-inch concrete sample cylinders were 
made.  As the age of the concrete reached different benchmarks, the cylinders were tested 
to determine the concrete properties at the time in question.  The averaged results of the 
hardened concrete properties for each girder can be seen in Table 3-3, as well as the 
amount of time that had elapsed between the placement of the concrete and the 
prestressed strand release the following day.  In addition, the required strengths that had 
to be obtained for the girders of each size are also shown. 
Table 3-3: Hardened Concrete Properties 
 Release 28-Days 
Beam Age  f'ci Eci f'c Ec (hrs) (psi) (ksi) (psi) (ksi) 
54-2S 24 9010 6200 10240 6400 
54-4S 24 8680 6300 10800 6600 
54-7S 24 7940 6100 10180 6200 
54-8C 25 8760 6400 10360 6800 
54-11C 24 7860 6700 9670 6900 
54-13C 23 8790 7100 10590 7400 
Required 
BT-54 - 5200 6000 - - 
72-2S 22 8220 5800 10550 6400 
72-4S 19 7860 5900 10770 6400 
72-7S 24 8120 5800 10490 6300 
72-8C 23 8290 6700 10770 7000 
72-11C 20 8320 6800 11050 7700 
72-13C 22 8770 7100 10850 7300 
Required 
BT-72 - 5800 8000 - - 
 
The concrete strength at prestress release was significantly higher than the 
required strength specified for both the BT-54 girders and the BT-72 girders.  This could 
 
59 
 
be a function of the strands not being released until approximately 23 hours after concrete 
placement as opposed to release occurring approximately 18 hours after placement which 
is closer to an industry standard.  A summary of both the fresh and hardened concrete 
properties can be seen in Table 3-4. 
Table 3-4: Summary of Concrete Properties 
  SCC CVC 
  Range Average Range Average 
Fr
esh
 Pr
op
ert
ies
 Unit Weight (lbs) 149.1-150.1 149.7 152.3-153.4 153.0 
Slump (Flow) (in.) 22.0-28.0 25.2 8.5-10.0 8.9 
Air (%) 2.6-5.5 4.0 2.5-4.5 3.8 
T50 (sec) 6-15 9.5 - - 
VSI 0.0-1.5 1.0 - - 
Ha
rd
en
ed
 
Pr
op
ert
ies
 
Age at Release (hrs) 19-24 23 20-25 23 
f'ci (psi) 7860-9010 8310 7860-8790 8460 
f'c (psi) 10180-10800 10510 9670-11050 10550 
Eci (ksi) 5800-6300 6020 6400-7100 6800 
Ec (ksi) 6200-6600 6380 6800-7700 7180 
 
3.4.2 Prestressing Strand 
The strand used in this investigation was low-relaxation, Grade 270, seven-wire 
prestressing strand.  Two different sizes were used: the BT-54 girders contained ?-inch 
strand, where as the BT-72 girders incorporated ?-inch ?special? strand.  All of the strand 
was stored outside using normal practices for ALDOT girders and exhibited some slight 
weathering effects.  The typical surface condition of the strand can be seen in Figure 
3-13.  The steel was supplied by two different strand providers.  The ?-inch strand was 
 
60 
 
provided by Strand-Tech Martin, Inc. out of Summerville, South Carolina.  The ?-inch 
?special? strand was provided by American Spring Wire out of Houston, Texas: the same 
type and manufacturer as the strand used for the previous phases of prestressed SCC 
research at Auburn University. 
 
Figure 3-13: Typical Surface Condition of Prestressing Strand 
Strand pullout testing was employed to determine a quantifiable estimate of the 
relative bond quality of the strands prior to construction of the girders.  After testing both 
the ?-inch and the ?-inch ?special? strands, it was determined that the strands met the 
acceptability criteria specified by Logan (1997) without exhibiting excessively strong 
bond capacity.  This was a desirable result as it allows for the transfer length behavior 
measured in this study to be representative of what could be expected from strands that 
have acceptable, but not superior, bond capacity.  A description and the results of the 
pullout tests are detailed in Appendix C. 
3.4.3 Nonprestressed Steel Reinforcement 
Nonprestressed, mild steel reinforcing bars were used to strengthen the section in 
relation to shearing and anchorage forces and to limit the size of any associated cracks.  
The steel used was ASTM A615 Grade 60 reinforcing bars.  As mentioned earlier, four 
different shapes were used, each of which can be seen in Figure 3-4 and Figure 3-6.  
 
61 
 
Additionally, the spacing of these bars can be seen in Figure 3-10 and Figure 3-11.  The 
bars ranged in size from #3 bars to #6 bars. 
3.5 Specimen Fabrication 
The twenty-eight girders were fabricated for State Route 22 over Hillabee Creek 
in Tallapoosa County, Alabama at Hanson Pipe and Precast prestressing plant in Pelham, 
Alabama in September and October 2010.  However, transfer behavior was studied on 
only twelve of the twenty-eight girders.  While two different sized girders were created, 
the process followed to cast a girder of either size is identical and is described in the 
following section. 
3.5.1 Casting Configuration of Precast, Prestressed Bridge Girders 
Each of the girders was cast on one of two lines utilized for the project in the 
prestressing plant.  Due to the length of the casting beds, it was possible to cast three BT-
54 girders on one line, with a single line being cast in one day.  The bed layout for a 
typical single casting day of BT-54 girders can be seen in Figure 3-14.  Two days of 
casting with CVC were completed as well as two days of casting using SCC, creating 
twelve of the fourteen BT-54 girders needed for the bridge.  To complete the castings 
required for the BT-54 girders, a single casting of only two girders on the line was done 
to create the thirteenth and fourteenth girders, one girder being cast with CVC and the 
other with SCC.  In this case, the CVC girder was cast first so that the vibration used on 
the girder would not affect the SCC girder.  The girder layout for the last day of casting 
for the BT-54 girders can be seen in Figure 3-15. 
 
 
62 
 
 
Figure 3-14: Casting Configuration of Three BT-54 Girders 
 
 
Figure 3-15: Casting Configuration of Two BT-54 Girders 
 
Given the extra length associated with the BT-72 girders, it was only possible to 
cast two girders on a line, with this configuration being seen in Figure 3-16.  This 
resulted in three days of casting with CVC and three days of casting with SCC.  To fulfill 
the number of girders, one last day of casting was done with one beam each of CVC and 
SCC. 
 
 
Figure 3-16: Casting Configuration of BT-72 Girders 
 
Throughout this process, only a single beam per casting was designated as a 
specimen for use within the study.  The one exception was both beams from the final day 
of BT-54 casting, which consisted of one CVC girder and one SCC girder, were utilized.  
E E W W 
E E W W 
E E E W W W 
 
63 
 
Casting dates for the girders spanned from September 21, 2010 to October 28, 2010.  The 
BT-54 girders were cast first, followed by the BT-72 girders.   
3.5.2 Fabrication of Precast, Prestressed Bridge Girders 
Normal plant casting procedures and protocol were followed since the girders cast 
during the duration of the study were for use in a bridge, not strictly for research.  Given 
the size and type of girders needed, the prestressing bed was laid out with the proper 
components required to cast the appropriately sized girder.  Once this was done and the 
bed was cleaned, strand was pulled in the correct configuration through the headers and 
the numerous hold-down points (for draped strands).  The hold-up points were then raised 
to the proper elevation so that the draped strands would acquire the correct draping 
configuration once the strands were tensioned.  
The strands were pulled to the specified jacking stress using a hydraulic jack.  
Each strand was partially stressed before pulling it to its final tension, allowing an 
opportunity to discover a major flaw in the strand prior to a sudden failure.  Strand 
tensions and elongations were checked according to standard ALDOT-mandated 
procedures. 
Once the strands were in the correct location and tensioned to the appropriate 
force, plastic sheaths were added to designated strands for debonding and tied into place.  
The strands designated as debonded strands can be seen in Figure 3-4 and Figure 3-6.  A 
picture of the installed sheaths can be seen in Figure 3-17.  These strands were debonded 
for a designated length of 10 ft from the end of the girder in both girder sizes.  Finally, 
the mild steel reinforcing cage was built around the strands.  This was done by tying the 
pre-bent deformed rebar into the correct locations and tying the bars and strands together.  
 
64 
 
The bed of the forms was then oiled by squirting the oil underneath the strands.  This was 
done very carefully to prevent the oil from coming into contact with the strands and 
compromising the integrity of the bond. 
 
Figure 3-17: Plastic Sheathing on Debonded Strands 
As fully described in Chapter 4, a new system of mounting the demountable, 
mechanical (DEMEC) points, used in measuring the surface compressive strains of the 
concrete in order to determine the transfer lengths, for the study was created.  The new 
system required a portion of the system to be cast into the girder.  Consequently, the pre-
fabricated portion of the DEMEC bars was installed into the steel cage at six designated 
locations prior to the formwork being moved into place.  Section 4.2.2 gives a complete 
description of this process.  A bar tied to the prestressing strands can be seen in Figure 
3-18. 
 
65 
 
 
Figure 3-18: DEMEC System Tied into Steel Cage 
Before the forms were put into place, they were sprayed with a form release agent 
that allowed for easy removal of the forms once the concrete was hardened.  It was 
imperative to ensure the release agent did not come into contact with the mild steel or the 
prestressing strands.  If this were to happen, the form oil would prevent the steel from 
becoming properly bonded to the concrete, the prestressing would be rendered 
ineffective, and the girder would be substandard and unsafe.  The side forms were then 
put into place and secured.  The beginning of this process can be seen in Figure 3-19. 
 
66 
 
 
Figure 3-19: Formwork Being Put into Place 
All of the concrete was batched on site and transported from the batching area to 
the prestressed beds by a concrete delivery vehicle which could carry 4 cubic yards of 
concrete.  Figure 3-20 shows one of the vehicles placing concrete into the formwork.  
Numerous trips were required from the batching area to the prestressing line in order to 
fill the formwork.  While the trucks were transporting the concrete, a truck was 
occasionally pulled aside in order to test the fresh concrete to ensure its properties met 
the project specifications, shown in Appendix B, as well as to sample the concrete. 
 
67 
 
 
Figure 3-20: Concrete Delivery Vehicle Placing Concrete 
The process used to place the CVC and the SCC was different given the different 
physical characteristics of each concrete.  To place the CVC, the concrete delivery 
vehicle would begin placement at one end of the girder and release discrete amounts of 
concrete before inching forward and releasing more concrete.  The concrete was very 
viscous and deliberate placement was required as the concrete did not easily move once 
placed and care had to be taken to not overfill the form at any one location.  Figure 3-21 
shows this as the concrete can be seen building up behind the vertical bars preventing the 
concrete from moving into the next area.  Another concrete delivery would follow behind 
the first, placing concrete to fill the formwork. 
 
68 
 
 
Figure 3-21: CVC Placement 
It was also necessary to use vibration for the CVC placement  in order to ensure 
that all the air pockets were eliminated that may have formed in the girder.  This was 
done in two ways.  First, an external vibrator was mounted in a track on the side of the 
formwork that ran along the length of the girder, which is visible in Figure 3-22.  As the 
concrete was placed, the vibrator was moved along the track, show in Figure 3-23, 
appropriately.  Second, the workers also used internal vibration, as can be seen in Figure 
3-24. 
 
 
 
69 
 
 
Figure 3-22: External Vibrator 
 
 
Figure 3-23: External Vibration Track 
 
70 
 
 
 
Figure 3-24: Internal Vibration of Concrete 
The SCC was much easier to place.  As with the CVC, the concrete delivery 
vehicle began placement at one end of the girder.  As the SCC was released, it would 
flow into the formwork and through the steel cages under its own weight and without the 
need for internal vibration.  Care still had to be taken as the rate at which the SCC flowed 
was slower than the rate at which the concrete was dispensed from the delivery truck via 
an auger-driven chute.  As a result, the concrete delivery vehicle was still required to 
move along the length of the girder.  However, the SCC was still easier to place as the 
trucks did not need to move near as often, nor be as precise in where along the girder the 
concrete was placed.  It was also safer for the workers as individuals were not on top of 
the form work applying internal vibration.  Figure 3-25 shows the concrete that has 
 
71 
 
almost filled the web from a previous placement, as well as concrete from a more recent 
placement flowing from the discharge point to fill the web and starting to fill the flange. 
 
Figure 3-25: Placement of Self-Consolidating Concrete 
In the two situations in which a conventional girder and a SCC girder were cast 
on the same line on the same day, which occurred once for the set of BT-54 girder 
castings and once for the BT-72 girders, the conventional girder was always cast first.  As 
the formwork was continuous along the entire length of the bed, any vibrations applied to 
the conventional girder would have some effect on the entire bed.  Placing the CVC and 
 
72 
 
vibrating it before the placement of the SCC guaranteed that the SCC would not receive 
any vibrations that could affect the resulting girder. 
After all the concrete had been placed, the top surface was roughened and any 
accessories required for the particular girder were added.  The surface was roughened to 
approximately ? in. by running a type of metal rake with several fingers across the wet 
concrete as seen in Figure 3-26.  However, given that the SCC would not keep a 
roughened surface since the concrete would just reconsolidate after being raked, the SCC 
girders were not raked until the top concrete surface had started to set slightly to allow it 
to retain the roughened surface.  Finally, a curing blanket and a weatherproof tarp were 
draped over the bed and forms, pictured in Figure 3-27, to help the concrete to cure and 
was left overnight.  In addition, all of the girders were steam cured. 
 
Figure 3-26: Concrete Surface Roughening 
 
73 
 
 
Figure 3-27: Curing Blankets and Placement of Weatherproof Tarp 
The next day, approximately 23 hours after the concrete had been placed, the 
curing blankets were rolled up, and the side forms removed.  Figure 3-28 shows the 
removal process.  The final steps required to prepare the DEMEC strain-measurement 
system, which is described in detail in Chapter 4, were completed and the actual distance 
from the end of the girder to the center of the first DEMEC point was measured to the 
nearest quarter inch.  Finally, an initial set of measurements were taken, the process of 
which is also included in Chapter 4. 
 
74 
 
 
Figure 3-28: Removal of Side Forms 
After representative concrete cylinders were tested to ensure the concrete had 
reached the required strength for release, the prestressing force was transferred to the 
girders by flame cutting the strands, which can be seen in Figure 3-29.  This required 
several workers, one located at the far east and west ends of the bed, as well as a man at 
every space in between girders.  The men then proceeded to cut the strands.  The order 
the strands were cut was predefined and, after each cut, the workers checked to make sure 
each cut for a single strand was made before continuing to the next strand.  Diagrams of 
this sequence for both the BT-54 girders and the BT-72 girders can be seen in Figure 
3-30 and Figure 3-31.  The strands were flame cut in the following order: the very bottom 
outside strand on either side, the four top strands, the top two draped strands, the hold-
down points, each remaining draped strand working from top to the bottom of the draped 
 
75 
 
portion, and the bottom strands working from the top to the bottom and from the outsides 
in.   
 
Figure 3-29: Flame Cutting 
 
76 
 
 
Figure 3-30: Flame Cutting Sequence for BT-54 Girders 
 
Figure 3-31: Flame Cutting Sequence for BT-72 Girders 
2 
1 
3 
7 
13 
9 
5 4 
8 
10 
6 
14 
12 
1 
15 
11 
Note: Release hold-down 
after cutting #3 
1 
3 
8 
5 4 6 
9 
7 
1 
10 
2 
Note: Release hold down 
after cutting #3 
 
77 
 
Once the strands had been released, a second set of DEMEC measurements were 
taken before the girders were moved into the storage yard by large mobile cranes.  A 
crane carrying a BT-54 girder into the storage area is shown in Figure 3-32.  When 
moving the BT-72 girders, two cranes were required due to the longer length of the BT-
72 girders.  The girders were then stored in the yard, having been placed on supports that 
were configured to resemble the final support conditions within the bridge.  The support 
conditions and end of three BT-54 girders in the storage yard can be seen Figure 3-33.  
The girders were kept in the yard until they were transported to the bridge site for 
construction. 
 
Figure 3-32: Transporting BT-54 Girder to the Storage Yard 
 
 
78 
 
 
Figure 3-33: Girder Support Conditions in Storage Yard
 
79 
 
Chapter 4 Transfer Length Test Program 
4.1 Introduction
Twelve PCI bulb-tee girders were studied and analyzed with respect to their 
transfer lengths.  Each girder had four transfer zones, one at each end of the girder and 
one at each end associated with the transfer zone of the debonded strands.  Each end 
transfer zone was examined for all twelve girders, along with one of the two debonded-
strand transfer zones for ten of the twelve girders.  Consequently, there were thirty-four 
resulting transfer zones: twenty-four end transfer zones and ten debonded-strand transfer 
zones.  Transfer lengths were determined by analyzing the concrete surface strains 
measured in each transfer zone.  A demountable, mechanical (DEMEC) strain gauge was 
used to measure the concrete surface strains.  Strains were measured immediately after 
prestress transfer, as well as at 7 days and 28 days after transfer in order to capture any 
time-dependant changes in the transfer length.  The measurement techniques are 
described in this chapter. 
4.2 Test Procedure 
Given the large scale of the specimens being tested and the fact that testing would 
occur on the premises of the precast plant facility, a new method and system for 
mounting the demountable, mechanical (DEMEC) points was created that allowed for the 
DEMEC points to be inserted into the concrete rather than having to be glued to the 
surface.  Inspiration for the instrumentation adapted for use within this study was inspired 
 
80 
 
by similar methods utilized by Ben Graybeal of the Federal Highway Administration and 
Canfield (2005).  This new method required significant preparations before casting, but 
allowed for a reduction in both the time needed and the number of procedural steps 
required between form removal and prestress transfer?minimizing disruption of normal 
plant production procedures. 
4.2.1 Cast-In-Place DEMEC Mounting System 
The DEMEC mounting system was fabricated and constructed to allow the 
DEMEC targets to be easily and quickly mounted onto the concrete girder specimen.  It 
was also important to create a system that could be easily installed at the plant.  The 
following section details the DEMEC mounting system that was utilized in the plant. 
The DEMEC bars each consisted of a 72 in. x 1 in. metal strip with thirty-four 
holes spaced at 50 mm on center.  Each of the holes was countersunk at 82 degrees to 
accommodate a machine screw.  Five larger holes were then countersunk at each end and 
at equal intervals along the bar in between the holes previously made. 
The bars were assembled by placing a screw into each of the thirty-four smaller 
holes.  A drop of lubricant was then placed on the screw before a washer and a threaded 
insert were attached to it and tightened until it was finger-tight.  Larger screws were then 
inserted into the five larger holes, lubricant added, a washer, coupling nut, and threaded 
rod attached until these too were finger-tight.  The assembled hardware can be seen in 
Figure 4-1 with the entire bar shown in Figure 4-2. 
 
81 
 
 
Figure 4-1: Assembled DEMEC Mounting System 
 
Figure 4-2: Fully Assembled DEMEC Mounting System 
Threaded Rod 
Coupling Nut 
Washer 
Threaded Insert 
DEMEC Bar 
 
82 
 
The intent behind the design of the mounting system was to devise a way to have 
the threaded inserts cast into the concrete at the locations where DEMEC measurements 
were desired.  The threaded rods were added to the system to provide a way to tie the bar 
into the steel cage prior to casting.  Once all of the hardware had been assembled, a strip 
of quick-recovery super-resilient polyurethane foam with an adhesive backing was placed 
over the heads of the screws and covered the entire length of the bar.  The foam was 
added to prevent concrete from coming into contact with the screw heads, as well as to 
provide a barrier between the formwork and the bar, preventing the bar from being 
embedded completely within the concrete and becoming inaccessible. 
It was also necessary to fabricate specialized DEMEC target screws.  This was 
done by drilling a small hole in the center of hex head screw to ensure the proper 
positioning of the conical points of the DEMEC gauge.  A fabricated DEMEC screw is 
shown in Figure 4-3. 
  
Figure 4-3: DEMEC Screw 
4.2.2 Specimen Preparation 
Each girder had six segments along which measurements were taken with each 
segment being 5.5 feet in length to ensure the entire transfer length was captured within 
the segment.  These segments were located on the bottom flange of each girder and 
 
83 
 
included each end of the girder, as well as a segment starting 9 feet from the mark end of 
the girder to capture the transfer length of the debonded strands.  Thus, there were three 
transfer zones measured, each with a segment on each girder face.  These segment 
configurations can be seen in Figure 4-4. 
 
 
 
Figure 4-4: Location of Areas Analyzed for Transfer Length, BT-54 and BT-72 
(Mirrored on Opposite Face) 
The pre-fabricated portion of the DEMEC bars was installed into the steel cage 
and can be seen in Figure 4-5.  Each bar was anchored so that the DEMEC strip stood 
slightly outside the edge of the bed.  Consequently, when the forms were moved into 
place prior to the concrete placement, the final location of the DEMEC bar would be snug 
against the form, also helping to prevent the bar from becoming embedded in the 
concrete. 
108? 
108? 
BT-54 
BT-72 
 
84 
 
 
Figure 4-5: Final Location of DEMEC Bar Prior to Casting 
Once the concrete had cured overnight, the tarps and formwork were removed.  
At this point, the DEMEC strips could be seen on the outside face of the bottom flange of 
the bulb tee girder, as seen in Figure 4-6.  Despite all efforts, on occasion it was possible 
for some paste to seep in between the foam and the forms.  When this occurred, the thin 
paste was easily knocked away with a hammer.  It was then possible to remove the foam, 
exposing the heads of the screws that had been used to hold the threaded inserts prior to 
hardening of the concrete.  This can be seen in Figure 4-7. 
 
85 
 
 
Figure 4-6: Exposed DEMEC Strip Immediately After Form Removal 
 
Figure 4-7: Removal of Foam Adhesive 
Each screw was removed with a power drill, including the screws associated with 
the threaded anchors, and discarded.  Doing this allowed the metal strip to be pried away 
from the concrete, as seen in Figure 4-8, leaving a smooth surface with a threaded insert 
at every location a DEMEC target was needed.  At this point, the prefabricated DEMEC 
target screws could be screwed into place.  The beginning of this process is shown in 
Figure 4-9.  Finally, each DEMEC target was labeled with odd numbers from one to 
 
86 
 
sixty-seven beginning with the point closest to the end of the girder.  Since each point 
was located 50 mm, or approximately 2 inches, from the next point, these labels 
represented the approximate distance the DEMEC point was from the end of the girder, 
in 25 mm increments.  A finalized DEMEC segment can be seen in Figure 4-10.  As a 
result, the DEMEC targets could be measured at any time of interest. 
 
Figure 4-8: Removal of Metal DEMEC Bar 
 
87 
 
 
Figure 4-9: DEMEC Strip after Metal Bar Removed and DEMEC Points Started 
 
Figure 4-10: Finalized DEMEC Target Installation 
4.2.3 Concrete Surface Strain Measurement 
The process for reading the DEMEC targets with the gauges was consistent 
throughout the entire project.  Before any of the points were measured, an initial 
reference reading was taken of an Invar reference bar corresponding with the gauge in 
 
88 
 
use and was recorded.  The process of measuring the DEMEC points was then started.  A 
200 mm DEMEC strain gauge was used to read the points, and can be seen in Figure 
4-11, along with the reference bar.   
 
Figure 4-11: DEMEC Strain Gauge and Reference Bar 
To measure the distance between the points, the moveable conical point of the 
gauge was inserted in the target on the right-hand end of the 200 mm span.  The fixed 
conical point was then inserted into the left-hand target, and a reading was taken.  The 
left-hand, fixed point was then removed, reinserted into the same target, and the gauge 
read again.  If the second reading was within one gauge divisions (0.0016 mm of surface 
displacement) of the first, both measurements were recorded.  Consequently, each 200 
mm interval was read twice to confirm repeatability in the measurement.  The gauge was 
then moved to the next successive target and the process was repeated.  An image of a 
reading being taken can be seen in Figure 4-12.  Once the measurement had been 
completed, due to the overlapping nature of the measurements, a single 50 mm interval 
 
89 
 
was included within four overlapping 200 mm gauge lengths.  All six segments were read 
to complete a set of measurements for a girder. 
 
Figure 4-12: Performing DEMEC Strain Measurement 
Several different sets of measurements were taken at different ages throughout the 
early life of the girders, as previous studies indicated that the transfer length grew for 
several days after prestress transfer.  The first set of measurements was taken 
immediately after the forms were removed to serve as a benchmark for the undeformed 
state of the girder.  Measurements were also taken immediately after prestress transfer, 7 
days after transfer, and 28 days after transfer, at which point it was determined that the 
transfer length had stopped changing significantly.  The 7- and 28-day strains were 
measured while the girders were in their storage positions in the precast plant.  During 
storage, the girders were supported so as to have the same span length that would be 
 
90 
 
experienced in the actual bridge.  The recorded strains were analyzed to determine the 
transfer length associated with each zone. 
4.3 Determination of Transfer Length 
Once the data had been collected for the thirty-four transfer zones contained 
within the twelve PCI bulb-tee girders, it was analyzed to acquire the appropriate 
information needed to determine the transfer length for each zone.  The raw 
measurements were converted into concrete surface strains that could be plotted and the 
95%  average maximum strain (AMS) plateau was found for each concrete age.  The 
transfer length was measured by determining the distance to the intersection of the 95% 
AMS plateau and the strain profile, as can be seen in Figure 4-13.  The detailed process 
through which this was done is described in the following sections. 
 
Figure 4-13: Compressive Strain Profile 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i
lt,7
lt,28
 
91 
 
4.3.1 Construction of Surface Compressive Strain Profiles 
The first step required to create a surface compressive strain profile for any of the 
girders was to transform the measurements collected at the prestressing facility into strain 
values.  The following steps were followed to perform this conversion. 
1. As some deformation measurements varied by as much as 0.0016 mm 
between the first and second reading, the average reading was determined at 
each location at each age. 
2. A reference reading was taken prior to taking the surface DEMEC target 
measurement for every age throughout the study.  The reference reading for 
each age was subtracted from the surface DEMEC target reading at each 
location for the same age.  The resulting difference is described as the 
?relative reading? in the next step. 
3. The change in compressive strain at each location corresponding to the age in 
question was determined by subtracting the relative reading prior to transfer 
from the relative reading at the age of interest.  The resulting difference was 
then multiplied by the appropriate gauge factor to determine the strain over 
the 200 mm gauge length.  At this stage, each measured strain was assigned to 
the absolute position of the DEMEC point at the middle of the 200 mm gauge 
length measured. 
4. As mentioned previously, the girders were skewed at 15 degrees.  
Consequently, the resulting strains were determined for the center line of the 
girder by averaging the strains from opposite faces of the girder at 
corresponding points (point 1 on the north face was averaged with point 1 of 
 
92 
 
the south face).  The distance from the end of the girder of each point was also 
averaged with the corresponding distance of the point on the other face to 
determine the midpoint between the two points, which can then be used to 
determine the distance from the end of the girder along the centerline for the 
resulting averaged strain. 
5. The strains were then smoothed: a single strain value was assigned to each 
distance along the centerline by averaging the strain assigned to a particular 
location with the strains assigned to the immediately adjacent locations.  A 
visual aid depicting the smoothing portion of this process can be seen in 
Figure 4-14. 
 
 
Figure 4-14: Assignment of Surface Compressive Strain Values 
(Barnes, Burns, and Kreger 1999) 
 
6. The smoothed strain values were then plotted in relation to their absolute 
values.  The resulting graph depicts the concrete strain along the centerline of 
the girder. 
 
93 
 
 
In previous cases in which large specimens were tested for transfer length, as with 
the specimens being tested by Barnes, Burns, and Kreger (1999), adjustments needed to 
be made to account for the self-weight of the girder.  When eccentrically placed 
prestressing strands are released, it causes the member to bend upwards.  As a result, the 
self-weight of the beam induces strains that are superimposed on the strains that result 
from the prestressing alone.  The self-weight strains vary along the length of the member 
and make it difficult to precisely identify the plateau strain that indicates the end of each 
transfer length.  In order to ensure that the transfer lengths were accurately determined, it 
was necessary to consider this effect and account for it. 
In this situation, given the very large size of the girders with respect to both their 
height and length, the self-weight was expected to have a large influence on the 
compressive strain profile results.  Since draped strands were present in this set of 
girders, it was hypothesized that the variable eccentricity of the draped strands could also 
have an effect of on the concrete strains.  However, inspection of the measured surface 
strains indicated that the compressive strains that resulted from the eccentricity of the 
draped strands balanced the self-weight strains so effectively that it was unnecessary to 
make any corrections to the strain profiles that were generated.  This observation agreed 
with elastic strains computed for each of the various sources of deformation.  In addition, 
it was determined that the need for a correction to account for self-weight creep was not 
needed as the effect of adding this correction was smaller than the effective precision of 
the DEMEC gauge.  Also, steps were taken later in the process to account for the larger 
 
94 
 
effect of creep due to the prestress force.  A graph of the compressive strain values for an 
end transfer zone at transfer, at 7 days, and at 28 days is shown in Figure 4-15. 
 
Figure 4-15: Compressive Strain Profile for End Transfer Zone 
(Girder End 52-2S-A-F) 
4.3.2 Determination of Average Maximum Strain: End Transfer Zones 
Once the surface strain profiles were plotted, the 95% AMS method was applied 
to determine the transfer length for each zone.  This was first done by determining the 
100% AMS value.  As can be seen in Figure 4-15, the strains increase at a fairly constant 
slope before a plateau is reached.  As in the definition of transfer length in Section 2.2.1, 
the stress in the strand will continue to increase until the effective prestress is reached 
within the section.  This can be seen visually in the graph as the strain increases along the 
transfer length and then plateaus once the prestress is fully effective.  The 100% AMS is 
the averaged strain value of the plateau portion of the graph, with the onset of the plateau 
being determined visually.  The results for the same girder shown in Figure 4-15 can also 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
 
95 
 
be seen in Figure 4-16 along with the 100% AMS values at each time interval in which 
measurements were taken. 
 
Figure 4-16: 100% AMS of Concrete Surface Strains (Girder End 52-2S-A-F) 
The 95% AMS method was used to determine the transfer lengths within this 
study.  This method uses the intersection of a horizontal line representing 95% of the 
average maximum strain and the surface compressive strain profile to establish the extent 
of the transfer length.  This method was chosen as it requires little or no subjective 
judgment.  While it can be argued whether an additional point should be added or 
removed from the averaged data to determine the 100% AMS, whether it be from the 
interpretation of the beginning of the plateau region or an error in a another point, the 
addition or subtraction of an additional point will have a minor effect on the resulting 
100% AMS value (Russell and Burns 1993).  
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
100% AMS
 
96 
 
A 95% AMS value was used instead of 100% for two reasons.  First, it provided a 
clearly identifiable intersection location between the compressive strain profile and the 
bounding horizontal line (Russell and Burns 1993).  Second, the reduction in AMS, 
which may appear to artificially shorten the transfer length reading, actually compensates 
for the slight artificial elongation of the transfer length that comes from the rounding of 
the strain profile as a result of the smoothing process employed (Boehm 2008). 
The 95% AMS calculation was different for the initial transfer lengths than it was 
for the later-age transfer lengths.  For the initial measurements, as can be expected, the 
95% AMS value was computed by multiplying the 100% AMS value by 0.95.  The 
reduced AMS value was plotted against the strain profile of the measurements taken 
immediately after the release of the prestressing strands.  The location of the intersection 
of the strain profile and the 95% AMS line was taken as the end of the transfer length, 
which can be seen in Figure 4-17. 
 
97 
 
 
Figure 4-17: Transfer Lengths with 95% AMS for End Transfer Zone 
(Girder End 54-2S-A-F) 
However, determining the 95% AMS for any long-term values was more 
complicated.  Two time-dependent factors must be taken into account when analyzing 
long-term data.  First, as the concrete continues to cure, the concrete shrinks.  Second, 
once the strands were cut, the self-weight of the beam began to play a factor.  The girder 
supported its own weight while it continued to cure causing creep.  While both of these 
effects must be considered in long-term 95% AMS calculations, the means in which to 
account for each phenomena were different. 
When looking at the effect of creep, the strains resulting from creep were assumed 
to be proportional to the applied load (Barnes, Burns, and Kreger 1999).  Consequently, 
the strain profile is amplified over time due to creep alone, but the direct use of the 95% 
strain value will not artificially decrease the apparent transfer length.  Thus, this 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=15.0 in.
lt,7=15.5 in.
lt,28=15.5 in.
 
98 
 
technique would remain accurate if all time-dependent strain growth was only due to 
creep. 
Conversely, shrinkage is not proportional to the applied load: it results in a 
translation of the strain profile.  In this case, use of a factor of 0.95 results in an artificial 
decrease in the apparent transfer length (Barnes, Burns, and Kreger 1999).  If all of the 
time-dependent deformation was due to shrinkage, it would be appropriate to reduce the 
100% long-term strain profile by the same strain value (not percentage) by which initial 
100% AMS was reduced. 
The long-term effects are a result of both creep and shrinkage.  After inspecting 
creep and shrinkage data, collected according to ASTM C512 (ASTM 2002) and shown 
in Figure 4-18, for the concrete that had been used to cast the girders, it was estimated 
that 1/3 of the changes were due to shrinkage and 2/3 were due to creep.  Consequently, the 
long-term 95% AMS values were determined by appropriately weighting the creep-only 
and shrinkage-only approaches discussed above.  This can also be seen in Equation 5-1. 
g2013g3030uni002Cg2877g2873uni0025 g3404g2013g3030uni002Cg2869g2868g2868uni0025g3398g3428uni0031uni0033g3435uni0030uni002Euni0030uni0035g1499g2013g3030uni002Cg2869g2868g2868uni0025uni0020g3036g3040g3040g3032g3031g3036g3028g3047g3032g3439g3397uni0032uni0033g3435uni0030uni002Euni0030uni0035g1499g2013g3030uni002Cg2869g2868g2868uni0025g3439g3432 
Equation 5-1 
Where:  ?c,95% is the long-term 95% AMS value desired, 
 ?c,100% is the 100% AMS value at the same long-term time as ?c,95%, and 
 ?c,100% immediate is the 100% AMS value immediately after transfer. 
 
99 
 
 
Figure 4-18: Creep and Shrinkage Data 
4.3.3 Determination of Average Maximum Strain: Debonded-Strand Transfer 
Zones 
Determining the 95% AMS of the debonded strands was more complicated than 
that of the fully bonded strands since it was appropriate to only consider the compressive 
strain resulting from the debonded strands.  To accomplish this, the 100% AMS was 
determined the same way as that of the fully bonded strands: by determining the average 
of the plateau of the compressive strain profile.  This can be seen in Figure 4-19. 
-700
-600
-500
-400
-300
-200
-100
0
0 7 14 21 28
Ti
me
-D
ep
en
de
nt 
Str
ain
 (?
?)
Age of Load (days)
SCC Creep
SCC Creep + Shrinkage
CVC Creep
CVC Creep + Shrinkage
 
100 
 
 
Figure 4-19: 100% AMS of Concrete Surface Strains for Debonded Strand (Girder 
End 72-4S-A-D) 
Once the 100% AMS was determined for the debonded strands, the 100% AMS 
for the same end of the same girder was subtracted from the debonded AMS to determine 
the AMS due to only the debonded strands.  At that point, the same procedure as 
followed previously was applied to account for the 5 percent of the difference between 
the 100% AMS of the fully bonded strands and 100 percent of the debonded strands 
accounting for both creep and shrinkage as was done previously.  Equation 5-2 exhibits 
this process. 
g2013g3030uni002Cg2877g2873uni0025uni0020g3031g3032g3029g3042g3041g3031g3032g3031 g3404g2013g3030uni002Cg2869g2868g2868uni0025uni0020g3031g3032g3029g3042g3041g3031g3032g3031g3398uni0030uni002Euni0030uni0035g1499g4666g2013g3030uni002Cg2869g2868g2868uni0025uni0020g3031g3032g3029g3042g3041g3031g3032g3031g3398g2013g3030uni002Cg2869g2868g2868uni0025uni0020g3029g3042g3041g3031g3032g3031g4667 
Equation 5-2 
Where: ?c,95% debonded is the 95% AMS value for the debonded strain profile, 
 ?c,100% debonded is the 100% AMS value for the debonded strain profile, and 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
100% AMS
 
101 
 
 ?c,100% bonded is the 100% AMS value for the corresponding fully bonded strain 
profile at the same time. 
The same methodology was used to determine the long-term 95% AMS debonded 
values as that which was used for the fully bonded strain profiles, as described in 
Equation 5-1.  Finally, the transfer lengths for the debonded strands were calculated and 
can be seen in Figure 4-20.  Since the sheathing on the strands did not end until 10 feet 
from the end of the girder, the transfer length was taken as the distance from the 
beginning of bonding (120 in. from the end) to the point where the strain profile crossed 
the 95% AMS threshold. 
 
Figure 4-20: Transfer Lengths with 95% AMS for Debonded-Strand Transfer Zone 
(Girder End 72-4S-A-D) 
4.3.4 Precision of Results 
After looking at the factors which were a part of the study, it was determined that 
a transfer length precision of 0.5 inches was suitable.  Given that each DEMEC point was 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,7=11.5 in.
lt,28=12.0 in.
lt,i=11.0 in.
 
102 
 
spaced at 1.97 inches (50 mm), and the results of the strain data were then smoothed and 
interpolated, it would be inappropriate to report results more precisely than to the nearest 
tenth of an inch.  However, given the local conditions in which measurements were 
taken, many of which required awkward movements to read the gauge, and the 
assumptions made with the regard to the involvement of creep and shrinkage in the long-
term analyses, more uncertainty was introduced into system.  Consequently, it was 
judged that 0.5 inches is the most appropriate precision for these transfer lengths.
 
103 
 
Chapter 5 Results and Discussion 
5.1 Results and Discussions
Thirty-four transfer zones were analyzed and incorporated as a part of this study.  
Of these, twenty-four zones anchored fully bonded strands, and ten anchored debonded 
strands.  The results of the testing and analysis are presented in the chapter, along with 
comparisons made with respect to the effects of each parameter considered, the previous 
phases of the study, and the current design convention. 
5.1.1 Transfer Length Results of Fully Bonded Strands 
For the twelve PCI bulb-tee girders tested, twenty-four transfer lengths of fully 
bonded strands were measured.  The strain profiles and the resulting transfer length of 
each transfer zone can be seen in Appendix D.  Each of the zones underwent the analysis 
procedure described previously, resulting in transfer length determination at transfer of 
the prestressing force, seven days after transfer, and twenty-eight days after transfer.  A 
summary of the results, as well as some of the relevant properties, can be seen in Table 
5-1.  The table includes information on the concrete cylinder compressive strength at 
transfer (f?ci), the strand jacking stress (fpj), and the strand stress immediately after 
transfer (fpt).  The concrete strength at transfer, the jacking stress, and the transfer lengths 
were all values that were measured and collected in the field.  The stress in the 
prestressing strand after transfer was calculated based upon the jacking stress, a 
 
104 
 
reasonable estimate for the strand relaxation prior to transfer, and the average concrete 
strain change that was measured at transfer in the girder being examined. 
 
 
 
 
10
5 
Table 5-1: Summary of Transfer Length Results and Properties for Fully Bonded Strands 
 
End A End B 
Concrete Depth (in.) Girder ID f'ci fpj fpt Initial 7-Day 28-Day Initial 7-Day 28-Day (psi) (ksi) (ksi) (in.) (in.) (in.) (in.) (in.) (in.) 
SCC 
54 
2S 9010 202.5 190 15.0 15.5 15.5 15.5 17.5 17.0 
4S 8680 202.5 190 20.0 19.0 20.5 14.0 15.0 15.5 
7S 8760 202.5 190 14.0 16.0 16.5 9.5 10.5 10.0 
72 
2S 8220 202.4 188 16.0 17.5 17.5 14.5 19.0 17.0 
4S 7860 202.4 188 9.5 12.0 13.5 18.0 19.0 20.0 
7S 8120 202.4 188 9.0 9.5 9.0 20.0 19.5 18.5 
CVC 
54 
8C 7940 202.5 190 9.0 12.0 11.5 15.0 19.0 17.0 
11C 7860 202.5 190 10.0 10.5 12.0 12.5 13.5 14.5 
13C 8790 202.5 190 9.0 12.0 11.0 12.0 14.5 14.0 
72 
8C 8290 202.4 190 11.0 13.0 15.0 11.0 13.5 15.0 
11C 8320 202.4 190 10.5 13.0 14.0 9.0 11.5 11.5 
13C 8770 202.4 190 7.5 9.0 10.0 12.5 16.0 16.0 
 
106 
 
5.1.2 Transfer Length Results Partially Debonded Strands 
Ten partially debonded tension zones were considered in four of the BT-54 
girders and six of the BT-72 girders.  The full compressive strain profiles created for each 
debonded-strand transfer zone can be seen in Appendix E.  Table 5-2 shows the transfer 
lengths for the debonded strands at transfer, 7 days, and 28 days. 
Table 5-2: Summary of Transfer Length Results and Properties for Debonded 
Strands 
Concrete Depth (in.) Girder ID f'ci fpj fpt Initial 7-Day 28-Day (psi) (ksi) (ksi) (in.) (in.) (in.) 
SCC 
54 2S 9010 202.5 190 14.5 11.5 12.0 4S 8680 202.5 190 14.0 13.5 13.5 
72 
2S 8220 202.4 187 11.5 13.5 14.0 
4S 7860 202.4 187 11.0 11.5 12.0 
7S 8120 202.4 187 14.5 13.5 13.5 
CVC 
54 11C 7860 202.5 191 13.0 12.0 12.0 13C 8790 202.5 191 12.5 11.5 10.5 
72 
8C 8290 202.4 189 11.5 12.0 13.0 
11C 8320 202.4 189 7.0 9.5 9.5 
13C 8770 202.4 189 12.0 13.5 11.0 
 
5.1.3 Effect of Time 
As previously discussed in Chapter 2, time does play a role in the transfer length 
results.  In previous phases of the study, it was discovered that while the lengths 
continued to grow for several weeks after transfer, the majority of the growth occurred 
within the first few days.  Consequently, measurements were taken for this study at both 
7 days and 28 days in order to capture larger changes that would occur within the first 
few days, as well as any additional growth that would be seen afterward.  The growth 
from the initial measurements taken immediately after transfer to the long-term 
 
107 
 
measurements at 28 days for the fully bonded strands are visible in Figure 5-1, with the 
average transfer length for each concrete type, girder size, and time period given. 
 
Figure 5-1: Effect of Time on Transfer Lengths 
While inconsistent in the amount of growth, it can be seen that the 7-day and 28-
day transfer lengths are almost always longer than the initial lengths.  The long-term 
measurements were then compared to the measurements taken immediately after transfer 
in order to depict the percentage of growth in the transfer length from the lengths taken 
after release.  A breakdown of the growth each type of concrete and girder size 
experienced is detailed in Table 5-3.  The values shown are the results of the ratio of the 
long-term transfer length compared to the initial transfer length. 
  
0
5
10
15
20
SCC 54-A SCC 54-B SCC 72-A SCC 72-B CVC 54-A CVC 54-B CVC 72-A CVC 72-B
Tr
an
sfe
r L
en
gth
 (in
.)
Concrete Type and Girder Size
Transfer
7-Day
28-Day
 
108 
 
Table 5-3: Time Effects on Transfer Length of Bulb-Tee Girders 
Fully Bonded Debonded 
Concrete Size 
lt,7-days/ 
lt,initial 
lt,28-days/ 
lt,initial 
lt,7-days/ 
lt,initial 
lt,28-days/ 
lt,initial 
SCC 54 1.07 1.08 0.88 0.90 72 1.13 1.12 1.05 1.08 
CVC 54 1.21 1.19 0.92 0.88 72 1.23 1.33 1.18 1.13 
 
As mentioned before, the trend for transfer length growth over time has shown 
that a large amount of growth occurs in the few days immediately after transfer, with 
some, but significantly less growth occurring beyond that point.  This can be seen in the 
results as significant growth occurred between the initial and seven-day measurements, 
anywhere from 7 percent to 23 percent, with minimal growth occurring after that.  The 
growth seen from 7 days to 28 days after transfer was typically just a few percent or less.  
Overall, the transfer lengths grew 18 percent from the values collected after transfer.  It 
would also appear that the transfer lengths grew more when cast in CVC than when cast 
in SCC.  This trend agrees with that found by Staton et al. (2009), who reported that the 
additional growth of the CVC compared to the SCC was attributed to time-dependent 
softening of the CVC around the strands. 
 The debonded-strand transfer lengths saw significantly less growth, and in some 
cases appeared to shorten, over the twenty-eight day time period.  Much of the growth of 
transfer lengths has been previously associated with creep and shrinkage within the 
concrete.  After transfer release, very large stresses are found in the concrete and the ends 
of the girder, with less towards the center as the self-weight of the girder counteracts the 
prestressing forces.  With this in mind, the concrete more towards the end of the girders 
 
109 
 
would experience more creep effects than that located more towards the middle of the 
girder.  Consequently, the transfer lengths of the fully bonded strands, which were 
associated with the more highly stressed concrete, saw more growth due to the creep 
effects than the transfer lengths associated with the debonded strands located ten feet 
towards the center of the beam. 
The results were also compared to previous results found by Swords (2005), Levy 
(2007), and Boehm (2008).  Each study utilized a different time period in which to 
observe the variation of the transfer length.  Swords (2005) and Boehm (2008) took strain 
measurements at multiple time intervals in order to capture the time frame in which most 
of the transfer length growth occurred.  Levy (2008), on the other hand, only took 
measurements after prestress transfer and four days after transfer, as it was assumed that 
most of the growth in the transfer lengths would occur within the shorter period.  
Consequently, there was not a uniform time after release in which each of the different 
studies took measurements. 
While comparisons can be made for the three previous phases within one day of 
the next, the first longer-term set of measurements for this study was at an age of 7 days.  
While twice as long as the time frames looked at by the other researchers, the comparison 
of the 7-day data to the 3- and 4-day data may still be enlightening.  The fact that a 
majority of the growth occurs over the first few days and then slows down dramatically 
might indicate that the seven-day results found as part of this study were only a little bit 
longer than if they had been taken at three days.  As the previous studies also examined 
several types of SCC with varying strengths, it was necessary to only consider the high-
strength SCC mixtures which corresponded to the SCC used in the bulb-tee girders tested 
 
110 
 
as part of this study.  Consequently, Table 5-4 shows the amount of growth seen in each 
study.  Overall, the PCI bulb-tee transfer lengths found in this study grew approximately 
10 percent from the time of release, which is within the range established by the previous 
studies.  Results from this and previous studies show that it is inappropriate to use the 
initial transfer lengths as an estimate of long-term transfer lengths given the significant 
growth that occurs with time. 
Table 5-4: Effect of Time on Transfer Lengths in SCC 
Study Days g1864g3047uni002Cg3039g3042g3041g3034g2879g3047g3032g3045g3040g1864
g3047uni002Cg3036g3040g3040g3032g3031g3036g3028g3047g3032
 
Prisms (Swords 2005) 3 1.04 
T-Beams (Levy 2007) 4 1.15 
AASHTO Type I (Boehm 2008) 3 1.16 
PCI BT (current study) 7 1.10 
 
5.1.4 Effect of Debonding Strands 
As there seems to be no differentiation between transfer lengths of fully bonded 
and debonded strands in the code provisions, it was logical to look at the debonded 
strands compared to the fully bonded strands.  Transfer lengths for partially debonded 
strands were not measured in girders BT-54-7S and BT-54-8C.  Table 5-5 shows the ratio 
obtained when comparing the debonded-strand transfer length (lt,debonded) to the transfer 
length of the fully bonded strands (lt,end) in the same end region of the same girder.  
Averages were then made for the four combinations of concrete type and girder size, as 
well as averages reflecting the SCC and the CVC. 
  
 
111 
 
Table 5-5: Comparison of Transfer Lengths of Fully Bonded and Debonded Strands 
Concrete Girder ID Depth (in.) lt,debond/lt,end Average 
SCC 
2S 54 0.77 0.72 
0.89 
4S 0.66 
2S 
72 
0.80 
1.06 4S 0.89 
7S 1.50 
CVC 
11C 54 1.00 0.98 
0.93 
13C 0.95 
8C 
72 
0.87 
0.88 11C 0.68 
13C 1.10 
 
On average, the transfer lengths for the debonded strands were about 10 percent 
shorter than for the corresponding fully bonded strands; however, this relationship is not 
consistent for all the girders.  One particularly interesting result was that of girder BT-72-
7S, which indicated that the debonded-strand transfer length was 50 percent longer than 
the transfer length of the fully bonded strands.  Upon closer analysis, it would appear that 
this was due to the fact that the transfer length for the fully bonded strands in this girder 
end was abnormally short (9 in.).  Based on the small set of debonded-strand transfer 
lengths measured in this study, there does not seem to be a consistent difference between 
the transfer bond behavior of fully bonded and partially debonded prestressing strands.  
There is certainly no evidence to suggest that the debonded-strand transfer lengths were 
longer than the fully bonded strands, and confirms the results found by Russell and Burns 
(1993) and Barnes, Burns, and Kreger (1999).  Consequently, there is no reason to 
 
112 
 
suggest that the code provisions be modified to contain special provisions pertaining to 
the transfer length of debonded strands for situations in which cracking is not present. 
5.1.5 Effect of Placement Sequence and Beam Orientation 
After looking at the results of the research, it appeared that the transfer length of 
one end of a girder was often significantly shorter than the corresponding transfer length 
at the opposite end of the girder, which can be seen in Table 5-1.  As an end-to-end 
comparison was the most direct comparison that could be made, since the same concrete 
mixture proportions and the same prestressing force were present throughout the girder, 
an outside factor had to be considered. 
One theory was based upon the size of the girders in question.  The smaller of the 
girders (BT-54) contained over sixteen cubic yards of concrete.  Consequently, by the 
time the second end of the girder was cast, a significant amount of time had transpired 
from the time that the first end was cast, despite the fact that concrete was almost 
continuously being added to the girder.  Another concern was that as the SCC was cast, 
the concrete was placed in the first end of the girder and began to flow to the bottom of 
the other end.  By the time it did reach the other end, the possibility of segregation had 
the potential of being higher.  As a result, a comparison was made between the transfer 
length at the second end of the girder in relation to the transfer length at the end in which 
concrete placement began.  A summary of these findings can be seen in Table 5-6, where 
?End 1? refers to the first end of the girder placed and ?End 2? refers to the final end 
placed. 
 
113 
 
Table 5-6: Comparison of Transfer Lengths Based Upon Placement Sequence 
Concrete Girder ID Depth (in.) lt,end 2/ l
t,end 1 
Average 
SCC 
2S 
54 
1.10 
0.82 
0.77 
4S 0.76 
7S 0.61 
2S 
72 
1.03 
0.73 4S 0.68 
7S 0.49 
CVC 
8C 
54 
1.48 
1.03 
1.09 
11C 0.83 
13C 0.79 
8C 
72 
1.00 
1.14 11C 0.82 
13C 1.60 
 
Given the wide range of ratios seen, from 0.49 to 1.10 for the SCC and 0.79 to 
1.60 for the CVC, it is difficult to conclude that concrete placement was the cause of the 
differences between the two different ends of the girders.  However, looking at averages, 
it does appear that the placement sequence of SCC an effect on the transfer lengths.  As 
the average transfer lengths were shorter in the end that was placed second during 
concrete placement, it was hypothesized that the effect of the concrete being placed 
laterally as the concrete flowed from the first end to the second end allowed for a more 
effective form of bond anchorage, probably in the form of mechanical resistance, than 
what was achieved in the first end of concrete placement where the SCC was dropped 
into place vertically. 
It was also considered that the effect of cutting the strand could have some impact 
on the transfer lengths.  Previous research done by Swords (2005), Levy (2007) and 
Boehm (2008) did show that a significant difference was seen between the live and dead 
 
114 
 
ends of the girder that was caused by flame cutting all the strands at one girder end, 
called the live end, before cutting the detensioned strands in the remaining locations, the 
dead ends.  This was not the case for the bulb-tee girders as the strand was cut at each 
end simultaneously, resulting in all live ends.  It was noticed, however, that on nearly all 
the ends of the girders in which a longer length of strand was exposed, at the beginning 
and end of the prestressing bed, longer transfer lengths were measured.  When the 
exterior ends of the girders (those adjacent to a longer length of unrestrained prestressing 
strand) were compared to the interior ends (those adjacent to another beam end, and thus 
a shorter length of unrestrained strand), an effect was evident.  This can be seen in the 
interior-to-exterior transfer length ratios for each beam reported in Table 5-7. 
Table 5-7: Comparison of Transfer Lengths Based Upon Beam Orientation 
Concrete Girder ID Depth (in.) lt,interior/ l
t,exterior 
Average 
SCC 
2S 
54 
1.10 
0.82 
0.77 
4S 0.76 
7S 0.61 
2S 
72 
0.97 
0.71 4S 0.68 
7S 0.49 
CVC 
8C 
54 
0.68 
0.76 
0.79 
11C 0.83 
13C 0.79 
8C 
72 
1.00 
0.82 11C 0.82 
13C 0.63 
 
Table 5-7 shows that there does seem to be a correlation between the girder ends 
that have longer lengths of exposed strand and longer transfer lengths.  When the strands 
 
115 
 
were cut at locations with longer lengths of exposed strand, the release was more violent 
as more potential energy was converted into kinetic energy.  As seen with the live ends 
from the previous studies performed by Swords (2005), Levy (2007), and Boehm (2008), 
the more dynamic the release was, the longer the transfer lengths tended to be.  The 
transfer lengths found for the interior ends of the girders studied, while still longer than 
what would have been found at dead ends, were shorter (22 percent) than those seen on 
the exterior ends of the girders, independent of the type of concrete in use.  However, it 
needs to be noted that in many instances, the exterior end of the girder was also the first 
girder end to be cast.  Without the ability to separate these two variables into significantly 
large sample sizes, it is difficult to comment on the extent that these variables had upon 
the transfer lengths. 
5.1.6 Normalization of Results 
When looking at the results presented in this chapter, as well as those collected 
previously in association with other phases of the project, there were many variables 
present.  In order to properly compare the values independent of strand size, concrete 
strength, and prestress intensity, steps were taken to ensure like quantities were available 
for the comparisons. 
From Mattock?s original equation, Equation 2-7, it can be seen that the transfer 
length was found to be proportional to both the stress in the prestressing steel, fpe, and the 
strand diameter, db.  In addition, it is inversely proportional to the average transfer bond 
stress capacity, ?tb, of the concrete (Barnes, Grove, and Burns 2003).  This can be 
summarized by Equation 5-3: 
 
116 
 
 g1864g3047 g1503 g3033g3291g3295uni016B
g3295g3277
g1856g3029 Equation 5-3 
Mitchell et al. (1993) recognized the need for a correction factor to account for 
the effects of high-strength concrete, which took the form of the inverse of the square 
root of the concrete strength at transfer.  Barnes, Burns, and Kreger (1999) justified this 
by reasoning that the average transfer bond stress capacity of the concrete is heavily 
dependent on the stiffness and tensile strength of the concrete, which are also often 
approximated as being proportional to the square root of the concrete compressive 
strength.  Consequently, by assigning a constant of proportionality, ?uni002Cuni0020Equation 5-3 can 
be modified to the following equation: 
 g1864g3047 g3404g2009 g3033g3291g3295g3493g3033g4593
g3278g3284
g1856g3029 Equation 5-4 
By solving for the proportionality constant, ?, a measured transfer length can be 
normalized in terms of concrete strength, the effective prestress after release, and the 
strand diameter.  This value can then be used to compare transfer length results by 
providing a measure which quantifies the ?relative transfer bond performance after 
normalization for the effects of prestress magnitude and concrete strength? (Boehm 2008) 
as well as strand size.  Research done by both Swords (2005) and Levy (2007) confirmed 
that the relationship shown in Equation 5-4 provided the best correlation between 
experimental results and predicted values.  Consequently, the same relationship is used in 
the following sections, and many comparisons are based upon the proportionality 
constant, ?, that corresponds to each measured transfer length.  The average ? values can 
be seen for both SCC and CVC for the transfer lengths of the fully bonded strands in 
Figure 5-2 and the debonded lengths in Figure 5-3, where the measured transfer lengths 
 
117 
 
from the bulb-tee girders are plotted versus g3033g3291g3295g3493g3033g4593
g3278g3284
g1856g3029.  The domain of the data on these 
plots is small because there is little variation in the g3033g3291g3295g3493g3033g4593
g3278g3284
g1856g3029 values for the transfer lengths 
in this study. 
 
Figure 5-2: Transfer Length as a Function of Tendon Prestress and Concrete 
Strength at Transfer of Fully Bonded Strands 
 
0
10
20
30
40
50
0 10 20 30 40 50
Tr
an
sfe
r L
en
gth
 (in
.)
(ksi0.5-in.)b
ci
pt d
f
f
'
b
ci
pt
t df
fksil
'44.0
5.0?=
 
118 
 
 
Figure 5-3: Transfer Length as a Function of Tendon Prestress and Concrete 
Strength at Transfer of Debonded Strands 
5.1.7 Effect of Concrete Strength 
While this particular study did not focus on the effects of the concrete strength, 
Swords (2005), Levy (2007), and Boehm (2008) determined in previous studies that the 
concrete strength does affect the transfer length of SCC with higher strength concretes 
producing shorter transfer lengths.  Variable concrete strengths were seen amongst the 
results of this study; however, the variation of strengths fell within a range of 1150 psi 
(from 7860 psi to 9010 psi) at transfer, a range too small to illuminate a clear sensitivity 
in the transfer length results.  However, while the range of concrete strengths in this study 
was not broad enough to justify conclusions about the effect of concrete strength on 
transfer length, it was still necessary to account for the differences in the concrete 
strength, strand size, and prestress when examining the effects of other variables.  This 
was accomplished by applying the normalizing process described previously and 
comparing ? values. 
0
10
20
30
40
50
0 10 20 30 40 50
Tr
an
sfe
r L
en
gth
 (in
.)
(ksi0.5-in.)b
ci
pt d
f
f
'
b
ci
pt
t df
fksil
'36.0
5.0?=
 
119 
 
5.1.8 Effect of Concrete Type?CVC versus SCC 
The comparison of transfer bond behavior in SCC to transfer lengths in CVC is 
the primary focus of this study.  In order to properly compare the transfer lengths as a 
function of the type of concrete employed, the transfer lengths measured at an age of 28 
days were compared.  Table 5-8 shows the averaged transfer lengths of the fully bonded 
strands for each girder, thus representing each of the twelve girders, along with the 
corresponding debonded-strand transfer lengths where applicable.  Averages based on the 
type of concrete and size of the girder are also shown. 
Table 5-8: Comparison of SCC and Conventional Mixture Transfer Length Results 
Fully Bonded Debonded 
Concrete Girder ID Depth (in.) lt Average lt lt Average lt 
(in.) (in.) (in.) (in.) (in.) (in.) 
SCC 
2S 
54 
16.25 
15.8 
15.9 
12.00 
12.8 
13.0 
4S 18.00 13.50 
7S 13.25 N/A 
2S 
72 
17.25 
15.9 
14.00 
13.2 4S 16.75 12.00 
7S 13.75 13.50 
CVC 
8C 
54 
14.25 
13.3 
13.5 
N/A 
11.3 
11.2 
11C 13.25 12.00 
13C 12.50 10.50 
8C 
72 
15.00 
13.6 
13.00 
11.2 11C 12.75 9.50 
13C 13.00 11.00 
 
As previously mentioned, given the variability of the concrete strength, the strand 
size, and the stress being anchored in the prestressing strand, the ? value for each transfer 
length was used to allow for more direct comparisons to be made between the various 
transfer zones.  Table 5-9 shows the average ? values for the transfer length of the fully 
 
120 
 
bonded strands of each girder and Table 5-10 shows the corresponding values for the 
debonded-strand transfer zones.  Consequent averages for girders of each size with 
respect to the type of concrete used, as well as the overall averages of the transfer length 
of both SCC and CVC, are given. 
Table 5-9: Comparison of SCC and Conventional Mixture Results of Fully Bonded 
Strands 
Concrete Girder ID Depth (in.) ? Average ? (ksi-0.5-in.) (ksi-0.5-in.) (ksi-0.5-in.) 
SCC 
2S 
54 
0.51 
0.50 
0.48 
4S 0.56 
7S 0.41 
2S 
72 
0.50 
0.46 4S 0.48 
7S 0.40 
CVC 
8C 
54 
0.42 
0.40 
0.40 
11C 0.39 
13C 0.39 
8C 
72 
0.44 
0.40 11C 0.37 
13C 0.39 
 
  
 
121 
 
Table 5-10: Comparison of SCC and Conventional Mixture Results of Debonded 
Strands 
Concrete Girder ID Depth (in.) ? Average ? (ksi-0.5-in.) (ksi-0.5-in.) (ksi-0.5-in.) 
SCC 
2S 
54 
0.38 
0.40 
0.39 
4S 0.42 
7S N/A 
2S 
72 
0.41 
0.38 4S 0.34 
7S 0.39 
CVC 
8C 
54 
N/A 
0.34 
0.33 
11C 0.35 
13C 0.33 
8C 
72 
0.38 
0.33 11C 0.28 
13C 0.33 
 
It is clearly apparent from the results that the transfer lengths in SCC are longer 
than those found in CVC.  For fully bonded strands, SCC was found to produce transfer 
lengths 20% longer than CVC, and 18% longer transfer lengths for debonded strands.  
The transfer lengths in the SCC were approximately 2 inches (4 strand diameters) longer. 
A second, more in depth comparison was also made.  Each transfer zone for fully 
bonded strands within an SCC girder was paired with a corresponding transfer zone for 
fully bonded strands in a CVC girder.  The pairs were assigned in such a manner that 
every variable between the two zones was accounted for.  The paired ends matched with 
respect to the girder size, strand size, orientation on the prestressing bed, placement 
order, and final placement within the bridge.  The one exception to these rules were 
girders BT-54-7S and BT-54-8C, in which the girder end that was placed first for one 
girder was paired with the end final placement end of the other girder.  However, the 
 
122 
 
exterior and interior girder end orientations were still paired because this was shown to be 
more important than the order of concrete placement.  The 28-day ? values were utilized 
for this comparison, which took into account the slight variation in concrete strength and 
prestress magnitude within each pair.  Table 5-11 displays the SCC and CVC girder ends 
that were paired, whether it was the first or final girder end to be placed, and whether the 
orientation of the girder on the prestressing bed resulted in it being an exterior or interior 
girder end.  Finally, the ratio of the SCC ? value to the CVC ? for each pair is reported, 
as well as an average for each girder size. 
Table 5-11: Paired SCC and CVC Girder Ends and Comparisons with Respect to 
Girder Depth 
Depth 
(in.) 
SCC 
End 
CVC 
End 
Start/Finish 
Placement 
Exterior/ 
Interior ?SCC/?CVC Average 
54 
2S-A 13C-B 1 E 1.13 
1.25 
2S-B 13C-A 2 I 1.57 
4S-A 11C-B 1 E 1.49 
4S-B 11C-A 2 I 1.36 
7S-A 8C-B Mixed E 1.02 
7S-B 8C-A Mixed I 0.92 
72 
2S-A 13C-B 1 E 1.07 
1.19 
2S-B 13C-A 2 I 1.66 
4S-A 11C-B 1 E 1.15 
4S-B 11C-A 2 I 1.40 
7S-A 8C-B 1 E 0.60 
7S-B 8C-A 2 I 1.23 
 
The pairs were also grouped with respect to both the order in which the ends were 
placed and whether the end was an exterior or interior end.  The results can be seen in 
Table 5-12 and Table 5-13. 
  
 
123 
 
Table 5-12: Paired SCC and CVC Girder Ends and Comparisons with Respect to 
Placement Sequence 
Start/Finish 
Placement 
SCC 
End 
CVC 
End 
Depth 
(in.) 
Exterior/
Interior ?SCC/?CVC Average 
1 2S-A 13C-B 54 E 1.13 
1.09 
1 4S-A 11C-B 54 E 1.49 
1 2S-A 13C-B 72 E 1.07 
1 4S-A 11C-B 72 E 1.15 
1 7S-A 8C-B 72 E 0.60 
2 2S-B 13C-A 54 I 1.57 
1.45 
2 4S-B 11C-A 54 I 1.36 
2 2S-B 13C-A 72 I 1.66 
2 4S-B 11C-A 72 I 1.40 
2 7S-B 8C-A 72 I 1.23 
Mixed 7S-A 8C-B 54 E 1.02 0.97 
Mixed 7S-B 8C-A 54 I 0.92 
 
 
 
Table 5-13: Paired SCC and CVC Girder Ends and Comparisons with Interior and 
Exterior Girder Ends 
Exterior/
Interior 
SCC 
End 
CVC 
End 
Start/Finish 
Placement 
Depth 
(in.) ?SCC/?CVC Average 
E 2S-A 13C-B 1 54 1.13 
1.08 
E 4S-A 11C-B 1 54 1.49 
E 2S-A 13C-B 1 72 1.07 
E 4S-A 11C-B 1 72 1.15 
E 7S-A 8C-B 1 72 0.60 
E 7S-A 8C-B Mixed 54 1.02 
I 2S-B 13C-A 2 54 1.57 
1.36 
I 4S-B 11C-A 2 54 1.36 
I 2S-B 13C-A 2 72 1.66 
I 4S-B 11C-A 2 72 1.40 
I 7S-B 8C-A 2 72 1.23 
I 7S-B 8C-A Mixed 54 0.92 
 
 
124 
 
All three tables verify that the SCC transfer lengths are usually longer than the 
corresponding CVC transfer lengths.  However, it is possible to see that not only does 
SCC produce longer transfer lengths, but the effect is more pronounced when coupled 
with the effect of the concrete placement sequence or the girder orientation on the 
prestressing bed.  As mentioned previously, it is difficult to separate the effects of the 
placement sequence from the girder orientation as the two are coupled in ten of the 
twelve girders. 
Girgis and Tuan (2005) speculated that the additional length of SCC transfer 
lengths is due to the presence of VMA, which is one of the admixtures included in the 
SCC mixtures to produce its characteristic properties.  While they cite the VMA as being 
the only varying factor between the tests performed on the SCC specimens and the CVC 
specimens, there were several other variable factors that could have contributed to the 
differences seen. 
Comparisons of the results of this study were also made with the results from the 
previous studies.  In each case, transfer lengths for SCC mixtures including less than 30 
percent GGBF slag, the only type of SCC used in conjunction with the bulb-tee girders in 
this study, were normalized with respect to the conventional mixture associated with each 
particular study, with all studies being considered at seven days.  The one exception was 
the results from Levy?s (2007) study in which case the values were taken at four days.  
The averaged results can be seen in Table 5-14. 
  
 
125 
 
Table 5-14: Comparison of Normalized ? Values 
Study g2009g3020g3004g3004g2009
g3004g3023g3004
 
Prisms (Swords 2005) 1.28 
T-Beams (Levy 2007) 1.04 
AASHTO Type I (Boehm 2008) 1.07 
BT-54 (current study) 1.25 
BT-72 (current study) 1.19 
Bulb-Tee (current study) 1.22 
 
While there is a discrepancy in how much longer the transfer lengths are in SCC 
than CVC (4 percent ?28 percent longer), it is apparent that SCC does have an effect on 
the length of the transfer lengths.  It was previously hypothesized by Boehm (2008) that 
the varying factor for the degree of elongation was dependent on the size of the 
specimens.  This could be the case as results of this study do see this trend, first with the 
bulb-tee girders as the transfer lengths were 22 percent longer in SCC than CVC 
compared to being 7 percent longer in the AASHTO Type I girders examined by Boehm 
(2008) and 4 percent longer in the T-beams studied by Levy (2007).  However, the larger 
BT-72 girders saw a smaller difference in the transfer lengths (19 percent) than those 
found in the smaller BT-54 girders (25 percent).  In addition, Swords (2005) found the 
largest difference between the SCC and the CVC, which were related to the smallest 
cross sections examined. 
5.1.9 Effect of Strand Size 
For the first time in Auburn University SCC studies, a variation in the prestressing 
strand was considered.  Two different strand sizes were used: ?-inch strand, which has a 
diameter of 0.50 in., and ?-inch ?special? strand, which has a diameter of 0.52 in., with 
 
126 
 
the ?-inch being used in the BT-54 girders and the ?-inch ?special? in the BT-72 girders.  
Previous projects only used the ?-inch ?special? prestressing strand.  Given the way both 
ACI and AASHTO phrase their provisions, it is not uncommon for transfer lengths to be 
measured in terms of the diameter of the strand.  Table 5-15 shows the fully bonded, 28-
day transfer lengths of the different girders in terms of the number of diameters seen.  
However, it is also necessary to consider the effects of the concrete strength and the 
prestress intensity, the results of which can be seen in Table 5-16, which shows the ? 
values corresponding to Table 5-15. 
Table 5-15: Transfer Lengths as a Function of Strand Diameter 
Strand 
? (in.) Concrete 
Girder 
ID 
No. of 
db 
Average 
No. of db 
0.50 
SCC 
2S 33 
32 
29 
4S 36 
7S 27 
CVC 
8C 29 
27 11C 27 
13C 25 
0.52 
SCC 
2S 33 
30 
28 
4S 32 
7S 26 
CVC 
8C 29 
26 11C 24 
13C 25 
 
 
  
 
127 
 
Table 5-16: Transfer Length ? Values as a Function of Strand Diameter 
Strand 
? (in.) Concrete 
Girder 
ID 
? Average ? 
(ksi-0.5-in.) (ksi-0.5-in.) (ksi-0.5-in.) 
0.50 
SCC 
2S 0.51 
0.50 
0.45 
4S 0.56 
7S 0.41 
CVC 
8C 0.42 
0.40 11C 0.39 
13C 0.39 
0.52 
SCC 
2S 0.50 
0.46 
0.43 
4S 0.48 
7S 0.40 
CVC 
8C 0.44 
0.40 11C 0.37 
13C 0.39 
 
As can be seen from the chart, there is no distinction in the transfer lengths 
between the two strand sizes.  If anything, the transfer lengths found with the ?-inch 
?special? strands were shorter than those found with the ?-inch strand, the opposite of 
what it was predicted to be.  However, it must also be noted that the strand size was not 
independent from the size of the girder as the larger strand was only used in the larger 
girders.  Also, the different sized strands came from different manufacturers, which might 
also have had an impact on the results. 
The results were also grouped in terms of similar concretes rather than similar 
strand diameters and can be seen in Table 5-17.  As can be seen from the table, the effect 
of the type of concrete has a much larger effect on the number of strand diameters 
required to estimate the transfer length than does the strand diameter. 
 
128 
 
Table 5-17: Transfer Lengths as a Function of Strand Diameter and Concrete Type 
Concrete Strand ? (in.) Girder ID ? Average ? (ksi-0.5-in.) (ksi-0.5-in.) (ksi-0.5-in.) 
SCC 
0.5 
2S 0.51 
0.50 
0.45 
4S 0.56 
7S 0.41 
0.52 
2S 0.50 
0.40 4S 0.48 
7S 0.40 
CVC 
0.5 
8C 0.42 
0.40 
0.40 
11C 0.39 
13C 0.39 
0.52 
8C 0.44 
0.40 11C 0.37 
13C 0.39 
 
 5.1.10 Effect of Cross-Section Size 
As mentioned, it is impossible to separate the strand diameter from the size of the 
girder.  Evidence has shown that as cross-sections become larger, transfer lengths become 
shorter (Levy 2007, Boehm 2008).  Consequently, a table comparing the ? values for the 
two different sized girders produces the same table as that shown in Table 5-16, which 
supports the trend showing that larger cross-sections produce shorter transfer lengths. 
As part of the extended study, several cross-sectional sizes were examined, with 
each study using significantly larger test specimen.  Both Swords (2005) and Levy (2007) 
tested small, simple cross sections in order to obtain a better understanding of the 
different factors contributing to the transfer length.  The members utilized included 
prisms and T-beams, respectively, and can be seen in detail in Sections 2.5.1 and 2.5.2.  It 
then became necessary to consider girder cross sections that would typically be used in 
 
129 
 
the field, resulting in the study by Boehm (2008) and the examination of AASHTO Type 
I girders.  The latest study continued the investigation by looking at the larger bulb-tee 
cross-section, as well as considering two different sized bulb-tee girders. 
 To investigate this idea further, all phases of the investigation were compared.  In 
order to make the most meaningful comparisons, only the prisms containing two 
prestressing strands from the research done by Swords (2005) were considered.  In 
addition, given the range of ages at which the concrete was sampled, a similar age was 
used from each phase of experimentation.  The transfer lengths from Swords (2005), 
Boehm (2008), and the current study were taken at seven days after release.  Given that 
the longest time period considered by Levy (2007) was four days, the corresponding 
results from this concrete age were used.  In addition, only transfer zones in SCC 
containing no more than 30 percent  GGBF slag and CVC mixtures were considered, of 
which only those adjacent to flame-cutting of strands were included.  When looking at 
the results of the AASHTO Type I study, the difference in lengths between the live-end 
and dead-end results that defined the live or dead end classification was deemed 
insignificant and all of the zones were included despite the result of the flame-cutting 
process.  Consequently, four zones considered by Swords (2005), eight zones considered 
by Levy (2007), and twelve zones considered by Boehm (2008) were compared to twelve 
fully bonded BT-54 zones and twelve fully bonded BT-72 zones obtained from this 
study.  The results can be seen in Figure 5-4. 
 
130 
 
 
Figure 5-4: Effect of Cross-Section Size on Transfer Lengths 
As can be seen from the graph, as well as the average proportionality constants 
for each specimen type, the transfer lengths became smaller as the magnitude of the cross 
section increased.  However, all of the full-scale girders tested, including the AASHTO 
Type I, the PCI BT-54, and the BT-72 girders, resulted in similar results, which can be 
seen by the grouping that occurred amongst the full-scale girders in Figure 5-4.  Further 
comparison and breakdown of the average ? values can be seen in Table 5-18 with a 
graphical comparison of the SCC and CVC ? values shown in Figure 5-5. 
Table 5-18: Summary of Normalized ? Values 
 ? Value (ksi
-0.5-in.) 
Specimen SCC CVC 
Prisms (Swords 2005) 1.03 0.78 
T-Beam (Levy 2007) 0.66 0.64 
AASHTO Type I (Boehm 2008) 0.50 0.49 
PCI BT-54 (current study) 0.49 0.41 
PCI BT-72 (current study) 0.46 0.37 
0
10
20
30
40
50
0 10 20 30 40 50
Tr
an
sfe
r L
en
gth
 (in
.)
(ksi0.5-in.)
Prisms (Swords 2005)
Beams (Levy 2007)
AASHTO (Boehm 2008)
PCI BT-54
PCI BT-72
b
ci
pt d
f
f
'
b
ci
pt
prismt df
fksil
'87.0
5.0
,
?=
b
ci
pt
beamt df
fksil
'65.0
5.0
,
?=
b
ci
pt
AASHTOt df
fksil
'50.0
5.0
,
?=
b
ci
pt
teebulbt df
fksil
'43.0
5.0
,
?
? =
 
131 
 
 
 
Figure 5-5: Normalized ? Values with Respect to Member Depth 
Each of the specimens produced a slightly smaller proportionality factor than the 
next smaller specimen.  The smaller of the bulb-tee girders produced a proportionality 
factor about 2 percent shorter than the AASHTO Type I girders in SCC, while the BT-72 
girders produced even shorter transfer lengths than the BT-54 girders (a further 6 percent 
reduction).  This was a fairly insignificant change when compared to the decrease seen 
from the small-scale SCC prism ? value of 1.03 to 0.49 for the bulb-tee girders, as well as 
the fact that a variation of 10% in these transfer lengths is almost within the limits of 
precision of the transfer-length determination process.  This confirms the statements 
made by Russell and Burns (1993) in which they conclude that larger cross sections will 
produce shorter transfer lengths than those produced in the small sample prisms that had 
typically been tested up to that point as a result of the larger mass being able to absorb 
more energy. 
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50 60 70 80
????V
alu
e (
ks
i-0.5
-in
.)
Member Depth (in.)
SCC
CVC
 
132 
 
Relooking at the information presented by Girgis and Tuan (2005), they attribute 
the presence of VMA to the longer transfer lengths measured in the SCC girders when 
compared to the CVC girders.  However, several other important variables can be seen 
between the two projects.  First, in addition to the absence of VMA, the CVC mixture 
used contained a reduced amount of HRWR admixture.  Second, the cross section used in 
conjunction with the shorter CVC transfer lengths was 50 percent taller than the one used 
with SCC.  Finally, the girders cast with SCC contained concrete that was 1000 psi 
weaker at transfer than the CVC girders.  From the results found in this thesis and 
previous works, particularly Swords (2005), Levy (2007), and Boehm (2008), both the 
larger cross section and the stronger concrete in the CVC girders examined by Girgis and 
Tuan (2005) could account for the difference in transfer lengths they saw.  Also, as part 
of this research, the amount of VMA was increased from the amount used in the BT-54 
girders to the amount used in the BT-72 girders.  Of all the trends seen, the BT-72 girders 
produced shorter transfer lengths than the BT-54 girders, the opposite of what Girgis and 
Tuan (2005) suggest would be seen due to a larger quantity of VMA.  Consequently, 
there was no evidence to suggest that the presence or amount of VMA used in an SCC 
mixture has any impact on the transfer lengths. 
5.2 Comparison of Test Data with Design Expressions 
It was necessary to re-evaluate the accuracy with which the design codes 
predicted the transfer length values and the potential for the need to adjust the current 
code provisions.  As done previously, both the ACI 318-08 and the AASHTO LRFD and 
AASHTO Standard code provisions were examined.  In addition, recommendations made 
by Levy (2007) for transfer length predictions were also considered. 
 
133 
 
5.2.1 ACI 318-08, Section 12.9 
The first expression considered was that found in Section 12.9 of ACI?s Building 
Code Requirements for Structural Concrete (ACI 318-08) in which the transfer length is 
described to be: 
 g1864g3047 g3404g4672 g3033g3291g3280g2871g2868g2868g2868g4673g1856g3029  Equation 5-5 
Equation 5-5 was used to predict the transfer lengths based upon the parameters in 
association with each girder.  A value of 165 ksi was estimated to be the effective stress 
in the prestressing steel after all loses (fpe).  While two different strand diameters were 
used, the effective prestressing was constant for this relationship.  Consequently, two 
values were obtained through the equation, with there being only a difference of 1.2 in. 
between them.  In order to consider the relationship between the measured transfer 
lengths and those predicted by Equation 5-5, a ratio was taken between the two values by 
dividing the measured transfer length by the predicted transfer length.  As the ratio 
approaches one, the more unconservative the expression becomes.  Figure 5-6 and Figure 
5-7 show the ratios of both the fully bonded and the debonded-strand transfer lengths, 
respectively, as no special provisions are made for debonded strands. 
 
134 
 
 
Figure 5-6: Comparison to ACI Expression for Fully Bonded Strands 
 
Figure 5-7: Comparison to ACI Expression for Debonded Strands 
As can be seen, Equation 5-5 is very conservative in comparison to the collected 
results.  On average, the measured values were 52% that of the predicted lengths.  The 
ratios ranged from 0.31 to 0.75, values that are well below the threshold.  The debonded-
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
l t,m
ea
su
red
l t,p
red
ict
ed
 
135 
 
strand transfer lengths were even shorter than their fully bonded counterparts as they 
were only 43% that of the predicted values.  Unlike other code provided expressions in 
use, Equation 5-5 does consider the effective stress in the strand, not just the diameter of 
the strands. 
5.2.2 AASHTO Standard and ACI 318-08 Shear Provisions 
Both the Standard Specifications for Highway Bridges (2002) by AASHTO and 
the shear provisions in Sections 11.3.4 and 11.3.5 of ACI?s Building Code Requirements 
for Structural Concrete (ACI 318-08) dictate that the transfer length be taken as: 
 g1864g3047 g3404uni0035uni0030g1856g3029 Equation 5-6 
As before, the transfer lengths were calculated based upon this expression and 
compared to the measured values via ratios, the level of conservatism being illustrated by 
Figure 5-8 and Figure 5-9. 
 
136 
 
 
Figure 5-8: Comparison to AASHTO Standard and ACI 318-08 Section 11.3.4 
Expression for Fully Bonded Strands 
 
 
Figure 5-9: Comparison to AASHTO Standard and ACI 318-08 Section 11.3.5 
Expression for Debonded Strands 
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
 
137 
 
While closer to the line of equality than Equation 5-5, and thus, technically, more 
accurate, it is still clear that employing Equation 5-6 to calculate the transfer length is still 
very conservative and did not reflect the trend of the results.  In addition, both Levy 
(2007) and Boehm (2008) found the expression to be unconservative for moderate-
strength concrete mixtures.  This was not an issue for this study as moderate-strength 
concrete was not tested, and further investigation into this trend may be warranted.  
While developed for concretes with moderate strength (Hanson and Kaar 1959), the 
expression was shown to be more than adequate and a conservative approximation for 
strength design of the transfer length in high-strength concretes, although it was 
inaccurate.   
In this comparison, the fully bonded strands averaged to be 57% of the values 
predicted by the expression.  While less conservative than Equation 5-5, Equation 5-6 is 
still a very conservative estimate for high-strength concretes.  The debonded strands were 
also compared to Equation 5-6 as Section 11.3.5 directly addresses the transfer length in 
debonded strands and declares that it too shall be taken as 50db.  As seen before, the 
expression was even more conservative for the debonded strands, as they were found to 
be 47% of the predicted values. 
5.2.3 AASHTO LRFD 
AASHTO?s LRFD Bridge Design Specifications (2010) take the most 
conservative approach for calculating the transfer length for strength design, specifying 
that the expression that should be used is: 
 g1864g3047 g3404uni0036uni0030g1856g3029 Equation 5-7 
 
138 
 
The transfer lengths were again calculated based upon Equation 5-7 for the 
girders.  Figure 5-10 and Figure 5-11, which show the comparison of the measured 
transfer lengths to the transfer lengths predicted by Equation 5-7. 
 
Figure 5-10: Comparison to AASHTO LRFD Expression for Fully Bonded Strands 
 
Figure 5-11: Comparison to AASHTO LRFD Expression for Debonded Strands 
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
 
139 
 
Not only was Equation 5-7 very conservative, but it also did not take into account 
any of the parameters that are shown to have an effect on the transfer length besides the 
strand diameter.  On average, the fully bonded strands measured to be only 48% that of 
the predicted length, with the largest ratio being 0.68, which was still more than 30% less 
than the predicted value.  The debonded strands measured an average of 60% less than 
the predicted values, and were the most conservative estimates except for those found by 
Equation 5-5. 
5.2.4 Levy (2007) 
Given the accuracy with which Equation 5-4 represented the data, Levy (2007) 
took the information she collected and determined values for the proportionality constant 
which could be used for design and strength calculations involving transfer lengths.  
From her testing, three general categories were formed based upon the properties of the 
specimen, as the properties of the member would alter the proportionality factor that 
would be needed.  First, it was determined that the method of release had an impact on 
the ? value.  A gradual release method caused shorter transfer lengths, and thus could 
have a smaller ? value.  This method of release had more impact on the transfer length 
than any of the concrete properties.  Consequently, only one ? value is given for this 
category.  For members that underwent sudden release, the concrete composition did 
have an impact on the transfer length.  For concrete that contained unlimited amounts of 
GGBF slag but more than 30%, a larger ? value was required.  A single ? value was 
assigned to all other concretes, including SCC and CVC, which underwent sudden 
release.  The specimens in this study all fell into the last category. 
 
140 
 
Finally, dependent on the type of analysis being done, two different 
proportionality constants were used.  As discussed previously, it is conservative to 
overestimate the transfer length for strength design purposes as it ?results in an 
underestimation of the flexural strength and shear strength? (Levy 2007).  Consequently, 
an upper-bound value was determined that encompassed 95% of the values collected by 
Levy (2007).  Conversely, when calculating allowable stresses in the concrete 
immediately after transfer, a shorter transfer length is conservative.  Consequently, an 
average ? value was determined.  The recommendations made by Levy (2007) to 
calculate the transfer length based on the two different analysis scenarios are detailed in 
Table 5-19.  
Table 5-19: Recommended Transfer Length Equations by Levy (2007) 
Analysis Type Transfer Length 
Strength Design g1864g3047 g3404uni0030uni002Euni0037uni0038g1863g1871g1861g2879g2868uni002Eg2873
g1858g3043g3047
g3493g1858g1314g3030g3036g1856g3029 
Allowable Stress Limits g1864g3047 g3404uni0030uni002Euni0036uni0035g1863g1871g1861g2879g2868uni002Eg2873 g1858g3043g3047g3493g1858g1314
g3030g3036
g1856g3029 
 
Applying the transfer length expression used in association with strength design 
to the parameters of the specimens tested, the results were then compared to the 
experimentally determined lengths and can be seen in Figure 5-12.  Unlike the results 
presented by Levy (2007) and Boehm (2008), the results of this study do not reflect a 
trend in relation to the predicted transfer lengths.  This may be largely due to the fact that 
a small range of concrete strength was used, whereas an expression that accounted for the 
changes in concrete strength proved very effective in the previous studies.  Despite this 
 
141 
 
observation, Levy?s (2007) equation was the only one that did account for the different 
parameters that effect transfer length, which was reflected in the fact that the equation did 
a slightly better job at predicting the trend of the data than any of the other expressions 
considered. 
 
Figure 5-12: Comparison to Levy Expression for Fully Bonded Strands 
As can be seen by the graph, the ? value determined by Levy is very conservative 
and each measured transfer length lies well within its boundaries.  While it might be 
appropriate to reduce the upper bound ? value of 0.78 ksi-0.5-in. slightly to a more general 
? ksi-0.5-in., the limited scope of this study could not account for effects that could result 
in relation to variations in concrete strength or other parameters not examined here that 
were considered by Levy (2007).  In addition, as the equation still produces a 
conservative estimation for use in strength design, a change in the equation is not 
warranted.  Ultimately, Levy?s (2007) equation represents a conservative approximation 
for transfer lengths for strength design. 
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
 
142 
 
In research presented by Boehm (2008), there was concern that the expression 
may not adequately represent the transfer lengths in high-strength concrete to a 
satisfactory degree.  However, given that this study only considered high-strength 
concrete, it can be concluded that this is not an issue.  Figure 5-12 depicts the level of 
conservatism of the expression established by Levy (2007).  It can be seen that the 
expression is very conservative for the given set of results as the largest ratio was 0.82 
with an average of 0.56, and the smallest ratio being 0.33. 
As debonded strands were never specifically addressed in the code provisions, 
Levy?s (2007) expression was also applied to the debonded-strand transfer length values.  
Figure 5-13 shows how the expression is even more conservative for the debonded 
strands than for the fully bonded strands. 
 
Figure 5-13: Comparison to Levy Expression for Debonded Strands 
In situations in which the allowable stresses are being determined, it is 
appropriate to use an average value for ? rather than an upper bound.  Levy (2007) 
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
BT-54 SCC BT-72 SCC BT-54 CVC BT-72 CVC
l t,m
ea
su
red
l t,p
red
ict
ed
 
143 
 
specified that the average should be 0.65 ksi-0.5-in as seen in Table 5-19, and corresponds 
with Figure 5-4.  However, this value is still an overestimate, not an average of the full-
scale girders.  As the AASHTO Type I girders are the smallest girders that may be used 
in practice by ALDOT and the bulb-tee girders are the largest, an average value based 
upon these values is logical.  As seen in Table 5-18, the ? values range from 0.50 ksi-0.5-
in to 0.41 ksi-0.5-in.  As the AASHTO Type I girders produced the longest transfer 
lengths, an appropriate ? value that is more reflective of full-scale girders for use in 
calculating the allowable stresses in a girder is ? ksi-0.5-in.  Consequently, Equation 5-8 
exhibits the modified equation. 
 g1864g3047 g3404 g2869g2870g1863g1871g1861g2879g2868uni002Eg2873 g3033g3291g3295
g3495g3033g4594g3278g3284
g1856g3029 Equation 5-8 
 
5.2.5 Summary of Code Comparisons 
The information presented in Section 5.2.1 through Section 5.2.4 is summarized 
in the following table: 
  
 
144 
 
Table 5-20: Summary of Code Provision Comparison 
  lt,measured/lt,predicted 
  Fully Bonded Debonded 
Source Equation Range Average Range Average 
ACI 318-08 
(12.9) g4678
g1858g3043g3032
uni0033uni0030uni0030uni0030g4679g1856g3029 0.31-0.75 0.52 0.33-0.49 0.43 
ACI 318-08 
(11.3) & 
AASHTO 
Standard 
uni0035uni0030g1856g3029 0.34-0.82 0.57 0.36-0.54 0.47 
AASHTO 
LRFD uni0036uni0030g1856g3029 0.29-0.68 0.48 0.30-0.45 0.39 
Levy uni0030uni002Euni0037uni0038g1863g1871g1861g2879g2868uni002Eg2873 g1858g3043g3047g3493g1858g1314
g3030g3036
g1856g3029 0.33-0.82 0.56 0.36-0.54 0.46 
 
 
 
145 
 
 
Chapter 6 Summary and Conclusions 
6.1 Summary
While the use of SCC is not widespread, it continues to gain popularity as its 
advantages for use in construction are continually recognized due to its ability to flow 
around and through reinforcement without the use of vibration.  Consequently, a 
movement to better understand its structural behavior is underway as multiple entities 
across the United States work to perform the research necessary to allow its 
implementation on a broad scale.  In doing so, the precast/prestressed industry would be 
able to take advantage of the many benefits of using SCC, including reduced labor costs, 
increased worker safety, increased productivity, and improved product aesthetics. 
As part of this movement, the Auburn University Highway Research Center 
performed this study on precast/prestressed bridge girders cast with SCC in conjunction 
with the previous phases for the investigation sponsored by the Alabama Department of 
Transportation.  The three phases previously completed included an in-depth evaluation 
of bond behavior between prestressing strand and SCC in regards to transfer length, 
development length, and flexural behavior.  Complete and thorough discussions 
regarding the results and conclusions of these phases were reported by Swords (2005), 
Levy (2007), and Boehm (2008).  This phase of the investigation focused on results 
 
146 
 
obtained from actual bridge girders, which can later be associated with the bridge?s 
overall structural performance. 
The scope of this investigation was to examine the transfer lengths found in 
twelve of the twenty-eight precast/prestressed girders cast for the SR 22 bridge over 
Hillabee Creek in Tallapoosa County, Alabama.  Of these twelve girders, three BT-54 
girders and three BT-72 girders were cast with SCC, as well as three BT-54 girders and 
three BT-72 girders which were cast with CVC.  All of the girders contained Grade 270, 
seven-wire, low-relaxation prestressing strand, with ?-inch strand being used in the BT-
54 girders and ?-inch ?special? strand being used in the larger BT-72 girders.  The 
girders were then cast at Hanson Pipe & Prestress Plant in Pelham, Alabama.  Production 
began September 21, 2010 and concluded October 28, 2010 and incorporated the cast-in-
place transfer length testing apparatus created specifically for this project.   
Once cast, surface compressive strain measurements were taken for each girder 
before transfer and after transfer, as well as seven days and twenty-eight days after 
transfer.  Ten of the twelve girders contained three transfer zones, with one transfer 
length for the fully bonded strands located at each end of the girder, as well as a single 
debonded-strand transfer length that was measure at the mark end of each girder.  Two of 
the girders only contained two transfer zones, one fully bonded zone at each end.  The 
concrete compressive strain measurements were than analyzed according to the 95% 
AMS method and transfer lengths were determined for each transfer zone.  These results 
were then looked at in light of the type of concrete used, the effects of time, the effect of 
cross-section size, concrete strength, and with consideration of the plant casting process 
and girder orientation.  When appropriate, the results of this phase of testing was also 
 
147 
 
compared to the results found by Swords (2005), Levy (2007), and Boehm (2008) to 
create a more comprehensive understanding of the bond behavior in SCC.  Finally, these 
results were also compared to current code provisions set forth by both ACI and 
AASHTO, as well as recommendations made by Levy (2007) for appropriate predictive 
expressions. 
6.2 Conclusions 
The following conclusions concerning the transfer lengths found in SCC were 
made based on the results seen in this study. 
? Transfer lengths continue to grow for weeks after the release of the 
prestressing force.  Significant growth occurs between the initial and 
seven-day measurements with minimal growth occurring over the weeks 
that follow. 
? Trustworthy estimates of long-term transfer lengths cannot be determined 
based solely on measurements of initial transfer length, because transfer 
lengths increased 18% on average over the course of twenty-eight days 
after prestress release. 
? Transfer lengths experienced more growth when cast in CVC compared to 
SCC. 
? Transfer lengths of partially debonded strands grew less over time when 
compared to transfer lengths associated with fully bonded strands. 
? In general, the debonded-strand transfer lengths were found to be shorter 
than those of the fully bonded strands.  There is no reason to adjust the 
 
148 
 
code provisions for the transfer length of debonded strands in concrete not 
subject to cracking within the transfer zones. 
? Girders cast with SCC see larger discrepancies between transfer lengths 
found in the end of the girder in which concrete was placed first compared 
with the end placed second. 
? Transfer lengths adjacent to long lengths of exposed strand are more likely 
to be longer than the transfer lengths of girders adjacent to short lengths of 
exposed strand.  This is independent of the use of SCC or CVC. 
? While there appears to be evidence to support the influence of concrete 
placement order and girder orientation on the transfer lengths, the effects 
are interrelated and cannot be separated.  Consequently, further research 
on these topics are recommended. 
? The effect of concrete strength and variability in prestress force on the 
transfer length can efficiently be accounted for by determining ? values in 
terms of g3033g3291g3295g3493g3033g4593
g3278g3284
g1856g3029 in units of ksi-0.5-in. 
? For fully bonded and debonded strands examined in this study, SCC 
produced transfer lengths 20 percent and 18 percent longer than CVC, 
respectively. 
? There is no apparent correlation to how much longer transfer lengths are in 
SCC when compared to CVC.  However, larger cross-sections have tended 
to produce larger differences in how much longer the SCC transfer lengths 
are than CVC transfer lengths. 
 
149 
 
? There is no significant difference between transfer lengths associated with 
different strand diameters; the type of concrete (SCC or CVC) has a much 
larger effect. 
? Cross-sectional size does play a role in the transfer length as larger cross-
sections produce shorter transfer lengths.   
? The effect larger cross sections have on the transfer length is less 
pronounced among specimens of varying full-scale girders sizes than was 
seen between test prisms and the full-scale girders. 
? While additional transfer length was associated with SCC, all methods of 
predicting the transfer length were conservative enough that the additional 
length was always accounted for. 
? There is no evidence to suggest that the presence or amount of VMA used 
in an SCC mixture has any impact on the transfer lengths 
? All recommended equations used by both ACI and AASHTO are 
conservative but inaccurate for high-strength concrete.  Based upon 
previous research, it was seen that the equations were often 
unconservative for lower-strength concretes. 
? Levy?s (2007) expression for transfer length in concrete with no more than 
a 30 percent replacement of GGBF slag, 
g1864g3047 g3404uni0030uni002Euni0037uni0038g1863g1871g1861g2879g2868uni002Eg2873 g1858g3043g3047
g3493g1858g1314g3030g3036
g1856g3029 
for strength design provided the most accurate representation of the trend 
of the transfer lengths for this, and previous, studies as it accounted for 
 
150 
 
release method, concrete strength, and stress in the prestressing strand.  
While still very conservative for the lengths collected in association with 
this investigation, justification cannot be made to decrease the ? values 
dictated by Levy (2007). 
? For calculating allowable stresses, Levy?s (2007) expression was modified 
as follows: 
g1864g3047 g3404uni0031uni0032g1863g1871g1861g2879g2868uni002Eg2873 g1858g3043g3047g3493g1858g4593
g3030g3036
g1856g3029 
6.3 Recommendations for Future Study 
After completion of the study, the following recommendations can be made for 
future investigations: 
? The effects of the sequence of concrete placement and orientation of the 
girder on the prestressing beds should be further evaluated. 
? 50db was found to be unconservative for moderate-strength concrete (Levy 
2007).  This trend should be investigated further. 
? The accuracy of the modification made to Levy?s (2007) allowable 
strength transfer length relationship should be confirmed. 
 
151 
 
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ACI Committee 318. 1963. Building Code Requirements for Reinforced Concrete (318-
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155 
 
Appendix A: Notation 
 
db Diameter of prestressing strand 
f?ci Concrete strength when the prestressing steel was released 
fpe  Effective prestress force 
fpj  Jacking force 
fps  Stress which produces Mn 
fpt Stress in the prestressing steel after release 
ld Development length 
lt Transfer length 
lfb Flexural bond length 
Mn Nominal flexural strength 
? Diameter
 
156 
 
Appendix B: Special Provision 
ALABAMA DEPARTMENT OF TRANSPORTATION 
DATE:  August 10, 2009 Special Provision No. 08-0498 
 
SUBJECT: Prestressed Concrete Bridge Members (SCC and Testing), 
 Project Number BR-0204(508), Tallapoosa County. 
 
 Alabama Standard Specifications, 2008 Edition, shall be amended by replacing 
Section 513 and adding a new Section 516 as follows:
 
SECTION 513 
PRESTRESSED CONCRETE BRIDGE MEMBERS 
 
513.01 Description. 
 This Section shall cover the furnishing and installation of precast prestressed 
concrete bridge members. The required details of the members and the required details of 
the installation of the members in the structure will be shown on the plans. 
 Testing for research purposes will be performed during the production and after 
the installation of the girders. The Contractor shall provide the assistance described in 
Section 516 and the assistance required by the Engineer in performing the testing. The 
 
157 
 
Contractor shall perform the work in a manner that will accommodate the delays in the 
girder production and installation process due to the testing. 
 
513.02 Materials. 
 (a) ALDOT PROCEDURE. 
 Material requirements for the production of precast prestressed concrete bridge 
members are given in this Section and also in ALDOT-367 "Production and Inspection of 
Precast Non-Prestressed and Prestressed Concrete". Modifications to these material 
requirements for the production of precast prestressed concrete bridge members utilizing 
self-consolidating concrete (SCC) are given in Section 516.  
 (b) REINFORCING STEEL AND PRESTRESSING STEEL. 
 Reinforcing steel and prestressing steel shall meet the requirements given in 
SECTION 835. Reinforcing steel shall be Grade 60 {Grade 420}. Prestressing steel 
strands and bars shall be the type shown on the plans.  
 (c) CONCRETE MIX DESIGN FOR CONVENTIONAL CONCRETE. 
 The concrete producer shall establish the proportion of materials for each class 
and type of concrete following the guidelines given in ALDOT-170, "Method of 
Controlling Concrete Operations for Structural Portland Cement Concrete" and ALDOT-
367, with the exception that the following criteria shall be used instead of the "Master 
Proportion Table". 
 The 28-day compressive strength for prestressed concrete bridge members shall 
be 5000 psi {35 MPa} if the required compressive strength is not shown on the plans.  
 
158 
 
 The concrete producer shall submit the proposed concrete mix design to the 
Materials and Tests Engineer for approval following the requirements given in ALDOT-
170.  The distribution of the approved concrete mix design will be in accordance with the 
requirements given in ALDOT-170 and ALDOT-367.  Any changes of the materials 
and/or proportions of the mix design will require a concrete mix re-submittal. 
 The mix design shall be based on the following requirements: 
MIX DESIGN CRITERIA ALL MEMBERS EXCEPT PILES CONCRETE PILES 
Minimum Cementitious Materials Factor 
(Lbs/Yd3) {kg/m3} 550 {330} 600 {356} 
Maximum Water/Cementitious Materials Ratio 0.45 0.45 
Maximum Slump (prior to admixture)  (in) {mm} 4.0 {100} 4.0 {100} 
 The maximum total air content is 6.0 % by volume. The mix design shall be based 
on a target total air content of 4.5 %. 
 Chemical admixtures may be used to increase the slump of the concrete to a 
maximum of 9 inches {225 mm} if this is proposed in the mix design submittal and 
approved for inclusion in the  mix. The approved water to total cementitious materials 
ratio shall not be exceeded in order to increase the slump. 
 Cement for piles shall be Type II and shall be low tricalcium aluminate. If 
requested by the Contractor and approved by the Materials and Tests Engineer, Type I or 
Type III cement containing a maximum of 8 % tricalcium aluminate may be used.  
 The concrete for piles shall contain Class "F" fly ash and microsilica as 
components of the cementitious materials. The requirements for fly ash and microsilica 
are given in Section 806, Mineral Admixtures. Fly ash shall meet the requirements given 
in AASHTO M 295. Fly ash shall also meet the Supplementary Chemical Requirement 
 
159 
 
given in Table 2 of AASHTO M 295.The percentage of cement, fly ash and microsilica 
in piles shall be the percent by weight {mass} of the total cementitious materials content 
shown in the following table: 
CEMENTITIOUS CONTENT IN PILES 
Cement (Type II) 70% 
Fly Ash (Class ?F?) 20% 
Microsilica 10% 
Total Cementitious Content 100% 
 
(d) CONCRETE MIX DESIGN FOR SELF CONSOLIDATING CONCRETE 
(SCC). 
 Concrete mix design requirements for the production of precast prestressed 
concrete bridge members utilizing self-consolidating concrete (SCC) are given in Section 
516.  
 
513.03 Construction Requirements. 
(a) MANUFACTURER'S PLANT, LABORATORY AND PERSONNEL 
REQUIREMENTS. 
 The concrete bridge member manufacturing plant shall be certified by the 
Precast/Prestressed Concrete Institute (PCI) Plant Certification Program. Certification of 
the production plants shall be at least Category B4 (Prestressed Deflected Strand Bridge 
Members). The manufacturer shall submit proof of the plant certification to the Materials 
and Tests Engineer prior to the start of production. 
 The manufacturing plant shall have on site, at the time of manufacturing bridge 
components for ALDOT, at least one technician that is certified as an ALDOT Concrete 
 
160 
 
Technician. This technician shall also be certified as PCI Level I/II. The manufacturer 
shall submit proof of this certification to the Materials and Tests Engineer prior to the 
start of production and during production when required by the Engineer. 
 The manufacturer's laboratory and laboratory personnel shall be qualified in 
accordance with the requirements given in ALDOT-405, "Certification and Qualification 
Program for Concrete Technicians and Concrete Laboratories". 
 (b) SHOP DRAWINGS AND NOTIFICATION OF MANUFACTURER. 
 The Contractor shall submit shop drawings to the Bridge Engineer for approval 
prior to production. The complete details of prestressed concrete members shall be 
submitted as Shop Drawings in accordance with the requirements given in Section 
105.02. The submittal shall include the proposed tensioning and de-tensioning 
procedures. 
 Within 30 days after the award of the contract, the Contractor shall notify the 
State Materials and Tests Engineer in writing of the manufacturer's proposed fabrication 
schedule. 
 (c) CAMBER OF GIRDERS AND BRIDGE DECK SPANS. 
 The theoretical camber of girders will be shown on the plans. The camber of 
girders shall be a minimum of 1/2 inch {13 mm} at the time of shipment. The camber of 
span sections shall be a minimum of 1/4 inch {6 mm} at the time of shipment. 
 (d) SURFACE FINISH. 
 All surfaces shall have a Class 1 surface finish in accordance with the 
requirements given in Section 501.  
 
161 
 
 The outside of all exterior girders shall have a Class 2 surface finish in accordance 
with the requirements given in Section 501 if a Class 3 is not shown to be required on the 
plans. A Class 2 surface finish shall be the same finish that is applied to other portions of 
the bridge structure. The final Class 2 finish shall not be applied until after the 
completion of the construction of the bridge deck on the girders. 
 A Class 2 surface shall be applied to the final exposed surface of concrete piles if 
shown to be required on the plans. 
 The riding surface of bridge deck span sections shall be finished with either a 
wood float finish or with a broom finish done with a broom with medium to stiff bristles. 
The surface shall not vary more than 1/8 of an inch {3 mm} from a 10 foot {3 m} straight 
edge. 
 The bonding surface of bridge deck span sections (surface covered by an overlay) 
shall be raked in a transverse direction to provide a roughened surface for the application 
of the overlay. The roughened surface shall have a minimum of 1/4 inch {6 mm} ridges 
raised in the surface at the time of the initial set of the concrete. 
 Where self-consolidating concrete is used for casting the girders the Contractor 
shall submit the proposed method of providing a roughened or mechanical bonding 
surface on the tops of the girders. The proposed method shall be shown on the girder 
shop drawings submitted for approval.   
 (e) HANDLING, STORING, AND TRANSPORTING MEMBERS. 
 The Contractor shall be fully responsible for handling, storing and transporting 
prestressed concrete bridge members in a manner that will prevent damage to the 
members. 
 
162 
 
 Girders shall be handled and stored in an upright position. Lifting hooks or similar 
devices for lifting shall be placed at points close to each end of each member or at the 
locations shown on the plans. Devices shall be of sufficient strength and embedment to 
provide safe handling of the members. Blocking under units during storage and handling 
shall be placed to prevent damage. 
 Piles shall be lifted, stored, transported, and placed in the pile driving leads in a 
manner that will eliminate the possibility of damaging bending stresses, cracking and 
spalling. Piles shall be lifted by means of a suitable bridle or sling attached to the pile at 
pickup points designated on the plans. Cracked piles will be rejected and shall be 
immediately removed and replaced without additional compensation.  
 All prestressed concrete bridge members except piles shall be held at the plant for 
a minimum of 4 days after casting.  Piles shall be held at the plant for a minimum of 21 
days after casting. All prestressed concrete bridge members shall not be transported until 
the minimum 28 day compressive strength is obtained and verified by test cylinders. 
 (f) INSTALLATION OF PRESTRESSED CONCRETE MEMBERS. 
 1. DAMAGED MEMBERS. 
 Members that are damaged in any way shall be replaced or repaired without 
extra compensation.  
 2.  PRESTRESSED CONCRETE GIRDERS. 
 Prestressed girders shall be lifted by attachment at the lifting points shown on 
the shop drawings. Girders shall be supported at the bearing points shown on the plans 
when they are put into the structure.  
 
163 
 
 The Contractor shall be fully responsible for the stability of the girders during 
construction. The Contractor shall submit working drawings in accordance with the 
requirements given in Article 105.02 for temporary bracing installed to provide stability 
for the girders. 
 3. INSTALLATION OF DECK SPAN MEMBERS. 
 Deck span members that will not be covered by an overlay shall be installed 
so that the difference in the top surface of adjacent members does not exceed 1/4 of an 
inch {6 mm}. Deck members shall be replaced without extra compensation if the 
difference in the surface is not within the allowable 1/4 of an inch {6 mm} difference. 
Members not meeting the installation tolerance may be installed in other locations in the 
structure if this results in an acceptable deck surface. 
 Deck span members shall be bolted together as shown on the plans to provide 
snug tight fit. Beveled washers shall be provided if the flat washers, bolt heads and nuts 
are not in full bearing on each other after tightening. Snug tight is defined as the tightness 
that can be produced by one or two solid blows from an impact wrench or by full effort of 
a person using an ordinary 2 foot {610 mm} spud wrench. The threads of the bolts shall 
be burred to prevent removal after the members have been acceptably bolted together.  
 At the completion of the bolting together of the members, the concrete 
keyway shall be filled with an approved 4000 psi {28 MPa} compressive strength 
concrete mix. The Contractor shall obtain the approval of the mix design from the 
Materials and Tests Engineer prior to filling the keyways. The keyways shall be filled in 
accordance with the following: 
 
164 
 
 -  standard mixing of the concrete shall be completed a minimum of 45 
minutes in advance of placement; 
 -  the mix shall be retempered by remixing the concrete without additional 
water just prior to placing; 
 -  the concrete mix shall be placed in the keyway, tamped, and packed as 
necessary to insure complete filling of the joint; 
 -  the exposed surface of the joint shall be struck to the same elevation of 
the adjoining deck sections; 
 - the surface shall be given a wood float finish. 
 (g) PLACEMENT OF CRANES ON BRIDGE DECKS.  
 Cranes shall not be placed on a bridge deck unless approved by the Engineer. The 
Contractor shall submit a placement plan for review prior to placing a crane on a bridge 
deck. The placement plan shall be submitted in accordance with the requirements given 
in Section 510.  
 
513.04 Method of Measurement. 
 (a) ITEM NO. 513-A. 
 Girders will be measured per each girder of each type and length. 
 (b) ITEM NO. 513-B. 
 Each type of girder will be measured per linear foot of casting length shown on 
the approved shop drawings minus the length of elastic shortening and shrinkage. This 
will be the length recorded on the Shipping Notice (BMT-139) prepared by the 
 
165 
 
Department's Plant Inspector. A copy of BMT-139 shall be sent with the shipment of the 
girders. 
 (c) ITEMS 513-C and 513-D. 
 Concrete span sections will be measured per each type and size. 
 
513.05 Basis of Payment. 
 (a) UNIT PRICE COVERAGE. 
 1. ITEMS 513-A and 513-B. 
 Concrete girders will be paid for at the contract unit price for each type of 
girder. This price shall be full compensation for furnishing all materials, accessories, 
tools and labor necessary to manufacture and install the girders except for the additional 
costs that results from the testing of the girders for research purposes and the utilization 
of SCC. Compensation for the cost of the testing of the girders and utilizing SCC as 
described in Section 516 will be paid for under the requirements given in that Section.   
 This price shall also be full compensation for premolded bituminous filler, for 
all items cast into the concrete including metal bearing plates and studs welded to these 
plates, and for  obtaining a Class 2 surface finish on the outside of all exterior girders. 
 2. ITEMS 513-C and 513-D. 
 Concrete deck span sections will be paid for at the contract unit price for each 
type and size. This price shall be full compensation for furnishing all materials, 
accessories, tools and labor necessary to manufacture and install the span sections. 
 This price shall also be full compensation for all items cast into the concrete, 
for the tie bolts, for expansion and bearing materials, for cover concrete over fittings, for 
 
166 
 
grout and grouting, for placement of keyways, and for surface finishing. Other structural 
steel items and handrail will be covered under other items of work. 
 3. PARTIAL PAYMENT. 
 Partial payments will be made in accordance with the following schedule: 
 - Fabrication and Delivery to Approved Storage Site. (Approved storage 
sites and partial payment for stored materials are addressed in Article 
109.07); 
 - Erected and the Required Finish Applied to Girder Units or the Bolting 
Up and Casting Of Keyway on Deck Units - 100%. 
 Partial payments for members that are unacceptable because of damage, 
improper installation or any other reason will be recovered by the Department on the next 
monthly estimate or final estimate, whichever is applicable. 
 (b) PAYMENT WILL BE MADE UNDER ITEM NO.: 
 513-A   *   Pretensioned-prestressed Concrete Girders, Type  **  (SPECIALTY 
ITEM)  - per each 
 513-B  Pretensioned-prestressed Concrete Girders, Type   ** (SPECIALTY 
ITEM) - per linear foot {meter} 
 513-C  Prestressed Concrete Interior Span Sections, ____ Wide by ____ Deep by 
____ Long (SPECIALTY ITEM) - per each 
 513-D  Prestressed Concrete Exterior Span Sections, ____ Wide by ____ Deep by 
____ Long (SPECIALTY ITEM) - per each 
 * Length 
 ** Type I, II, III, etc., as per AASHTO Classification. 
 
167 
 
 
 
SECTION 516 
TESTING CONCRETE GIRDERS AND UTILIZING SELF-CONSOLIDATING 
CONCRETE 
 
516.01 Description. 
 This Section shall cover the testing of prestressed concrete girders for research 
purposes and the utilization of self consolidating concrete (SCC) for the production the 
girders where shown to be required on the plans. The requirements given in this Section 
shall modify and supplement the material, production and compensation requirements 
given in Section 513. 
 SCC is a highly flowable, non-segregating concrete utilized in the fabrication of 
prestressed bridge components. SCC is utilized to fill the formwork and encapsulate the 
reinforcing steel without, or with very minimal, applied vibratory consolidation. The 
Engineer may require a minimal amount of applied vibratory consolidation. 
 Testing for research purposes will be performed during the production and after 
the installation of the girders. The Contractor shall provide the assistance described in 
this Section and the assistance required by the Engineer in performing the testing. The 
Contractor shall perform the work in a manner that will accommodate the delays in the 
girder production and installation process due to the testing.  
 
516.02 Materials. 
 (a) ALDOT PROCEDURES. 
 
168 
 
 Material requirements for the production of precast prestressed concrete bridge 
members are given in this Section and in the following ALDOT Procedures:  
 - ALDOT 170 "Method of Controlling Concrete Operations for Structural 
Portland Cement Concrete"; 
 - ALDOT-367 "Production and Inspection of Precast Non-Prestressed and 
Prestressed Concrete"; 
 - ALDOT 441 "Prestressing Strand Pullout Test". 
 The requirements given in this Section shall govern over similar requirements 
given in the ALDOT Procedures.  
 (b) DESIGN, SUBMITTAL AND APPROVAL OF SCC MIX DESIGN. 
 The concrete producer shall establish the proportion of materials for the SCC mix 
in accordance with the guidelines given in ALDOT 170 with the exception that the mix 
design criteria given in this Section shall be followed instead of the Master Proportion 
Table. 
 The concrete producer shall submit the proposed SCC mix design to the Materials 
and Tests Engineer for approval following the guidelines given in ALDOT-170. The 
distribution of the approved concrete mix design will be in accordance with the 
requirements given in ALDOT-170 and ALDOT-367.  The producer shall submit all 
proposed changes to a previously approved mix design for reapproval. Any changes of 
the materials and/or proportions of the mix design will require a concrete mix 
re-submittal. 
 (c) CEMENTITIOUS MATERIALS FOR SCC. 
 
169 
 
 The cementitious materials for SCC shall meet the requirements given in Sections 
806 and 815. The following combinations of mineral admixtures may be substituted for a 
portion of the Portland cement that is required for the total cementitious materials content 
of the mix.  
 
MAXIMUM PERCENT OF ALLOWABLE MINERAL ADMIXTURE 
SUBSTITUTION FOR PORTLAND CEMENT (BY WEIGHT) 
Substitution 
Option 
Class C or Class F Fly 
Ash 
Ground Granulated 
Blast Furnace Slag Microsilica 
1 30 % - - 
2 - 50 % - 
3 - - 10 % 
4 20 % - 10 % 
5 20 % 30 % - 
 
 (d) CHEMICAL ADMIXTURES FOR SCC. 
 Chemical Admixtures for the production of SCC shall be selected from List II-1 
of the Department?s "Materials, Sources, and Devices with Special Acceptance 
Requirements" Manual. Refer to Subarticle 106.01(f) and ALDOT-355 concerning this 
list. 
 Approved viscosity modifying admixtures (VMA) may be used as a part of the 
chemical admixtures if they are shown in the approved mix design. 
 (e) PREPARATION OF SCC TEST SAMPLES. 
 All SCC test specimen molds, air content buckets, and unit weight buckets shall 
be filled in one continuously poured lift using a suitable container without vibration, 
rodding, or tapping.  The SCC shall be dropped from a height of 6 inches ? 2.0 inches 
 
170 
 
above the mold or container top into the center of the container until the concrete is 
slightly above the top of the mold or bucket. The SCC shall be struck off level with the 
top of the mold or bucket. 
 (f) REQUIREMENTS FOR THE DESIGN OF THE SCC MIX. 
 The design of the SCC shall be in compliance with the requirements given in the 
following table. 
 
REQUIRED DESIGN PROPERTIES OF THE SCC MIX 
Properties shall be measured from a minimum size batch of 3 cubic yards. 
Property Requirement Test 
Compressive 
Strength at 28 days 
The compressive strength shown on the plans or 
5000 psi if it is not shown.  
AASHTO T 
22 
Cementitious 
Materials Content 
Minimum 600 pounds per cubic yard of 
concrete.   
Water/Cementitious 
Materials Ratio Maximum 0.40.  
Nominal Aggregate 
Size Maximum 0.75 inches.  
Fine/Total 
Aggregate Ratio 0.45 to 0.55 by volume.  
Total Air Content 
Maximum 6.0 % by volume. The design of the 
mix shall be based on a target total air content 
of 4.5 %. 
AASHTO T 
152 
Temperature 
Freshly mixed concrete at the time of placing in 
the forms shall not be less than 50 ?F or more 
than 95 ?F. 
AASHTO T 
309 
28-Day Drying 
Shrinkage 
Maximum 0.04 % when prisms are exposed to 
drying at a concrete age of 7 days. ASTM C 157 
 
171 
 
Slump Flow1 
Minimum 25 inches, maximum 29 inches. Test 
shall be completed within 10 minutes after 
completion of mixing. 
ASTM C 
1611 
Passing Ability2 
Difference between slump flow and J-Ring 
flow 3.0 inches or less. Test shall be completed 
within 10 minutes after completion of mixing. 
ASTM C 
1621 
Visual Stability 
Index3 (VSI) 
Less than 2.0. Test shall be completed within 10 
minutes after completion of mixing. 
ASTM C 
1611 
Static Segregation 
Index 
Maximum 15.0 %. Test shall be started within 
10 minutes after completion of mixing. 
ASTM C 
1610 
Robustness Slump flow 29 inches or less. VSI less than 2.0. ASTM C 1611 
1. The Slump Flow test shall be performed using the "Filling Procedure B" in ASTM 
C 1611.  
2. The Passing Ability test shall be performed using the ?Filling Procedure B? in 
ASTM C 1621. 
3. A VSI of 1.5 is acceptable. A VSI of 1.5 corresponds to a stable SCC with a 
minimal mortar halo (< 0.25 inch), good aggregate distribution, and slight 
noticeable bleeding at the surface of the slump patty. 
 
 (g) ROBUSTNESS TESTING. 
 The freshly mixed SCC shall be robust to ensure that segregation of the mixture 
does not occur during or after placement.  
 Robustness testing shall be performed on a minimum batch size of 3 cubic yards 
of mix. No water may be withheld from the minimum batch size of 3 cubic yards. A 
representative sample shall be taken and the unit weight shall be determined in 
accordance with the requirements given in AASHTO T 121. After completion of the unit 
weight test, a 2 cubic foot sample shall be taken for further testing. The concrete weight 
 
172 
 
of the 2 cubic foot sample shall be calculated from the unit weight test results. The 2 
cubic foot sample shall be added to a buttered rotating-drum mixer and additional water 
shall be added to the mixture. The additional water shall be equal to 2 % of the total fine 
aggregate saturated-surface dry weight in the 2 cubic foot sample. The concrete sample 
with the added water shall be mixed for 1 minute and then the tests for mixture 
robustness (Slump Flow and Visual Stability Index) shall be performed.  Both the Slump 
Flow and VSI tests shall be completed within 5 minutes after completion of mixing with 
additional water.  A 4 inch x 6 inch digital color photograph (printed with a minimum 
resolution of 300 dpi) of the slump flow patty obtained for the robustness test shall be 
submitted with the request for the mixture approval. 
 The mixture is acceptable if its robustness test results are a slump flow of 29 
inches or less and a VSI less than 2.0. 
 (h) TESTING REQUIREMENTS FOR THE SCC DURING GIRDER 
PRODUCTION. 
 SCC shall be in compliance with the requirements given in the following table 
during the production of the girders. All of the tests shown in this table shall be 
considered as "one set" of tests. At least one set of tests shall be performed for every 50 
cubic yards, or fraction thereof, of concrete placed. 
  
 
173 
 
REQUIRED PROPERTIES OF THE SCC MIX DURING GIRDER 
PRODUCTION 
Property Requirement Test 
Compressive 
Strength at 28 days 
The compressive strength shown on the plans or 
5000 psi if it is not shown.  
AASHTO T 
22 
Temperature 
Freshly mixed concrete at the time of placing in 
the forms shall not be less than 50 ?F or more 
than 95 ?F. 
AASHTO T 
309 
Total Air Content Maximum 6.0 % by volume.  AASHTO T 152 
Slump Flow1 Minimum 25 inches, maximum 29 inches. ASTM C 1611 
Visual Stability 
Index2 (VSI) Less than 2.0. 
ASTM C 
1611 
1. The Slump Flow test shall be performed using the "Filling Procedure B" in ASTM 
C 1611. 
2. A VSI of 1.5 is acceptable. A VSI of 1.5 corresponds to a stable SCC with a 
minimal mortar halo (< 0.25 inch), good aggregate distribution, and slight 
noticeable bleeding at the surface of the slump patty. 
 
 The QC technician of the prestressed concrete producer shall be responsible for 
the performance of all concrete sampling and testing during girder production. The 
Department's QA technician will determine and document the point of sampling and 
testing and the schedule of testing for each line of production.  
 Sampling and testing shall be performed as close as possible to the casting bed. 
Fresh concrete will be accepted during concrete placement based on all of the tests shown 
in the preceding table except for compressive strength. Acceptance of a girder will be 
based on the 28-day compressive strength test results. 
 
174 
 
 All tested SCC batches shall meet the 28-day compressive strength, temperature, 
total air content, and slump flow requirements outlined in the preceding table.  Action to 
correct the lack of mixture stability is required immediately following an individual 
failing VSI test. The batch of SCC immediately following a batch that failed the VSI 
requirement shall be tested for all of the tests shown in the preceding table. If the VSI 
requirement is not met on any two consecutive batches of SCC, then the second batch of 
SCC will be rejected. After the rejection of a batch of SCC that did not meet the VSI 
requirement, testing of all subsequent batches of SCC shall continue until two 
consecutive batches of SCC meet the VSI requirement.  A 4 inch x 6 inch digital color 
photograph (printed with a minimum resolution of 300 dpi) of the slump flow patty of the 
SCC that did not meet the VSI requirement shall be kept for documentation purposes. 
 (i) AGGREGATE MOISTURE CONTROL. 
 If moisture meters are not used, the free moisture content of aggregates shall be 
measured within one hour prior to each day?s batching operations, at 2 hour intervals 
during continuous batching operations, and at any time a change in moisture content 
becomes apparent. 
 
516.03 Fabrication and Testing. 
 The Contractor shall have the prestressed concrete girders fabricated by Hanson 
Prestressed Concrete in Pelham Alabama. The Contractor and Hanson shall allow testing 
for research purposes to be performed during the production of the girders made with 
conventional concrete and the girders made from SCC.  
 
175 
 
 The Contractor and Hanson Prestressed Concrete shall provide access for the 
installation of instrumentation and recording of measurements. They shall also alter the 
schedule of production to allow the installation of instrumentation and recording of 
measurements. 
 The Contractor and Hanson Prestressed Concrete shall provide full cooperation as 
directed by the Engineer to insure that the testing is done in a manner that will allow the 
researchers to make sufficient measurements. 
 The following are anticipated delays that will be necessary to facilitate the 
research-related testing: 
 -Up to one hour at the casting bed between installation of girder reinforcement 
and placement of side forms; 
 - Up to three hours at the casting bed between the removal of side forms and 
strand detensioning; 
 - Up to one hour at the casting bed between completion of detensioning and 
removal of girders; 
 - One day for measurement of camber after girder erection and prior to 
placement of deck forms; 
 - One day for installation of instruments prior to casting of bridge deck; 
 - Four hours for installation of instruments prior to casting of barrier rails; 
 - Two days for load testing after completion of bridge construction. 
 Girders shall be stored in such manner as to facilitate measurements of camber 
and strain. 
 
176 
 
 The Contractor shall notify the Engineer at least 7 calendar days prior to shipping 
any girder to the project site. The Engineer will inform the researchers of this delivery 
schedule to allow them the time to prepare for testing. 
 Instruments, sensors, or associated cables shall not be disturbed without prior 
written approval of the Engineer. The Engineer will be advised by the researchers if these 
devices can be disturbed by the Contractor. 
 (b) TIME ALLOWED FOR THE PLACEMENT OF THE SCC. 
 SCC delivery shall be timed so that consecutive lifts will combine completely 
without creating segregation, visible pour lines, or cold joints.  Additional loads of SCC 
shall be placed within 15 minutes from the previous load.  An SCC load outside the 15 
minutes margin may be placed on top of a previous load if the ALDOT QA inspector 
authorizes it and if required, minimal vibration is applied to the previous load. 
 (c) DISCHARGE OF THE SCC INTO FORMS. 
 SCC shall be placed from one point only and be allowed to flow sideways.  SCC 
may be also pumped from the bottom upward so as not to encapsulate air.  Simultaneous 
opposing flows of SCC shall not be done. 
 (d) SEALING FORMS TO PREVENT LEAKAGE. 
 Sealing of form joints and bulkheads prior to placement of SCC is required.  Paste 
leakage from forms and bulkheads may cause honeycombed areas.  Any area where paste 
leakage has occurred shall be assessed for possible repairs in accordance with the 
requirements given in Section 2, Article 10 of ALDOT-367. 
 (e) ALLOWABLE MINIMAL VIBRATION. 
 
177 
 
 Freshly placed SCC shall not be vibrated.  If additional loads of SCC are placed 
over SCC that was placed more than 15 minutes earlier, then minimal vibration may be 
applied to the surface of the already placed SCC to improve mixing between the different 
loads of SCC. 
 
516.04 Method of Measurement. 
 The cost of the delays for testing the concrete girders will be measured as a lump 
sum unit. The utilization of SCC for the fabrication of the girders will be measured as a 
lump sum unit.  
 
516.05 Basis of Payment. 
 (a) UNIT PRICE COVERAGE. 
 Concrete girders will be paid for at the contract unit price for each type of girder 
in accordance with the requirements given in Section 513.  
 Payment for the cost of the delays for testing of the girders and the utilization of 
SCC for fabricating the girders shall be full compensation for all costs attributable to the 
testing and the utilization of SCC that are in excess of the costs of fabricating and 
installing prestressed concrete girders with conventional concrete. The price for the 
testing of the girders and utilizing SCC shall be full compensation for furnishing all 
materials, accessories, tools and labor necessary to manufacture, install, and facilitate the 
testing of the girders and strands (strand pullout) that are in excess of the costs of girder 
fabrication and installation utilizing the requirements given in Section 513 without SCC. 
 
 
178 
 
 (b) PAYMENT WILL BE MADE UNDER ITEM NO.: 
 516-A  Testing Concrete Girders ? per lump sum. 
 516-B  Utilization of Self-Consolidating Concrete ? per lump sum. 
 
 
179 
 
Appendix C: Moustafa/Logan Pullout Testing Procedure and Results 
 
Alabama Department of Transportation 
Auburn University Highway Research Center 
Tests Performed September 14, 2010 
 
Strand Preparation Procedure 
1. Ten strand samples were taken from a roll of Strand-Tech Martin ?-inch 
strand used in the PCI 54  bulb-tee girders constructed for the ALDOT SR 22 
Hillabee Creek Bridge/Auburn University SCC research study. Samples were 
saw-cut to 34 in. lengths, and projections from the saw-cutting were removed. 
Strand samples were straightened by hand as needed. 
2. Ten strand samples were taken from a roll of American Spring Wire ?-inch 
?special? strand used in PCI 72? bulb-tee girders constructed for the ALDOT 
SR 22 Hillabee Creek Bridge/Auburn University SCC research study. 
Samples were saw-cut to 34 in. lengths, and projections from the saw-cutting 
were removed. Strand samples were straightened by hand as needed. 
3. The strand samples were clean and free of rust. 
 
  
 
180 
 
Block Casting Procedure 
1. Details of the test block geometry and reinforcement are shown in the 
Appendix. 
2. Test block forms were set up, and the reinforcement cage was installed and 
securely positioned. 
3. The strand samples were then tied securely in place in accordance with the 
layout shown in Appendix. 
4. After the strand locations and tying procedure were checked and approved, 
concrete placement began at 12:05 p.m. on September 13, 2010. 
5. Concrete mixture proportions are given in Table 1. The concrete had a slump 
of 2 ? in. and an air content of 3.9 percent.  
6. The concrete was vibrated well using an internal vibrator. 
7. The top surface was smoothed using a one-pass trowel finish. No strand 
samples were moved after the vibration ceased. 
8. Support racks were placed over the test blocks to keep the curing covers from 
coming in contact with the tips of the strand samples. Curing compound 
(Conspec Aquafilm) was sprayed on the tops of the blocks to prevent 
shrinkage cracks from occurring in the top surface. 
9. Pullout block and test cylinders were tarp-cured together. Curing was not 
accelerated. 
 
 
181 
 
Table B-1: Concrete mixture proportions 
Materials Quantity per cubic yard 
Cement (Type III) 655 lbs 
Concrete Sand (Red Bluff) 1230 lbs (SSD) 
#78 Crushed Limestone 2010 lbs (SSD) 
Normal-Range Water Reducing Admixture 0 oz 
Air-Entraining Admixture 0 oz 
High-Range Water Reducing Admixture 0 oz 
Water 235 lbs 
Water/Cement Ratio 0.43 
 
Pullout Testing Procedure 
1. Pullout testing was performed on September 14, 2010. 
2. The average concrete compressive strength measured from tests of four tarp-
cured, 6 in. x 12 in. cylinders during the pullout testing period was 4030 psi. 
3. The hydraulic jack was a Hercules jack typically used for single-strand 
stressing in long-line pretensioning operations. 
4. The bridging device was slipped over each strand to be tested and placed 
against the concrete surface.  The strand chuck was slipped over the strand to 
the top of the bridge and light pressure is applied to the jack to seat the jaws of 
the chuck into the strand. 
5. The jacking load was applied in a single increasing application of load at the 
rate of approximately 20 kips per minute until the maximum load was 
reached. 
 
 
182 
 
Results 
The following data are reported in Table B-2 for the ?-inch strand and Table B-3 for the 
?-inch ?special? strand.  Each table contains the following information for each strand 
sample: 
? Maximum pullout force capacity (Pmax) 
? Approximate load at first noticeable movement (Pmove) 
? Approximate distance the strand pulled out at maximum load (?Pmax) 
? General description of failure 
 
Table B-2: Pullout Test Results for STD ?-inch Strand 
Strand 
ID 
Pmax 
(kips) 
Pmove 
(kips) 
DPmax 
(in.) 
Failure 
Description 
1 36.0 15.0 2.0 Pullout 
2 35.0 15.0 1.8 Pullout 
3 34.0 15.0 2.3 Pullout 
4 40.0 15.0 2.0 Pullout 
5 37.0 17.0 2.0 Pullout 
6 37.0 15.0 2.0 Pullout 
7 33.5 13.0 2.3 Pullout 
8 33.5 18.0 2.0 Pullout 
9 47.5 16.0 1.5 Pullout 
10 41.5 16.0 1.5 7-wire rupture 
 
  
 
183 
 
The average maximum load for this group of 10 strand samples was 37.5 kips. 
Values ranged from 33.5 to 47.5 kips with a standard deviation of 4.4 kips (coefficient of 
variation = 11.8 percent).  While these results would typically indicate inadequate results, 
it was determined that Strand #9 had an unusually strong bond, and thus could be 
discarded from the analysis.  Consequently, the maximum values ranged from 33.5 to 
41.5 kips with a standard deviation of 2.8 kips and a coefficient of variation equal to 7.8 
percent.  Peak load generally corresponded to a pullout-type failure at pullout distances 
ranging from 1.5 to 2.3 in. 
 
Table B-3: Pullout Test Results for ASW ?-inch ?special? Strand 
Strand 
ID 
Pmax 
(kips) 
Pmove 
(kips) 
DPmax 
(in.) 
Failure 
Description 
1 40.5 NA 2.0 Pullout 
2 40.5 25.0 2.3 6-wire break 
3 39.0 24.0 1.5 1-wire break 
4 40.5 22.0 2.8 Pullout 
5 40.5 22.0 1.8 Pullout 
6 37.0 23.0 2.3 Pullout 
7 37.5 26.0 1.5 Pullout 
8 31.5 20.0 2.0 Pullout 
9 31.0 19.0 1.8 Pullout 
10 37.5 23.0 2.0 Pullout 
 
The average maximum load for this group of 10 strand samples was 37.6 kips. Values 
ranged from 31.0 to 40.5 kips with a standard deviation of 3.6 kips (coefficient of 
 
184 
 
variation = 9.6 percent). Peak load generally corresponded to a pullout-type failure at 
pullout distances ranging from 1.5 to 2.8 in. 
 
Discussion 
Based on ?excellent transfer/development length performance?, Logan (1997) 
recommends the following conditions for acceptable pullout capacity of standard ?-in. 
7-wire strand: 
? Average Pmax (six samples) of at least 36 kips 
? Coefficient of variation not exceeding 10 percent 
 
The pullout tests on which these recommendations are based were performed in a block 
with a concrete compressive strength of 4230 psi (Logan 1997). 
Assuming an equivalent average bond stress at failure for different size strands, the 
corresponding limiting Pmax value for ?-in. ?special? strand is 37? kips. The 10-sample 
average Pmax value from the tests reported here exceeds their corresponding value, and 
the coefficient of variation is within the recommended 10 percent limit. 
 
Reference 
Logan, Donald R. 1997. Acceptance criteria for bond quality of strand for pretensioned 
prestressed concrete applications. PCI Journal 42 (2): 52?90. 
  
 
185 
 
APPENDIX 
PULLOUT TEST BLOCK DETAILS 
 
 
 
 
2?-0? 
6? 6? 12? 
18? 3? 3? 
2?-0? 18? 
4? 5? 
3? 
16? 
TIE DIMENSIONS 
TIES 
14? 
EXTENSION 
2? TUBE 
MOUSTAFA PULL-OUT BLOCK ELEVATION 
# 3 
 
186 
 
 
 
 
4?-0? 
4? 1?-4? 1?-4? 4? 8? # 3 
SPACING 
# 4 LONGITUDINAL # 3 TIES 
MOUSTAFA PULL-OUT BLOCK ELEVATION 
 
187 
 
 
 
7 ?? 
6? 5? 
1? 
2? BOND BREAKER TUBE 
18? EMBEDMENT 
STRAND 
1? x 4? x 7 ??                
PLATE W/ 9/16? DIA. HOLE 
2 ?? x 2 ?? ANGLE 
TEST BRIDGING DEVICE 
4 SP @  8? 8? 8? 
6? 
6? 
12? 
TEST STRAND 
PLAN VIEW WITH STRAND NUMBERS 
1 2 3 4 5 
10 9 8 7 6 
 
188 
 
Appendix D: Fully Bonded Compressive Strain Profiles 
 
 
 
Figure D-1: 54-2S-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=15.0 in.
lt,7=15.5 in.
lt,28=15.5 in.
 
189 
 
 
Figure D-2: 54-2S-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-3: 54-4S-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=15.5 in.
lt,7=17.5 in.
lt,28=17.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=20.0 in.
lt,7=19.0 in.
lt,28=20.5 in.
 
190 
 
 
Figure D-4: 54-4S-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-5: 54-7S-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=14.0 in.
lt,7=15.0 in.
lt,28=15.5 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=14.0 in.
lt,7=16.0 in.
lt,28=16.5 in.
 
191 
 
 
Figure D-6: 54-7S-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-7: 54-8C-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=9.5 in.
lt,7=10.5 in.
lt,28=10.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=9.0 in.
lt,7=12.0 in.
lt,28=11.5 in.
 
192 
 
 
Figure D-8: 54-8C-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-9: 54-11C-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=15.0 in.
lt,7=19.0 in.
lt,28=17.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=10.0 in.
lt,7=10.5 in.
lt,28=12.0 in.
 
193 
 
 
Figure D-10: 54-11C-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-11: 54-13C-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=12.5 in.
lt,7=13.5 in.
lt,28=14.5 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=9.0 in.
lt,7=12.0 in.
lt,28=11.0 in.
 
194 
 
 
Figure D-12: 54-13C-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-13: 72-2S-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=12.0 in.
lt,7=14.5 in.
lt,28=14.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=16.0 in.
lt,7=17.5 in.
lt,28=17.5 in.
 
195 
 
 
Figure D-14: 72-2S-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-15: 72-4S-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=14.5 in.
lt,7=19.0 in.
lt,28=17.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=9.5 in.
lt,7=12.0 in.
lt,28=13.5 in.
 
196 
 
 
Figure D-16: 72-4S-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-17: 72-7S-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=18.0 in.
lt,7=19.0 in.
lt,28=20.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=9.0 in.
lt,7=9.5 in.
lt,28=9.0 in.
 
197 
 
 
Figure D-18: 72-7S-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-19: 72-8C-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=20.0 in.
lt,7=19.5 in.
lt,28=18.5 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=11.0 in.
lt,7=13.0 in.
lt,28=15.0 in.
 
198 
 
 
Figure D-20: 72-8C-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-21: 72-11C-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=11.0 in.
lt,7=13.5 in.
lt,28=15.0 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMSlt,i=10.5 in.
lt,7=13.0 in.
lt,28=14.0 in.
 
199 
 
 
Figure D-22: 72-11C-B-F Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure D-23: 72-13C-A-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=9.0 in.
lt,7=11.5 in.
lt,28=11.5 in.
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=7.5 in.
lt,7=9.0 in.
lt,28=10.0 in.
 
200 
 
 
Figure D-24: 72-13C-B-F Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60 70
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=12.5 in.
lt,7=16.0 in.
lt,28=16.0 in.
 
201 
 
Appendix E: Debonded Strand Compressive Strain Profiles 
 
 
Figure E-1: 54-2S-A-D Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=14.5 in.
lt,7=11.5 in.
lt,28=12.0 in.
 
202 
 
 
Figure E-2: 54-4S-A-D Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure E-3: 54-11C-A-D Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 175
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=14.0 in.
lt,7=13.5 in.
lt,28=13.5 in.
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=13.0 in.
lt,7=12.0 in.
lt,28=12.0 in.
 
203 
 
 
Figure E-4: 54-13C-A-D Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure E-5: 72-2S-A-D Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=12.5 in.
lt,7=11.5 in.
lt,28=10.5 in.
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=11.5 in.
lt,7=13.5 in.
lt,28=14.0 in.
 
204 
 
 
Figure E-6: 72-4S-A-D Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure E-7: 72-7S-A-D Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,7=11.5 in.
lt,28=12.0 in.
lt,i=11.0 in.
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=14.5 in.
lt,7=13.5 in.
lt,28=13.5 in.
 
205 
 
 
Figure E-8: 72-8C-A-D Measured Initial and Long-Term Strain Profiles 
 
 
 
Figure E-9: 72-11C-A-D Measured Initial and Long-Term Strain Profiles 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=11.5 in.
lt,7=12.0 in.
lt,28=13.0 in.
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=7.0 in.
lt,7=9.5 in.
lt,28=9.5 in.
 
206 
 
 
Figure E-10: 72-13C-A-D Measured Initial and Long-Term Strain Profiles 
 
0
200
400
600
800
1000
1200
1400
100 110 120 130 140 150 160 170 180
Su
rfa
ce 
Co
mp
res
siv
e S
tra
in 
(x1
0-6
)
Distance from End of Specimen (in.)
At Prestress Transfer
7 Days after Transfer
28 Days after Transfer
95% AMS
lt,i=12.0 in.
lt,7=13.5 in.
lt,28=11.0 in.