END ZONE DESIGN FOR ALABAMA DEEP PRESTRESSED GIRDERS by DAVID ISAAC ...

189 Pages·2016·10.83 MB·English

END ZONE DESIGN FOR ALABAMA
DEEP PRESTRESSED GIRDERS

by

DAVID ISAAC BURKHALTER

SRIRAM AALETI, COMMITTEE CO-CHAIR
WEI SONG, COMMITTEE CO-CHAIR
JAMES RICHARDSON
MARK BARKEY

A THESIS

Submitted in partial fulfillment of the requirements
for the degree of Master of Science
in the Department of Civil, Construction, and Environmental Engineering
in the Graduate School of
The University of Alabama

TUSCALOOSA, ALABAMA

2016
Copyright David Isaac Burkhalter 2016
ALL RIGHTS RESERVED
ABSTRACT
Deep prestressed concrete bridge girders are becoming increasingly popular due to their
ability to span longer distances and reduce the total cost of bridge projects. However, these girders
have frequently been subject to end zone cracking during the transfer of prestress forces despite
being designed to current AASHTO specifications. Previously, the Alabama Department of
Transportation (ALDOT) has designed deep prestressed girders which can span up to 165 ft.
During the fabrication of these girders, crack formations in the end zone were typically noticed.
To address this concern, longitudinal reinforcement was added to the end zones. This solution
controlled cracking to some extent but could not completely eliminate cracking.
An experimental study was conducted to find a practical engineering solution to the
problem of end zone cracking, as well as to develop a 78 in. deep prestressed bulb-tee girder design
to reach a span length of 180 ft. 3D finite element modeling was used to find three practical
alternative end zone modifications to the standard design. The modified designs included a
lowered draping angle, partial debonding of the strands, and a combination of the two.
Four 54 ft. long specimens, including three with end zone modifications, were fabricated
at Hanson Pipe & Precast in Pelham, Alabama, and monitored during the detensioning process.
The end zones were instrumented with steel and concrete strain gauges to better understand the
complex behavior of girder end zones. External DEMEC instrumentation was also included at the
girder ends to measure the transfer length of the strands in each specimen. The specimens were
then load tested at the UA Large Scale Structures Laboratory (LSSL) to determine the effects of
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the modified end zone details on the girder capacity. Based on the study, modified girder end zone

details are recommended to ALDOT for implementation.
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DEDICATION
This thesis is dedicated to my loving family: to my mom, who taught me how to write; my
dad, who taught me how to solve problems; and my grandfathers, who taught me how to build.
Finally, this thesis is dedicated to my fiancée, who makes me a better person every day. Any
success I have is because of you all.

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LIST OF ABBREVIATIONS AND SYMBOLS
AASHTO American Association of State Highway and Transportation Officials
ACI American Concrete Institute
ALDOT Alabama Department of Transportation
AMS Average Maximum Strain
BT-78 Bulb-tee girder, 78 in. deep
DEMEC Demountable, mechanical (targets and gauges)
FDOT Florida Department of Transportation
FEM Finite Element Modeling
LRFD Load and Resistance Factor Design
LSSL UA’s Large Scale Structures Laboratory
SCC Self-Consolidating Concrete
WisDOT Wisconsin Department of Transportation
VDOT Virginia Department of Transportation

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ACKNOWLEDGEMENTS
I would like to thank all of the members of my thesis committee who made this research
opportunity possible for me and through whose continued efforts I gleaned knowledge and wisdom
that I will cherish throughout my career. Dr. Sriram Aaleti’s technical knowledge and enthusiasm
for engineering served an irreplaceable role throughout the entire development of this thesis. Dr.
Wei Song provided me with much insight and vision through both the experimental and writing
stages. I would also like to thank Vidya Sagar Ronanki whose guidance and willingness to help
throughout the project made the process not only possible, but enjoyable.
I also owe gratitude to the following graduate and undergraduate students for donating their
time to help me reach this goal: Luan Rocha Dominguez, Drew Landsell, Saeid Hayati, Shanglian
Zhou, Qi Kuang, Kobir Hossain, Shane Crawford, and Daniel Bridi Valentim. Collin Sewell, the
LSSL’s Research Engineer, provided me with a great amount of practical advice in the lab, for
which I am very appreciative.
This research was only possible through the generous funding from the Alabama
Department of Transportation, to whom our entire team is very grateful. Also, many thanks go to
the team at Hanson Pipe & Precast in Pelham, Alabama who worked with us through the
fabrication process. We would also like to thank Steve Koch at Sumiden wire for donating
prestressing strand and making it possible to construct the test girders in two phases.
Finally, I would like to thank God, my family, and my friends who provided me with the

support and encouragement that I needed to accomplish this goal.
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CONTENTS
Abstract ........................................................................................................................................... ii
Dedication ...................................................................................................................................... iv
List of Abbreviations and Symbols................................................................................................. v
Acknowledgements ........................................................................................................................ vi
Chapter 1 Introduction .................................................................................................................... 1
1.1. Background .......................................................................................................................... 1
Overview of Prestressed Concrete ................................................................................ 1
End Zone Cracking ....................................................................................................... 3
1.2. Project Objectives and Scope ............................................................................................... 4
1.3. Organization of Thesis ......................................................................................................... 5
Chapter 2 Review of End Zone Cracking and Transfer Length in Pretensioned Girders ............... 6
2.1. Introduction .......................................................................................................................... 6
2.2. Bond Theory of Pretensioned Concrete ............................................................................... 7
2.3. Review of End Zone Cracking in Pretensioned Concrete Girders ...................................... 9
2.4. AASHTO Provisions for Splitting Reinforcement .............................................................. 9
2.5. Previous Experimental and Analytical Research Related to End Zone Cracking ............. 10
Tuan et al. (2004) ........................................................................................................ 10
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Hamilton, Consolazio, & Ross (2013) ........................................................................ 14
2.5.2.1. FIB-54 Test Program ........................................................................................... 15
2.5.2.2. FIB-63 Test Program ........................................................................................... 19
Crispino (2007) ........................................................................................................... 24
Arab et al. (2014) ........................................................................................................ 32
Oliva & Okumus (2011) ............................................................................................. 39
2.6. Review of Transfer Length in Pretensioned Concrete Girders .......................................... 46
Code Provisions for Transfer Length .......................................................................... 46
2.6.1.1. AASHTO (2015) .................................................................................................. 46
2.6.1.2. ACI 318-14 .......................................................................................................... 47
2.7. Previous Research Associated with Transfer Length ........................................................ 47
Hanson and Kaar (1959) ............................................................................................. 48
Martin and Scott (1976) .............................................................................................. 49
Shahawy (1992) .......................................................................................................... 49
Russell and Burns (1993) ............................................................................................ 50
Ramirez and Russell (2008) ........................................................................................ 51
2.8. Previous Research Related to this Study ........................................................................... 51
Dunham (2011) ........................................................................................................... 51
Chapter 3 Design and Finite Element Modeling of the BT-78 ..................................................... 57
3.1. Introduction ........................................................................................................................ 57
3.2. Preliminary Design of the BT-78 ....................................................................................... 58
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3.3. Finite Element Model Properties ....................................................................................... 61
Analysis Model for a Typical Prestressed Girder ....................................................... 63
Calibration of the FEM ............................................................................................... 65
Modeling the BT-72 .................................................................................................... 66
3.4. Modeling the BT-78 ........................................................................................................... 67
Additional Vertical Reinforcement ............................................................................. 67
Partial Debonding ....................................................................................................... 68
Lower Draping ............................................................................................................ 69
Lower Draping and Partial Debonding ....................................................................... 69
3.5. End Zone Strain Gauge Placement .................................................................................... 70
3.6. Summary of the Finite Element Analysis Program ........................................................... 71
Chapter 4 Design and Fabrication of Experimental Specimens ................................................... 72
4.1. Introduction ........................................................................................................................ 72
4.2. Specimen Design ............................................................................................................... 72
4.3. Prestressing Strands ........................................................................................................... 76
Steel Reinforcement .................................................................................................... 79
4.3.1.1. Splitting Reinforcement ....................................................................................... 81
4.3.1.2. Confinement Reinforcement ................................................................................ 81
4.3.1.3. Reinforcement in the Top Flange ........................................................................ 81
Concrete Mix .............................................................................................................. 83
4.4. Specimen Fabrication......................................................................................................... 85
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