Table Of ContentAN ABSTRACT OF THE THESIS OF
Mackenzie M.W. Lostra for the degree of Master of Science in Civil Engineering presented on
September 8, 2016.
Title: Seismic Performance of Square Reinforced Concrete Columns Retrofitted with Titanium
Alloy Bars
Abstract approved:
Christopher C. Higgins André R. Barbosa
Large numbers of reinforced concrete (RC) bridges were built in the past that are now considered
seismically deficient. The structural members most likely to be considered deficient are the
supporting columns. Typical deficient columns contain inadequate transverse reinforcement and
poorly detailed lap splice lengths above the foundation. Insufficient lap splice lengths can lead to
bond failure and an inability to develop the strength of the longitudinal reinforcement.
Deterioration of the mechanical bond between the longitudinal reinforcement bars and the
surrounding concrete reduces the stiffness and strength of the column-footing joint and provides
limited or no ductility. In addition, widely spaced transverse reinforcement may not adequately
confine the base of the column. This permits premature buckling of the longitudinal
reinforcement that may occur between transverse bar locations and poor confinement of the
concrete core. Complete replacement of these bridges is not practical due to limited resources
thus, rehabilitation of existing deficient infrastructure is a practical approach. In this research,
titanium alloy bars (TiABs) were explored as an alternative material to retrofit RC columns with
poorly detailed reinforcing steel above the footing. The well-defined material properties of TiABs
have the potential to provide effective and economical seismic strengthening of deficient RC
columns. Compared to conventional reinforcing steel, they have relatively low stiffness, high
strength, high ductility, and are fully resistant to corrosion in the operating environment. The
proposed installation allows for inspection of the members and the environmental durability of
the TiABs make them a viable long-term solution for column strengthening. To evaluate the
potential for using TiABs to remediate seismically deficient RC columns with poor lap splice
details and inadequate transverse reinforcement that were common in the U.S. prior to 1970, four
full-scale columns were tested. One was a control specimen without strengthening and the other
three (3) had externally mounted TiABs. The specimens were subjected to fully reversed cyclic
lateral loading in the laboratory. The experimental results showed improved ductility and stable
cyclic response with minor flexural strength degradation in the specimens retrofitted with TiABs
and the failure modes of the columns were altered from non-ductile lap splice failure in the
conventionally reinforced column to ductile flexural failure in the retrofitted columns. They
demonstrated that TiABs offer a new option for effectively strengthening seismically deficient
square bridge columns.
Copyright by Mackenzie M.W. Lostra
September 8, 2016
All Rights Reserved
Seismic Performance of Square Reinforced Concrete Columns Retrofitted with Titanium Alloy
Bars
by
Mackenzie M.W. Lostra
A THESIS
Submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Master of Science
Presented September 8, 2016
Commencement June 2017
Master of Science thesis of Mackenzie M.W. Lostra presented on September 8, 2016.
APPROVED:
Co-Major Professor, representing Civil Engineering
Co-Major Professor, representing Civil Engineering
Head of the School of Civil and Construction Engineering
Dean of the Graduate School
I understand that my thesis will become part of the permanent collection of Oregon State University
libraries. My signature below authorizes the release of my thesis to any reader upon request.
Mackenzie M.W. Lostra, Author
ACKNOWLEDGEMENTS
I would like to thank my research advisors, Dr. Christopher Higgins and Dr. André Barbosa, for
assisting me throughout this project and for their continual guidance during my graduate school
career, not only as technical advisors but also as positive influences and mentors. Their support
during this process has been invaluable. I would also like to thank Dr. Matthew Evans and Dr. Mike
Bailey for being contributing advisors on my defense committee.
Secondly, I would like to thank the team of persons who contributed to the construction of this
project through its completion. I acknowledge my primary undergraduate assistants, Kyle Logan
and Jonathon Roy, who made my experience working as a graduate assistant sincerely enjoyable
and without whom this project would not have been possible – I am grateful for the many hours
that they dedicated. I also acknowledge our laboratory supervisor, Jeff Gent, who was an invaluable
aide. Other students who assisted on this project include Aléxia Ribeiro, Lance Parson, and Spenser
Maunu.
This project was funded by Perryman Company and I want to thank them for providing all of the
resources needed to complete this project. I would like to particularly acknowledge Jim Perryman
Sr. and Rose Perryman, Frank Perryman, Jim Perryman Jr., and Warren George, who were leading
contributors to this project.
To all other individuals who also helped on this project who were not specifically noted, I sincerely
extend my gratitude as well.
CONTRIBUTION OF AUTHORS
Dr. Christopher C. Higgins is the principal investigator of this research project. Dr. André R.
Barbosa is the co-principal investigator of this research project. Dr. Higgins and Dr. Barbosa and
the co-authors of this thesis.
TABLE OF CONTENTS
Page
1 INTRODUCTION .................................................................................................................. 1
1.1 Motivation and Background ............................................................................................ 1
1.2 Research Significance ..................................................................................................... 4
2 LITERATURE REVIEW ....................................................................................................... 5
2.1 Lap Splice Behavior ........................................................................................................ 5
2.2 Effective Confinement ................................................................................................... 10
2.3 Concrete Grade .............................................................................................................. 15
2.4 Alternative Retrofit Strategies ....................................................................................... 17
3 EXPERIMENTAL PLAN AND PROCEDURE .................................................................. 24
3.1 Conventional Column Design ....................................................................................... 24
3.2 Titanium Alloy Retrofit ................................................................................................. 33
3.3 Construction Sequence .................................................................................................. 44
3.4 Tension Tests ................................................................................................................. 48
3.5 Instrumentation .............................................................................................................. 53
3.6 Experimental Set-Up and Methodology ........................................................................ 57
4 TEST RESULTS AND ANALYSIS .................................................................................... 60
4.1 Observed Performance: Non-Retrofitted Specimen C1-L ............................................. 61
4.2 Observed Performance: Retrofitted Specimens C2-LRT, C3-LRS, and C4-RT ........... 65
4.3 Overall Force-Deformation Response ........................................................................... 73
4.4 Strength Degradation ..................................................................................................... 84
Page
4.5 Energy Dissipation ........................................................................................................ 88
4.6 Failure Modes ................................................................................................................ 93
4.7 Steel Reinforcement Strains .......................................................................................... 94
4.7.1 Strain Gage Notation ............................................................................................. 94
4.7.2 Longitudinal Steel: Specimen C1-L ...................................................................... 96
4.7.3 Longitudinal Steel: Specimen C2-LRT ............................................................... 101
4.7.4 Longitudinal Steel: Specimen C4-RT .................................................................. 105
4.7.5 Transverse Steel: Specimen C1-L ....................................................................... 106
4.7.6 Transverse Steel: Specimen C2-LRT .................................................................. 108
4.7.7 Transverse Steel: Specimen C4 ........................................................................... 110
4.8 T iAB Reinforcement Strains ....................................................................................... 111
4.8.1 Longitudinal TiABs: Specimen C2-LRT ............................................................ 112
4.8.2 Longitudinal TiABs: Specimen C4-RT ............................................................... 113
4.8.3 Transverse TiABs: Specimen C2-LRT ................................................................ 117
4.8.4 Transverse TiABs: Specimen C4-RT .................................................................. 118
4.9 C olumn Ductility ......................................................................................................... 119
4.9.1 Displacement Ductility ........................................................................................ 119
4.9.2 Curvature Ductility .............................................................................................. 123
4.10 C olumn Shear .............................................................................................................. 126
4.11 Retrofit Bond ............................................................................................................... 128
5 SUMMARY AND CONCLUSIONS ................................................................................. 134
6 REFERENCES ................................................................................................................... 136
7 APPENDIX......................................................................................................................... 139
Page
7.1 Appendix A ................................................................................................................. 139
7.2 Appendix B .................................................................................................................. 143
7.3 Appendix C .................................................................................................................. 162
Description:Deterioration of the mechanical bond between the longitudinal reinforcement bars and the surrounding concrete reduces the stiffness and strength of
