Citation
Experimental program for seismic connections to add ductility to cold-formed steel panels

Material Information

Title:
Experimental program for seismic connections to add ductility to cold-formed steel panels
Creator:
Wilson, Brian Scott ( author )
Place of Publication:
Denver, Colo.
Publisher:
University of Colorado Denver
Publication Date:
Language:
English
Physical Description:
1 electronic file (294 pages) : ;

Thesis/Dissertation Information

Degree:
Master's ( Master of science)
Degree Grantor:
University of Colorado Denver
Degree Divisions:
Department of Civil Engineering, CU Denver
Degree Disciplines:
Civil engineering

Subjects

Subjects / Keywords:
Earthquake resistant design ( lcsh )
Steel, Structural -- Ductility ( lcsh )
Earthquake resistant design ( fast )
Steel, Structural -- Ductility ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Review:
The purpose of this work is to explore connections that will perform elastically under normal loading conditions but will behave plastically when subjected to the higher forces experienced during an earthquake. These connections are vital to a framing system, and must provide sufficient ductility and strength for the cold-formed steel (CFS) building to remain standing throughout a seismic event. They must be economical to produce, and allow for ease of construction in the field. ( , )
Review:
The concept of using a yielding plate to add ductility to a connection is examined through the fabrication and testing of six different families of connections. The connection families were developed sequentially after lessons were learned from prior series. Each connection family utilized either small hot rolled steel plate or a short section of hollow structural steel (HSS) tube to provide the ductility in the connection. All connections were load tested cyclically and were subjected to a protocol of progressively increasing positive and negative displacements until the specimen failed. Failure mechanism, ultimate load capacity, and displacement were all evaluated to determine the suitability of each type of connection for further study, modification, rejection, or acceptance.
Bibliography:
Includes bibliographical references.
System Details:
System requirements: Adobe Reader.
Statement of Responsibility:
by Brian Scott Wilson.

Record Information

Source Institution:
University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
on10121 ( NOTIS )
1012117104 ( OCLC )
on1012117104
Classification:
LD1193.E53 2017m W55 ( lcc )

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Full Text
EXPERIMENTAL PROGRAM FOR SEISMIC CONNECTIONS TO ADD DUCTILITY
TO COLD-FORMED STEEL PANELS by
BRIAN SCOTT WILSON B.S., University of Florida 1997 M.S., University of Missouri, Rolla -2002
A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment Of the requirements of the degree of Master of Science Civil Engineering Program
2017


This thesis for the Master of Science degree by Brian Scott Wilson has been approved for the Civil Engineering Program by
Kevin L. Rens, Chair Frederick R. Rutz Carnot L. Nogueira
Date: July 29, 2017
n


Wilson, Brian Scott (M.S., Civil Engineering)
Experimental Program for Connections to Add Ductility to Cold-formed Steel Panels for Else in Seismic Applications
Thesis directed by Associate Professor Frederick R. Rutz, Advisor
ABSTRACT
The purpose of this work is to explore connections that will perform elastically under normal loading conditions but will behave plastically when subjected to the higher forces experienced during an earthquake. These connections are vital to a framing system, and must provide sufficient ductility and strength for the cold-formed steel (CFS) building to remain standing throughout a seismic event. They must be economical to produce, and allow for ease of construction in the field.
The concept of using a yielding plate to add ductility to a connection is examined through the fabrication and testing of six different families of connections. The connection families were developed sequentially after lessons were learned from prior series. Each connection family utilized either small hot rolled steel plate or a short section of hollow structural steel (HSS) tube to provide the ductility in the connection. All connections were load tested cyclically and were subjected to a protocol of progressively increasing positive and negative displacements until the specimen failed. Failure mechanism, ultimate load capacity, and displacement were all evaluated to determine the suitability of each type of connection for further study, modification, rejection, or acceptance.
The form and content of this abstract are approved. I recommend its publication.
Approved: Frederick R. Rutz
m


DEDICATION
I dedicate my thesis work to my wife Gina who has supported me throughout this process of going back to school and changing careers. She made this all possible by giving me her full, loving, and enthusiastic permission to embark upon this life changing adventure we have been on. To my sons, Jacob and Lucas who are growing into fine young men. Your assistance at home when I have been gone has made it possible for me to focus on the business at hand. To my parents whose support throughout the years has allowed me to live a charmed life. The adventures you gave me in childhood, lead me to continue seeking them as an adult.
IV


ACKNOWLEDGEMENTS
I cannot express the gratitude I have to Dr. Fred Rutz for his mentorship, advice, and participation on this project. I have truly enjoyed working closely with him in the lab. There are few individuals as dedicated to developing young (and not so young) professionals as this man. I want to thank and offer my appreciation to Dr. Kevin Rens and Dr. Carnot Nogueira, for their participation and service as member of my examination committee.
This work would not be possible without the support of J.R. Harris & Company. I want to thank Jim Harris his for the amazing opportunity to actively contribute to his outstanding organization. To Gene Stevens for freely sharing his knowledge and enthusiasm for this research. And to Holly Janowicz for her major contribution in analyzing the data and cheerfully answering my numerous questions throughout this project.
A special thanks to Michael Lastowski co-founder of Prescient for allowing me to participate in research and development of this concept. His entrepreneurial spirit and enthusiasm is infectious.
To Jac Corless and Tom Thuis in providing outstanding support in the execution of testing in the University of Colorado, Denvers structural lab. The aggressive testing schedule could not have been possible without their help.
v


TABLE OF CONTENTS
CHAPTER 1........................................................................1
1.1. Background...............................................................1
1.2. Scope of Investigation...................................................5
CHAPTER II.......................................................................6
2.1. Why seismic loads are considered in design...............................6
2.2. Systems in steel construction to resist lateral forces...................9
2.2.1. Concentrically Braced Frames........................................10
2.2.2. Moment Resisting Frames.............................................11
2.2.3. Eccentrically Braced Frames.........................................13
2.2.4. Buckling-Restrain Braced Frames.....................................14
CHAPTER III.....................................................................16
3.1 Scope of testing.........................................................16
3.1.1. A-Series Connection.................................................17
3.1.2. T-Series Connection.................................................19
3.1.3. E-Series Connection.................................................22
3.1.4. UC-Series Connection................................................24
3.1.5. UE-Series Connection................................................26
3.1.6. TN-Series Connection................................................28
3.2. Testing procedure.......................................................29
vi


CHAPTER IV
36
4.1. Description of outputs..................................................36
4.2. Analysis of Connections.................................................39
4.2.1. A-series............................................................40
4.2.2. T-series............................................................47
4.2.3. E-series............................................................53
4.2.4. UC-series...........................................................60
4.2.5. UE-series...........................................................66
4.2.6. TN-Series...........................................................71
4.3. Theoretical vs experimental load values.................................73
CHAPTER V.......................................................................81
5.1. Lessons Learned.........................................................81
5.2. Recommendations for further investigation...............................81
REFERENCES......................................................................83
APPENDIX A......................................................................85
A. 1 A-series samples........................................................86
A.2 T-series samples........................................................104
A.3 E-series samples........................................................113
A.4 UC-series samples.......................................................125
A.5 UE-series samples.......................................................131
A.6 PUC-series samples......................................................135
vii


A.7PE-series samples.........................................................138
A. 8 TN-series samples......................................................141
APPENDIX B.....................................................................147
B. l. A-Series Graphs.......................................................148
B.2 T-Series Graphs..........................................................182
B.3 E-Series Graphs..........................................................200
B.4 UC-Series Graphs.........................................................230
B.5 UE-Series Graphs.........................................................248
B.6 TN-Series Graphs.........................................................256
viii


LIST OF FIGURES
FIGURE
Figure 1.1. Example of typical panel and column in construction........................2
Figure 1.2 Location of Connections on atypical CFS Panel...............................3
Figure 1.3 Concept of yielding plate connection to HSS column. Showing compression and
tension cycle..........................................................................4
Figure 2.1 Aftermath of San Francisco, CA earthquake, 1906.............................7
Figure 2.2 Damage to Venice high school 1933...........................................7
Figure 2.3 Destroyed building after earthquake in Loma Prieta, CA 1989. (Nikitin 1989) .... 8 Figure 2.4 Damaged parking structure after the Northridge earthquake, 1994. (Celebi n.d.) 9
Figure 2.5 Examples of concentrically braced frames....................................10
Figure 2.6 A connection in a concentrically braced frame...............................11
Figure 2.7 Layout of a moment frame.....................................................12
Figure 2.8. Typical moment frame connection showing the reduced beam section...........12
Figure 2.9 Example of eccentrically braced frame layouts...............................13
Figure 2.10 Building with an eccentrically braced frame structural system..............14
Figure 2.11 Illustration of a buckling restrained brace................................15
Figure 2.12 Buckling restrained braces installed in a building frame...................15
Figure 3.1 Bushings used to generate plastic hinges in the yielding plate of the connection. From left to right. 1.5 round, 2.5 round, 2 rectangular, 2.75 rectangular, 3 rectangular,
and 3.5 rectangular....................................................................17
Figure 3.2 A-Series Connection..........................................................18
Figure 3.3 A-Series Connection..........................................................18
IX


Figure 3.4 Detail of welds between gusset plate and yielding plate...................19
Figure 3.5 T-Series Connection, version 1. The bold lines indicate fillet weld locations.20
Figure 3.6 T-Series Connection, version 1............................................20
Figure 3.7 T-Series Connection, version 2............................................21
Figure 3.8 T-Series Connection, version 2............................................22
Figure 3.9 E-Series Connection.......................................................23
Figure 3.10 E-Series Connection......................................................23
Figure 3.11 UC-Series Connection.....................................................24
Figure 3.12 UC-Series Connection....................................................25
Figure 3.13 UE-Series Connection.....................................................26
Figure 3.14 UE-Series Connection....................................................27
Figure 3.15 TN-Series Connection.....................................................28
Figure 3.16 TN-Series Connection....................................................29
Figure 3.17 Graph of CUREE protocol, displacement vs. time...........................31
Figure 3.18 Test jig for concentrically loaded specimens.............................32
Figure 3.19 Photograph of a concentrically loaded sample in the MTS..................33
Figure 3.20 Test jig for eccentrically loaded specimens..............................34
Figure 3.21 Photograph of an eccentrically loaded sample.............................35
Figure 4.1 Typical graphs of displacement and force vs time..........................37
Figure 4.2 Typical Load vs. displacement (hysteresis) graph..............................38
Figure 4.3 Change in dimension between walls of HSS during tension and compression
cycles...................................................................................39
Figure 4.4 Backbone curve overlaid on a hysteresis graph............................40
x


Figure 4.5 Example of local buckling of the unreinforced stud flanges, bending of top
bushing, and failure of the weld between the gusset and the edge of the yielding plate.41
Figure 4.6 Illustration of permanent deformation in 3/8 top bushing. Deformation shown in
the photograph occurred in the tension cycle.............................................42
Figure 4.7 Example of horizontal shift in data to gaps between mounting pin and yoke
without the use of wedges................................................................43
Figure 4.8 Wedges used to remove mechanical slack in top and bottom mounting yokes. ... 43
Figure 4.9 Wedges installed in lower mounting assembly...................................44
Figure 4.10 Use of wedges eliminated horizontal shift in the graph. Compare to graph shown
in figure 4.7............................................................................45
Figure 4.11 T-series back bone curve for 1/4 thick HSS section. Comparing 3.5 square, 2
rectangular, and 1.5 round bushings.....................................................48
Figure 4.12T-series back bone curve for 5/16 thick HSS section. Comparing 3.5 square, 2
rectangular, and 1.5 round bushings.....................................................49
Figure 4.13 T-series back bone curve for 3.5 square bushing. Comparing 1/4 and 5/16
thick HSS................................................................................50
Figure 4.14T-series back bone curve for 2 rectangular bushing. Comparing 1/4 and 5/16
thick HSS................................................................................51
Figure 4.15T-series back bone curve for 1.5 round bushing. Comparing 1/4 and 5/16
thick HSS................................................................................52
Figure 4.16 E-series back bone curve for 3/16 thick HSS section. Comparing 3 rectangular, and 1.5 round bushings.
54


Figure 4.17 E-series back bone curve for 1/4 thick HSS section. Comparing 3 rectangular,
and 1.5 round bushings................................................................55
Figure 4.18 E-series back bone curve for 5/16 thick HSS section. Comparing 3
rectangular, and 1.5 round bushings....................................................56
Figure 4.19 E-series back bone curve for 3 rectangular bushing. Comparing 3/16, 1/4,
and 5/16 thick HSS.....................................................................57
Figure 4.20 E-series back bone curve for 1.5 round bushing. Comparing 3/16, 1/4, and
5/16 thick HSS.........................................................................58
Figure 4.21 UC-series back bone curve for 1/4 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings....................................................61
Figure 4.22 UC-series back bone curve for 5/16 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings....................................................62
Figure 4.23 UC-series back bone curve for 3/8 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings....................................................63
Figure 4.24 UC-series back bone curve for 3 rectangular bushing. Comparing 1/4, 5/16,
and 3/8 thick yielding plate...........................................................64
Figure 4.25 UC-series back bone curve for 1.5 round bushing. Comparing 1/4, 5/16, and
3/8 thick yielding plate...............................................................65
Figure 4.26 UE-series back bone curve for 5/16 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings....................................................67
Figure 4.27 UE-series back bone curve 3/8 thick yielding plate. Comparing 3 rectangular, and 1.5 round bushings.................................................................68
xii


Figure 4.28 UE-series back bone curve for 3 rectangular bushing. Comparing 5/16, and
3/8 thick yielding plates..................................................................69
Figure 4.29 UE-series back bone curve for 1.5 round bushing. Comparing 5/16, and 3/8
thick yielding plates.......................................................................70
Figure 4.30 TN-series back bone curve for 1/4 thick HSS section. Comparing 3
rectangular, and 1.5 round bushings........................................................72
Figure 4.31 Illustration of plastic hinges forming in a yield plate around a bushing. Large
displacements lead to x < x..............................................................74
Figure 4.32 Tested yield stress of 50 ksi nominal, steel plate..............................77
Figure 4.33 Stress strain curve for 50ksi nominal steel.................................78
Figure 4.34 Yield plate in large compression displacement...................................80
Figure Al. Sample A1 before testing.........................................................86
Figure A2. Sample Al after testing..........................................................86
Figure A3. Sample A2 before testing.........................................................87
Figure A4. Sample A2 after testing..........................................................87
Figure A5. Sample A3 before testing.........................................................88
Figure A6. Sample A3 after testing..........................................................88
Figure A7. Sample A4 before testing.........................................................89
Figure A8. Sample A4 after testing..........................................................89
Figure A9. Sample A5 before testing.........................................................90
Figure A10. Sample A5 after testing.........................................................90
Figure All. Sample A6 before testing........................................................91
Figure A12. Sample A6 after testing.........................................................91
xiii


Figure A13. Sample A7 before testing........................................................92
Figure A14. Sample A7 after testing........................................................92
Figure A15. Sample A8 before testing.......................................................93
Figure A16. Sample A8 after testing........................................................93
Figure A17. Sample A9 before testing.......................................................94
Figure A18. Sample A9 after testing........................................................94
Figure A19. Sample A10 before testing......................................................95
Figure A20. Sample A10 after testing.......................................................95
Figure A21. Sample A11 before testing......................................................96
Figure A22. Sample all after testing............................................................96
Figure A23. Sample A12 before testing......................................................97
Figure A24. Sample A12 after testing.......................................................97
Figure A25. Sample A13 before testing......................................................98
Figure A26. Sample A13 after testing.......................................................98
Figure All. Sample A14 before testing......................................................99
Figure A28. Sample A14 after testing.......................................................99
Figure A29. Sample A15 before testing.....................................................100
Figure A30. Sample A15 after testing......................................................100
Figure A31. Sample A16 before testing.....................................................101
Figure A32. Sample A16 after testing......................................................101
Figure A33. Sample A17 before testing.....................................................102
Figure A34. Sample A17 after testing......................................................102
Figure A3 5. Sample A18 before testing.....................................................103
xiv


103
Figure A3 6. Figure A3 7. Figure A3 8. Figure A3 9. Figure A40. Figure A41. Figure A42. Figure A43. Figure A44. Figure A45. Figure A46. Figure A47. Figure A48. Figure A49. Figure A50. Figure A51. Figure A52. Figure A53. Figure A54. Figure A55. Figure A56. Figure A57. Figure A58.
Sample A18 after testing.
Sample T1 before test.
Sample T1 after test..
Sample T2 before test.
Sample T2 after test..
Sample T3 before test.
Sample T3 after test..
Sample T4 before test.
Sample T4 after test..
Sample T5 before test.
Sample T5 after test..
Sample T6 before test.
Sample T6 after test..
Sample T7 before test.
Sample T7 after test..
Sample T8 before test.
Sample T8 after test..
Sample T9 before test.
Sample T9 after test..
Sample El before test.
Sample El after test..
Sample E2 before test.
Sample E2 after test..
104
104
105
105
106 106 107
107
108 108 109
109
110 110 111 111 112 112 113
113
114 114
xv


Figure A59. Sample E3 before test..................................................115
Figure A60. Sample E3 after test...................................................115
Figure A61. Sample E4 before test..................................................116
Figure A62. Sample E4 after test...................................................116
Figure A63. Sample E5 before test..................................................117
Figure A64. Sample E5 after test...................................................117
Figure A65. Sample E6 before test..................................................118
Figure A66. Sample E6 after test...................................................118
Figure A67 Sample E7 before test...................................................119
Figure A68. Sample E7 after test...................................................119
Figure A69. Sample E8 before test..................................................120
Figure A70. Sample E8 after test...................................................120
Figure A71. Sample E9 before test..................................................121
Figure A72. Sample E9 after test...................................................121
Figure A73. Sample El0 before test.................................................122
Figure A74. Sample E10 after test..................................................122
Figure A75. Sample El 1 before test................................................123
Figure A76. Sample El 1 after test.................................................123
Figure A77. Sample E12 before test.................................................124
Figure A78. Sample E12 after test..................................................124
Figure A79. Sample EiCl before test................................................125
Figure A80. Sample EiCl after test.................................................125
Figure A81. Sample EiC2 before test................................................126
xvi


Figure A82. Sample UC2 after test
Figure A83. Sample UC3 before test....
Figure A84. Sample UC3 after test
Figure A85. Sample UC4 before test....
Figure A86. Sample UC4 after test
Figure A87. Sample UC5 before test....
Figure A88. Sample UC5 after test
Figure A89. Sample UC6 before test....
Figure A90. Sample UC6 after test
Figure A91. Sample UE1 before test....
Figure A92. Sample UE1 after test
Figure A93. Sample UE2 before test....
Figure A94. Sample UE2 after test
Figure A95. Sample UE3 before test....
Figure A96. Sample UE3 after test
Figure A97. Sample UE4 before test....
Figure A98. Sample UE4 after test
Figure A99. Sample PUC1 before test..
Figure A100 Sample PUC1 after test
Figure A101 . Sample PUC2 before test.
Figure A102 . Sample PUC2 after test...
Figure A103 . Sample PUC3 before test.
Figure A104 . Sample PUC3 after test...
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XVII


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Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
A105. Sample PEI before test........
A106 Sample PEI after test...........
A107. Sample PE2 before test.........
A108. Sample PE2 after test..........
A109. Sample PE3 before test.........
A110. Sample PE3 after test..........
A111. Sample TN1 before test.........
A112. Sample TNI after test..........
A113. Sample TN2 before test.........
A114. Sample TN2 after test..........
A115. Sample TN3 before test.........
A116. Sample TN3 after test..........
A117. Sample TN4 before test.........
A118. Sample TN4 after test..........
A119. Sample TN5 before test.........
A120. Sample TN5 after test..........
A121. Sample TN6 before test.........
A122. Sample TN6 after test..........
Bl. Sample Al, force vs displacement.
B2. Sample Al, displacement vs time..
B3. Sample Al, load vs time..........
B4. Sample A3, force vs displacement.
B5. Sample A3, displacement vs time.
xviii
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Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
B6. Sample A3, force vs time...........
B7. Sample A4, force vs displacement...
B8. Sample A4, displacement vs time....
B9. Sample A4, force vs time...........
BIO. Sample A5, force vs displacement... Bll. Sample A5, displacement vs time....
B12. Sample A5, force vs time..........
B13. Sample A6, force vs displacement... B14. Sample A6, displacement vs time....
B15. Sample A6, force vs time..........
B16. Sample A7, force vs displacement... B17. Sample A7, displacement vs time....
B18. Sample A7, force vs time..........
B19. Sample A8, force vs displacement... B20. Sample A8, displacement vs time....
B21. Sample A8, force vs time..........
B22. Sample A9, force vs displacement... B23. Sample A9, displacement vs time....
B24. Sample A9, force vs time..........
B25. Sample A10, force vs displacement. B26. Sample A10, displacement vs time..
B27. Sample A10, force vs time.........
B28. Sample All, force vs displacement.
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xix


Figure B29. Sample
Figure B30. Sample
Figure B31. Sample
Figure B32. Sample
Figure B33. Sample
Figure B34. Sample
Figure B35. Sample
Figure B36. Sample
Figure B37. Sample
Figure B38. Sample
Figure B39. Sample
Figure B40. Sample
Figure B41. Sample
Figure B42. Sample
Figure B43. Sample
Figure B44. Sample
Figure B45. Sample
Figure B46. Sample
Figure B47. Sample
Figure B48. Sample
Figure B49. Sample
Figure B50. Sample
Figure B51. Sample
All, displacement vs time.
All, force vs time.........
A12, force vs displacement. A12, displacement vs time.
A12, force vs time.........
A13, force vs displacement. A13, displacement vs time.
A13, force vs time.........
A14, force vs displacement. A14, displacement vs time.
A14, force vs time.........
15, force vs displacement... A15, displacement vs time.
A15, force vs time.........
A16, force vs displacement. A8, displacement vs time...
A16, force vs time.........
A17, force vs displacement. A17, displacement vs time.
A17, force vs time.........
A18, force vs displacement. A18, displacement vs time. A18, force vs time.........
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Figure B52. Sample Tl,
Figure B53. Sample Tl,
Figure B54. Sample Tl,
Figure B55. Sample T2,
Figure B56. Sample T2,
Figure B57. Sample T2,
Figure B58. Sample T3,
Figure B59. Sample T3,
Figure B60. Sample T3,
Figure B61. Sample T4,
Figure B62. Sample T4,
Figure B63. Sample T4,
Figure B64. Sample T5,
Figure B65. Sample T5,
Figure B66. Sample T5,
Figure B67. Sample T6,
Figure B68. Sample T6,
Figure B69. Sample T6,
Figure B70. Sample T7,
Figure B71. Sample T7,
Figure B72. Sample T7,
Figure B73. Sample T8,
Figure B74. Sample T8,
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
force vs time.........
force vs displacement, displacement vs time..
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xxi


Figure B75. Sample T8,
Figure B76. Sample T9,
Figure B77. Sample T9,
Figure B78. Sample T9,
Figure B79. Sample El,
Figure B80. Sample El,
Figure B81. Sample El,
Figure B82. Sample E2,
Figure B83. Sample E2,
Figure B84. Sample E2,
Figure B85. Sample E3,
Figure B86. Sample E3,
Figure B87. Sample E3,
Figure B88. Sample E4,
Figure B89. Sample E4,
Figure B90. Sample E4,
Figure B91. Sample E5,
Figure B92. Sample E5,
Figure B93. Sample E5,
Figure B94. Sample E6,
Figure B95. Sample E6,
Figure B96. Sample E6,
Figure B97. Sample E7,
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement.. displacement vs time....
force vs time..........
force vs displacement..
xxii
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Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
B98. Sample E7, displacement vs time....
B99. Sample E7, force vs time...........
B100. Sample E8, force vs displacement... B101. Sample E8, displacement vs time....
B102. Sample E8, force vs time..........
B103. Sample E9, force vs displacement... B104. Sample E9, displacement vs time....
B105. Sample E9, force vs time..........
B106. Sample E10, force vs displacement. B107. Sample E10, displacement vs time..
B108. Sample E10, force vs time.........
B109. Sample El 1, force vs displacement. B110. Sample El 1, displacement vs time..
Bill. Sample El 1, force vs time........
B112. Sample E12, force vs displacement. B113. Sample El2, displacement vs time..
B114. Sample El2, force vs time.........
B115. Sample PEI, force vs displacement. B116. Sample PEI, displacement vs time..
B117. Sample PEI, force vs time.........
B118. Sample PE2, force vs displacement. B119. Sample PE2, displacement vs time.. B120. Sample PE2, force vs time.........
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225
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226 227 227
xxm


Figure B121. Sample
Figure B122. Sample
Figure B123. Sample
Figure B124. Sample
Figure B125. Sample
Figure B126. Sample
Figure B127. Sample
Figure B128. Sample
Figure B129. Sample
Figure B130. Sample
Figure B131. Sample
Figure B132. Sample
Figure B133. Sample
Figure B134. Sample
Figure B135. Sample
Figure B136. Sample
Figure B137. Sample
Figure B138. Sample
Figure B139. Sample
Figure B140. Sample
Figure B141. Sample
Figure B142. Sample
Figure B143. Sample
PE3, force vs displacement... PE3, displacement vs time....
PE3, force vs time..........
UC1, force vs displacement.. EiCl, displacement vs time...
EiCl, force vs time.........
UC2, force vs displacement.. UC2, displacement vs time...
UC2, force vs time..........
UC3, force vs displacement.. EiC3, displacement vs time...
EiC3, force vs time.........
UC4, force vs displacement.. UC4, displacement vs time...
UC4, force vs time..........
UC5, force vs displacement.. UC5, displacement vs time...
UC5, force vs time..........
UC6, force vs displacement.. UC6, displacement vs time...
UC6, force vs time..........
PUC1, force vs displacement. PUC1, displacement vs time.
228
229
229
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231
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XXIV


Figure B144. Sample
Figure B145. Sample
Figure B146. Sample
Figure B147. Sample
Figure B148. Sample
Figure B149. Sample
Figure B150. Sample
Figure B151. Sample
Figure B152. Sample
Figure B153. Sample
Figure B154. Sample
Figure B155. Sample
Figure B156. Sample
Figure B157. Sample
Figure B158. Sample
Figure B159. Sample
Figure B160. Sample
Figure B161. Sample
Figure B162. Sample
Figure B163. Sample
Figure B164. Sample
Figure B165. Sample
Figure B166. Sample
PUC1, force vs time........
PUC2, force vs displacement. PUC2, displacement vs time.
PUC2, force vs time........
PUC3, force vs displacement. PUC3, displacement vs time.
PUC3, force vs time........
UE1, force vs displacement.. UE1, displacement vs time...
UE1, force vs time.........
UE2, force vs displacement.. UE2, displacement vs time. ..
UE2, force vs time.........
UE3, force vs displacement.. UE3, displacement vs time. ..
UE3, force vs time.........
UE4, force vs displacement.. UE4, displacement vs time. ..
UE4, force vs time.........
TNI, force vs displacement.. TNI, displacement vs time...
TNI, force vs time.........
TN2, force vs displacement..
243
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XXV


Figure B167. Sample TN2,
Figure B168. Sample TN2,
Figure B169. Sample TN3,
Figure B170. Sample TN3,
Figure B171. Sample TN3,
Figure B172. Sample TN4,
Figure B173. Sample TN4,
Figure B174. Sample TN4,
Figure B175. Sample TN5,
Figure B176. Sample TN5,
Figure B177. Sample TN5,
Figure B178. Sample TN6,
Figure B179. Sample TN6,
Figure B180. Sample TN6,
displacement vs time.
force vs time........
force vs displacement, displacement vs time.
force vs time........
force vs displacement, displacement vs time.
force vs time........
force vs displacement, displacement vs time.
force vs time........
force vs displacement, displacement vs time, force vs time........
259
259
260 261 261 262 263
263
264
265
265
266 267 267
XXVI


LIST OF TABLES
TABLE
4.1. A-Series summary of tension, displacement, and failure modes....................46
4.2. T-Series summary of tension, displacement, and failure modes....................53
4.3. E-Series summary of tension, displacement, and failure modes....................59
4.4. UC-Series summary of tension, displacement, and failure modes..................65
4.5. UE-Series summary of tension, displacement, and failure modes..................71
4.6. TN-Series summary of tension, displacement, and failure modes..................73
4.7 Comparison of Theoretical to Actual Forces in connections for various plate
thicknesses.........................................................................79
xxvii


CHAPTER I
INTRODUCTION
1.1. Background
Adding ductility to a cold formed steel frame, so that it may resist the high lateral demands induced by seismic events, is challenging due to the nature of the material. While the cold-formed steel (CFS) in many cases has a better ductility than many hot-rolled steels used in construction, the small cross sectional areas of various members do not allow for significant energy dissipation in the event of an earthquake. These members also tend to be weak in transverse loading conditions, perpendicular to their cross sections, compared to their capacities when loaded in an the longitudinal direction. Because of this, the standard methods of resisting lateral loads due to an earthquake are difficult to apply. A study by Lee and Foutch (2010) evaluating CFS braced frame structures finds that, they do not reach designed seismic resistance using current design code and using conservative R factors did not necessarily increase performance.
A revolutionary construction method of using predesigned/prefabricated CFS structural panels connected to hollow structural section (HSS) columns has been developed that increases the efficiency of construction in CFS. Factory manufactured assemblies are shipped to a job site where they are connected together, forming the structural system of a building. Figure 1.1 shows a typical 8 foot long panel connected to a HSS column.
1


Figure 1.1. Example of typical panel and column in construction.
This method of construction greatly reduces engineering and construction cost and time. These economic factors have resulted in an increase in demand for such structures.
While the current design meets all load and serviceability requirements for resisting lateral loads in low-seismic regions, improved story stiffness and ductility for construction in a seismically active area is needed. An extensive research and development program to add lateral strength and ductility to this building system is underway.
Traditional steel structures absorb seismic energy through the ductility of members, this system absorbs energy in the connections. A study by Uang et al. (2010) determined that that conventional strong column/weak beam seismic design philosophy was not appropriate for a CFS moment frame (Dao & Van De Lindt 2013). Due to the limitations of the cold-formed steel, a unique approach was taken to add ductility to the system by installing yielding plates in the connection between CFS panels and HSS columns. Metal bushings are used on either side of a yielding plate so that the plate can plastically deform around the
2


bushings during displacement. Figure 1.2 shows the general arrangement of the connections for the panel to posts.
Figure 1.2 Location of Connections on a typical CFS Panel
3


Yielding Plate
Jushing
Figure 1.3 Concept of yielding plate connection to HSS column. Showing compression and
tension cycle.
The purpose of the yielding plates is to dissipate the energy imparted to the building system during an earthquake. They also add ductility to the system to make use of the strength of the steel as it deforms plastically. The challenge is finding a combination of material and connection geometry that will provide an elastic response sufficient to resist wind loads, and a plastic response to absorb earthquake energy, all while maintaining positive connection between panel and column. If the system is too stiff other lateral force resisting members may be damaged before significant energy has been dissipated. If the system is not stiff enough it may be unable to resist non-seismic lateral loads elastically.
This approach to adding ductility to a system by utilizing a yielding connection, is a departure from current practice, where connections are designed with an overs strength factor to ensure elastic behavior. Structural members other than the connection are designed to yield and provide the ductility for the system. Four of the most common methods of adding ductility to a structure made from structural steel will be discussed in chapter 2 of this work.
4


1.2. Scope of Investigation
In the scope of this thesis, six types of connections were tested using a cyclic loading profile of increasing displacements in a Material Testing System (MTS) testing machine to evaluate the performance of each specimen. The connection designs evolved throughout the investigation, while considering tested performance and manufacturing efficiencies. The purpose of the research in this work is to develop a design for a connection between a cold formed-steel structural-panel to aHSS column, for commercial production in seismically active regions.
Due to the difficulty in computer modeling this component, an experimental analysis of the samples is used to evaluate their performance in both failure mode and their response to displacements. Connections need to be able to resist multiple cycles of loading, while providing consistent and predictable force resisting performance. Based on estimated building demands, an acceptable connection will be able to resist a 16 kip load, or more, and a displacement of greater than 1 inch.
As the tested connections are to be incorporated into a new building system, to resist seismic demands, the new structural CFS panel system must be analyzed, to quantify its anticipated performance. FEMA document P695, Quantification of Building Seismic Performance Factors, outlines a method for doing this (FEMA 2009). The results from this work will be used in the generation of a link, to be used in a future computer model. This model will be used for the development of a building archetype for this method of construction and also as a component in the generation of a Response Modification coefficient (or R-value) for the building system.
5


CHAPTER II
BACKGROUND
2.1. Why seismic loads are considered in design
Seismic loads must be considered in design, for the simple reason of it being a code requirement. ASCE 7-10, Minimum Design Loadfor Buildings and Other Structures, states that Every structure, and portion thereof, including nonstructural components, shall be designed and constructed to resist the effects of earthquake motions..(ASCE 2010).
ASCE 7-10 dedicates 15 chapters of its 31 chapters to seismic design. In addition to ASCE 7, which is the minimum standard to design to, there are numerous other seismic requirements required at every level of building jurisdiction from local, up through federal government.
Only considering the required reasons for designing for seismic events neglects the fact, development of codes and regulations arose from lessons learned from catastrophic seismic events that have caused large scale loss of life, damage to property and infrastructure. According to former FEMA Director James Lee Witt, The hazards associated with earthquakes in the U.S. has remained relatively constant over time, but the risk associated with them has increased, as population centers have grown in seismically active areas. (Arguero n.d.). Over 70 notable earthquakes have struck the U.S. since the 1700s. In 1906 a 7.9 magnitude earth quake struck San Francisco, CA. Figure 2.1 shows the city afterwards. There were an estimated 3000 deaths. It is estimated that this event would cause an economic loss of $120 billion if it were to occur today (London 2006). This event began serious research and discussion on earthquake engineering in the U.S. but did not produce any definitive seismic code (Berg 1983).
6


Figure 2.1 Aftermath of San Francisco, CA earthquake, 1906
In 1933 a 6.4 magnitude earthquake occurred near Long Beach, CA causing 120 deaths and damaging many structures including schools. This event spurred the California legislature to develop regulations for schools, masonry buildings, and set standards for of some seismic design requirements (Berg 1983). Damage to Venice high school is shown in figure 2.2.
Figure 2.2 Damage to Venice high school 1933.
7


More recently, the 1989 6.9 magnitude earthquake in Loma Prieta, CA caused 63
deaths, injured over 3700 people, and caused over $6 billion in damage at the time.
Figure 2.3 Destroyed building after earthquake in Loma Prieta, CA 1989. (Nikitin 1989)
The 6.7 magnitude earthquake that struck Northridge, CA, in 1994 killed 57 people and did over $44 billion in damages. Lessons are still being learned from these events and have had significant effect on the development of current design code and construction methods. Figure 2.4 Illustrates an example of the damage caused to structures from the earthquake.
8


Figure 2.4 Damaged parking structure after the Northridge earthquake, 1994. (Celebi n.d.)
2.2. Systems in steel construction to resist lateral forces
The study and codification of seismic design requirements has led to not only development of regulations and code requirements, but also lead to the generation of design manuals for various materials and construction methods. The American Institute of Steel Construction (AISC) publishes the Seismic Design Manual which covers the specific details of designing in structural steel for seismic loads. Four of the most common methods for resisting lateral loads in steel design are discussed below. A common feature of all the methods, is the connections between horizontal and vertical load bearing members are designed so that the ductile yielding is developed within the members themselves and not the connection. Specific members or portions of a member are designed to yield plastically or by buckling, thus dissipating some of the seismic energy imparted to the structure. Sabols
9


(2010) ASCE seminar regarding the seismic connections explains that they .Attempt to develop ductile behavior in steel seismic systems by detailing fuses to sustain large inelastic deformations prior to rupture or instability. He goes on to state that the other frame elements must be stronger than the fuses, especially the connections.
2.2.1. Concentrically Braced Frames
Concentrically braced frames are one of the most common construction methods using steel to resist lateral loads due to their being one of the most economical, in terms of material, fabrication and erection costs (AISC 2012). They operate similar to a truss except they are designed for resisting lateral versus vertical loads. The diagonal cross bracing members are designed to work axially in tension and compression in opposing pairs. The center lines of connecting members, columns, beams, and diagonal braces all intersect at a point to reduce rotation and moment at a connection. Figure 2.5 illustrates two of the various types of concentrically braced frames. Figure 2.6 shows a connection in a concentrically braced frame.
Figure 2.5 Examples of concentrically braced frames.
10


Figure 2.6 A connection in a concentrically braced frame.
These systems are relatively stiff, not allowing for as much story drift as other systems. The get their ductility from the buckling of a diagonal member in compression.
The members generally buckle out plane when they do so. The cross bracing can be limiting in locating doors, windows and corridors due to the obstruction they cause.
2.2.2. Moment Resisting Frames
Moment resisting frames use a concept described as strong column/weak beam. The beams have section of reduced area, generally where a section of the flange is removed, that is designed to yield plastically when the frame is exposed a seismic load. This reduced area section of the beam is designed to yield before other members in the structural frame do. The strength of the connection must be such that it is capable of developing the plastic hinge in the beam section. Figure 2.7 illustrates the general frame layout of a typical moment frame.
11


Figure 2.7 Layout of a moment frame.
Figure 2.8 shows the connection in a moment frame and the protected zone of the reduced section. The yellow cross hatching is to designate the area that is to be protected from damage or attachments that might affect the designed performance or initiate a failure originating from cracks or penetrations.
Figure 2.8. Typical moment frame connection showing the reduced beam section.
The moment frame generally has more ductility but less stiffness than the concentrically braced frame and often uses less economical steel shapes. The beams and columns must be larger than a comparable braced frame for resisting vertical loads. This is
12


so that the connections may be designed such that the structure can resist the lateral loads applied to the structure.
2.2.3. Eccentrically Braced Frames
An eccentrically braced frame combines aspects from the concentrically braced frame and moment frame concept to get the best performance characteristics of each. The eccentrically braced frame uses diagonal braces to provide lateral support like the concentrically braced frame does. The difference is in their orientation, the center lines of connecting members no longer connect at a common work point to eliminate applied moments. One end of the diagonal brace terminates at a link on a beam. This Link is designed to act much like the reduced section of beam in a moment frame. It is designed to yield before any other member or connection in the frame. It is this link that provides the ductility for the system. Figure 2.9 illustrates two common eccentrically braced frame layouts, and Figure 2.10 is a photograph that has an example of each.
Figure 2.9 Example of eccentrically braced frame layouts.
13


Figure 2.10 Building with an eccentrically braced frame structural system.
2.2.4. Buckling-Restrain Braced Frames
Buckling restrained braced frames are a special sub-class of the concentrically braced frame system. It uses opposing diagonal braces to resist lateral load just as the concentrically braced frame does. The difference is that the diagonal braces are a designed assembly versus a plain steel section. The brace assembly consists of a steel core that is treated with an unbonding material. This core is inserted inside of a hollow steel shell which is then filled with a mortar mixture. The purpose of the unbonding material is to allow the steel core to deform axially in tension, independently from the mortar and steel shell. In compression the mortar and steel shell increase compression capacity of the steel core such that the capacity of the diagonal brace is very similar when loaded in tension and compression. Figure 2.11 illustrates the configuration of a buckling restrained brace.
14


Steel Core
Figure 2.12 Buckling restrained braces installed in a building frame.
Tube
Tube
Unbonded Brace
Figure 2.11 Illustration of a buckling restrained brace.
Figure 2.12 shows a building the orientation of the buckling restrained braces. It them in an identical configuration as a concentrically braced frame.
Unbonding Material
15


CHAPTER III
RESEARCH PROGRAM
3.1 Scope of testing
Six types of connections were tested in a 220 kip capacity MTS testing machine under displacement control and resulting forces versus time and displacements. After each series of tests the failures of the samples were evaluated, and a new design generated to overcome the deficiencies of its predecessor. The difference between each type of connection was primarily geometric, or in the material used. For example some sample types were loaded concentrically with the load path through the specimen in a straight line. In others there was an eccentricity in the load path. Grade 50 steel plates were tested as were 46 ksi HSS tube sections loaded perpendicular to their wall. All yield plates were 6 long by 4 deep. The HSS sections used were 6 wall widths cut to 4 length. The 6 width for the yielding plate is based on the nominal 6 width of the CFS studs used in the system.
In each type of connection there were two variables that were modified between test samples. One was the thickness of the yielding plates or HSS tube sections, varying between 3/16 and 3/8 inch thick. The other variable was the size and shape of bushing used to facilitate the formation of a plastic hinge in the yield plate. The bushings used were either rectangular or circular in shape. Figure 3.1 shows an example of the different bushings used in testing. Four widths of rectangular bushings were used, 2, 2-3/4, 3 and 3-1/2. For the round bushing, 1-1/2 and 2-1/2 were the two diameters used.
16


Figure 3.1 Bushings used to generate plastic hinges in the yielding plate of the connection. From left to right. 1.5 round, 2.5 round, 2 rectangular, 2.75 rectangular, 3 rectangular, and 3.5 rectangular.
A brief description of the six tested connections is provided below.
3.1.1. A-Series Connection
The first sample connection was given the A series nomenclature, simply due to it being the first one. It was a proof of concept model that utilized the standard fabrication methods of fabricating cold formed steel components and welding those pieces together using a flux-cored welding process. The connection was made from a section of reinforced CFS stud, comprised of two studs nested together, simulating what would be a horizontal force collecting member in a panel. It was attached to a non-reinforced stud section representing the edge-stud of a panel. The two studs were welded together with a gusset plate. The yield plate was attached at the bottom of the edge-stud and welded to the end gusset plate. Figures 3.2 and 3.3 show what a typical A-Series connection looked like.
17


Yield Plate
Bushing
Figure 3.2 A-Series Connection.
18


Figure 3.4 is the detail of the weld configuration between the side gusset plates and the yielding plate. The bottom fillet weld was on all samples, and one-half of the samples had an additional fillet weld on the upper corner of the yield plate to the side of the gusset.
Figure 3.4 Detail of welds between gusset plate and yielding plate.
A notch was cut in the end of the reinforced stud to allow for access of a torque wrench to the 3/4 bolt that would attach the connection to the column. In this connection 3/8 thick yield plates were used. Eighteen samples were tested with 3.5, 2.75, and 2 rectangular bushings; and 1.5 circular bushing. Virtually all welds were made using a flux-cored welding process.
3.1.2. T-Series Connection
The T-Series connection utilizes 6x6 inch HSS sections cut to 4 lengths. 6x6 HSS tubes were used as the columns in this type of construction. Two versions were developed, where the assembly between the stud and the HSS tube was slightly different. In the version 1 connection, the flange of the CFS track was extended down along the side of the HSS tube. The stud bottom was welded to the face of the HSS tube. Figures 3.5, and 3.6 illustrate a typical version 1 of a T-series connection.
19


Figure 3.5 T-Series Connection, version 1. The bold lines indicate fillet weld locations.
Figure 3.6 T-Series Connection, version 1
20


Version 2 of the T-series connection eliminated the flange extension on the track. Both the stud and track terminated at the face of the HSS section. Gusset plates were used to connect the stud in track section to the HSS section. Figures 3.7 and 3.8 show a typically T-series, version 2 connection.
Figure 3.7 T-Series Connection, version 2
21


Figure 3.8 T-Series Connection, version 2
3.1.3. E-Series Connection
The E-Series Connection also utilizes a HSS tube section connected to a CFS member, comprised of a stud in track. It was determined that in some panel configurations a concentric loading path from the horizontal member through the attachment bolt to the column was not possible. This connection was developed to test the effects an eccentricity would have on the assembly. The track section of CFS extends down an open end of the HSS section 5 and the stud section terminates at the face. The assembly was welded on the inner perimeter of the HHS to the track, along the outside of the track to the HSS on the sides, and across the top between the stud and tube. Figures 3.9 and 3.10 show a typical E-series connection.
There are 3 samples labeled with a PE designation. They are an E-series design, but welded by metal inert gas (MIG) process, to verify the performance against those made by a flux-cored welding process.
22


Stud ends at top of HSS
1 1 1 1 i 1 i t i r i i i i i i

5 *
Back and sides of track continue 5"
Figure 3.9 E-Series Connection
Figure 3.10 E-Series Connection
23


3.1.4. UC-Series Connection
The UC-series connection was developed to maximize the use of CSF, and to eliminate shortcomings found during the testing of the A-series, which are discussed in chapter 4 of this work. A U shaped CFS gusset was used to secure the yield plate to the assembly. It wrapped around the yield plate and across the flanges of the edge-stud and continued up along the reinforced stud. There is a single tack weld in the center of the yield plate to the edge-stud to keep it in place for fabrication. The C in the designation indicates the load path is concentric. The reduced CFS section is extended into the unreinforced stud and welded to the flange to stiffen the assembly. A cut out in the reduced section of the reinforced stud was made to allow for access to the 3/4" inch bolt for installation. Figures 3.11 and 3.12 show atypical UC-series connection.
Figure 3.11 UC-Series Connection
24


Figure 3.12 UC-Series Connection
25


3.1.5. UE-Series Connection
The UE connection is identical in construction to the UC connection except that the reinforced stud is 1-1/4 off center from the hole for the connection to the column. The results in an eccentricity identical to the E-series connection. Figures 3.13 and 3.14 show a typical EE connection. There are three samples labeled with a PEE designation. They are an EE-series design, but welded using a MIG process to verify the performance against those made by using the flux-cored process.
Figure 3.13 UE-Series Connection
26


Figure 3.14 UE-Series Connection
27


3.1.6. TN-Series Connection
The final connection tested was an adaptation of the T-series. A notch was cut from the face and side walls of the HSS section to accept a reinforced stud inserted 3 inches into the HSS through the top face. The stud was welded to the HSS section along the outside vertical edges of the stud. Figures 3.15 and 3.16 show atypical TN connection.
Figure 3.15 TN-Series Connection
28


Figure 3.16 TN-Series Connection
3.2. Testing procedure
All samples were tested in a 220 kip MTS testing machine, at the University of Colorado Denver (UCD) Structures Laboratory in Denver, CO, and subjected to the same cyclic protocol of progressively increasing tension and compression cycles. Displacement was the controlling variable and the resisting force developed was recorded by the MTS data acquisition system. A modified Consortium of Universities for Research in Earthquake engineering (CUREE) loading protocol was used to simulate the accumulated damage to a component or structure exposed to a ground motion. The CUREE protocol is based on a single large leading cycle followed by 2 to 6 smaller trailing cycles, usually 75% of the leading cycle displacement. The next leading cycle is an increase over the last leading cycle. In this investigation 0.2 inches was used as the primary step increase, in leading cycle displacement. Table 3.1 and shows the values programmed into the MTS and Figure 3.17 is a graph of displacement vs. time for this protocol.
29


Table 3.1 Modified CUREE Protocol
Step No. Cycles Displacement (inches) Frequency (Hz)
1 6 0.025 0.125
2 1 0.05 0.125
3 6 0.025 0.125
4 1 0.1 0.125
5 3 0.075 0.125
6 1 0.2 0.125
7 2 0.015 0.125
8 1 0.4 0.125
9 2 0.3 0.0625
10 1 0.6 0.0625
11 2 0.45 0.0625
12 1 0.8 0.0625
13 2 0.6 0.0625
14 1 1.0 0.0625
15 2 0.75 0.0625
16 1 1.2 0.0625
17 2 0.9 0.0625
18 1 1.4 0.0625
19 2 1.05 0.0625
20 1 1.6 0.0625
21 2 1.2 0.0625
22 1 1.8 0.04167
23 2 1.35 0.04167
24 1 2.0 0.04167
30


Figure 3.17 Graph of CUREE protocol, displacement vs. time.
The frequency of each cycle was determined by the physical capabilities of the MTS. It is the maximum frequency that can be obtained by the MTS for a given displacement while providing maximum performance. Too fast and the MTS is unable to keep up and reach a specified displacement before reversing direction. Too slow and the test time increases and becomes inefficient.
The purpose of using the CUREE protocol according to is to simulate the accumulated damage a component may experience in a seismic episode (Krawinkler et al. 2001).
31


Based on connection geometry, there were two different load paths through a specimen based on its geometry. The first was axially concentric through the specimen so no moment was introduced to the connection as shown in figure 3.18 and 3.19. The load path through the mounting bolt at the bottom of the sample is in line with the reinforced stud and continues up to the top mounting yoke of the MTS.
Figure 3.18 Test jig for concentrically loaded specimens.
32


Load cell
Mounting yoke
Loading bar
Test specimen
Simulated HSS mounting block
Mounting yoke Hydraulic ram
Figure 3.19 Photograph of a concentrically loaded sample in the MTS.
It was determined that in some circumstances a configuration of connection will be required where there would be a non-concentric load path through it. The reason for this is to allow access for tools to tighten the bolts that will secure panels to columns. It also allows for crossing bolts through a column for panels positioned perpendicular to each other at a column. As a result the load path through the mounting bolt through the reinforced stud is
33


offset by 1.25. Resulting in the second load path, an eccentric one. Figure 3.20 and 3.21 show the geometry of this loading configuration.
Figure 3.20 Test jig for eccentrically loaded specimens.
34


Figure 3.21 Photograph of an eccentrically loaded sample.
Bolts connecting the loading bar to the CFS reinforced stud on the top of the specimen were torqued to 350 ft-lb to prevent slippage. Depending on the sample, two or four % diameter A325 bolts were used to secure the sample. A single, % diameter A325 bolt torqued to 350 ft-lb was used to connect the sample to the simulated HSS mounting block. A bushing was installed on each side of the yielding plate, to facilitate the formation of a plastic hinge in the yielding plate.
35


CHAPTER IV
RESULTS
4.1. Description of outputs.
The MTS provided data on the displacement and applied force vs time for each sample. Using a custom program run in MATLAB, the data was extracted and three graphs for each sample were generated: displacement versus time, force versus time, and a force versus displacement. The force versus displacement graph, also known as a hysteresis plot, provides the best visualization of raw data to evaluate our samples. It graphically demonstrates how much a particular sample could deflect before it fails as well has the forces achieved at different displacements. The area within the loops of the graph are equivalent to the energy dissipated by the connection. Figure 4.1 shows typical graphs of displacement vs. time and force vs. time respectively.
36


Tost T4 HSS6*65 16 1 2x2-x4" PI Washor Single Gusset PI Displacement vs. Time Cyclic Tension Compression
05
A A
0 WvW'/^WvVW-11
Peak displacements -0 5 correlate with peak forces
50 too 1 ISO 200 Tme {MCI
250 300 350
Test T4 HSS6x6x5 16-1 '2x7x4" PI Washer Single Gusset PI Load vs. Tima* Cyclic Tension Compression
30 20 10 ; g o -10 20 30 40
50 IOO
150
Decreasing trend line of forces indicate onset of failure in connection
I Compression
"spikes indicate contact made with lower mounting block 2^0 300 ji in compression
Tm# (mc)
Figure 4.1 Typical graphs of displacement and force vs time.
Figure 4.1 also shows how peak displacements correlate with peak forces. As the test progresses and displacements continue to increase, there is a noticeable reduction in applied force for the given displacements. This is an indication that a mechanism of failure has begun in the connection. In this example two spikes can be seen in compression on the force graph. They correlate with the two largest compression displacements on the displacement graph. The test sample came in contact with the lower mounting block at these displacements. This is analogous to a panel coming in contact with a column during a lateral movement during an earthquake.
37


Using the same data and MATLAB program, a force versus displacement or hysteresis graph can be generated as well. Figure 4.2 shows a representative hysteresis graph.
Test T4 HSS6x6x5/16 1/2x2"x4" PI Washer Single Gusset PI Load vs. Displacement Cyclic Tension/Compression
Non-symmetric behavior in tension and compression
-1 l -0.5 o 0.5 1
Contact with Displacement (in)
bottom mounting block
Figure 4.2 Typical Load vs. displacement (hysteresis) graph.
In this graph one can also see where the connection came into contact with the bottom mounting block in the larger compression cycles. Another trend of note that can be observed is a non-symmetric behavior in the tension and compression cycles.
Because these samples are being moved with relatively large displacements, significant lateral displacements in some members of the connection can also be observed. Moment arm length between the edge of the bushing and the edge of the yielding plate or HSS changes as the geometry of the connection changes throughout a cycle. Figure 4.3 illustrates this change in geometry.
38


Figure 4.3 Change in dimension between walls of HSS during tension and compression
cycles.
In the case of a 2 bushing the undeformed moment arm is 2 on either side of the bushing where we are using a 6 long yielding plate. In a large displacement, the length of the moment arm perpendicular to the direction of force can be reduced by 0.5 which translates to a 25% reduction in moment arm length.
4.2. Analysis of Connections
Backbone curves were generated for the T, E, UC, UE, and TN families of connections. A backbone curve is an idealization of behavior of a connection based on the hysteresis graph. The backbone curve is made up of the linear elastic behavior of the
39


connection in small displacements, the ultimate strength it obtains in during a displacement, and its residual capacity at the maximum displacement. Figure 4.4 shows an example of a typical backbone curve.
Test T4 HSS6x6x5/16 1/2x2"x4" PI Washer Single Gusset PI Load vs. Displacement Cyclic Tension/Compression
30
20
10
0
O ra o _l -10
-20
-30
-40
-1 -0.5 0 0.5 1
Displacement (in)
Figure 4.4 Backbone curve overlaid on a hysteresis graph.
A backbone curve is a useful tool in evaluating and comparing the performance of one connection to another. This section will provide various analysis of connections based on their backbone curves.
4.2.1. A-series.
There was a discovery-learning process on how to obtain the best possible data from our samples, during the testing of the A-series of connections. The result was modifications to the physical set up of the test specimen in almost every test in this series. Local buckling in the unreinforced stud combined with the lateral outward movement in the legs of the cut-
40


out of the reinforced stud section, resulted in premature failure of the connection before significant deformation of the yielding plate was achieved. This is demonstrated in Figure 4.5. In subsequent connection families using CFS and yielding plates, the vertical flanges of the unreinforced stud are reinforced to eliminate this issue.
Figure 4.5 Example of local buckling of the unreinforced stud flanges, bending of top bushing, and failure of the weld between the gusset and the edge of the yielding plate.
The use of 3/8 thick bushings was also found to be insufficient because they would also bend in the tension cycle along with the yielding plate. This results in only one yield line in the yielding plate located along the centerline vs. the preferred result of two yield lines, one on either side of the bushing. Figure 4.6 illustrates the permanent deformation of the top bushing.
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Figure 4.6 Illustration of permanent deformation in 3/8 top bushing. Deformation shown in
the photograph occurred in the tension cycle.
The lessons learned with this series were used to modify and improve future test specimens and also resulted in modification of the test procedure to reduce experimental uncertainty in the data of following tests. The most significant improvement was the development of wedges to remove mechanical slack from the system between the 2 inch diameter round pins, the mounting yokes, and the simulated HSS column piece. Figure 4.7 illustrates the horizontal shift in the data on a hysteresis graph.
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Test A10 2 3/4" Plate Washer (Weld 3)
Load vs. Displacement Cyclic Tension/Compression
Figure 4.7 Example of horizontal shift in data to gaps between mounting pin and yoke
without the use of wedges.
Figure 4.8 is a photograph of the wedges that were fabricated to remove mechanical slack from the system. They were constructed from a 6 long by 1 thick piece of steel plate. It was cut diagonally through the thickness of the plate down its length.
Figure 4.8 Wedges used to remove mechanical slack in top and bottom mounting yokes.
The wedges were used in the top and bottom mounting yokes. Figure 4.9 shows their location in the lower mounting assembly.
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-Simulated HSS
Pin
Wedges
Lower mounting yoke
Figure 4.9 Wedges installed in lower mounting assembly.
After the wedges were utilized, the horizontal shift in data was eliminated. Figure 4.10 is a hysteresis plot of the first test run after wedges were installed. Note the lack of horizontal shift compared to that shown in Figure 4.7 previously. The wedges also had a secondary benefit of eliminating rotation around the mounting pin in the yoke. This more closely simulated conditions a connection would be under in a CFS Panel.
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Test A18 -1.5" Round Washer (Weld 3/4)
Load vs. Displacement Cyclic Tension/Compression
Displacement (in)
Figure 4.10 Use of wedges eliminated horizontal shift in the graph. Compare to graph shown
in figure 4.7.
Due to the variability in test setup from one specimen to the next, and the poor performance of the connection without external stabilization back bone curves were not generated for this family of connections. The lessons learned from this series were used to develop the UC and UE connections, as well as standardize the testing procedure.
Table 4.1 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the A-series. A summary of the primary failure modes is also included. Side gusset plate buckling was the primary failure mechanism for samples A1 to A11. Once the local buckling was controlled through the use
45


of steel plates and clamps, failures in the yielding plates and in the welds between the gusset plate and yielding plates became the controlling failure mechanism.
Table 4,1 A-Series summary of tension, displacement, and failure modes.
Sample # Test Name Max Force Displacement Failure Mode
Tens. (Kip) Comp. (Kip) Tens. (ini Comp. fin)
A1 3/8" PL, 3.5" Square Bushing 19.3 -17.9 1.2 -1.2 Side gusset plates buckled in compression, stud flanges buckled
A3 3/8" PL, 2" Square Bushing 14.7 -14.3 0.8 -0.6 Gusset pi buckled in compression, gusset fractured in tension
A4 3/8" PL, 2" Square Bushing 15.8 -14.7 0.8 -0.8 Gusset pi buckled in compression
A5 3/8" PL, 2.75" Square Bushing 17.8 -16.7 0.6 -0.6 Gusset pi buckled in compression
A6 3/8" PL, 3.5" Square Bushing 16.8 -19.9 0.4 -0.4 Gusset pi buckled in compression
A7 3/8" PL, 2.75" Square Bushing 19.7 -17 1 -1 Gusset pi buckled in compression, then fractured in tension
A8 3/8" PL, 2" Square Bushing 16.5 -13.2 0.8 -0.8 Gusset pi buckled in compression
A9 3/8" PL, 2.75" Square Bushing 19 -18.9 0.6 -0.6 Gusset pi buckled in compression at 18k when buckling restraint disengaged
A10 3/8" PL, 2.75" Square Bushing 17.4 -16.7 0.4 -0.4 Gusset pi buckled in compression when buckling restraint disengaged
All 3/8" PL, 2.75" Square Bushing 20.1 -18.2 1 -1 Gusset buckled in compression at contact with loaf, yield pi fractured at edge of pi washer in tension, gusset to stud weld failed
A12 3/8" PL, 2" Square Bushing 15.9 -24.5 1.2 -1.2 Yield pi fractured at edge of pi washer, gusset to stud weld failed, gusset to yield plate weld fractured
A13 3/8" PL, 3.5" Square Bushing 27.8 -21.6 1 -1 failure at bottom of slot welds
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A14 3/8" PL, 3.5" Square Bushing 24.9 -22.8 1 -1 Stud flange buckled and stud to gusset welds fractured, yield pi fractured at edge of pi washer
A15 3/8" PL, 3.5" Square Bushing 26 -22.2 1 -1 Stud flange buckled and stud to gusset welds fractured, yield pi fractured at edge of pi washer
A16 3/8" PL, 2.75" Square Bushing 20 -24.5 1 -1 Stud flange buckled and stud to gusset welds fractured, yield pi fractured at edge of pi washer
A17 3/8" PL, 2" Square Bushing 16.6 -26.9 1.2 -1.2 Stud flange buckled and stud to gusset welds fractured, yield pi fractured at edge of pi washer
A18 3/8" PL, 1.5" Round Bushing 14.2 -13.7 1.2 -1.2 Yield pi to gusset weld fractured
4.2.2. T-series
The backbone curves in Figures 4.11 through 4.15 show the envelope of behavior for the T-series connections. They compare behavior of the connections by looking at how the different variables of either thickness of the HSS tube wall, or dimension and shape of bushing affects the results. Figures 4.11 and 4.12 compare the behavior of bushing geometry affects for a particular thickness.
The larger bushings yield larger forces but smaller displacement capacity. The results are consistent for the two thicknesses of HSS tube tested. A small horizontal shift in the T1 and T2 test results can be observed at the origin of the graph. The wedges discussed earlier were implemented as a standard test procedure afterwards.
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Force (Kip)
T-Series. 1/4" thick HSS
30.00 3.5" square bushing
10 00 2' rectangle bushing
1.5" rou nd bushin g DO --T2
00 -1. 50 -1. 00 -0 50 r o Lo 50 1.00 1. 50 2.(

-30.00
Displacement (in)
Figure 4.11 T-series back bone curve for 1/4 thick HSS section. Comparing 3.5 square, 2
rectangular, and 1.5 round bushings.
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Figure 4.12T-series back bone curve for 5/16 thick HSS section. Comparing 3.5 square, 2
rectangular, and 1.5 round bushings.
Figures 4.13, 4.14, and 4.15 compare the behavior HSS wall thickness affects for a particular bushing geometry. Higher forces are able to be resisted for thicker HSS sections. This is demonstrated for all three bushings types tested for this series, 3.5 square, 2 rectangular, and 1.5 round. It was observed that the 1.5 round bushing was able to achieve more ductility in the smaller 1/4 tube than in the 5/16 tube section. The opposite is the case when comparing results for the 3.5 square and 2 rectangular bushings. The thicker 5/16 tube was able to withstand greater displacement.
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Force (kip)
T-Series. 3.5" Square Bushing
45.00 |
-35.0011
Displacement (in)
Figure 4.13 T-series back bone curve for 3.5 square bushing. Comparing 1/4 and 5/16
thick HSS.
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Force (kip)
T-Series. 2" Rectangular Bushing
30 |
5/16" HSS
-20
---30 1
Displacement (in)
Figure 4.14T-series back bone curve for 2 rectangular bushing. Comparing 1/4 and 5/16
thick HSS.
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T-Series. 1.5" Round Bushing
Figure 4.15T-series back bone curve for 1.5 round bushing. Comparing 1/4 and 5/16
thick HSS.
Table 4.2 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the T-series. A summary of the primary failure modes is also included. In the version 1 of the connection the CFS of the extended flange of the stud fractured or had large local buckling effects. This eliminated the version T-series of connection from further review. The version 2 connections using the side gusset plates performed better. While local buckling was observed in the gussets and the stud the failure mechanism was in the HSS, either in the comers of the tube or along the bushing. While the 3.5 square bushing with the 5/16 thick HSS tube resulted in the largest force observed in testing, the displacements for samples with the square and rectangular shape were insufficient. The 1.5 round bushing provided sufficient force resistance and
52


displacement in the 1/4 and 5/16 thick HSS tubes. The 3/16 in thick HSS tube was determined to be too thin to provide sufficient force resistance in a connection.
Table 4,2 T-Series summary of tension, displacement, and failure modes.
Sample # Test Name Max Force Displacement Failure Mode
Tens. (Kip) Comp. (Kip) Tens. iin) Comp. (ini
T1 1/4" HSS, 3.5" Square Bushing 23 -17.6 0.4 -0.4 Buckle and fracture at CFS extended flange
T2 1/4" HSS, 1.5" Round Bushing 12.1 -9.3 1.6 -1.6 Side gussets buckled, HSS fractured at round washer
T3 1/4" HSS, 2" Square Bushing 16 -11 0.8 -0.8 Side gussets buckled, HSS fractured at washer pi
T4 5/16" HSS, 2" Square Bushing 23.4 -17 1 -1 Side gussets buckled, HSS fractured at comers
T5 5/16" HSS, 1.5" Round Bushing 19.8 -13 1.2 -1.2 Side gussets buckled, HSS fractured at comers
T6 5/16" HSS, 3.5" Square Bushing 40.4 -27.3 0.8 -0.8 HSS fractured at washer pi
T7 5/16" HSS, 3.5" Square Bushing 41 -27.9 0.6 -0.6 HSS fractured at washer pi
T8 5/16" HSS, 2" Square Bushing 24.5 -16 0.8 -0.8 Side gussets buckled, HSS fractured at washer pi
T9 5/16" HSS, 1.5" Round Bushing 20.5 -12 1.2 -1.2 Side gussets buckled, HSS fractured at comers
4.2.3. E-series.
The results from the A and T-series tests led the elimination of all but two bushings for the remaining tests. A 3 rectangular bushing is used to study the behavior of the connections as the upper limit of force resistance, and the 1.5 round bushing is used to study the lower bounds. The 3.5 square bushing was determined to be too large and insufficient
53


ductility was achieved. The intermediate sizes of 2.75 and 2 rectangular bushing only provided marginal data in making decision for future connections design or analysis.
Like the T-series connections Figures 4.16 through 4.20 examines the behavior of the E-series connections by comparing bushing geometry for a particular HSS thickness and the behavior due to thickness for a particular bushing geometry. We see very similar behavior to the T-series. The larger bushing provides greater force resistance and the smaller one allows greater ductility. Thicker HSS sections provide more force resistance than thinner for the same size bushing. The ductility is fairly consistent for a particular bushing regardless of HSS thickness.
E-Series. 3/16" HSS
Figure 4.16 E-series back bone curve for 3/16 thick HSS section. Comparing 3 rectangular, and 1.5 round bushings.
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Force (kip)
E-Series. 1/4" HSS

Figure 4.17 E-series back bone curve for 1/4 thick HSS section. Comparing 3 rectangular,
and 1.5 round bushings.
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Force (kip)
E-Series. 5/16" HSS
---30 1
Displacement (in)
Figure 4.18 E-series back bone curve for 5/16 thick HSS section. Comparing 3 rectangular, and 1.5 round bushings.
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Force (kip)
E-Series with 3" rectangular bushings
E4
E5
E6
E7
E8
E9
PEI
PE2
Figure 4.19 E-series back bone curve for 3 rectangular bushing. Comparing 3/16, 1/4,
and 5/16 thick HSS.
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E-Series. 1.5" Round Bushings
El
E2
E3
E10
Ell
E12
E15
Figure 4.20 E-series back bone curve for 1.5 round bushing. Comparing 3/16, 1/4, and
5/16 thick HSS.
Table 4.3 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the E-series. A summary of the primary failure modes is also included. Three primary failures were observed in this series of connection. Fracture in the CFS of the stud above the weld connecting the stud to the top of the HSS and in its flanges due to bending from the eccentric loading was observed in 4 samples. Fracture of the HSS tube in the comers, along the edges of the bushing or both was the primary mode of failure.
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Table 4.3 E-Series summary of tension, displacement, and failure modes.
Sample # Test Name Max Force Displacement Failure Mode
Tens. (Kip) Comp. (Kip) Tens. iin) Comp. (ini
El 3/16" HSS, 1.5" Round Bushing 8.3 -3 1.4 -1.4 Local and global stud buckling after contact with loaf, HSS tore at washer
E2 1/4" HSS, 1.5" Round Bushing 14.1 -6 1.4 -1.4 Local and global stud buckling after contact with loaf, HSS tore at washer and comers
E3 5/16" HSS, 1.5" Round Bushing 18.9 -12 1.4 -1.2 Local and global stud buckling after contact with loaf, HSS tore at washer and comers, track flange tear adj to HSS top comers
E4 3/16" HSS, 3" Square Bushing 13.3 -5.9 0.6 -0.6 HSS fractured at edge of 3" plate
E5 1/4" HSS, 3" Square Bushing 21.8 -15 0.8 -0.8 HSS fractured at edge of 3" plate
E6 5/16" HSS, 3" Square Bushing 27.8 -22.3 0.6 -0.4 Stud wall fractured above stud to HSS weld
E7 3/16" HSS, 3" Square Bushing 13.4 -6.5 0.6 -0.6 HSS tube fractured at edge of 3" plate
E8 1/4" HSS, 3" Square Bushing 22.1 -14 0.8 -0.8 HSS tube fractured at edge of 3" plate
E9 5/16" HSS, 3" Square Bushing 28.6 -21.5 0.6 -0.6 Local and global stud buckling, the Stud wall fractured above stud to HSS weld
E10 3/16" HSS, 1.5" Round Bushing 8 -3 1.6 -1.4 HSS tearout at 1.5" round washer
Ell 1/4" HSS, 1.5" Round Bushing 13.6 -7 1.4 -1.2 HSS tearout at 1.5" round washer, HSS bot comers cracked and fractured
E12 5/16" HSS, 1.5" Round Bushing 18.9 -12 1.4 -1.4 HSS tearout at 1.5" round washer, HSS cracked at bot comers, stud to HSS weld cracked, stud buckled after contact w/ loaf
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PEI 5/16" HSS, 3" Square Bushing 29.8 -20.5 0.6 -0.6 Stopped test when upper test plate began to bend, fractures visible in stud
PE2 5/16" HSS, 3" Square Bushing 28.5 -21.7 0.6 -0.6 Stud metal tore adjacent to weld at top of HSS
PE3 5/16" HSS, 1.5" Round Bushing 19.5 -12.5 1.4 -1.4 HSS tore at washer and fractured at bottom comers
4.2.4. UC-series.
While both the T and E-series of connection eliminated the local buckling issues associated with the A-series, the complexities of integrating them with a CFS panel ultimately led to their rejection. The development of the UC and UE connections was to maximize the use of CFS and inexpensive steel plate for the yielding mechanism. Figures 4.21 through 4.25 show the behavior of the UC-series connection. Only the 3 and 1.5 round bushings were used 1/4, 5/16, and 3/8 yielding plates were evaluated. The global behavior of this followed that of the HSS style connections. Large bushings and thicker plates provide more force resistance than smaller bushings and thinner plates. Small bushings allow for more ductility but ductility is relatively constant for a particular bushing across the tested thicknesses of plate. One item of note is that PUC2 and PUC3 had similar performance to UC5 in displacement and force resistance but a different shape in their backbone curves. No determination has been found for this. They were constructed by a different manufacturer to test MIG vs flux-cored welding. Only 1 of 4 welds securing the gusset to the unreinforced stud was observed with welds were observed to have any indication of failure in PUC3. This was determined to have negligible effect on the overall performance of that sample.
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Force (kip)
UC-Series. 1/4" Plate
30 |
20
--30 1
Displacement (in)
Figure 4.21 UC-series back bone curve for 1/4 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings.
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Force (kip)
UC-Series. 5/16" Plate

Figure 4.22 UC-series back bone curve for 5/16 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings.
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Force (kip)
2
UC-Series. 3/8" Plate
30 20 10
-1.5 -1 -0.5
-20
---30 1
Displacement (in)
p 3" 1 Rectangular
1.5" Round

.5 : L 1. .5 2


UC6
PUC1
PUC2
PUC3
UC5
Figure 4.23 UC-series back bone curve for 3/8 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings.
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Force (Kip)
UC-Series 3" Rectangular Bushing
Displacement (in)
UC1
UC4
UC5
PUC1
PUC2
Figure 4.24 UC-series back bone curve for 3 rectangular bushing. Comparing 1/4, 5/16,
and 3/8 thick yielding plate.
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UC-Series. 1.5" Round Bushing
30 |
3/8" PL
-20
--30 1
Displacement (in)
Figure 4.25 UC-series back bone curve for 1.5 round bushing. Comparing 1/4, 5/16, and
3/8 thick yielding plate.
Table 4.4 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the UC-series. A summary of the primary failure modes is also included. The primary failure observed was a fracture at the 90 degree bend in the U-shaped gusset. Only one sample had complete yield plate fracture without U-gusset fracture.
Table 4,4 UC-Series summary of tension, displacement, and failure modes.
Sample # Test Name Max Force Displacement Failure Mode
Tens. (Kip) Comp. (Kip) Tens. liai Comp. liai
UC1 1/4" PL, 3" Square Bushing 16.9 -9.5 1.2 -l Beveled stud edges buckled, yield pi fractured at washer pi edges
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UC2 1/4" PL, 1.5" Round Bushing 10.6 -6 1.4 -1.4 Beveled stud edges buckled, yield pi fractured at washer, U-shape pi fractured at comer
UC3 5/16" PL, 1.5" Round Bushing 13.7 -8 1.2 -1.2 Fractured U-shape pi at comer, yield pi began fracturing at bolt CL
UC4 5/16" PL, 3" Square Bushing 27 -14.5 1 -1 Yield pi fractured at bushing edges
UC5 3/8" PL, 3" Square Bushing 28.3 -26 0.6 -0.6 Fractured U-shape pi at comer
UC6 3/8" PL, 1.5" Round Bushing 19.4 -14 1.4 -1.4 Fractured U-shape pi at comer
PUC1 3/8" PL, 3" Square Bushing 22.7 -22.5 0.4 -0.4 Fractured U-shape pi at comer
PUC2 3/8" PL, 3" Square Bushing 23.9 -22.2 0.4 -0.4 Fractured U-shape pi at comer
PUC3 3/8" PL, 1.5" Round Bushing 19.9 -12 1.8 -1.8 Weld failure at gusset/bot stud, fractured U-shape pi at comer, punch-out of 3/8" yield pi at round washer
4.2.5. UE-series.
Figures 4.26 through 4.29 show almost identical results to the UC connections.
Based on results previously, the 1/4 thick plate was eliminated due to the lower force resisting capacity. Only 5/16 and 3/8 were evaluated using a 3 rectangular bushing and a 1.5 round busing. The global behavior of this connection followed the pattern of the previous series. The 3 rectangular bushing provides more force resistance and less ductility while the smaller 1.5 round bushing allows for more ductility but less force resistance. Thicker yielding plates can generate higher force resistance for a specific bushing size but appears to have less effect on the overall ductility, especially in respect to 1.5 round bushing.
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Force (kip)
UE-Series. 5/16" Yield Plate.
30 |
---30 1
Displacement (in)
Figure 4.26 UE-series back bone curve for 5/16 thick yielding plate. Comparing 3
rectangular, and 1.5 round bushings.
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Fgsce (kip)
UE-Series. 3/8" Yield Plate.
30.00 |
3" Rectangular
20.00 10.00
1.5" Round
00 -1.50 -1.00 -0.50 0/00 0.50 1.00 1.50 2.00
UE1
UE2
-30.0911 Displacement (in)
Figure 4.27 UE-series back bone curve 3/8 thick yielding plate. Comparing 3 rectangular,
and 1.5 round bushings.
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Force (kip)
UE-Series. 3" Rectangular Bushing.
30 |
3/8" PL
---30 1
Displacement (in)
Figure 4.28 UE-series back bone curve for 3 rectangular bushing. Comparing 5/16, and
3/8 thick yielding plates.
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UE-Series. 1.5" Round Bushing.
30.00 |
-20.00
-30.0011
Displacement (in)
Figure 4.29 UE-series back bone curve for 1.5 round bushing. Comparing 5/16, and 3/8
thick yielding plates.
Table 4.5 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the UC-series. A summary of the primary failure modes is also included. The only failure observed was a fracture at the 90 degree bend in the U-shaped gusset. The eccentricity in the connection did not contribute to any failure in the connection nor did it significantly decrease capacity or ductility. This connection has demonstrated the most promise to be integrated with a panel for construction, based on geometry, materials used, and performance, if the U-shaped gusset fracture can be eliminated as a failure mode.
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Table 4.5 UE-Series summary of tension, displacement, and failure modes.
Sample # Test Name Max Force Displacement Failure Mode
Tens. (Kip) Comp. (Kip) Tens. iin) Comp. (ini
UE1 3/8" PL, 1.5" Round Bushing 19 -16.1 1.2 -1.2 Fractured U-shape pi at comer
UE2 3/8" PL, 3" Square Bushing 23.8 -23.7 0.4 -0.4 Fractured U-shape pi at comer
UE3 5/16" PL, 1.5" Round Bushing 13.4 -8 1.2 -1.2 Fractured U-shape pi at comer
UE4 5/16" PL, 3" Square Bushing 22.3 -16 0.8 -0.8 Fractured U-shape pi at comer
4.2.6. TN-Series.
The TN-series of connections was developed to explore the behavior of a connection using an HSS section that had a portion of its surface removed so that a CFS stud could be inserted through and welded in place. Only 1/4 thick HSS was tested for this series. Figure 4.30 shows the response for the 3 square and 1.5 round bushings. The behavior is similar to the T and E-series.
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TN-Series. 1/4" HSS with 1.5" round and 3" square bushings.
30.00 |
-20.00
-30.0011
Displacement (in)
Figure 4.30 TN-series back bone curve for 1/4 thick HSS section. Comparing 3 rectangular, and 1.5 round bushings.
Table. 4.6 Summarizes the results for the TN connections. The singular failure mode was fracture of the HSS tube along the edge of the bushing. While the performance of this connection is marginally better in terms of force resistance and ductility, the difficulty in integrating this design with panel construction is sufficient to eliminate it as a design for further study as with the T and E-series connections.
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Table 4.6 TN-Series summary of tension, displacement, and failure modes.
Sample # Test Name Max Tens. (Kip) Force Como. (Kip) Displa Tens. iin) cement Como. (ini Failure Mode
TNI 1/4" HSS, 1.5" Round Bushing 11.4 -7 1.4 -1.4 HSS fractured at edge of bushing
TN2 1/4" HSS, 3" Square Bushing 20.8 -12.6 0.6 -0.6 HSS fractured at edge of bushing
TN3 1/4" HSS, 1.5" Round Bushing 11.6 -6.4 1.4 -1.4 HSS fractured at edge of bushing
TN4 1/4" HSS, 3" Square Bushing 20.5 -12.7 0.6 -0.6 HSS fractured at edge of bushing
TN5 1/4" HSS, 1.5" Round Bushing 11.4 -6.5 1.4 -1.4 HSS fractured at edge of bushing
TN6 1/4" HSS, 3" Square Bushing 19.8 -12.5 0.6 -0.6 HSS fractured at edge of bushing
4.3. Theoretical vs experimental load values.
This section discuss the theoretical values calculated for forces applied to obtain plastic hinges in a yield plate. Figure 4.32 shows the concept of a plastic hinge forming at the edge of a bushing in a yielding plate.
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Full Text

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i EXPERIMENTAL PROGRAM FOR SEISMIC CONNECTIONS TO ADD DUCTILITY TO COLD FORMED STEEL PANELS by BRIAN SCOTT WILSON B.S., University of Florida 1997 M.S., University of Missouri, Rolla 2002 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment Of the requirements of the degree of Master of Science Civil Engineering Program 2017

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ii This thesis for the Master of Science degree by Brian Scott Wilson has been approved for the Civil Engineering Program by Kevin L. R ens, Chair Frederick R. Rutz Carnot L. Nogueira Date: July 29, 2017

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iii W ilson, Brian Scott (M.S., Civil Engineering) Experimental Program for Connections to Ad d D uctil ity to Cold formed Steel P anels for U se in S eismic A pplications Thesis directed by Associate Professor Frederick R. Rutz Advisor ABSTRACT The purpose of this work is to explore connections that will perform elastically under normal loading conditions but will behave plastically when subjected to the higher forces experienced during an earthquake. These connections are vital to a framing sys tem, and must provide sufficient ductility and strength for the cold formed steel ( CFS ) building to remain standing throughout a seismic event. They must be economical to produce, and allow for ease of construction in the field. The concept of using a yi elding plate to add ductility to a connection is examined through the fabrication and testing of six different families of connections. The connection families were developed sequentially after lessons were learned from prior series. Each connection fam i ly utilized either small hot rolled steel plate or a short section of hollow structural steel ( HSS ) tube to provide th e ductility in the connection. All connections were load tested cyclically and were subjected to a protocol of progressively increasing p ositive and negative displacements until the specimen failed. Failure mechanism, ultimate load capacity, and displacement were all evaluated to determine the suitability of each type of connection for further study, modification, rejection, or acceptance. The form and content of this abstract are approve d. I recommend its publication. Approved: Frederick R. Rutz

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iv DEDICATION I dedicate my thesis work to my wife Gina who has supported me throughout this process of going back to school and changing careers. She made this all possible by giving me her full loving, and enthusiastic permission to embark upon this life changing adventure we have been on. To my sons, Jacob and Lucas who are growing into fine young men. Your assistance at home when I h ave been gone has made it possible for me to focus on the business at hand. To my parents whose support throughout the years has allowed me to live a charmed life. The adventures you gave me in childhood, lead me to continue seeking them

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v ACKNOWLEDGEMENTS I cannot express the gratitude I have to Dr. Fred Rutz for his mentorship, advice, and participation on this project. I have truly enjoyed working closely with him in the lab There are few indivi duals as dedicated to developing young ( and not so young) professionals as this man. I want to thank and offer my appreciation to Dr. Kevin Rens and Dr. Carnot Nogueira, for their participation and service as member of my examination committee. This work would not be possible without the suppor t of J.R. Harris & Company. I want to thank Jim Harris his for the amazing opportunity to actively contribute to his outstanding organization. To Gene Stevens for freely sharing his knowledge and enthusiasm for this research. And to Holly Janowicz for her major contribution in analyzing the data and cheerfully a nswering my numerous questions throughout this project A special thanks to Michael Lastowski co founder of Prescient for allowing me to participate in research and development of this concept. His entrepreneurial spirit and enthusiasm is infectious. To Jac Corless and Tom Thuis in providing outstanding support in the execution of schedule could not have been possible without their help.

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vi TABLE OF CONTENTS CHAPTER I ................................ ................................ ................................ .............................. 1 1.1. Background ................................ ................................ ................................ .................... 1 1.2. Scope of Investigati on ................................ ................................ ................................ .... 5 CHAPTER II ................................ ................................ ................................ ............................. 6 2.1. Why seismic loads are considered in design ................................ ................................ .. 6 2.2. Systems in steel construction to resist lateral forces ................................ ...................... 9 2.2.1. Concentrically Braced Frames ................................ ................................ .............. 10 2.2.2. Moment Resisting Frames ................................ ................................ .................... 11 2.2.3. Eccentrically Braced Frames ................................ ................................ ................ 13 2.2.4. Buckling Restrain Braced Frames ................................ ................................ ........ 14 CHAPTER III ................................ ................................ ................................ ......................... 16 3.1 Scope of testing ................................ ................................ ................................ ............. 16 3.1.1. A Series Connection ................................ ................................ ............................. 17 3.1.2. T Series Connection ................................ ................................ .............................. 19 3.1.3. E Series Connection ................................ ................................ .............................. 22 3.1.4. UC Series Connection ................................ ................................ .......................... 24 3.1.5. UE Series Connection ................................ ................................ ........................... 26 3.1.6. TN Series Connection ................................ ................................ ........................... 28 3.2. Testing procedure ................................ ................................ ................................ ......... 29

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vii CHAPTER IV ................................ ................................ ................................ ......................... 36 4.1. Description of outputs. ................................ ................................ ................................ 36 4.2. Analysis of Connections ................................ ................................ .............................. 39 4.2.1. A series. ................................ ................................ ................................ ................ 40 4.2.2. T series ................................ ................................ ................................ .................. 47 4.2.3. E series. ................................ ................................ ................................ ................. 53 4.2.4. UC series. ................................ ................................ ................................ .............. 60 4.2.5. UE series. ................................ ................................ ................................ .............. 66 4.2.6. TN Series. ................................ ................................ ................................ ............. 71 4.3. Theoretical vs e xperimental load values. ................................ ................................ ..... 73 CHAPTER V ................................ ................................ ................................ .......................... 81 5.1. Lessons Learned. ................................ ................................ ................................ .......... 81 5.2. Recommendations for further investigation ................................ ................................ 81 REFERENCES ................................ ................................ ................................ ....................... 83 APPENDIX A. ................................ ................................ ................................ ........................ 85 A.1 A series samples ................................ ................................ ................................ .......... 86 A.2 T series samples ................................ ................................ ................................ ......... 104 A.3 E series samples ................................ ................................ ................................ ......... 113 A.4 UC series samples ................................ ................................ ................................ ...... 125 A.5 UE series samples ................................ ................................ ................................ ...... 131 A.6 PUC series samples ................................ ................................ ................................ .... 135

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viii A.7 PE series samples ................................ ................................ ................................ ....... 138 A.8 TN series samples ................................ ................................ ................................ ...... 141 APPENDIX B. ................................ ................................ ................................ ...................... 147 B.1. A Series Graphs ................................ ................................ ................................ ........ 148 B.2 T Series Graphs ................................ ................................ ................................ .......... 182 B.3 E Series Graphs ................................ ................................ ................................ .......... 200 B.4 UC Series Graphs ................................ ................................ ................................ ....... 230 B.5 UE Series Graphs ................................ ................................ ................................ ....... 248 B.6 TN Series Graphs ................................ ................................ ................................ ....... 256

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ix LIST OF FIGURES FIGURE Figure 1.1. Example of typical panel and column in construction. ................................ ......... 2 Figure 1.2 Location of Connections on a typical CFS Panel ................................ ................... 3 Figure 1.3 Concept of yielding plate connection to HSS column. Showing compression and tension cycle. ................................ ................................ ................................ ............................. 4 Figure 2.1 Aftermath of San Francisco, CA earthquake, 1906 ................................ ................. 7 Figure 2.2 Damage to Venice high school 1933. ................................ ................................ ..... 7 Figure 2.3 Destroyed building after earthquake in Loma Prieta, CA 1989. (Nikitin 1989) .... 8 Figu re 2.4 Damaged parking structure after the Northridge earthquake, 1994. (Celebi n.d.) 9 Figure 2.5 Examples of concentrically braced frames. ................................ ........................... 10 Figure 2.6 A connection in a concentrically braced frame. ................................ ................... 11 Figure 2.7 Layout of a moment frame. ................................ ................................ .................. 12 Figure 2.8. Typical moment frame connection showing the reduced beam section. ............. 12 Figure 2.9 Example of eccentrically braced frame layouts. ................................ ................... 13 Figure 2.10 Building with an eccentrically braced frame structural system. ......................... 14 Figure 2.11 Illustration of a buckling restrained brace. ................................ .......................... 15 Figure 2.12 Buckling restrained braces installed in a building frame. ................................ .. 15 Figure 3.1 Bushings used to generate plastic hinges in the yielding plate of the connection. ................................ ................................ ................................ ............... 17 Figure 3.2 A Series Connection. ................................ ................................ ............................. 18 Figure 3.3 A Series Connection ................................ ................................ .............................. 18

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x Figure 3.4 Detail of welds between gusset plate and yielding plate. ................................ ..... 19 Figure 3.5 T Series Connection, version 1. The bold lines indicate fillet weld locations. .... 20 Figure 3.6 T Series Connection, version 1 ................................ ................................ ............. 20 Figure 3.7 T Series Connection, version 2 ................................ ................................ ............. 21 Figure 3.8 T Series Connection, version 2 ................................ ................................ ............. 22 Figure 3.9 E Series Connection ................................ ................................ .............................. 23 Figure 3.10 E Series Connection ................................ ................................ ............................ 23 Figure 3.11 UC Series Connection ................................ ................................ ......................... 24 Figure 3.12 UC Series Connection ................................ ................................ ......................... 25 Figure 3.13 UE Series Connection ................................ ................................ ......................... 26 Figure 3.14 UE Series Connection ................................ ................................ ......................... 27 Figure 3.15 TN Series Connection ................................ ................................ ......................... 28 Figure 3.16 TN Series Connection ................................ ................................ ......................... 29 Figure 3.17 Graph of CUREE protocol, displacement vs. time. ................................ ............. 31 Figure 3.18 Test jig for concentrically loaded specimens. ................................ ..................... 32 Figure 3.19 Photograph of a concentrically loaded sample in the MTS. ............................... 33 Figure 3.20 Test jig for eccentrically loaded specimens. ................................ ........................ 34 Figure 3.21 Photograph of an eccentrically loaded sample. ................................ ................... 35 Figure 4.1 Typical graphs of displacement and force vs time. ................................ ............... 37 Figure 4.2 Typical Load vs. displacement (hysteresis) graph. ................................ ............... 38 Figure 4.3 Change in dimension between walls of HSS during tension and compression cycles. ................................ ................................ ................................ ................................ ...... 39 Figure 4.4 Backbone curve overlaid on a hysteresis graph. ................................ ................... 40

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xi Figure 4.5 Example of local buckling of the unreinforced stud flanges, bending of top bushing, and failure of the weld between the gusset and the edge of the yielding plate. ....... 41 the photograph occurred in the tension cycle. ................................ ................................ ........ 42 Figure 4.7 Example of horizontal shift in data to gaps between mounting pin and yoke without the use of wedges. ................................ ................................ ................................ ...... 43 Figure 4.8 Wedges used to remove mechanical slack in top and bottom mounting yokes. ... 43 Figure 4.9 Wedges installed in lower mounting assembly. ................................ .................... 44 Figure 4.10 Us e of wedges eliminated horizontal shift in the graph. Compare to graph shown in figure 4.7. ................................ ................................ ................................ ............................ 45 Figure 4.11 T series back bone cur ................................ ................................ .................... 48 Figure 4.12T series back bone ................................ ................................ .................... 49 Figure 4.13 T series back thick HSS. ................................ ................................ ................................ ............................... 50 Figure 4.14T thick HSS. ................................ ................................ ................................ ............................... 51 Figure 4.15T thick HSS. ................................ ................................ ................................ ............................... 52 Figure 4.16 E shings. ................................ ................................ .................... 54

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xii Figure 4.17 E ................................ ................................ ................................ ........ 55 Figure 4.18 E ................................ ................................ .................... 56 Figure 4.19 E ................................ ................................ ................................ ............... 57 Figure 4.20 E ................................ ................................ ................................ ..................... 58 Figure 4.21 UC ................................ ................................ .................... 61 Figure 4.22 UC ................................ ................................ .................... 62 Figure 4.23 UC ................................ ................................ .................... 63 Figure 4.24 UC ................................ ................................ ................................ .. 64 Figure 4.25 UC ................................ ................................ ................................ ......... 65 Figure 4.26 UE ................................ ................................ .................... 67 Figure 4.27 UE ................................ ................................ ................................ ........ 68

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xiii Figure 4.28 UE ................................ ................................ ................................ ....... 69 Figure 4.29 UE thick yielding plates. ................................ ................................ ................................ ............... 70 Figure 4.30 TN ................................ ................................ .................... 72 Figure 4.31 Illustration of plastic hinges forming in a yield plate around a bushing. Large displacements lead to ................................ ................................ ................................ .. 74 Figure 4.32 Tested yield stress of 50 ksi nominal, steel plate. ................................ ............... 77 Figure 4.33 Stress strain curve for 50ksi nominal steel. ................................ ......................... 78 Figure 4.34 Yield plate in large c ompression displacement. ................................ .................. 80 Figure A1. Sample A1 before testing. ................................ ................................ ................... 86 Figure A2. Sample A1 after testing. ................................ ................................ ...................... 86 Figure A3. Sample A2 before testing. ................................ ................................ ................... 87 Figure A4. Sample A2 after testing. ................................ ................................ ...................... 87 Figure A5. Sample A3 before testing. ................................ ................................ .................... 88 Figure A6. Sample A3 after testing. ................................ ................................ ...................... 88 Figu re A7. Sample A4 before testing. ................................ ................................ ................... 89 Figure A8. Sample A4 after testing. ................................ ................................ ...................... 89 Figure A9. Sample A5 before testing. ................................ ................................ ................... 90 Figure A10. Sample A5 after testing. ................................ ................................ .................... 90 Figure A11. Sample A6 before testing. ................................ ................................ ................. 91 Figure A12. Sample A6 after testing. ................................ ................................ .................... 91

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xiv Figure A13. Sample A7 before testing. ................................ ................................ ................. 92 Figure A14. Sample A7 after testing. ................................ ................................ .................... 92 Figure A15. Sample A8 before testing. ................................ ................................ ................. 93 Figure A16. Sample A8 after testing. ................................ ................................ .................... 93 Figure A17. Sample A9 before testing ................................ ................................ .................. 94 Figure A18. Sample A9 after testing ................................ ................................ ..................... 94 Figure A19. Sample A10 before testing. ................................ ................................ ............... 95 Figure A20. Sample A10 after testing. ................................ ................................ .................. 95 Figure A21. Sample A11 before testing. ................................ ................................ ............... 96 Figure A22. Sample all after testing. ................................ ................................ ..................... 96 Figure A23. Sample A12 before testing ................................ ................................ ................ 97 Figure A24. Sample A12 after testing ................................ ................................ ................... 97 Figure A25. Sample A13 before testing. ................................ ................................ ............... 98 Figure A26. Sample A13 after testing. ................................ ................................ .................. 98 Figure A27. Sample A14 before testing. ................................ ................................ ............... 9 9 Figure A28. Sample A14 after testing. ................................ ................................ .................. 99 Figure A29. Sample A15 before testing. ................................ ................................ ............. 100 Figure A30. Sample A15 after testing. ................................ ................................ ................ 100 Figure A31. Sample A16 before testing. ................................ ................................ ............. 101 Figure A32. Sample A16 after testing. ................................ ................................ ................ 101 Figure A33. Sample A17 before testing. ................................ ................................ ............. 102 Figure A34. Sample A17 after testing. ................................ ................................ ................ 102 Figure A35. Sample A18 before testing. ................................ ................................ ............. 103

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xv Figure A36. Sample A18 after testing. ................................ ................................ ................ 103 Figure A37. Sample T1 before test. ................................ ................................ ..................... 104 Figure A38. Sample T1 after test. ................................ ................................ ........................ 104 Figure A39. Sample T2 before test. ................................ ................................ ..................... 105 Figure A40. Sample T2 after test. ................................ ................................ ........................ 105 Figure A41. Sample T3 before test. ................................ ................................ ..................... 106 Figure A42. Sample T3 after test. ................................ ................................ ........................ 106 Figure A43. Sample T4 before test. ................................ ................................ ...................... 107 Figure A44. Sample T4 after test. ................................ ................................ ......................... 107 Figure A45. Sample T5 before test. ................................ ................................ ..................... 108 Figure A46. Sample T5 after test. ................................ ................................ ........................ 108 Figure A47. Sample T6 before test. ................................ ................................ ..................... 109 Figure A48. Sample T6 after test. ................................ ................................ ........................ 109 Figure A49. Sample T7 before test. ................................ ................................ ..................... 110 Figure A50. Sample T7 after test. ................................ ................................ ........................ 110 Figure A51. Sample T8 before test. ................................ ................................ ..................... 111 Figure A52. Sample T8 after test. ................................ ................................ ........................ 111 Figure A53. Sample T9 before test. ................................ ................................ ..................... 112 Figure A54. Sample T9 after test. ................................ ................................ ........................ 112 Figure A55. Sample E1 before test. ................................ ................................ ..................... 113 Figure A56. Sample E1 after test. ................................ ................................ ........................ 113 Figure A57. Sample E2 before test. ................................ ................................ ..................... 114 Figure A58. Sample E2 after test. ................................ ................................ ........................ 114

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xvi Figure A59. Sample E3 before test. ................................ ................................ ..................... 115 Figure A60. Sample E3 after test. ................................ ................................ ........................ 115 Figure A61. Sample E4 before test. ................................ ................................ ..................... 116 Figure A62. Sample E4 after test. ................................ ................................ ........................ 116 Figure A63. Sample E5 before test. ................................ ................................ ..................... 117 Figure A64. Sample E5 after test. ................................ ................................ ........................ 117 Figure A65. Sample E6 before test. ................................ ................................ ..................... 118 Figure A66. Sample E6 after test. ................................ ................................ ........................ 118 Figure A67 Sample E7 before test. ................................ ................................ ....................... 119 Figure A68. Sample E7 after test. ................................ ................................ ........................ 119 Figure A69. Sample E8 before test. ................................ ................................ ..................... 120 Figure A70. Sample E8 after test. ................................ ................................ ........................ 120 Figure A71. Sample E9 before test. ................................ ................................ ..................... 121 Figure A72. Sample E9 after test. ................................ ................................ ........................ 121 Figure A73. Sample E10 before test. ................................ ................................ ................... 122 Figure A74. Sample E10 after test. ................................ ................................ ...................... 122 Figure A75. Sample E11 before test. ................................ ................................ ................... 123 Figure A76. Sample E11 after test. ................................ ................................ ...................... 123 Figure A77. Sample E12 before test. ................................ ................................ ................... 124 Figure A78. Sample E12 after test. ................................ ................................ ...................... 124 Figure A79. Sample UC1 before test. ................................ ................................ .................. 125 Figure A80. Sample UC1 after test. ................................ ................................ ..................... 125 Figure A81. Sample UC2 before test. ................................ ................................ .................. 126

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xvii Figure A82. Sample UC2 after test. ................................ ................................ ..................... 126 Figure A83. Sample UC3 before test. ................................ ................................ .................. 127 Figure A84. Sample UC3 after test. ................................ ................................ ..................... 127 Figure A85. Sample UC4 before test. ................................ ................................ .................. 128 Figure A86. Sample UC4 after test. ................................ ................................ ..................... 128 Figure A87. Sample UC5 before test. ................................ ................................ .................. 129 Figure A88. Sample UC5 after test. ................................ ................................ ..................... 129 Figure A89. Sample UC6 before test. ................................ ................................ .................. 130 Figure A90. Sample UC6 after test. ................................ ................................ ..................... 130 Figure A91. Sample UE1 before test. ................................ ................................ .................. 131 Figure A92. Sample UE1 after test. ................................ ................................ ..................... 131 Figure A93. Sample UE2 before test. ................................ ................................ .................. 132 Figure A94. Sample UE2 after test. ................................ ................................ ..................... 132 Figure A95. Sample UE3 before test. ................................ ................................ .................. 133 Figure A96. Sample UE3 after test. ................................ ................................ ..................... 133 Figure A97. Sample UE4 before test. ................................ ................................ .................. 134 Figure A98. Sample UE4 after test. ................................ ................................ ..................... 134 Figure A99. Sample PUC1 before test. ................................ ................................ ................ 135 Figure A100 Sample PUC1 after test. ................................ ................................ ................... 135 Figure A101. Sample PUC2 before test. ................................ ................................ .............. 136 Figure A102. Sample PUC2 after test. ................................ ................................ ................. 136 Figure A103. Sample PUC3 before test. ................................ ................................ .............. 137 Figure A104. Sample PUC3 after test. ................................ ................................ ................. 137

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xviii Figure A105. Sample PE1 before test. ................................ ................................ ................. 138 Figure A106 Sample PE1 after test. ................................ ................................ ...................... 138 Figure A107. Sample PE2 before test. ................................ ................................ ................. 139 Figure A108. Sample PE2 after test. ................................ ................................ .................... 139 Figure A109. Sample PE3 before test. ................................ ................................ ................. 140 Figure A110. Sample PE3 after test. ................................ ................................ .................... 140 Figure A111. Sample TN1 before test. ................................ ................................ ................ 141 Figure A112. Sample TN1 after test. ................................ ................................ ................... 141 Figure A113. Sample TN2 before test. ................................ ................................ ................ 1 42 Figure A114. Sample TN2 after test. ................................ ................................ ................... 142 Figure A115. Sample TN3 before test. ................................ ................................ ................ 143 Figure A116. Sample TN3 after test. ................................ ................................ ................... 143 Figure A117. Sample TN4 before test. ................................ ................................ ................ 144 Figure A118. Sample TN4 after test. ................................ ................................ ................... 144 Figure A119. Sample TN5 before test. ................................ ................................ ................ 145 Figure A120. Sample TN5 after test. ................................ ................................ ................... 145 Figure A121. Sample TN6 before test. ................................ ................................ ................ 146 Figure A122. Sample TN6 after test. ................................ ................................ ................... 146 Figure B1. Sample A1, force vs displacement. ................................ ................................ .... 148 Figure B2. Sample A1, displacement vs time. ................................ ................................ ..... 149 Figure B3. Sample A1, load vs time. ................................ ................................ ................... 149 Figure B4. Sample A3, force vs displacement. ................................ ................................ .... 150 Figure B5. Sample A3, displacement vs t ime. ................................ ................................ ..... 151

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xix Figure B6. Sample A3, force vs time. ................................ ................................ .................. 151 Figure B7. Sample A4, force vs displacement. ................................ ................................ .... 152 Figure B8. Sample A4, displacement vs time. ................................ ................................ ..... 153 Figure B9. Sample A4, force vs time. ................................ ................................ .................. 153 Figure B10. Sample A5, force vs displacement. ................................ ................................ .. 154 Figure B11. Sample A5, displacement vs time. ................................ ................................ ... 155 Figure B12. Sample A5, force vs time. ................................ ................................ ................ 155 Figure B13. Sample A6, force vs displacement. ................................ ................................ .. 156 Figure B14. Sample A6, displacement vs time. ................................ ................................ ... 157 Figure B15. Sample A6, force vs time. ................................ ................................ ................ 157 Figure B16. Sample A7, force vs displacement. ................................ ................................ .. 158 Figure B17. Sample A7, displacement vs time. ................................ ................................ ... 159 Figure B18. Sample A7, force vs time. ................................ ................................ ................ 159 Figure B19. Sample A8, force vs displacement. ................................ ................................ .. 160 Figure B20. Sample A8, displacement vs time. ................................ ................................ ... 161 Figure B21. Sample A8, force vs time. ................................ ................................ ................ 161 Figure B22. Sample A9, force vs displacement. ................................ ................................ .. 162 Figure B23. Sample A9, displacement vs time. ................................ ................................ ... 163 Figure B24. Sample A9, force vs time. ................................ ................................ ................ 163 Figure B25. Sample A10, force vs displacement. ................................ ................................ 164 Figure B26. Sample A10, displacement vs time. ................................ ................................ 165 Figure B27. Sample A10, force vs time. ................................ ................................ .............. 165 Figure B28. Sample A11, force vs displacement. ................................ ................................ 166

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xx Figure B29. Sample A11, displacement vs time. ................................ ................................ 167 Figure B30. Sample A11, force v s time. ................................ ................................ .............. 167 Figure B31. Sample A12, force vs displacement. ................................ ................................ 168 Figure B32. Sample A12, displacement vs time. ................................ ................................ 169 Figure B33. Sample A12, force vs time. ................................ ................................ .............. 169 Figure B34. Sample A13, force vs displacement. ................................ ................................ 170 Figure B35. Sample A13, displacement vs time. ................................ ................................ 171 Figure B36. Sample A13, force vs time. ................................ ................................ .............. 171 Figure B37. Sample A14, force vs displacement. ................................ ................................ 172 Figure B38. Sample A14, displacement vs time. ................................ ................................ 173 Figure B39. Sample A14, force vs time. ................................ ................................ .............. 173 Figure B40. Sample 15, force vs displ acement. ................................ ................................ ... 174 Figure B41. Sample A15, displacement vs time. ................................ ................................ 175 Figure B42. Sample A15, force vs time. ................................ ................................ .............. 175 Figure B43. Sample A16, force vs displacement. ................................ ................................ 176 Figure B44. Sample A8, displacement vs time. ................................ ................................ ... 177 Figure B45. Sample A16, force vs time. ................................ ................................ .............. 177 Figure B46. Sample A17, force vs displacement. ................................ ................................ 178 Figure B47. Sample A17, displacement vs time. ................................ ................................ 179 Figure B48. Sample A17, force vs time. ................................ ................................ .............. 179 Figure B49. Sample A18, force vs displacement. ................................ ................................ 180 Figure B50. Sample A18, displacement vs time. ................................ ................................ 181 Figure B51. Sample A18, force vs time. ................................ ................................ .............. 181

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xxi Figure B52. Sample T1, force vs displacement. ................................ ................................ .. 182 Figure B53. Sample T1, displacement vs time. ................................ ................................ ... 183 Figure B54. Sample T1, force vs time. ................................ ................................ ................ 183 Figure B55. Sample T2, force vs displac ement. ................................ ................................ .. 184 Figure B56. Sample T2, displacement vs time. ................................ ................................ ... 185 Figure B57. Sample T2, force vs time. ................................ ................................ ................ 185 Figure B58. Sample T3, force vs displacement. ................................ ................................ .. 186 Figure B59. Sample T3, displacement vs time. ................................ ................................ ... 187 Figure B60. Sample T3, force vs time. ................................ ................................ ................ 187 Figure B61. Sample T4, force vs displacement. ................................ ................................ .. 188 Figure B62. Sample T4, displacement vs time. ................................ ................................ ... 189 Figure B63. Sample T4, force vs time. ................................ ................................ ................ 189 Figure B64. Sample T5, force vs displacement. ................................ ................................ .. 190 Figure B65. Sample T5, displacement vs time. ................................ ................................ ... 191 Figure B66. Sample T5, force vs time. ................................ ................................ ................ 191 Figure B67. Sample T6, force vs displacement. ................................ ................................ .. 192 Figure B68. Sample T6, displacement vs time. ................................ ................................ ... 193 Figure B69. Sample T6, force vs time. ................................ ................................ ................ 193 Figure B70. Sample T7, force vs displacement. ................................ ................................ .. 194 Figure B71. Sample T7, displacement vs time. ................................ ................................ ... 195 Figure B72. Sample T7, force vs time. ................................ ................................ ................ 195 Figure B73. Sample T8, force vs displacement. ................................ ................................ .. 196 Figure B74. Sample T8, displacement vs time. ................................ ................................ ... 197

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xxii Figure B75. Sample T8, forc e vs time. ................................ ................................ ................ 197 Figure B76. Sample T9, force vs displacement. ................................ ................................ .. 19 8 Figure B77. Sample T9, displacement vs time. ................................ ................................ ... 199 Figure B78. Sample T9, force vs time. ................................ ................................ ................ 199 Figure B79. Sample E1, force vs displacement. ................................ ................................ .. 200 Figure B80. Sample E1, displacement vs time. ................................ ................................ ... 201 Figure B81. Sample E1, force vs time. ................................ ................................ ................ 201 Figure B82. Sample E2, force vs displacement. ................................ ................................ .. 202 Figure B83. Sample E2, displacement vs time. ................................ ................................ ... 203 Figure B84. Sample E2, force vs time. ................................ ................................ ................ 203 Figure B85. Sample E3, force vs displacemen t. ................................ ................................ .. 204 Figure B86. Sample E3, displacement vs time. ................................ ................................ ... 205 Figure B87. Sample E3, force vs time. ................................ ................................ ................ 205 Figure B88. Sample E4, force vs displacement. ................................ ................................ .. 206 Figure B89. Sample E4, displacement vs time. ................................ ................................ ... 207 Figure B90. Sample E4, force vs time. ................................ ................................ ................ 207 Figure B91. Sample E5, force vs displacement. ................................ ................................ .. 208 Figure B92. Sample E5, displacement vs time. ................................ ................................ ... 209 Figure B93. Sample E5, force vs time. ................................ ................................ ................ 209 Figure B94. Sample E6, force vs displacement. ................................ ................................ .. 210 Figure B95. Sample E6, displacement vs time. ................................ ................................ ... 211 Figure B96. Sample E6, force vs time. ................................ ................................ ................ 211 Figure B97. Sample E7, force vs displacement. ................................ ................................ .. 212

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xxiii Figure B98. Sample E7, displacement vs time. ................................ ................................ ... 213 Figure B99. Sample E7, force vs time. ................................ ................................ ................ 213 Figure B100. Sample E8, force vs displacement. ................................ ................................ 214 Figure B101. Sample E8, displacement vs time. ................................ ................................ 215 Figure B102. Sample E8, force vs time. ................................ ................................ .............. 215 Figure B103. Sample E9, force vs displacement. ................................ ................................ 216 Figure B104. Sample E9, displacement vs time. ................................ ................................ 217 Figure B105. Sample E9, force v s time. ................................ ................................ .............. 217 Figure B106. Sample E10, force vs displacement. ................................ .............................. 218 Figure B107. Sample E10, displacement vs time. ................................ ............................... 219 Figure B108. Sample E10, force vs time. ................................ ................................ ............ 219 Figure B109. Sample E11, force vs displacement. ................................ .............................. 220 Figure B110. Sample E11, displacement vs time. ................................ ............................... 221 Figure B111. Sample E11, force vs time. ................................ ................................ ............ 221 Figure B112. Sample E12, force vs displacement. ................................ .............................. 222 Figure B113. Sample E12, displacement vs time. ................................ ............................... 223 Figure B114. Sample E12, force vs time. ................................ ................................ ............ 223 Figure B115. Sample PE1, force vs displacement. ................................ .............................. 224 Figure B116. Sample PE1, displacement vs time. ................................ ............................... 225 Figure B117. Sample PE1, force vs time. ................................ ................................ ............ 225 Figure B118. Sample PE2, force vs displacement. ................................ .............................. 226 Figure B119. Sample PE2, displacement vs time. ................................ ............................... 227 Figure B120. Sample PE2, force vs time. ................................ ................................ ............ 227

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xxiv Figure B121. Sample PE3, force vs displacement. ................................ .............................. 228 Figure B122. Sample PE3, displacement vs ti me. ................................ ............................... 229 Figure B123. Sample PE3, force vs time. ................................ ................................ ............ 229 Figure B124. Sample UC1, force vs displacement. ................................ ............................. 230 Figure B125. Sample UC1, displacement vs time. ................................ .............................. 231 Figure B126. Sample UC1, force vs time. ................................ ................................ ........... 231 Figure B127. Sample UC2, force vs displacement. ................................ ............................. 232 Figure B128. Sample UC2, displacement vs time. ................................ .............................. 233 Figure B129. Sample UC2, force vs time. ................................ ................................ ........... 233 Figure B130. Sample UC3, force vs displacement. ................................ ............................. 234 Figure B131. Sample UC3, displacement vs time. ................................ .............................. 235 Figure B132. Sample UC3, force vs time. ................................ ................................ ........... 235 Figure B133. Sample UC4, force vs displacement. ................................ ............................. 236 Figure B134. Sample UC4, displacement vs time. ................................ .............................. 237 Figure B135. Sample UC4, force vs time. ................................ ................................ ........... 237 Figure B136. Sample UC5, force vs displacement. ................................ ............................. 238 Figure B137. Sample UC5, displacement vs ti me. ................................ .............................. 239 Figure B138. Sample UC5, force vs time. ................................ ................................ ........... 239 Figure B139. Sample UC6, force vs displacement. ................................ ............................. 240 Figure B140. Sample UC6, displacement vs time. ................................ .............................. 241 Figure B141. Sample UC6, force vs time. ................................ ................................ ........... 241 Figure B142. Sample PUC1, force vs displacement. ................................ ........................... 242 Figure B143. Sample PUC1, displacement vs time. ................................ ............................ 243

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xxv Figure B144. Sample PUC1, force vs time. ................................ ................................ ......... 243 Figure B145. Sample PUC2, force vs displacement. ................................ ........................... 244 Figure B146. Sample PUC2, displacement vs time. ................................ ............................ 245 Figure B147. Sample PUC2, force vs time. ................................ ................................ ......... 245 Figure B148. Sample PUC3, force vs displacement. ................................ ........................... 246 Figure B149. Sample PUC3, displacement vs time. ................................ ............................ 247 Figure B150. Sample PUC3, force vs time. ................................ ................................ ......... 247 Figure B151. Sample UE1, force vs displacement. ................................ ............................. 248 Figure B152. Sample UE1, displacement vs time. ................................ .............................. 249 Figure B153. Sample UE1, force vs time. ................................ ................................ ........... 249 Figure B154. Sample UE2, force vs displacement. ................................ ............................. 250 Figure B155. Sample UE2 displacement vs time. ................................ .............................. 251 Figure B156. Sample UE2, force vs time. ................................ ................................ ........... 251 Figure B157. Sample UE3, force vs displacement. ................................ ............................. 252 Figure B158. Sample UE3, displacement vs time. ................................ .............................. 253 Figure B159. Sample UE3, force vs time. ................................ ................................ ........... 253 Figure B160. Sample UE4, force vs displacement. ................................ ............................. 254 Figure B161. Sample UE4, displacement vs time. ................................ .............................. 255 Figure B162. Sample UE4, force vs time. ................................ ................................ ........... 255 Figure B163. Sample TN1, force vs displacement. ................................ ............................. 256 Figure B164. Sample TN1, displacement vs time. ................................ .............................. 257 Figure B165. Sample TN1, force vs time. ................................ ................................ ........... 257 Figure B166. Sample TN2, force vs displacement. ................................ ............................. 258

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xxvi Figure B167. Sample TN2, displacement vs ti me. ................................ .............................. 259 Figure B168. Sample TN2, force vs time. ................................ ................................ ........... 259 Figure B169. Sample TN3, force vs displacement. ................................ ............................. 260 Figure B170. Sample TN3, displacement vs time. ................................ .............................. 261 Figure B171. Sample TN3, force vs time. ................................ ................................ ........... 261 Figure B172. Sample TN4, force vs displacement. ................................ ............................. 262 Figure B173. Sample TN4, displacement vs time. ................................ .............................. 263 Figure B174. Sample TN4, force vs time. ................................ ................................ ........... 263 Figure B175. Sample TN5, force vs displacement. ................................ ............................. 264 Figure B176. Sample TN5, displacement vs time. ................................ .............................. 265 Figure B177. Sample TN5, force vs time. ................................ ................................ ........... 265 Figure B178. Sample TN6, force vs displacement. ................................ ............................. 266 Figure B179. Sample TN6, displacement vs time. ................................ .............................. 267 Figure B180. Sample TN6, force vs time. ................................ ................................ ........... 267

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xxvii LIST OF TABLES TABLE 4.1. A 4.2 T Series summary of tension, displacement, and failure modes 4.3. E Series summary of tension, displacement, and 4.4. UC 4.5. UE 4.6. TN 4.7 Comparison of Theoretical to Actual Forces in connections for various plate 79

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1 CHAPTER I INTRODUCTION 1.1 B ackground Adding ductility to a cold formed steel frame so that it may resist the high lateral demands induced by seismic events, is challenging due to the nature of the material. While the cold formed steel (CFS) in many cases has a better ductility than many hot rolled steels used in construction, the small cross sectional areas of various members do not allow for significant energy dissipation in the event of an earthquake. These members also tend to be weak in transverse loading conditions, perpendicular to their cross sections, compared to their capaciti es when loaded in an the longitudinal direction. Because of this, the standard methods of resisting lateral loads due to an earthquake are difficult to apply. A study by Lee and Foutch (2010) evaluating CFS braced frame structures finds that they do no t reach designed seismic resistance using current design code and using conservative R factors did not necessarily increase performance. A revolutionary construction method of using predesigned/prefabricated CFS structural panels connected to hollow stru ctural section ( HSS ) columns has been developed that increases the efficiency of construction in CFS Factory manufactured assemblies are shipped to a job site where they are connected together, forming the structural system of a building Figure 1.1 sho ws a typical 8 foot long panel connected to a HSS column.

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2 Figure 1. 1 Example of typical panel and column in construction. This method of constructi on greatly reduces engineering and construction cost and time. These economic factors have resulted in an increase in demand for such structures. While the current design meets all load and serviceability requirements for resisting lateral loads in low seismic regions improved story stiffness and ductility for co nstruction in a seismically active area is needed A n extensive research and development program to add lateral strength and ductility to this building system is underway. T raditional steel structures absorb seismic energy through the ductility of membe rs, this system absorbs energy in the connections. A study by Uang et al. (2010) determined that ropriate for a CFS moment frame ( Dao & Van De Lindt 2013) Due to the limita tions of the cold formed steel, a unique approach was taken to add ductility to the system by installing yield plate s in the connection between CFS panels and HSS columns. M etal bushing s are used on either side of a yield ing plate so that the plate can plastically deform around the

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3 bushings during displacement Figure 1.2 shows the general arrangement of the connections for the panel to posts. Figure 1. 2 Location of Connections on a typical CFS Panel

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4 Figure 1. 3 Concept of y ield ing plate connection to HSS column. Showing compression and tension cycle. The purpose of the yield ing plate s is to dissipate the energy imparted to the building system during an earthquake. They al so add ductility to the system to make use of the strength of the steel as it deforms plastically The challenge is finding a combination of material and connection geometry that will provide an elastic response sufficient to resist wind loads, and a plastic res ponse to absorb earthquake energy a ll while maintain ing positive connection between panel and column. If the system is too stiff other later al force resisting members may be damaged before significant energy has been dissipated. If the system is not sti ff enough it may be unable to resist non seismic lateral loads elastically This approach to adding ductility to a system by utilizing a yielding connection is a departure from current practice where connections are designed with an overs strength facto r to ensure elastic behavior. Structural members other than the connection are designed to yield and provide the ductility for the system. Four of the most common methods of adding ductility to a structure made from structural steel will be discussed in chapter 2 of this work.

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5 1.2 Scope of Investigation In the scope of this thesis, six types of connections were tested using a cyclic loading profile of increasing displacements in a Material Testing S ystem (MTS) testing machine to evaluate the performance of each specimen. The connection designs evolved throughout the investigation while considering tested performance and manufacturing efficiencies The purpose of the research in this work is to develop a design for a connection between a cold formed steel structural panel to a HSS column for commercial production in seismic ally active regions Due to the difficulty in comp uter modeling this component, an experimental analysis of the samples is used to evaluate their p erformance in bo th failure mode and their response to displacement s Connections need to be able to resist multiple cycles of loading while providing consistent and predictable force resisting performance. Based on estimated building demands, an acceptable connection w ill be able to resist a 16 kip load, or more, and a displacement of greater than 1 inch. As the tested connections are to be incorporated into a new building system to resist uantify its anticipated performance. FEMA document P695, Quantification of Building Seismic Performance Factors outlines a method for doing this (FEMA 2009) The results from this work will be used in the generation of a link to be used in a future com puter model This model will be used for the development of a building arche type for this method of construction and also as a component in the generation of a Response Modification coefficient ( or R value ) for the building system.

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6 CHAP TER II BACKGROUND 2.1 Why seismic loads are considered in design Seismic loads must be considered in design for the simple reason of it being a code requirement. ASCE 7 10 Minimum Design Load for Buildings and Other Structures states designed and constructed to resist the effects of ASCE 7 10 dedicates 15 chapters of its 31 chapters to seismic design. In addition to ASCE 7, which is the minimum standard to design to, there are numerous other seismic requirements required at every level of building jurisdiction from local up through federal government. for seismic events neglects the fact, development of codes and regulations arose from lessons learned from catastrophic seismic events that have caused large scale loss of life, damage to property and infrastructure. According to former FEMA Director Jam The hazards associated with earthquakes in the U.S. has remained relatively constant over time, but the risk associated with them has increased, as population centers have grown in seismically active areas (Arguero n.d.) Over 70 notable e arthquakes have struck the U S In 1906 a 7.9 magnitude earth quake struck San Francisco, CA Figure 2.1 shows the city afterwards. There were an estimated 3000 deaths. It is estimated that this event w ould cause an economic loss of $120 billion if it were to occur today (London 2006). This event began serious research and discussion on earthquake engineering in the U.S. but did not produce any definitive seismic code (Berg 1983).

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7 Figure 2. 1 Aftermath of San Francisco, CA earthquake, 1906 In 1933 a 6.4 magnitude earthquake occurred near Long Beach, CA causing 120 deaths and damaging many structures including schools. This event spurred the California legislature to develop regulations for schools, ma sonry buildings, and set standards for of some seismic design requirements (Berg 1983). Damage to Venice high school is shown in figure 2.2. Figure 2. 2 Damage to Venice high school 1933.

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8 More recently the 1989 6.9 magnitud e earthquake in Loma Prieta, CA caused 63 deaths, injured over 3700 people, and caused over $6 billion in damage at the time. Figure 2. 3 Destroyed building after earthquake in Loma Prieta, CA 1989. (Nikitin 1989) The 6.7 magnitude earthquake that struck Northridge, CA, in 1994 killed 57 people and did over $44 billion in dam ages. Lessons are still being learned from these events and have had significant effect on the development of current design code and constru ction methods. Figure 2.4 Illustrates an example of the damage caused to structures from the earthquake.

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9 Figure 2. 4 Damaged parking structure after the Northridge earthquake 1994. (Celebi n.d.) 2.2 Systems in steel co nstruction to resist lateral forces The study and codification of seismic design requirements has led to not only development of regulations and code requirement s but also lead to the generation of design manuals for various materials and construction me thods. The American Institute of Steel Construction (AISC) publishes the Seismic Design Manual which covers the specific details of designing in structural steel for seismic loads. Four of the most common methods for resisting lateral loads in steel desi gn are discussed below. A common feature of all the methods, is the connections between horizontal and vertical load bearing members are designed so that the ductile yielding is developed within the members themselves and not the connection Specific members or portions of a member are designed to yield plastically or by buckling thus dissipating some of the seismic energy imparted to the structure.

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10 (2010 develop es on to state that the other frame elements must be stronger than the fuses, especially the connections. 2.2.1 Concentrically Braced Frames Concentrically braced frames are one of the most common construction methods using steel to resist lateral loads due to their material, (AISC 2012). They operate similar to a truss except they are designed for resisting lateral versus vertical loads. The diagonal cross bracing members are designed to work axially in tension and compression in opposing pairs. The center lines of connect ing members, columns, beams, and diagonal braces all intersect at a point to reduce rotation and moment at a connection. Figure 2.5 illustrates two of the various types of concentrically braced frames. Figu re 2.6 shows a connection in a concentrically br aced frame. Figure 2. 5 Examples of concentrically braced frames.

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11 Figure 2. 6 A connection in a concentrically braced frame. These systems are relatively stiff, not allowing for as much story dri ft as other systems. The get their ductility from the buckling of a diagonal member in compression. The members generally buckle out plane when the y do so. The cross bracing can be limiting in locating doors, windows and corridors due to the obstruction they cause. 2.2.2 Moment Resisting Frames Moment resis ting frames use a concept described as strong column/weak beam. The beams have section of reduced area, generally where a section of the flange is removed, that is designed to yield plastically whe n the frame is exposed a seismic load. This reduced area section of the beam is designed to yield before other members in the structural frame do. The strength of the connection must be such that it is capable of developing the plastic hinge in the beam section. Figure 2.7 illustrates the general frame layout of a typical moment fram e

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12 Figure 2. 7 Layout of a moment frame. Figure 2.8 shows the connection in a moment frame and the protected zone of the reduced section. The damage or attachments that might affect the designed performance or initiate a failure originating from cracks or penetrations. Figure 2. 8 Typic al moment frame connection showing the reduced beam section. The moment frame generally has more ductility but less stiffness than the concentrically braced frame and often uses less economical steel shapes. The beams and columns must be larger than a comparable braced frame for resisting vertical loads. This is

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13 so that the connections may be designed such that the structure can resist the lateral loads applied to the structure. 2.2.3 Eccentrically Braced Frames An eccentrically braced frame combines aspects from the concentrically braced frame and moment frame concept to get the best performance characteristics of each. The eccentrically braced frame uses diagonal braces to provide lateral support like the concentrically braced frame does. The difference is i n their orientation, the center lines of connecting members no longer connect at a common work point to eliminate applied designed to act much like t he reduced section of beam in a moment frame. It is designed to yield before any other member or connection in the frame. It is this link that provides the ductility for the system. Figure 2.9 illustrates two common ecc entric ally braced frame layouts, a nd F igure 2.10 is a photograph that has an example of each. Figure 2. 9 Example of eccentrically braced frame layouts.

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14 Figure 2. 10 Building with an eccentrically braced frame structural system. 2.2.4 Buckling Restrain Braced Frames Buckling restrained braced frames are a special sub class of the concentrically braced frame system. It uses opposing diagonal braces to resist lateral load just as the concentrically braced frame does. The difference is that the diagonal braces are a designed assembly versus a plain steel section. The brace assembly consists of a steel core that is treated with an unbonding material This core is inserted inside of a hollow steel shell which is then filled with a mortar mixture. The purpose of the unbonding material is to allow the steel core to deform axially in tension, independently from the mortar and steel shell. In compression the mortar and steel shell increase compression capacity of the steel cor e such that the capacity of the diagonal brace is very similar when loaded in tension and compression. Figure 2.11 illustrates the configuration of a buckling restrained brace.

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15 Figure 2. 11 Illustration of a buckling restraine d brace. Figure 2.12 shows a building the orientation of the buckling restrained braces It them in an identical configuration as a concentrically braced frame. Figure 2. 12 Buckling restrained braces installed in a buildi ng frame.

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16 CHAPTER III RESEARCH PROGRAM 3.1 Scope of testing Six types of connections were tested in a 220 k ip capacity MTS testing machine under displacement control and resulting forces versus time and displacements After each series of test s the failures of the samples were evaluated and a new design generated to overcome the deficiencies of its predecessor. The difference between each type of connection was primarily geometric or in the material used. For example some samp le types were loaded concentrically with the load path through the specimen in a straight line. In others there was a n eccentr icity in the load path Grade 50 steel plates were tested as were 46 ksi HSS tube sections loaded perpendicular to their wall. All yield plat the CFS studs used in the system In each type of connection there were two variables that w ere modified between test samples. One was t he thickness of the yielding plate s or HSS tube sections, varying between size and shape of bushing used to facilitate the formation of a plastic hinge in t he yield plate The bushing s used were either rectangular or circular in shape. Figure 3.1 shows an example of the different bushings used in testing. For the round bushing, 1 1/

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17 Figure 3. 1 Bushings used to generate plastic hinges in the yielding plate of the connection. A brief description of the six tested connections is provided below. 3.1.1 A Series Connection The first sample connection was given being the first one. It was a proof of concept model that utilized the standard fabrication methods of fabricating cold formed steel components and welding those pieces together using a flux cored welding proc ess The connection was made from a section of reinforced CFS stud, comprised of two studs nested together, simulating what would be a horizontal force collecting member in a panel It was attached to a non reinforced stud sec tion representing the edge s tud of a panel. The two studs were welded together with a gusset plate. The yield plate was attached at the bottom of the edge stud and welded to th e end gusset plate. Figures 3.2 and 3.3 show what a typical A Series connection looked like.

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18 Figure 3. 2 A Series C onnection. Figure 3. 3 A Series Connection Bushing Yielding Plate

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19 Figure 3.4 is the detail of the weld configuration between the side gusset plates and the yielding plate. The bottom fillet weld was on all samples, and one half of the samples had an additional fillet weld on the upper corner of the yield plate to the si de of the gusset Figure 3. 4 Detai l of welds between gusset plate and yielding plate. A notch was cut in the end of the reinforced stud to allow for access of a torque wrench to the bolt that would atta ch the connection to the column In this connection thick yield plates were used. Eighteen s Virtually a ll welds were made using a flux cored welding process. 3.1.2. T Serie s Connection The T Series connection utilizes 6x6 HSS tubes were used as the columns in this type of construction. Two versions were developed where the assembly between the stud and the HSS tube was slightly different. In the version 1 connection the flange of the CF S track was extended down along the side of the HSS tube. The stud bottom was welded to the fa ce of the HSS tube. Figures 3.5, and 3.6 illustrate a typical version 1 of a T series connection.

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20 Figure 3. 5 T Series Connection version 1 The bold lines indicate fillet weld locations. Figure 3. 6 T Series Connection version 1

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21 Version 2 of the T series connection eliminated the flange extension on the track. Both the stud and track terminated at the face of the HSS section. Gusset plates were used to connect the stud in track section to the HSS section Figures 3.7 and 3.8 show a typically T series, version 2 connection. Fig ure 3. 7 T Series Connection version 2

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22 Figure 3. 8 T Series Connection, version 2 3.1.3 E Series Connection The E Series Connection also utilizes a HSS tube section connected to a CFS member, co mprised of a stud in track It was determined that in some panel configurations a concentric loading path from the horizontal member through the attachment bolt to the column was not possible. This connection was d eveloped to test the effects an eccentricity would have on the assembly. The track section of CFS extends down an open end of the inner perimeter of the HHS to the track, along the outside of the track to the HSS on the sides, and across the top between the stud and tube. Figures 3.9 and 3.10 show a typical E series connection. There are 3 samples labeled with a PE designation. They are an E series design, but welded by metal inert gas (MIG) p rocess, to verify the performance against those made by a flux cored welding process

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23 Figure 3. 9 E Series C onnection Figure 3. 10 E Series C onnection

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24 3.1.4 UC Series Connection The UC series c onnection was developed to maximize the use of CSF and to eliminate shortcomings found during the testing of the A series which are discussed in chapter 4 of this work ped CFS gusset was used to secure the yield plate to the assembly. It wrapped around the yield plate and across the flanges of the edge stud and continued up along the reinforced stud. There is a single tack weld in the center of the yield plate to the edge stud to ke the load path is concentric. The reduced CFS section is extended into the unreinforced stud and welded to the flange to stiffen the assembly. A cut out in the reduced section of the re inforced stud was made to allow for access to the 3/4" inch bol t for installation. Figures 3.11 and 3.12 show a typical UC series connection. Figure 3. 11 UC Series Connection

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25 Figure 3. 12 UC Series Connection Extended reduced stud

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26 3.1.5. UE Series Connection The UE connection is identical in construction to the UC connection except that the reinforced stud is 1 results in an eccentricity identical to the E series connection. Figures 3.13 and 3.14 s how a typical UE connection. There are three samples labeled with a PUE designation. They are an UE series design, but welded using a MIG process to verify the per formance against those made by using the flux cored process. Figure 3. 13 UE Series Connection

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27 Figure 3. 14 UE Series Connectio n Extended reduced stud

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28 3.1.6. TN Series Connection The final connection tested was an adaptation of the T series. A notch was cut from the face and side walls of the HSS section to accept a reinforced stud inserted 3 inches into the HSS through the top face The stud was welded to the HSS section along the outside vertical edges of the stud. Figures 3.15 and 3.16 show a typical TN connection. Figure 3. 15 TN Series Connection

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29 Figure 3. 16 TN Series Connection 3.2 Testing proc edure All samples were tes ted in a 220 kip MTS testing machine at th e University of Colorado Denver (UCD) Structures Laboratory in Denver, CO and subjected to the same cyclic protocol of progressively increasing tension and compressi on cycles D isplacement was the controlling variable and the resisting force developed was recorded by the MTS data acquisition system. A modified Consortium of Universities for Research in Earthquake engineering ( CUREE ) loading p rotocol was used to simulate the accumulated damage to a component or structure exposed to a ground motion The CUREE protocol is based on a single large leading cycle followed by 2 to 6 smaller trailing cycles, u sually 75% of the leading cycle displacement. Th e next leading cycle is an increase over the last leading cycle. In this investigation 0.2 inches was used as the primary step increase, in leading cycle displacement. Table 3.1 and shows the valu es program med into the MTS and Figure 3.17 is a graph of d isplacement vs. time for this protocol.

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30 Table 3.1 Modified CUREE Protocol Step No. Cycles Displacement (inches) Frequency (Hz) 1 6 0.025 0.125 2 1 0.05 0.125 3 6 0.025 0.125 4 1 0.1 0.125 5 3 0.075 0.125 6 1 0.2 0.125 7 2 0.015 0.125 8 1 0.4 0.125 9 2 0.3 0.0625 10 1 0.6 0.0625 11 2 0.45 0.0625 12 1 0.8 0.0625 13 2 0.6 0.0625 14 1 1.0 0.0625 15 2 0.75 0.0625 16 1 1.2 0.0625 17 2 0.9 0.0625 18 1 1.4 0.0625 19 2 1.05 0.0625 20 1 1.6 0.0625 21 2 1.2 0.0625 22 1 1.8 0.04167 23 2 1.35 0.04167 24 1 2.0 0.04167

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31 Figure 3. 17 Graph of CUREE protocol, displacement vs. time. The frequency of each cycle was determined by the physical capabilities of the MTS. It is the maximum frequency that can be obtained by the MTS for a given displacement while providing maximum performance. Too fast and the MTS is unable to keep up and reach a specified displacement before reversing direction. To o slow and the test time increases and becomes inefficient. The purpose of using the CUREE protocol according to is to simulate the accumulated damage a component may e xperience in a seismic episo de (Krawinkler et al. 2001).

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32 Based on connection geometry there we re two different load paths through a sp ecimen based on its geometry The first was a xially concentric through the specimen so no moment w as introduced to the connection as shown in figure 3.18 and 3.19 The load path through the mounting bolt at the bottom of the sample is in line with the reinforced stud and continues up to the top mounting yoke of the MTS. Figure 3. 18 Test jig for concentrically loaded specimens.

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33 Figure 3. 19 Photograph of a concentrically loaded sample in the MTS. It was determined that in some circumstances a configuration of connection will be required where there would be a non concentric load path through it. The reason for this is to allow access for tools to tighten the bolts that will secure panels to column s It also allows for crossing bolts through a column for panels positioned perpendicular to each other at a column As a result the load path through the mounting bolt through the reinforced stud is

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34 Resulting in the second load path, a n eccentric one. Figure 3.20 and 3.21 show the geometry of this loading configuration. Figure 3. 20 Test jig for eccentrically loaded specimens.

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35 Figure 3. 21 Photograph of an eccentrically loaded sample. Bolts connecting the loading bar to the CFS reinforced stud on the top of the specimen were torqued to 350 ft lb to prevent slippage. Depending on the sample two or sample. A single d iameter A325 bolt torqued to 350 ft lb was used to connect the sample to the simulated HSS mounting block. A bushing was installed on each side of the yielding plate to facilitate the formation of a plastic hinge in the yielding p late. Eccentric load path

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36 CHAPTER IV RESULTS 4.1 Description of outputs T he MTS provided data on the displacement and applied force vs time for each sample. Using a custom program run in MATLAB the data was extracted and three graphs for each sample were generated: d isplacement versus time, force versus time, and a force versus displacement. The force versus displacement graph also know n as a hysteresis plot, provides the best visualization of raw data to evaluate our samples. It graphically demonstrates how much a particular sample could deflect before it fails as well has the forces achieved at d ifferent displacements. The area within the loops of the graph are equivalent to the energy diss ipated by the connection. Figure 4.1 shows typical graphs of displacement vs. time and force vs time respectively.

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37 Figure 4. 1 Typical graphs of displacement and force vs time. Figure 4.1 also shows how peak displacements correlate with peak forces. As the test progresses and displacements continue to increase, there is a noticeable reduction in applied force for the given displacements. This is an indication that a mechanism o f failure has begun in the connection. In this example two spikes can be seen in compression on the force graph. They correlate with the two largest compression displacements on the displacement graph. The test sample came in contact with the lower moun ting block at these displacements. This is analogous to a panel coming in contact with a column during a lateral movement during an earthquake

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38 Using the same data and MATLAB program a force versus displacement or hysteresis graph can be generated as we ll. Figure 4.2 s hows a representative hysteresis graph. Figure 4. 2 T ypical Load vs. displacement ( hysteresis ) graph. In this graph one can also see where the connection came into contact with the bottom mounting block in the larger compression cycles. Another trend of note that can be observed is a non symmetric behavior in the tension and compression cycles. Because these samples ar e being moved with relatively large displacements, significant lateral displacements in some members of the co nnection can also be observed. M oment arm length between the edge of the bushing and the edge of the yielding plate or HSS changes as the geometr y of the connecti on changes throughout a cycle. Figure 4.3 illustrates this change in geometry.

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39 Figure 4. 3 Change in dimension between walls of HSS during tension and compression cycles. shing the u ndeformed moment arm bushing In a large displacement the length of translates to a 25 % reduction in moment arm length. 4.2 Analysis of Connections Backbone curves were generated for the T, E, UC, UE, and TN families of connections. A backbone curve is an idealization of behavior of a connection based on the hysteresis graph. The backbone curve is made up of the linear elastic behavior of the

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40 connection in small displacements, the ultima te strength it obtains in during a displacement, and its residual capacity at the maximum displacement. Figure 4.4 shows an example of a typical backbone curve. Figure 4. 4 Backbone curve overlaid on a hysteresis graph. A ba ckbone curve is a useful tool in evaluating and comparing the performance of one connection to another. This section will provide various analysis of connections based on their backbone curves. 4.2 .1 A series. There was a discovery learning process on how to obtain the best possible data from our samples, during the testing of the A seri es of connections. The result was modifications to the physical set up of the test specimen in almost every test in this series. Local buckling in the unreinforced stu d combined with the lateral outward movement in the legs of the cut

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41 out of the reinforced stud section, resulted in premature failure of the connection before significant deformation of the yielding plate was achieved. This is demonstrated in Figure 4.5. In subsequent connection families using CFS and yielding plates, the vertical flanges of the unreinforced stud are reinforced to eliminate this issue. Figure 4. 5 Example of local buckling of the unreinforced stud flanges, ben ding of top bushing, and failure of the weld between the gusset and the edge of the yielding plate. also bend in the tension cycle along with the yielding plate. This res ults in only one yield line in the yielding plate located along the center line vs. the preferred result of two yield lines one on either side of the bushing Figure 4.6 illustrates the permanent deformation of the top bushing.

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42 Figure 4. 6 shown in the photograph occurred in the tension cycle. The lessons learned with this series were used to modify and improve future test specimens and als o resulted in modification of the test procedure to reduce experimental uncertainty in the data of following tests. The most significant improvement was the development of wedges to remove mechanical slack from the system b etween the 2 in ch diameter round pins, the mounting yokes and the simulated HSS column piece. Figure 4.7 illustrates the horizontal shift in the data on a hysteresis graph.

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43 Fig ure 4. 7 Example of horizontal shift in data to gap s between mounting pin and yo ke without the use of wedges. Figure 4.8 is a photograph of the wedges that were fabricated to remove mechanical It was cut diagonally through the thickness of the plate down its length. Figure 4. 8 Wedges used to remove mechanical slack in top and bottom mounting yokes. The wedges were used in the top and bottom mounting yokes. Figure 4.9 shows their location in the lower mounting assembly.

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44 Figure 4. 9 Wedges installed in lower mounting assembly. After the wedges were utilized the horizontal shift in data was eliminated. Figure 4.10 is a hysteresis plot of the fir st test run after wedges were installed. Note the lack of horizontal s hift compared to that shown in F igure 4.7 previously. The wedges also had a secondary benefit of eliminating rotation around the mounting pin in the yoke. This more closely simulated conditions a connection would be under in a CFS Panel.

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45 Figure 4. 10 Use of wedges eliminated horizontal shift in the graph. Compare to graph shown in figure 4.7. Due to the variability in test setup from one specimen to the next, and the poor performance of the connection without external stabilization back bone curves were not generated for this family of connections The lessons learned from this series were used to develop the UC and UE connections, as well as standar dize the testing procedure. Table 4.1 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the A series A summary of the primary failure modes is also included. Side gusset plate buckling was the primary failure mechanism for samples A1 to A11. Once the local buckling was controlled through the use

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46 of steel plates and clamps, failures in the yielding plates and in the welds between the gusset plate and yielding plates became the controlling fa ilure mechanism. Table 4.1 A Series summary of tension, displacement, and failure modes. Sample # Test Name Max Force Displacement Failure Mode Tens. (Kip) Comp. (Kip) Tens. (in) Comp. (in) A1 3/8" PL, 3.5" Square Bushing 19.3 17.9 1.2 1.2 Side gusset plates buckled in compression, stud flanges buckled A3 3/8" PL, 2" Square Bushing 14.7 14.3 0.8 0.6 Gusset pl buckled in compression, gusset fractured in tension A4 3/8" PL, 2" Square Bushing 15.8 14.7 0.8 0.8 Gusset pl buckled in compression A5 3/8" PL, 2.75" Square Bushing 17.8 16.7 0.6 0.6 Gusset pl buckled in compression A6 3/8" PL, 3.5" Square Bushing 16.8 19.9 0.4 0.4 Gusset pl buckled in compression A7 3/8" PL, 2.75" Square Bushing 19.7 17 1 1 Gusset pl buckled in compression, then fractured in tension A8 3/8" PL, 2" Square Bushing 16.5 13.2 0.8 0.8 Gusset pl buckled in compression A9 3/8" PL, 2.75" Square Bushing 19 18.9 0.6 0.6 Gusset pl buckled in compression at 18k when buckling restraint disengaged A10 3/8" PL, 2.75" Square Bushing 17.4 16.7 0.4 0.4 Gusset pl buckled in compression when buckling restraint disengaged A11 3/8" PL, 2.75" Square Bushing 20.1 18.2 1 1 Gusset buckled in compression at contact with loaf, yield pl fractured at edge of pl washer in tension, gusset to stud weld failed A12 3/8" PL, 2" Square Bushing 15.9 24.5 1.2 1.2 Yield pl fractured at edge of pl washer, gusset to stud weld failed, gusset to yield plate weld fractured A13 3/8" PL, 3.5" Square Bushing 27.8 21.6 1 1 failure at bottom of slot welds

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47 A14 3/8" PL, 3.5" Square Bushing 24.9 22.8 1 1 Stud flange buckled and stud to gusset welds fractured, yield pl fractured at edge of pl washer A15 3/8" PL, 3.5" Square Bushing 26 22.2 1 1 Stud flange buckled and stud to gusset welds fractured, yield pl fractured at edge of pl washer A16 3/8" PL, 2.75" Square Bushing 20 24.5 1 1 Stud flange buckled and stud to gusset welds fractured, yield pl fractured at edge of pl washer A17 3/8" PL, 2" Square Bushing 16.6 26.9 1.2 1.2 Stud flange buckled and stud to gusset welds fractured, yield pl fractured at edge of pl washer A18 3/8" PL, 1.5" Round Bushing 14.2 13.7 1.2 1.2 Yield pl to gusset weld fractured 4.2 .2 T series The backbone curves in Figures 4.11 through 4.15 show the envelope of behavior for the T series connections. They compare behavior of the connections by looking at how the different variables of either thickness of the HSS tube wall, or dimension and shap e of bushing affects the results. Figures 4.11 and 4.12 compare the behavior of bushing geometry affects for a particular thickness. The larger bushings yield larger forces but smaller displacement capacity. The results are consistent for the two thickne sses of HSS tube tested. A small horizontal shift in the T1 and T2 test result s can be observed at the origin of the graph. The wedges discussed earlier were implemented as a standard test procedure afterwards.

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48 Figure 4. 11 T series back bone curve for thick HSS section. -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (Kip) Displacement (in) T Series. 1/4" thick HSS T1 T2 T3 3.5" square bushing 2" rectangle bushing 1.5" round bushing

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49 Figure 4. 12 T rectangular, Figures 4.13, 4.14, and 4.15 compare the behavior HSS wall thickness affects for a particular bushing geometry. Higher forces are able to be resisted for thicker HSS sections. This is demonstrated for all three bushings types t case when comparing results fo -35 -25 -15 -5 5 15 25 35 45 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (Kip) Displacement (in) T Series. 5/16" thick HSS T4 T5 T6 T7 T8 T9 3.5" Square 2" Rectanguar 1.5" Round

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50 Figure 4. 13 T thick HSS. -35.00 -25.00 -15.00 -5.00 5.00 15.00 25.00 35.00 45.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (kip) Displacement (in) T Series. 3.5" Square Bushing T1 T7 T6 5/16" HSS 1/4" HSS

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51 Figur e 4. 14 T thick HSS. -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) T Series. 2" Rectangular Bushing T3 T4 T8 5/16" HSS 1/4" HSS

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52 Figure 4. 15 T thick HSS. Table 4.2 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the T series. A summary of the primary failure modes is also included. In the version 1 of the connection the CFS of the extended fl ange of the stud fractured or had large local buckling effects. This eliminated the version T series of connection from further review. The version 2 connections using the side gusset plates performed better. While local buckling was observed in the gus sets and the stud the failure mechanism was in the HSS, either in the corners of the tube or along the bushing. observed in testing, the displacements for samples wi th the square and rectangular shape -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) T Series. 1.5" Round Bushing T2 T5 T9 5/16" HSS 1/4" HSS

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53 determined to be too thin to provide sufficient for ce resistance in a connection. Table 4.2 T Series summary of tension, displacement, and failure modes. Sample # Test Name Max Force Displacement Failure Mode Tens. (Kip) Comp. (Kip) Tens. (in) Comp. (in) T1 1/4" HSS, 3.5" Square Bushing 23 17.6 0.4 0.4 Buckle and fracture at CFS extended flange T2 1/4" HSS, 1.5" Round Bushing 12.1 9.3 1.6 1.6 Side gussets buckled, HSS fractured at round washer T3 1/4" HSS, 2" Square Bushing 16 11 0.8 0.8 Side gussets buckled, HSS fractured at washer pl T4 5/16" HSS, 2" Square Bushing 23.4 17 1 1 Side gussets buckled, HSS fractured at corners T5 5/16" HSS, 1.5" Round Bushing 19.8 13 1.2 1.2 Side gussets buckled, HSS fractured at corners T6 5/16" HSS, 3.5" Square Bushing 40.4 27.3 0.8 0.8 HSS fractured at washer pl T7 5/16" HSS, 3.5" Square Bushing 41 27.9 0.6 0.6 HSS fractured at washer pl T8 5/16" HSS, 2" Square Bushing 24.5 16 0.8 0.8 Side gussets buckled, HSS fractured at washer pl T9 5/16" HSS, 1.5" Round Bushing 20.5 12 1.2 1.2 Side gussets buckled, HSS fractured at corners 4.2 .3 E series. The results from the A and T series tests led the elimination of all but two bushings used to study

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54 provided marginal data in making decision for future connectio ns design or analysis. Like the T s eries connections Figures 4. 16 through 4.20 examines the behavior of the E series connections by comparing bushing geometry for a particular HSS thickness and the behavior due to thickness for a particular bushing geome try. We see very similar behavior to the T series. The larger bushing provides greater force resistance and the smaller one allows greater ductility. Thicker HSS sections provide more force resistance than thinner for the same size bushing. The ductili ty is fairly consistent for a particular bushing regardless of HSS thickness. Figure 4. 16 E rectangular -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (kip) Displacement (in) E Series. 3/16" HSS E1 E4 E7 E10 3" Rectangular 1.5" Round

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55 Figure 4. 17 E rectangular -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) E Series. 1/4" HSS E2 E5 E8 E11 3" Rectangular 1.5" Round

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56 Figure 4. 18 E rectangular round bushings. -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) E Series. 5/16" HSS E3 E6 E9 E12 PE1 PE2 PE3 3" Square 1.5" Round

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57 Figure 4. 19 E series back bone curve for bushing. Comparing -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement E Series with 3" rectangular bushings E4 E5 E6 E7 E8 E9 PE1 PE2 5/16" HSS 1/4" HSS 3/16" HSS

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58 Figure 4. 20 E Table 4.3 shows the maximum forces and displacements in the tension and compression cycles that each sample a chieved for the E series. A summary of the primary failure modes is also included. Three primary failure s were observed in this series of connection. F racture in the CFS of the stud above the weld connecting the stud to the top of the HSS and in its flanges due to bending from the eccentric loading was observed in 4 samples. Fracture of the HSS tube in the corners, along the edges of the bushing or both was the primary mode of failure. -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (kip) Displacement (in) E Series. 1.5" Round Bushings E1 E2 E3 E10 E11 E12 E15 5/16" 1/4" 3/16/"

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59 Table 4.3 E Series summary of tension, displacement, and failure modes. Sample # Test Name Max Force Displacement Failure Mode Tens. (Kip) Comp. (Kip) Tens. (in) Comp. (in) E1 3/16" HSS, 1.5" Round Bushing 8.3 3 1.4 1.4 Local and global stud buckling after contact with loaf, HSS tore at washer E2 1/4" HSS, 1.5" Round Bushing 14.1 6 1.4 1.4 Local and global stud buckling after contact with loaf, HSS tore at washer and corners E3 5/16" HSS, 1.5" Round Bushing 18.9 12 1.4 1.2 Local and global stud buckling after contact with loaf, HSS tore at washer and corners, track flange tear adj to HSS top corners E4 3/16" HSS, 3" Square Bushing 13.3 5.9 0.6 0.6 HSS fractured at edge of 3" plate E5 1/4" HSS, 3" Square Bushing 21.8 15 0.8 0.8 HSS fractured at edge of 3" plate E6 5/16" HSS, 3" Square Bushing 27.8 22.3 0.6 0.4 Stud wall fractured above stud to HSS weld E7 3/16" HSS, 3" Square Bushing 13.4 6.5 0.6 0.6 HSS tube fractured at edge of 3" plate E8 1/4" HSS, 3" Square Bushing 22.1 14 0.8 0.8 HSS tube fractured at edge of 3" plate E9 5/16" HSS, 3" Square Bushing 28.6 21.5 0.6 0.6 Local and global stud buckling, the Stud wall fractured above stud to HSS weld E10 3/16" HSS, 1.5" Round Bushing 8 3 1.6 1.4 HSS tearout at 1.5" round washer E11 1/4" HSS, 1.5" Round Bushing 13.6 7 1.4 1.2 HSS tearout at 1.5" round washer, HSS bot corners cracked and fractured E12 5/16" HSS, 1.5" Round Bushing 18.9 12 1.4 1.4 HSS tearout at 1.5" round washer, HSS cracked at bot corners, stud to HSS weld cracked, stud buckled after contact w/ loaf

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60 PE1 5/16" HSS, 3" Square Bushing 29.8 20.5 0.6 0.6 Stopped test when upper test plate began to bend, fractures visible in stud PE2 5/16" HSS, 3" Square Bushing 28.5 21.7 0.6 0.6 Stud metal tore adjacent to weld at top of HSS PE3 5/16" HSS, 1.5" Round Bushing 19.5 12.5 1.4 1.4 HSS tore at washer and fractured at bottom corners 4.2 .4 UC series. While both the T and E series of connection eliminated the local buckling issues associated with the A series, t he complexities of integrating them with a CFS panel ultimately led to the ir rejection. The d evelopment of the UC and UE connections was to maximize the use of CFS and inexpensive steel p late for the yielding mecha nism. Figures 4.21 through 4.25 show the behavior of the UC round bushings were used 1/4 behavior of this followed that of the HSS style connections. Large bushings and thicker plates provide more force resistance than smaller bushings and thinner plates. Small bushings allow for more ductility but ductility is relatively constant for a particular bushing across the tested thicknesses of plate. One item of note is that PUC2 and PUC3 had similar performance to UC5 in displacement and force r esistance but a different shape in their backbone curves. No determination has been found for this. They were constructed by a different manufacturer to test MIG vs flux cored welding. Only 1 of 4 welds securing the gusset to the unreinforced stud was observed with welds were observe d to have any indication of failure in PUC3. This was determined to have negligible effect on the overall performance of that sample.

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61 Figure 4. 21 UC rectangular, and -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) UC Series. 1/4" Plate UC1 UC2 3" Rectangular 1.5" Round

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62 Figure 4. 22 UC -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) UC Series. 5/16" Plate UC3 UC4 3" Rectangular 1.5" Round

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63 Figure 4. 23 UC -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) UC Series. 3/8" Plate UC6 PUC1 PUC2 PUC3 UC5 3" Rectangular 1.5" Round

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64 Figure 4. 24 UC yielding plate -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (Kip) Displacement (in) UC Series 3" Rectangular Bushing UC1 UC4 UC5 PUC1 PUC2 3/8" PL 5/16" PL 1/4" PL

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65 Figure 4. 25 UC yielding plate Table 4.4 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the UC series. A summary of the primary failure modes is also included. The primary failure observed was a fracture at the 90 degree bend in the U shaped gusset. Only one sample had complete yield plate fracture without U gusset fracture. Table 4.4 UC Series summary of tension, displacement, and failure modes. Sample # Test Name Max Force Displacement Failure Mode Tens. (Kip) Comp. (Kip) Tens. (in) Comp. (in) UC1 1/4" PL, 3" Square Bushing 16.9 9.5 1.2 1 Beveled stud edges buckled, yield pl fractured at washer pl edges -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) UC Series. 1.5" Round Bushing UC2 UC3 UC6 PUC3 1/4" PL 5/16" PL 3/8" PL

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66 UC2 1/4" PL, 1.5" Round Bushing 10.6 6 1.4 1.4 Beveled stud edges buckled, yield pl fractured at washer, U shape pl fractured at corner UC3 5/16" PL, 1.5" Round Bushing 13.7 8 1.2 1.2 Fractured U shape pl at corner, yield pl began fracturing at bolt CL UC4 5/16" PL, 3" Square Bushing 27 14.5 1 1 Yield pl fractured at bushing edges UC5 3/8" PL, 3" Square Bushing 28.3 26 0.6 0.6 Fractured U shape pl at corner UC6 3/8" PL, 1.5" Round Bushing 19.4 14 1.4 1.4 Fractured U shape pl at corner PUC1 3/8" PL, 3" Square Bushing 22.7 22.5 0.4 0.4 Fractured U shape pl at corner PUC2 3/8" PL, 3" Square Bushing 23.9 22.2 0.4 0.4 Fractured U shape pl at corner PUC3 3/8" PL, 1.5" Round Bushing 19.9 12 1.8 1.8 Weld failure at gusset/bot stud, fractured U shape pl at corner, punch out of 3/8" yield pl at round washer 4.2 .5 UE series. Figures 4.26 through 4.29 show almost identical results to the UC connections. Based on results previously due to the lower force resisting capacity. O The global behavior of this connection followed the pattern of the previous series. Thicker yielding plates can generate higher force resistance for a specific bushing si ze but bushing.

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67 Figure 4. 26 UE gs. -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) UE Series. 5/16" Yield Plate. UE3 UE4 3" Rectangular 1.5" Round

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68 Figure 4. 27 U E -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (kip) Displacement (in) UE Series. 3/8" Yield Plate. UE1 UE2 3" Rectangular 1.5" Round

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69 Figure 4. 28 UE -30 -20 -10 0 10 20 30 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 Force (kip) Displacement (in) UE Series. 3" Rectangular Bushing. UE2 UE4 3/8" PL 5/16" PL

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70 Figure 4. 2 9 UE thick yielding plates. Table 4.5 shows the maximum forces and displacements in the tension and compression cycles that each sample achieved for the UC series. A summary of the primary failure modes is also included. The only failure observed was a fracture at the 90 degre e bend in the U shaped gusset. The eccentricity in the connection did not contribute to any failure in the connection nor did it significantly decrease capacity or ductility. This connection has demonstrated the most promise to be integrated with a panel for construc tion, based on geometry, materials used and performance, if the U shaped gusset fracture can be eliminated as a failure mode. -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (kip) Displacement (in) UE Series. 1.5" Round Bushing. UE1 UE3 3/8" PL 5/16" PL

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71 Table 4.5 UE Series summary of tension, displacement, and failure modes. Sample # Test Name Max Force Displacement Failure Mode Tens. (Kip) Comp. (Kip) Tens. (in) Comp. (in) UE1 3/8" PL, 1.5" Round Bushing 19 16.1 1.2 1.2 Fractured U shape pl at corner UE2 3/8" PL, 3" Square Bushing 23.8 23.7 0.4 0.4 Fractured U shape pl at corner UE3 5/16" PL, 1.5" Round Bushing 13.4 8 1.2 1.2 Fractured U shape pl at corner UE4 5/16" PL, 3" Square Bushing 22.3 16 0.8 0.8 Fractured U shape pl at corner 4.2 .6 TN S eries. The TN series of connections was developed to explore the behavior of a connection using an HSS section that had a portion of its surface removed so that a CFS stud could be 4.30 The behavior is similar to the T and E series.

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72 Figure 4. 30 TN Table. 4.6 Summarizes the results for the TN connections. The singular failure mode was fracture of the HSS tube along the edge of the bushing. While the performance of this connection is marginally better in terms of force resistance and ductility the difficulty in integrating this design with panel construction is sufficient to eliminate it as a design for further study as with the T and E series connections. -30.00 -20.00 -10.00 0.00 10.00 20.00 30.00 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 Force (kip) Displacement (in) TN Series. 1/4" HSS with 1.5" round and 3" square bushings. TN1 TN2 TN3 TN4 TN5 TN6 3" Rectangular 1.5" Round

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73 Table 4.6 TN Series summary of tension, displacement, and failure modes. Sample # Test Name Max Forc e Displacement Failure Mode Tens. (Kip) Comp. (Kip) Tens. (in) Comp. (in) TN1 1/4" HSS, 1.5" Round Bushing 11.4 7 1.4 1.4 HSS fractured at edge of bushing TN2 1/4" HSS, 3" Square Bushing 20.8 12.6 0.6 0.6 HSS fractured at edge of bushing TN3 1/4" HSS, 1.5" Round Bushing 11.6 6.4 1.4 1.4 HSS fractured at edge of bushing TN4 1/4" HSS, 3" Square Bushing 20.5 12.7 0.6 0.6 HSS fractured at edge of bushing TN5 1/4" HSS, 1.5" Round Bushing 11.4 6.5 1.4 1.4 HSS fractured at edge of bushing TN6 1/4" HSS, 3" Square Bushing 19.8 12.5 0.6 0.6 HSS fractured at edge of bushing 4.3 Theoretical vs experimental load values. This section discuss the theoretical values calculated for forces applied to obtain plastic hinges in a yield plate. Figure 4.32 shows the concept of a plastic hinge forming at the edge of a bushing in a yielding plate.

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74 Figure 4. 31 Illustration of plastic hinges forming in a yield plate around a bushing. Large displacements lead to < x The variables in figure 4.31 are defined below: l w b is the width of the bushing. x is the length of the moment arm.

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75 is the length of the moment arm perpendicular to force P. x, this is a factor in large displacements. h is the height or thickness of the yielding plate. f y is the yield strength of the yielding plate. P is the applied force. The force applied to the edges of a yield pla te times the distance from the point of application gives us an applied moment that will ultimately bend the plate adjacent to the bushing. Taking the distance from the edge of the plate to the edge of the bushing gives us the maximum possible length of moment arm. This distance is not observed in experiments. The plastic hinge does not form as a small point, but encompasses a region. In the case of a cantilever beam with a load applied at the free end, the largest bending moment is at the fixed end support. As the force increases beyond the point where yielding occurs at the base of the support, t he plastic hinge spreads towards the free end in a parabolic pattern (Beer et al. 2009). For the purpose of this research it is assumed that the width of the plastic hinge is equal to the thickness of the yield plate. The estimate for our moment arm length x is from where the force is applied at the edge of the plate to the edge of the bushing In some samples the true length of the yield plate is up to arms. In addition, at large vertical displacements of the sample the perpendicular distance from the applied force to the edge of the bus h ing is reduced. This is discussed in Section 4.1 and illustrated in F i gure 4.3 Equation 1 below for the applied moment is equal to the (Eq. 4.1)

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76 The applied force is resisted by the strength of the material in forming a plastic hinge where the whole cross section is plastically deforming in either tension or compression. The plastic moment M p is equal to the yield strength of the material multiplied by its plastic section modulus. It is a direct function of the yield strength of the mater ial, the width of the yield plate, and the square of the height of the yield plate as shown in equation 2. (Eq. 4.2) Setting the applied moment equal to the plastic moment and solving for force P results in equation 3 below. (Eq. 4.3) This force, P is what is theoretically required to form a plastic hinge on one side of the bushing. Since we are forming two plastic hinges the force applied by the MTS should be approximately equal to two times P Another factor that needs to be accounted for is the strength of the material. Coupon testing of the yield plate steel shows a higher yield strength than the nominal 50 ksi specified. Figure 4.32 shows a stress vs strain graph for a coupon test of yield plate material

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77 Figure 4. 32 Tested yield stress of 50 ksi nominal, steel plate. This indicates that the actual yield stress is 61ksi or 20% more than nominal. Figure 4.33 shows a graph of stress vs strain for the sample material through its failure.

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78 Figure 4. 33 Stress strain curve for 50ksi nominal steel. Because the yield plate was cycled through large displacements until it fractured we ex perienced strain hardening in the plastic hinge. This is illustrat ed in the peak values shown on Figure 4.33 of 73 ksi. For the purpose of calculations 70 ksi will be used. The table below lists a range for theoretical values for applied force compared t o the experimental values obtai ned for the UC and the UE samples. The samples using HSS tube sections have been eliminated as a viable option due to the smaller deflections to reach their maximum resistance before their performance degrades.

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79 Table 4.7 Comparison of Theoretical to Actual Forces in connections for various plate thicknesses. Yield Plate Thickness (in) Bushing size (in) Theoretical force applied (kip) Actual force applied (kip) 3/8" 1.5 11.7 19.2 3 18.9 28.3 5/16" 1.5 8.8 13.7 3 15.2 27 1/4" 1.5 5.0 12 3 7.8 19.6 The actual applied force f rom the MTS is much greater than that obtained from an analysis of just a plastic hinge in the yielding plate In bushing it is 60%. To determine the difference in capacity between analytical and actual one must look at the deformed shape of the yield plate at its maximum displacement, shown in F igure 4.34 below. At large displacements the CFS is exposed to tensile forces as well as bending. Even in a compression cycle the CFS is in tension. That tension force can be resolved into horizontal and vertical components. If the difference in capacity is due to this tension force one can calculate the stress the CFS is under. As long as the stress is be low the yield stress of the CFS, this is a reasonable conclus ion. With a total area of 0.46 square inches a nd a nominal yield strength of 5 0 ksi. Calculations indicate t he CFS of the U shaped gusset can handle a 25 kip tensile load without yielding. As mentioned in chapter 1 modeling the behavior of this assembly is complicated and there are interactions that are difficult to analyze. The experimental testing of samples has allowed us to determine a behavioral boundaries for further investigation.

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80 F igure 4. 34 Yield plate in large compression displacement.

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81 CHAPTER V CONCLUSION 5.1 Lessons Learned The concept of using a yielding plate to introduce ductility in a connection is viable. Displacement and force targets were achieved. Thicker bushings are required on the top side of the yield plate to prevent them from bending in a tension cycle. Round bushings are preferred over rectangular bushings. Failure in the yield plate due to the rectangular bushings initiates along their contact line uniformly and propagates through the thickness of the steel until complete fracture. While the rectangular bushings generally generate more force resistance, they reach a peak then failure occurs within one or subseque nt trailing cycles. The complete fractures are generally sudden, thus making it an undesirable failure mode. In the case of a round bushing fracture in the yield plate begins at the edges of the washer closest to either the HSS wall or gusset that transfers the vertical load. The fracture then propagates to the edges of the yield plate. This results in connection that can withstand more cycles and higher displacements prior to failure. Loss of capacity is much more gradual even when e xposed to larger trailing cycles. For the purpose of resisting seismic loads ductility is much more important than higher force resisting capacity. 5.2 Recommendations for further investigation The UE is the preferred connection based on its similar p erformance to comparable thickness tube sections. The preference is based primarily on material cost of the connection, and ease of fabrication. It integrates most easily with the current panel fabrication method. It also is compatible for fabrication u sing robotic welding methods in the future. To ensure

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82 proper performance of this connection in a seismic load resistant system, a fatigue study of the connection should be conducted to ensure performance over the lifecycle of a structure. Further study of the welds in the connections could be conducted to 1) ensure performance requirements meet a design criteria and 2) to reduce required length of welds in CFS connections to the minimum about required for structural performance in order to maximize the economy of the fabrication process.

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83 REFERENCES AISC (American Institute of Steel Construction). (2012) Seismic Design. 2 nd Edition, United States of America. https://www.govcon.com/doc/annual us earthquake losses estimated at 44b 0001 (June 29, 2017) ASCE (American Society of Civil Engineers). (2010) Minimum Design Loads for Buildings and Other Structures Standard ASCE/SEI 7 10. Second printing. ASCE, Reston, VA. Beer, F P., et.al. (2009). Mechanics of Materials. McGraw Hill Publishing. 5 th edition. New York, NY. Berg, G V. (1983). Seismic Design Codes and Procedures. The Earthquake Engineering Research Institute. Berkeley, CA. Blog (January 17, 2009). http://seismo.berkeley.edu/blog/2009/01/17/today in earthquake history northridge 1994.html (July 19, 2017). Connection Design Design Requirements. Version II. http://www.steel insdag.org/teachingmaterial/chapter29.pdf (June 29, 2017) Journal of Performance of Constructed Facilities ASCE 04014018 1 FEMA. (2009). FEMA P 675. Washington, DC. Protocol for Woo 02. Lee, M.S. formed steel braced frames Int. J. Steel Struct. 10(3), 305 316. London, J. http://www.nbcnews.com/id/12319421/ns/us_news san_franci sco_earthquake_1906/t/how much would quake cost today/#.WXC8mYTythE (June 29, 2017). Madsen, R L. et al. (2016). Seismic Design of Cold Formed Steel Lateral Load Resisting Systems: A Guide for Practicing Engineers. NEHRP Seismic Design Technical Brief No.12. Available at: http://dx.doi.org/10.6028/NIST.GCR.16 917 38 Mason, B https://www.wired.com/2008/11/gallery deadly earthquake/ Nikitin, G. (Photographer) (1989). Collapsed Building, Loma Prieta Earthquake. The San Francisco Examiner (October 16, 2014). https://archives.sfexaminer.com/sanfrancisco/1989 loma prieta temblor shook up need for earthquake solutions/C ontent?oid=2909383 (July 19, 2017).

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84 Sabol, T. A., PhD, SE. (2010). Seismic Design Manual and Application of the 2010 AISC Seismic Provisions. The American Institute of Steel Construction. Los Angeles, CA.

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85 APPENDIX A Before and after photographs of test samples.

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86 A.1 A series s amples Figure A 1 Sample A1 before testing Figure A 2 Sample A1 after testing

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87 Figure A 3 Sample A2 before testing. Figure A 4 Sample A2 after testing

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88 Figure A 5 Sample A3 before testing. Figure A 6 Sample A3 after testing

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89 Figure A 7 Sample A4 before testing Figure A 8 Sample A4 after testing

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90 Figure A 9 S ample A5 before testing Figure A 10 Sample A5 after testing

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91 Figure A 11 Sample A6 before testing. Figure A 12 Sample A6 after testing.

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92 Figure A 13 Sample A7 before testing. Figure A 14 Sample A7 after testing.

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93 Figure A 15 Sample A8 before testing. Figure A 16 Sample A8 after testing.

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94 Figure A 17 Sample A9 before testing Figure A 18 Sample A9 after testing

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95 Figure A 19 Sample A10 before testing. Figure A 20 Sample A10 after testing.

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96 Figure A 21 Sample A11 before testing. Figure A 22 Sample all after testing.

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97 Figure A 23 Sample A12 before testing Figure A 24 Sample A12 after testing

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98 Figure A 25 Sample A13 before testing. Figure A 26 Sample A13 after testing.

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99 Figure A 27 Sample A14 before testing. Figure A 28 Sample A14 after testing.

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100 Figure A 29 Sample A15 before testing. Figure A 30 Sample A15 after testing.

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101 Figure A 31 Sample A16 before testing. Figure A 32 Sample A16 after testing.

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102 Figure A 33 Sample A17 before testing. Figure A 34 Sample A17 after testing.

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103 Figure A 35 Sample A18 before testing. Figure A 36 Sample A18 after testing.

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104 A.2 T series s amples Figure A 37 Sample T1 before test. Figure A 38 Sample T1 after test.

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105 Figure A 39 Sample T2 before test. Figure A 40 Sample T2 after test.

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106 Figure A 41 Sample T3 before test. Figure A 42 Sample T3 after test.

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107 Figure A 43 Sample T4 before test. Figure A 44 Sample T4 after test.

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108 Figure A 45 Sample T5 before test. Figure A 46 Sample T5 after test.

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109 Figure A 47 Sample T6 before test. Figure A 48 Sample T6 after test.

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110 Figure A 49 Sample T7 before test. Figure A 50 Sample T7 after test.

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111 Figure A 51 Sample T8 before test. Figu re A 52 Sample T8 after test.

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112 Figure A 53 Sample T9 before test. Figure A 54 Sample T9 after test.

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113 A.3 E series samples Figure A 55 Sample E1 before test. Figure A 56 Sample E1 after test

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114 Figure A 57 Sample E2 before test. Figure A 58 Sample E2 after test.

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115 Figure A 59 Sample E3 before test. Figure A 60 Sample E3 after test.

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116 Figure A 61 Sample E4 before test. Figure A 62 Sample E4 after test.

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117 Figure A 63 Sample E5 before test. Figure A 64 Sample E5 after test.

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118 Figure A 65 Sample E6 before test. Figure A 66 Sample E6 after test.

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119 Figu re A 67 Sample E7 before test. Figure A 68 Sample E7 after test.

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120 Figure A 69 Sample E8 before test. Figure A 70 Sample E8 after test.

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121 Figure A 71 Sample E9 before test. Figure A 72 Sample E9 after test.

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122 F igure A 73 Sample E10 before test. Figure A 74 Sample E10 after te st.

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123 Figure A 75 Sample E11 before test. Figure A 76 Sample E11 after test.

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124 Figure A 77 Sample E12 before test. Figure A 78 Sample E12 after test.

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125 A.4 UC series samples Figure A 79 Sample UC1 before test. Figure A 80 Sample UC1 after test.

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126 Figure A 81 Sample UC2 before test. Figure A 82 Sample UC2 after test.

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127 Figure A 83 Sample UC3 before test. Figure A 84 Sample UC3 after test.

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128 Figure A 85 Sample UC4 before test. Figure A 86 Sample UC4 after test.

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129 Figure A 87 Sample UC5 before test. Figure A 88 Sample UC5 after test.

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130 Figure A 89 Sample UC6 before test. Figure A 90 Sample UC6 after test.

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131 A.5 UE series samples Figure A 91 Sample UE1 before test. Figure A 92 Sample UE1 after test.

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132 Figure A 93 Sample UE2 before test. Figure A 94 Sample UE2 after test.

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133 Figure A 95 Sample UE3 before test. Figure A 96 Sample UE3 after test.

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134 Figure A 97 Sample UE4 before test. Figure A 98 Sample UE4 after test.

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135 A.6 PUC series samples Figure A 99 Sample PUC1 before test. Figure A 100 Sample PUC1 after test.

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136 Figure A 101 Sample PUC2 before test. Figure A 102 Sample PUC2 after test.

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137 Figure A 103 Sample PUC3 before tes t. Figure A 104 Sample PUC3 after test.

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138 A.7 PE series samples Figure A 105 Sample PE1 before test. Figure A 106 Sample PE1 after test.

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139 Figure A 107 Sample PE2 before test. Figure A 108 Sample PE2 after test.

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140 Figure A 109 Sample PE3 before test. Figure A 110 Sample PE3 after test.

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141 A.8 TN series samples Figure A 111 Sample TN1 before test. Figure A 112 Sample TN1 after test.

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142 Figure A 113 Sample TN2 before test. Figure A 114 Sample TN2 after test.

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143 Figure A 115 Sample TN3 before test. Figure A 116 Sample TN3 after test.

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144 Figure A 117 Sample TN4 before test. Figure A 11 8 Sample TN4 after test.

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145 Figure A 119 Sample TN5 before test. Figure A 120 Sample TN5 after test.

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146 Figure A 121 Sample TN6 before test. Figure A 122 Sample TN6 after test.

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147 APPENDIX B Force, Displacement, and Hysteresis graphs

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148 B.1 A Series Graphs Figure B 1 Sample A1, force vs displacement.

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149 Figure B 2 Sample A1, displacement vs time. Figure B 3 Sample A1, load vs time.

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150 Figure B 4 Sample A3, force vs displacement.

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151 Figure B 5 Sample A3, displacement vs time. Figure B 6 Sample A3, force vs time.

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152 Figure B 7 Sample A4, force vs displacement.

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153 Figure B 8 Sample A4, displacement vs time. Figure B 9 Sample A4, force vs time.

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154 Figure B 10 Sample A5, force vs displacement.

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155 Figure B 11 Sample A5, displacement vs time. Figure B 12 Sample A5, force vs time.

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156 Figure B 13 Sample A6, force vs displacement.

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157 Figure B 14 Sample A6, displacement vs time. Figure B 15 Sample A6 force vs time.

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158 Figure B 16 Sample A7, force vs displacement

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159 Figure B 17 Sample A7, displacement vs time. Figure B 18 Sample A7, force vs time.

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160 Figure B 19 Sample A8, force vs displacement.

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161 Figure B 20 Sample A8, displacement vs time. Figure B 21 Sample A8, force vs time.

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162 Figure B 22 Sample A9 force vs displacement.

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163 Figure B 23 Sample A9, displacement vs time. Figure B 24 Sample A9 force vs time.

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164 Figure B 25 Sample A10 force vs displacement.

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165 Figure B 26 Sample A10, displacement vs time. Figure B 27 Sample A10 force vs time.

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166 Figure B 28 Sample A11 force vs displacement.

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167 Figure B 29 Sample A11, displacement vs time. Figure B 30 Sample A11 force vs time.

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168 Figure B 31 Sample A12 force vs displacement.

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169 Figure B 32 Sample A12, displacement vs time. Figure B 33 Sample A12 force vs time.

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170 Figure B 34 Sample A13 force vs displacement.

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171 Figure B 35 Sample A13, displacement vs time. Figure B 36 Sample A13 force vs time.

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172 Figure B 37 Sample A14 force vs displacement.

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173 Figure B 38 Sample A14, displacement vs time. Figure B 39 Sample A14 force vs time.

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174 Figure B 40 Sample 15 force vs displacement.

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175 Figure B 41 Sample A15, displacement vs time. Figure B 42 Sample A15 force vs time.

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176 Figure B 43 Sample A16, force vs displacement.

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177 Figure B 44 Sample A8, displacement vs time. Figure B 45 Sample A16 force vs time.

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178 Figure B 46 Sample A17 force vs displacement.

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179 Figure B 47 Sample A17, displacement vs time. Figure B 48 Sample A17 force vs time.

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180 Figure B 49 Sample A 1 8, force vs displacement.

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181 Figure B 50 Sample A18, displacement vs time. Figure B 51 Sample A18 force vs time.

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182 B.2 T Series Graphs Figure B 52 Sample T1 force vs displacement.

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183 Figure B 53 Sample T1, displacement vs time. Figure B 54 Sample T1 force vs time.

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184 Figure B 55 Sample T2 force vs displacement.

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185 Figure B 56 Sample T2, displacement vs time. Figure B 57 Sample T2 force vs time.

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186 Figure B 58 Sample T3 force vs displacement.

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187 Figure B 59 Sample T3, displacement vs time. Figure B 60 Sample T3 force vs time.

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188 Figure B 61 Sample T4 force vs displacement.

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189 Figure B 62 Sample T4, displacement vs time. Figure B 63 Sample T4 force vs time.

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190 Figure B 64 Sample T5 force vs displacement.

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191 Figure B 65 Sample T5, displacement vs time. Figure B 66 Sample T5 force vs time.

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192 Figure B 67 Sample T6 force vs displacement.

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193 Figure B 68 Sample T6, displacement vs time. Figure B 69 Sample T6 force vs time.

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194 Figure B 70 Sample T7 force vs displacement.

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195 Figure B 71 Sample T7, displacement vs time. Figure B 72 Sample T7 force vs time.

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196 Figure B 73 Sample T 8, force vs displacement.

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197 Figure B 74 Sample T8, displacement vs time. Figure B 75 Sample T8 force vs time.

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198 Figure B 76 Sample T9 force vs displacement.

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199 Figure B 77 Sample T9, displacement vs time. Figure B 78 Sample T9 force vs time.

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200 B.3 E Series Graphs Figure B 79 Sample E1 force vs displacement.

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201 Figure B 80 Sample E1, displacement vs time. Figure B 81 Sample E1 force vs time.

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202 Figure B 82 Sample E2 force vs displacement.

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203 Figure B 83 Sample E2, displacement vs time. Figure B 84 Sample E2 force vs time.

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204 Figure B 85 Sample E3 force vs displacement.

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205 Figure B 86 Sample E3, displacement vs time. Figure B 87 Sample E3 force vs time.

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206 Figure B 88 Sample E4 force vs displacement

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207 Figure B 89 Sample E4, displacement vs time. Figure B 90 Sample E4 force vs time.

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208 Figure B 91 Sample E5 force vs displacement.

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209 Figure B 92 Sample E5, displacement vs time. Figure B 93 Sample E5 force vs time.

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210 Figure B 94 Sample E6 force vs displacement.

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211 Figure B 95 Sample E6, displacement vs time. Figure B 96 Sample E6 force vs time.

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212 Figure B 97 Sample E7 force vs displacement.

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213 Figure B 98 Sample E7, displacement vs time. Figure B 99 Sample E7 force vs time.

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214 Figure B 100 Sample E8 force vs displacement.

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215 Figure B 101 Sample E8, displacement vs time. Figure B 102 Sample E8, force vs time.

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216 Figure B 103 Sample E9 force vs displacement.

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217 Figure B 104 Sample E9, displacement vs time. Figure B 105 Sample E9 force vs time.

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218 Figure B 106 Sample E10 force vs displacement.

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219 Figure B 107 Sample E10, displacement vs time. Figure B 108 Sample E10 force vs time.

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220 Figure B 109 Sample E11 force vs displacement.

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221 Figure B 110 Sample E11, displacement vs time. Figure B 111 Sample E11 force vs time.

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222 Figure B 112 Sample E12 force vs displacement.

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2 23 Figure B 113 Sample E12, displacement vs time. Figure B 114 Sample E12 force vs time.

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224 Figure B 115 Sample PE1 force vs displacement.

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225 Figure B 116 Sample PE1, displacement vs time. Figure B 117 Sample PE1 force vs time.

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226 Figure B 118 Sample PE2 force vs displacement.

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227 Figure B 119 Sample PE2, displacement vs time. Figure B 120 Sample PE2 force vs time.

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228 Figure B 121 Sample PE3 force vs displacement.

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229 Figure B 122 Sample PE3, displacement vs time. Figure B 123 Sample PE3 force vs time.

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230 B.4 UC Series Graphs Figure B 124 Sample UC1 force vs displacemen t.

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231 Figure B 125 Sample UC1, displacement vs time. Figure B 126 Sample UC1 force vs time.

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232 Figure B 127 Sample UC2 force vs displacement.

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233 Figure B 128 Sample UC2, displacement vs time. Figure B 129 Sample UC2 force vs time.

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234 Figure B 130 Sample UC3 force vs displacement.

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235 Figure B 131 Sample UC3, displacement vs time. Figure B 132 Sample UC3 force vs time.

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236 Figure B 133 Sample UC4 force vs displacement.

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237 Figure B 134 Sample UC4, displacement vs time. Figure B 135 Sample UC4 force vs time.

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238 Figure B 136 Sample UC5 force vs displacement.

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239 Figure B 137 Sample UC5, displacement vs time. Figure B 138 Sample UC5 force vs time.

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240 Figure B 139 Sample UC6 force vs displacement.

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241 Figure B 140 Sample UC6, displacement vs time. Figure B 141 Sample UC6, force vs time.

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242 Figure B 142 Sample PUC1 force vs displacement.

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243 Figure B 143 Sample PUC1, displacement vs time. Figure B 144 Sample PUC1, force vs time.

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244 Figure B 145 Sample PUC2 force vs displacement.

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245 Figure B 146 Sample PUC2, displacement vs time. Figure B 147 Sample PUC2, force vs time.

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246 Figure B 148 Sample PUC3 force vs displacement.

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247 Figure B 149 Sample PUC3, displacement vs time. Figure B 150 Sample PUC3, force vs time.

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248 B.5 UE Series Graphs Figure B 151 Sample UE1 force vs displacement.

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249 Figure B 152 Sample UE1, displacement vs time. Figure B 153 Sample UE1, force vs time.

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250 Figure B 154 Sample UE2, force vs displacement.

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251 Figure B 155 Sample UE2, displacement vs time. Figure B 156 Sample UE2, force vs time.

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252 Figure B 157 Sample UE3 force vs displacement.

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253 Figure B 158 Sample UE3, displacement vs time. Figure B 159 Sample UE3, force vs time.

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254 Figure B 16 0 Sample UE4 force vs displacement.

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255 Figure B 161 Sample UE4, displacement vs time. Figure B 162 Sample UE4, force vs time.

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256 B.6 TN Series Graphs Figure B 163 Sample TN1 force vs displacement.

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257 Figure B 164 Sample TN1, displacement vs time. Figure B 165 Sample TN1, force vs time.

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258 Figure B 166 Sample TN2 force vs displacement.

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259 Figure B 167 Sample TN2, displacement vs time. Figure B 168 Sample TN2, force vs time.

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260 Figure B 169 Sample TN3, force v s displacement.

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261 Figure B 170 Sample TN3, displacement vs time. Figure B 171 Sample TN3, force vs time.

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262 Figure B 172 Sample TN4, force vs displacement.

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263 Figure B 173 Sample TN4, displacement vs time. Figure B 174 Sample TN4, force vs time.

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264 Figure B 175 Sample TN5 force vs displacement.

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265 Figure B 176 Sample TN5, displacement vs time. Figure B 177 Sample TN5, force vs time.

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266 Figure B 178 Sample TN6 force vs displacement.

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267 Figure B 179 Sample TN6, displacement vs time. Figure B 180 Sample TN6, force vs time.