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Title page

Contents

FOREWORD 2

EXECUTIVE SUMMARY 15

CHAPTER 1. INTRODUCTION 18

BACKGROUND 18

PROJECT OBJECTIVES AND TASKS 20

CHAPTER 2. COMPILATION OF EXISTING INFORMATION 21

REFERENCE MATERIALS 21

INVENTORY OF U.S. CABLE-STAYED BRIDGES 21

CHAPTER 3. ANALYSIS, EVALUATION, AND TESTING 22

MECHANICS OF WIND-INDUCED VIBRATIONS 22

Reynolds Number 22

Strouhal Number 22

Scruton Number 23

Vortex Excitation of an Isolated Cable and Groups of Cables 23

Rain/Wind-Induced Vibrations 24

Wake Galloping for Groups of Cables 25

Galloping of Dry Inclined Cables 26

WIND TUNNEL TESTING OF DRY INCLINED CABLES 27

Introduction 27

Testing 28

Results Summary 29

OTHER EXCITATION MECHANISMS 31

Effects Due to Live Load 31

Deck-Stay Interaction Because of Wind 32

STUDY OF MITIGATION METHODSThe development of recommended design 34

Linear and Nonlinear Dampers 34

Linear Dampers 35

Nonlinear Dampers 36

Field Performance of Dampers 37

Crosstie Systems 39

Analysis 41

Field Performance 44

Considerations for Crosstie Systems 46

Cable Surface Treatment 47

FIELD MEASUREMENTS OF STAY CABLE DAMPING 48

Leonard P. Zakim Bunker Hill Bridge (over Charles River in Boston, MA) 48

Sunshine Skyway Bridge (St. Petersburg, FL) 51

BRIDGE USER TOLERANCE LIMITS ON STAY CABLE VIBRATION 53

CHAPTER 4. DESIGN GUIDELINES 56

NEW CABLE-STAYED BRIDGES 56

General 56

Mitigation of Rain/Wind Mechanism 56

Additional Mitigation 56

Minimum Scruton Number 56

External Dampers 57

Cable Crossties 57

User Tolerance Limits 58

RETROFIT OF EXISTING BRIDGES 58

WORKED EXAMPLES 59

Example 1 59

Example 2 63

CHAPTER 5. RECOMMENDATIONS FOR FUTURE RESEARCH AND DEVELOPMENT 66

WIND TUNNEL TESTING OF DRY INCLINED CABLES 66

DECK-INDUCED VIBRATION OF STAY CABLES 66

MECHANICS OF RAIN/WIND-INDUCED VIBRATIONS 66

DEVELOP A MECHANICS-BASED MODEL FOR STAY CABLE VIBRATION ENABLING THE PREDICTION OF ANTICIPATED VIBRATION CHARACTERISTICS 67

PREDICT THE PERFORMANCE OF STAY CABLES AFTER MITIGATION USING THE MODEL 68

PERFORM A DETAILED QUANTITATIVE ASSESSMENT OF VARIOUS ALTERNATIVE MITIGATION STRATEGIES 69

IMPROVE UNDERSTANDING OF INHERENT DAMPING IN STAYS AND THAT PROVIDED BY EXTERNAL DEVICES 69

IMPROVE UNDERSTANDING OF CROSSTIE SOLUTIONS 70

REFINE RECOMMENDATIONS FOR EFFECTIVE AND ECONOMICAL DESIGN OF STAY CABLE VIBRATION MITIGATION STRATEGIES FOR FUTURE BRIDGES 70

APPENDIX A. DATABASE OF REFERENCE MATERIALS 72

APPENDIX B. INVENTORY OF U.S. CABLE-STAYED BRIDGES 91

APPENDIX C. WIND-INDUCED CABLE VIBRATIONS 96

APPENDIX D. WIND TUNNEL TESTING OF STAY CABLES 110

APPENDIX E. LIST OF TECHNICAL PAPERS 161

APPENDIX F. ANALYTICAL AND FIELD INVESTIGATIONS 163

APPENDIX G. INTRODUCTION TO MECHANICS OF INCLINED CABLES 220

APPENDIX H. LIVE-LOAD VIBRATION SUBSTUDY 231

APPENDIX I. STUDY OF USER COMFORT 263

REFERENCES AND OTHER SOURCES 266

Tables

Table 1. Dry inclined cable testing: Model setup 28

Table 2. Dry inclined cable testing: Damping levels 29

Table 3. Dry inclined cable testing: Surface condition 29

Table 4. Stay and damper properties 38

Table 5. Cable network modes (0-4 Hz) predicted by the model 45

Table 6. Preliminary cable damping measurements: Leonard P. Zakim Bunker Hill Bridge 49

Table 7. Preliminary cable damping measurements from the Sunshine Skyway Bridge 53

Table 8. Data from table 4 63

Table 9. Cable-stayed bridge inventory 91

Table 10. Bridges reporting cable vibration and mitigating measures 109

Table 11. Model setup 123

Table 12. Different damping levels of the model 123

Table 13. Surface condition 123

Table 14. Limited-amplitude motion 129

Table 15. Geometrical and structural characteristics of the Fred Hartman system 184

Table 16. Individual cable frequencies (0-4 Hz) of the A-line side-span stays of the Fred Hartman Bridge (direct measurement) 204

Table 17. Cable network modes (0-4 Hz) predicted by the model (A-line system) 204

Table 18. Stay cable property comparison 229

Table 19. Free independent extensible cable vibration versus theoretical inextensible 235

Table 20. Free independent inextensible cable vibration periods: Theoretical values and values obtained by analysis 237

Table 21. Cable vibration periods and frequencies: Theoretical values and values obtained by analysis 240

Table 22. Vertical displacements due to live load 245

Table 23. Bending moments due to live load 246

Table 24. Cable forces due to live load 247

Table 25. Cable end rotations and deck rotations 248

Figures

Figure 1. Graph. Comparison of wind velocity-damping relation of inclined dry cable 30

Figure 2. Graph. Cable M26, tension versus time (transit train speed = 80 km/h (50 mi/h)) 31

Figure 3. Graph. Time history and power spectral density (PSD) of the first 2 Hz for deck at midspan (vertical direction) 32

Figure 4. Graph. Time history and power spectral density (PSD) of the first 2 Hz for cable at AS24 (in-plane direction) deck level wind speed 33

Figure 5. Deck level wind speed 33

Figure 6. Photo. Damper at cable anchorage 34

Figure 7. Drawing. Taut cable with linear damper 35

Figure 8. Graph. Normalized damping ratio versus normalized damper coefficient: Linear damper 36

Figure 9. Graph. Normalized damping ratio versus normalized damper coefficient (β = 0.5) 37

Figure 10. Photo. Fred Hartman Bridge 38

Figure 11. Photo. Cable crosstie system 40

Figure 12. Photo. Dames Point Bridge 41

Figure 13. Chart. General problem formulation 42

Figure 14. Chart. General problem formulation (original configuration) 42

Figure 15. Graph. Eigenfunctions of the network equivalent to Fred Hartman Bridge: Mode 1 43

Figure 16. Graph. Eigenfunctions of the network equivalent to Fred Hartman Bridge: Mode 5 43

Figure 17. Graph. Comparative analysis of network vibration characteristics and individual cable behavior: Fred Hartman Bridge 44

Figure 18. Chart. Fred Hartman Bridge, field performance testing arrangement 45

Figure 19. Drawing. Types of cable surface treatments 47

Figure 20. Graph. Example of test data for spiral bead cable surface treatment 48

Figure 21. Photo. Leonard P. Zakim Bunker Hill Bridge 48

Figure 22. Graph. Sample decay: No damping and no crossties 50

Figure 23. Graph. Sample decay: With damping and no crossties 50

Figure 24. Graph. Sample decay: With damping and crossties 51

Figure 25. Photo. Sunshine Skyway Bridge 51

Figure 26. Photo. Stay and damper brace configuration 52

Figure 27. Photo. Reference database search page 72

Figure 28. Photo. Reference database search results page 73

Figure 29. Photo. U.S. cable-stayed bridge database: Switchboard 92

Figure 30. Photo. U.S. cable-stayed bridge database: General bridge information 93

Figure 31. Photo. U.S. cable-stayed bridge database: Cable data 94

Figure 32. Photo. U.S. cable-stayed bridge database: Wind data 95

Figure 33. Graph. Galloping of inclined cables 101

Figure 34. Drawing. Aerodynamic devices 103

Figure 35. Drawing. Cable crossties 107

Figure 36. Drawing. Viscous damping 107

Figure 37. Drawing. Material damping 108

Figure 38. Drawing. Angle relationships between stay cables and natural wind (after Irwin et al.) 112

Figure 39. Photo. Cable supporting rig: Top 114

Figure 40. Photo. Cable supporting rig: Bottom 114

Figure 41. Drawing. Longitudinal section of the propulsion wind tunnel 116

Figure 42. Drawing. Cross section of the working section of propulsion wind tunnel 117

Figure 43. Photo. Data acquisition system 118

Figure 44. Photo. Airpot damper 120

Figure 45. Drawing. Cross section of airpot damper 121

Figure 46. Photo. Elastic bands on the spring coils 122

Figure 47. Drawing. Side view of setups 1B and 1C 124

Figure 48. Drawing. Side view of setups 2A and 2C 125

Figure 49. Drawing. Side view of setups 3A and 3C 126

Figure 50. Photo. Cable setup in wind tunnel for testing 127

Figure 51. Graph. Amplitude-dependent damping (A, sway; B, vertical) with setup 2C (smooth surface, low damping) 134

Figure 52. Graph. Divergent response of inclined dry cable (setup 2C; smooth surface, low damping) 135

Figure 53. Graph. Lower end X-motion, time history of setup 2C at U = 32 m/s (105 ft/s) 135

Figure 54. Graph. Top end X-motion, time history of setup 2C at U = 32 m/s (105 ft/s) 136

Figure 55. Graph. Lower end Y-motion, time history of setup 2C at U = 32 m/s (105 ft/s) 136

Figure 56. Graph. Top end Y-motion, time history of setup 2C at U = 32 m/s (105 ft/s) 137

Figure 57. Graph. Trajectory of setup 2C at U = 32 m/s (105 ft/s) 137

Figure 58. Graph. Lower end X-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in the first 5 minutes 138

Figure 59. Graph. Top end X-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in the first 5 minutes 138

Figure 60. Graph. Lower end Y-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in the first 5 minutes 139

Figure 61. Graph. Top end Y-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in the first 5 minutes 139

Figure 62. Graph. Lower end X-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in second 5 minutes 140

Figure 63. Graph. Top end X-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in second 5 minutes 140

Figure 64. Graph. Lower end Y-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in second 5 minutes 141

Figure 65. Graph. Top end Y-motion, time history of setup 2A at U = 18 m/s (59 ft/s) in second 5 minutes 141

Figure 66. Graph. Lower end X-motion, time history of setup 2A at U = 19 m/s (62 ft/s) 142

Figure 67. Graph. Top end X-motion, time history of setup 2A at U = 19 m/s (62 ft/s) 142

Figure 68. Graph. Lower end Y-motion, time history of setup 2A at U = 19 m/s (62 ft/s) 143

Figure 69. Graph. Top end Y-motion, time history of setup 2A at U = 19 m/s (62 ft/s) 143

Figure 70. Graph. Lower end X-motion, time history of setup 1B at U = 24 m/s (79 ft/s) 144

Figure 71. Graph. Top end X-motion, time history of setup 1B at U = 24 m/s (79 ft/s) 144

Figure 72. Graph. Lower end Y-motion, time history of setup 1B at U = 24 m/s (79 ft/s) 145

Figure 73. Graph. Top end Y-motion, time history of setup 1B at U = 24 m/s (79 ft/s) 145

Figure 74. Graphic. Lower end X-motion, time history of setup 1C at U = 36 m/s (118 ft/s) 146

Figure 75. Graph. Top end X-motion, time history of setup 1C at U = 36 m/s (118 ft/s) 146

Figure 76. Graph. Lower end Y-motion, time history of setup 1C at U = 36 m/s (118 ft/s) 147

Figure 77. Graph. Top end Y-motion, time history of setup 1C at U = 36 m/s (118 ft/s) 147

Figure 78. Graph. Lower end X-motion, time history of setup 3A at U = 22 m/s (72 ft/s) 148

Figure 79. Graph. Top end X-motion, time history of setup 3A at U = 22 m/s (72 ft/s) 148

Figure 80. Graph. Lower end Y-motion, time history of setup 3A at U = 22 m/s (72 ft/s) 149

Figure 81. Graph. Top end Y-motion, time history of setup 3A at U = 22 m/s (72 ft/s) 149

Figure 82. Graph. Trajectory of setup 2A at U = 18 m/s (59 ft/s), first 5 minutes 150

Figure 83. Graph. Trajectory of setup 2A at U = 18 m/s (59 ft/s), second 5 minutes 150

Figure 84. Graphic. Trajectory of setup 2A at U = 19 m/s (62 ft/s) 151

Figure 85. Graphic. Trajectory of setup 1B at U = 24 m/s (79 ft/s) 151

Figure 86. Graphic. Trajectory of setup 1C at U = 36 m/s (119 ft/s) 152

Figure 87. Graph. Trajectory of setup 3A at U = 22 m/s (72 ft/s) 152

Figure 88. Graph. Wind-induced response of inclined dry cable (setup 2A; smooth surface, low damping) 153

Figure 89. Graph. Wind-induced response of inclined dry cable (setup 1B; smooth surface, low damping) 153

Figure 90. Graph. Wind-induced response of inclined dry cable (setup 1C; smooth surface, low damping) 154

Figure 91. Graph. Wind-induced response of inclined dry cable (setup 3A; smooth surface, low damping) 154

Figure 92. Graph. Wind-induced response of inclined dry cable (setup 3B; smooth surface, low damp 155

Figure 93. Graph. Critical Reynolds number of circular cylinder (from Scruton) 155

Figure 94. Graph. Damping trace of four different levels of damping (setup 1B; smooth surface) 156

Figure 95. Graph. Effect of structural damping on the wind response of inclined cable (setup 1B; smooth surface) 156

Figure 96. Graph. Surface roughness effect on wind-induced response of dry inclined cable (setup 3A; low damping) 157

Figure 97. Graph. Surface roughness effect on wind-induced response of dry inclined cable (setup 1B; low damping) 157

Figure 98. Graph. Surface roughness effect on wind-induced response of dry inclined cable (setup 2A; low damping) 158

Figure 99. Graph. Amplitude-dependent damping in the X-direction with setup 2A (frequency ratio effect) 158

Figure 100. Graph. Amplitude-dependent damping in the Y-direction with setup 2A 159

Figure 101. Graph. Wind-induced response of inclined cable in the X-direction with setup 2A (frequency ratio effect) 159

Figure 102. Graph. Wind-induced response of inclined cable in the Y-direction with setup 2A (frequency ratio effect) 160

Figure 103. Graph. Comparison of wind velocity-damping relation of inclined dry cable 160

Figure 104. Chart. Taut cable with a linear damper 165

Figure 105. Graph. Normalized damping ratio versus normalized damper coefficient 167

Figure 106. Chart. Cable with attached friction/viscous damper 169

Figure 107. Chart. Force-velocity curve for friction/viscous damper 169

Figure 108. Graph. Normalized damping ratio versus clamping ratio 171

Figure 109. Graph. Normalized viscous damper coefficient versus clamping ratio 171

Figure 110. Graph. Relationship between nondimensional parameters μ and κ with different values of the clamping ratio Θci for a friction/viscous damper 173

Figure 111. Graphic. Normalized damping ratio versus κ with varying μ 174

Figure 112. Graph. Normalized damping ratio versus normalized damper coefficient (β = 0.5) 176

Figure 113. Graph. Normalized damping ratio versus mode ratio (β = 1) 178

Figure 114. Graph. Normalized damping ratio versus amplitude ratio (β = 0.5) 178

Figure 115. Graph. Normalized damping ratio versus mode-amplitude ratio (β = 0) 178

Figure 116. Chart. General problem formulation 181

Figure 117. Chart. General problem formulation (original configuration) 184

Figure 118. Graph. Eigenfunctions of the network equivalent to Fred Hartman Bridge (1st-8th modes) 186

Figure 119. Graph. Comparative analysis of network vibration characteristics and individual cable behavior (Fred Hartman Bridge; NET_3C, original configuration; NET_3RC, infinitely rigid restrainers; NET_3CG, spring connectors extended to ground (restrainers 2,3)) 187

Figure 120. Chart. Generalized cable network configuration 190

Figure 121. Chart. Twin cable with variable position connector 191

Figure 122. Graph. Twin cable system, with connector location ξ = 0.35, example of frequency solution for linear spring model 193

Figure 123. Graph. Typical solution curves of the complex frequency for the dashpot 193

Figure 124. Chart. Intermediate segments of specific cables only 193

Figure 125. Chart. Fred Hartman Bridge (A-line) 3D network 194

Figure 126. Chart. Equivalent model 194

Figure 127. Graph. Frequency solutions (1st mode) for the damped cable network (A-line) 196

Figure 128. Graph. Complex modal form (1st mode) for the optimized system M1(uo) 196

Figure 129. Graphic. Damping versus mode number for Hartman stays A16 and A23 198

Figure 130. Graph. Stay vibration and damper force characteristics; stay A16 201

Figure 131. Graph. Stay vibration and damper force characteristics; stay A23 202

Figure 132. Chart. In-plane versus lateral RMS displacement for (A) AS16 and (B) AS23 206

Figure 133. Chart. Sample Lissajous plots of displacement for two records from AS16 207

Figure 134. Chart. Power spectral density of displacement of two records from AS16 208

Figure 135. Graph. Sample Lissajous plots of displacement for two records from AS23 209

Figure 136. Graph. Power spectral density of displacement of two records from AS23 209

Figure 137. Graph. In-plane versus lateral RMS displacement for (A) AS16 and (B) AS23 after damper installation 210

Figure 138. Graph. Lissajous and power spectral density plots of displacement for record A 211

Figure 139. Graph. Modal frequencies of stays (A) AS16 and (B) AS23 212

Figure 140. Graph. Second-mode frequency versus RMS displacement for stay AS16 213

Figure 141. Graph. Estimated modal damping of stay AS16 showing effect of damper 214

Figure 142. Graphic. Histogram of estimated damping for (A) mode 2 of AS16 and (B) mode 3 of AS23 214

Figure 143. Graphic. Dependence of modal damping on damper force 215

Figure 144. Graph. RMS damper force versus RMS displacements for (A) AS16 and (B) AS23 216

Figure 145. Chart. Damper force versus displacement and velocity for a segment of a sample record 217

Figure 146. Chart. Displacement and damper force time histories of a sample record 218

Figure 147. Drawing. Incline stay cable properties 220

Figure 148. Drawing. Definition diagram for a horizontal cable (taut string), compared to the definition diagram for an inclined cable 225

Figure 149. Graph. Cable √T/m versus cable unstressed length: Summary of Alex Fraser, Maysville, and Owensboro bridges 229

Figure 150. Graph. Cable frequency versus cable unstressed length: Summary of Alex Fraser, Maysville, and Owensboro bridges 230

Figure 151. Photo. RAMA 8 Bridge (artistic rendering) 231

Figure 152. Drawing. RAMA 8 Bridge computer model: XY, YZ, and ZX views 232

Figure 153. Chart. Independent cable M26 discretization 10-segment model: XZ view 234

Figure 154. Chart. Cable catenary 235

Figure 155. Chart. Cable modes: XZ, YZ, and XY views (as defined in figure 152) 236

Figure 156. Chart. Inextensible cable mode 1, in-plane: XY, YX, and XZ views 238

Figure 157. Drawing. Cable M26 discretization: 10-segment model, isometric view. Only cables M26 are shown. Other cables not shown for clarity 239

Figure 158. Drawing. Cable M26 discretization: 10-segment model, XZ view. Other cables not shown for clarity 239

Figure 159. Chart. Fundamental bridge modes 241

Figure 160. Chart. Additional bridge modes 242

Figure 161. Chart. Four first modes of the cables; XY, YZ, and XZ views 243

Figure 162. Chart. Four second modes of the cables; XY, YZ, and XZ views 243

Figure 163. Chart. Four third modes of the cables; XY, YZ, and XZ views 244

Figure 164. Chart. Nodes, members, and cables for comparison of results 245

Figure 165. Graph. RAMA 8 Bridge model damping versus frequency 250

Figure 166. Graph. Vertical displacements, velocities, and accelerations of node 427 versus time (train speed = 80 km/h (50 mi/h) 251

Figure 167. Graph. Member 1211: Bending moment versus time (train speed = 80 km/h (50 mi/h)) 252

Figure 168. Graph. Cable M26: Tension versus time (train speed = 80 km/h (50 mi/h)) 252

Figure 169. Graph. Difference in cable tension for cable M26 between the dynamic train load case and static train load case versus time (train speed = 80 km/h (50 mi/h)) 253

Figure 170. Graph. Cable M26 tension spectra (train speed = 80 km/h (50 mi/h)) 254

Figure 171. Graph. Global coordinate displacements (A, B, C) of cable M26 nodes (mm) versus time (train speed = 80 km/h (50 mi/h)) 256

Figure 172. Chart. Transformation from global coordinates to coordinates along the cable 257

Figure 173. Chart. Local coordinate displacements of nodes of cable M26 (mm). Displacements are shown for three nodes of the cable: At 1/4 span (closer to the tower), 1/2 span, and 3/4 span (closer to the deck; train speed = 80 km/h (50 mi/h) 258

Figure 174. Graph. Spectra for movements of cable M26 nodes: At 1/4 span (closer to the tower), 1/2 span, and 3/4 span (closer to the deck; frequency range = 0-2 Hz; train speed = 80 km/h (50 mi/h)) 259

Figure 175. Graph. Deck rotations and cable end rotations for cable M26: Dynamic (train speed = 80 km/h (50 mi/h)) and static 261

Figure 176. Graph. Deck rotations and cable end rotations for cable M21: dynamic (train speed = 80 km/h (50 mi/h)) and static 261

Figure 177. Graph. Effect of mode (constant amplitude and velocity) 264

Figure 178. Graph. Effect of velocity (constant amplitude) 264

Figure 179. Graph. Effect of amplitude (constant velocity) 265