ABSTRACT Title of Dissertation: AN EXPERIMENTAL INVESTIGATION OF THE FLEXURAL RESISTANCE OF HORIZONTALLY CURVED STEEL I- GIRDER SYSTEMS Joseph Lawrence Hartmann, Doctor of Philosophy, 2005 Dissertation Directed By: Professor Emeritus Pedro Albrecht and Affiliated Associate Professor Chung Fu, Department of Civil and Environmental Engineering In 1998 the Federal Highway Administration (FHWA) began executing the experimental component of a multi-year program investigating horizontally curved steel I-girder bridges. This experimental program consists of full-scale testing to determine the effects of horizontal curvature on the structural performance of I- girders subject to moment and shear, to investigate moment/shear interaction, and to assess the behavior and ultimate capacity of a composite bridge. The experiments that are the focus of this dissertation are the component tests designed to determine the bending strength of horizontally curved steel I-girders. These tests were conducted at full-scale using a 3-girder system in order to eliminate concerns with modeling and scaling of the results. Also, the boundary conditions supplied to the components by the full-scale 3-girder system are considered to be comparable if not equal to those produced on real bridges. The seven bending component tests were designed to examine the influence of compression flange slenderness, web slenderness and transverse stiffener spacing on bending capacity. The components were loaded within a constant moment region of the test frame eliminating applied vertical shear loads from affecting their performance. For each test, an attempt was made to capture the strains due to installation of the component into the test frame and the strain due to dead-load deflection, as well as the strains due to the applied loading. AN EXPERIMENTAL INVESTIGATION OF THE FLEXURAL RESISTANCE OF HORIZONTALLY CURVED STEEL I-GIRDER SYSTEMS By Joseph Lawrence Hartmann Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2005 Advisory Committee: Professor Emeritus Pedro Albrecht, Chair Affiliated Associate Professor Chung Fu, Co-Chair Professor Amde Amde Professor Amr Baz, Dean?s Representative Professor Emeritus Bruce Donaldson ? Copyright by Joseph Lawrence Hartmann 2005 Preface This report is one of several that will include data and analyses specific to the Curved Steel Bridge Research Project conducted at the Federal Highway Administration?s Turner-Fairbank Highway Research Structures Laboratory. This multi-year project investigated the effects of horizontal curvature on steel I-girder systems during erection, subject to uniform moment, subject to moment-shear interaction, and in composite construction. This report is specific to the experimental results of the investigation on uniform moment. The Curved Steel Bridge Research Project was a pooled-fund effort. In addition to the Federal Highway Administration, the following state Departments of Transportation contributed funding to this project: Alabama, Arkansas, California, Florida, Georgia, Iowa, Illinois, Kansas, Kentucky, Louisiana, Minnesota, Missouri, Nebraska, Nevada, New Hampshire, New Jersey, New York, North Carolina, Oklahoma, Tennessee, Texas, Utah, Virginia, Wisconsin, and Wyoming. ii Dedication To my wife, Tracy, and daughters, Sara and Hannah. iii Acknowledgements The author wishes to gratefully acknowledge the contributions made to this report by his advisor, Professor Emeritus Pedro Albrecht, and co-advisor, Affiliated Associate Professor Chung Fu. In particular, the author would like to thank Dr. Albrecht for the steadfast support and encouragement he has provided during 15 years of graduate school advisement. The author would also like to recognize the direct and indirect contributions made to this report by Dr. William Wright (Federal Highway Administration), Professor Donald White (Georgia Institute of Technology), and Mr. Michael Grubb (BSDI Ltd.). The author is pleased to be able to refer to these gentlemen as mentors, colleagues and friends. Finally, the author wishes to thank his colleagues at the Turner-Fairbank Highway Research Center Structures Laboratory who were a part of the Curved Steel Bridge Research Project for their contributions to this report; Mr. Zuhan Xi, Dr. Hernando Chandra and Dr. Fassil Beshah. Without their professionalism and participation, these experiments and this report would not have been a success. iv Table of Contents Preface ii Dedication iii Acknowledgements iv Table of Contents v List of Tables viii List of Figures xi List of Abbreviations xvi Chapter 1. Introduction 1 1.1 Background/Problem 1 1.2 Objective and Scope 6 1.3 Previous Experimental Work 6 1.3.1 CURT Tests 7 1.3.2 University of Maryland Tests 12 1.3.3 Japanese Tests 14 1.3.4 Other Experimental Testing 16 1.4 Strength Predictor Equations 17 Chapter 2. Experiment Design 19 2.1 Test Frame Concept 20 2.2 Component Test Matrix 27 2.2.1 Bending Component Series 27 2.2.2 Moment-Shear Interaction Component Series 30 2.3 Fabrication of the Test Frame and Bending Components 30 2.3.1 Materials 30 2.3.1.1 Girders 31 2.3.1.2 Cross-Frames and Diaphragms 31 2.3.1.3 Bending Components 32 2.3.2 As-Built Geometry 32 2.4 Material Properties 33 2.4.1 Plate Coupon Locations 34 2.4.2 Tensile Strength Testing 34 2.4.3 Compressive Strength Testing 35 2.4.4 Elastic Modulus Testing 35 2.5 Instrumentation Plan 36 2.5.1 Test Frame Instrumentation 36 2.5.2 Bending Component Instrumentation 47 2.6 Laboratory Equipment 48 2.6.1 Loading Apparatus 48 2.6.2 Instrumentation 51 2.6.2.1 Electrical Resistance Strain Gages 51 2.6.2.2 Vibrating Wire Strain Gages 52 2.6.2.3 Load Cells 52 2.6.3 Data Acquisition Systems 53 2.6.3.1 MicroMeasurements 4000 53 v 2.6.3.2 MicroMeasurements 5000 53 2.6.3.3 Geokon Micro-10 53 2.6.3.4 Hewlett-Packard VXI 54 Chapter 3. Analysis of Experimental Data 55 3.1 Execution of the Experiments 55 3.2 Data Analysis 58 3.3 Installation Strains 66 3.4 Bending Component B1 Test 77 3.5 Bending Component B2 Test 91 3.6 Bending Component B3 Test 103 3.7 Bending Component B4 Test 120 3.8 Bending Component B5 Test 132 3.9 Bending Component B6 Test 143 3.10 Bending Component B7 Test 156 3.11 Boundary Conditions 167 3.12 Effect of Installation Strains on Capacity 168 3.13 Effect of Compression Flange Slenderness on Capacity 169 3.14 Effect of Web Slenderness on Capacity 172 3.15 Effect of Transverse Stiffener Spacing on Capacity 172 Chapter 4. Analytical Results 173 4.1 Finite Element Model 173 4.1.1 Stress-Strain Relationship 176 4.1.2 As-Built Geometry 183 4.1.3 Installation Strains 184 4.1.4 Modeling of Residual Stress 185 4.1.5 Modeling of Boundary Conditions 191 4.1.6 Predictions 191 4.1.6.1 B1 Finite Element Model Results 193 4.1.6.2 B2 Finite Element Model Results 195 4.1.6.3 B3 Finite Element Model Results 198 4.1.6.4 B4 Finite Element Model Results 200 4.1.6.5 B5 Finite Element Model Results 202 4.1.6.6 B6 Finite Element Model Results 205 4.1.6.7 B7 Finite Element Model Results 208 4.2 AASHTO Guide Specifications Predictions 211 4.2.1 Non-Compact Compression Flange Example 212 4.2.2 Compact Compression Flange Example 216 4.3 Unified Design Method Predictions 219 4.3.1 Non-Compact Compression Flange Example 220 4.3.2 Compact Compression Flange Example 224 4.4 Summary of Predictions 228 Chapter 5. Conclusions 230 5.1 Summary 230 5.2 Findings 231 5.3 Research Needs 233 Appendix A. Steel Properties Data 235 vi A.1 Plate Coupon Locations 235 A.2 Tension Testing 253 A.2.1 Yield Strength Results 292 A.2.1.1 Offset Yield Strength 292 A.2.1.2 Upper Yield Strength 295 A.2.1.3 Lower Yield Strength 297 A.2.1.4 Static Yield Strength 298 A.2.2 Yield Point Elongation Results 298 A.2.3 Tensile Strength Results 299 A.3 Compression Testing 299 A.3.1 Yield Strength Results 301 A.3.1.1 Offset Yield Strength 301 A.3.1.2 Upper Yield Strength 301 A.3.1.3 Lower Yield Strength 301 A.3.1.4 Static Yield Strength 302 A.3.2 Yield Point Elongation Results 302 A.4 Young?s Modulus Testing 302 A.4.1 Young?s Modulus Testing Results 304 A.4.2 Young?s Modulus From Tension Testing 304 A.4.3 Young?s Modulus From Compression Testing 305 A.5 True Stress-Strain 305 A.5.1 True Strain 306 A.5.2 True Stress 306 Appendix B. Design Equations 308 B.1 Summary of the Guide Specifications Provisions for the Design of Non-Composite I-Girders in Flexure 308 B.1.1 I-Girder Flanges 308 B.1.1.1 Partially Braced Compression Flanges 309 B.1.1.2 Partially Braced Tension Flanges 311 B.1.2 I-Girder Webs 311 B.1.2.1 Unstiffened Webs 311 B.1.2.2 Transversely Stiffened Webs 312 B.1.2.3 Transversely and Longitudinally Stiffened Webs 313 B.2 Summary of the Unified Design Method Equations for the Design of Non-Composite I-Girders in Flexure 313 B.2.1 Discretely Braced Compression Flanges 314 B.2.1.1 Flange Local Buckling 314 B.2.1.2 Lateral Torsional Buckling 315 B.2.2 Discretely Braced Tension Flanges 316 Refrences 317 vii List of Tables Table 1-1: Summary of Previous Experimental Work That Produced Flexural or Flexural/Shear Failures 8 Table 2-1: CSBRP Bending Specimen Target Parameter Test Matrix 29 Table 2-2: CSBRP Bending Specimen As-Built Parameter Test Matrix 33 Table 2-3: Configuration and Location of Strain Gaged Sections 37 Table 3-1: Installation Strain Data Analysis Results for Specimens B4, B5, B6 and B7 68 Table 3-2: Installation Strain Data Used in Bending Component Capacity Analysi 74 Table 3-3: B1 Applied Load Steps and Resulting Girder Moments 80 Table 3-4: B1 Mid-Span Stresses and Moments 81 Table 3-5: B2 Applied Load Steps and Resulting Girder Moments 93 Table 3-6: B2 Mid-Span Stresses and Moments 94 Table 3-7: B3 Applied Load Steps and Resulting Girder Moments (Part I) 104 Table 3-8: B3 Applied Load Steps and Resulting Girder Moments (Part II) 105 Table 3-9: B3 Mid-Span Stresses and Moments 106 Table 3-10: B4 Applied Load Steps and Resulting Girder Moments 121 Table 3-11: B4 Mid-Span Stresses and Moments 123 Table 3-12: B5 Applied Load Steps and Resulting Girder Moments (Part I) 133 Table 3-13: B5 Applied Load Steps and Resulting Girder Moments (Part II) 134 Table 3-14: B5 Mid-Span Stresses and Moments 135 Table 3-15: B6 Applied Load Steps and Resulting Girder Moments (Part I) 144 Table 3-16: B6 Applied Load Steps and Resulting Girder Moments (Part II) 145 Table 3-17: B6 Mid-Span Stresses and Moments 147 Table 3-18: B7 Applied Load Steps and Resulting Girder Moments 157 Table 3-19: B7 Mid-Span Stresses and Moments 160 Table 3-20: Summary of Experimental Results 169 Table 4-1: Cross-reference of Steel Plate Number and Bending Component Element 176 Table 4-2: Average Steel Plate Properties for Selected Steel Plates 177 Table 4-1: Equations Used to Establish Typical Stress-Strain Relationships for the FE Model 178 Table 4-2: Bending Specimen As-Built Plate Dimensions 184 Table 4-3: Compression Flange Plate Residual Stresses 188 Table 4-4: Web Plate Residual Streses 188 Table 4-5: Tension Flange Plate Residual Stresses 189 Table 4-6: B1 Test and Finite Element Model Results 193 Table 4-7: B2 Test and Finite Element Model Results 196 Table 4-8: B3 Test and Finite Element Model Results 198 Table 4-9: B4 Test and Finite Element Model Results 201 Table 4-10: B5 Test and Finite Element Model Results 203 Table 4-11: B6 Test and Finite Element Model Results 206 Table 4-12: B7 Test and Finite Element Model Results 208 viii Table 4-13: Summary of Guide Specifications Flexural Capacities and Staistcs 212 Table 4-14: Summary of Unified Design Method Flexural Capacities and Staistcs 220 Table 4-15: Summary of Predicted Vertical Bending Moments 229 Table A-1: Summary of Plate 1 Tension Test Results 255 Table A-2: Summary of Plate 2 Tension Test Results 256 Table A-3: Summary of Plate 3 Tension Test Results 257 Table A-4: Summary of Plate 4 Tension Test Results 258 Table A-5: Summary of Plate 5 Tension Test Results 259 Table A-6: Summary of Plate 6 Tension Test Results 260 Table A-7: Summary of Plate 7 Tension Test Results 261 Table A-8: Summary of Plate 8 Tension Test Results 262 Table A-9: Summary of Plate 9 Tension Test Results 263 Table A-10: Summary of Plate 10 Tension Test Results 264 Table A-11: Summary of Plate 11 Tension Test Results 265 Table A-12: Summary of Plate 12 Tension Test Results 266 Table A-13: Summary of Plate 13 Tension Test Results 267 Table A-14: Summary of Plate 14 Tension Test Results 268 Table A-15: Summary of Plate 15 Tension Test Results 269 Table A-16: Summary of Plate 16 Tension Test Results 270 Table A-17: Summary of Plate 18 Tension Test Results 271 Table A-18: Summary of Plate 19 Tension Test Results 272 Table A-19: Summary of Plate 20 Tension Test Results 273 Table A-20: Summary of Plate 21 Tension and Compression Test Results 274 Table A-21: Summary of Plate 22 Tension and Compression Test Results 275 Table A-22: Summary of Plate 23 Tension and Compression Test Results 276 Table A-23: Summary of Plate 24 Tension and Compression Test Results 277 Table A-24: Summary of Plate 25 Tension and Compression Test Results 278 Table A-25: Summary of Plate 26 Tension Test Results 279 Table A-26: Summary of Plate 27 Tension Test Results 280 Table A-27: Summary of Plate 28 Tension Test Results 281 Table A-28: Summary of Plate 29 Tension Test Results 282 Table A-29: Summary of Plate 30 Tension and Compression Test Results 283 Table A-30: Summary of Plate 31 Tension and Compression Test Results 284 Table A-31: Summary of Plate 32 Tension Test Results 285 Table A-32: Summary of Plate 33 Tension Test Results 286 Table A-33: Summary of Plate 34 Tension Test Results 287 Table A-34: Summary of Plate 35 Tension Test Results 288 Table A-35: Summary of Structural Steel Tube 674 Tension Test Results 289 Table A-36: Summary of Structural Steel Tube 811 Tension Test Results 290 Table A-37: Summary of Structural Steel Tube 871 Tension Test Results 291 Table A-38: A572 Steel Tension Testing Statistics 293 Table A-39: A852 Steel Tension Testing Statistics 294 Table A-40: A572 Steel Compression Testing Statistics 300 Table A-41: Young?s Modulus Testing Statistics 303 ix Table A-42: Young?s Modulus Statistics from Tension and Compression Testing 304 x List of Figures Figure 1-1: All Previous Experimental Slenderness Combinations 4 Figure 1-2: Slenderness Combinations From All Previous Uniform Bending Experiments 5 Figure 1-3: All Previous Uniform Bending Experiments with Realistic Boundary Conditions 5 Figure 2-1: Plan View of Test Frame 22 Figure 2-2: Cross-Section of Test Frame at a Cross Frame Location 6L 23 Figure 2-3: The Test Frame in the FHWA Structures Laboratory 24 Figure 2-4: Bending Component Test Matrix 26 Figure 2-5: Location of Instrumented Cross-Sections 38 Figure 2-6: Instrumentation Configuration (1) 39 Figure 2-7: Instrumentation Configuration (2) 40 Figure 2-8: Instrumentation Configuration (3) 41 Figure 2-9: Instrumentation Configuration (V1) 42 Figure 2-10: Instrumentation Configuration (V2) 43 Figure 2-11: Instrumentation Configuration (V3) 44 Figure 2-12: Instrumentation Configuration (V5) 45 Figure 2-13: Instrumentation Configuration (V6) 46 Figure 2-14: Typical Load Frame 49 Figure 3-1: No-Load Condition Support Layout 56 Figure 3-2: I-Girder Coordinate System 60 Figure 3-3: Identification of Strain Measurement and Resultant Locations 61 Figure 3-4: Cross-Sectional Parameters 62 Figure 3-5: Components of Longitudinal Strain 65 Figure 3-6: B4 Installation Strain Data 70 Figure 3-7: B5 Installation Strain Data 71 Figure 3-8: B6 Installation Strain Data 72 Figure 3-9: B7 Installation Strain Data 73 Figure 3-10: B1 Installation Strain Data with Regression Line Estimates 75 Figure 3-11: B2 Installation Strain Model From Regression Line Estimates 76 Figure 3-12: B3 Installation Strain Data With Regression Line Estimates 77 Figure 3-13: B1 Vertical Bending Moment 82 Figure 3-14: Test Frame Mid-Span Vertical Bending Moments, B1 Test 82 Figure 3-15: B1 Mid-Span Longitudinal Strain State Resulting From Installations and Dead Load (Step 1) 84 Figure 3-16: B1 Mid-Span Longitudinal Strain State During Step 8 85 Figure 3-17: Longitudinal Strain State in B1 Near Cross-Frame N6L During Step 8 (Excluding Installation Effects) 86 Figure 3-18: B1 Mid-Span Longitudinal Strain State During Step 11 87 Figure 3-19: B1 Mid-Span Longitudinal Strain State During Step 18 88 Figure 3-20: B1 Mid-Span Longitudinal Strain State During Step 28 89 Figure 3-21: Most Critical G2 Mid-Span Longitudinal Strain State B1 Test (Step 29) 90 xi Figure 3-22: B2 Vertical Bending Moment in Elastic Range 95 Figure 3-23: Test Frame Mid-Span Vertical Bending Moments, B2 Test 95 Figure 3-24: B2 Mid-Span Longitudinal Strain State Resulting From Installation and Dead Load (Step 1) 96 Figure 3-25: B2 Mid-Span Longitudinal Strain State During Step 10 97 Figure 3-26: Longitudinal Strain State in B2 Near Cross-Frame N6L During Step 10 (Excluding Installation Effects) 98 Figure 3-27: B2 Mid-Span Longitudinal Strain State During Step 13 99 Figure 3-28: Longitudinal Strain State in B2 Near Cross-Frame N6L During Step 22 (Excluding Installation Effects) 100 Figure 3-29: Longitudinal Strain State in B2 Near Cross-Frame N6R During Step 22 (Excluding Installation Effects) 101 Figure 3-30: B2 Mid-Span Longitudinal Strain State During Step 33 102 Figure 3-31: Most Critical G2 Mid-Span Longitudinal Strain State During B2 Test (Step 36) 103 Figure 3-32: B3 Vertical Bending Moment 107 Figure 3-33: Test Frame Mid-Span Vertical Bending Moments, B3 Test 108 Figure 3-34: B3 Mid-Span Longitudinal Strain State Resulting From Installation and Dead Load (Step 1) 109 Figure 3-35: B3 Mid-Span Longitudinal Strain State During Step 10 110 Figure 3-36: Longitudinal Strain State in B3 Near Cross-Frame N6L During Step 10 (Excluding Installation Effects) 111 Figure 3-37: Longitudinal Strain State in B3 Near Cross-Frame N6R During Step 10 (Excluding Installation Effects) 112 Figure 3-38: B3 Mid-Span Longitudinal Strain State During Step 14 113 Figure 3-39: Longitudinal Strain State in B3 Near Cross-Frame N6L During Step 21 (Excluding Installation Effects) 114 Figure 3-40: Longitudinal Strain State in B3 Near Cross-Frame N6R During Step 21 (Excluding Installation Effects) 115 Figure 3-41: Longitudinal Strain State in B3 Near Cross-Frame N6R During Step 22 (Excluding Installation Effects) 116 Figure 3-42: Longitudinal Strain State in B3 Near Cross-Frame N6L During Step 23 (Excluding Installation Effects) 117 Figure 3-43: B3 Mid-Span Longitudinal Strain State During Step 31 118 Figure 3-44: B3 Mid-Span Longitudinal Strain State During Step 44 119 Figure 3-45: Most Critical G2 Mid-Span Longitudinal Strain State During B3 Test 120 Figure 3-46: B4 Vertical Bending Moment 122 Figure 3-47: Test Frame Mid-Span Vertical Bending Moments, B4 Test 124 Figure 3-48: B4 Mid-Span Longitudinal Strain State Resulting From Installation and Dead Load (Step 1) 125 Figure 3-49: B4 Mid-Span Longitudinal Strain State During Step 8 126 Figure 3-50: Longitudinal Strain State in B4 Near Cross-Frame N6L During Step 8 (Excluding Installation Effects) 127 Figure 3-51: Longitudinal Strain State in B4 Near Cross-Frame N6R During Step 8 (Excluding Installation Effects) 128 xii Figure 3-52: Longitudinal Strain State in B4 Near Cross-Frame N6R During Step 18 (Excluding Installation Effects) 129 Figure 3-53: Longitudinal Strain State in B4 Near Cross-Frame N6L During Step 19 (Excluding Installation Effects) 130 Figure 3-54: B4 Mid-Span Longitudinal Strain State During Step 29 131 Figure 3-55: Most Critical G2 Mid-Span Longitudinal Strain State During B4 Test 132 Figure 3-56: B5 Vertical Bending Moment 136 Figure 3-57: Test Frame Mid-Span Vertical Bending Moments, B5 Test 137 Figure 3-58: B5 Mid-Span Longitudinal Strain State Resulting From Installation and Dead Load (Step 1) 138 Figure 3-59: B5 Mid-Span Longitudinal Strain State During Step 9 139 Figure 3-60: Longitudinal Strain State in B5 Near Cross-Frame N6L During Step 9 (Excluding Installation Effects) 140 Figure 3-61: Longitudinal Strain State in B5 Near Cross-Frame N6L During Step 16 (Excluding Installation Effects) 141 Figure 3-62: B5 Mid-Span Longitudinal Strain State During Step 38 142 Figure 3-63: Most Critical G2 Mid-Span Longitudinal Strain State During B5 Test 143 Figure 3-64: B6 Vertical Bending Moment 148 Figure 3-65: Test Frame Mid-Span Vertical Bending Moments, B6 Test 149 Figure 3-66: B6 Mid-Span Longitudinal Strain State Resulting From Installation and Dead Load (Step 1) 150 Figure 3-67: B6 Mid-Span Longitudinal Strain State During Step 13 151 Figure 3-68: Longitudinal Strain State in B6 Near Cross-Frame N6L During Step 13 (Excluding Installation Effects) 152 Figure 3-69: Longitudinal Strain State in B6 Near Cross-Frame N6R During Step 13 (Excluding Installation Effects) 153 Figure 3-70: B6 Mid-Span Longitudinal Strain State During Step 28 154 Figure 3-71: B6 Mid-Span Longitudinal Strain State During Step 38 155 Figure 3-72: Most Critical G2 Mid-Span Longitudinal Strain State During B6 Test 156 Figure 3-73: B7 Vertical Bending Moment 158 Figure 3-74: Test Frame Mid-Span Vertical Bending Moments, B7 Test 159 Figure 3-75: B7 Mid-Span Longitudinal Strain State Resulting From Installation and Dead Load (Step 1) 161 Figure 3-76: B7 Mid-Span Longitudinal Strain State During Step 8 162 Figure 3-77: Longitudinal Strain State in B7 Near Cross-Frame N6L During Step 8 (Excluding Installation Effects) 163 Figure 3-78: Longitudinal Strain State in B7 Near Cross-Frame N6R During Step 8 (Excluding Installation Effects) 164 Figure 3-79: B7 Mid-Span Longitudinal Strain State During Step 10 165 Figure 3-80: B7 Mid-Span Longitudinal Strain State During Step 13 166 Figure 3-81: Most Critical G2 Mid-Span Longitudinal Strain State During B7 Test 167 Figure 3-82: Effect of Compression Flange Slenderness 170 xiii Figure 3-83: Effect of Compression Flange Slenderness (w/o B7) 171 Figure 4-1: Typical Finite Element Model Used in this Study 174 Figure 4-2: Typical Bending Component Finite Element Mesh Density 175 Figure 4-3: Typical Engineering Stress-Strain Relationship Used by FE Model 178 Figure 4-4: Engineering Versus True Stress-Strain 181 Figure 4-5: Plate 21 Compression and Tension Test Results Compared with the FE Material Model in Engineering Stress-Strain 182 Figure 4-6: Plate 21 Compression and Tension Test Results Compared with the FE Material Model in True Stress-Strain 183 Figure 4-7: Example Flange Plate Residual Stress Profile 190 Figure 4-8: Example Web Plate Residual Stress Profile 190 Figure 4-9: B1 Test Mid-Span Moments and Finite Element Predictions 194 Figure 4-10: B1 Mid-Span Moment vs. Deflection 195 Figure 4-11: B2 Test Mid-Span Moments and Finite Element Predictions 196 Figure 4-12: B2 Mid-Span Moment vs. Deflection 197 Figure 4-13: B3 Test Mid-Span Moments and Finite Element Predictions 199 Figure 4-14: B3 Mid-Span Moment vs. Deflection 200 Figure 4-15: B4 Test Mid-Span Moments and Finite Element Predictions 201 Figure 4-16: B4 Mid-Span Moment vs. Deflection 202 Figure 4-17: B5 Test Mid-Span Moments and Finite Element Predictions 204 Figure 4-18: B5 Mid-Span Moment vs. Deflection 205 Figure 4-19: B6 Test Mid-Span Moments and Finite Element Predictions 206 Figure 4-40: B6 Mid-Span Moment vs. Deflection 207 Figure 4-41: B7 Test Mid-Span Moments and Finite Element Predictions 209 Figure 4-42: B7 Mid-Span Moment vs. Deflection 210 Figure A-1. Layout of Cutting Plates in Full Scale Test of Curve Girders Bridge (See Table 1 for Cutting Schedule) 237 Figure A-2. Location of Tensile Coupons on Plate: 1 238 Figure A-3. Location of Tensile Coupons on Plate: 2 238 Figure A-4. Location of Tensile Coupons on Plate: 3 239 Figure A-5. Location of Tensile Coupons on Plate: 4 239 Figure A-6. Location of Tensile Coupons on Plate: 5 240 Figure A-7. Location of Tensile Coupons on Plate: 6 240 Figure A-8. Location of Tensile Coupons on Plate: 7 241 Figure A-9. Location of Tensile Coupons on Plate: 8 241 Figure A-10. Location of Tensile Coupons on Plate: 9 242 Figure A-11. Location of Tensile Coupons on Plate: 10 242 Figure A-12. Location of Tensile Coupons on Plate: 11 243 Figure A-13. Location of Tensile Coupons on Plate: 12 243 Figure A-14. Location of Tensile Coupons on Plate: 13 244 Figure A-15. Location of Tensile Coupons on Plate: 14 244 Figure A-16. Location of Tensile Coupons on Plate: 15 244 Figure A-17. Location of Tensile Coupons on Plate: 16 245 Figure A-18. Location of Tensile Coupons on Plate: 17 245 Figure A-19. Location of Tensile Coupons on Plate: 18 245 xiv Figure A-20. Location of Tensile Coupons on Plate: 19 246 Figure A-21. Location of Tensile Coupons on Plate: 20 246 Figure A-22. Location of Tensile Coupons on Plate: 21 246 Figure A-23. Location of Tensile Coupons on Plate: 22 247 Figure A-24. Location of Tensile Coupons on Plate: 23 247 Figure A-25. Location of Tensile Coupons on Plate: 24 247 Figure A-26. Location of Tensile Coupons on Plate: 25 248 Figure A-27. Location of Tensile Coupons on Plate: 26 248 Figure A-28. Location of Tensile Coupons on Plate: 28 248 Figure A-29. Location of Tensile Coupons on Plate: 32 249 Figure A-30. Location of Tensile Coupons on Plate: 34 249 Figure A-31. Location of Tensile Coupons on Plate: 30 250 Figure A-32. Location of Tensile Coupons on Plate: 31 250 Figure A-33. Location of Tensile Coupons on Plate: 33 251 Figure A-34. Location of Tensile Coupons on Plate: 35 251 Figure A-35. Location of Tensile Coupons on Plate: 27 252 Figure A-36. Location of Tensile Coupons on Plate: 29 252 Figure A-37: Typical Tension Test Records 296 xv List of Abbreviations A = I-girder cross-sectional area AF = 1 st order lateral flange bending stress amplification factor Bi = bimoment C b = moment gradient correction factor C w = warping constant D = web depth D c = depth of web in compression in the elastic range E = modulus of elasticity of steel E st = strain hardening modulus F bs = critical average flange stress F cr = critical average flange stress or critical compressive longitudinal stress in the web for the Guide Specifications; critical buckling stress for the Unified Design Method F cr1 = critical average flange stress calculated from reduction factors F cr2 = critical average flange stress determined from partial yielding F n = nominal flexural resistance in terms of stress F nc = nominal flexural resistance of the compression flange in terms of stress F nc(FLB) = nominal flexural resistance of the compression flange based on flange local buckling in terms of stress F nc(LTB) = nominal flexural resistance of the compression flange based on lateral torsional buckling in terms of stress F nt = nominal flexural resistance of the tension flange in terms of stress F y = specified minimum yield strength of steel F yc = specified minimum yield strength of compression flange steel F yt = specified minimum yield strength of tension flange steel F yw = specified minimum yield strength of web plate steel I x = moment of inertia about the x-axis I y = moment of inertia about the y-axis L b = unbraced length L p = lateral bracing limit for flexural capacity governed by plastic bending L r = lateral bracing limit for flexural capacity governed by inelastic lateral torsional buckling M lat = lateral flange bending moment M n = nominal vertical bending moment M x = moment about x-axis M x yield = moment about x-axis that will cause yield in the compression flange M y = moment about y-axis P z = axial force in the z-direction R = girder radius; minimum girder radius within a panel or over a specified length R b = flange-stress reduction factor to account for load shedding from web buckling R h = flange-stress reduction factor to account for load shedding from hybrid web yielding xvi Sxc = section modulus with respect to the compression flange W n = normalized unit warping b = minimum flange width b f = flange width b fc = compression flange width b ft = tension flange width d o = actual distance between transverse stiffeners d s = distance between longitudinal stiffener and compression flange f b = calculated factored average flange stress at the section under consideration f bu = flexural flange stress due to primary bending from factored loads f l1 = 1 st order lateral flange bending stress f l = 2 nd order lateral flange bending stress or 1 st order lateral flange bending stress corrected with AF k = coefficient of web bend-buckling l = unbraced length r t = radius of gyration of the compression flange taken about the vertical axis t f = flange thickness t fc = thickness of the compression flange t s = transverse web stiffener thickness t t = thickness of the tension flange t w = web thickness x = normal distance to the x-axis y = normal distance to the y-axis y NA = distance from web mid-depth to neutral axis y SC = distance from neutral axis to shear center ? = longitudinal strain ? eng = engineering strain ? st = strain at the onset of strain hardening ? true = true strain ? u = strain at tensile strength ? f = compression flange slenderness parameter ? pf = limiting slenderness parameter for compact flange local buckling behavior ? rf = limiting slenderness parameter for non-compact flange local buckling behavior b ? = curvature factor for non-compact flange strength w ? = curvature factor for non-compact flange strength w1 ? = curvature factor for non-compact flange strength w2 ? = curvature factor for non-compact flange strength b ? = curvature factor for compact flange strength w ? = curvature factor for compact flange strength ? eng = engineering stress ? sy = static yield strength ? true = true stress ? u = tensile strength xvii ? z = stress in the z-direction ? 0.2% = offset yield strength ? f = resistance factor for flexure xviii Chapter 1. Introduction 1.1 Background/Problem Horizontally curved girder bridges represent approximately 30% of the steel bridge market in the United States today. The current market share is a significant increase from 25 years ago when these types of structures represented only a single digit percentage of the market. The increased use of this bridge type reflects the significant attention that is now given to land usage, aesthetics, and complex roadway and viaduct alignments that are mostly found in and around urban centers. The first significant investigations into the design and analysis of horizontally curved steel I-girder bridges began in 1969. At that time, the Federal Highway Administration (FHWA) formed the Consortium of University Research Teams (CURT). This group consisted of researchers from Carnegie-Mellon University, the University of Pennsylvania, the University of Rhode Island, and Syracuse University. CURT?s analytical and experimental work, combined with research efforts conducted at the University of Maryland, formed the basis for the American Association of State Highway and Transportation Officials? (AASHTO) Guide Specification for Horizontally Curved Highway Bridges (herein referred to as the Guide Specifications). This document was first issued in 1980 and was subsequently updated in 1993 and 2003. However, the document was never adopted by AASHTO as a full or standard specification because of knowledge gaps that existed in the entire design and analysis processes for this type of bridge. 1 In the early 1990s, the Curved Steel Bridge Research Project (CSBRP) was initiated. This project focuses on the area of horizontally curved steel girders. The research project participants include the FHWA, the Transportation Research Board (TRB), and the participating states of the Highway Planning and Research (HP&R) study. The primary objective of this research study is to better define the behavior of such bridges. The study involves theoretical work leading to the development of refined predictor equations and to the verification of those equations through linear and non-linear analyses and experimental testing. The CSBRP effort was largely based on recommendations of the Structural Stability Research Council?s (SSRC) Task Group 14 [SSRC (1991)]. Several priorities were identified for research by the SSRC group: ? develop an understanding of construction issues including fabrication and erection ? determine nominal bending and shear strengths ? understand the behavior of diaphragms, cross-frames, and lateral bracings ? define the effect of lateral loads ? determine the level of analysis needed for analyzing curved girders ? determine serviceability issues The goals of the CSBRP were to address these knowledge gaps, to generate enough information to improve the current Guide Specifications, and to incorporate curved steel girder design provisions into the AASHTO LRFD Bridge Design Specifications (herein referred to as the LRFD Specifications). 2 The Guide Specifications is the only consensus document available to the bridge community that supports the design and construction of horizontally curved steel I-girder bridges. In its current form, the guide is disjointed and difficult to follow. The commentary in the guide is incomplete and lacks the necessary details needed to explain the development of many of the provisions. Many of the original key references are not available to most designers. And when the references are available, they require a great deal of interpretation. The general lack of comprehensible support material available for understanding and clarifying the Guide Specifications can lead to misinterpretation of its provisions. This misinterpretation may result in overly conservative and uneconomical structures or in the development of bridges that do not meet the intended safety levels. This economic and safety uncertainty on structures that represent 30% of the steel bridge market is significant. In 1994, AASHTO published the first edition of the LRFD Specifications. These provisions introduced the load and resistance factor design method for the design of tangent girder bridges to the bridge engineering community. Since then, AASHTO, through the National Cooperative Highway Research Council (NCHRP), has been broadening the scope of the LRFD Specifications to make a fully integrated specification for the design of all common bridge types. The FHWA mandated that beginning in 2007 all bridges that are built with Federal Aid money must use the LRFD Specifications as the governing design provisions. To incorporate the horizontally curved girder bridge design into the LRFD Specifications, statistically significant data are needed to produce calibrated and refined predictor equations. Calibrated equations will produce a uniform 3 level of safety across bridge types and will improve the community?s ability to design and build economic structures. A review of the existing experimental data reveals a lack of appropriate results for inclusion into the statistical models. Figure 1-1 shows flange and web slenderness combinations from all previous experimentation that produced a flexure or flexure-shear combination failure. Figure 1-2 restricts the previous experimental data to just those tests performed in uniform bending. Figure 1-3 eliminates tests performed with unrealistic boundary conditions from the Figure 1-2 data. All of these figures show the design limits for both web and flange compact and non-compact behavior. The limited data shown in Figure 1-3 represent two points with slenderness combinations far from those that represent current best practice. These data cannot realistically be used to anchor the large analytical parametric study needed to produce statistically relevant information for use in the formulation and calibration of predictor equations for the LRFD Specifications. 0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 40 Compression Flange Slenderness W e b S l en der n es s CURT P2(PB) CURT P3(PB) Nakai(PB) CURT P1 CURT P2 CURT P3 Fukumoto Shanmugan 23 18 Compact Flange Limit Non- Compact Flange Limit Non-Compact Web Limit Compact Web Limit Figure 1-1: All Previous Experimental Slenderness Combinations 4 0 50 200 W b S l en e r n 100 150 300 0 5 10 15 20 25 30 35 40 ession Flange Slenderness e d ess 250 Compr CURT P2 CURT P3 Nakai 23 18 Limit Non-Compact Web Limit Figure 1-2: Slenderness Combinations From All Previous Uniform Bending Experiments Compact Flange Limit n- Compact Flange No Compact Web Limit 0 50 150 200 250 300 W e b S l e r n e 100 0 5 10 15 20 25 30 35 40 ge Slenderness nde s s Compression Flan CURT P3 23 18 Compact Non- Limit Non-Compact Web Limit Compact Web Limit F tions element based study. Flange Limit Compact Flange igure 1-3: All Previous Uniform Bending Experiments with Realistic Boundary Condi A large suite of experimental tests with the appropriate parameters would obviously be cost prohibitive for the community. Therefore, a focused and deliberate experimental effort is needed to supply significant and sufficient physical results to anchor a finite 5 1.2 Objective and Scope The objective of this experimental effort is to determine the flexural resistance of a White et al. (2001), herein referred to as the Unified Design Method. variety of full scale horizontally curved girder components with realistic boundary conditions. The test matrix will examine the influence of (i), compression flange slenderness, (ii), web slenderness, and (iii), web stiffening on moment capacity. These results will be used to validate a computer model similar to that used to produce the hundreds of virtual test results that form the statistical basis of the recently developed predictor equations by 1.3 Previous Experimental Work With a few exceptions, previous investigations have focused on single, scaled, doubly-symmetric horizontally curved I-sections tested with artificial torsional restrai provided at the ends. In some cases, this restraint was full fixity of the end. In other cases, a sole restraint against lateral movement provided at the end was used. In either ca end conditions of the girders in these investigations did not accurately represent the conditions produced by a horizontally curved girder bridge. Recently, several researchers [Linzell (1999), White et al. (2001), Grubb and Ha Zureick et al.(1994)] reviewed, critiqued, and synthesized most of the previous work this area as part of the FHWA CSBRP. The following sections will highlight previous experimental work performed on horizontally curved steel I-girders. An emphasis is nt se, the ll, in placed on those individual experiments from each investigation that produced a bending capacity type failure. 6 1.3.1 CURT Tests d t Carne niversity performed most of the experimental testing done for the CURT Pro tests are documented in great detail in Mozer ulver (1 Mozer, Oh nd Mozer, C er 5). A tota 22 failure loa ts on 11 plate I-girder specimens are described in the CURT Project. Twelve of thes ced information on moment or nt-shear capacity of horizontally curved girders (refer to Table 1-1 for a list of s). Data are erved elastic d n calculations b on analytic ped as f the C s include d uter aide deling analy ecause neither the finite elemen ware he microc uter were re or available tools to the researc me. Culver an Mozer a gie Mellon U ject. These and C 975); l nd Culver (197son a 5); a ook and Culv (197 l of d tes e experiments produ mome selected parameter presented comparing obs behavior an ultimate load capacity with predictio ased al methods develo part o URT ect. These inves Proj tigation d very limite comp d mo ses b t method soft nor t omp liable hers at that ti 7 Specimen ID Curvature l R Compression Slenderness Flange fc fc t b Web Slenderness w t D Overall mm (in.) Depth, CURT P1 Tests (1970) C8(2) 18.6 20.3 141 474.7 (18.69) C9(2) 6.3 20.3 150 476.0 (18.74) D13 7.4 23.4 150 474.5 (18.68) D14 7.4 23.0 149 476.0 (18.74) CURT P2 Tests (1971) L1(A) 9.9 15.2 149 473.7 (18.65) L2(A) 10.1 15.4 151 475.2 (18.71) L2(B) 10.1 15.4 151 475.2 (18.71) L2(C) 10.1 15.4 151 475.2 (18.71) CURT P3 Tests (1973) GI(3) 10.0 7.82 150 482.1 (18.98) GI(4) 10.0 7.82 150 482.1 (18.98) GI(5) 10.0 7.82 150 482.1 (18.98) GO(8) 10.6 15.7 58 476.8 (18.77) Fukumoto and Nishida Tests (1980) AR1 13.6 12.1 45 268.2 (10.56) AR2 29.8 12.2 44 268.5 (10.57) AR3 99.8 12.1 44 268.5 (10.57) BR1 12.1 12.0 45 267.0 (10.51) BR2 25.8 12.1 44 268.2 (10.56) BR3 172 12.0 45 267.0 (10.51) Nakai et al. Tests (1985) M1 15.0 178 824.0 (32.44) M2 14.7 15.2 177 821.4 (32.34) M3 12.3 15.0 178 821.7 (32.35) M4 5.2 15.0 177 821.7 (32.35) M5 5.3 15.1 248 824.0 (32.44) M6 5.4 15.3 257 821.4 (32.34) M7 5.3 15.1 178 824.0 (32.44) M8 4.7 7.6 175 824.0 (32.44) M9 4.5 15.0 175 824.2 (32.45) Shanmugan et al. Tests (1995) CB1 5.3 10.27 35.3 306.6 (12.07) CB2 7.9 10.27 35.3 306.6 (12.07) CB3 13.2 10.27 35.3 306.6 (12.07) CB4 19.7 10.27 35.3 306.6 (12.07) CB5 39.5 10.27 35.3 306.6 (12.07) CB6 18.9 10.27 35.3 306.6 (12.07) CB7 2.0 10.27 35.3 306.6 (12.07) WB1 5.3 10.33 35.25 306.1 (12.05) WB2 13.2 10.33 35.25 306.1 (12.05) WB3 39.5 10.33 35.25 306.1 (12.05) Flexural/Shear Failures Table 1-1: Summary of Previous Experimental Work That Produced Flexural or 8 Mozer and Culver (1975) contains the results from static load tests on seven scaled, doubly symmetric, welded plate girders (herein referred to as the P1 tests). The primary focus of this investigation was to determine the influence that a variety of geometric stress parameters had on flange local buckling for this type of girder. However, onl and y three of t ft) meters for l f local flange buckling compared fav ign can be conservatively used for horizontally curved girder design if the flanges are cut hese tests produced that failure mode. One experiment displayed a moment/shear interaction failure while the remaining investigations produced shear failures. The test components had radii that ranged from 115.2 m (378 ft) to 339.2 m (1,113 and were either heat curved or cut curved to produce their final horizontal geometry. Flange and web steels were ASTM A36 and AISI 1008, respectively. Other geometric variables included compression flange slenderness, web slenderness, and transverse stiffener spacing. Table 1-1 contains a specimen matrix of limit geometric para the specimens from this set of tests that exhibited flexural or flexure-shear interaction failure. The P1 test girders had 3.0 m (10 ft) arc length spans that were supported on radia aligned rollers at both ends. The girder ends were also restrained from lateral translation and twisting by radial aligned bracing. Load was applied eccentrically at mid-span to produce a desired combination of warping and primary bending stresses in the compression flange. All specimens had 1.5 m (5 ft) unbraced lengths. The results of the P1 tests that failed as a result o orably with predictions made using equations based on the Elastic Beam theory developed by Culver and McManus (1971). The authors concluded that the contemporaneous compression flange slenderness limitations for straight girder des 9 cur slen a desired ratio of warping to bending stress. These tests were done with a 3 m (10 at one end of the overall 4.6 m (15 ft i designed to produce either a shear failure (L1 series) or a flexure-shear interaction failure (L2 seri The sistent with those employed for the P te perties are ved, and first yield is defined at the flange tip where the primary bending and warping stresses are additive. If the design preference was to neglect consideration of warping stresses, then the authors recommended limiting curved girder compression flange derness to the contemporaneous straight girder compact section requirements. Mozer, Ohlson, and Culver (1975) investigated two horizontally curved I-girders, each tested with three separate loading arrangements (herein referred to as the P2 tests). The primary difference between the two specimens, designated as L1 and L2, was the transverse stiffener detail that was used. One focus was to determine the effects of partial versus full depth stiffeners on flexural resistance. Each specimen was failed using three loading regimes, A, B, and C. The A regime consisted of 4 point loading applied at the third points along the 4.6 m (15 ft) arc length of each simple span girder. The arrangement was designed to produce a flexural failure in the compression flange within the constant moment region of the girder. The B regime and C regime were nearly identical, involving a single point load located eccentrically similar to the P1 tests to produce ft) arc length simple span leaving a 1.5 m (5 ft) overhang ) g rder. All tests had 1.5 m (5 ft) unbraced lengths. The experiments were es) in the girder panel adjacent to the load. P2 tests used bearing, bracing, and load details con 1 sts. The P2 girders had a 15.2 m (50 ft) radius. Relevant girder pro tabulated in Table 1-1 for the four tests in which flexural was involved in failure. 10 The author?s P2 test conclusions for flexural resistance supported those conclusions made in the P1 tests. The conclusions also indicated that adequately braced compact compression flanges were capable of developing significant post-yield bending capacity. he 5.7 m ich detail a capacity failure. Tests 5 and te e inside The P3 test program included the following objectives: ? determining the bending strength of a curved plate girder in a curved bridge system ? monitoring the inelastic redistribution of load within the bridge system ining the capacity of curved web plates curved I-girder bridge behavior when the structure is an open grid, the Culver-McManus Mozer, Cook, and Culver (1975) investigated a pair of doubly symmetric I-girders that were concentrically curved, transversely spaced at 0.9 m (3 ft), and connected by five rigid cross frames and two rigid end diaphragms (herein referred to as the P3 tests). T P3 test frame had a centerline span of 4.7 m (15.5 ft) and a radius of curvature of 1 (51.5 ft). The girder ends were held down to prevent unpredictable uplift during testing. Eight individual test results are reported, six of wh 8 used third point loading to produce a constant moment region over an approxima 1.5 m (5 ft) unbraced length and local flange buckling failures in the inside (GI) and outside (GO) girders respectively. The remaining tests used a single applied load at mid- span. Tests 3 and 4 produced flexure-shear interaction failures at different locations of the inside girder. Test 1 and Test 2 produced shear failures on different panels of th girder. ? determ ? monitoring the influence of transverse stiffeners on web behavior Among other conclusions, the researchers stated that cross-frames play a major role in 11 equations [Culver and McManus (1971)] are conservative when used to calcula resistance, and that a considerable degree of reserve streng te flexural th above initial yield exists in cur ed ers. e al g con 1.3.2 University of Maryland Tests Contemporaneous to the CURT program, several experimental studies were conducted at the University of Maryland on the behavior of curved I-girders, box-girders, and systems as part of a large experimental and analytical program titled The Design of Curved Viaducts. This program was co-sponsored by the Maryland State Highway Administration and the FHWA. The program?s objectives were to produce analytical tools for the design and evaluation of curved girder bridges. A series of progress and ved plate girders with compact compression flanges. To prove their analytical methods and the computer analysis program developed as part of the CURT program, Brennan and Mandel (1971, 1974) built and elastically test small-scale similitude structures. These small-scale structures were used to develop influence lines for deflection, moment, and shear for each girder of the structures modeled. The experimental results were compared with the computer generated results with good agreement reported by the research Shore and Lapore (1975) built several very small curved girder and curved bridg models that were exercised elastically to produce data that would support their numeric efforts. Their report details the experimental work and results as well as the work bein done to develop a finite element approach to curved girder analysis. However, the report does not draw conclusions. The researchers planned to report comparisons and clusions in a follow-up effort. 12 interim reports were issued to the sponsoring agencies detailing the individual experimental and analytical efforts of the larger program. Spates and Heins (1968) used four individual elastic loadings to evaluate the be of a single curved beam cold rolled to a 15.2 m (50 ft) radius. The arc length of the span was 9.1 m (30 ft), and the ends were designed to be fixed with respect to bending and torsion. The steel section used, S180x22.8 (S7x15.3), had a nominal yield strength of 2 MPa (30 ksi). Load was applied by radially cantilevering havior 07 lead weight off the beam at mid estigators? red ft) single composite girders with varying end conditions and slab thickness. Torsion was applied at one end of the girder using a force couple while the other girder end was either pinned or fixed. All tests utilized a 0.3 -span. Strain and deflection information was compared with analytical predictions from equations developed for single girders. The major problem encountered during this investigation was the experimental control or establishment of the desired end conditions. Even with extensive effort, the experimental data showed that truly fixed ends were not achieved. The inv uction of data and analytical comparisons lead them to conclude that end conditions can be very significant on curved girder plane bending behavior of a single girder. In the analytical portion of their investigation, Spates and Heins demonstrated how predictor equations developed for a line girder design were very conservative when used to design the individual girders of a curved bridge system. Kuo and Heins (1971) conducted experimental testing to determine the torsional rigidity, warping behavior, and failure mode of composite I-girders subject to torsion. Four experiments were performed on 5.5 m (18 13 m (1 ft) deep wide flange section and a 0.9 m (3 ft) wide composite slab with a 51 mm ( in.), 76 mm (3 in.), 102 mm (4 in.), or 152 mm (6 in.) thickness. In all four tests, the results indicated that the concrete slab dominates torsional behavior and that warping effects were negligible for t 2 he slab, but were very significant for ause ory the ctors and can be neglected if the source of the effects is from vertical loads acti he ction. sign 1.3.3 Japanese Tests Two major experimental programs were conducted in Japan to support the Hanshin Expressway Corporation?s Guidelines for the Design of Horizontally Curved Girder the girder. Rupture of the concrete slab due to diagonal tension was the reported c of failure for each experiment. Analytical comparisons using the Thin-Walled the yielded excellent correlation with experimental results. The main objective of Colville (1972) was to develop appropriate design criteria for welded stud shear connectors in curved composite sections. The experimental program consisted of four individual tests on 5.4 m (17.75 ft) arc length horizontally curved and composite concrete slabs and I-beams. Test parameters included radius of curvature, girder size, number of shear connectors per section, and type of loading. Colville concluded that the effects of torsion and warping are not significant on shear conne ng on curved members. However, the design procedure developed does consider t transverse shear forces that result from the bending and warping of the composite se The design procedure does converge to the straight girder procedure when the radius becomes large. The reader is also reminded that the data used to develop the de procedure were generated from composite slabs in compression; therefore, the results may not be valid in negative moment regions. 14 Bridges. These guidelines and the Guide Specifications are the only two specifications for horizontally curved steel bridges in the world. While most of the literature associated wit hite et Load was supplied with a gravity simulator at mid-span; although, the details of the system used were not reported. These specimens had a nominal compression flange slenderness of 12 and web slenderness of 45, which is very unrepresentative of bridge girders. The girders had an overall depth of less than 279 mm (11 in.) and had radii of 23.2 m (76 ft) to approximately 483 m (1,584 ft). Table 1-1 contains parameters for individual specimens. The experimental results showed good agreement to both the theoretical solution presented and the approximate solution proposed. Nakai et al. tested nine scaled doubly symmetric components. Parameters for all specimens, M1 through M9, are included in Table 1-1. The girders were tested for flexural capacity in near uniform negative bending with the ends completely restrained from translation or out-of-plane rotation. All but one of these specimens had a compression flange slenderness of 15, and most had a web slenderness of approximately 175. Specimen M8 had a compression flange slenderness of 7.6. Two specimens, M5 and M6, had a web slenderness of approximately 250. One of these pair of specimens employed a longitudinal stiffener to stabilize the web while the other did not in an effort to quantify the effect of that web attachment on bending capacity. A reduction in capacity h these programs is published in Japanese, other researchers [Linzell (1999), W al. (2001), Grubb and Hall] have reviewed this work. Fukomoto and Nishida (1981) tested six simple-span scaled doubly symmetric I- girders that had laterally restrained ends that were fabricated out of steel with an approximate 235 MPa (34 ksi) yield strength. 15 com er analytical prediction was reported for these test f the difference in behavior between hot-rolled beam ntal ing. Also, nearly a dozen field test studies have reported m pared with an equivalent straight gird s. While the Nakai tests were conducted with girders of appropriate slenderness combinations and section depths for bridges, the specimens had a span to depth ratio o approximately 2.5. At this ratio, an assumption is made that the highly restrained girder ends affected the demonstrated flexural resistance. At the very least, the configuration tested relates poorly to bridge girder realties. 1.3.4 Other Experimental Testing Shanmugam et al. (1995) compared experimental results with predictions made with a refined finite element model. The experimental program consisted of 10 tests to failure of single simple-span curved girders with various unsupported lengths and end conditions fabricated out of steel with a nominal strength of approximately 276 MPa (40 ksi). The primary focus of the testing was to contrast s and welded plate girders. All specimens were cold-bent into their final horizo curvature and had load applied at a single point. These girders were very small with an overall depth of about 305 mm (12 in.). Daniels et al. (1979) at Lehigh University primarily investigated fatigue issues on horizontally curved steel I-girders. Nakai and Kotoguchi tested a pair of horizontally curved I-girders for systematic lateral buckl ostly limited elastic behavior data acquired primarily during the construction of horizontally curved steel I-girder bridges or from structures already in service. 16 1.4 Strength Predictor Equations The current Guide Specifications (2003) uses governing equations for flange stress that are slight modifications of the original work by Culver and McManus (1971) that was sponsored by the CURT program. Culver and McManus built on the First-Order theory for determining the stresses and deformations in horizontally curved beams normal to their plane of curvature. This theory was first developed by Vlasov (1961) and Dabrowski (1968). The derivation of the Culver-McManus equations was based on doubly-symmetric and prismatic curved I-girders with compact and non-compact compression flanges that were braced at a un loaded iform spacing and subject to a constant ver cts ted for by the ? -factors defined in Appendix B. Culver and McManus developed the ? -factors by performing approximate second order elastic analyses on a range of I-girder geometric parameters, subtracting first order behavior from the results, and fitting a curve through the findings. The ? -factors are also the weakness of the Guide Specifications. Their derivation includes many assumptions that cannot be uncoupled from the results. A predictor equation is also used for tangent girder lateral torsional flange buckling (Equation B-3 in Appendix B) that has since been replaced in the AASHTO Standard Specifications for tical bending moment. The Guide Specifications? equations have been extended to be valid for singly symmetric I-girders by Hall and Yoo (1998). The Guide Specifications? provisions that apply to the design of non-composite I-girders in flexure are summarized in Appendix B. The strength of the Guide Specifications? provisions is that an engineer is only required to produce a first order analysis of the structure for design. Second order effe are accoun 17 the Design of Highway Bridges and LRFD Specifications for straight girder design with a more accurate formulation. The ? -factor equations fail to recognize the amount of rigor emp n nd, they can be used to design for lateral loading from all sou lly, act loyed in the structural analysis process forcing a common design procedure for all levels of investigation. Also, a careful review of the ? -factor formulations by Hall et al. (1999) has revealed some inaccuracies in how warping stresses are accounted for resulting in an unintended doubling of their effect. Finally, the ? -factor equations do not converge to any resemblance of the tangent girder design equations when the radius of curvature becomes very large. They also include a step discontinuity in behavior betwee compact and non-compact flanged sections. The Proposed Unified Design Method provisions are also summarized in Appendix B. This design method has several advantages. First, the provisions are independent of the analysis method used. Seco rces, not just vertical loading on horizontally curved girders. Third, the design equations reduce to the tangent girder design equations when the radius is large. Fina this method has eliminated the step discontinuity between non-compact and comp behavior. 18 Chapter 2. Experiment Design ogy on the philosophy behind the Curved Steel Bridge Research Project (CSBRP) including the development of the experiment design was reported by Grubb and Hall. A review of the limited curved girder experimentation to date demonstrates the significant challenges inherent with producing relevant capacity data for this very complex structure type. As previously mentioned most documented experimental investigations have been tests on individual, doubly symmetric I-sections with proportions or scale that do not represent the family of girders typically used for bridges. Also, these investigations generally assumed some level of restraint for the ends of the test girder and at bracing or loading locations that does not replicate the structural behavior of a bridge system. t of d to live-load stresses in the gird A very detailed and complete chronol Full scale testing eliminates scaling issues. In many of the previous tests described above, girders were fabricated from very thin plate and sometimes from sheet steel. Steels in this thickness range retain very high levels of residual stress and distort significantly out-of-plane as a result of the high heat that they are subjected to as par any welding process. These stresses and distortions can cause premature yielding or buckling that can decrease the ultimate capacity of a section. Also, many structural relationships are not linearly dependent. For instance, in dynamic tests, dead load?often called compensatory loading?needs to be added to a scaled bridge system without adding stiffness to produce a representative ratio of dead-loa ers or for added inertia. In static structural experimentation, the desired moment/shear 19 capacity ratios are difficult to maintain using scaled geometric properties. The full-scale structure used for this experimental program mitigates all of these concerns. 2.1 Test Frame Concept le demonstrated the highly non-linear behavior of the post-peak single girder. In the final analysis of the project team, testing of a three-girder system was necessary to avoid the limitations and weaknesses of previous work and to safely produce the quantity and type of physical data needed within the financial means provided. The CSBRP team employed the following philosophy to develop the test frame: The test frame needed to be flexible enough to accommodate testing components that would be subjected to a constant moment (pure bending) and moment-shear interaction, and the test frame had to be adaptable for a composite bridge test. The method for both sets of component tests was to insert a test specimen into the exterior test frame girder and connect it to the test frame with bolted splices and cross-frames. The test frame girders and the cross-frames were proportioned using a variety of materials and sections to remain elastic while providing realistic interaction to the test component as it experienced significant inelastic deformation. Once a test was finished, the component was replaced and the process was repeated until the series was complete. The CSBRP team developed the three-girder bridge system shown in Figures 2-1 and 2-2. The span of the test frame was limited to 27.4 m (90 ft) because the FHWA The feasibility of single girder testing was considered for the CSBRP. Considerab analytical effort was focused on designing a set of bracing, loading and bearing details that could mimic the boundary conditions and internal load sharing of a bridge system, particularly the distribution of lateral flange bending moment. These analyses 20 21 conducted additional unrelated experimental research in the Structures Laboratory during the tenure of the CSBRP. A radius and unbraced length of 61.0 m (200 ft) and 4.57 m (15 ft) respectively, measured along the centerline of the middle girder were selected to test the upper range of the practical limits of R l for a structure of this span. Once a span, radius and unbraced length were determined, the project team solved for an overall girder depth for the test frame using best practice design tools. Figure 2-3 shows the test frame in the FHWA Structures Laboratory configured for one of the bending component tests. 25'-4 3/4" R = 1 9 1 ' - 3 " R = 200' - 0 " R = 2 0 8 ' - 9 " 12 SP ACES @ 7'-6" = 90'-0" ? G IRD ER G2 MEASURED A LONG 76L 5L 4L 3L 2L 1L 6R 5R 4R 3R 2R 1R CROS S FRAMING SPACIN G 1 '- 0 " T Y P . C R E A C T IO N L C R E A C TI O N 1 '- 0 " T Y P . L GIRD ER G 290'-0 " MEASU RED ALONG ? LA TE R LA L B R A C IN G (T YP .) 30 '-3 3 /1 6" 4'-0 1 /16" C OF BOLTED FIELD SPLICE L 4'-0 1 /16" 30 '-3 3 /1 6" 28 '-6 1 /4" 28 '-6 1/ 4" 32'-11 1/2" 26 '-9 3 /8 " 26' -9 3 /8" 32'-6" C O F L OA D PO INT L C O F L OA D PO INT EXAMPLE CROSS-FRAM E DESIGNATION: S - 2L CROSS FRAME LINE SOUTH BAY EXAMPLE LATERAL BRACING DESIGNATION: LAT - SE SOUTH BAY EAST END LATERAL BRACE L C R O S S F R A M E L IN E S L C G IR D E R G 3 C G IR D E R G 2 L C G IR D E R G 1 L 8 ' - 9 " 8 ' - 9 " S OU T H B A Y N OR T H B A Y CR OS S FR AM E (T YP .) Figure 2-1: Plan View of Test Frame L C G2 L C G1 4 ' - 0 " 8'-9" 8'-9" NORTH BAY SOUTH BAY C G3 L Figure 2-2: Cross-Section of Test Frame at a Cross Frame Location 6L F T es m th W tr yt Fra e in e FH A S uctures Laboratorigure 2-3: he T The exterior girder on the inside radius of the test frame is herein referred to as G1. G1 is doubly symmetric and prismatic with flange plates measuring approximately 27 mm x 406 mm (1 1/16 in. x 16 in.) and a web plate measuring approximately 11 mm x 1,219 mm (7/16 in. x 48 in.). The interior girder of this three-girder system, referred to as G2, is also doubly symmetric and prismatic. The flange plates are approximately 30 mm x 508 mm (1 3/16 in. x 20 in.), and the web plate is approximately 13 mm x 1219 mm (? in. x 48 in.). The exterior girder on the outside radius of the test frame, G3, is made up of three doubly symmetric and prismatic sections connected by two bolted splices. The flange plates of G3 measure approximately 57 mm x 610 mm (2 1/4 in. x 24 in.), and the web plate is approximately 13 mm x 1219 mm (? in. x 48 in.). This girder was fabricated in three sections so that the center section could be replaced with each of the bending or moment-shear interactio o develop the full plastic moment of the strongest bending component (component B6) without slip. ombinations slightly exceed the limits in the ile n components. The splices were designed t With the overall depth of the girders established, the matrix of test specimens was easily developed for both the bending component and moment-shear interaction component series. The tested parameter combinations were selected to best fulfill the objective and to provide a broad enough set of information on which the analytical work could be based. Figure 2-4 shows how the slenderness combinations for the bending component series of tests compare with the current Guide Specifications compact and non-compact limits. The selected slenderness c figure because the Guide Specifications slenderness limits were altered in 2003 wh the test matrix was originally designed using the 1993 version of this document. 25 Compression Flange Slenderness 0 10203040 W eb S l er ness end 0 50 150 250 100 200 300 Compact Flange Limit Non-Compact Web Limit Non-Compact . he ter of 127 mm (5 in.) and a wall thickness of 6 mm (? in.). Th n its flexural capacity approximated that of the mem determined by two independent methods throughout the elastic range of behavior. These Flange Limit Compact Web Limit Figure 2-4: Bending Component Test Matrix The test frame utilized the ?K-type? cross-frame and diaphragm shown in Figure 2-2 However, to reduce the instrumentation demand and to ease interpretation of results, t single-leg angles that typically are used to make up horizontal and inclined legs of the cross-frames and diaphragms were replaced with round structural steel tubing. The tubing used had a nominal outside diame is tubi g size was selected because bers used in a more conventional design. Use of the test frame also provides for redundancy in the analysis of the inelastic behavior of the test components. Flexural resistance of the test components can be 26 analysis methods, called the Direct Method and the Indirect Method, rely on different instrument subsets from the extensive instrumentation plan (800+ channels of data acquisition) for their calculation. The instruments are primarily made up of strain, load and t 2.2 Component Test Matrix displacement indication devices and are applied to strategic locations within the tes frame and the bending components. Besides insuring an appropriate interpretation of results, the experiment data were used to validate a fully material and geometric non- linear finite element model. This model incorporates the as-built steel plate widths and thicknesses, and steel plate specific material properties based on the large suite of materials tests performed as a part of this project. The test frame was designed to be versatile. By reconfiguring the load and reaction locations, the test component location in G3 could be subjected to either constant moment (referred to herein as the bending component series of tests) or to a combination of high moment and high shear (referred to herein as the moment-shear interaction component series of tests). The bending component series included seven individual component specimen tests and are the primary subject of this dissertation. The moment-shear component series included individual tests conducted on four component specimens that are the subject of another report. erlapping set of parameters by incorporating characteristics shared by other members of the test matrix. These shared characteristics were intended to produce 2.2.1 Bending Component Series Each of the bending components, identified as B1 through B7, was designed to investigate an ov 27 suff The B1 web design was also used for components B5, B6 and oubly mpon 2 and esi ith a thic plate than B1 lowering their web slenderness to 128.0. The differing characteristic between B2 and B3 is how their web plate was stiffened. While the web plate of component B2 had transverse stiffeners spaced again at approximately 0.98D, the web plate of component B3 was left unstiffened between cross-frame locat in a 3.92D for onent B3 C onent B4 designed ession f slend of 23. section was made s ymmetri a larg ang rea compression of approximately 0.62D, which re web slenderne The doubly symmetric component B5 was d ith a flange slende 17.5, which is close to the compact flange Specifications. icient information to quantify the effects of compression flange slenderness, web slenderness and transverse web stiffening on the flexural capacity of horizontally curved steel I-girders. Component B1 was designed doubly symmetric with a flange slenderness, b f /t f , of 23.3, a web slenderness, 2D c /t w or for doubly symmetric sections D/t w , of 153.6 and transverse stiffener spacing, d o , of 0.98D. These slenderness values slightly exceed the limits, 23 and 150 respectively, included in the AASHTO Guide Specifications for a stiffened non-compact girder. The B1 compression flange design was also used for components B2, B3 and B4. B7. The d symmetric co ents B B3 were d gned w ker web ions. This resulted d o of comp . omp had a compr lange erness 3, but the ingly s c with e tension fl e to c te a depth of web in sulted in a ss of 189.2. esigned w rness of limit of 17.0 specified in the AASHTO Guide 28 Com c with compact flanges. B6 was f n flange of e n s of the bending component test series are compiled in Table 2-1. Test Co Compression Slenderness ponent B6 was also designed to be doubly symmetri detailed with a flange slenderness of 13.6, which is well within the compact range o the AASHTO Guide Specifications. The singly symmetric component B7 was designed with a slender compressio qual area to the tension flange. This flange combination generates a depth of web i compression that is very close to the mid-height of the girder maintaining the desired web slenderness of 153.6. This test component was designed to investigate the effects of a compression flange slenderness of 33.6, which is well in excess of the AASHTO Guide Specifications? limit of 23. The target parameter Web mponent Flange fc fc t b Slenderness w c D2 mm t Overall (in.) Panel t Ratio Notes Depth Aspec B1 23.3 153.6 1257 0.98 Top flange and limits (49.5) web near non-compact B2 23.3 128.0 1257 0.98 B1 with a stockier (49.5) web B3 23.3 128.0 1257 3.90 B2 with an (49.5) unstiffened web B4 23.3 189.2 1270 (50) 0.98 Singly symmetric B5 17.5 153.6 1267 0.98 Top flange near (49.875) compact limit B6 13.6 153.6 1280 (50.375) 0.98 Very compact top flange B7 33.6 153.6 1254 (49.375) 0.98 Slender top flange Table 2-1: CSBRP Bending Specimen Target Parameter Test Matrix 29 2.2. action Component Series ess combinations that duplicated tho o = s placed at a spa 2.3 Fabrication of Test Frame and Bending Components 2 Moment-Shear Inter Although the results of the moment-shear interaction component series tests are not included in this report, a brief description of these components is included in this section because the test frame was also designed to appropriately test these specimens. The moment-shear interaction components were labeled MV1, MV1-S, MV2 and MV2-S. MV1 and MV1-S had flange and web slendern se used for B1. MV2 and MV2-S had flange and web slenderness combinations that duplicated those used for B5. MV1 and MV2 had a transversely unstiffened web, d 3.92D, while the webs of MV1-S and MV2-S had transverse stiffener cing of d o = 0.98D. All test series components and test frame components were fabricated with material and workmanship in accordance with the provisions and tolerances of the AASHTO Standard Specifications (15 th Edition including the 1993 and 1994 Interims) and the American National Standards Institute (ANSI)/AASHTO/American Welding Society (AWS) D1.5 Bridge Welding Code (1988 Edition including 1989-1994 Interims). In addition, the design drawings specified that all girder and component specimen flanges should be cut curved and that heat adjustments could be made to obtain the desired final geometry with approval of the design engineer. me girders, the cross- frames and diaphragms, and the different component test series. 2.3.1 Materials A variety of steels were used in the fabrication of the test fra 30 2.3.1.1 Girders Two steels were used to fabricate the horizontally curved girders of the test frame. G and G3 were fabricated from AASHTO M270M Grade 345 (M270 Grade 50) or A A572M Grade 345 (A572 Grade 50) steel herein referred to as A572 steel. G2 was fabricated from plates of AASHTO M270M Grade 480W (M270 Grade 70W) or AST A852M (A852) steel herein referred to as A852 stee 1 STM M l. at approximately 6.1 m (20 ft) measured along the girder centerline from either end of each flange. 2.3.1.2 Cross-Frames and Diaphragms ural f ss- e ding experienced by cross-frames N6L and N6R during testing, their connections were made using ASTM A490 high strength bolts. Both the flange and web plates were cut curved to produce the necessary horizontal and vertical curvature for each girder. Flange and web plates were attached using overmatched fillet welds produced with the submerged arc process. Because of the quenching and tempering process required to produce the A852 steel limits plate lengths to approximately 15.4 m (50 ft), two butt welds were needed in each flange of G2. These full penetration groove welds were made The K-type cross-frames and diaphragms used an ASTM A513 Grade 1026 struct steel tube for all horizontal and inclined legs. The tubes were attached to double gusset plates of A572 steel at each bolted connection location with a full penetration groove weld. To ease erection, the lower legs could be removed from the upper delta portion o the cross-frames and diaphragms (see Figure 2-2). All connections, except those on cro frames N6L and N6R, were made with ASTM A325 high strength bolts. Because of th level of loa 31 2.3.1.3 All bending component and moment-shear interaction component flanges and webs were fabricated from A572 steel. The bending components, with the exception of spe n B7, were fabricated in the same manner as the girders of the test frame. The splice plates used to secure the inserted bending co t into the te e were dril n place and w so made of A572 steel. ding compon was an addition to the original test matrix. This component test was add t six bending component tests and the beginning of the moment-shear interaction series of tests. B7 was fabricated by using heat to restore, within tolerance, the tension (bottom) flan s lated in Tab Bending Components cime mponen st fram led i ere al Ben ent B7 ed to most effectively use the downtime between the end of the firs ge and web of bending component B1 and by replacing the compression (top) flange with a plate of almost equal area and increased slenderness. 2.3.2 As-Built Geometry While the component fabrication was completed within the AWS and AASHTO tolerances, the as-built geometry slightly altered the target design slenderness of both the flanges and the web at the critical section (mid-length) of each member. In most cases, these minor changes in the slenderness ratio were the result of plate material that wa slightly thicker than the nominally specified thickness due to permitted manufacturing tolerances. The bending component series as-built slenderness ratios are tabu le 2-2. 32 Component Compression Flange Slenderness fc b Web fc t Slenderness w c t D2 Tension Flan ge Slenderness ft ft t b B1 22.8 147.0 22.9 B2 22.8 119.6 22.8 B3 22.7 119.5 22.9 B4 22.8 188.0 16.5 B5 17.0 143.6 17.1 B6 13.4 141.5 13.3 B7 32.5 144.2 23.2 Table 2-2: CSBRP Bending Specimen As-Built Parameter Test Matrix 2.4 Material Properties Tension test specimens were cut from coupons taken from each steel plate used in th fabrication of the test frame and components. Coupons were a e lso taken from the rolled sections that m and the tangential support frame, and from the stru as lication of flange and web thicknesses used throughout the test matrix, sev flanges of ade up the lateral bracing ctural steel tube sections from which the cross-frames were comprised. Three coupons were taken from each steel plate used for flange material and six coupons were taken from each steel plate used for web material. Static yield testing in accordance with the Structural Stability Research Council (SSRC) (see Galambos, 1988) provisions w conducted on most of the tension test specimens cut from each coupon. In general, tension tests were performed until two qualified results were obtained for each coupon location. A detailed set of results for these tests is available in Appendix A. Due to the dup eral elements often could be cut from the same steel plate. The compression components B1, B2, B3 and B4 were all cut from Plate 21. The tension flanges of components B1, B2 and B3 were all cut from Plate 22. Both the compression and tension 33 flanges of components B5 and B6 were cut from Plates 23 and 24, respectively. The tension flange of component B4 was cut from Plate 25. 2.4.1 Plate Coupon Locations Figures A-2 through A-14 show the location and orientation of the six coupons take from the steel plates used for web material in both the test frame and bending components. The location and orientation for the three coupons taken from the steel plates used for flange material can be seen in Figures A-15 through A-27. The co taken from either end of the steel plate, designated as A and C on these figures, are located at mid-depth and oriented to be parallel to a tangent to the end of the horizontally curved flanges. The coupon at mid-length, designated B, is locate n upons d near one side of the plate and is oriented to be parallel to the direction of rolling. ses, ngation and tensile strength. In this doc d in static yield strength and the ultimate yield strength results from individual plates were used to build true stress-true strain relationships suitable for use by 2.4.2 Tensile Strength Testing The tensile tests were performed in accordance with the ASTM E8, Standard Test Methods for Tension Testing of Metallic Materials standard test method. In most ca the E8 procedures were supplemented with the Structural Stability Research Council?s (SSRC) Technical Memorandum No. 7: Tension Testing to generate consistent and uniform static yield strength levels. The E8 methods and procedures are designed to specifically determine yield strength, yield point elo ument, the definitions of these terms are consistent with those definitions provide the E8 Standard. The static yield strength of individual plates was used in the analysis of the experimental data. The 34 the pendix A contains a complete discussion of the tensile test the brication of the CSBRP bending component compression flanges. The purpose for this series of tests was to confirm that the behavior of t of , used without m analytical modeling effort. Ap results and their conversion to true stress-true strain. 2.4.3 Compressive Strength Testing The compressive strength tests were performed in accordance with the ASTM E9, Standard Test Methods of Compression Testing of Metallic Materials at Room Temperature standard test method. These tests were limited to specimens taken from steel plates that were used in the fa he steels used was complementary in both tension and compression. A complete set results for the compression tests is also included in Appendix A. 2.4.4 Elastic Modulus Testing The elastic modulus testing was performed in accordance with the ASTM E111, Standard Test Method for Young?s Modulus, Tangent Modulus and Chord Modulus standard test method. Ten Young?s modulus tests were conducted as a part of this program. Parameters included steel grade and plate thickness. The E111 Standard was odification to conduct the testing. Standard plate-type tension specimens, as described in Appendix A.1.2, were selected as the test specimens because the testing was performed in the tension stress-strain domain. As a result of this testing, a Young?s modulus of 204,000 MPa (29,600 ksi) was selected for use in both the experimental data analysis and in the finite element analysis of this project. Appendix A contains a discussion that details how this value of Young?s modulus was selected. 35 2.5 Instrumentation Plan A detailed and sc of h inst as developed for these experim how these instruments were deployed is included in Linzell This plan ts of ove 800 hard- ired instru ated by four separate data acquisition systems. Only the instruments that data tha were used in analysis and that a ssential to this report are n this s n. 2. Each of the girders, cross-frames and lateral braces were instrumented at multiple sections during each of the bending component tests. Load cells monitored reactions at the girder ends as well as applied load at the hydraulic jack locations. Both of the independent channels of each load cell were recorded by separate data acquisition systems during testing to ensure redundancy of information. The load cells used to measure girder reactions had a 1,335,000 N (300 kip) capacity, while those used to monitor applied load had a 445,000 N (100 kip) capacity. Strain gages were used to characterize sectional behavior at 10 locations throughout the test frame. On G1 and G2, strain gaged sections near each load point and at mid-span were monitored during each test. G3 sections near each load point and near cross-frames N4L and N4R were monitored during each bending component test. The location of each instrumented cross-section within the test frame is shown in Figure 2-5. This figure also indicates the instrument configuration at each location. A summary of instrument configurations and locations is contained in Table 2-3. The instrument configurations used are illustrated in Figures 2-5 through 2-12. complete de ents and ription ow the rumentation plan w (1999). consis r w ments, subsets of which are interrog produced t this re e described i ectio 5.1 Test Frame Instrumentation 36 Configuration (Figure) 1 (2-5) 2 (2-6) 3 (2-7) V1 V2 V3 V5 V6 37 G3 and Bending Component Location Label G2 Location Label G1 Location Label # Electrical Resistance Strain Gages # Vibrating Wire Strain Gages D, E 22 A, J A A 15 C, H 4 (2-8) F 7 15 (2-9) B B 7 8 (2-10) G 4 18 (2-11) B, I 11 11 (2-12) C C 11 4 Table 2-3: Configuration and Location of Strain Gaged Sections 38 B R B B R B R B R ( T Y P . ) R B R B R N 26 '-2 " (B ) A (2) B (V2) C (V6 ) A (2) B (V5 ) C 5L L 8" B R ( T Y P . ) 8" C 4L L 41'-0 3/8" (C) A (2) 8" C 6L L C (3) B (V2) C (V6 ) 8" C 5 R L I (V5) J (2) 8" C 4R L F (V1) 8" L C 7 E (1) D (1) H (3) 8" C 6R L 8"3'-3 " G (V3) 3'-3" 88'-0 15/16" (A) 25 '-6 " (D ) 35 '-3 3 /8 " (F ) 25'-4 3/4" (G) 35 '-3 3 /8 " (E ) SECTION LOCATIO N (TYP.) INSTRUMENTATIO N CONFIGURATION (TYP.) Figure 2-5: Location of Instrumented Cross-Sections B5 B6 B7 B1 B2 B3 B8 B4 W3 W6 W2 W5 W1 W4 Center of Curvature T5 T1 T7T6 T2 T3 T8 T4 D D / 4 D / 4 D / 4 D / 4 Electrical Resistance Strain Gage (Typ.) Location (Typ.) Strain Gage SYM. b /2 ft b /4 ftft b /8 ft b /8 fc fc b /2 fc b /4 fc b /8 S M.Y b /8 Figure 2-6: Instrumentation Configuration (1) 39 D / 4 B5 B6 B1 SYM. B7 B8 B4 W6 Location (Typ.) Strain Gage Strain Gage (Typ.) Center of Curvature Electrical Resistance W4 D / 4 D / 4 D W5 D / 4 T8T5 T2T1 T3 T4 b /2 b /4b /8 ft ft ft b /8 ft b /8 SYM. b /8 fc b /4 fc b /2 fc fc Figure 2-7: Instrumentation Configuration (2) 40 B5 SYM. D / 4 B8 SYM. D / 4 D D / 4 D / 4 T1 Center of Electrical R Strain Gag esistance e (Typ.) Curvature Location (Typ.) Strain Gage T4 b /2 ft ft b /8 fc b /8 b /2 fc Figure 2-8: Instrumentation Configuration (3) 41 D / 4 B5 B6 B1 B2 SYM. B7 B8 B3 B4 W3 W6 Location (Typ.) Strain Gage Strain Gage (Typ.) Center of Curvature Electrical Resistance W1 W4 D / 4 D / 4 D W2 W5 D / 4 T8T7T6T5 T2T1 T3 T4 Vibrating Wire Strain Gage (Typ.) b /4 b /2 ft ft ft b /8 ft b /8 SYM. fc b /8 fc b /8 fc b /2 fc b /4 Figure 2-9: Instrumentation Configuration (V1) 42 B7 B1 B5 B6 SYM. D / 4 W6 B8 B4 W4 D / 4 D W5 D / 4 T5 D / 4 T1 T3T2 Center of Electrical Resistance Strain Gage (Typ.) Curvature Location (Typ.) Strain Gage T8 T4 Vibrating Wire Strain Gage (Typ.) ftftft b /2 ft b /4b /8 b /8 SYM. b /8 fc b /2 fc fc fc b /8 b /4 Figure 2-10: Instrumentation Configuration (V2) 43 D / 4 B5 B6 B1 B2 SYM. B7 B8 B3 B4 W3 W6 Location (Typ.) Strain Gage Strain Gage (Typ.) Center of Curvature Electrical Resistance W1 W4 D / 4 D / 4 D W2 W5 D / 4 T8T7T6T5 T2T1 T3 T4 Strain Gage (Typ.) Vibrating Wire b /8 SYM. b /8 fc b /4 fc b /2 fc fc b /2 b /4b /8 ft ft ft b /8 ft Figure 2-11: Instrumentation Configuration (V3) 44 D / 4 Electrical Resistance Strain Gage (Typ.) B5 B6 B7 SYM. B8 D / 4 B2B1 B4B3 W3 W6 Curvature Center of Strain Gage Location (Typ.) D / 4 D W2 W5 W1 W4 D / 4 T4T3T1 T2 T6T5 T7 T8 Strain Gage (Typ.) Vibrating Wire ftftft b /2 ft b /4b /8 b /8 SYM. fc b /2 b /8 fc b /8 fc b /4 fc Figure 2-12: Instrumentation Configuration (V5) 45 B7 B1 B5 B6 SYM. D / 4 W6 B8 B4 W4 D D / 4 W5 / 4 D T5 D / 4 T1 T3T2 Center of Electrical Resistance Strain Gage (Typ.) Curvature Location (Typ.) T4 Strain Gage T8 Strain Gage (Typ.) Vibrating Wire b /2 b /4b /8 ft ft ft b /8 ft SYM. b /8 b /8b /4 b /2 fc fc fc fc Figure 2-13: Instrumentation Configuration (V6) 46 2.5.2 Bending Component Instrumentation instrumented at the six sections indicated in Figure 2-5. The sections labeled E and F are located 200 mm (8 in.) either side of mid-length of the component. These sections were used to determine the critical mid-span strains during each bending component test. Section F used Instrumentation Configuration (V1) shown in Figure 2-9. The data produced by this instrumentation configuration captured the installation and dead-load effects experienced by each component prior to the applied load test. However, the instrumentation used at this section is primarily comprised of vibrating wire strain gages which have a limited reliable strain capacity, (<1800 ?e) and are very sensitive to distortion. Therefore, as the steel flanges of the components approaches yield these instruments generally become inoperative. Section E employed Instrument Configuration (1) shown in Figure 2-6. This configuration used only electrical resistance strain gages which have relatively large reliable strain capacities (>10,000 ?e). However, this gage type tends to drift over extended periods of time. For this reason, the data needed to determine mid-span effects during the applied load portion of the component tests was acquired using the instrumentation at this section. The Sections labeled C and H in Figure 2-5 employed Instrument Configuration (3) shown in Figure 2-8. These sections are located 200 mm (8 in.) towards mid-length of the component from the cross-frames N6L and N6R. The data acquired from these sections Each bending component was 47 during the applied load portion of the bending component tests was used to interpret the affect of the lateral bracing on the component. 2.6 Laboratory Equipment 2.6.1 Loading Apparatus For the bending component testing, the curved steel girder test frame was loaded from above with six load frames at the locations indicated on Figure 2-1. These frames reacted off the floor of the structural laboratory and consisted of five major components, which are identified in Figure 2-14 and described below: ? The Cross Beam was comprised of two 2438 mm (8 ft) long MC310 x 67 (MC12 x 45) ASTM A572M Grade 345 (A572 Grade 50) channels bolted together around a series of spacers with 22 mm (7/8 in.) diameter ASTM A325 high strength bolts. The spacers were 7 40 pipe. The channels were set back-to-back with the spacers between them. The bolts passed through the web of one anne el. near each end that allowed the attachment of the Brace Beams. 5 mm (3 in.) lengths of schedule ch l, then through the spacer and finally through the web of the other chann ? The End Beams were duplicates of the Cross Beam with additional bolt holes in the webs 48 End Beam Brace Beam Cross Beam Hydraulic Jack Dywidag Bar r strength thread-bars were used to attach each load assembly to the reaction floor. ? e by reacting off the loading fixture. These jacks had an 890 kN (100 ton) capacity and a 457+ mm (18+ in.) Figure 2-14: Typical Load Frame ? Approximately 1,372 mm (4 ft 6 in.) C250 x 22.8 (C10 x 15.3) ASTM A572M Grade 345 (A572 Grade 50) channels were used as braces and separators fo the End Beams. ? Four 25 mm (1 in.) diameter Dywidag Grade 1030 (Grade 150) high An Enerpac Model RR-10018 Heavy Duty Solid Plunger Double Acting Hydraulic Cylinder (jack) was used to load the test fram stroke. 49 The load frames were secured to the reaction floor at tie down locations that wer placed in a grid pattern at 914 mm (3 ft) centers. The four Dywidag bars of each load frame were connected to the floor tie downs at the corners of the 1829 mm (6 ft) north- south east-west square that was most centered on the load point. The bars extended from the floor to approximately 2438 mm (8 ft) above the top of the curved girder test frame. One End Beam was connected to each of the northern and southern pair of Dywidag bars at approximately 610 mm e (2 ft) above the top of the curved girder test frame. The bar el, The eastern and western ends of the End Beams were connected to a Brace Beam with 178 mm (7 in.) long L152 x 89 x 9.5 (L6 x 3? x 3/8) angles. Two 22 mm (7/8 in.) diameter A325 bolts connected one leg of the angle to the web of the End Beam through standard holes. Two additional 22 mm (7/8 in.) diameter A325 bolts connected the other leg of the angle to the web of the Brace Beam through slotted holes. The Cross Beam, with its weak axis in a vertical position, was then placed to span perpendicularly from one End Beam to the other over the load point on the curved girder test frame. The Cross Beam was connected to each of the End Beams with ?1219 mm (?4 ft) lengths of Dywidag thread-bars. At each of these connections, the Dywidag bar passed between the spaced webs of both the Cross Beam and the End Beam and was tensioned to securely hold the assembly together. Before incorporation into the load frame assembly, the base of the hydraulic jack was attached to the center of a 305 mm x 610 mm x 51 mm (1 ft x 2 ft x 2 in.) thick steel s passed through the spaced webs of the End Beams, which were held in place with anchor plates and nuts both above and below the beams. The End Beams were parall ran east-west and were 1829 mm (6 ft) apart. 50 plate. The Jack was then attached to the Cross Beam at the load point location with ?1219 mm (?4 ft) lengths of Dywidag thread-bars. These bars passed between the spaced web e e load point on the curved girder test 2.6.2 Instrumentation The instrumentation plan was devised to provide redundancy in both the acquisition of data and analysis techniques. The plan was comprised of nearly 800 individual instruments, the vast majority of which were uni-axial electrical resistance strain gages. 2.6.2.1 Electrical Resistance Strain Gages All electrical resistance strain gages used in this experimental program were manufactured by Measurements Group Incorporated and had an internal resistance of 120 ohms. Two types of electrical resistance strain gages were used: uni-axial or single-arm gages with a 6 mm (1/4 in.) gage length and rosettes with a 3 mm (1/8 in.) gage length. Uni-axial gages or single-arm gages measure strain in one direction along the longitudinal axis of the gage. Rosette gages incorporate three uni-axial gages whose longitudinal axes coincide at a single point but are each separated by an angle of 50 s of the Cross Beam and through pre-drilled holes in the 51 mm (2 in.) plate and wer tensioned to securely hold the assembly together. The Jack loaded the curved girder test frame through a machined ball and socket joint. The ball was attached to the hydraulic jack cylinder while the socket was attached to a load cell at th frame. All six hydraulic jacks were extended with a common pressure line. This line was fed by an Enerpac PEM-8418 Hi-Flow Hydraulic Pump capable of delivering up to 7.8 liters/minute (2 gallons/minute) at 68.9 MPa (10 ksi). 51 gradients (45 degrees). This configuration allowed the three individual strain reading be appropriately combin s to ed to determine the shear strain at that location. f sting of each bending component. 2.6.2.2 Vibrating Wire Strain Gages Vibrating wire strain gages use changes in the natural frequency of vibration of a wire stretched between two points to measure strain. As the wire?s length changes, the tension in the wire changes, which proportionally affects the wires natural frequency. The change in frequency can be mathematically equated to the change in length between the two points over which the wire is stretched. The gages used on this project were the Geokon models VK4100 that have a 51 mm (2 in.) gage length. 2.6.2.3 Load Cells Load cells are essentially scales capable of measuring load along one axis. They use a circuit of multiple uni-axis strain gages, called a bridge, to determine load. All load cells used have an internal resistance of 350 ohms and have two electrical bridges that were independently monitored during testing by the MicroMeasurement 5000 (MM5000) and the Hewlett-Packard VXI (HP) data acquisition systems that are described in Sections 2.6.3.2 and 2.6.3.4, respectively. StrainSert Model FL100U(C)-2DGKT Universal Flat Load Cells were used at each load point to determine the load applied to the test frame from the hydraulic rams. These Electrical resistance strain gages are very sensitive, have a large strain capacity and can be interrogated very quickly by a data acquisition system. However, they tend to drift over extended periods of time (days). Therefore, these gages were the primary source o data during the capacity te 52 load cells have a capacity of 445 kN (100 kip) and are capable of measuring load to within 56 N (12.5 lbs). StrainSert Model FL300U(C)-2DGKT Universal Flat Load Cells were used at each poi 2.6.3 Data Acquisition Systems Four data acquisition devices were required to support the instrumentation plan. As previously stated, this plan included more than 800 instruments and required redundancy in many of the measurements. Of particular importance was the requirement to be able to interpret the data in near-real-time to direct the course of each experiment. 2.6.3.1 MicroMeasurements 4000 The MicroMeasurements 4000 (MM4000) has a 200-channel capacity and was used to monitor the 176 resistance strain gages on the cross-frames and lateral bracing in the south bay of the test frame between G1 and G2. 2.6.3.2 MicroMeasurements 5000 The MicroMeasurements 5000 (MM5000) data acquisition system has an 80-channel capacity. This system was used to monitor the rosette resistance gages on G3 as well as the load cells at the abutment and at the hydraulic actuator locations. 2.6.3.3 Geokon Micro-10 The Geokon Micro-10 system has an 80-channel capacity and was used in combination with five Model 8032 Multiplexers to monitor all 79 vibrating strain gages nt of support to determine the vertical reaction of the test frame from all loads. These load cells have a capacity of 1,335 kN (300 kip) and are capable of measuring load to within 167 N (37.5 lbs). 53 used during each component test. This system was also used to monitor strains on the bending components as they were being installed. XI le disp se 2.6.3.4 Hewlett-Packard V The Hewlett-Packard VXI (HP) data acquisition system has a 640-channel capacity. It was the workhorse of these experiments?monitoring a minimum of 576 instruments during each test. This system was used to monitor a majority of the electrical resistance strain gages and the entire set of load cells, potentiometers, tiltmeters, linearly variab lacement transducers (LVDTs) and instrumented studs used during the bending component experiments. The HP system is capable of manipulating and displaying the acquired data in near-real-time (about 90 seconds from recording initiation for the experiments). 54 Chapter 55 3. Analysis of Experimental Data 3.1 Execution of the Experiments The test frame consisted of a three-girder bridge that was horizontally curved. Before any of the component testing began, the frame was erected with a prismatic outside girder (girder G3). This system was instrumented and elastically exercised over a period of months to prove the variety of instrumentation and data acquisition systems used. The test fram e nine locations, shown in Figure 3-1, to begin the component testing. Load cells were utilized to monitor and to record the shoring reaction loads. Screw jacks were used to adjust the elevation of the shores?increasing or decreasing the shoring load?to obtain a desired reaction. The shoring was used to eliminate as much of the dead load deflection from the structure as possible. The desired reactions were determined by constructing a finite element model shored at complimentary locations and by applying traction to simulate gravity. The results of the finite element analysis for the six girder abutment reactions and for the nine shoring reactions were used to establish a structural state that minimized the dead load effects within the test frame. This state will be referred to herein as the ?no- load? condition. e was shored at th 56 AL RAM EASU O F IN M R O NG ? G ED AL NG R= 2 0 8 ' - 9 " R = 2 0 0 ' - 0 " R = 1 9 1 ' - 3 " 1 '- 0 " T Y P . 1L C TI R E A C O N L 12 S P C ES 3L 4L A 2L 5L ME E C @ = 9 6L 7 ASUR D ROSS 7'-6" 90'-0" 0'-0" 4R 6 5R RDE R 2 ? IRD E G2 R GI G G R SP I NGAC 3 R R 2 C G D E R G IR D G 3 1 ' " T Y P . S O U T L G IR D R G 1 RO S S RA M E NE S 1R IR G 2 C E R -0 H B A Y C E C F L I N O R T H B A Y C E A C T I N 8 ' - 9 " 8 ' - 9 " R O L L L STR CTURA 100 LOAD U L W K CE P.) SHORE ITH LL (TY ition S pport LayoutFigure 3-1: No Load- Cond u Once the no-load condition was established, a bending component could be inserted into the outside girder (G3) of the test frame between the bolted field splices. After a bending component was bolted into G3, any outstanding instrumentation was applied, and all instruments were wired to one of the data acquisition systems. The shoring beneath the entire test frame and the component was then removed, and the dead load effects were captured using the data acquisition systems. This step, referred to as Shakedown-1 for each bending component test, was the first time the instrumentation supplied to the bending component was exercised over a significant range of strain. A complete set of data was acquired during Shakedown-1 in most of the bending component tests. However, individual pieces of instrumentation or the data acquisition systems occasionally did not perform as intended, and some data were corrupted or lost. These losses proved insignificant to the analysis of the results. After the shoring was removed, frames were erected that supplied the load to two locations on the top flange of each of the three girders. These frames were tied to the reaction floor of the laboratory using four high-strength steel rods. Double action hydraulic actuators that were connected to the frames supplied the load to the top flanges through a ball and socket joint. The joint acted on a load cell attached to the top flange at each load point. The load frames are described in detail in Section 2.6.1. If issues with the instrumentation or data acquisition systems arose during Shakedown-1, a series of loadings were applied to the entire test frame using the load frames. These proof tests were conducted repeatedly to exercise and prove the instrumentation and electronic equipment. These series of proof tests, referred to as 57 Shakedown-2, Shakedown-3 etc., were continued until all devices were working properly and as expected. 3.2 Data Analysis nalysis in this report focuses primarily on the strain data acquired from two instrum ions, labeled E and F in Figure 2-5, were located 203 mm (8 in.) from id-span of each bending component. The off he these instrumented cross-sections was necessary due to the local influences of the mid-span transverse stiffener present on six t even the vertical bending, horizontal bending and n dia his unif tion of the results. ith vibrating wire strain gages that had a long-term sta the data collected at t n, ulti-day process for the bending component installation, were used to determine the installation effects at mid-span. Cross-section E was instrumented com cal resistance strain gages. Because these gages are highly accurate over large ranges of strain, their data are used to determine the onditions at mid-span thr ch experiment. e propriately The a ented cross-sections. These cross-sect either side of the m set from t actual mid-span location for each of of he s bending components. However, torsio grams were all relatively constant throughout this range of the girder. T ormity allowed a collective interpreta Cross-section F was primarily instrumented w bility but a relatively small strain range. For this reason, his sectio during the usually m pletely with electri c oughout the applied-load portion of ea Analysis results included in this report for cross-sections other than E and F on the bending component are appropriately labeled. Four force actions cause normal strain, ? , in an I-girder cross-section: bending about the strong axis, bending about the weak axis, warping torsion and axial load. Using th Beam theory, the normal strains that result from these force actions are ap 58 combined at any point on the I-girder cross-section (shown in Figure 3-2) using Equation 3-1. EA P EC BiW EI xM EI yM z w n y y x x +++?=? Equation 3-1 Where: P z = Axial force in the z-direction E = Modulus of elasticity of steel A = Cross-sectional area of the I-girder M x = Moment about the x-axis y = Normal distance from the y-axis I x = Moment of inertia of the cross-section about the x-axis M y = Moment about the y-axis x = Normal distance from the x-axis I y = Moment of inertia of the cross-section about the y-axis C w = Warping constant Bi = W n = Normalized unit warping Bimoment 59 Y C.G. Z X Figure 3-2: I-Girder Coordinate System respective force action. The following equations utilize the magnitude of norma determine the complementary strains in the tension (bottom) flange tips. The aggregate normal strain distributions in the flanges can be separated using the thin-walled, open-section, Beam theory into each component of strain associated with a l strain in the compression (top) flange tips as a unit quantity that can be scaled as indicated to 60 ? ? ? B Out ? Out B,M B5 B6 B7 B1 B2 B3 B8 ? B In B4 ? B,M In W3 W6 W2 W5 W1 W4 Center of Curvature T5Out T,M T1 T7T6 T2 T3 T Out ? T8 T4 In T,M ? ? In T3 T (Typ.) Figure 3-3: Identification of Strain Measurement and Resultant Locations Equation 3-2 Equation 3-3 Equation 3-4 Equation 3-5 Where: zzyx PzMzMzMz out MT ,,,, . , ????? ?++?= zzyx PzMzMzMz in MT ,,,, . , ????? ????= zzyx PzMzMzMz out MB ,,,, . , ???????? ??+= zzyx PzMzMzMz in MB ,,,, . , ???????? ?+?= 61 62 ? ? ? ? ? ? ? ? ++ +? = fcNA ftNA tyD tyD 2 2 ? Equation 3-6 ? ? ? ? ? ? ? ? = fc ft b b ? Equation 3-7 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +++ +?? = fc ft fcSCNA ftSCNA b b tyyD tyyD 22 22 ? Equation 3-8 The location of these strain quantities on the cross-section of the girder is shown in Figure 3-3. The geometric characteristics are defined on Figure 3-4. Out ? B,M In ? B,M ? Out T,M Web mid-depth ? In T,M Neutral Axis Shear Center b ft t f t S C y y N A C.G. S.C. ' d D b fc f c t Figure 3-4: Cross-Sectional Parameters In the tests of the cross-sections that are doubly symmetric, the scalars defined in Equations 3-6 through 3-8 are approximately equal to 1.0, which reduces Equations 3-4 and 3-5 to the following: . ????? ??+= Equation 3-9 of the ain ending neutral axis sho in F n flange using the first term in Equation 3-1, then this magnitude can be scaled by ? oduce gradients of strain along the width of t lang fined in Figure 3-3, bec e thi s rmine the extreme fiber tension flange tip strains. ma is used to determine the normal strain due to warping. This term is presented using the Bimoment, Bi, so that it takes a familiar form. zzyx PzMzMzMzMB ,,,,, zzyx PzMzMzMz in MB ,,,, . , ????? ?+?= Equation 3-10 The resulting strain distribution from each described force action can be seen in Figure 3-5. Strong-axis bending produces a gradient of strain through the thickness flanges. At any location on the cross-section, the magnitude of strong axis bending str is proportional to the normal distance from that location to the b out wn igure 3-4. If this strain is determined for the extreme fiber tip of the compressio (Equation 3-6) to determine the extreme fiber tip strain in the tension flange. Weak-axis bending and torsional warping pr he f es. For all I-girders, the magnitude of weak-axis bending strain is proportional to the normal distance from the location of interest to the y-axis de aus s is an axis of symmetry for these section types. Weak-axis bending strain i determined by the second term in Equation 3-1. The extreme fiber compression flange tip strains are modified by ? (Equation 3-7) to dete The gnitude of flange tip torsional warping strain is proportional to the aggregate normal distances from the location of interest to both the y-axis and to the shear center of the section. The third term of Equation 3-1 63 The Bimom arping torsion ltiplied by the distance between flange centroids. The torsional warping stra in in the tension flange. h the fourth term in Equation 3-1. ent represents the magnitude of lateral flange bending due to w in each flange mu in at the extreme fiber tip in the compression flange is scaled by ? (Equation 3-8) to obtain the extreme fiber tip stra The axial load produces a uniform strain throughout the cross-section. The magnitude of this strain is determined wit 64 Z ? ? Z , Z ? Z , Z , P Z ? ? PZ Z P , P Z ? PZ ? ? M Z Z , M Z + ? ? Z , M ? ? ? Z Z , M ? Z M Z + ? Z Y -M Z ? , Z Y Y Y + ? ? Z , Z , M Y + Y , M ? ? M Y M ? + ? ? Z , M Z ? ? ? , M X Z ? X ? , ? ? Z + ? ? Z X X , M Z X , M -M XX B O Out T B ? In ? ut ? T ? In IA E N OR COMPRESSION TORSIONAL R G K AX DIN BE S RAIN IDENT O IS G NDI STRONG AXI NG AX L T NSIO WA PIN WEA BEN ST IFICATI N Fi ure 3 : Cog -5 mponents of Longitudinal Strain 3.3 Installation Strains The installation of each of the bending components into the test frame locked forces into the system through the completion of each bolted field splice and the insertion of the cross-frames at locations N6L and N6R. The strain effects from this erection were monitored at two sections on the bending component with vibrating wire strain gages. The following process, used to acquire these strains, was designed to minimize the amount of longitudinal warping strain and primary-axis bending strain present in the bending component prior to being installed into the test frame. 1. Block bending component at approximately 1/3 rd points while standing vertically. 2. Measure and record straight-line distance from inside of the flange tips at one end to inside of the flange tips at the other end. 3. Lay specimen on its side with blocking now provided at the ends and the 1/3 rd points. Adjust blocking to recreate flange distance measurements. 4. Apply vibrating wire gages at all accessible locations. Read and record all applied gages three times. Individual gage readings should not be consecutive, but should be the result of a circuitous reading procedure. 5. Return component to vertical position blocked again at 1/3 rd points. 6. Apply remaining vibrating wire gages. Read and record all gages, both those applied in this step and those applied previously, three times as stated above. Also, read and record all test frame instrumentation. 66 7. Bolt component into test frame. Read and record all operating instrumentation. 8. Bolt cross-frame N6L to the test frame and to the component. Read and record all operating instrumentation. 9. Bolt cross-frame N6R to the test frame and to the component. Read and record all operating instrumentation. The acquisition of the vibrating wire strain gage data during the installation of bending component B1 was accomplished using a vibrating wire gage readout box and a single gage reader. The reader was manually placed over one gage at a time, and the readout box indication was recorded by hand. After reviewing the data, it became apparent that the strain readings were very sensitive to operator technique. This sensitivity was confirmed by having three individuals independently produce the vibrating wire gage data with the bending component and test frame in a steady-state condition. While some of the cross-referenced strain indications were consistent, large groups of the data included at least one divergent reading. acquired with this acquisition sys Therefore, to increase the consistency and value of the installation strain data, the process of manual readings was replaced with automatic strain data collection using an acquisition system. Each vibrating wire gage was hardwired to a data acquisition system as the gage was installed on the bending component. The installation strain data for bending components B2, B3, B4, B5, B6 and B7 were tem. Unfortunately, in spite of the best efforts of the laboratory staff, most of the recorded data from the installation of components B2 and B3 was corrupted. 67 An analysis of the insta onents B4 through B7 instills high confidence in the data. Using the Beam theory analysis, detailed earlier in this Section, on independent subsets of the data produces the same group of equilibrated internal forces at the instrumented section. The results of the analysis on the installation strain data are summarized in Table 3-1 for these specimens. Normal strain (?e) from llation strains collected for the comp Specimen M x M y M z P z B4 257 22 82 -31 B5 172 4 236 1 B6 157 -24 12 3 B7 74 199 122 -29 Table 3-1: Installation Strain Data Analysis Results for Specimens B4, B5, B6 and B7 The installation strain analysis for component B4 shows that the vast majority of strain is the result of strong-axis bending. The analysis also indicates that a small axial force, 6 MPa (0.9 ksi), is also present in the component. However, the presence of this force is not supported by other test frame data. This apparent axial force is most likely the result of distortion in the web plate, which has a slenderness of 188.0 due to the section geometry that is singly symmetric. A review of the web data collected during installation supports this interpretation. However, the review was not definitive because information for only one face of the web was available. Figure 3-6 plots the B4 installation strain magnitudes onto their respective I-girder plate component. This figure is the first in a series used throughout this report to show the distribution of longitudinal strain along an I-girder cross-section. On these figures ind ividual longitudinal strains are plotted at the location where they were recorded using the scales attached to each plate of the cross-section. Then, a line representing the linear 68 regression result of the family of data from any one surface is also plotted using the s scales. These linear regression lines essentially indicate the distribution of longitudinal strain along each plate and project a plate tip strain. ame from the e f the web are indicated with a shaded square. Returning to Figure 3-6, the regression line for the web data shown crosses the web at the ) Flange strains are indicated with triangles. Triangles that point up show data top of the plate. Triangles that point down show data from the bottom of the plate. Th shaded triangles indicate that the data is from the outside of the plate at the location o extreme fiber for strong-axis bending. The open triangles indicate that the data is from the inside surface of the plate i.e. top of the bottom flange or bottom of the top flange. Web strains on the inside of the web, the face closest to the center of curvature, are indicated with an open diamond. Web strains on the outside face of the approximate location of the bending neutral axis. However, its fit to the individual strain data is poor, which supports the hypothesis of web flexing as the cause of the apparent axial force. Also, while the data for the top and bottom of the compression (top flange indicate similar trends, the tension (bottom) flange data reveal a slight localized bending on the outside of the plate by the intersection of the regression lines. 69 Center of Curvature B4 Section F Strains - 4 0 0 -200 0 2 0 0 400 -600 -400 -200 20 400 0 0 Installation -400 00-2 0 200 400 600 Figure 3-6: B4 Installation Strain Data ajority the cross-frames between B5 and G2. The remainder of the installation stra of the component suspended between supports. The installation strain analysis for doubly symmetric B5 reveals that a slight m of the installation strain resulted from torsion in the component. This torsion was caused by the insertion of ins were caused by strong-axis bending due to the bolted field splices and to the dead load Figure 3-7 shows the linear behavior of the B5 installation strains. The flange strain gradients, which trend oppositely in the constructed figure, indicate a large torsional warping component in the strain data. 70 Center of Curvature -400 -200 0 200 400 -600 -400 -200 0 200 400 B5 Section F Installation Strains -400 -200 0 200 400 600 Figure 3-7: B5 Installation Strain Data The in tion of the cross-frames was insignificant on this component. The strain from installation can be attributed almost entirely to the effect of the bolted field splices and to the vertical bending due to dead load. Figure 3-8 shows the near uniform strain across both flanges that supports the analysis. stallation strain analysis for doubly symmetric B6 shows that the inser 71 Center of Curvature -4 00 -2 00 0 20 0 40 0 -600 -400 -200 0 200 400 B6 Section F Installation Strains -400 -200 0 200 400 600 Figure 3-8: B6 Installation Strain Data l 7 is also singly symmetric. While the strain data that s did com cross-frames between B7 and G2. The figure indicates that the weak-axis bending and Simi ar to B4, bending component B were acquired during installation are held in high confidence, the data analysi not produce an ideal strain distribution and resulted in an apparent small axial stress acting on the cross-section, 6 MPa (0.9 ksi). However, this result is most likely due to the fabrication process used to create B7 that is described in Section 2.3.1.3. Figure 3-9 shows the installation strains and associated regression lines for ponent B7. While the overall installation had little effect on the web and bottom (tension) flange, the top (compression) flange was influenced by the insertion of the 72 warping components of normal strain are of similar magnitude because they nega other in the tension flange and combined to produce a significant strain gradient in the ted each compression flange. This graphic evidence supports the data analysis. B7 Section F Strains Center of Curvature - 400 - 200 20 0 40 0 0 -600 -400 -200 0 400 200 Installation -400 -200 0 200 400 600 Figure 3-9: B7 Installation Strain Data Because the installation strain data for B1 are considered suspect and the data f and B3 were largely corrupted, an estimate of the installation strain levels for these components was made using the data from B5 and B6. The data from B4 were slightly affected by the single axis symmetric of the section; therefore, they were excluded from this estimate. The data from B7 were influenced by the fabrication process employed or B2 with this component and were also excluded from this estimate. 73 To create the model of the estimated installation strain levels for B1, B2 and B3, the strain data analyses for B5 and B6 were used to determine the moments about each a that resulted from the installation process. These moments were averaged, and the averages we xis re analyzed for their effects on sections B1, B2 and B3. The results of this ope e ration are the sets of strain listed in Table 3-2 for components B1, B2 and B3. Thes strains are contrasted with the actual installation strain data for components B4 through B7 also in Table 3-2. These estimated installation strain levels were used to analyze the experimental data of B1, B2 and B3. Bending Specimen B1* B2* B3* B4 B5 B6 B7 Strain Location Installation Strain (?e) Gage T1 -118 -110 -110 -136 -4 -168 183 T2 -182 -175 -174 -197 -106 -167 38 T3 -247 -240 -238 -247 -264 -166 -128 T4 -311 -304 -302 -280 -350 -150 -273 T5 -112 -104 -104 -153 25 -162 213 T8 -304 -298 -296 -322 -349 -144 -297 W4 -105 -102 -102 -143 -50 -97 -5 W5 -2 -2 -2 -186 -21 34 -11 W6 100 97 97 57 106 79 16 B1 85 78 78 191 11 132 141 B4 321 314 313 144 351 166 82 B5 92 85 84 170 -21 114 88 B6 170 163 162 176 137 138 71 B7 249 242 241 202 208 180 65 B8 327 321 319 239 332 185 102 *Strain levels estimated using B5 and B6 data. Table 3-2: Installation Strain Data Used in Bending Component Capacity Analysis Figure 3-10 shows the regression lines that are the result of the estimated installation strain levels and the suspect installation strain data from B1. The estimated levels primarily indicate vertical bending and warping in the girder flanges and bound most of the suspect data. 74 Figure 3-11 shows the effect s ponent B2 Figure 3-12 shows the effects of the estimated installation strain levels on component B nd the that we rmin liabl m the actual f B3. The ac l data ce ag uat und e e e, n fidence in the estimation procedure. s of the e timated installation strain levels on com . 3 a data re dete ed re e fro installation o tua are on ain adeq ely bo by th stimat instilli g con Center of Curvature -400 - 2 0 0 0 200 400 -600 0 0 0 0 0 -40 -20 20 40 B1 Section F In n St stallatio rains -400 0 200 400 600 -200 Figure 3-10: B1 Installation Strain Data with Regression Line Estimates 75 76 Center of Curvature - 4 0 0 - 2 0 0 0 200 400 -60 -40 0 0 -200 0 20 40 0 0 B2 Section F Installation Strains Estimates -400 -200 0 0 200 40 600 Figure 1: m ssion Line Estim 3-1 B2 Installation Strain Model Fro Regre ates Center of Curvature -400 -200 0 200 400 -600 -400 -200 0 200 400 B3 Section F Installation Strains -400 -200 0 200 400 600 3.4 Bending Component B1 Test Figure 3-12: B3 Installation Strain Data With Regression Line Estimates The test frame containing bending component B1 was loaded in 28 steps to a maximum applied load of 1,354 kN (304.3 kip). As indicated in Table 3-3, the majority of these steps represent approximately 27 kN (6 kip) increments in applied load. Once the system became non-linear, both load increment and displacement increment were monitored in an effort to capture the peak resistance of each bending component. The component behavior analyses in this report utilize the steel plate specific yield criteria established from material testing and reported in Appendix A. That is, each plate 77 of a nt to l 1 and G2, and then subtracting them from the total. Wh n the p ben his table shows that the ratio of ver moment to calculated vertical yield moment, M x yield ,of 0.69, and during the maximum n I-girder cross-section has an associated yield strength determined through experimentation, which is used to interpret the behavior and performance of that plate. Vertical bending moments at mid-span of the component are calculated by two methods in the elastic range; the direct method and the indirect method. The direct method converts the individual strain readings recorded at mid-span of the compone a moment using the Beam theory describe earlier in this Chapter. The indirect method considers a free body of half the test frame between mid-span and one of the abutments. Using the applied loads and end reactions a mid-span vertica bending moment can be determined for the entire test frame. This moment can then be reduced to a component mid-span moment by employing the Beam theory to solve for the vertical bending moments in both G ile the indirect method is proven by and is redundant to the direct method in the elastic range, it is the sole method of determining the component mid-span moment i inelastic range. First yield in B1 occurred at the inside tip of the compression flange during load ste 8 at a total applied load of 826 kN (185.6 kip). At the step 8 load level, the vertical ding moment resisted by B1 was determined to be 3,513 kN-m (2,591.0 k-ft) using the direct method of calculation and 3,516 kN-m (2,593.0 k-ft) using the indirect method of calculation. Table 3-4 contains a summary of the B1 mid-span stresses and the moments that are a result of the strain data analysis. T tical flange bending stress to lateral flange bending stress was between 0.46 and 0.47 throughout the elastic load range. Also, first yield occurred at a ratio of vertical bending 78 sustained applied load this ratio rose to 0.90. M x yield is calculated using the yield strength of the compression flange and is the strong-axis bending moment required to cause yielding at the extreme fiber of the compression flange without consideration for Figure 3-13 shows a comparison of the resisted vertical bending moment for each method of calculation, direct and indirect, throughout the elastic range of loading. The purpose of this figure is to establish the accuracy of the indirect method of calculation in determining the vertical bending moment being resisted by the component. The direct method relies on the principles of the Beam theory. Therefore, at load levels that cause the component to exceed its yield strength or distort significantly out of plane this method of determining the resisted vertical bending moment no longer applies. Accordingly the indirect method is relied upon in the non-linear region of component behavior. instability. 79 Load Total Applied Mx (Total) Mx (G1) Mx (G2) Mx (B1) Step Load Indirect Direct (a) (b) (a)/(b) KN kN-m kN-m kN-m kN-m kN-m B1 Elastic 1 0.0 -1.0 0.4 -0.2 -1.1 -2.6 0.44 2 63.8 242.9 24.8 88.2 129.9 116.5 1.11 3 187.8 759.1 52.4 293.1 413.6 397.6 1.04 4 329.7 1379.3 84.2 53 .3 756.8 735.8 1.03 8 5 459.8 1953.0 115.0 773.6 1064.4 1050.8 1.01 6 650.0 2798.1 158.1 1103.8 1536.3 1506.9 1.02 7 802.7 3481.2 1 4.2 1888.9 1.01 87.7 1379.4 191 8 825.6 3582.1 190.8 1434.2 1957.1 1954.4 1.00 B1 Plastic 9 844.5 3666.6 193.9 1468.9 2003.7 2004.9 1.00 10 878.1 3816.3 198.6 1537.0 2080.7 2116.2 0.98 11 900.0 3913.7 200.3 1582.9 2130.4 2201.0 0.97 12 923.8 4023.4 198.9 1633.8 2190.8 13 957.0 4168.9 200.3 1703.2 2265.4 14 982.6 4283.9 195.1 1764.2 2324.6 15 1012.3 4415.9 193.7 1834.0 2388.2 16 1035.5 4518.0 188.6 1894.7 2434.6 17 1068.9 4668.2 192.1 1961.3 2514.8 18 1094.2 4780.0 187.3 2018.8 2573.9 19 1119.0 4893.7 185.4 2086.6 2621.6 20 1139.7 4988.2 183.4 2145.2 2659.6 21 1166.0 5106.3 177.1 2216.1 2713.1 22 1197.5 5245.8 168.1 2308.7 2768.9 23 1216.4 5314.1 155.2 2369.0 2789.9 24 1248.3 5452.1 150.0 2457.9 2844.2 25 1265.8 5528.1 140.1 2517.3 2870.6 26 1296.8 5661.1 123.3 2631.9 2905.9 27 1329.4 5803.4 96.9 2759.7 2946.9 28 1353.5 5910.4 79.3 2850.9 2980.3 29 1344.6 5860.0 8.2 3026.0 2825.8 Table 3-3: B1 Applied Load Steps and Resulting Girder Moments 80 Load otal Co pressi T m on Flange, Inside Tip, Extreme Fiber Stress Moments at Section Case A plied ? ? z p z ? z ? z ? z ? z (lat.) M x M x M y Bi M lat. oad To l from FrL ta om from from Direct Indirect Comp. M x M y M z P z Flange (b) (b)/(a) (c) (c)/M x yield (a) N M MPa Mk Pa Pa MPa MPa MPa kN-m kN-m kN-m kN-m 2 kN-m Elastic Instal -69. 7 43.24 2l. 9 - . 9.06 -0.52 -26.20 0.61 536.8 -3.7 45.8 16.8 86 -2 DL . - .06 9.63 4.11 -31.68 0.38 1022.1 2.6 46.6 20.3 -109 90 82.33 -2 -2 In +D . -1 .80 8.69 3.59 -57.88 0.46 1559.0 -1.0 92.4 37.0 stall. L -179 87 25.57 0 -5 (1 .0 -179 66 25.36 0) 0 . -1 .86 8.73 3.58 -57.87 0.46 1556.4 1557.8 -1.1 92.5 37.0 0.31 -5 (2 3.8 -193 78 34.96 -0) 6 . -1 .10 2.26 3.54 -62.36 0.46 1675.5 1688.9 0.1 98.0 39.9 0.33 -6 (3 7.8 -226 50 57.60 -1) 18 . -1 .82 0.68 3.59 -72.49 0.46 1956.5 1972.6 2.3 111.3 46.3 0.39 -7 (4 9.7 -265 90 84.84 -3) 32 . -1 .84 0.91 3.69 -84.75 0.46 2294.7 2315.8 4.9 127.4 54.2 0.46 -8 (5 9.8 -302 76 10.21 -5) 45 . -2 .71 0.64 3.79 -96.34 0.46 2609.8 2623.4 7.3 142.7 61.6 0.52 -9 (6) 0. -356 4 46.9 -865 0 .7 -2 5 .9 04.75 3.96 -113.74 0.46 3065.9 3095.3 11.5 164.9 72.7 0.61 9 -1 (7) 2. -403 5 77.7 -180 7 .3 -2 2 2.54 17.10 4.00 -129.64 0.47 3447.8 3473.2 16.0 184.3 82.9 0.68 -1 (8) 5. -411 2 83.0 -182 6 .8 -2 0 3.47 19.61 4.27 -133.09 0.47 3513.4 3516.1 17.2 188.3 85.1 0.69 -1 Plastic (9) 4. -419 9 87.0 -184 5 .2 -2 6 4.58 21.79 4.15 -136.37 0.48 3563.9 3562.7 18.7 191.7 87.2 0.70 -1 (10) 8. -441 0 96.0 -187 1 .2 -2 3 9.25 28.76 2.84 -148.01 0.50 3675.2 3639.7 24.6 202.7 94.6 0.72 -1 . . . . . . . . . . . . (28) 1353.5 4539.2 0.90 le 3-4: B1 Mid-Span Stresses and Moments Tab B1 Vertical Bending Moment (Mx) 0.0 500.0 1000.0 1500.0 Total Applied Load (kN) o me 2000.0 25 3000.0 4000.0 0.0 200.0 400.0 600.0 800.0 1000.0 M n t ( k N - m) 3500.0 00.0 Direct Indirect ending Moment Figure 3-13: B1 Vertical B Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m 0 1000 2000 3000 4000 5000 6000 G1 Test G2 Test B1 Test Figure 3-14: Test Frame Mid-Span Vertical Bending Moments, B1 Test ) 82 Figure 3-14 compares the mid-span vertical bending moments carried by B1, G2 and G1 due to the applied loading. The maximum sustained vertical bending moment in B1 was 4,539 kN-m (3,347.5 k-ft) and occurred at load step 28. Failure of B1 occurred during the displacement increase associated with load step 29. Failure is defined as the point at which a decrease in the component mid-span vertical bending resistance is associated with an increase in either the total load sustained by the test frame or the vertical displacement of the test frame. As the result of yielding and/or local compression flange buckling, the point of failure is generally coupled with dramatic load shedding from the component to G2. This is the condition illustrated by the last points (load step 29) of the B1 and G2 plots in Figure 3-14. At this load step, G2 is resisting more applied vertical bending moment than B1. The effects of installation and dead load on the mid-span of B1 can be seen in Figure 3-15. The seemingly complementary strain gradients in the flanges indicate that the primary cause of longitudinal strain is strong-axis bending and warping. If a significant weak-axis bending moment was present its effect would increase the gradient of strain across the co nge. The mid-span longitudinal strain state at first yield in B1, load step 8, is shown in Figure 3-16. In addition to the longitudinal strains plotted on each plate as in previous figures, this figure and those in the subsequent sections also show the individual steel plate yield strain limits with dashed lines labeled ? y . Returning to Figure 3-16, despite the slight separation of the regression lines at the inside tip of the compression flange and at the top of the web, the section is essentially mpression flange and decrease this gradient across the tension fla 83 behaving linearly elastically. This deduction is proven by the ratio of the direct to indirect calculation of resisted vertical moment, see Figure 3-13 and Table 3-4. Center of B1 Section E Step 1 Curvature -2000 -1000 0 00 00 10 20 -5000 -4000 -3000 -2000 -1000 0 -? y ? y 0 2000 4000 1000 3000 5000 -? y ? y B1 Mid-Span Longitudinal Strain State Resulting From Installations and Dead Load (Step 1) Figure 3-15: 84 Center of Curvature -2000 -1000 0 10 00 20 00 -5000 -4000 -3000 -2000 -1000 0 B1 Section E Step 8 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-16: B1 Mid-Span Longitudinal Strain State During Step 8 The longitudinal strain state at the more critical cross-frame section for the B1 test at first yield (step 8) is shown in Figure 3-17. While this plot does not include the effects of installing the bending component on the cross-section, the most critical flange tip is more than 500 ?e away from its yield limit supporting the assertion that first yield in this component occurred at mid-span. At this cross-section, the flange strain gradients trend opposite to those for the mid-span cross-section because the lateral bending effect in the flange due to warping has gone through the expected inflection near the brace point. 85 Center of Curvature -5000 0 0 -2000 000 0 -400 -300 -1 B1 Section C Step 8 ? y -? y 0 000 000 000 000 000 1 2 3 4 5 Figure 3-17: dinal tate Nea Fram During tep 8 (Excluding Installation Effects) d step the m n of shown in Figure 3-18. At this load level, the inside compre lange expe ng t thic ieldin . Al , first yield in the tension flange has been reached at the inside tip. The separation of the regression lines at the in of th ression flange the th web ind ates the presence of local plate bending or, perhaps, the onset of buckling. Longitu Strain S in B1 r Cross- e N6L S Loa 11 for id-spa B1 is ssion f tip is rienci hrough kness y g so side tip e comp and at top of e ic 86 87 Cent Curvature er of - 2 0 0 0 0 0 0 0 - 1 0 0 10 0 20 0 -5000 -3 -2000 -4000 000 -1000 0 B1 Section E 1Step 1 ? y -? y 0 3000 10 20 00 00 40 50 00 00 Figure 3-18: B1 Mid-Span Longitudinal Strain State During Step 11 Mid-span of B1 at load 9. is sustained load, ro r tension flange have excee their y th e tip of the compress nge that w owever, the While the strain gradient across the tension flange has increased slightly through the sion of loading th oint, the gradient of strain across the compprog web strains are now indicating app res ded xim ion -? y ? y step 1 preately half of the com fla ield stren to gt a hs. s fi is p Th rst the distortions consistent with racking of the flanges. e ob 8 i ssi loc se s s on al rve ho fl wn ang pla d a te t load step 8 has increased. H in e Fi and bend gu a ing re qu 3-1 arte at e in A of t th the sid ression flange is nearly four times what it was across the tension flange at this load step. This amplification is the result of the increase lateral bending of the compression flange due to the P-delta effects of the horizontally curved flange. Center of Curvature -2000 -1000 0 20 000 0 10 -5000 -4000 -3000 -2000 -1000 0 B1 Section E Step 18 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-19: B1 Mid-Span Longitudinal Strain State During Step 18 The effects of the maximum sustained load during the B1 test are shown in Figure 3- 20. The regression lines for the top flange data have been replaced with simple linear links. When the strain data across any surface of a plate becomes non-linear due to excessive yielding or buckling the regression line for that particular data set is replaced 88 with simple linear links. Shaded symbols are connected with a solid gray line while open symbols are connected with a dashed black line. Returning to Figure 3-20, the maximum sustained load during the B1 test has caused through thickness yielding over approximately 5/8 of the compression flange and over half of the tension flange. The compression flange and web have buckled significantly as evidenced by the grossly disparate regression lines. Center of Curvature -2000 -1000 0 10 00 20 00 -5000 -4000 -3000 -2000 -1000 0 B1 Section E Step 28 (Max. Load) ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-20: B1 Mid-Span Longitudinal Strain State During Step 28 89 Figure 3- an longitudinal strains of G2. At this load step, G2 is resisting a majority of the applied moment, and B1 has failed. While the figure does not include any effects for installation of the B1 into the test frame, the applied load effects are far enough from the indicated yield limits to ensure elastic behavior. G2 and G1 as well as all cross-frame members were continuously monitored during each test to ensure they remained elastic as the bending component exceeded this limit. 21 shows the effects of the applied loads at step 29 on the mid-sp Center of Curvature -2 000 -1 000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B1-G2 Step 29 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-21: Most Critical G2 Mid-Span Longitudinal Strain State B1 Test (Step 29) 90 3.5 Bending Component B2 Test The test frame that contains bending component B2 was loaded to a maximum of 1,434 kN (322.4 kip) in 33 steps. The applied load levels for each step and the associa vertical bending resistance for each girder element are listed in Table 3-5. Table 3-6 contains the mid-spa ted n stresses and moments experienced by B2 throughout the elastic range of loading. When yield was first reached in the bending component at load step 10, the normalized vertical bending strength ratio was 0.67. Also, for the com comparison of the direct versus indirect methods of determining the vertical bending moment at mid-span of B2 is shown in Figure 3-22. The plot indicates good agreement between the two methods for determining the vertical bending resistance of B2. At first yield in B2, load step 10, the ratio of indirect to direct resistance is 0.98 (see Table 3-5). Figure 3-23 shows the vertical bending moments at mid-span of each of the three girders of the test frame throughout the B2 test. The test progressed until G2 carried a greater percentage of the applied load than B2. The installation and dead load effects on the longitudinal strain state at mid-span of B2 are shown on Figure 3-24. Recall that the installation strain data used in this analysis were derived from the B5 and B6 tests. The complementary gradients of strain in the flanges indicate that these effects are dominated by strong-axis bending and warping. The pression flange, the ratio of lateral bending stress to vertical bending stress ranged from 0.50 to 0.52 in this regime. A maximum vertical bending moment of 4,730 kN-m (3,487.9 k-ft) corresponding to a normalized ratio of 0.90 was sustained by B2 during step 33. A 91 web data are consistent and linear indicating a lack of plate flexing at this initial load level. 92 Load Total Applied Mx (Total) Mx (G1) Mx (G2) Mx (B2) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m B2 Elastic 1 0.0 -0.4 0.0 -0.4 0.0 0.6 -0.05 2 26.1 111.4 8.1 37.9 65.4 57.3 1.14 3 137.5 602.7 35.3 206.2 361.2 314.9 1.15 4 274.8 1204.6 70.6 451.6 682.4 643.2 1.06 5 404.7 1779.1 97.2 656.0 1025.9 957.4 1.07 6 535.5 2363.2 122.8 873.7 1366.7 1279.2 1.07 7 664.1 2937.2 150.4 1149.0 1637.7 1626.4 1.01 8 794.5 3510.4 160.8 1406.0 1943.6 2008.4 0.97 9 826.7 3651.9 165.4 1472.0 2014.6 1979.6 1.02 10 852.8 3767.4 169.6 1526.4 2071.3 2103.1 0.98 B2 Plastic 11 874.0 3858.2 170.3 1572.9 2115.0 2179.5 0.97 12 907.8 4009.8 176.0 1630.2 2203.6 2251.5 0.98 13 938.5 4145.0 178.9 1690.5 2275.6 2353.1 0.97 14 963.7 4254.1 179.5 1740.9 2333.7 15 983.0 4341.0 178.0 1789.5 2373.5 16 1015.6 4485.6 180.7 1849.7 2455.2 17 1040.9 4599.1 184.3 1905.5 2509.3 18 1071.1 4732.4 186.2 1967.0 2579.2 19 1090.9 4817.4 184.6 2015.1 2617.7 20 1112.8 4909.6 177.1 2065.4 2667.1 21 1143.3 5049.6 178.9 2129.7 2741.1 22 1167.4 5153.9 178.3 2190.2 2785.4 23 1199.9 5301.9 177.5 2255.0 2869.4 24 1223.2 5405.1 173.6 2321.7 2909.8 25 1251.6 5531.8 172.1 2388.2 2971.5 26 1280.0 5660.0 168.5 2463.6 3028.0 27 1306.5 5777.6 163.9 2528.3 3085.4 28 1331.3 5884.8 154.4 2603.1 3127.3 29 1358.1 6001.4 143.1 2683.5 3174.7 30 1382.5 6110.3 131.5 2763.5 3215.3 31 1410.8 6223.7 113.7 2855.9 3254.1 32 1417.9 6256.3 94.8 2911.2 3250.3 33 1434.1 6327.1 80.9 2981.5 3264.7 34 1423.8 6277.7 50.9 3050.9 3176.0 35 1392.4 6130.9 23.5 3042.5 3064.9 36 1384.7 6095.6 -6.8 3115.1 2987.2 37 1349.3 5935.6 -43.7 3099.7 2879.7 Table 3-5: B2 Applied Load Steps and Resulting Girder Moments 93 Load Total Compression Flange, Inside Tip, Extreme Fiber Stress o s ctiM ment at Se on Case Applied ? ? ? ? ? ? (lat.) x x M lat. z z z z z z M M y Bi M Load Total fr ct direct mom from from from Dire In Co p. M x M y M z P z Flange (a) (b) (b)/(a) ) (c yiel (c )/M x d kN MPa M a m N k 2 - Pa MPa MPa MPa MP kN-m kN- k -m N-m kN m Elastic Install. -68.64 -41.81 2.88 -29.23 -0.48 -26.35 0.63 536.8 -3 .7 .7 45.8 16 DL -72. -31.53 0.44 .1 4. .0 -100.96 29 -3.55 -27.98 2.86 928 5 43.8 20 Install.+DL -169.60 -11 88 .9 0. .84.10 -0.67 -57.21 2.38 -57. 0.51 1464 8 89.6 36 (1) 0.0 -169.60 -11 90 0.51 .5 4. 0. .7 .84.14 -0.59 -57.31 2.44 -57. 1465 146 9 7 89 36 0.28 (2) 26.1 -176.09 -118.56 -1.09 -58.96 2.53 -60.05 0.51 1522.2 0. 1. .3 .2153 3 4 92 38 0.29 (3) 137.5 -205.88 -138.63 -2.83 -66.84 2.42 -69.67 0.50 .8 1826. 3. 6 .31779 1 6 104. 44 0.35 (4) 274.8 -243.54 -16 76 .50 .2 2147. 6. 5 .04.20 -4.79 -76.97 2.42 -81. 0 2108 3 1 120. 52 0.41 (5) 404.7 -279.74 -188.67 -6.67 -86.84 2.43 -93.50 0.50 .3 2490. 8. 9 .4 2422 9 5 135. 59 0.47 (6) 535.5 -317.23 .74 -8.85 -97.18 2.54 -106 0.50 4.1 2831. 1 1 .4 -213 .03 274 6 1.2 152. 67 0.54 (7) 664.1 -359.61 .78 -11.29 -110.14 2.61 -121 0.50 1.3 3102. 14 -240 .43 309 6 .4 172.4 77.2 0.59 (8) 794.5 -407.85 -270.53 -15.61 -124.98 3.27 -140.59 0.52 .3 3408. 19 3473 5 .8 195.6 89.3 0.65 (9) 826.7 -404.06 -26 . 0.52 .5 3479. 19 8.29 -15.22 -124.09 3.53 -139 31 3444 5 .3 194.2 88.5 0.66 (10) 852.8 -419.90 -277.91 -16.95 -128.54 3.51 -145.49 0.52 .0 3536. 21 3568 2 .6 201.2 92.5 0.67 Plastic (11) 874.0 -430.12 -28 149.75 .53 3644.4 3579. 23 3.86 -18.13 -131.62 3.49 - 0 9 .0 206.0 95.2 0.68 (12) 907.8 -441.56 -28 . 3716.5 3668. 25 9.47 -20.05 -135.23 3.19 -155 27 0.54 6 .5 211.7 98.7 0.70 . . . . . . . . . . . . 4729. 6 0.90(33) 1434.1 Table 3-6: B2 Mid-Span Stresses and Moments B2 Vertical B ng M nt (M 0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0 3500 000.0 0.0 200.0 400.0 600.0 800.0 1000.0 Total Applied Load (kN) M o me n t ( k N - m) endi ome x) 4 .0 Direct Indirect Figure 3-22: B2 Vertical Bending Moment in Elastic Range Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m ) 0 1000 2000 3000 4000 5000 6000 G1 Test G2 Test B2 Test Figure 3-23: Test Frame Mid-Span Vertical Bending Moments, B2 Test 95 Center o urvatur f C e -2 - 1 0000 0 0 0 1 000 0 0 2 0 -5000 -4000 00 00 -1000 0 -30 -20 B2 Section E Step 1 ? y -? y 0 00 00 3000 00 00 10 20 40 50 -? y ? y Figure 3-24: B2 Mid-Span Longitudina in Sta lting F nstallatio and Dead oad Step 1 ield B2 te urred e inside compression flange tip at mid-span of the component during load step 10. The longitu rain the m -span cro - section at in the tension (bottom) flange compared with the compression (top) flange indicates that there is a significant weak-axis bending effect at mid-span of B2 at this load level. The regression lines fit the data well, which is representative of linear-elastic behavior. l Stra te Resu rom I n L ( ) First y in the st occ at th dinal st state of id ss step 10 can be seen in Figure 3-25. The slightly flatter strain gradient 96 97 C C enter urva of tu re -2 0 0 0 0 0 0 -1 0 0 0 0 1 0 2 0 0 -5000 -2000 -4 -3 000 000 -1000 0 B2 Section E Step 10 ? y -? y 0 1000 4000 2 3 000 000 5000 -? y ? y Figure 3- St ing Step 10 Th ost critical b n nted section adjacent to e outside tension flange tip is still more than 500 ?e from its yiel id-span of B2 s test. 25: B2 Mid-Span Longitudinal Strain ate Dur e m raced section of B2 at step 10, the i strume cross-fram included in this figure, th e N6L, is shown in Figure 3-26. Although the effects of installation are not d limit. This result supports the conclusion that first yield occurred at m during thi Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B2 Section C Step 10 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-26: Longitudinal Strain State in B2 Near Cross-Frame N6L During Step 10 (Excluding Installation Effects) Figure 3-27 depicts the longitudinal strain state at mid-span of B2 when the tension flange also reaches its yield limit. At this point, the inside tip of the compression flange is experiencing through-thickness yielding and the regression lines of the compression flange are starting to slightly separate. This separation indicates that the local plate bending or buckling has initiated. 98 Center of Curvature -2000 -1000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B2 Section E Step 13 -? y ? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-27: B2 Mid-Span Longitudinal Strain State During Step 13 At step 22 of the B2 test, the outside tip of the tension flange at cross-frame N6L and the outside tips of both flanges of the cross-section at cross-frame N6R have reached their yield limits as can be seen in Figures 3-28 and 3-29 respectively. At load step 27, the cross-sections adjacent to N6L and N6R were experiencing yielding in all outside flange tips. 99 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B2 Section C Step 22 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-28: Longitudinal Strain State in B2 Near Cross-Frame N6L During Step 22 (Excluding Installation Effects) 100 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B2 Section C Step 22 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-29: Longitudinal Strain State in B2 Near Cross-Frame N6R During Step 22 (Excluding Installation Effects) The longitudinal strain state of mid-span B2 during the maximum sustained moment of the test, step 33, is illustrated in F ure shows that approximately 5/8 of the compression flange and ? of the tension flange had yielded at this load level. The separations of the compression flange and web data regression lines indicate local bending and buckling of these plates. igure 3-30. The fig 101 Center of Curvature -2 000 -1 000 0 1 000 2 000 -5000 -4000 -3000 -2000 -1000 0 B2 Section E Step 33 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-30: B2 Mid-Span Longitudinal Strain State During Step 33 Figure 3-31 illustrates the strain state of the mid-span of G2 at the maximum load that this girder sustained during the B2 test. The data reveal linear elastic behavior well below the yield limit in all three plates of the cross-section. 102 Center of Curvature -200 0 -100 0 0 100 0 200 0 -5000 -4000 -3000 -2000 -1000 0 B2-G2 Step 36 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-31: Most Critical G2 Mid-Span Longitudinal Strain State During B2 Test (Step 36) 3.6 Bending Component B3 Test The test frame containing component B3 was loaded in 45 steps to a maximum represent approximately 27 kN (6 kip) increases in applied load. From step 31 to the end of the test, the experiment was conducted in displacement control. The maximum applied vertical bending moment sustained by B3, 3,375 kN-m (2,489.2 k-ft), occurred during applied load of 1,504 kN (338.1 kip). From step 8 to step 31, these load step increments 103 load step 44. Table 3-7 and Table 3-8 contain these results along with other selected information regarding the B3 test. Load Total Applied Mx (Total) Mx (G1) Mx (G2) Mx (B3) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m B3 Elastic 1 0 -0.7 -0.1 0.4 -1 0.2 -5.4 2 56.4 240.9 14.2 81.7 144.9 126.9 1.14 3 148.9 651.2 40.4 231.4 379.4 338.4 1.12 4 276.5 1219.2 70.3 451.8 697.1 644.6 1.08 5 406.5 1793.6 96.9 674.8 1021.9 962.6 1.06 6 536 2362.5 119.6 901 1341.8 1283.3 1.05 7 664.9 2931.3 141.9 1135.5 1654 1604.4 1.03 8 802.3 3545.4 172.2 1373.7 1999.5 1936.9 1.03 9 826 3650.1 178.8 1419.1 2052.2 1998.5 1.03 10 852.7 3766.8 178 1469.1 2119.8 2075.8 1.02 B3 Plastic 11 872.2 3850 180.7 1511.3 2158.1 2137.9 1.01 12 906.6 4005.6 189.6 1569.7 2246.3 2229.9 1.01 13 934.8 4129.4 193.6 1625.9 2309.9 14 960.4 4239.7 193.1 1686.1 2360.5 15 984.3 4347.6 190 1737.8 2419.8 16 1012.9 4474 194.3 1792.5 2487.2 1033.9 4566 2535.8 17 189.2 1841 18 1060.8 4684.5 193 1900.7 2590.8 19 1092.1 4823.4 193 1966.1 2664.2 20 1116.5 4930.9 189.2 2017.1 2724.6 21 1141.4 5039.1 188.8 2080 2770.4 22 1169.6 5167.8 193.7 2138.3 2835.8 Table 3-7: B3 Applied Load Steps and Resulting Girder Moments (Part I) 104 Total Load Applied Mx (Total) Mx (G1) Mx (G2) Mx (B3) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m 23 1195.5 5281.5 185.2 2205.5 2890.8 24 1223.4 5407.3 185.1 2279.2 2943 25 1249.4 5524.3 181 2340.4 3002.9 26 1273.7 5633.7 176 2403.7 3054 27 1299.6 5748.6 171.8 2471.3 3105.6 28 1326.3 5868.3 160.5 2549.1 3158.6 29 1347.9 5962.8 146.5 2629 3187.2 30 1371.9 6068.6 153.1 2678.9 3236.6 31 1401.8 6201.2 140.9 2777.5 3282.9 32 1417.9 6271.6 128.9 2830.3 3312.4 33 1434.6 6345.2 111.6 2896.9 3336.7 34 1445.2 6395.5 103.8 2940.9 3350.8 35 1452.6 6426.7 94.6 2966.8 3365.2 36 1454.9 6436.9 85.4 2996.4 3355.2 37 1457.8 6450.3 79 3009.6 3361.7 38 1406.5 6203.7 44.1 2950.2 3209.4 39 1452.6 6426.4 71.2 3023.6 3331.5 40 1455.5 6440.7 68.7 3034.7 3337.3 41 1459.9 6459.8 65.2 3046.5 3348 42 1458.6 6457.1 62.8 3055.7 3338.6 43 1460.4 6463.9 59.4 3062.5 3342 44 1499.7 6620 68.7 3175.9 3375.4 45 1503.8 6634.5 21.9 3329.1 3283.5 46 1479.9 6533.4 -154.5 3671.2 3016.7 Table 3-8: B3 Applied Load Steps and Resulting Girder Moments (Part II) 105 Load Total Compression Flange, Inside Tip, Extr e Fiber Stress Moments a tiem t Sec on Case Applied ? z ? z ? z ? z t.) x M y lat. ? z ? z (la M x M Bi M Load Total from from from fr ct irect mom Dire Ind Co p. M x M y M z Flange P z (a) b) (c) (c el (b) ( /(a) )/M x yi d kN MPa MPa MPa M M a m -m k 2 -m Pa Pa MP kN- kN kN-m N-m kN Elastic Install. 86 -2 -0 8 4 0. 8 45.8 -68.26 -41.64 2. 9.00 .4 -26.1 63 536. -3.7 16.7 DL -102.30 -71.53 -4.12 -27 1. 8 0. 2 43.9 .4 .85 21 -31.9 45 922. 5.3 20 Install.+DL -170.56 -113.17 -1.2 -5 0. 2 0. .1 89.7 .0 6 6.85 73 -58.1 51 1459 1.6 37 (1) 0.0 1.2 0. 0 0. 2 58.1 89.7 .0 28 -170.52 -113.18 - 5 -56.84 76 -58.1 51 1459. 14 6.9 37 0. (2) 56.4 -2.4 -6 0. 9 0. 9 04.0 95.9 .3 30 -185.29 -123.01 2 0.76 91 -63.1 51 1585. 16 8.5 40 0. (3) 148.9 -209.34 -139.41 -4.03 -67 1. 4 0. 4 38.5 105.7 .3 35 .00 11 -71.0 51 1797. 18 15.4 45 0. (4) 276.5 -244.41 -163.17 -6.4 -7 1. 2 0. 7 56.2 120.2 .6 41 2 6.20 38 -82.6 51 2103. 21 23.9 52 0. (5) 406.5 -280.65 -187.83 -8.71 -8 1. 3 0. 7 2481.0 135.4 .2 47 5.81 71 -94.5 50 2421. 39.3 60 0. (6) 536. -317.54 -212.71 - 8 -9 2. 0. 4 2800.9 151.00 11.2 5.70 15 -106.99 50 2742. 63.3 68.2 0.53 (7) 664. -354.77 -237.61 - 9 -10 2 81 0. 4 3113.0 166.8 .3 59 9 14.0 5.71 .65 -119. 50 3063. 102.6 76 0. (8) 802.3 -394.28 -263.40 -17.49 -11 2 83 0. 0 3458.6 9 183.6 .3 66 6.34 .95 -133. 51 3396. 165. 85 0. (9) 826.0 8. -11 3 82 0. 6 3511.2 5 187.2 .2 67 -401.90 -268.18 -1 16 8.65 .10 -136. 51 3457. 268. 87 0. (10) 852.7 -411.88 -274.18 -19.21 -12 65 3. 85 0. 9 3578.9 3 191.9 .7 68 1. 15 -140. 51 3534. 434. 89 0. Plastic (11) 872.2 0. .98 3. 67 0. 9 3617.1 8 204.5 .8 69 -421.46 -278.99 -2 69 -124 19 -145. 52 3596. 702. 92 0. (12) 906.6 3. 3.02 73 0. 0 3705.3 1 89.7 .3 70 -435.84 -286.13 -2 11 -129.62 -152. 53 3689. 1137. 97 0. . . . . . . . . . (44) 4834.4 0.92 1499.7 pan resses and MomentsT 3-9: B3 Mid-S Stable Tabl 9 con he mi str nd ts First yield occurred at the insid of po mp fl rin 0 At this ad level, B3 was resisting a vertical bending mom 3,535 kN-m (2,606.8 k-ft), which represents approxim ly 6 he yie me is t. This rmalized ratio wa sed at wh wa ng m m of 4,834 kN-m (3,565.2 ). Th of flan ndi s to lange b ding stress ranged b een d 0 ug e e egi test. A co e f d i the ver al moment resistance of the B3 component is presented in Figure 3-32. The individual results are included in Table 3-7. At first yield, step 10, these results differ by 2%. e 3- tains t B3 test d-span esses a momen . e tip the com nent co ression ange du g step 1 . lo ent of ate 8% of t vertical ld mo nt for th componen no s rai to 0.92 step 44 en B3 s resisti a maxi u k-ft e ratio lateral ge be ng stres vertical f en etw 0.50 an .51 thro hout th lastic r me of this mparison of the indirect and direct m thods o etermin ng tic B3 Vertical Bending Moment (Mx) 0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0 3500.0 4000.0 0.0 200.0 400.0 600.0 800.0 1000.0 Total Applied Load (kN) M o me n t ( k N - m) Direct Indirect Figure 3-32: B3 Vertical Bending Moment Figure 3-33 illustrates the mid-span vertical bending moments of G1, G2 and B3 as a function of the total applied load for this component test. The test progressed until G2 107 resisted a majority of the applied mid-span moment. However, this condition was not assu nts red until load step 46, because at load step 45 the applied vertical bending mome carried by G2 and B3 were very similar 3,329 kN-m vs. 3,284 kN-m (2,455.1 k-ft vs. 2,421.5 k-ft). Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m 0 1000 2000 3000 4000 5000 6000 G1 Test ) G2 Test B3 Test Figure 3-33: Test Frame Mid-Span Vertical Bending Moments, B3 Test The effects of dead load and installation on the longitudinal strain state at mid-span of B3 are shown in Figure 3-34. The overlapping regression lines indicate linear-elastic behavior and the absence of local plate distortion at this cross-section under these small loads. Figure 3-35 shows the state of B3 mid-span longitudinal strain at the load level required to produce first yield in the cross-section. At this load level, step 10, the separating regression lines of the web in compression as well as the crossing and 108 separating regression lines across the com bending in the cross-section. 109 pression flange are evidence of local plate Center of Curvature - 2 0 0 0 - 1 0 0 0 0 1000 2000 -50 -40 00 00 -3000 0 -20 -1000 00 B St 3 Section E ep 1 ? y -? y 0 00 1000 20 3000 4000 5000 -? y ? y ure 3-34: B3 Mid-S su rom Installation and Dead Load Fig pan Longitudinal Strain (Step 1) S tate Re lting F Center of Curvature -2000 -1000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B3 Section E Step 10 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-35: B3 Mid-Span Longitudinal Strain State During Step 10 Figures 3-36 and 3-37 show the very similar longitudinal strain states at cross-frames N6L and N6R, respectively, produced during step 10. In fact, both braced sections behaved almost identically throughout both the elastic and inelastic portions of the B3 test. 110 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B3 Section C Step 10 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-36: Longitudinal Strain State in B3 Near Cross-Frame N6L During Step 10 (Excluding Installation Effects) 111 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B3 Section H Step 10 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-37: Longitudinal Strain State in B3 Near Cross-Frame N6R During Step 10 (Excluding Installation Effects) The yield limit of the steel in the tension flange of B3 at mid-span was first reached during step 14. As seen in Figure 3- l there is evidence of through thickness yielding at the inside tip of the com l 38, at this load leve pression flange and of an increase in the ocal plate bending in this flange and along the depth of the web in compression. 112 Center of Curvature -2000 -1000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B3 Section E Step 14 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-38: B3 Mid-Span Longitudinal Strain State During Step 14 Figures 3-39 and 3-40 show the longitudinal strain state at cross-sections N6L and N6R, respectively, during step 21. At this load level, the outside tip of tension flange at N6R reaches yield during step 22, and the outside tip of the compression flange at N6L r load both locations has just reached its yield limit. The outside tip of the compression flange at eaches yield at step 23. The longitudinal strain states at these locations at the respective steps can be seen in Figures 3-41 and 3-42. 113 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B3 Section C Step 21 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-39: Longitudinal Strain State in B3 Near Cross-Frame N6L During Step 21 (Excluding Installation Effects) 114 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B3 Section H Step 21 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-40: Longitudinal Strain State in B3 Near Cross-Frame N6R During Step 21 (Excluding Installation Effects) 115 Center of Curvature -5000 -4000 00 -1000 0 -30 -2000 B3 Section H Step 22 -? y ? y 0 1000 2000 3000 4000 5000 Figure 3-41: L inal tate ear rame uring S p 22 (Exc ding Installation Effects) ongitud Strain S in B3 N Cross-F N6R D te lu 116 B3 S Step ec 23 tion C Center of rvatu Cu re -5000 -4000 -3000 -2000 000 0 -1 ? y -? y 0 000 2000 000 000 5000 1 3 4 Figure 3-42: inal tate ear rame uring S p 23 (Exc ding The test fram e weak state at th ate significant buckling across the plate and through-thickness yielding on the inside half of the plate. The web data also indicate significant plate bending at the cross-section. While the tension flange data at this location show yielding across half of the plate, little evidence of significant local plate bending is displayed. Longitud Strain S in B3 N Cross-F N6L D te lu Installation Effects) e?s response briefly becam er after step 31. The longitudinal strain at load step is shown in Figure 3-43. The compression flange data indic 117 118 Center of Curvature - 2 0 0 0 0 0 0 0 - 1 0 0 1 0 0 2 0 0 -5000 -3 -2000 -4000 000 -1000 0 B ction E St p 31 3 Se e ? y -? y 0 3000 10 20 00 00 40 50 00 00 -? y ? y Figure 3-43: B3 Mid-Span Longitudinal Strain State During Step 31 In a post-buckled state, the stiffness of B3 remained stable until an applied load of s) h level corresponds to the maximum resisted ver ,8 -m (3,565.2 k-ft). The ained stable enough to sustain an addi applied load of 1,504 kN (338.1 kip), despite the failure of B3. 1,50 mid-span section at this step is shown in 0 kN (337.2 kip was reached during step 44. The longitudinal strain state of the B3 Fig en ur t b e 3 y B -4 3 4. T of 4 is l 34 oad kNtical bending mom frame rem tional load increment, step 45, at a total Center of Curvature -2 00 -1 00 10 00 20 00 0 0 0 -5000 -4000 -3000 -2000 -1000 0 B3 Section E Step 44 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-44: B3 Mid-Span Longitudinal Strain State During Step 44 Figure 3-45 depicts the longitudinal strain state of the mid-span of G2 while it experienced the greatest demand of the B3 test, step 46. While the data plotted do not include the effects of installation of the B3 component, all measurements are far enough away from their respective yield limits to ensure that this girder remained elastic throughout the test. 119 Center of Curvature -200 -100 100 200 0 0 0 0 0 -5000 -3000 -1000 -4000 -2000 0 B3-G2 Step 46 -? y ? y 0 1000 2000 3000 4000 5000 Figure 3-45: Most Critical G2 Mid-Span Longitudinal Strain State During B3 Test 3.7 Bending Component B4 Test The test frame, including the singly symmetric B4 component, was loaded to a maximum applied load level of 1,354 kN (304.5 kip) during step 29 of this test. This load level corresponded to an applied vertical bending moment of 3,223 kN-m (2,376.9 k-ft) at mid-span of the component. The individual applied load levels and the effects of each step on the test frame girders are summarized in Table 3-10. 120 Load Total Applied Mx (Total) Mx (G1) Mx (G2) Mx (B4) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m B4 Elastic 1 0.0 -2.2 0.1 0.5 -2.8 -0.2 16.78 2 45.8 196.4 16.9 61.3 118.2 106.5 1.11 3 143.9 623.6 42.8 195.4 385.4 344.1 1.12 4 268.5 1174.1 76.5 363.4 734.3 653.4 1.12 5 405.7 1774.9 121.7 606.5 1046.7 997.4 1.05 6 535.1 2345.6 157.4 801.6 1386.6 1327.2 1.04 7 672.5 2954.5 201.4 1037.3 1715.8 1676.1 1.02 8 802.7 3530.6 228.3 1262.4 2039.9 2060.3 0.99 B4 Plastic 9 826.5 3635.2 232.9 1303.8 2098.5 2136.2 0.98 10 855.8 3765.3 241.9 1357.2 2166.3 2222.6 0.97 11 879.5 3871.0 242.3 1398.8 2229.9 2302.1 0.97 12 908.3 3998.4 251.2 1452.8 2294.3 13 934.6 4116.5 254.8 1501.2 2360.5 14 959.9 4227.8 259.7 1551.1 2417.0 15 985.9 4342.1 261.5 1598.7 2481.9 16 1012.6 4462.3 270.8 1650.6 2541.0 17 1040.6 4587.1 271.6 1702.8 2612.7 18 1065.7 4698.4 274.9 1753.1 2670.3 19 1093.5 4820.2 277.7 1811.4 2731.0 20 1117.6 4931.3 278.9 1860.8 2791.7 21 1142.1 5041.6 276.1 1916.3 2849.2 22 1169.2 5166.3 277.0 1976.7 2912.7 23 1193.6 5271.9 272.3 2037.2 2962.5 24 1219.9 5390.8 268.5 2106.1 3016.2 25 1246.3 5511.7 264.0 2176.6 3071.1 26 1269.4 5616.4 252. 6.0 3118.2 1 224 27 1295.1 5732.6 245.7 2323.0 3163.9 28 1319.8 5841.8 239.6 2402.1 3200.1 29 1354.5 5995.8 224.1 2548.6 3223.0 30 1295.0 5719.8 122.6 2707.6 2889.6 31 1267.4 5596.4 -65.7 3049.3 2612.8 Table 3-10: B4 Applied Load Steps and Resulting Girder Moments The ratio of indirect to direct method for determining the mid-span moment of B4 was 0.99 for load step 8, which is the load level that produced first yield in B4. This ratio is illustrated t re 3-46. hroughout the entire range of elastic behavior of this test in Figu 121 B4 Vertical Bending Moment (Mx) 0.0 500.0 1000.0 1500.0 2000.0 2500.0 3000.0 0.0 50.0 100.0 150.0 200.0 Total Applied Load (kN) M o me n t ( k N - m) Direct Indirect Figure 3-46: B4 Vertical Bending Moment Table 3-11 contains the B4 mid-span stresses and moments for the entire elastic regime of loading. The table also includes selected information at the maximum resisted vertical bending moment in the component. The ratio of lateral flange bending stress to vertical flange bending stress in the compression flange of this component ranged from 0.43 to 0.49 in the elastic load range. At first yield in B4, the ratio of mid-span vertical bending moment to yield moment was 0.69. This ratio increased to 0.90 at the maximum sustained load level. 122 Load Total Compression Flange, Inside Tip, Extreme Fiber Stress oM ments at Section Case Applied ? z ? z ? z ? z ? z ? z (lat.) M M lat.x M x y Bi M Load Total from from from from Dir pect Indirect Com . M x M y M z P z Flange (a) (b) (b)/(a) (c eld (c) )/M x yi kN MPa MPa MPa MPa MPa MPa kN m N k -m-m kN- k -m N-m 2 kN Elastic Install. -67.45 -52.46 -4.55 -16.82 6.38 -21.37 0.41 69 0 1 .8 6. 1 .3 51 13.6 DL -104.75 -72.41 -3.00 -29.58 0.24 -32.57 0.45 96 7. .7 0.7 5 91.1 20 Install.+DL -172.20 -124.88 -7.55 -46.39 6.62 -53.94 0.43 165 18 1 .3 6.7 .8 42.9 34 (1) 0.0 -172.34 -124.86 -7.58 -46.48 6.58 -54.06 0.43 165 .9 18 1 3 6.5 1653 .8 43.1 34. 0.31 (2) 0.0 -184.23 -132.90 -8.17 -49.72 6.57 -57.90 0.44 176 .9 20 1 8 3.2 1774 .3 53.1 36. 0.33 (3) 0.4 -210.62 -150.81 -9.44 -56.90 6.52 -66.33 0.44 200 .1 23 1 1 0.7 2042 .5 75.2 42. 0.38 (4) 0.4 -245.02 -174.13 -10.82 -66.58 6.51 -77.40 0.44 231 .9 26 2 2 0.1 2390 .9 05.0 49. 0.44 (5) 0.4 -283.33 -200.06 -12.20 -77.56 6.49 -89.76 0.45 265 .3 30 2 0 4.1 2703 .3 38.8 57. 0.50 (6) 0.4 -320.36 -224.92 -13.68 -88.28 6.52 -101.96 0.45 298 .3 34 2 8 3.9 3043 .0 71.8 64. 0.56 (7) 0.4 -360.63 -251.22 -15.53 -100.20 6.31 -115.73 0.46 333 .5 38 3 5 5 2.8 3372 .6 08. 73. 0.62 (8) 0.4 -411.08 -280.18 -18.53 -117.66 5.28 -136.18 0.49 371 .6 46 3 3 5 7.0 3696 .1 62. 86. 0.68 Plastic (9) 0.4 -421.11 -285.90 -19.20 -121.14 5.12 -140.34 0.49 379 .2 47 3 0 2 2.9 3755 .7 73. 89. 0.69 (10) 0.5 -433.11 -292.41 -20.02 -125.48 4.80 -145.50 0.50 387 .0 49 3 4 5 9.3 3823 .8 86. 92. 0.71 . . . . . . . . . . . . (29) 0.0 7948 .7 0.90 Table 3-11: B4 Mid-Span Stresses and Moments The mid-span vertical bending moments for each of the girders of the test frame during the B4 test are shown in Figure 3-47. The plots in this figure illustrate the data included for G1, G2 and B4 (indirect method) in Table 3-10. While the maximum sustained load occurred at step 29, the test was continued until step 31. At this point, G2 was resisting a majority of the applied vertical bending moment. The last point in each plot of the figure describes this condition. Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m ) 0 1000 2000 3000 4000 5000 6000 G1 Test G2 Test B4 Test Figure 3-48 shows the longitudinal strain state of the B4 mid-span resulting from the installa eral, the data indicate linear-elastic behavior of the section. The magnitude and gradient of Figure 3-47: Test Frame Mid-Span Vertical Bending Moments, B4 Test tion of the component and from the dead load effects of the test frame. In gen 124 stra ection are consistent with the expected singly sym in in each of the plates of this cross-s metric behavior. Cent Cu er of rvature -20 0 -10 0 0 0 0 10 00 20 00 -5000 -4000 -3000 -2000 -1000 0 B4 Section E Step 1 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-48: B4 Mid-Span Longit Strain State Resulting From ep 1) Figure 3-49 illustrates the first yield s at mid-span of B4 that occurred at step 8 of the te his lo l, the data ig t loc l bending that is the result o evat slen s, 18 e cross ections a N6L and N6R during step 8 are shown in Figures 3-50 and 3-51 respectively. These plots do not include the effects that the inst had e cros ns. Ho ever, the udinal Installation and Dead Load (St train state st. At t ad leve web indicate s nifican al elastic p ate f the el ed web dernes 8.0. Th -s t allation on th s-sectio w 125 data far en om t ated limi port clusion hat first ld occurred at mi . are ough fr he indic yield t to sup the con t yie d-span Center of Curvature -2 000 -1 000 0 1 000 2 000 -5000 -4000 -3000 -2000 -1000 0 B4 Section E Step 8 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-49: B4 Mid-Span Longitudinal Strain State During Step 8 126 Center of vature Cur -5000 -4000 -3000 -2000 000 0 -1 B4 S Step ect 8 ion C ? y -? y 0 0 0 0 0 0 100 200 300 400 500 Figure 3-50: dina State Near ram uring S ng Longitu l Strain in B4 Cross-F e N6L D tep 8 (Excludi Installation Effects) 127 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B4 Section H Step 8 -? y ? y 0 1000 2000 3000 4000 5000 Figure 3-51: Longitudinal Strain State in B4 Near Cross-Frame N6R During Step 8 (Excluding Installation Effects) The outside tip of the top flange at N6L (Figure 3-52) and at N6R (Figure 3-53) reached their yield limit at steps 18 and 19 respectively. However, the tension (bottom) flange of B4 never came close to the yield limit at anytime during the test. 128 129 Cent Cur er vat of ure -5000 -2000 -1000 -400 -300 0 0 0 B4 Section H Step 18 ? y -? y 0 1000 2 3 000 000 4 5000 000 : Longitudinal s-F ur ep 18 (Excluding Figure 3-52 Strain State in B4 Near Cros rame Installation Effects) N6R D ing St Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B4 Section C Step 19 ? y -? y 0 1000 2000 3000 4000 5000 Installation Effects) Figure 3-53: Longitudinal Strain State in B4 Near Cross-Frame N6L During Step 19 (Excluding The maximum sustained applied load during the B4 test produced the longitudinal strain state shown in Figure 3-54 at mid-span ponent. The associated vertical bending moment being resisted by the section at this load step was 4,880 kN-m (3,598.6 k-ft tion l. of the com ). The figure indicates significant buckling and yielding in the compression flange. The data also project yielding within the compression depth of the web in conjunc with significant web distortion. The state of longitudinal strain in the tension flange is linear and consistent at this load leve 130 Center of Curvature -2000 -1000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B4 Section E Step 29 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-54: B4 Mid-Span Longitudinal Strain State During Step 29 Figure 3-55 demonstrates that G2 remained elastic throughout the loading regime. The strain data plotted are significantly below the respective yield limits shown. Also, the regression lines do not indicate any degree of local plate bending. 131 Center of Curvature -200 0 -100 0 0 100 0 200 0 -5000 -4000 -3000 -2000 0 -1000 B4-G2 Step 31 -? y ? y 0 1000 2000 3000 4000 5000 Figure 3-55: Most Critical G2 Mid-Span Longitudinal Strain State During B4 Test 3.8 Bending Component B5 Test 1,833 kN (412.2 kip). However, the resisted by B5 occurred at step 38 at an applied load level of 1,732 kN (389.5 kips). A summary of applied loading inform The test frame containing component B5 was loaded in 46 steps to a maximum of maximum moment ation for this component test is presented in Table 3-12 and Table 3-13. 132 Total Load Applied Mx (Total) Mx (G1) Mx (G2) Mx (B5) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m B5 Elastic 1 0 0.9 -0.1 0.4 0.6 0.7 0.92 2 57.7 271.9 20 85 166.9 135.3 1.23 3 151.9 668.4 49.8 215.5 403.1 351.1 1.15 4 274.2 1203.1 75.5 419.3 708.4 658 1.08 5 406.2 1786.2 107.7 641 1037.5 990.7 1.05 6 534.9 2358.8 137.6 862.5 1358.6 1328.1 1.02 7 670.1 2957.5 162.7 1105.1 1689.6 1697 1 8 798.8 3525.8 185.6 1338.7 2001.5 2052.7 0.98 9 917.2 4037.7 198.8 1568.9 2269.9 2393.8 0.95 B5 Plastic 10 1066.4 4703 226.4 1833.9 2642.7 2792.8 0.95 11 1101.5 4857.8 232.6 1888.6 2736.6 2884.5 0.95 12 1130.6 4982 237.7 1949.7 2794.5 13 1159.3 5110.7 245.4 2008.9 2856.5 14 1184.5 5222.5 245.8 2055.6 2921.2 15 1208.1 5327.7 248.1 2113.1 2966.5 16 1243.2 5481.9 251.5 2185.2 3045.2 17 1268.9 5596.4 251.5 2225.7 3119.2 18 1290 5690.5 248.4 2280.1 3162 19 1314.3 5797.9 251.2 2338.6 3208.1 20 1346.2 5936.4 249.7 2406.1 3280.6 21 1365.6 6019.3 240.3 2469.7 3309.3 22 1396.7 6157.6 240.8 2532.7 3384.1 23 1425.4 6285.1 237.1 2602.1 3445.9 24 1449.7 6393.4 231.8 2680.7 3480.9 Table 3-12: B5 Applied Load Steps and Resulting Girder Moments (Part I) 133 Load Applied Mx (Total) Mx (G1) Mx (G2) Mx (B5) Total Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m 25 1483.2 6540.3 225.4 2768.1 3546.8 26 1493.5 6587 200.1 2841.3 3545.6 27 1529.6 6745.4 203.2 2908.2 3634 28 1554.6 6854.8 189.6 3008.5 3656.7 29 1587.6 6999.9 173.4 3091.3 3735.2 30 1616.8 7128.8 169.2 3193.7 3765.8 31 1642.8 7246.3 135.6 3276.6 3834.1 32 1662.9 7336.1 127.4 3392.6 3816 33 1696.1 7479.2 103.8 3526.9 3848.5 34 1703.8 7517.8 68.1 3585.2 3864.5 35 1654.5 7298 8.9 3549.7 3739.4 36 1680.5 7416.8 20.8 3605.9 3790.1 37 1708 7537.5 35.5 3662.7 3839.3 38 1732.7 7646 31.7 3745 3869.3 39 1733.2 7647.3 -0.6 3794.6 3853.2 40 1749.9 7719.9 -19.3 3877 3862.2 41 1768.5 7803.9 -35.1 3987.7 3851.3 42 1782.1 7861 -71 4110.1 3821.9 43 1799.1 7937.9 -108.2 4210.7 3835.4 44 1814.2 8006 -166.2 4391.5 3780.7 45 1826.8 8061.5 -214.9 4531.1 3745.3 46 1833.3 8092.1 -265.9 4664.7 3693.3 47 1819.8 8030.6 -347.6 4809.1 3569.1 48 1809.1 7983.8 -428 4990.4 3421.3 49 1804.1 7961.9 -506.2 5122.2 3345.9 Table 3-13: B5 Applied Load Steps and Resulting Girder Moments (Part II) 134 Load Total Compression Flange, Inside Tip, Extreme Fiber Stress oM ments at Section Case Applied ? z ? z ? z ? z ? z ? z (lat.) M x x M lat. M y Bi M Load Total from from from from Direct Indire mct Co p. M x M y M P z Flange z (a) (b) (b)/(a) (c) (c yiel )/M x d kN MPa MPa MPa MPa MPa MPa kN-m kN-m N k 2 - k -m N-m kN m Elastic Install. -84.28 -35.14 -0.91 -48.08 -0.15 -49.00 1.39 51 1. .2 1.9 3 86 35.4 DL -89.63 -61.57 -5.19 -22.35 -0.52 -27.54 0.45 896.9 7. .95 40.1 19 Install.+DL -173.91 -96.71 -6.10 -70.44 0.79 1408.8 8. .3-0.66 -76.54 8 126.3 55 (1) 0.0 -173.96 -96.75 -6.18 -70.44 -0.59 -76.62 0.79 1409.5 409. 8 1 4 .9 126.3 55.3 0.24 (2) 57.7 -187.78 -106.00 -7.17 -73.86 -0.75 -81.04 0.76 1544.1 575. 1 4 .5 1 7 0.4 132. 58 0.27 (3) 151.9 -209.70 -120.81 -8.78 -79.33 -0.78 -88.11 0.73 1759.8 811. 1 2 .6 1 9 2.7 142. 63 0.31 (4) 274.2 -240.77 -141.88 -10.89 -87.16 -0.84 -98.05 0.69 66.8 117. 1 3 .8 20 2 1 5.8 156. 70 0.37 (5) 406.2 -274.40 -164.72 -13.13 -95.77 99.5 446. 1 7 .6 -0.77 -108.91 0.66 23 2 2 9.0 171. 78 0.43 (6) 534.9 -307.69 -187.88 -14.89 -105.03 0.10 -119.92 0. 2736.9 2767. 21 3 .6 64 4 .5 188. 86 0.48 (7) 670.1 -343.90 -213.20 -16.55 -115.84 1.69 -132.39 0.6 3105.8 098. 23 7 .6 2 3 4 .9 207. 95 0.54 (8) 798.8 -378.93 -237.62 -18.09 -126.47 61.4 410. 26 8 4. 3.25 -144.56 0.61 34 3 3 .2 226. 10 4 0.59 (9) 917.2 -411.94 -261.03 -19.25 -136.61 02.6 678. 27 0 2. 4.94 -155.85 0.60 38 3 7 .8 245. 11 5 0.64 Plastic (10) 5 1.37 0.59 420 4051. 32 1 3. 1066.4 -453.46 -288.43 -22.42 -148.9 6.34 -17 1.6 5 .4 267. 12 7 0.70 (11) 7 4145. 33 0 6. 1101.5 -462.69 -294.72 -23.13 -151.6 6.84 -174.80 0.59 4293.3 4 .5 272. 12 2 0.72 . . . . . . . . . . . . 5278. 0.921 (38) 1732.7 Table 3-14: B5 Mid-Span Stresses and Moments Table 3-14 p sh e e ang id-span stresses and mom nts. First yield in the component was projected to have occurred during load step 9 at a load level of 917.2 (206 . A ep, al mi vertic l bendin moment in B5 wa ,679 2,7 -ft) mo hen lized by the vertical bending yield mo res pe nc of 0 the m ximum vertical bending mom s normalized ratio increased to 0.92. A comparison of the direct and indirect methods to determine the resisted vertical moment in B5 is shown in Figure 3-56. While this comparison shows good agreement throughout most of the elastic regime of loading, the methods have diverged approximately 5% at the point that inelasticity is introduced into the system. rimarily ows th lastic r e B5 m e kN .2 kip) t this st the tot resisted d-span a g s 3 kN-m ( 12.9 k . This a unt, w norma ment, ults in a rforma e ratio .64. At a ent resisted by B5 during step 38, 5,278 kN-m (3,892.4 k-ft) thi B5 Vertical Bending Moment (Mx) 0.0 500.0 1000.0 2000.0 2500.0 0.0 200.0 400.0 600.0 800.0 1000.0 Total Applied Load (kN) M o n t ( N - m) 1500.0 3000.0 3500.0 4000.0 me k Direct Indirect Figure 3-56: B5 Vertical Bending Moment 136 The mid-span vertical bending moments of the test frame that result from the applied loading are shown in Figure 3-57 for the B5 test. The B5 test record shows a small plateau of post-peak stability prior to ultimate failure of the section and a dramatic shedding of load to the test frame, in particular for G2. Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m ) 0 1000 2000 3000 4000 5000 6000 G1 Test G2 Test B5 Test Figure 3-57: Test Frame Mid-Span Vertical Bending Moments, B5 Test ges indicate the presence of a significant torsional warping strain. The separation of the regression lines across the tension flange is evidence of some local vertical plate bending. The effects of installation and dead load on the mid-span longitudinal strain state of B5 are shown in Figure 3-58. The complementary strain gradients across the flan 137 138 C C e ent urv er of atur - 2 0 0 0 0 0 0 0 0 0 - 1 0 0 0 1 2 0 -5000 -4000 -300 -2000 -1000 0 0 B5 Section E Step 1 ? y -? y -100 1000 2000 3000 4000 0 0 -? y ? y udinal t p in re 3-59, the compression ge a has al n ver, the web plate data cate a uniform flexing that caus si e in pression on the out o e lted from the i d effects h a oad l. Figure 3-58: flan indi B5 Mid-Span Longit Strain State Resulting From tep Installation and Dead Load (S 1) At the firs rojected yield in the B5 test, shown Figu of the mid-sp n section mi es nim ten di on sto on rtio th . H si owe de face and com side face f the w b. Also, the distortion in the tension flange that resu nstallation and dead loa as not progressed t this l leve Center of Curvature -2000 -1000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B5 Section E Step 9 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-59: B5 Mid-Span Longitudinal Strain State During Step 9 The cross-section at N6L, shown in Figure 3-60, was the braced-section during step 9 that was the most critical. While the strain data plotted do not include the effects of installation on the cross-section, the magnitudes fall significantly short of the yield limits indicated. The tension flange at this section does reach its indicated yield limit at step 16 (see Figure 3-61). 139 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B5 Section C Step 9 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-60: Longitu ng dinal Strain State in B5 Near Cross-Frame N6L During Step 9 (Excludi Installation Effects) 140 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B5 Section C Step 16 ? y -? y 0 1000 2000 3000 4000 5000 Figure 3-61 ace of the web plate in this region has been prevented from yielding by the tensile strains caused by the its yield : Longitudinal Strain State in B5 Near Cross-Frame N6L During Step 16 (Excluding Installation Effects) The effects on the longitudinal strain state at mid-span of B5 during the maximum sustained moment of the test, step 38, are shown in Figure 3-62. At this load step, most of the compression flange has yielded and distorted significantly. Also, a large portion of the depth of web in compression has yielded the outside face of the plate. The inside f local buckling of the plate. The tension flange has also reached 141 limit over approximately the inside half of the plate. However, the regression lines for each surface of data do not indicate an increase in the local level of lateral distortion. Center of Curvature -2 00 0 -1 00 0 0 10 00 20 00 -5000 -4000 -3000 -2000 -1000 0 B5 Section E Step 38 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-62: B5 Mid-Span Longitudinal Strain State During Step 38 Figure 3-63 shows the longitudinal strain state at mid-span of G2 during the maximum vertical bending moment that it experienced during the B5 test, step 49. This figure confirms that G2 remained well within the elastic region throughout this component test. 142 Center of Curvature -200 0 -100 0 0 100 0 200 0 -5000 -3000 -1000 0 -4000 -2000 B5-G2 Step 49 -? y ? y 0 1000 2000 3000 5000 4000 Figure 3-63: Most Critical G2 Mid-Span Longitudinal Strain State During B5 Test 3.9 Bending Component B6 Test Table 3-15 and Table 3-16 contain the applied load levels associated with eac the B6 component test. The mid-span girder vertical bending moments that resulted from the applied loading for G1, G2 and B6 are also in Table 3 h step of -15 and Table 3-16. First yield in B6 was projected to occur during step 13 with a sustained load level of 1,354 kN (304.5 kip). At this step, the resisted vertical bending moment due to the applied loading 143 in B moment resisted by B6 6 was 3,442 kN-m (2,538.3 k-ft). The maximum vertical bending was 4,886 kN-m (3,603.4 k-ft) and occurred during step 38. Load Total Applied Mx (Total) Mx (G1) Mx (G2) Mx (B6) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m B6 Elastic 1 0.1 -0.5 0.1 0.6 -1.2 0.2 -6.83 2 51.9 216.6 17.1 69.3 130.3 122.3 1.06 3 136.1 594.3 46.4 180.8 367.1 326.3 1.12 4 271.8 1188.5 88.4 384.8 715.3 671 1.07 5 404 1771.4 130 583.3 1058.1 1004.6 1.05 6 535.3 2355.6 169.5 793.1 1393 1355.7 1.03 7 670.7 2953.2 208.4 1003.7 1741.1 1724 1.01 8 804.9 3541 244.3 1223.7 2073 2095.1 0.99 9 937.6 4133.2 278.8 1436.1 2418.4 2462.6 0.98 10 1068.8 4707.4 306.1 1659.5 2741.8 2839.7 0.97 11 1197.9 5278 334.4 1878.6 3065 3210.8 0.95 12 1331.1 5858.3 359.7 2097.5 3401.1 3592.7 0.95 13 1354.2 5960.4 365.4 2153.1 3441.9 3665.2 0.94 B6 Plastic 14 1378.4 6065.3 371 2192.8 3501.4 3732.6 0.94 15 1405.5 6187.1 369.8 2236.8 3580.5 3814.7 0.94 16 1432.1 6306.1 389.1 2279.2 3637.7 17 1486.3 6544.5 403.1 2365.7 3775.7 18 1517.2 6681.2 405.3 2429.8 3846.1 19 1541.8 6788.5 405.8 2464 3918.6 20 1566.3 6898.1 412.6 2522.7 3962.9 21 1594.4 7024.3 414.5 2567.4 4042.4 Table 3-15: B6 Applied Load Steps and Resulting Girder Moments (Part I) 144 Load Applied M Total x (Total) Mx (G1) Mx (G2) Mx (B6) Step Loa ct t d Indire Direc (b) (a)/(b) (a) kN kN kN-m -m kN-m kN-m kN-m 22 16 7 1 4 25 157.1 418.7 2627. 4111. 23 164 7 6.8 251.5 414 2674.8 4162.7 24 16 7 73 367.8 415 2731.9 4220.8 25 170 7 4 8 7.7 520.7 419.5 2794. 4306. 26 172 7 3 5 6.3 603.1 416.3 2853. 4333. 27 176 7 3 1 5.4 771.8 421.4 2937. 4413. 28 177 78 .7 2.9 07.3 403.4 2982.2 4421 29 18 8 1 12 7981 409.1 3048. 4523. 30 1839.6 7 2 8102 405.1 3119. 4577. 31 18 8 1 6 71 243.4 397.7 3217. 4628. 32 190 8 7 4 3.2 385.5 394.4 3306. 4684. 33 192 8 5 2.7 472.3 372.8 3378. 4721 34 1949.1 8590.6 365.4 55.7 4769.5 34 35 1981.1 8736.4 343 3588.3 4805.1 36 2007.6 8856.8 319.6 3693 4844.2 37 2033.9 8973.3 295.5 3807.8 4870 38 2071.6 9140.3 248.2 4006 4886.2 39 2095.4 9252.8 183.9 4195.9 4873 40 2113.2 9332.8 138.9 4335.8 4858.1 41 2138.3 9446.9 46.6 4626.2 4774.1 42 2165.1 9572.4 -85.9 4981.9 4676.4 43 2171.4 9598.2 -208.7 5282 4525 Table 3-16: B6 Applied Load Steps and Resulting Girder Moments (Part II) Selected stresses and moments, primarily from the elastic regime of loading, are listed in Table 3-17 for the mid-span cross-section of B6. These data indicate that at first yield in the component, the ratio of compression flange lateral bending stress to vertical bending stress was 0.37. Also, the largest sustained vertical bending moment in the elastic range was 4,955 kn-m (3,654.3 k-ft). This amount, when normalized by the theoretical vertical bending yield moment, yields a performance ratio of 0.73. This ratio 145 increases to 0.94 at the maximum moment resisted by B6, 6,400 kN-m (4,719.4 k-ft), which occurred during step 38 of this test. The direct and indirect methods of determining the resisted vertical bending moment at mid-span of B6 during the elastic loading regime of this component test are contrasted in Figure 3-64. The methods again begin to diverge at about the 890 kN (200 kip) total applied load level. This separation represents approximately 6% at the load step during which first yield is projected to have occurred. 146 Load Total C F , e Tip, Extreme Fib es me t onompression lange Insid er Str s Mo nts a Secti Case Applied ? z ? ? ? yz ? z z ? z z (lat.) M x M x M Bi M lat. Load Total fro m fro f D In . m fro m rom irect direct Comp M e M x M y z P z Flang (a) )/(a) (c)/M d (b) (b (c) x yiel kN MP M a a M k k -m N kNa P MP Pa MPa MPa N-m N-m kN k -m 2 -m Elastic Install. -30.18 31. 4 -2. - 46 .0 56 5. - 98 4.8 38 0.66 2. -0 8 1.9 -8.6 3 2.2 DL -74.77 54. -2 4 18. - -2 8 39 - 15 .1 - 12 0.36 0.25 0.37 951.5 3. .9 -17.9 Install.+DL -104.95 86. 20. - - .8 45 7 - 13 2.70 - 50 1.02 17.79 0.21 1513.3 -4 .2 -15. (1) 0.1 -104.82 86. 20. - - 15 8 45 7 0. - 14 2.73 - 49 0.93 17.75 0.21 1513.5 12.2 -4. .2 -15. 22 (2) 51.9 -114.86 93. 22. - - 16 5 50 4 0. - 09 1.99 - 83 0.93 20.84 0.22 1635.7 43.6 -3. .3 -18. 24 (3) 136.1 -131.63 0 26. - - 1880.4 6 58 8 0. -1 4.70 0.92 - 74 1.11 25.82 0.25 1839.6 -1. .9 -22. 28 (4) 271.8 -159. 2 3. - -3 2 21 2228.6 8 73 8 0.04 -1 4.31 -0.44 -3 22 1.07 3.66 0. 7 84.3 0. .2 -29. 33 (5) 404.0 -185. 4 9. - -4 2 25 2571.4 9 87 5 0.53 -1 3.30 -1.63 -3 65 0.95 1.28 0. 9 17.9 2. .4 -36. 38 (6) 535.3 -212. 6 6. - -4 3 28 2906.3 3 0 5 0.55 -1 3.29 -2.41 -4 77 0.08 9.18 0. 0 69.1 4. 1 3.1 -43. 43 (7) 670.7 -240. 8 4. -5 3 32 3254.4 5 2 0 0.61 -1 4.24 -3.09 -5 54 1.27 7.63 0. 1 37.3 5. 1 0.2 -51. 48 (8) 804.9 -269. 0 2. -6 3 36 3586.4 3 3 8 0.15 -2 5.36 -4.12 -6 32 2.66 6.44 0. 2 08.4 7. 1 7.4 -58. 53 (9) 937.6 -297. 2 9. 4.12 -7 3 3975.9 3931.7 6 5 6 0.49 -2 6.28 -5.43 -6 90 5.33 0. 3 9. 1 4.1 -66. 58 (10) 1068.8 -326. 4 7. 5.73 -8 3 4353.0 4255.2 .4 7 1 0.92 -2 7.74 -7.56 -7 35 4.91 0. 4 13 1 0.5 -75. 62 (11) 1197.9 -356.30 6 86 14 84. 7.33 -9 4724.1 4578.4 8 0. -2 8. -10. - 62 4.76 0.35 18.0 1 6.5 -83.8 67 (12) 1331.1 -387.18 9 60 58 92. 9.02 -1 5106.1 4914.4 0 0. -2 0. -13. - 02 05.60 0.36 24.0 2 2.8 -93.4 72 (13) 1354.2 -393.05 9 72 48 93. 9.49 -1 5178.5 4955.3 0 0. -2 4. -14. - 35 07.83 0.37 25.6 2 5.8 -95.4 73 Plastic (14) 1378.4 -398.68 -29 56 30 94. 9.83 -1 5246.0 5014.7 0 0. 8. -15. - 65 09.95 0.37 27.1 2 8.6 -97.3 74 (15) 1405.5 -405.70 -30 23 44 96. 10.32 -1 5328.0 5093.8 1 0. 3. -16. - 35 12.79 0.37 29.1 2 2.4 -99.8 75 . . . . . . . . . . . . (38) 2071.6 6399.5 0 .94 B6 Mid-Span StresseTable 3-17: s and Moments B6 Vertical Bending Moment (Mx) 50 6000.0 N 0.0 1000.0 2000.0 3000.0 4000.0 0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0 1600.0 Total Applied Load (kN) M o me n t ( k - m) 00.0 Direct Indirect Figure 3-64: B6 Vertical Bending Moment The mid-span vertical bending moments in G1, G2 and B6, which are due to the applied loading throughout the entire regime of the B6 test, are plotted in Figure 3-65. The peak resisted vertical bending moment in B6 occurred during load step 38. The section initially remained viable post-peak as the test frame continued to take load up until load step 43 when the test was halted. At this load level, 2,172 kN (488.2 kip), B6 was carrying significantly less of the applied moment than girder G2. 148 Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m ) 0 1000 2000 3000 4000 5000 6000 G1 Test G2 Test B6 Test ents, B6 Test itudinal s state are shown in Figure 3-66. This plot primarily indicates that vertical bending was the dominate force effect that resulted from these loadings. The data describ behavior in all plates of the section. Figure 3-65: Test Frame Mid-Span Vertical Bending Mom The dead load and installation effects on the mid-span long 149 train e linear elastic Center of Curvature -2000 -1000 0 1000 2000 -5000 -4000 -3000 -2000 -1000 0 B6 Section E Step 1 ? y -? y 0 1000 2000 4000 3000 5000 -? y ? y Figur ngitudinal Strain State Resulting From Installation and Dead Figure 3-67 presents the m ongitudinal s of B6 at loa This load step is projected to have caused first yield in the cr section on the inside tip of the compression flange. However, first yield in the component most likely occurred at the brace point cross-sections. The data from the cross-sections near the cross-fra N6L and N6R, shown in Figures 3-68 and 3-69 respectively, also projected strain levels in the utside tips of the tension flange. These levels also exceed the yield strain limits at this e 3-66: B6 Mid-Span Lo Load (Step 1) id-span l train state d step 13. oss- mes o 150 same load step. These data do not include any effects for installation of the component; therefore, they m kely re their yi limits ea n the loa g regimost li ached eld rlier i din e. Center of Curvature B6 Se Step 13 -2000 -1000 10 00 20 00 0 -5000 -4000 -3000 -2000 -1000 0 ction E ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y ure 3-67: B6 Mid-Span Longitudinal Strain State During Step 13 Fig 151 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B6 Section C Step 13 ? y -? y 0 1000 2000 3000 4000 5000 ure 3-68: Longitudinal Strain State in B6 Near Cross-Frame N6L During Step 13 (Excluding Installation Effects) Fig 152 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B6 Section H Step 13 ? y -? y 0 1000 2000 4000 3000 5000 Figure 3-69: Longitudinal Strain State in B6 Near Cross-Frame N6R During Step 13 (Excluding Installation Effects) Approximately half of each flange of B6 has exceeded its yield limit by load step 28, shown in Figure 3-70. At this load level, the plotted data indicate that the compression flan , the web data on the figure. ge has buckled while the tension flange displays no evidence of local bending. Also very little out of plane effect exists in 153 Center of Curvature -2 000 -1 000 0 1 000 2 000 -5000 -4000 -3000 -2000 -1000 0 B6 Section E Step 28 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-70: B6 Mid-Span Longitudinal Strain State During Step 28 Figure 3-71 shows the mid-span longitudinal strain state during the maximum sustained vertical bending moment in the component during the B6 test. The compression flange data indicate gross yielding and buckling across most of the plate. The top of the we yielded along its outside face. The tension flange data again indicate yielding across most of t b has also picked up much of the buckling evident in the compression flange and has he plate, but there is no evidence of local bending. 154 Center of Curvature -2 000 -1 000 0 000 2 000 1 -5000 -4000 -3000 -2000 -1000 0 B6 Section E Step 38 ? y -? y 0 2000 4000 1000 3000 5000 -? y ? y Figure 3-71: B6 Mid-Span Longitudinal Strain State During Step 38 Figure 3-72 illustrates the linear elastic state of the mid-span of G2 at its critical load of the B6 component test. 155 Center of Curvature -200 0 -100 0 0 100 0 200 0 -5000 -4000 -3000 -2000 -1000 0 B6-G2 Step 43 ? y -? y 0 1000 2000 3000 4000 5000 3.10 Bending Component B7 Test Figure 3-72: Most Critical G2 Mid-Span Longitudinal Strain State During B6 Test The maximum sustained vertical bending moment due to the applied loading at mid- span of B7 was 2,501 kN-m (1,844.5 k-ft). This moment occurred very early in this component test during step 13. First yield in the component was projected at load step 8. The test frame continued to take load until the test was halted at step 38 with a total applied load of 1,317 kN (296.1 kip). The resulting vertical bending moment in G2 was 156 4,635 kN-m (3,418.5 k-ft). Table 3-18 contains a selected set of data from this test. Total Load Applied Mx (Total) Mx (G1) Mx (G2) Mx (B7) Step Load Indirect Direct (a) (b) (a)/(b) kN kN-m kN-m kN-m kN-m kN-m B7 Elastic 1 0.0 -0.7 0.2 0.0 -0.8 -0.1 7.34 2 55.1 254.6 13.9 78.3 162.4 126.3 1.29 3 139.2 609.0 33.6 209.6 365.7 316.0 1.16 4 275.2 1210.8 59.7 432.3 718.7 650.7 1.10 5 403.7 1779.3 81.8 678.5 1019.0 973.2 1.05 6 532.4 2359.3 98.0 930.8 1330.5 1280.2 1.04 7 672.1 2966.5 104.3 1240.2 1622.1 1596.4 1.02 8 808.5 3565.9 105.8 1540.4 1919.7 1908.7 1.01 B7 Plastic 9 939.3 4143.0 109.0 1837.0 2197.0 2193.2 1.00 10 991.1 4370.7 107.1 1954.8 2308.8 2537.6 0.91 11 1041.8 4595.7 97.8 2078.2 2419.7 12 1071.1 4724.6 95.3 2167.5 2461.8 13 1095.5 4830.5 81.0 2248.4 2501.1 14 1123.6 4956.3 42.1 2415.0 2499.2 15 1109.2 4892.7 12.0 2416.8 2463.9 16 1114.4 4912.2 -8.4 2510.0 2410.6 17 1122.8 4950.9 -41.2 2588.3 2403.8 18 1123.6 4956.4 -65.7 2617.5 2404.6 19 1138.3 5020.3 -92.2 2734.0 2378.5 20 1149.3 5070.9 -123.9 2829.5 2365.2 21 1157.5 5105.9 -158.6 2930.5 2334.0 22 1171.4 5169.8 -188.8 3031.4 2327.2 23 1179.5 5206.6 -213.0 3067.5 2352.0 24 1195.7 5277.5 -232.5 3194.9 2315.1 25 1200.3 5298.8 -280.3 3293.3 2285.9 26 1216.2 5371.3 -311.3 3408.8 2273.8 27 1224.1 5406.5 -346.9 3522.2 2231.2 28 1232.7 5446.2 -385.4 3606.4 2225.1 29 1243.0 5492.4 -418.9 3733.4 2177.9 30 1255.0 5548.1 -452.7 3812.2 2188.6 31 1262.3 5581.6 -487.1 3926.2 2142.5 32 1270.2 5614.6 -520.9 4010.3 2125.2 33 1273.7 5630.5 -567.2 4134.6 2063.0 34 1285.7 5685.9 -605.2 4228.2 2062.9 35 1292.2 5713.9 -638.2 4325.7 2026.3 36 1301.4 5755.8 -669.4 4444.7 1980.5 37 1306.3 5777.4 -704.1 4540.9 1940.5 38 1317.2 5828.0 -741.2 4635.5 1933.7 pplied Load Steps and Resulting Girder Moments Table 3-18: B7 A 157 Figure 3-73 contrasts the direct and indirect methods of determining the resisted vertical bending moment at mid-span of B6 during the elastic loading regime of this component test. The methods again show good agreement throughout the elastic range. At a total applied load of 808.5 kN (182.8 k), the point at which first yield is projected to have been reached in B7, the results of these analysis methods are less than one percent different. B7 Vertical Bending Moment (Mx) 0.0 500.0 1000.0 2000.0 2500.0 3000.0 1 500.0 600.0 700.0 800.0 900.0 Total Applied Load (kN) M o me n t ( k N - m) 1500.0 3500.0 0.0 00.0 200.0 300.0 400.0 Direct Indirect Figure 3-73: B7 Vertical Bending Moment The mid-span vertical bending moments in G1, G2 and B7, which are due to the applied loading throughout the entire load regime of the B7 test, are plotted in Figure 3- 74. The peak resisted vertical bending moment in B7 occurred very early in the tes during load step 13. The section remained viable post-peak as the test frame continued to take load up until load step 38 when the test was halted. At this load level, 1,317 kN t (296.1 kip), B7 was carrying significantly less of the applied moment than girder G2. 158 0 500 1000 1500 2000 2500 M d-S i pan M o ment (kN-m ) 0 2000 1000 3000 40 5000 00 6000 G1 Test Total Applied Load (kN) G2 Test B7 Test Figure 3-74: Test Frame Mid-Span Vertical Bending Moments, B7 Test d-span B7 stresses and m the component, the ratio of lateral flange bending stress to vertical bending stress was 7 was 2,922 kN- m (2,154.8 k-ft). A ratio of 0.61 resulted when the maximum elastic vertical bending moment was normalized by the vertical yield moment. At the maximum vertical bending moment sustained by B7, 3,503 kN-m (2,583.6 k-ft), this ratio increased to 0.73. The mi oments are presented in Table 3-19. At first yield in 0.68. The maximum elastic regime vertical bending moment carried by B 159 Loa l Compression Flange, Inside Tip, Extreme Fiber Stress Mome t ond Tota nts a Secti Ca ed ? z ? z ? z ? z ? z ? z (lat.) M x M x y se Appli M Bi M lat. Loa d Total from from from from Direct Indirect . Comp M x M y M z P z e Flang (a) (b) (b)/(a) (c) (c)/M d x yiel kN MPa MPa MPa MPa MPa MPa kN-m kN-m kN-m N kNk -m 2 -m Elastic Install. -74.84 -15.07 -40.71 -24.99 5.93 -65.71 4.36 190. 53.1 40 4 .2 -51.2 DL -90.04 -64.26 -4.34 -21.58 0.14 -25.92 0.40 811. 5.7 34.7 8 -20.2 Install 164. -79.33 - 6 -46.57 6.07 -91.63 1.16 1002. 58.8 74.+DL - 88 45.0 2 .9 -71.4 (1) 0. 164. -79.32 - 8 -46.62 6.04 -91.70 1.16 1002. 1001.4 58.8 75.0 0.21 0 - 98 45.0 1 -71.5 (2) 55 179. -89.33 - 6 -49.73 5.93 -95.99 1.07 1128. 1164.6 60.4 80 0.24 .1 - 39 46.2 5 .0 -74.8 (3 201. -104.34 - 3 -54.59 5.99 -102.83 0.99 1318. 1367.9 63.0 87 0.29 ) 139.2 - 17 48.2 2 .9 -80.1 (4 240. -130.83 - 1 -63.12 4.94 -114.72 0.88 1652. 1720.9 67.4 10 6 0.36 ) 275.2 - 62 51.6 9 1. -89.4 (5 277. -156.36 - 9 -71.29 4.12 -125.58 0.80 1975. 2021.2 70.9 11 7 0.42 ) 403.7 - 82 54.2 4 4. -97.9 (6 312. -180.66 - 4 -78.75 3.32 -134.79 0.75 2282. 2332.7 73.1 12 7 - 1 0.49 ) 532.4 - 13 56.0 4 6. 105. (7 35 -87.81 2.61 -147.86 0.72 25 78.4 14 3 - 2 0.55 ) 672.1 - 0.94 -205.69 -60.05 98.6 2624.3 1. 115. (8 385. -230.41 - 9 -95.26 2.18 -157.75 0.68 2910. 2921.9 81.6 15 3 - 9 0.61 ) 808.5 - 98 62.4 9 3. 122. Plastic (9 413. -252.92 - 9 -100.42 2.91 -163.30 0.65 3195. 3199.2 82.1 16 6 - 3 0.67 ) 939.3 - 32 62.8 4 1. 127. (1 1 531. 80.19 -1 04 -130.65 -15.15 -235.69 0.84 3539. 3311.0 137.1 21 - 7 0.0) 991. - 03 -2 05. 9 0.3 183. 69 . . . . . . . . (13) .5 3503.3 0.1095 73 Table 3-19: B7 Mid-Span Stresses and Moments The longitudinal strain state at the mid-span of B7 resulting from the installation and dead load effects is sh own in Figure 3-75. All data indicate a linear elastic response from the steel plates of the cross-section. The warping strain has pushed the outside tip of the compression flange into tension at this low load level. Center of Curvature -2 000 -1 000 0 1 000 2 000 -5000 -4000 -3000 -2000 -1000 0 B7 Section E Step 1 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Load ring step 8, shown in Figure 3-76. At this load level, the compression depth of the web is already showing significant out-of-plane bending effects. The strain data for the inside tip of the Figure 3-75: B7 Mid-Span Longitudinal Strain State Resulting From Installation and Dead (Step 1) The projected first yield in the component occurs at mid-span du 161 com e pression flange also contains evidence of local bending, which is illustrated by th separating regression lines. Center of Curvature -2 000 -1 000 0 1 000 2 000 -5000 -4000 -3000 -2000 -1000 0 B7 Section E Step 8 -? y ? y 0 2000 1000 3000 4000 5000 -? y ? y Figures 3-77 and 3-78 support the assertion that first yield occurred at mid-span in the B7 component during step 8. The data in these figures do not include any effect for installation of B into the test frame. However, the strain levels plotted fall significantly from the indicated yield limits. Figure 3-76: B7 Mid-Span Longitudinal Strain State During Step 8 162 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B7 Section C Step 8 ? y -? y Installation Effects) 0 1000 2000 3000 4000 5000 Figure 3-77: Longitudinal Strain State in B7 Near Cross-Frame N6L During Step 8 (Excluding 163 Center of Curvature -5000 -4000 -3000 -2000 -1000 0 B7 ction H Se Step 8 ? y -? y 0 2000 1000 3000 4000 5000 Figure 3-78: Longitudinal Strain State in B7 Near Cross-Frame N6R During Step 8 (Excluding Installation Effects) The B7 mid-span longitudinal strain state at step 10 is shown in Figure 3-79. At this load step, the first evidence of local buckling pears in the compression flange data. The com ap pression depth of the web data shows increased levels of local bending as the web tries to restrain the now buckled compression flange. 164 Center of Curvature -2000 -1000 0 10 00 20 00 -5000 -4000 -3000 -2000 -1000 0 B7 Section E Step 10 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3 Step 10 The ma id-span B7 occurred during load g -79: B7 Mid-Span Longit dinal Strain State During u ximum sustained vertical bending moment by m step 13. The longitudinal strain state at that cross-section during step 13 is shown in Figure 3-80. The strain data indicate that the inside half of the compression flange has surpassed its yield limit and is buckled. The web data contain evidence of local bendin that could also be the result of buckling. Finally, the tension flange is still linearly elastic at this load step. 165 Center of Curvature -2 00 0 -1 00 0 0 10 00 20 00 -5000 -4000 -3000 -2000 -1000 0 B7 Section E Step 13 ? y -? y 0 1000 2000 3000 4000 5000 -? y ? y Figure 3-80: B7 Mid-Span Longitudinal Strain State During Step 13 While the maximum vertical bending moment sustained by B7 occurred at step 13, the test progressed through step 38 when the test frame was resisting a maximum applied load of 1,31 through step 38. 7 kN (296.1 kip). Figure 3-81 ind cates that G2 remained linearly-elastic i 166 Center of Curvature -200 0 -100 0 0 100 0 200 0 -5000 -4000 -2000 -3000 -1000 0 B7-G2 Step 38 ? y -? y 0 1000 2000 3000 4000 5000 : Most Critical G2 Mid-Span Longitudinal Strain State During B7 Test 3.11 Boundary Conditions Figure 3-81 The test frame was loaded from above. The hydraulic actuators reacted off floating frames that were anchored to the laboratory floor using high-strength steel rods. This loading system is described in detail in Section 2.6.1. Radially aligned abutm end supported the test frame. Each end of the three girders that made up the test frame sat on a compound polytetrafluoroethylene ents at each (PTFE) sliding surface bearing. 167 The bearings that supported either end of G1 and G3 were free to rotate and slide in any direction. The bearings that supported both ends of G2 were free to rotate in any direction and were guided to slide in a direction along the tangent to the radius of curvature at the point of support. While approximately 6 mm (1/4 in.) of play existed in the guided direction, these bearing were essentially fixed radially. An attempt to monitor horizontal loads transmitted through the bearings was made using two supported the coefficient of friction, determined for the bearings with a proof load test, the data from the instrumented studs were inconclusive. sets of instrumented studs. However, beyond providing evidence that 3.12 Effect of Installation Strains on Capacity The effect of including the strains captured as a result of the installation process o the moment at first yield and the maximum resisted moment for each component can seen in the data contained in Table 3-20. Recall that while the installation strains applied to B1, B2 and B3 were derived from the data acquired during the installation of B5 and B6, the regression line models used reasonably captured any uncorrupted data from those n be components. Also recall that the installation of B7 was accomplished relatively free of installation effects because the splice plates for the compression flange were drilled in place for this component. 168 Component Total w/Installation Effects w/o Installation Effects Applied Moment Normalized Moment Normalized Load Resisted Moment Resisted Moment M M/M x yield M M/M x yield kN kN-m kN-m At First Yield B1 825.5 3516.1 0.69 2979.3 0.58 B2 852.7 3536.2 0.67 2999.3 0.57 B3 852.7 3578.9 0.68 3042.1 0.58 B4 802.9 3696.6 0.68 3000.6 0.55 B5 917.2 3678.7 0.64 3166.8 0.55 B6 1354.4 4955.2 0.73 4393.4 0.65 B7 808.6 2921.9 0.61 2731.5 0.57 At Maximum Moment B1 1353.5 4539.2 0.90 4002.4 0.79 B2 1434.0 4729.6 0.90 4192.8 0.80 B3 1499.9 4834.4 0.92 4297.6 0.82 B4 1354.4 4879.7 0.90 4183.7 0.77 B5 1732.5 5278.1 0.92 4766.2 0.83 B6 2071.4 6399.5 0.94 5837.7 0.86 B7 1095.5 3503.4 0.73 3313.0 0.69 Table 3-20: Summary of Experimental Results With the exception of B7, the data indicate that the effect of including installation strains on the capacit for approximately 10% of the te strength. The reduced effect of i y calculations were in effect uniform accounting moment capacity at either first yield or ultima nstallation on B7 was expected due to the manner in which this component was installed as noted above. 3.13 Effect of Compression Flange Slenderness The effect of compression flange slenderness on the moment at first yield and t maximum moment resisted are illustrated in Figure 3-82 (also see Table 3-20). Both sets of data trend as expected with compress he ion flange slenderness having a smaller effect on the moment at first yield than on maximum moment. 169 Compression Flange Slenderness 10 15 20 25 30 35 M te st /M x yi el d 0.0 0.2 0.4 0.6 0.8 1.0 Maximum Moment Moment at First Yield Figure 3-82: Effect of Compression Flange Slenderness However, with the exception of B7, which has a very slender compression flange, the normalized maximum moments seemed relatively unaffected by compression flange slendernes to 0.94). Also, with B7 removed from the data set, the trends shown in Figure 3-83 for both moment at first yield and ultimate moment are very similar. These similarities are most likely due to the fact that the failure mode in all cases was a lateral mechanism at mid- span of the component. This mechanism was initially made by a local flange buckle on the inside half of the compression flange and yielding on the outside half. s. Results for all specimens excluding B7 fell within a 4% range (0.90 170 Compression Flange Slenderness 10 15 20 25 30 35 M te st /M yi el d x 0.0 0.2 1.0 0.4 0.6 0.8 Maximum Moment Moment at First Yield Figure 3-83: Effect of Compression Flange Slenderness (w/o B7) While compression flange slenderness had little effect on either the moment at first yield or the maxim st-peak capacity of these sections. Components B5 and B6 ha compact flanges and exhibited a post-peak cap 0%. um moment sustained, it did have an effect on the po d acity reduction of less than 0.5%. The remaining components, all with non-compact or slender compression flanges, exhibited post-peak capacity reductions of 3% to 1 Also unlike the remaining components, B5 and B6 never exhibited a dramatic unloading prior to the ending of these tests. 171 3.14 Effect of Web Slenderness on Capacity Web slenderness did not effect moment at first yield or ultimate moment for these sections. However, the slender web of B4 had significantly more buckling as eviden by the strain measurements than did the non-compact webs of the remaining componen ced ts. 3.15 Effect of Transverse Stiffener Spacing The presence of transverse stiffeners had no effect on vertical bending capacity. The performance ratios of B2 and B3, components with a stiffened and unstiffened web of identical slenderness, were essentially the same for all conditions. However, the absence of stiffeners on B3 elevated the level of cross-sectional distortion in both the flange and web when compared to the behavior of B2 at similar load levels. 172 Chapter 4. Analytical Results 4.1 Finite Element Model The finite element software ? ABAQUS, Version 6.4 (ABAQUS, 2003) ? was used to conduct the linear-elastic and fully non-linear (geometric and material) analytical studies that were conducted during this research. Girder flanges and webs were modeled using the general-purpose conve e members and the lateral bracing were modeled with B32 beam elements. Figure 4-1 shows a typical undeformed finite element model used in this investigation. Mesh density was chosen based on the recommendation reported in White et al. (2001). Figure 4-2 shows the typical mesh densities used to model the individual members of these investigations. Bending component flanges were modeled with 10 elements across their width. Bending component webs were modeled with 20 elements along their depth. An element aspect ratio of approximately one was maintained along the length of the girder. In general, G1, G2 and G3 had coarser mesh densities. G1 and G2 utilized four elements across a flange and five elements along the depth of a web. G3 used six elements across a flange and 10 elements along the depth of the web. However, mesh densities were increased on all three girder models on elements local to the cross- frame connections. ntional shell element S4R. The cross fram 173 X Y Z Figure 4-1: T ca ite Element Model Used in this S tudyypi l Fin X Y Z r : c ndin mponent Finite Element Mesh Densityg CoFigu e 4-2 Typi al Be 4.1.1 Stress-Strain Relationship Engineering stress-strain relationships were constructed for each of the steel plates used in the fabrication of the bending components. After considering the property test data produced as a part of the CSBRP, a generic stress-strain relationship was developed that was easily tailored to represent the behavior of individual steel plates. An example of the generic seven part linear construction is shown in Figure 4-3. The following process is used to modify this construction to represent individual steel plate properties: 1. Average the static yield strength (? sy ), the offset yield strength (? 0.2% ), the strain at the onset of strain hardening (? st ), the strain hardening modulus (E st ), the tensile strength (? u ) and the strain at the tensile strength (? u ) for all tension test results produced by specimens from a particular steel plate. Table 4-1 cross- references each bending component element to the steel plate from which it was cut. Table 4-2 contains a summary of the average material properties used to construct the stress-strain relationships used by the finite element models for the bending components. Bending Component Compression Flange Plate Number Web Plate Number Tension Flange Plate Number B1 21 8 22 B2 21 9 22 B3 21 10 22 B4 21 11 25 B5 23 12 23 B6 24 13 24 B7 30 8 22 Table 4-1: Cross-reference of Steel Plate Number and Bending Component Element 176 %2.0 ? sy ? st ? st u E ? u ? Steel Plate Number MPa MPa % GPa % MPa 8 460.1 445.4 1.978 3.110 16.38 592.2 9 405.5 393.6 1.941 3.195 16.11 530.3 10 407.8 396.3 2.171 3.149 16.87 540.6 11 457.8 445.2 2.182 2.901 16.51 584.6 12 455.6 439.6 2.089 3.050 15.17 585.6 13 454.8 439.7 2.044 2.995 16.72 584.6 21 425.1 408.5 1.472 4.170 15.88 582.6 22 417.4 406.9 1.711 3.775 16.18 575.2 23 405.2 395.0 1.632 4.111 16.11 570.4 24 401.1 388.1 1.704 3.695 16.68 558.5 25 404.4 390.5 1.753 3.984 16.60 564.7 30 390.2 378.3 1.291 3.422 12.36 530.5 Table 4-2: Average Steel Plate Properties for Selected Steel Plates 2. Use the averaged results, a Young?s modulus (E) of 204 GPa (29,600 ksi) and the functional relationships in Table 4-3 to construct a specific engineering stress-strain curve for each steel plate. 177 Strain 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 St r ess (M Pa) 0 200 0 400 500 600 3 4 5 neering Stress-Strain Relationship Used by FE Model Stress (MPa) 6 7 1 2 3 0 100 Figure 4-3: Typical Engi Point Strain 1 E sy ? sy ? 2 st ? sy ? 3 ( ) () sy stust E ? ?? + 10 ? st stu ? ?? + ? 10 4 ( ) () 3 36 3 36 7 ? 2 ?? + ? 7 4 ? ?? + ? 5 ( ) 4 36 7 2 ? ?? + ? () 4 36 7 2 ? ?? + ? 6 ( ) () 10 stu u ?? ? ? ? st E? ?? %2.0 stu u sy ?? ? ? ? ? ? ? ? ? ? ? 100 7 u ? u sy ? ? ? ? ? ? ? ? ? ? ? %2.0 Table 4-1: Equations Used to Establish Typical Stress-Strain Relationships for the FE Model 178 The Young?s modulus that was used to determine the yield strain for Point 1 of the curve, ? eng ,1 , of the finite-element model?s stress-strain relationship was 204 GPa (29,600 ksi). As reported in hat were preformed determined an average modulus of 204.7 GPa (29,700 ksi) for the steels used in these exp m andard deviation of 0.6 GPa (87 ksi) which is ver ,700 rmined from tension and com s a much larger standard deviation than the modulus determined using the more accurate Young?s modulus test. After all of these results were reviewed, a Young?s modulus of 204 GPa (29,600 ksi) was chosen for use in all analytical efforts throughout this report. The tension testing that was conducted as a part of this study was done in accordance wit ctural Stability Research Council?s (SSRC) Technical Memorandum No. 7 to produce static yield strengths. The SSRC procedure eliminates any effect that strain-rate may have on the demonstrated yield strength of the material. In general, strain-rate affected the yield strengths of the plate steels used in this tudy by elevating their values by approximately 2%. This result was determined by comparing the static yield strength values to the offset yield strength values for individual tests. Analyses of the tension test data did not support the determination of any functional relationship between strain-rate and its effect on yield strength. Therefore, demonstrated tensile strengths, ? u , were also scaled by the ratio of associated static to offset yield Appendix A, the Young?s modulus tests t eri ents. This result has an associated st y small. The Young?s modulus for these steels was also determined during the tension and compression testing. These results are 201.5 GPa (29,200 ksi) and 204.5 GPa (29 ksi) respectively. The Young?s modulus that was dete pression testing is slightly lower and ha h the ASTM E8 standard except that it was modified by the Stru s 179 strength in an attempt to eliminate the strain-rate effect from the stress-strain model. This adjustment is detailed in the calculation for the engineering strain at Point 7, ? eng ,7 , in Table 4-1. The relationships for Points 1, 2 and 7 on the engineering stress-strain model are taken directly from the summary record of the tension tests. Points 3 and 6 also utilize information from the summary record; however, the strain step that was indicated was selected to best capture the general shape of the family of A572 tension test records. The stress and strain relationships for Points 4 and 5 were also selected to best capture the general shape of the tension test records and to rely on coordinate calculations from else odel. The engineering stress-strain curves were converted to true stress-stain curves for use by the finite element program using the following relationships that are derived in Appendix A: where in the m )1ln( engtrue ?? += Equation 4-1 )1( engengtrue ??? += Equation 4-2 A comparison between an engineering stress-strain model and its true stress-strain conversion is shown in Figure 4-4. 180 Strain (?e) 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 S t ress (M P a ) 100 200 300 500 600 700 400 0 Engineering Stress-Strain True Stress-Strain e Stress-Strain Figure 4-5 shows the family of tension and compression test results for material testing that were performed on samples taken from Plate 21 (see Appendix A for a description of this plate) in terial model. These results are shown on a field of engineering stress and strain. The test results differ slightly, with lower strengths displayed by compression test results, due to the specimen necking or barreling that is inherent to each respective test method. Figure 4-4: Engineering Versus Tru addition to the constructed ma the tension test results and higher strengths by the 181 Engineering Strain -0.05 0.00 0.05 0.10 0.15 0.20 0.25 0.30 E ngine S t ress (MPa ) 0 200 800 Compression Tests Tension Tests 600 400 erin g Engineering Stress-Strain Model Figure 4-5: Plate 21 Compression and Tension Test Results Compared with the FE Material engineering stress-strain to ferences in behavior become insignificant. Figure 4-6 shows the same family of Plate 21 results after conversion to true stress-strain. Once converted, the tension and compression test results essentially overlay each other, as shown in Figure 4-6. This figure supports the widely accepted material behavior model for steel with respect to tensile and compressive stress. The tension and compression test results established, a separate material model is not needed to account for the stress-strain behavior of these Model in Engineering Stress-Strain However, when the tension and compression test results are converted from true stress-strain the dif refore, with the agreement between 182 steels in the compression domain. All material properties used in any associated analytical efforts will be drawn from the tension test results. Strain -0.05 0.00 0.05 0.10 0.15 0.20 0.25 T r ue St re ss (MP a ) 0 200 400 600 800 Compression Tests Tension Tests True Stress-Strain Model Figure 4-6: Plate 21 Compression and Tension Test Results Compared with the FE Material Model in True Stress-Strain 4.1.2 As-Built Geometry Prior to testing, the flanges and web of each bending component were measured at regular intervals for width or depth, and thickness. Six sets of measurements were taken alon e lo ations 6L and 6R. The numbers reported in Table 4-2 are the averages for the center four sets of those measurements. A decision was made to use these measurements for the analytical model because this middle section was the location of failure in all of the experiments. g each component between cross-fram c 183 b f t f Dt w b f t f (mm) (mm) (mm) (mm) (mm) (mm) B1 443.7 19.5 1210.7 8.2 444.5 19.4 B2 442.9 19.4 1211.9 10.1 442.9 19.4 B3 442.9 19.5 1213.4 10.2 444.5 19.4 B4 442.9 19.4 1212.4 8.1 533.4 32.4 B5 419.1 24.7 1215.2 8.5 419.9 24.6 B6 414.4 30.9 1213.6 8.6 413.9 31.0 B7 533.4 16.4 1215.2 8.4 444.5 19.2 Bending Component Compression Flange Web Tension Flange Table 4-2: Bending Specimen As-Built Plate Dimensions The thickness measurements were made with an ultrasonic device. The device employed had a 12.7mm (? in.) diameter transducer. Three individual thickness measurements were taken at each measurement location. During each successive me previous measurement. The echeck the calibration. The width and depth measurements were made using a steel tape that was scaled in U.S. Customary units. All pieces of the test frame had their dimensions measured and recorded in the same manner that was used for the bending components. These measurements have been summarized by Linzell (1999). 4.1.3 Installation Strains The installation strains that were recorded during the erection of each bending component and that were used in the analysis of the experimental data (discussed in Chapter 3) were not utilized to refine the predictions of the analytical model. Although these strains do exist and were captured for the mid-span section of each component, not asurement, the transducer partially covered the area used in the device had an integrated platen that was regularly used to r 184 enough information was obtained to determine their distribution along the length of each component to appropriately model their effects. 4.1.4 Modeling of Residual Stresses The fabrication process to construct I-girders from steel plates requires both flame cutting and welding. In the areas adjacent to the application of these processes, sufficient thermal stresses are created to plastically deform the steel plate. The steel is affected by the heat, and as it cools its elastic recovery is constrained by cooler portions of the plate. The elastic recovery and constraint compete until an equilibrium of internal stress is achieved. This remaining internal stress profile is referred to as residual stress because it is a consequence of either the cutting or welding process. Several researchers have attempted to measure residual stresses. The sectioning method, which is employed most often, requires careful monitoring of changes in the strain profile throughout a cross-section of a plate as a portion or section of that plate is rem tes. For he ebs that were subjected to both flame cutting and welding. Each plate modeled is divided into zones of tension and compression. The heat affected zones from flame cutting or welding are modeled as small regions of uniform high tensile stress. The remainder of the plate is considered to be at a constant compressive stress level of necessary scale to equilibrate the aggregate tensile stresses. oved. These studies along with many analytical efforts have resulted in the publication of several residual stress models for I-girders fabricated from steel pla this investigation, residual stress predictions are made using the recommendations of t European Convention for Constructional Steelwork (ECCS, 1976). The ECCS method includes residual stress models for flanges and w 185 The ECCS procedure specifies the equivalent rectangular tension block width, c f , adjacent to a flame cut plate edge as: y F where: f c = 4-3 t = plate thickness (mm) F y = plate yield strength (MPa) For single pass welds, the ECCS procedure specifies an equivalent rectangular tension block width, c w , for each plate joined at that weld of: t1100 Equation ? = )( )(12000 tF Ap c y w w Equation 4-4 where: p = efficiency factor (0.9 for the submerged arc welding process) w = etal (mm 2 ) simultaneously at the top and bottom of one side of the web during the fabrication of the bending components. This method of fabrication resulted in the web-to-flange fillet welds being placed on opposite faces of the web at different times. In the flange plate, both of the consecutive welds both slightly lowered the residual tensile stresses caused at each flange tip by the flame cutting process. Also, this two?step welding procedure lowered the level of residual stress at the weld location because the heat input from the second weld relieved the tensile stresses A cross-sectional area of weld m F y = plate yield strength (MPa) ? t = sum of plate thicknesses meeting at the weld (mm) The web-to-flange fillet welds were placed 186 cre method, the resulting equivalent stress block for the two welds placed consecutively and spaced d mm apart is given by: Equation 4-5 where: c = equivalent tension block width of a single pass or weld (mm) d ? 2c In the web plate, the residual stresses of the flame cut edge are partially relieved by both the first and second welds. In addition, the residual stresses from the first weld are partially relieved by the heat input of the second weld. To account for this combination of effects, the ECCS method suggests that the combined tension block width created by welding and flame cutting, c fw , is approximated by the following relationship: Equation 4-6 where: c f = equivalent tension block width created by flame cutting (mm) c w = equivalent tension block idth due to welding (mm) The ECCS method also includes a predictor for the final tension block width produced by multi-pass welds or superimposed welds of equal size. Equation 4-7 where: c = equivalent tension block width of a single pass or weld (mm) n = number of weld passes or superimposed welds of equal size The residual stress profiles that resulted from flame cutting and welding were determined for each flange and web of the bending components using equations 4-3 ated by the first weld. According to the ECCS dcc 5.0 2 += 444 wffw ccc += w 4/1 cnc n = 187 through 4-6. The equivalent widths of the rectangular tension block do not match the element size of the finite element model. Therefore, net element stresses were also det of a flange and to each of the 20 elements along the depth of a web. The results of these calculations for each com ending components are compiled in Tables 4-3 through 4-5. MPa) B1 374.2 11.9 56.7 408.5 34.4 121.7 -59.5 B2 363.9 11.9 56.7 408.5 33.4 119.3 -57.8 11.9 -60.1 B6 346.1 15.8 96.1 388.1 26.7 85.8 -59.6 B7 338.5 11.8 37.2 378.3 40.7 114.4 -49.8 Component Tension at Each Flange Tip Tension at Welds Compression ermined to apply to each of the 10 elements across the width pression flange, web and tension flange of the b Resultant Width Net per Element Resultant Width Net per Element (MPa) (mm) (MPa) (MPa) (mm) (MPa) ( B3 364 11.9 56.8 408.5 33.4 119 -57.7 B4 362.7 55.5 408.5 34.5 124.3 -59 B5 350.6 13.8 76.9 395 30.9 106.4 ble 4-3: Compression Flange Plate Residual Stresses et per Element (MPa (mm) (MPa) (MPa) (mm) (MPa) (MPa) B1 445.4 31.9 221.3 445.4 31.9 221.3 -24.8 B2 393.6 34.5 212.4 393.6 34.5 212.4 -23.8 B3 396.3 34.2 211.9 396.3 34.3 212.6 -23.7 B4 445.2 32 223.6 445.2 23 154.8 -21.2 B5 439.6 27.7 188.2 439.6 27.8 189 -21.1 B6 439.7 24 162.1 439.7 23.9 161.4 -18.1 B7 445.4 35.2 246.2 445.4 32.1 222.2 -26.1 Component Tension at Top of Web Tension at Bottom of Web Compression Ta Resultant Width Net per Resultant Width N Element ) Table 4-4: Web Plate Residual Stresses 188 104.4 -61 B6 361.5 15.8 100.1 388.1 26.6 83 -61.1 397.3 11.1 55.1 431.9 33 123 -59.4 Component Tension at Each Flange Tip Tension at Welds Compression Resultant Width Net per Element Resultant Width Net per Element (MPa) (mm) (MPa) (MPa) (mm) (MPa) (MPa) B1 397.5 11.2 56 431.9 32.8 121.9 -59.3 B2 398.4 11.2 57.3 431.9 31.9 118 -58.5 B3 398.5 11.2 57.2 431.9 31.9 117.5 -58.2 B4 370.7 16 79.2 390.5 25.7 59.1 -46.1 B5 364.1 13.8 78.8 395 30.5 B7 Typical residual stress profiles for a flange and web are shown in Figures 4-5 and 4-6. These figures illustrate profiles that represent both the resultant residual stresses determined using the ECCS method for flame cutting and welding and the net residual stre analytical model. Table 4-5: Tension Flange Plate Residual Stresses sses determined to apply to individual elements that make up each flange or web of the 189 Flange Width (mm) 0 100 200 300 400 Re sid u a l S t re ss (MPa ) -100 0 100 200 300 400 500 Net Per Element Resultant Figure 4-7: Example Flange Plate Residual Stress Profile Residual Stress (MPa) 100 0 100 200 300 400 50 W eb Depth ( mm) 0 200 400 600 800 1200 1000 Net Per Element Resultant ofile Figure 4-8: Example Web Plate Residual Stress Pr 190 4.1.5 Modeling of Boundary Conditions Reactions were modeled using a gap element that prevented vertical deflection but allowed lift-off. These elements incorporate a frictional resistance to horizontal translation that was set at the experimentally determined frictional coefficient for the actual bearings. Reactions under G1 and G3 were free to translate in any horizontal direction while the G2 reactions allowed only tangential translation as they were fixed radially. All reactions allowed rotation about the point of support. The loads were applied to the top flange of all three girders as a point load at the appropriate node. Early results were scrutinized to insure that this method of applying load did not cause any local instability. A tangential support frame was attached to the west end of the experimental test frame as a safety precaution. This fram was mounted to the floor of the structural laboratory and was attached to the test frame with a large cotter pin. The pin passed through one side of a double gusset plate that was attached to the tangential support fram and finally through the other side of the tangential support frame?s double gusset. This structure was intended to prevent the test frame from a global translation off of the bearings. This structure was not modeled in the finite element analyses since the strain readings recorded during each test indicated that it was never engaged. 4.1.6 Predictions kness and width of the steel plates used in the fabrication of the test frame and bending components. However, with the exception of B7, the finite element models predicted less component mid-span e e, then through an oversized slot in the G2 web A diligent effort was made to account for the variation in thic 191 moment due to self-weight than what was measured during the tests. These results are not uncommon, especially on a large structure in which the weight of weld metal, bolts, nuts, washers, instrumentation etc. cannot be dismissed as insignificant. Also, the gusset plates, con quately incorporated in the finite element models for the software to predict a representative weight. Regardless, the self-weight moment predictions were within 5% of the measured values for all components except for B1 and B2. The prediction for B1 dramatically departed from the measured value by a reduction of 17%. A review of the experimental test log and other test documentation, as well as a careful review of the finite element model provide no explanations as to why this difference is so great. However, this difference did not adversely affect the flexural capacity analysis for B1 that is presented in Section 4.1.6.1. The predicted self-weight moment for B2 was 7% less than that deduced from the measured strains. This difference is acceptable and had no effect on the flexural capacity ana ted self-weight moment for B7 was greater than that generated from the strain measurements by 5%. This difference is not alarming, and is only of interest because it is an over prediction that is contrary to the displayed and expected trend. It is however an indication that all force-actions were not properly accounted for prior to the applied loading portion of this test. Also, with B6 as the only exception, the finite element models predicted a greater maximum applied load than what was measured during the experiments. This additional applied load accounted for the differences in self-weight and installation effects between nections and stiffening on each of the cross-frames are not ade lysis of this component (similar to B1). The predic 192 the predicted vertical moment capacities considered the influences of residual stress but were primarily the result of self-weight and applied load. The experimental data contains measurements of strain associated with self-weight, installation and applied load. Regardless of what combination of loads caused the maximum mid-span moment, the measured and predicted flexural resistance of the bending components were virtually the same for all bending components with the exception of B7. 4.1.6.1 B1 Finite Element Model Results The finite element model of the B1 component test predicted a maximum sustainable applied load of 1532.3 kN. This load equated to a mid-span moment of 3726.3 kN-m. When combined with the self-weight effects the predicted maximum mid-span moment resisted by B1 was 4573.9 kN-m which is comparable to the measured maximum mid- span resisted moment of 4539.2 kN-m. These results are summarized in Table 4-6. predictions and the experimental data in most of the analyses. That is, the finite element model Test FE Ratio (a) (b) (b)/(a) Max. Applied Load (kN) 1353.5 1532.3 1.13 Mid-Span Moment Self-Weight (kN-m) 1022.2 847.6 0.83 Installation (kN-m) 536.8 Max. Applied Load (kN-m) 2980.2 3726.3 1.25 Flexural Resistance (kN-m) 4539.2 4573.9 1.01 B1 Table 4-6: B1 Test and Finite Element Model Results Figure 4-9 shows the effect of the applied loads on the G1, G2 and B1 mid-span moments from both the experimental test and the finite element model. The predictions match the physical results very well indicating that the load is being distributed as expected within the load frame. 193 0 500 1000 1500 2000 2500 M d- M ment ( k N- m) i Span o 0 2000 4000 6000 1000 3000 5000 G1 Test G1 FE G2 Test G2 FE B1 Test B1 FE Total Applied Load (kN) Figure 4-10 shows the B1 mid-span moment from the applied loads normalized with yield finite element model and the experimental data. The test results fall short of the predicted capacity and contain some pre-peak non-linearity. However, the shapes of the curves are very similar. The exhibited and predicted flexural resistance capacities are within 1% once the differences in self-weight and the effects of the recorded installation strains are added to the test results. Figure 4-9: B1 Test Mid-Span Moments and Finite Element Predictions respect to the strong-axis yield moment, M x , as a function of deflection for both the 194 0 100 200 300 400 M/ x yi e l d M 0.0 0.2 0.4 0.8 Deflection (mm) 0.6 1.0 B1 Test B1 FE e 4-7. . t by B2 was 4774.5 kN-m. This amount is comparable to the measured maximum mid Figure 4-10: B1 Mid-Span Moment vs. Deflection 4.1.6.2 B2 Finite Element Model Results A summary of the B2 experimental and finite element results is included in Tabl The finite element model of the B2 component test predicted a maximum sustainable applied load of 1596.8 kN. This load equated to a mid-span moment of 3910.8 kN-m When combined with the self-weight effects the predicted maximum mid-span momen resisted -span resisted moment of 4729.6 kN-m. 195 Test FE Ratio Max. Applied Load (kN) 1432.3 1596.8 1.11 (a) (b) (b)/(a) Mid-Span Moment Self-Weight (kN-m) 928.0 863.6 0.93 Installation (kN-m) 536.8 Max. Applied Load (kN-m) 3264.7 3910.8 1.20 Flexural Resistance (kN-m) 4729.6 4774.5 1.01 B2 Table 4-7: B2 Test and Finite Element Model Results Figure 4-11 shows the effect that the applied loads had on the mid-span moments of G1, G2 and B2 from both the experimental test and the finite element model. The predictions match the physical results very well indicating that the load is being distributed as expected within the load frame. Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d- Span M o ment ( k N- m) 0 1000 2000 3000 4000 6000 G1 Test G1 FE G2 Test 5000 G2 FE B2 Test B2 FE Figure 4-11: B2 Test Mid-Span Moments and Finite Element Predictions 196 Figure 4-12 shows the normalized B2 mid-span moment from the applied loads as function a of deflection for both the finite element model and the experimental data. The test ever, the shapes of the curves are very similar. The exhibited and results fall short of the predicted capacity and contain a greater degree of pre-peak non-linearity. How predicted flexural resistance capacities are within 1% once the difference in self-weight and the recorded installation strains are added to the test results. Deflection (mm) 0 100 200 300 400 M/ e l d 0.0 1.0 B2 Test B2 FE 0.6 0.8 M x yi 0.2 0.4 Figure 4-12: B2 Mid-Span Moment vs. Deflection 197 inite Element Model Results mum mid-span moment resisted by B3 was 4778.0 kN- nt of 483 ent res 4.1.6.3 B3 F The B3 finite element model predicted a maximum sustainable applied load of 1598.2 kN which resulted in a mid-span moment of 3904.6 kN-m. When combined with the self- weight effects the predicted maxi m. This moment is comparable to the measured maximum mid-span resisted mome 4.4 kN-m. Table 4-8 contains a summary of the B3 experimental and finite elem ults. Test FE Ratio Max. Applied Load (kN) 1499.9 1593.2 1.06 Mid-Span Moment Self-Weight (kN-m) 922.2 873.4 0.95 (a) (b) (b)/(a) Installation (kN-m) 536.8 0.0 Max. Applied Load (kN-m) 3375.4 3903.3 1.16 Flexural Resistance (kN-m) 4834.4 4776.7 0.99 B3 Table 4-8: B3 Test and Finite Element Model Results Figure 4-13 shows the effect that the applied loads had on the m id-span moments of odel. The figure indicates that the finite elem of load within the te the experiment. the test frame girders from both the B3 experimental test and the finite element m ent model is accurately predicting the distribution st frame and that the pre-peak behavior prediction agrees well with 198 Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d-S pan M o ment (kN-m ) 0 1000 2000 3000 4000 5000 6000 G1 Test G1 FE G2 Test G2 FE B3 Test B3 FE Figure 4-13: B3 Test Mid-Span Moments and Finite Element Predictions Figure 4-14 shows the normalized B3 mid-span moment from the applied loads as a function of deflection for both the finite element model and the experimental data. The experimental results indicate that the component was initially stiffer than the predicted behavior. The test results cross the prediction curve prior to the predicted maximum capacity and return to the prediction curve again in the post-peak field of behavior. However, the analytical results predict a severe post-peak capacity drop that was not captured during the physical test. After adjusting for the difference in self-weight and the recorded installation effects, the results are within 1% of the predicted flexural capacity. 199 Deflection (mm) 0 100 200 300 400 M/ M x e l d yi 0.0 0.4 0.6 0.8 0.2 1.0 B3 Test B3 FE 9. t test. This load equated to a mid-span moment of 3790.7 kN- m. eight effects the predicted maximum mid-span mom Figure 4-14: B3 Mid-Span Moment vs. Deflection 4.1.6.4 B4 Finite Element Model Results A summary of the B4 experimental and finite element results is included in Table 4- A maximum sustainable applied load of 1475.4 kN was predicted by the finite element model for the B4 componen When combined with the self-w ent resisted by B4 was 4718.3 kN-m is comparable to the measured maximum mid- span resisted moment of 4879.7 kN-m. 200 Test FE Ratio (a) (b) (b)/(a) Max. Applied Load (kN) 1354.4 1475.4 1.09 Mid-Span Moment Self-Weight (kN-m) 960.7 927.6 0.97 Installation (kN-m) 696.0 0.0 Max. Applied Load (kN-m) 3223.1 3790.7 1.18 Flexural Resistance (kN-m) 4879.7 4718.3 0.97 B4 Table 4-9: B4 Test and Finite Element Model Results Figure 4-15 shows the effect that the applied loads had on the mid-span moments of G1, G2 and B2 from both the experimental test and the finite element model. The predictions match the physical results very well prior to the failure of B4, indicating that the model is accurately accounting for the actual physical behavior. Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d- Span M o ment ( k N- m) 0 1000 2000 3000 4000 5000 6000 G1 Test G1 FE G2 Test G2 FE B4 Test B4 FE Figure 4-15: B4 Test Mid-Span Moments and Finite Element Predictions 201 202 Figure 4-16 shows the normalized B4 mid-span moment from the applied loads as a function of deflection for both the finite element model and the experimental data. The test results fall short of the predicted capacity and contain some pre-peak non-linearity. However, the shape of the curves is very similar, and when the test resu difference in self-weight and the recorded installation effects the exhibited and predicted flexural resistance capacities are within 3%. Deflection (mm) 0 100 200 300 400 Figure 4-16: B4 Mid-Span Moment vs. Deflection B5 Finite Element Model Results odel of the B5 test predicted a maximum sustainable applied oment of 4361.3 kN-m at mid-span of the 4.1.6.5 The finite element m load of 1742.7 kN, which produced a m M/ M x yi e l d 0.0 0.2 0.4 0.6 0.8 1.0 B4 Test B4 FE lts include the component. When combined with the self-weight effects the predicted maximum mid- span moment resisted by B5 was 5255.2 kN- e as the easured maximum mid-span resisted moment of 5278.1 kN-m. A summary of the B4 experimental and finite element results is included in Table 4-10. m. This result is essentially the sam m Test FE Ratio (a) (b) (b)/(a) Max. Applied Load (kN) 1732.5 1742.7 1.01 Mid-Span Moment Self-Weight (kN-m) 896.9 893.9 1.00 Installation (kN-m) 511.9 0.0 Max. Applied Load (kN-m) 3869.3 4361.3 1.13 Flexural Resistance (kN-m) 5278.1 5255.2 1.00 B5 T Figure 4-17 shows the effect that the app ents of 1, G2 and B2 from both the experimental test and the finite element model. The predictions match the physical results very well early in the loading regime and maintain the same characteristic shape throughout the figure. able 4-10: B5 Test and Finite Element Model Results lied loads had on the mid-span mom G 203 Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d- Span M o ment ( k N- m) 0 1000 2000 3000 4000 5000 6000 G1 Test G1 FE G2 Test G2 FE B5 Test B5 FE Figure 4-17: B5 Test Mid-Span Moments and Finite Element Predictions Figure 4-18 shows the normalized B1 mid-span moment from the applied loads as a function of deflection for both the finite element model and the experimental data. The test results fall short of the predicted capacity and contain additional pre-peak non- linearity. However, the shapes of the curves are very similar. When the test results are include the difference in self-weight and the recorded installation effects, the exhibited and predicted flexural resistance capacities are nearly identical. 204 Deflection (mm) 0 100 200 300 400 M/ M x yi e l d 0.0 0.2 0.4 0.6 0.8 1.0 B5 Test B5 FE Figure 4-18: B5 Mid-Span Moment vs. Deflection 4.1.6.6 B6 Finite Element Model Results A summary of the B6 experimental and finite element results is included in Table 4- 11. The finite element model of the B6 component test predicted a maximum sustainable applied load of 2038.5 kN. This load equated to a mid-span moment of 5319.3 kN-m. When combined wi id-span moment sisted by B6 was 6257.8 kN-m. This result is comparable to the measured maximum mid-span resisted m th the self-weight effects the predicted maximum m re oment of 6399.5 kN-m. 205 Test FE Ratio (a) (b) (b)/(a) Max. Applied Load (kN) 2071.4 2038.5 0.98 Mid-Span Moment Self-Weight (kN-m) 951.5 938.5 0.99 Installation (kN-m) 561.8 0.0 Max. Applied Load (kN-m) 4886.2 5319.3 1.09 Flexural Resistance (kN-m) 6399.5 6257.8 0.98 B6 Table 4-11: B6 Test and Finite Element Model Results The effect that t e test frame girders during the B6 test from both the experimental data and the finite element model results are shown in ity for B6 is ightly more dramatic than the measured behavior. However, the predictions match the physical results very well for the mid-span test frame cross-section. he applied loads had on the mid-span moments of th Figure 4-19. The predicted post-peak drop in capac sl Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d- Sp an M o m e nt ( k N - m) 0 1000 2000 3000 4000 5000 6000 G1 Test G1 FE G2 Test G2 FE B6 Test B6 FE Figure 4-19: B6 Test Mid-Span Moments and Finite Element Predictions 206 Figure 4-40 shows the normalized B6 mid-span moment from the applied loads as a function of deflection for both the finite element model and the experimental data. The test results again fall short of the predicted capacity. However, the prediction curve matches the measured behavior through the elastic range and maintains a very similar shape pre- and post-peak. When the B6 test results are amended for the difference in self- weight and the recorded installation effects, the exhibited and predicted flexural resistance capacities are within 2%. Deflection (mm) 0 100 200 300 400 M/ M x yi e l d 0.0 0.2 0.4 0.6 0.8 1.0 B6 Test B6 FE Figure 4-40: B6 Mid-Span Moment vs. Deflection 207 4.1.6.7 B7 Finite Element Model Results Table 4-12 contains a summary of the B7 experimental and finite element results. The B7 finite element model predicted a maximum sustainable applied load of 1269.9 kN. This load equated to a mid-span moment of 3138.1 kN-m. When combined with the self- weight effects the predicted maximum mid-span moment resisted by B7 was 3993.3 kN- m. This result is a significant over-strength, compared with the measured maximum mid- span resisted mome /(a) Max. Applied Load (kN) 1095.5 1269.9 1.16 Mid-Span Moment Self-Weight (kN-m) 811.8 855.2 1.05 Installation (kN-m) 190.4 0.0 Max. Applied Loa nt of 3503.4 kN-m. Test FE Ratio (a) (b) (b) B7 d (kN-m) 2501.1 3138.1 1.25 Flexural Resistance (kN-m) 3503.4 3993.3 1.14 Table 4-12: B7 Test and Finite Element Model Results The effect that the applied loads had on the mid-span moments of G1, G2 and B7 from both the experim he predictions match the physical results very well early in the loading regime indicating that the finite element model adequately forecasts the elastic behavior of the test frame. ental test and the finite element model are shown in Figure 4-41. T 208 Total Applied Load (kN) 0 500 1000 1500 2000 2500 M i d- Span M o ment ( k N- m) 0 1000 2000 3000 4000 5000 6000 G1 Test G1 FE G2 Test G2 FE B7 Test B7 FE Figure 4-41: B7 Test Mid-Span Moments and Finite Element Predictions Figure 4-42 shows the normalized B7 mid-span moment from the applied loads as a function of deflection for both the finite element model and the experimental data. Although the overall shape of the prediction and experimental curves remains similar throughout the figure, the experimental data indicate a significant early stiffness difference and, later, a failure of the section well short of the predicted peak. These ifferences are most likely due to the nature in which B7 was fabricated and the inability to quantify these differences and incorporate them into the model. This resulted in fully analyzed test result self-weight and recorded installation effects that are nearly 14% less than predicted. d s for flexural resistance that include the difference in 209 In addition to the fabrication issues that affected the performance of B7, it is difficult for any general purpose finite element program to predict the onset of local buckling for slender plates such as the top flange of this specimen. These slender sections are sensitive to geometric imperfections that were not a part of this analytical study. White et al. (2001) modeled B7 with and without estimates for geometric imperfections. Their results without the geometric imperfection estimates were very similar to those in this study. Their results including the geometric imperfection estimates matched the physical test results much more employs odeling very similar to that used by White et al. (2001), a similar correction in behavior is expected with the 7 model. closely; the results are within 4%. Because this study m incorporation of geometric imperfections into the B Deflection (mm) 0 100 200 300 400 M/ M x yi e l d 0.0 0.2 0.4 0.6 0.8 1.0 B7 Test B7 FE Figure 4-42: B7 Mid-Span Moment vs. Deflection 210 m linear-elastic behavior. 211 4.2 AASHTO Guide Specification Predictions Bending capacities for each of the bending components can be determined using the provisions of the Guide Specifications. These provisions, which are summarized in Appendix B.1, utilized the vertical bending stress, f b , and the lateral flange bending stress, f l , results of a 1 st order analysis to determine a maximum strong-axis flexural resistance. The 1 st order analysis used in this report was generated with the same finite element odel that was used for the fully non-linear analysis. However, the model was limited to Table 4-13 includes the vertical bending capacities, M n , as determined by the Guide Specifications (example calculations to demonstrate how these numbers were generated are included in Sections 4.1.1 and 4.1.2), and a summary of the experimental results for these sections, M x test , as reported in Chapter 3. A performance ratio that is produced by normalizing the capacity of the Guide Specificatio ental results is listed in the far right column of Table 4-13. A statistical summary of the normalized performance ratios is shown in the n. The average performance ratio was 0.71, or owever, this average was associated with a rather large standard deviation of 0.15 or 21% of the mean, indicating a very poor consistency of prediction. The range of results extended from 9% conservative to 43% conservative. ns by the experim roughly 29% conservative. H box just under the far right colum 212 Component M n From f l /f b From M x test M n/ M x test Guide 1st Order Specifications Analysis (kN-m) (kN-m) B1 2702 0.32 4339 0.62 B2 2778 0.33 4730 0.59 B3 2748 0.36 4834 0.57 B4 2900 0.31 4880 0.59 B5 4790 0.32 5278 0.91 B6 5649 0.31 6400 0.88 B7 2775 0.29 3503 0.79 Average 0.71 Std. Dev. 0.15 Maximum 0.91 Minimum 0.57 Guide Specifications Flexural Capacities and Statistics lations illustrate the use of the Guide Specifications for determining the flexural resistance of a non-compact compression flange section and of a compact compression flange section. These calculations are usually an iterative process. The las ration of this process is presented in Section 4.1.1 for brevity. 4.2.1 Non-Compact Compr on Flange Example Bending component B1 was chosen for these example calculations. ? B1 properties F yc = yield stress of the compression flange = 408.5 MPa F yw = yield stress of the web = 445.4 MPa L b = unbraced arc length of the flange = 4772 mm R = minimum girder radius within the panel = 63,630 mm b fc = compression flange width = 443.7 mm D = web depth = 1211 mm Table 4-13: Summary of The following two sets of example calcu t ite essi D c = depth of web in compression = 604.9 mm 6 3 st st flan t fc = compression flange thickness = 19.48 mm t w = web thickness = 8.230 mm S xc = section modulus referred to the compression flange = 12.41x10 mm f l1 = 1 order analysis lateral flange bending stress = 69.64 MPa f bu = 1 order analysis flange stress from vertical bending = 217.6 MPa ? Check flange compactness B1 was designed to be non-compact. To be defined as non-compact, the compression ge must meet the following criterion: () 2302.1 1 ?? lbufc fc E b + fft () 2.27 64.696.217 204000 02.18.22 48.19 7.443 = + ?== fc t b fc 238.22 ?= fc t Therefore, the flange is non-compact. fc b ? Solve for the critical flange stress, The critical flange stress is the lesser of a flange stress that, when amplified with the ? -factors, will cause lateral torsional buckling in unbraced length, or the flange yield strength reduced by the lateral flange bending stress. The lateral torsional buckling stress is: cr F ? ? ? ? ? ? ? ? ? ? ?= F L FF yc b ycbs 2 31 ?? ?? ?? Eb fc 2 9.0 ? 213 ()() MPaF 0.373315.408 =???= bs 204000 5.408 7.4439.0 4772 2 2 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? The non-compact flange ? -factors are: fc bb b L R L + = 1 1 ? b 554.0 7.443 4772 630,63 4772 1 = ? ? ? ? ? ? 1 ? ? ? ? ? ? + = b ? ? ? ? ? ? ? ?? = fc b bu l w bf 75 11 1 1 1 ? ?? Lf () 378.1 7.44375 4772 1 64.69 1 1 ? ? ? ? ? ? ?? w 6.217 = ?? =? 1 ? ? ? ? ? ? ? ? + ?? = bu w f R 2 6.01 ? ? ? ? ? l b fc f L 1 2 1.0000,830 ? + + b b L 95.0 055.1 6.217 64.69 6.01 630,63 4772 1.0000,830 7.443 4772 95.0 2 2 = ? ? ? ? ? ? + ? ? ? ? ? ? ?+ + = w ? 0 1 ? bu l f f , ( ) 055.1,min 21 == www ??? . Because 214 215 Having determined the ? -factors, solve for the critical flange stress. wbbscr FF ??= 1 ()()() MPaF cr 0.218055.1554.00.373 1 == lycr fFF ?= 2 MPaF cr 9.33864.695.408 2 =?= () MPafiFFF bcrcrcr 6.2170.218,min 21 =?== ? Check the web stress criterion k = bend-buckling coefficient = 2 0.9 ? ? ? ? ? ? ? ? c D D 07.36 9.604 1211 0.9 2 = ? ? ? ? ? ? =k () yw w cr F t D Ek webF ? ? ? ? ? ? ? ? ? = 2 9.0 (()) MPaweb 9.305 230.8 1211 07.362040009.0 ) 2 = ? ? ? ? ? ? = Because the critical web stress, 305.9 MPa (44.367 ksi) is greater than the vertical bending stress in the section 217.6 MPa (31.560 ? Determine the equivalent vertical bending moment n M = F cr ( xcbu Sf ( ) mkNmmNxxM n ?=?== 27001027001041.12 66 6.217 ksi) the web condition is acceptable. 216 Please refer to Table 4-17 to see how this capacity compares to the experimental measurement. 4.2.2 Compact Compression Flange Example Bending component B5 was chosen for these example calculations. ? B5 properties F yc = compression flange yield strength = 395.0 MPa F yw = web plate yield strength = 445.2 MPa L R inimum girder radius within the panel = 63,630 mm b pression flange width = 419.1 mm D t fc pression flange thickness = 24.66 mm t w S odulus referred to the compression flange = 14.56x10 6 mm 3 f l1 st order analysis lateral flange bending stress = 105.3 MPa f bu = 1 st order analysis flange stress from vertical bending = 329.0 MPa ? Check the flange compactness B5 was designed to have a compact compression flange. To be defined as compact, the compression flange must meet the following criterion: b = unbraced arc length of the flange = 4772 mm = m fc = com = web depth = 1215 mm c = depth of web in compression = 607.3 mm = com = web thickness = 8.458 mm xc = section m = 1 D 18? fc fc t b ? strength reduced by the lateral flange bending stress. 217 180.17 66.24 1.419 ?== fc fc t b Therefore, the flange is compact. ? Solve for the critical flange stress, cr F The critical flange stress is the lesser of a flange stress that, when amplified with the -factors, will cause lateral torsional buckling in unbraced length, or the flange yield The lateral torsional buckling stress is: ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?= E F b L FF yc fc b ycbs 2 2 9.0 31 ? ()() MPaF bs 8.357 204000 0.395 1.4199.0 4772 310.395 2 2 = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?= ? The compact flange ? -factors are: 2 01.0 6 11 1 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ++ = R L b L b L b fc b fc b b ? () 878 0 630,63 4772 1.4196 4772 1 1.419 4772 1 1 ? ? ? ? ? ? ? ? ? ? ? ? ++ = b ? .0 01. 2 = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? yc bs fc bb F F b L R L 1. ? ? ? ? ? +? ? ? ? ? ? ?+= b bu lb w f f R L ? ? 03.0 1.01895.0 1 2 048.1 0.395 8.357 878.0 630,63 4772 1.03.0 0.329 3.105 630,63 4772 1.01895.0 2 = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? +? ? ? ? ? ? ?+= w ? 1.419 4772 ? ? ? ? ? ? ? ? ? 218 () 0.1920.0048.1878.0 <== wb ?? Having determined the ? -factors, solve for the critical flange stress. wbbscr FF ??= 1 () MPaF cr 2.329920.08.357 1 == 3 1 2 l ycr f FF ?= MPaF cr 9.359 3 3.105 0.395 2 =?= () MPafMPaFFF bucrcr 0.3292.329,min 21cr =>= ? eb stress criterion k = Check the w = bend-buckling coefficient = 2 0.9 ? ? ? ? ? ? ? ? c D D 02.36 3.607 1215 0. 2 = ? ? ? ? ? ? k 9= () yw w F t D Ek F ? ? ? ? ? ? ? ? ? = 2 9.0 () cr web () MPafMPawebF bucr 0.3295.320 458.8 1215 02.362040009. ( 2 =<= ? ? ? ? ? ? pressive stress is less than th the f etermine the vertical bending stress based on the critical web stress. 0 ) = Because the critical web com e vertical bending stress in lange, d bu fcc c cr f tD D ? ? ? ? ? ? ? ? + ?)( webF 219 () MPaMPawebF cr 5.3201.3160.329 66.243.607 3.607 )( <= ? ? ? ? ? ? + ? okay Therefore this design meets the critical web stress criterion. ? Determine the equivalent vertical bending moment xcbun SfM = ( ) mkNmmNxxM n ?=?== 47901047901056.140.329 66 Please refer to Table 4-17 to see how this capacity compares to the experimental measurement. 4.3 Unified Design Method Predictions The estimated capacities derived by using the Unified Design Method for the entire suite of bending components can be seen in the top section of Table 4-14. These capacities, M n ined by using a 1 st order analysis with the suggested lateral flange stre ication factor, and by using a 2 nd lysis. Similar to with the Guide Specification results, each calculated capacity has been normalized by the appropriate experimental result, M x test , from Chapter 3 to pro mance ratios in the far right column of each section of Table 4-14. The lo le contains a statistical summary of the performance ratios for each analysis method. For the 1 st order analysis results, the average performance ratio was 0.85, or roughly 15% conservative. This average was associated with a standard deviation of 0.03 or approximately 4% of the mean. The range of results extended from 10% conservative to 19% conservative. nd order analysis results are very similar to the statistical results for the 1 st order analysis results. The average performance ratio was 0.84 or 16% The statistics for the 2 , have been determ ss amplif order ana duce the perfor wer section of this tab conservative with an ass tightened slightly extending from 220 ociated standard deviation of 0.03 or 4%. The range of results 12% conservative to 18% conservative. Component M x test M n AF(f l /f b )M n/ M x test M n f l /f b M n/ M x test (kN-m) (kN-m) (kN-m) B1 4339 3908 0.37 0.90 3835 0.33 0.88 B2 4730 4022 0.38 0.85 3944 0.34 0.83 B3 4834 4006 0.42 0.83 3942 0.43 0.82 B4 4880 3967 0.36 0.81 4007 0.28 0.82 B5 5278 4618 0.38 0.87 4590 0.34 0.87 B6 6400 5512 0.37 0.86 5316 0.43 0.83 0.83 2928 0.28 0.84 0.85 Average 0.84 0.03 Std. Dev. 0.03 0.90 Maximum 0.88 0.81 Minimum 0.82 1st Order Analysis 2nd Order Analysis B7 3503 2919 0.29 Average Std. Dev. Maximum Minimum thod Flexural Capacities and Statistics tions illustrate the use of the Unified resistance of a discretely braced non- com a discretely braced compact compression flange section using the results of a 1 st order analysis. Appendix B.2 contains a summary of the Unified Design Method provisions for non-composite I-girders. 4.3.1 Non-Compact Compression Flange Example As before, bending component B1 was chosen for these example calculations. The B1 section properties listed in Section 4.1.1 still apply. However, the unique set of coincidental loads from the 1 st order analysis that are needed for these calculations are listed here: f l1 = 1 st order analysis lateral flange bending stress = 100.8 MPa Table 4-14: Summary of Unified Design Me The following two sets of example calcula Design Method for determining the flexural pact compression flange section and of flange slend 221 f bu = 1 st order analysis flange stress from vertical bending = 314.9 MPa ? Check the flange compactness B1 was designed to be non-compact. To be defined as compact, the compression erness must meet the following criterion: yc pf F E 38.0=? 49.8 5.408 204000 38.0 == pf ? fc fc f t b 2 =? () 49.839.11 48.192 7.443 =>== pff ?? Because pff ?? > , the flange is non-compact. ? Determine critical flange local buckling stre Because the flange is non-compact, first determine the critical flange stress that will cause local buckling of the flange. yr F rf E 56.0=? 96.1456.0 == rf ? Because F yc yw R h , is taken as 1.0. Determine the web load shedding factor, R b . 0.286 204000 < F [ ] ycywycyr FFFF 5.0,7.0min >= ()[] MPaFF ycyr 3.2045.02864.4455.4087.0min ss MPa0.,0.286 =>=== the hybrid web reduction factor, 222 If yrw c F E t D 76.5 2 ? , then R b = 1.0 () 8.153 0.286 204000 76.50.147 230.8 9.6042 =?= Therefore R b = 1.0 ychb pfrf pff ych yr FLBnc FRR FR F F ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??= ?? ?? 11 )( MPaF FLBnc 6.3535.408 49.896.14 49.839.11 5.408 0.286 11 )( = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??= ? l torsional buckling stress The critical lateral torsional buckling stress is based on the unbraced length of the comp Determine the critical latera ression flange. ? ? ? ? ? ? ? ? + fcfc wc fc tb tD b r 3 1 112 = t () () mmr 3.117 48.197.443 230.89.604 3 1 112 7.443 = ? ? ? ? ? ? ? ? ? ? ? ? ? ? + yc tp F E rL 0.1= () mmL p 2621 5.408 204000 3.1170.1 == yr tr F E rL ?= () mmL r 9842 0.286 204000 3.117 ==? t = 223 Because rbp LLL ?< , the unbraced length is non-compact. [ ] MPaFFFF ycywycyr 0.2865.0,7.0min =?= C b = 1.0 for constant vertical bending moment ychbychb pr pb ych yr bLTBnc FRRFRR LL LL FR F CF ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??= 11 )( MPaF LTBnc 0.3725.408 26219842 26214772 5.408 0.286 110.1 )( = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??= ? Determine the vertical bending moment capacity using the 1/3 rule [ ] MPaFFF LTBncFLBncnc 6.353,min )()( == Because f l1 is from a 1 st order analysis, apply the recomm plification factor, AF, to account for the 2 etric effects on lateral flange bending, f l . ended am nd order geom ? ? ? ? ? ? ? cr bu F f 1 85.0 F cr is the fl ? ? ? ? ? ? =AF where ange elastic lateral-torsional buckling s . 2 2 ? ? ? ? ? ? ? ? = t b bb cr r L ERC F ? ()()( ) F cr 1217 3.117 4772 2040000.10.1 2 2 = ? ? ? ? ? ? = ? 147.1 1217 9.314 1 85.0 = ? ? ? ? ? ? ? ? ? ? ? ? ? =AF MPa tress 224 () 1ll fAFf = () MPaf l 6.1158.100147.1 == Apply the 1/3 rd rule to determine the vertical bending capacity. ? f = 1.00 lbunf ffF 3 1 +?? MPaF nf 6.353=? () MPaMPa 4.3536.115 3 1 9.314353 =+? Therefore f bu = 314.9MPa is acceptable and the equivalent vertical bending moment is: xcbu SfM 6. n = ( ) mkNmmNxxM ?=?= 39081039081041.129.314 66 Please refer to Table 4-18 to see how this capacity compares to the experimental measurement. Compact Comp ple The properties for bending com nt B5 are listed in Section 4.1.2. The 1 st order or appropriate for this set of calculations are: f l1 = 1 st ge bending stress = 101.5 MPa f bu = 1 st order analysis flange stress from vertical bending = 317.2 MPa ? actness pact compression flange. Therefore it must meet the following slenderness limit. loads f order analysis lateral flan Check the flange comp B5 was designed to have a com n = 4.3.2 ression Flange Exam pone 225 yc pf F E 38.0=? 64.8 0.395 204000 38.0 == pf ? fc fc f t b 2 =? () 64.850.8 66.242 1.419 =<== pff ?? Because pff ?? ? , the flange is compact. ? Determine the critical flange local buckling stress Because the compression flange is compact, ychbFLBnc FRRF = )( . Determine the hybrid girder reduction factor, . F yc 150)213(125.0100 ??+? R t D w the critical compressive longitudinal stress, cr F,is: yc w cr F t D Ek F ? ? ? ? ? ? ? ? ? = 2 9.0 Equation B-14 where: k = bend-buckling coefficient = 2 2.7 ? ? ? ? ? ? ? ? c D D D c = depth of web in compression B.1.2.2 Transversely Stiffened Webs For transversely stiffened webs that meet the following slenderness and stiffener spacing criteria: 150? w t D for mR 213? Dd o ? for mR 213> ()DDRd o 3)213(00506.00.1 ??+? the critical compressive longitudinal stress, cr F , is given by Equation B-14 above but where: 313 k = bend-buckling coefficient = 2 0.9 ? ? ? ? ? ? ? ? c D D B.1.2.3 Transversely and Longitudinally Stiffened Webs For transversely and longitudinally stiffened webs that meet the transverse stiffener spacing requirements of Section B.1.2.2 and the following slenderness criteria: 300? w t D the critical compressive longitudinal stress is given by Equation B-14 above but where the bend-buckling coefficient is: 2 17.5 ? ? ? ? ? ? ? ? = s t D k for 4.0? c s D d or 2 64.11 ? ? ? ? ? ? ? ? ? = sc dD D k for 4.0< c s D d where: d s = distance along web between longitudinal stiffener and compression flange B.2 A Summary of the Unified Design Method Equations for the Design of Non- Composite I-Girders in Flexure The Unified Design Method provisions to determine the flange longitudinal stress limit, nf F? , are valid for I-Girders that meet the following criteria: Compression flanges width, b f , shall be at least 30% of the depth of the web in compression, D c . Tension flanges shall meet the following slenderness requirement: 314 0.12 2 ? ft ft t b Webs shall meet the following slenderness requirements: For unstiffened or transversely stiffened webs 150? w t D For longitudinally stiffened webs 300? w t D For all strength limit state load combinations the governing design equation for longitudinal flange stress is: lbunf ffF 3 1 +?? Equation B-15 where yl Ff 6.0? ? f = 1.00 and n F is determined for either the compression flange, nc F , or the tension flange, nt F , by the provisions outlined below. B.2.1 Discretely Braced Compression Flanges The longitudinal compressive stress limit, ncf F? , is the smaller of )(FLBncf F? or )(LTBncf F? determined from the Flange Local Buckling and Lateral Torsional Buckling limits. B.2.1.1 Flange Local Buckling If pff ?? ? , then the flange is compact and 315 ychbFLBnc FRRF = )( Equation B-16 where fc fc f t b 2 =? yc pf F E 38.0=? If pff ?? > , then the flange is non-compact and ychb pfrf pff ych yr FLBnc FRR FR F F ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??= ?? ?? 11 )( Equation B-17 where [ ] ycywycyr FFFF 5.0,7.0min >= yr rf F E 56.0=? B.2.1.2 Lateral Torsional Buckling If pb LL ? , then compact unbraced length and ychbLTBnc FRRF = )( Equation B-18 where ? ? ? ? ? ? ? ? + = fcfc wc fc t tb tD b r 3 1 112 yc tp F E rL 0.1= If rbp LLL ?< , then non-compact unbraced length and 316 ychbychb pr pb ych yr bLTBnc FRRFRR LL LL FR F CF ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ??= 11 )( Equation B-19 where [ ] ycywycyr FFFF 5.0,7.0min ?= yr tr F E rL ?= If rb LL > , then slender unbraced length and ychbcrLTBnc FRRFF ?= )( Equation B-20 where 2 2 ? ? ? ? ? ? ? ? = t b bb cr r L ERC F ? B.2.2 Discretely Braced Tension Flanges The longitudinal tensile stress limit, ntf F? , is ythntf FRF =? Equation B-21 317 References AASHTO, 2004. 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