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ACKNOWLEDGMENT This work was sponsored by the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration, and was conducted in the National Cooperative Highway Research Program (NCHRP), which is administered by the Transportation Research Board (TRB) of the National Academies. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, Transit Development Corporation, or AOC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB.
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i Acknowledgments The research reported herein was performed under NCHRP 10-71 Cast-in-Place Concrete Connections for Precast Deck Systems by investigators from the Department of Civil Engineering at the University of Minnesota, the Department of Civil and Environmental Engineering, University of Tennessee â Knoxville, Eriksson Technologies, Inc., Berger/ABAM Engineers, Inc., Concrete Technology Corp., and Central Pre- Mix Prestress Co. The University of Minnesota was the contractor for this study. The principal authors of this report are Catherine French, Carol Shield, David Klaseus, Matthew Smith and Whitney Eriksson, of the University of Minnesota and Z. John Ma and Peng Zhu of the University of Tennessee Knoxville. The authors from the University of Minnesota would like to acknowledge the contributions of Professor Arturo Schultz; graduate students who contributed to this study, including Roberto Piccinin, Brock Hedegaard, and Phil Cici; research personnel for their assistance in the laboratory, Paul Bergson and Rachel Gaulke; as well as many undergraduate research assistants, especially Dan Sleigh and Eric Matzke. The authors also wish to acknowledge the Minnesota Supercomputing Institute for Advanced Computational Research, which provided supercomputing resources for many of the numerical studies completed during this study. The authors from the University of Tennessee at Knoxville (UTK) would like to acknowledge the contributions of graduate students including Peng Zhu, Sam Lewis, Beth Chapman, Qi Cao, Lungui Li, and Mohammad Bayat; assistance of UTK laboratory technicians Ken Thomas and Larry Roberts; and many undergraduate research assistants at UTK for their assistance with the testing. Ross Prestressed Concrete, Inc. donated some of the concrete materials and helped with the casting of the specimens. Gerdau Ameristeel, Engineered Wire products and Salit Specialty Rebar Inc. provided the reinforcement. Robert Gulyas of BASF Construction Chemicals, LLC provided valuable comments in regards to the material testing program. The authors gratefully acknowledge the support of BASF Construction Chemicals, LLC, CTS Cement Manufacturing Corporation, Dow Reichhold, Specialty Latex LLC, Enco Materials, Inc., Five Star Products, Inc., and Lafarge North America, Inc.
ii Abstract This report contains recommended design specifications, construction specifications, and five illustrative examples of durable CIP reinforced concrete connections for precast deck systems that emulate monolithic construction, considering issues including speed of construction, durability, and fatigue. Included in the report is the supporting research that led to these recommendations. This research focused on systems that reduce the need to place and remove formwork thus accelerating on-site construction and improving safety. The three systems considered to accomplish these objectives were: (1) a precast composite slab span system (PCSSS) for short to moderate span structures, (2) full-depth prefabricated concrete decks, and (3) deck joint closure details (e.g., decked-bulb-tee (DBT) flange connections) for precast prestressed concrete girder systems for long span structures. Depending on the system, the connections are either transverse (i.e., across the width of the bridge) or longitudinal (i.e., along the length of the bridge). The first system, PCSSS, is an entire bridge system; whereas the other two systems investigated in the project represented transverse and longitudinal joint details to transfer moment and shear in precast deck panels and flanges of decked bulb tees. Two types of connection concepts were explored with these details, looped bar details and two layers of headed bar details.
iii Contents Contents ........................................................................................................................................... iii List of Tables ..................................................................................................................................... ix List of Figures .................................................................................................................................. xiv Chapter 1: Introduction and Research Approach .................................................................................1 1.0 Introduction .............................................................................................................................. 1 1.1. Scope of Study ........................................................................................................................... 3 1.1.1. Task 1 â Review relevant practice, performance, data, and research findings ................ 3 1.1.2. Task 2 â Develop detailed design, fabrication, construction, and performance criteria .. 3 1.1.3. Task 3 â Develop conceptual designs for CIP reinforced concrete connections .............. 3 1.1.4. Task 4 â Develop an updated and detailed work plan ...................................................... 3 1.1.5. Task 5 â Submit an interim report .................................................................................... 3 1.1.6. Task 6 â Execute the approved work plan for evaluation of the connections ................. 4 1.1.7. Task 7 â Prepare a connection design, detailing guide, and construction guide .............. 4 1.1.8. Task 8 â Develop specification language and commentary .............................................. 4 1.1.9. Task 9 â Submit the products of Tasks 7 and 8 and the Draft Final Report ...................... 4 1.1.10. Task 10 â Final Report ....................................................................................................... 4 1.2. Introduction to Precast Composite Slab Span Systems (PCSSS) ............................................... 4 1.3. Introduction to Longitudinal and Transverse Joints in Decked Bulb-T (DBT) and Full-Depth Precast Panel on Girder Systems .......................................................................................................... 5 1.4. Organization of Report .............................................................................................................. 6 Chapter 2: PCSSS: Literature Review ...................................................................................................8 2.0 Introduction to Literature Review ............................................................................................ 8 2.1. Poutre Dalle System .................................................................................................................. 8 2.2. Crack Control Reinforcement, Frosch et al., 2006 .................................................................... 9 2.3. Horizontal Shear Capacity of Composite Concrete Beams without Ties, Naito et al., 2006 .. 14 2.4. AASHTO (2007) Bursting Design Requirements ...................................................................... 18 2.4.1. Bursting, Splitting and Spalling Stresses ......................................................................... 19 2.4.2. Stresses in End Regions of Post-Tensioned and Pretensioned Sections ......................... 20 Chapter 3: PCSSS: Background .......................................................................................................... 22 3.0 Introduction to Background .................................................................................................... 22 3.1. Introduction to Survey Results ................................................................................................ 22
iv 3.1.1. Mn/DOT PCSSS and Poutre Dalle System ....................................................................... 24 3.2. Center City PCSSS Bridge ......................................................................................................... 24 3.2.1. Live Load Distribution Tests at the Center City Bridge ................................................... 31 3.3. Restraint Moment ................................................................................................................... 38 Chapter 4: PCSSS Numerical Studies: Practical Span Ranges, Applicability of Design Recommendations, and Other Issues .............................................................................................................................. 45 4.0 Introduction and Organization ................................................................................................ 45 4.1. Parametric Study to Investigate Practical Span Ranges and Associated Precast Sections ..... 46 4.2. Parametric Study to Investigate Effect of Transverse Hook Spacing on Reflective Cracking . 50 4.3. Parametric Study to Investigate Live-Load Distribution Factors for PCSSS ............................ 59 4.4. Parametric Study to Investigate Skew Effects ........................................................................ 64 4.5. End Zone Stresses in Precast Inverted Tee Sections ............................................................... 68 4.6. Connection Details between Superstructure and Substructure ............................................. 78 4.7. Numerical Determination of Laboratory Loading ................................................................... 80 Chapter 5: PCSSS: Large-Scale Laboratory Bridge Investigation of System Behavior ............................ 83 5.0 Introduction ............................................................................................................................ 83 5.1. Selection and Design of Laboratory Bridge Specimens .......................................................... 83 5.1.1. Concept 1 Laboratory Bridge .......................................................................................... 85 5.1.2. Concept 2 Laboratory Bridge ........................................................................................ 106 5.1.3. Instrumentation of Concept 1 and Concept 2 Laboratory Bridge Specimens .............. 118 5.2. Construction of Laboratory Bridge Specimens and Material Properties .............................. 123 5.3. Laboratory Testing Program and Results .............................................................................. 124 5.3.1. Simulated Traffic Loading.............................................................................................. 124 5.3.2. Environmental Effect Simulation .................................................................................. 130 5.3.3. Load Transfer Between Precast Panels ......................................................................... 143 5.3.4. Composite Action .......................................................................................................... 146 5.4. Destructive Testing of Large-Scale Laboratory Specimens ................................................... 153 5.4.1. Inspection of Cores taken from Laboratory Bridge Specimens .................................... 153 5.4.2. Visual Inspection of Internal Surfaces after Sectioning the Laboratory Bridge Specimens by Means of Saw Cutting .............................................................................................................. 157 Chapter 6: PCSSS: Subassemblage Investigation of Crack Control Reinforcement ............................. 162 6.0 Introduction .......................................................................................................................... 162 6.1. Selection and Design of Laboratory Subassemblage Specimens .......................................... 162 6.1.1. Subassemblage 1 â Control Specimen 1 ....................................................................... 166
v 6.1.2. Subassemblage 2 â No Cage Reinforcement ................................................................ 167 6.1.3. Subassemblage 3 â Increased Distance Between Transverse Hooks and Precast Flange .. ....................................................................................................................................... 168 6.1.4. Subassemblage 4 â Increased Depth of Precast Section .............................................. 170 6.1.5. Subassemblage 5 â Increased Transverse Hook Size .................................................... 171 6.1.6. Subassemblage 6 â Frosch Design Recommendations ................................................. 171 6.1.7. Subassemblage 7 â Control Specimen 2 ....................................................................... 173 6.2. Instrumentation of Subassemblage Specimens .................................................................... 174 6.3. Clamping System ................................................................................................................... 178 6.4. Construction of Subassemblage Specimens and Material Properties .................................. 182 6.5. Laboratory Testing Program ................................................................................................. 184 6.5.1. Data Acquisition ............................................................................................................ 188 6.6. Results of Laboratory Testing ............................................................................................... 188 6.6.1. Transverse Strains Near Joint Region due to Shrinkage and Handling of Subassemblage Specimens ..................................................................................................................................... 189 6.6.2. General Observations of Cracking Behavior during Load Testing ................................. 190 6.6.3. Width of Cracking Near Joint Region Measured with Crack Gage ................................ 192 6.6.4. Width of Cracking Near Joint Region Measured with LVDTs ........................................ 201 6.6.5. Rate of Increase in the Length of Cracking Near Joint Region via Visual Observation . 205 6.6.6. Investigation of the Vertical and Horizontal Generation and Propagation of Reflective Cracking near the Precast Joint Measured via Concrete Embedment Resistive Strain Gages ..... 209 6.6.7. Calculation of Expected Tensile Reinforcement Stress in Subassemblage Specimens . 226 6.7. Destructive Testing of Subassemblage Specimens ............................................................... 228 Chapter 7: PCSSS: Conclusions and Recommendations .................................................................... 233 7.0 Introduction .......................................................................................................................... 233 7.1. Bursting, Splitting and Spalling Stresses ............................................................................... 234 7.2. Restraint Moment ................................................................................................................. 235 7.3. Live Load Distribution Factors ............................................................................................... 235 7.4. Skew ...................................................................................................................................... 236 7.5. Composite Action and Horizontal Shear Strength ................................................................ 237 7.6. Control of Reflective Cracking across Longitudinal Joint between Precast Flanges ............. 237 7.7. PCSSS Design Recommendations .......................................................................................... 240 Chapter 8: Flange/Deck Connection: Concept Development of Joint Details for Accelerated Bridge Construction .................................................................................................................................. 241
vi 8.0 Introduction .......................................................................................................................... 241 8.1. Longitudinal and Transverse Connection Concepts between Precast Panels and Decked Bulb- T (DBT) Flanges .................................................................................................................................. 243 8.1.1. Summary of Phone Survey in Association with Longitudinal and Transverse Connection Concepts between Precast Panels and Bulb-T Flanges ................................................................. 244 8.1.2. Criteria Considered and Finalization of Longitudinal and Transverse Connection Concepts Investigated in NCHRP 10-71 ........................................................................................ 245 8.2. Organization of Report Regarding Investigation of Longitudinal and Transverse Connection Concepts between Precast Panels and Bulb-T Flanges ..................................................................... 247 Chapter 9: Flange/Deck Connection: Selection of Most Promising Connection Detail through Two- Phase Experimental Investigation ................................................................................................... 248 9.0 Introduction to Two-Phase Experimental Investigation to Finalize Connection Concept Detail for Further Study ............................................................................................................................... 248 9.1. Test Phase I ........................................................................................................................... 248 9.1.1. Specimen Design ........................................................................................................... 248 9.1.2. Experimental Setup and Instrumentation .................................................................... 255 9.1.3. Specimen Construction, Reinforcement Cost and Fabrication ..................................... 260 9.1.4. Material Testing ............................................................................................................ 263 9.1.5. Results and Discussion .................................................................................................. 270 9.1.6. Conclusions for Phase I U-Bar (SS, DWR) and Headed Bar (HB) Tests .......................... 291 9.2. Test Phase II .......................................................................................................................... 292 9.2.1. Experimental Setup and Instrumentation .................................................................... 296 9.2.2. Material Testing ............................................................................................................ 298 9.2.3. Results and Discussion .................................................................................................. 299 9.2.4. Conclusions for Phase II Tests ....................................................................................... 323 9.3. Conclusions ........................................................................................................................... 324 Chapter 10: Flange/Deck Connection: Numerical Studies to Determine Forces to be Applied in Large- Scale Tests ..................................................................................................................................... 326 10.1. Investigation of Maximum Forces in the Longitudinal Joints ........................................... 326 10.1.1. Introduction .................................................................................................................. 326 10.1.2. Description of Bridge Parameters ................................................................................. 327 10.1.3. Description of Loadings ................................................................................................. 330 10.1.4. Development of Finite Element Models ....................................................................... 331 10.1.5. Parametric Study ........................................................................................................... 333 10.2. Maximum Forces in the Transverse Joints ........................................................................ 362
vii 10.3. Conclusions ....................................................................................................................... 368 Chapter 11: Selection of Durable Closure Pour Materials for Accelerated Bridge Construction ......... 370 11.0 Introduction .......................................................................................................................... 370 11.1. Preliminary Performance Criteria ..................................................................................... 372 11.2. Selection of Candidate Materials for Long-Term Tests ..................................................... 375 11.2.1. Overnight Cure Materials and Their Preliminary Selection .......................................... 375 11.2.2. 7-Day Cure Materials and Their Preliminary Selection ................................................. 379 11.3. Long-Term Tests ................................................................................................................ 382 11.3.1. Bond Strength Test........................................................................................................ 382 11.3.2. Permeability Test .......................................................................................................... 384 11.3.3. Freezing-and-Thawing Test ........................................................................................... 387 11.3.4. Shrinkage Test ............................................................................................................... 388 11.4. Proposed Performance Criteria and Conclusions ............................................................. 390 Chapter 12: Longitudinal Joint Details For Accelerated Bridge Construction: Fatigue Evaluation ....... 392 12.0 Introduction .......................................................................................................................... 392 12.1. Experimental Program ...................................................................................................... 393 12.1.1. Slab Dimension .............................................................................................................. 393 12.1.2. Reinforcement Layout and Strain Gage Instrumentation ............................................. 393 12.1.3. Panel Fabrication .......................................................................................................... 395 12.1.4. Joint Surface Preparation .............................................................................................. 396 12.1.5. Closure Pour (CP) Materials .......................................................................................... 397 12.1.6. Testing Plan and Setup .................................................................................................. 397 12.1.7. Fatigue Loading Determination .................................................................................... 405 12.1.8. Moment Capacity and Curvature .................................................................................. 408 12.1.9. Deflection Development ............................................................................................... 415 12.1.10. Crack Width Development ........................................................................................... 419 12.1.11. Strain Development ..................................................................................................... 425 12.1.12. Failure of Specimen ..................................................................................................... 428 12.2. Conclusions ....................................................................................................................... 431 Chapter 13: Transverse Joint Details For Accelerated Bridge Construction: Fatigue Evaluation ......... 433 13.0 Introduction .......................................................................................................................... 433 13.1. Experimental Program ...................................................................................................... 433 13.1.1. Specimen Dimension ..................................................................................................... 433
viii 13.1.2. Reinforcement Layout and Strain Gage Instrumentation ............................................. 434 13.1.3. Specimen Fabrication .................................................................................................... 436 13.1.4. Joint Surface Preparation .............................................................................................. 437 13.1.5. Closure-Pour Materials ................................................................................................. 438 13.1.6. Testing Plan and Setup .................................................................................................. 438 13.1.7. Fatigue Loading Determination .................................................................................... 441 13.1.8. Tensile Capacity ............................................................................................................ 442 13.1.9. Load Deflection Relationships ....................................................................................... 443 13.1.10. Crack Width Development ........................................................................................... 444 13.1.11. Strain Development ..................................................................................................... 447 13.1.12. Failure of Specimen ..................................................................................................... 449 13.2. Conclusions ....................................................................................................................... 452 Chapter 14: Full-Depth Deck Panel and Decked Bulb-T: Summary .................................................... 453 14.1. Summary ........................................................................................................................... 453 14.2. Full Depth Deck Panel and Decked Bulb T Design Recommendations: ............................ 456 References for PCSSS Study ............................................................................................................ 457 References for Full-Depth Deck Panel and Decked Bulb-T Study ...................................................... 461 Appendix A: NCHRP 10-71 Design Guide Appendix B: NCHRP 10-71 Design Examples Appendix C: Phone Survey Results Appendix D: Center City Field Bridge Instrumentation Designation, Nominal, and Measured Locations Appendix E: Concept 1 Large-Scale Laboratory Bridge Instrumentation Designation and Measured Locations Appendix F: Concept 2 Large-Scale Laboratory Bridge Instrumentation Designation, Nominal, and Measured Locations Appendix G: Large-Scale Laboratory Bridge and Subassemblage Core Analysis Appendix H: Subassemblage Sectional Calculations and Analyses Appendix I: Subassemblage Instrumentation Designation, Nominal, and Measured Locations
ix List of Tables Table 2.2.1: Characteristics of Bridges in Field Investigation (Frosch et al., 2006) ............................... 10 Table 2.2.2: Characteristics of deck reinforcement in field investigation (Frosch et al., 2006) ............. 11 Table 2.2.3: Comparison of crack width statistics (Frosch et al., 2006) ............................................... 12 Table 2.2.4: Range of variables considered in parametric study (Frosch et al., 2006) .......................... 13 Table 2.3.1: Research parameters and specimen characteristics considered during the study (Naito et al., 2006) ......................................................................................................................................... 16 Table 2.3.2: Horizontal shear stress at cracking (psi) during 5-point load tests (Naito et al., 2006) ...... 17 Table 2.3.3: Horizontal shear stress at ultimate (psi) during two-point load tests (Naito et al., 2006) .. 18 Table 3.1.1: Distribution of phone survey respondents ..................................................................... 23 Table 3.2.1: Increases in transverse mechanical strains immediately over longitudinal joint during static live load truck tests on the Center City Bridge (Smith et al. 2008) ............................................. 34 Table 4.1.11: Concrete stress limits utilized during parametric study .................................................. 48 Table 4.1.2: Precast section dimensions and results of parametric study ........................................... 49 Table 4.2.1: Summary of FEM runs to investigate effects of transverse hooked bar spacing................ 52 Table 4.3.1: Summary of FEM runs to investigate longitudinal and transverse live-load distribution factors ............................................................................................................................................. 62 Table 4.3.2: AASHTO (2010) longitudinal design moments and curvatures ......................................... 63 Table 4.3.3: FEM and design longitudinal curvatures under Tandem 2 and Tandem 5 load cases ........ 64 Table 4.4.1: Summary of FEM runs to investigate performance of skewed PCSSS ............................... 66 Table 4.5.1: Description of models run during parametric study ........................................................ 72 Table 4.5.2: Ratio of Spalling Forces to Prestress Forces as Predicted by FE Models for Slabs with Equivalent e/h as Feasible Precast Inverted Tee Sections, using both Uniform and Linear Bond Stress Distributions, varying h and e/h and constant Lt=20 in. ..................................................................... 74 Table 4.5.3: Vertical reinforcement in configurations 1-4 of the precast members utilized in experimental study .......................................................................................................................... 75 Table 4.5.4: Maximum of the measured strain values in end regions of precast members used for Concept 1 laboratory bridge in the 88 minutes after transfer of prestress force ................................. 76 Table 4.5.5: Spalling reinforcement for Precast Inverted-T Sections .................................................. 78 Table 5.1.1: Original and modified design criteria in Spans 1 and 2 of the Concept 1 laboratory bridge ........................................................................................................................................................ 86 Table 5.1.2: Comparison of design parameters between Span 1 of Concept 1 and Concept 2 laboratory bridge specimen ............................................................................................................................ 107 Table 5.1.3: Transverse load transfer and crack control reinforcement ratios for the Concept 1 and Concept 2 large-scale laboratory bridge specimens ......................................................................... 109 Table 5.2.1: Measured CIP material properties at an age of 28 days................................................. 123
x Table 5.2.2: Measured precast concrete material properties for the Concept 1 and Concept 2 bridges ...................................................................................................................................................... 123 Table 5.3.1: Measured vertical locations of transversely oriented strain gages that were utilized in the observation of reflective cracking in the Center City Bridge and laboratory bridge specimens .......... 127 Table 5.3.2: Measured transverse strains during introduction of reflective cracking after the completion of one million fatigue cycles in each specimen .............................................................. 127 Table 5.3.31: Change in transverse strain measured at 35 kips throughout the course of 2M cycles of fatigue loading in each span of Concept 1 and Concept 2 laboratory specimens ............................... 128 Table 5.3.4: Maximum transverse strains and number of cycles completed at given strain level during laboratory environmental effect simulation .................................................................................... 132 Table 5.3.5: Measured load and transverse strain, and number of cycles completed during environmental effect simulation on Span 2 of the Concept 1 laboratory bridge specimen ................ 134 Table 5.3.6: Measured load and transverse strain, and number of cycles completed during environmental effect simulation on Span 1 of the Concept 1 laboratory bridge specimen ................ 136 Table 5.3.7: Measured load and transverse strain, and number of cycles completed during environmental effect simulation at the quarter points of the Concept 2 laboratory bridge specimen 139 Table 5.3.8: Measured load and transverse strain, and number of cycles completed during environmental effect simulation at midspan of the Concept 2 laboratory bridge specimen .............. 141 Table 5.3.9: Maximum loads applied to laboratory bridge specimens during ultimate loading, calculated applied moments, and predicted moment capacities ...................................................... 150 Table 5.3.10: Longitudinal curvature and relevant values during ultimate loading on Concept 2 laboratory bridge specimen ............................................................................................................ 151 Table 5.4.1: Crack width classification categories for analysis of core specimens ............................. 153 Table 5.4.2: Summary of maximum height and width of cracks measured in core specimens from the Concept 1 laboratory specimen ...................................................................................................... 155 Table 5.4.3: Summary of maximum height and width of cracks measured in core specimens from the Concept 2 laboratory specimen ...................................................................................................... 156 Table 6.1.1: Subassemblage specimen design details ...................................................................... 164 Table 6.4.1: Measured subassemblage CIP concrete material properties at an age of 28 days .......... 183 Table 6.4.2: Measured subassemblage CIP concrete material properties on first day of specimen testing ........................................................................................................................................... 184 Table 6.5.1: Subassemblage specimen measured modulus of rupture and predicted cracking moment and load ........................................................................................................................................ 185 Table 6.5.2: Subassemblage loading plan for example specimen with predicted cracking load of 40 kips ...................................................................................................................................................... 187 Table 6.6.1: Increase in the measured crack width on the end face as a result of cyclic loading at each load step ....................................................................................................................................... 199 Table 6.6.2: Maximum crack widths via crack gage (from Section 6.6.3) and LVDT displacements measured on the origin and end faces1 ........................................................................................... 204
xi Table 6.6.3: Predicted locations of the subassemblage cracked section neutral axes ........................ 208 Table 6.6.4: Maximum applied loading and associated predicted tensile reinforcement stresses in subassemblage specimens ............................................................................................................. 228 Table 6.7.1: Crack width classification categories for analysis of core specimens ............................. 230 Table 6.7.2: Summary of maximum height and width of crack measured in core specimens ............. 231 Table 9.1.1: Reinforcement required for the U-bar detail in an 8 in. deck ......................................... 250 Table 9.1.2: Reinforcement required for the headed bar detail in an 8 in. deck ................................ 250 Table 9.1.3: Reinforcement required for the U-bar detail in a 6-¼ in. deck ....................................... 250 Table 9.1.4: Reinforcement required for the headed bar detail in a 6-¼ in. deck - ............................ 251 Table 9.1.5: Negative moment longitudinal reinforcement .............................................................. 252 Table 9.1.6: Concrete compressive strengths, U-bar specimens ....................................................... 263 Table 9.1.7: Concrete compressive strengths, headed bar specimens .............................................. 263 Table 9.1.8 Modulus of elasticity and ultimate strength .................................................................. 264 Table 9.1.9: Weld test results, one pass welds ................................................................................ 268 Table 9.1.10: Weld test results, Beveled Welds ............................................................................... 269 Table 9.1.11: Weld test results, beveled welds and 110 ksi welding stick ......................................... 270 Table 9.1.12: Moment demands for specimens containing the U-bar detail ..................................... 271 Table 9.1.13: Moment demands for specimens containing the headed bar detail ............................. 271 Table 9.1.14: Calculated moments and curvature (six-bar side) ....................................................... 275 Table 9.2.1: Testing parameters ..................................................................................................... 293 Table 9.2.2: Concrete compressive strengths (longitudinal joint specimens) ................................... 298 Table 9.2.3: Concrete compressive strengths (transverse joint specimens) ...................................... 299 Table 9.2.4: Service moments ........................................................................................................ 300 Table 9.2.5: Flexural test results, nominal moments (Mn) ............................................................... 309 Table 9.2.6: Flexural test results, curvatures (Φn ) .......................................................................... 309 Table 9.2.7: Tensile test results ...................................................................................................... 315 Table 9.2.8: Summary of tested parameters ................................................................................... 323 Table 10.1.1: Practical span ranges for optimized DBT girders ......................................................... 326 Table 10.1.2: Summary of the seven bridge models......................................................................... 327 Table 10.1.3: Forces in Joint 1 due to loads applied in accordance with Figure 10.1.9 ....................... 334 Table 10.1.4: Forces in Joint 1 due to loads applied in accordance with Figure 10.1.10 ..................... 337 Table 10.1.5: Forces in Joint 1 due to loads applied in accordance with Figure 10.1.11 ..................... 339 Table 10.1.6: Forces in Joint 1 due to loads applied in accordance with Figure 10.1.12 ..................... 340
xii Table 10.1.7: Negative moment in Joint 2 due to loads applied in accordance with Figure 10.1.14 ... 343 Table 10.1.8: Negative moment in Joints 2 and 3 due to loads applied in accordance with Figure 10.1.16 .......................................................................................................................................... 345 Table 10.1.9: Maximum positive moment and shear comparison between bridge B and modified bridge B ......................................................................................................................................... 345 Table 10.1.10: Maximum positive moment (+Moment) and shear in Joint 1 under single-lane loading ...................................................................................................................................................... 356 Table 10.1.11: Maximum positive moment (+Moment) and shear in Joint 2 under single-lane loading ...................................................................................................................................................... 356 Table 10.1.12: Maximum positive moment (+Moment) and shear in Joint 1 under multi-lane loading ...................................................................................................................................................... 357 Table 10.1.13: Maximum positive moment (+Moment) and shear in Joint 2 under multi-lane loading ...................................................................................................................................................... 357 Table 10.1.14: Maximum negative moment in Joints 1 and 2 under multi-lane loading .................... 358 Table 10.2.1: Negative moment over piers in bridge models ........................................................... 363 Table 10.2.2: Moment over piers in bridge models with DBT65 ....................................................... 364 Table 10.2.3: Moment over piers in bridge models with BT72 .......................................................... 364 Table 11.1.1: Proposed performance characteristic grades by Russell and Ozyildirim (2006) ............ 373 Table 11.1.2: Performance characteristic grades by Tepke and Tikalsky (2007) ................................ 373 Table 11.2.1: Candidate overnight cure materials including mix proportions .............................. 376 Table 11.2.2 Candidate grout workability observations for neat gouts and extended grouts ............ 378 Table 11.2.3: Candidate HPC mixes and mix proportions ................................................................. 380 Table 11.2.4: 7-day cure mixes and mixture proportions, lb/yd3 ...................................................... 381 Table 11.2.5: Compressive strengths (psi) per ASTM C 39 Modified ................................................. 382 Table 11.3.1 Slant cylinder bond strength and failure mode ............................................................ 384 Table 11.3.2: Depths (in.) for 0.2% chloride content (by mass of cement) ........................................ 387 Table 11.4.1: Proposed performance criteria of CP materials ........................................................... 390 Table 11.4.2: Application of CP material grades for freezing-and-thawing durability ........................ 391 Table 12.1.1: Slab specimen loading matrix .................................................................................... 399 Table 12.1.2: Compressive strength of concrete panel and grouted joint ......................................... 405 Table 12.1.3: Measured and calculated loading capacity ................................................................ 412 Table 13.1.1: Transverse joint (tension) specimen loading matrix .................................................... 439 Table 13.1.2: Compressive strength of concrete panel and grouted joint ......................................... 441 Table 13.1.3: Tensile capacity ........................................................................................................ 442 Table 14.1.1: Proposed performance criteria of CP materials ........................................................... 454
xiii Table 14.1.2: Application of CP material grades for freezing-and-thawing durability ........................ 454
xiv List of Figures Figure 2.1.1: Photograph of precast section used in Poutre Dalle System (Hagen, 2005) ......................9 Figure 2.4.1: Effects of eccentricity of distribution of compression and spalling forces ....................... 20 Figure 3.2.1: Plan view and construction stages of Mn/DOT Bridge No. 13004 in Center City, Minnesota (Bell et al. 2006) ............................................................................................................................... 25 Figure 3.2.2: Anticipated locations of reflective cracking in Mn/DOT PCSSS (Bell et al. 2006) ............. 26 Figure 3.2.3: Location of instrumented joints in the Center City Bridge (Bell et al. 2006)..................... 26 Figure 3.2.4: Location of transverse concrete embedment gages in each of the three instrumented joints at midspan of the center span of the Center City Bridge (Bell et al. 2006) ................................. 27 Figure 3.2.5: Lower level of concrete embedment and spot-weldable VW gages utilized in observation of reflective cracking in the Center City Bridge .................................................................................. 28 Figure 3.2.6: Plan view of longitudinal instrumentation locations for investigation of live load distribution over the continuous pier (Bell et al. 2006) ...................................................................... 29 Figure 3.2.7: Measured transverse mechanical strain and temperature in Joint 1 of Center City Bridge [note results of red gage (black dashed line) are obscured by those of the blue gage (blue line) in the figure] ............................................................................................................................................. 31 Figure 3.2.8: Single and paired truck positions during live load truck tests at the Center City Bridge (Smith et al. 2008) ............................................................................................................................ 33 Figure 3.2.9: Change in mechanical tensile strain in transverse hooked bars at Joint 1 immediately under wheel load during live load truck tests on the Center City Bridge (Smith et al., 2008) ............... 36 Figure 3.2.10: Longitudinal curvatures at midspan due to a single truck located at midspan of the center span of the Center City Bridge (Smith et al. 2008) ................................................................... 37 Figure 3.3.1: Positive and negative restraint moments in continuous bridge superstructures (Molnau 2007) ............................................................................................................................................... 39 Figure 3.3.2: Ratio of 20-year positive restraint moment (due to time-dependent effects only) to cracking moment comparison .......................................................................................................... 41 Figure 3.3.3: Ratio of 20-year positive restraint moment (due to time-dependent and thermal effects) to cracking moment comparison ...................................................................................................... 42 Figure 3.3.4: Comparison of calculated and TPbeam results for ratio of 20-year restraint moment (due to thermal effects only) to cracking moment .................................................................................... 44 Figure 4.2.1: Location and orientation of loading in the loaded span of the two-span bridge model ... 50 Figure 4.2.2: Crack opening in loaded span for 6 in. hooked bar spacing with or without one rebar per solid element ................................................................................................................................... 53 Figure 4.2.3: Maximum crack opening and transverse bar stress versus transverse hooked bar spacing in loaded span for load case 1 .......................................................................................................... 54 Figure 4.2.4: Transverse stress distribution in the compression (i.e., top) concrete fiber for load case 1 (units of stress are in psi) ................................................................................................................. 55
xv Figure 4.2.5: Longitudinal stress distribution in the compression (i.e., top) concrete fiber for load case 1 (units of stress are in psi) ............................................................................................................... 56 Figure 4.2.6: Transverse stress distribution in the compression (i.e., top) concrete fiber for load case 2 (units of stress are in psi) ................................................................................................................. 57 Figure 4.3.1: Tandem loading located 2 ft. from midspan utilized for FEM live-load distribution study 60 Figure 4.3.2: Panel and joint numbering used in the placement of tandem loading for the center span of the continuous models and the simple-span models ..................................................................... 61 Figure 4.4.1: Placement of precast slab span panels at a skewed support .......................................... 65 Figure 4.4.2: Simply supported, three panel wide bridge and location of loading used for FEM models ........................................................................................................................................................ 67 Figure 4.4.3: Maximum horizontal shear stress measured in the cast-in-place concrete above the precast joint measured under the acute, midspan, and obtuse load cases ......................................... 67 Figure 4.4.4: Maximum horizontal shear stress envelope above longitudinal precast joint considering all load cases for precast joint models and monolithic slab models. ................................................... 68 Figure 4.5.1: Spalling and bursting stresses near the end zone of prestressed members ..................... 69 Figure 4.5.2: Validation of FEM model with experimental results from Gergely (1963) ....................... 71 Figure 4.5.3: Comparison of Bursting and Spalling Stresses for Member e/h=0.20 .............................. 73 Figure 4.5.4: Ratio of spalling force to prestress force as a function of ratio of eccentricity to precast member depth for linear and uniform bond stress distributions, with h= 12 in and Lt = 20 in. ............. 74 Figure 4.5.5: Ratio of Spalling Force to Prestress Force for varying e2/(h*db) ...................................... 77 Figure 4.6.1: Bearing detail at continuous pier in Mn/DOT Bridge No. 13004 in Center City, Minnesota ........................................................................................................................................................ 79 Figure 5.1.1: Reinforcement and depth of concrete considered in the calculation of the reinforcement ratio for transverse load transfer (highlighted in yellow) ................................................................... 84 Figure 5.1.2: Reinforcement and depth of concrete considered in the calculation of the reinforcement ratio for reflective crack control (highlighted in yellow) .................................................................... 85 Figure 5.1.3: Bursting reinforcement details used in the Concept 1 laboratory specimen. Configuration numbers correspond to the discussion on bursting in Section 4.5 ...................................................... 87 Figure 5.1.4: Plan view of the Concept 1 laboratory bridge, including support locations and relevant dimensions. Transverse reinforcement near longitudinal precast joint is not included for clarity ........ 88 Figure 5.1.5: Cross section and individual reinforcement details for the east end of precast beam 1N 89 Figure 5.1.6: Cross section and individual reinforcement details for west end of precast beam 1N ..... 90 Figure 5.1.7: Cross section and individual reinforcement details for midspan of precast beam 1N ...... 91 Figure 5.1.8: Elevation and plan views of reinforcement layout for precast beam 1N ......................... 92 Figure 5.1.9: Cross section and individual reinforcement details for east end of precast beam 1S ....... 93 Figure 5.1.10: Cross section and individual reinforcement details for west end of precast beam 1S .... 94 Figure 5.1.11: Cross section and individual reinforcement details for midspan of precast beam 1S ..... 95
xvi Figure 5.1.12: Elevation and plan views of reinforcement layout for precast beam 1S ........................ 96 Figure 5.1.13: Cross section and individual reinforcement details for east end of precast beam 2N .... 97 Figure 5.1.14: Cross section and individual reinforcement details for west end of precast beam 2N ... 98 Figure 5.1.15: Cross section and individual reinforcement details for midspan of precast beam 2N .... 99 Figure 5.1.16: Elevation and plan views of reinforcement layout for precast beam 2N ..................... 100 Figure 5.1.17: Cross section and individual reinforcement details for east end of precast beam 2S ... 101 Figure 5.1.18: Cross section and individual reinforcement details for west end of precast beam 2S .. 102 Figure 5.1.19: Cross section and individual reinforcement details at midspan of precast beam 2S .... 103 Figure 5.1.20: Elevation and plan views of reinforcement layout for precast beam 2S ...................... 104 Figure 5.1.21: Photograph of the Concept 1 laboratory bridge shortly after completion of the continuity pour .............................................................................................................................. 105 Figure 5.1.22: Support and bearing detail of the end supports of the laboratory bridge specimens ... 106 Figure 5.1.23: Threaded connection and adjacent termination detail of straight bars in east half span of the Concept 2 laboratory bridge specimen .................................................................................. 108 Figure 5.1.24: Conceptual section illustrating continuous nature of embedded reinforcement utilized in conjunction with mechanical anchors when threaded transverse reinforcement is present; figure shown represents configuration in east half span of the Concept 2 laboratory bridge specimen (transverse reinforcement in joint region to be mechanically anchored to reinforcement in precast web is not shown) .......................................................................................................................... 108 Figure 5.1.25: Plan view of the Concept 2 laboratory bridge specimen, including support locations and relevant dimensions. Transverse reinforcement near longitudinal precast joint is not included for clarity ............................................................................................................................................ 110 Figure 5.1.26: Cross section and individual reinforcement details for the east end of the precast beam 1N in the Concept 2 laboratory bridge specimen ............................................................................. 111 Figure 5.1.27: Cross section and individual reinforcement details for the west end of the precast beams 1N and 1S in the Concept 2 laboratory bridge specimen ....................................................... 112 Figure 5.1.28: Cross section and individual reinforcement details at midspan of precast beam 1N in the Concept 2 laboratory bridge specimen ............................................................................................ 113 Figure 5.1.29: Elevation and plan views of the reinforcement layout for precast beam 1N in the Concept 2 laboratory bridge specimen ............................................................................................ 114 Figure 5.1.30: Cross section and individual reinforcement details for the east end of the precast beam 1S in the Concept 2 laboratory bridge specimen .............................................................................. 115 Figure 5.1.31: Cross section and individual reinforcement details at midspan of precast beam 1S in the Concept 2 laboratory bridge specimen ............................................................................................ 116 Figure 5.1.32: Elevation and plan views of the reinforcement layout for precast beam 1S in the Concept 2 laboratory bridge specimen ............................................................................................ 117 Figure 5.1.33: Photograph of the Concept 2 laboratory bridge specimen prior to placement of CIP concrete ........................................................................................................................................ 118
xvii Figure 5.1.34: Instrumentation layout for Concept 1 laboratory bridge specimen (Smith et al. 2008) 119 Figure 5.1.35: Typical instrumentation layout near precast joint in the Concept 1 laboratory bridge specimen ....................................................................................................................................... 120 Figure 5.1.36: Instrumentation layout for the Concept 2 laboratory bridge specimen ....................... 121 Figure 5.1.37: Typical 9 and 6 gage transverse instrumentation layout in Concept 2 laboratory bridge specimen ....................................................................................................................................... 122 Figure 5.1.38: Location of origin and definition of positive x and y ordinates for instrumentation layout in the Concept 1 and Concept 2 laboratory bridge specimen ........................................................... 122 Figure 5.3.1: Placement of patch loads during fatigue loading and extension of longitudinal reflective cracking (applicable in Span 1 only) for the Concept 1 laboratory bridge specimen .......................... 126 Figure 5.3.2: Placement of patch loads during fatigue loading and extension of longitudinal reflective cracking for the Concept 2 laboratory bridge specimen ................................................................... 126 Figure 5.3.3: Transversely oriented concrete embedment resistive gages located nearest the precast flange1. Instrumentation locations which detected reflective cracking and were used for measurement of transverse strain values during fatigue loading are highlighted in black and annotated ................ 129 Figure 5.3.41: Transverse strains measured with a 35 kip patch load applied at midspan during environmental effect simulation in Span 2 of Concept 1 laboratory bridge ...................................... 133 Figure 5.3.5: Transverse strains measured with 35 kip patch load applied at midspan during environmental effect simulation in Span 1 of Concept 1 laboratory bridge ...................................... 135 Figure 5.3.6: Transverse strains measured with 35 kip patch load applied at quarter points during environmental effect simulation in the Concept 2 laboratory bridge ............................................... 138 Figure 5.3.7: Transverse strains measured with 35 kip patch load applied at midspan during environmental effect simulation in the Concept 2 laboratory bridge ............................................... 140 Figure 5.3.8: Transverse strains measured at midspan under the 35 kip patch load applied at midspan during the 15,000 cycles completed during the environmental effect simulation ............................. 142 Figure 5.3.9: Load placement during transverse load distribution tests for Concept 1 and Concept 2 laboratory specimens ..................................................................................................................... 144 Figure 5.3.10: Longitudinal curvature in north and south panels in Span 2 of Concept 1 laboratory bridge under 35 kip patch load applied at midspan centered over south panel ................................ 145 Figure 5.3.11: Longitudinal curvature in north and south panels in Concept 2 laboratory bridge under 35 kip patch load applied at the quarter points centered over south panel. ..................................... 146 Figure 5.3.12: Intentionally roughened surface, by means of raking, of top web of precast beam used for the construction of Concept 2 laboratory bridge specimen ........................................................ 147 Figure 5.3.13: Photograph of tri-actuator load setup and transverse loading beam utilized during ultimate load tests; shown for the Concept 2 laboratory bridge test ................................................ 149 Figure 5.3.14: Longitudinal strains measured through the section depth at midspan of north panel 20 in. from precast joint with 458 kip applied Load in Concept 2 laboratory bridge specimen ............... 152 Figure 5.4.1: Location of reference line for measurement of vertical location of cracking in core specimens ...................................................................................................................................... 154
xviii Figure 5.4.2: Concept 1 laboratory bridge specimen partitioning for saw cutting procedure ............. 157 Figure 5.4.3: Delamination at the PC â CIP interface in the East transverse face of section number 7 of the Concept 1 Laboratory bridge specimen ..................................................................................... 158 Figure 5.4.4: Concept 2 laboratory bridge specimen partitioning for saw cutting procedure ............. 159 Figure 5.4.5: Delamination at the PC â CIP interface observed on the West face of section number 3 of the Concept 2 laboratory bridge specimen ...................................................................................... 159 Figure 5.4.6: Evidence of diagonal cracking in the trough region on the east face of panel 2 in the Concept 2 laboratory bridge ........................................................................................................... 160 Figure 6.1.1: Elevation and plan views of subassemblage specimen. The x-axis was aligned along the North direction and corresponded with the longitudinal joint. Positive x pointed North, positive y pointed West, positive z, was vertically upward .............................................................................. 165 Figure 6.1.2: Photograph of deck reinforcement utilized for the subassemblage specimens ............. 166 Figure 6.1.3: Layout for SSMBLG1-Control1, SSMBLG3-HighBars, SSMBLG4-Deep, SSMBLG5-No.6Bars, and SSMBLG7-Control2. Transverse hooked bars are shown in blue; cage reinforcement is shown in green ............................................................................................................................................. 167 Figure 6.1.4: Layout for SSMBLG2-NoCage. Transverse hooked bars are shown in blue .................... 168 Figure 6.1.5: Elevation view of SSMBLG3-HighBars and increased deck depth to provide additional cover for the shrinkage reinforcement in the deck .......................................................................... 169 Figure 6.1.6: Failure of SSMBLG3-HighBars due to fracture of the transverse hooked reinforcement near the CIP - precast web interface ............................................................................................... 170 Figure 6.1.7: Specimen layout for SSMBLG6-Frosch. Transverse hooked bars are shown in blue; cage reinforcement is shown in green .................................................................................................... 172 Figure 6.1.8: Precast flange surface condition in SSMBLG7-Control2 before and after patching of the flange to provide a smooth surface condition ................................................................................. 173 Figure 6.1.9: Photograph of SSMBLG7-Control2 to illustrate manufacturing error in placement of transverse hooked bars .................................................................................................................. 174 Figure 6.2.1: Instrumentation layout for subassemblage specimens. Overlap of gages not shown for clarity ............................................................................................................................................ 175 Figure 6.2.2: Plan view of instrumentation near origin face of subassemblage specimens ................ 176 Figure 6.2.3: Location of LVDT instrumentation utilized for subassemblage tests. Vertical measurements for placement of instrumentation originated from bottom of 1 in. precast chamfer . 177 Figure 6.3.1: Clamping system developed to simulate restraint near joint region on subassemblage specimens. Section AA is shown in Figure 6.3.2 ............................................................................... 179 Figure 6.3.2: Section view of clamping assembly and subassemblage specimen, parallel to joint, illustrating exaggerated curvature of L-section (top) and wide flange section (bottom) due to eccentricity of tensioned threaded rods .......................................................................................... 180 Figure 6.3.3: Separation of East precast section from CIP concrete during testing of SSMBLG3-HighBars before the implementation of the vertical clamping assembly ........................................................ 181
xix Figure 6.3.4: Clamping system used to provide rotational restraint of the precast members from the CIP concrete during the subassemblage tests and loading apparatus consisting of 1 in. HSS and neoprene bearing pad .................................................................................................................... 182 Figure 6.6.1: Measured transverse mechanical strains in the subassemblage specimens based on the number of days after the placement of the CIP concrete ................................................................. 190 Figure 6.6.2: Photograph of development of two primary vertical cracks near the precast flange on origin face of SSMBLG6-Frosch. Applied load was 49.0 k (152 percent of PCR-pred) .............................. 191 Figure 6.6.3: Photograph of cracking near the vertical precast web-CIP interface, including cracking through the precast flange and diagonal cracking due to the clamping assembly in SSMBLG6-Frosch ...................................................................................................................................................... 192 Figure 6.6.4: Location of measurement of width and length of crack observed on origin and end faces of subassemblage specimens.......................................................................................................... 193 Figure 6.6.5: Measurement of crack width during subassemblage testing ........................................ 194 Figure 6.6.6: Maximum1 crack widths measured on the origin face2 of selected specimens3 before each set of cycles ................................................................................................................................... 195 Figure 6.6.7: Maximum1 crack widths measured on the end face2 of selected specimens before each set of cycles ................................................................................................................................... 197 Figure 6.6.81: Difference in crack width between the origin and end face (origin minus end) ............ 200 Figure 6.6.9: LVDT displacement measured via the Mid LVDT at the origin face ............................... 202 Figure 6.6.10: LVDT displacement measured via the Mid LVDT at the end face ................................ 203 Figure 6.6.11: Difference in LVDT displacements between the origin and end face (origin minus end) ...................................................................................................................................................... 205 Figure 6.6.12: Measurement of the length of crack during subassemblage testing. Red dots illustrate path of crack .................................................................................................................................. 206 Figure 6.6.13: Normalized crack length on the origin face of selected specimens before each set of cycles............................................................................................................................................. 207 Figure 6.6.14: Normalized crack length on the end face of selected specimens before each set of cycles ...................................................................................................................................................... 207 Figure 6.6.15: Difference in normalized crack length between the origin and end face (origin minus end) of selected specimens ............................................................................................................ 209 Figure 6.6.16: Slope of linear fit line for load versus 1.0 level strain data at middle cross section in SSMBLG1-Control1 ......................................................................................................................... 210 Figure 6.6.17: Slope of linear fit line for load versus 1.5 level strain data at middle cross section in SSMBLG1-Control1 ......................................................................................................................... 211 Figure 6.6.18: Slope of linear fit line for load versus 2.0 level strain data at middle cross section in SSMBLG1-Control1 ......................................................................................................................... 212 Figure 6.6.19: Slope of linear fit line for load versus 1.0 level strain data at origin cross section in SSMBLG1-Control1 ......................................................................................................................... 213
xx Figure 6.6.20: Slope of linear fit line for load versus 1.5 level strain data at origin cross section in SSMBLG1-Control1 ......................................................................................................................... 214 Figure 6.6.21: Load at which cracking was first observed in gages at middle cross section as determined from concrete embedment resistive strain gages ......................................................... 215 Figure 6.6.22: Load at which cracking was first observed in gages at origin cross section as determined from strain gages ........................................................................................................................... 216 Figure 6.6.23: Strain gage identification utilized for investigation of uniformity of cracking along the length of the precast joint. Pairs of hooks spaced at 18 in. and the cage reinforcement are not shown in the drawing for clarity ................................................................................................................ 218 Figure 6.6.24: Load and location at which cracking was detected for SSMBLG1-Control1 .................. 219 Figure 6.6.25: Load and location at which cracking was detected for SSMBLG2-NoCage ................... 220 Figure 6.6.26: Load and location at which cracking was detected for SSMBLG4-Deep ....................... 221 Figure 6.6.27: Load and location at which cracking was detected for SSMBLG5-No.6Bars ................. 222 Figure 6.6.28: Load and location at which cracking was detected for SSMBLG6-Frosch ..................... 224 Figure 6.6.29: Load and location at which cracking was detected for SSMBLG7-Control2 .................. 225 Figure 6.6.30: Predicted tensile reinforcement stress demands as a function of applied loading in subassemblage specimens1 ............................................................................................................ 227 Figure 6.7.1: Coring locations in subassemblage specimens ............................................................. 229 Figure 6.7.2: Location of reference line for measurement of vertical location of cracking in core specimens ...................................................................................................................................... 230 Figure 8.0.1: A DBT concrete bridge being constructed .................................................................... 241 Figure 8.0.2: A typical DBT bridge connected by longitudinal joints with welded steel connectors .... 242 Figure 8.1.1: Orientation of joints and corresponding test specimens .............................................. 247 Figure 9.1.1: U-bar longitudinal joint specimen ............................................................................... 254 Figure 9.1.2: Headed bar longitudinal joint specimen ...................................................................... 254 Figure 9.1.3: U-bar transverse joint specimen ................................................................................. 255 Figure 9.1.4: Headed bar transverse joint specimen ........................................................................ 255 Figure 9.1.5: Flexural test set-up (Longitudinal Joint Test) ............................................................... 256 Figure 9.1.6: Tension test set-up (Transverse Joint) ......................................................................... 258 Figure 9.1.7: U-bar joint detail strain gage configuration ................................................................. 259 Figure 9.1.8: Headed bar joint detail strain gage configuration ........................................................ 259 Figure 9.1.9: Lacer bar strain gage configuration ............................................................................. 260 Figure 9.1.10: Specimen construction ............................................................................................. 261 Figure 9.1.11: Stress versus strain curves for Deformed Wire Reinforcement (DWR) and Stainless Steel (SS) ................................................................................................................................................ 265
xxi Figure 9.1.12: Connection detail, conceptual drawing ..................................................................... 266 Figure 9.1.13: Photo of the top connection detail ............................................................................ 266 Figure 9.1.14: Weld test set-up ....................................................................................................... 267 Figure 9.1.15: One pass weld failure ............................................................................................... 268 Figure 9.1.16: Moment versus deflection curves ............................................................................. 272 Figure 9.1.17: Moment-versus-curvature curves ............................................................................. 273 Figure 9.1.18: Cross Section used for theoretical calculations of the U-bar specimens ...................... 274 Figure 9.1.19: Cross section used for the theoretical calculations of the headed bar specimen ......... 274 Figure 9.1.20: Measured and theoretical moment-versus-curvature curves for the U-bar details ...... 276 Figure 9.1.21: Measured and theoretical moment-versus-curvature curves for headed bar details ... 276 Figure 9.1.22: Flexural crack patterns at failure ............................................................................... 278 Figure 9.1.23: Moment versus rebar strain curves for SB-1 .............................................................. 281 Figure 9.1.24: Moment versus rebar strain curves for WB-1 ............................................................ 282 Figure 9.1.25: Moment versus rebar strain curves for HB-1 ............................................................. 284 Figure 9.1.26: Total applied force versus deflection curves .............................................................. 285 Figure 9.1.27: Tension crack patterns at failure ............................................................................... 287 Figure 9.1.28: Total force versus rebar strain for WT-1 .................................................................... 289 Figure 9.1.29: Total force versus rebar strain for HT-1 ..................................................................... 291 Figure 9.2.1: WB-1 longitudinal joint specimen (Tested in Phase I) .................................................. 293 Figure 9.2.2: WB-2 longitudinal joint specimen .............................................................................. 293 Figure 9.2.3: WB-3 longitudinal joint specimen .............................................................................. 294 Figure 9.2.4: WB-4 longitudinal joint specimen .............................................................................. 294 Figure 9.2.5: WT-1 transverse joint specimen (Tested in Phase I) .................................................... 294 Figure 9.2.6: WT-2 transverse joint specimen ................................................................................. 295 Figure 9.2.7: WT-3 transverse joint specimen ................................................................................. 295 Figure 9.2.8: WT-4 transverse joint specimen ................................................................................. 296 Figure 9.2.9: Strain gage configuration for WB-3 and WT-3 ............................................................. 297 Figure 9.2.10: Strain gage configuration for WB-2, WT-2, WB-4, and WT-4 ...................................... 297 Figure 9.2.11: Moment versus deflection ....................................................................................... 301 Figure 9.2.12: Moment-versus-curvature ....................................................................................... 301 Figure 9.2.13: Cross sections, As of 1.24 in 2 ..................................................................................... 302 Figure 9.2.14: Cross sections, As of 1.86 in 2 ..................................................................................... 303 Figure 9.2.15: Measured and calculated moment versus deflection ................................................ 305
xxii Figure 9.2.16: Measured and calculated moment-versus-curvature ................................................ 307 Figure 9.2.17: Material properties used in Response 2000 .............................................................. 308 Figure 9.2.18: Flexural cracks at failure .......................................................................................... 311 Figure 9.2.19: Moment versus rebar strain for longitudinal joint tests ............................................ 314 Figure 9.2.20: Load versus deflection ............................................................................................. 316 Figure 9.2.21: Tensile cracks at failure ............................................................................................ 318 Figure 9.2.22: Deformation of lacer bar .......................................................................................... 319 Figure 9.2.23: Crack comparator used to measure tension crack widths .......................................... 320 Figure 9.2.24: Force versus rebar strain for transverse joint tests.................................................... 323 Figure 10.1.1: Cross section of optimized DBT girder ....................................................................... 327 Figure 10.1.2: Steel diaphragm connecting adjacent girders at midspan .......................................... 328 Figure 10.1.3: Proposed continuous longitudinal joint ..................................................................... 328 Figure 10.1.4: Cross section of bridge models .................................................................................. 329 Figure 10.1.5: Plan view of skewed bridge models .......................................................................... 330 Figure 10.1.6: Dimensions and wheel weights of the HL-93 live load ................................................ 331 Figure 10.1.7: Bridge components modeled by 3D finite elements ................................................... 332 Figure 10.1.8: Boundary conditions at pinned end ........................................................................... 333 Figure 10.1.9: Lane loading positions for moment ........................................................................... 335 Figure 10.1.10: Lane loading positions for shear .............................................................................. 336 Figure 10.1.11: Truck load positions for moment ............................................................................ 338 Figure 10.1.12: Truck load positions for shear ................................................................................. 340 Figure 10.1.13: Tandem load positions for maximum moment and shear ......................................... 342 Figure 10.1.14: Load positions for negative moment on bridge model B .......................................... 343 Figure 10.1.15: Cross section of Modified Bridge B .......................................................................... 344 Figure 10.1.16: Loading positions for negative moment on modified bridge model B ....................... 344 Figure 10.1.17: Moment and shear comparison in long-span bridge (A) ........................................... 346 Figure 10.1.18: Moment and shear comparison in short-span bridge (B) .......................................... 347 Figure 10.1.19: Span effect on forces in joint ................................................................................... 348 Figure 10.1.20: Effect of girder depth on forces in joint ................................................................... 350 Figure 10.1.21: Effect of girder spacing on forces in joint ................................................................. 352 Figure 10.1.22: Effect of bridge skew on forces in joint .................................................................... 354 Figure 10.1.23: Effect of number of loaded lanes (single-lane loading (left column bar for each model) versus multi-lane loading (right column bar for each model)) .......................................................... 355
xxiii Figure 10.1.24: FE Model ................................................................................................................ 359 Figure 10.1.25: Impact of cracking on forces ................................................................................... 360 Figure 11.2.1: Compressive strength development of the neat grouts per ASTM C 109 and extended grouts per ASTM C 39. (âhâ=hour; âdâ=day) .................................................................................... 377 Figure 11.2.2: Truncated flow cone spread values per ASTM C 1437 for neat gouts and extended gouts ...................................................................................................................................................... 378 Figure 11.3.1: ASTM C882 Test: (a) Test mold and dummy section (b) Completed slant shear cylinders ready for testing (c) Test setup ....................................................................................................... 383 Figure 11.3.2: ASTM C882 Test Failure Modes (a), (b) and (c)* ......................................................... 383 Figure 11.3.3: Specimen preparation per ASTM C 1543 ................................................................... 385 Figure 11.3.4: Chloride concentration determination with ISE ......................................................... 385 Figure 11.3.5: Chloride content profile after 90-day ponding test .................................................... 386 Figure 11.3.6: ASTM C666 Freezing-and-Thawing Durability Test: (a) Freezing-and-thawing apparatus, (b) Fundamental transverse frequency test, (c) Failure of RSLP Mix 2 specimens .............................. 388 Figure 11.3.7: AASHTO PP34 test setup .......................................................................................... 389 Figure 11.3.8: Steel ring strain versus specimen age for HPC Mix 1 .................................................. 389 Figure 12.1.1: Dimensions of longitudinal joint specimen ................................................................ 393 Figure 12.1.2: Reinforcement layout in longitudinal joint specimen ................................................. 394 Figure 12.1.3: Strain gage layout ..................................................................................................... 395 Figure 12.1.4: Panel fabrication ...................................................................................................... 396 Figure 12.1.5: Profile of joint surface .............................................................................................. 397 Figure 12.1.6: Longitudinal joint specimen before and after grouting .............................................. 398 Figure 12.1.7: Longitudinal joint specimen test setup ...................................................................... 400 Figure 12.1.8: Simple support boundary condition at edge of longitudinal joint specimen ................ 401 Figure 12.1.9: DEMEC points ........................................................................................................... 402 Figure 12.1.10: Test setup for applying fatigue forces ...................................................................... 403 Figure 12.1.11: FE model for load determination ............................................................................. 406 Figure 12.1.12: First two cycles of fatigue shear (FS) loading applied ............................................... 408 Figure 12.1.13: C-N curves for flexure and flexure-shear specimens ................................................. 411 Figure 12.1.14: Moment-curvature curves for flexure and flexure-shear specimens ......................... 414 Figure 12.1.15: Load-deflection curves of flexure and flexure-shear specimens ................................ 416 Figure 12.1.16: RD-N curves for flexure and flexure-shear specimens .............................................. 418 Figure 12.1.17: Cracks at joint-panel interface ................................................................................ 419 Figure 12.1.18: Moment-crack width curves for static flexure and static flexure-shear specimens .... 422
xxiv Figure 12.1.19: CW-N curves for fatigue flexure and fatigue flexure-shear specimens ...................... 424 Figure 12.1.20: Transverse crack in FF-7 test (circled in red)............................................................. 425 Figure 12.1.21: MS-N curves for fatigue flexure and fatigue flexure-shear specimens ....................... 426 Figure 12.1.22: Moment-strain curves for flexure and flexure-shear specimens ............................... 427 Figure 12.1.23: Specimen failures for flexure specimens .................................................................. 428 Figure 12.1.24: Cracks at the bottom of the flexure specimens (the joint interfaces are marked with dashed lines) ................................................................................................................................. 429 Figure 12.1.25: Specimen failures for flexure-shear specimens ........................................................ 430 Figure 12.1.26: Cracks at the bottom of the flexure-shear specimens (the joint interfaces are marked with dashed lines) .......................................................................................................................... 431 Figure 13.1.1: Dimension of transverse joint (tension) specimen ..................................................... 434 Figure 13.1.2: Reinforcement layout in transverse joint (tension) specimen ..................................... 435 Figure 13.1.3: Strain gage configuration for transverse joint (tension) specimen ............................. 436 Figure 13.1.4: Panel fabrication ...................................................................................................... 437 Figure 13.1.5: Profile of joint surface after sandblasting .................................................................. 438 Figure 13.1.6: Transverse joint (tension) specimen before and after grouting .................................. 439 Figure 13.1.7: Tension test setup .................................................................................................... 440 Figure 13.1.8: Load-deflection curves of the tension specimens ....................................................... 443 Figure 13.1.9: Load-crack width curves of static tension specimens ................................................. 445 Figure 13.1.10: Cracks within the Joint ............................................................................................ 446 Figure 13.1.11: CW-N curve ............................................................................................................ 447 Figure 13.1.12: MS-N curves of fatigue tension specimens............................................................... 448 Figure 13.1.13: Load-strain curve .................................................................................................... 449 Figure 13.1.14: Cracking in transverse joint (tension) specimens ..................................................... 451 Figure 13.1.15: Deformation of lacer bar ......................................................................................... 452 Figure 14.1.1: Dimension of Slab Specimen ..................................................................................... 455 Figure 14.1.2: Reinforcement Layout in Slab ................................................................................... 456
xxv Executive Summary Introduction The aging highway bridge infrastructure in the United States is subjected to increasing traffic volumes and must be continuously renewed while accommodating traffic flow. Speed of construction, especially for the case of bridge replacement and repair projects, is a critical issue. Disruption of traffic and inconvenience to motorists, let alone major safety issues arising from detours, has encouraged the development of rapid construction methods. The issue of speed of construction, combined with higher labor costs and more variable quality control associated with on-site concrete casting, construction and motorist safety issues, political pressures, and environmental concerns, has paved the way for further increase in the use of precast elements to speed construction. Depending on the specific site conditions, the use of prefabricated bridge systems can minimize traffic disruption, improve work-zone safety, minimize impact to the environment, improve constructability, increase quality, and lower life-cycle costs. This technology is applicable and needed for both existing bridge replacement and new bridge construction. For many deficient bridges in the United States on the waiting list for replacement, it is imperative that new bridge construction be as economical as possible and yet be long lasting and nearly maintenance free. The focus of this study was to develop design specifications, construction specifications, and examples for the design and construction of durable CIP reinforced concrete connections for precast deck systems that emulate monolithic construction, considering issues including durability and fatigue, while increasing speed of construction. The typical sequence of erecting bridge superstructures in the United States is to erect the precast prestressed concrete or steel beams, place either temporary formwork or stay-in-place formwork such as steel or concrete panels, place deck reinforcement, cast deck concrete, and remove formwork if necessary. This project focused on systems that reduce the need to place and remove formwork thus accelerating on-site construction and improving safety. The three systems considered to accomplish these objectives were identified during a 2004 Prefabricated Bridge Elements and Systems International Scanning tour. These systems included: (1) a precast composite slab span system (PCSSS) for short to moderate span structures based on the French Poutre Dalle system, (2) full-depth prefabricated concrete decks, and (3) deck joint closure details (e.g., decked-bulb-tee (DBT) flange connections) for precast prestressed concrete girder systems for long-span structures. Each system uses precast elements that are brought to the construction site ready to be set in place and quickly joined together. Depending on the system, the connections are either transverse (i.e., across the width of the bridge) or longitudinal (i.e., along the length of the bridge). The first system, PCSSS, is an entire bridge system; whereas the other two systems investigated in the project represented transverse and longitudinal joint details to transfer moment and shear in precast deck panels and flanges of decked bulb tees. Because of the similarities in the latter two types of systems, they are grouped together in the report. Two types of connection concepts were explored with these details, looped bar details and two layers of headed bar details. Although both types of systems performed adequately in initial tests, the looped bar systems were deemed to be more practical for construction purposes and were investigated in the subsequent tests. Because this report covers two very different systems: (1) the precast composite slab-span system (PCSSS), which is an entire bridge system, and (2) transverse and longitudinal cast-in-place connection concepts to transfer moment and shear between precast deck panels and the flanges of precast decked bulb-Ts. The executive summary, as well as the report, is separated accordingly.
xxvi Precast Composite Slab Span System: Introduction Precast composite slab span systems (PCSSS) are a promising technology for the implementation of accelerated construction techniques for bridge construction. The bridge systems are composed of precast, inverted-T sections, fabricated off-site and delivered to the jobsite ready for erection. The inverted-T sections are assembled such that no formwork is required prior to the placement of the CIP deck, which considerably reduces construction time related to the placement and removal of formwork. Transverse load transfer is achieved through the development of transversely oriented reinforcement protruding from the precast members. Furthermore, improved quality of the main superstructure can be achieved due to the rigid quality control associated with the fabrication of precast members, which may be difficult to achieve in cast-in-place (CIP) bridge construction. Precast Composite Slab Span System: Research Methodology and Findings Several numerical and experimental investigations were completed and reviewed during the project related to issues of importance to the design and performance of precast composite slab span system (PCSSS) bridges. Included in this review was the work completed during a study commissioned by the Minnesota Department of Transportation which was the first Department of Transportation in the United States to implement this technology. The laboratory bridge specimen utilized during the Minnesota Department of Transportation study was subsequently made available for use with the project described herein. Numerical studies included an investigation of bursting and spalling stresses in the end zones of precast inverted-T sections, effects of spacing of transverse reinforcement in the joint region, and an investigation of the applicability of current design specifications for slab-type bridges to the design of PCSSS bridges for live load distribution factors and for consideration of effects of skewed supports. The two primary considerations that distinguish PCSSS bridges from slab-span bridges are (1) the required reinforcement to control reflective cracking above the longitudinal joint between the precast flanges, and (2) the effect of time-dependent restraint moments due to the composite nature of the system. With regard to the issue of reflective crack control, in addition to a numerical investigation regarding the effect of the transverse reinforcement, the issue was also studied in laboratory investigations of two large-scale laboratory specimens (i.e., Concept 1 and 2 bridges), as well as in subassemblage test specimens specifically designed to investigate crack control. The Concept 1 laboratory bridge was a two-span continuous bridge that included variations in a number of parameters including precast flange depth and end zone reinforcement details. It had been instrumented in the study for the Minnesota Department of Transportation to investigate the effects of restraint moment and potential development of reflective cracking. The Concept 1 specimen included No. 6 transverse hooked reinforcement embedded into the precast webs to provide load transfer and crack control in the joint region, as well as No. 5 cage stirrups which contributed to the crack control reinforcement. The nominal maximum spacing between transverse reinforcement was 12 in., similar to the detail of one of the first implementations of PCSSS bridges in the State of Minnesota, the Center City Bridge. The Concept 2 bridge was a simply-supported structure that included variations in the transverse reinforcement details across the precast joint. The horizontal shear reinforcement between the precast web and cast-in-place topping was eliminated in this structure. In the Concept 2 specimen, No. 4 embedded hooked reinforcement was used in the west half of the simple span, while No. 4 straight embedded bars mechanically connected to reinforcement in the precast webs were provided in the east half span. No. 3 cage stirrups were staggered in the Concept 2 laboratory bridge relative to the transverse reinforcement spaced at 18 in. to provide a maximum spacing of 9 in. between transverse reinforcement.
xxvii In the research described herein, the performance of both bridge specimens was investigated under various types of loading, including cyclic loading to simulate traffic, loading to simulate environmental effects, and loading to investigate load transfer between adjacent precast panels (both longitudinally and transversely). To simulate environmental effects, the structures were loaded to impose transverse strains above the longitudinal joint between the precast flanges that were observed due to thermal gradient effects in the Center City Bridge which was instrumented in the Minnesota Department of Transportation study. The structures were cycled at these strain levels to simulate more than 100 years of service life due to thermal gradient effects which were found to be much more significant than strains due to traffic loading. Following the cyclic load tests, the bridges were loaded above the nominal design flexural strengths to the limiting capacities of the actuators to investigate the effectiveness of composite action. Following the tests, cores and slices of the bridge were examined to investigate any residual cracks. In addition to the two large-scale laboratory bridge specimens, six subassemblage specimens were tested to investigate the relative performance of various reflective crack control reinforcement details. The subassemblage specimens were loaded to flexurally induce cracking above the longitudinal joint between the precast flanges. The size, quantity, and location of cracking were documented through a range of quasi-static and cyclic load tests. The subassemblages were instrumented internally to investigate the location of the crack along the depth and through the thickness of the structure. The results obtained from the internal instrumentation were compared to visual observations of crack initiation, width and depth observed on the faces of the specimen. There were a few considerations not included in the laboratory research or numerical study such as the connection between the precast elements and the substructure. These details were investigated primarily by means of examination of structural plans for existing PCSSS structures. Precast Composite Slab Span System: Conclusions and Recommendations The conclusions and recommendations are summarized by topic. Bursting, Splitting and Spalling Stresses - Significant changes have been made to the bridge design specification since 2007 with regard to end zone stresses, specifically in the terminology. Up to and including the 2007 specifications, the term âburstingâ was used to describe the end zone stresses, and were associated with design requirements likely developed specifically for I-girders, but applied to other shapes. The 2008 Interim specifications relaxed the placement requirements for wide-shallow sections, by allowing the designer to spread the end zone reinforcement, termed âsplittingâ reinforcement over a larger distance. In the case of pretensioned solid or voided slabs, the designer can substitute the section width for âh,â rather than using the section depth for âh.â According to this study, this may not be appropriate when trying to control spalling stresses. In addition, the terminology for the reinforcement described in this section of the design specifications is more correctly termed âspallingâ reinforcement rather than âsplittingâ or âburstingâ reinforcement. Experimental and numerical studies were completed to investigate the effects of end zone stresses on the precast prestressed inverted-T sections used in the PCSSS. The experimental results from the Concept 1 and 2 laboratory bridge investigations indicated that the 12 in. deep concrete sections had sufficient strength to resist tensile stresses induced in the transfer zone of the precast inverted-T sections at the time of release. Four unique end regions of the Concept 1 laboratory bridge specimen precast members, did not exhibit any evidence of cracking in those regions, even where vertical reinforcement was not provided in the end zones of those specimens. These findings were corroborated with the results of numerical studies that showed certain inverted-T members did not require spalling reinforcement, specifically those members with depths less than 22 in. for which the expected concrete
xxviii tensile strength was larger than the expected vertical tensile stresses due to the development of prestress. It was also found through numerical studies that the existing design requirements may not be conservative for deep inverted-T sections (i.e., greater than 22 in.). Larger amounts of spalling reinforcement than specified by the 2010 design specifications were found to be required. It was also found that the reinforcement should be placed as close to the end of the member as possible (i.e., within h/4 of the end of the member, where âhâ represents the depth of the member). The end region was the most critical region for the reinforcement to be located to address spalling stresses, even for the case of wide sections. Restraint Moment - It is important to consider the effects of restraint moments in the design of PCSSS bridges made continuous, or they should be designed as a series of simple spans. The current specification allows that, when the age of the girder is at least 90 days at the time of continuity, the computation of restraint moments is not required. The reasoning lies in the fact that, when the girder has aged beyond 90 days, the positive restraint moments caused by the precast beams due to time- dependent effects are minimal, and the negative restraint moments that may be generated can be accommodated by the negative moment reinforcement over the piers. In the case of PCSSS bridges made continuous by casting the CIP concrete on relatively young girders (e.g., 7 to 14 days old) to complete the continuous composite bridge system, the effects of positive restraint moments should be considered. In these cases the positive restraint moments due to time- dependent effects are typically dominated by the creep of the precast sections. It is recommended that the resulting positive time-dependent restraint moments developed at the piers be computed using the P-method. Research completed during the Minnesota Department of Transportation study and the current study has shown that restraint moments that develop due to thermal gradients can be significant, and should be considered in either case (i.e., whether or not time-dependent effects generate positive or negative restraint moments). The positive restraint moment effects attributed to the design thermal gradients can be an order of magnitude larger in some climates than the positive restraint moments due to time- dependent effects. The thermal gradients provided by the bridge design specification should be taken into consideration by calculating the resulting expected curvatures of each span treated as simply supported and then determining the moment required to overcome the end rotations and provide continuity. There may be little or no economic gain in continuity because of the large thermal restraint moments that develop and in some cases, continuity may require additional reinforcement in the precast sections (i.e., larger than would be required for a simply-supported design). As a consequence it is not conservative to design the PCSSS bridges as simply supported and add positive moment reinforcement across the piers for integrity reinforcement without considering the effects of the restraint moments that can be generated due to the thermal gradient effects. Live Load Distribution Factors - Numerical modeling was combined with observations from a live load truck test on the field-instrumented Center City Bridge along with load distribution tests on the laboratory bridge specimens (i.e., Concept 1 and Concept 2) to determine the applicability of current live load distribution factors in the bridge design specification for slab-type bridges to the PCSSS. The numerical models illustrated that the longitudinal curvatures measured in the precast slab span system with a reflective crack extending to within 3 in. of the extreme compression fiber and a tandem load greater than that which could be physically applied in the field resulted in longitudinal curvatures which were only 84 percent of the longitudinal curvatures predicted using the AASHTO LRFD (2010) load distribution factors for monolithic concrete slab span bridges, suggesting that PCSSS-type
xxix superstructures could reasonably and conservatively be designed using the current live load distribution factors for monolithic slab-type bridges. Furthermore, the live load truck tests on the Center City Bridge suggested that the measured longitudinal curvatures were approximately three times less than those calculated using monolithic slab span equations. In addition, the measured longitudinal curvatures were consistently conservative when compared to monolithic slab span FEM models. The conservatism in the factors for monolithic slab span bridges was sufficient to cover the cases of the PCSSS bridges even considering the potential effects of reflective cracking as discussed above. Load distribution tests on Span 2 of the Concept 1 laboratory bridge and the Concept 2 laboratory bridge included an investigation of the transverse load distribution between adjacent precast panels. Both spans showed good load transfer capabilities across the longitudinal joint during intermittent tests conducted throughout the investigation of the laboratory bridge specimens to extend the reflective crack. In both cases, little variation in the measured longitudinal curvatures with crack growth was observed in the unloaded panels, which suggested that load was effectively transferred across the longitudinal joint from the loaded panel despite the presence and increase in the size of reflective cracking induced in/near the joint. In summary, the numerical and experimental studies in regards to live load distribution factors indicated that the PCSSS was well represented by monolithic FEM models, suggesting that the discontinuity at the precast joint did not significantly affect the load distribution characteristics of the system. Also, the performance of the large-scale laboratory bridge specimens reinforced the notion that the system provided sufficient transverse load distribution, with and without the presence of reflective cracking near the joint region. Skew - Numerical modeling was applied to simply-supported monolithic and jointed (to simulate the PCSSS discontinuity at the adjacent precast flange interface) bridge models with skewed supports ranging up to 45 degrees. Three independent load cases were investigated, which included a 35 kip load individually applied over a 12 by 12 in. patch at both quarter points and at midspan for each model. For each load case, the largest horizontal shear stress in the plane above the precast joint nearest the loading was determined. The small variation and consistency between the models considering a joint between precast sections with a 3 in. flange and a monolithic structure suggested that the effect of the joint in precast composite slab span construction was not expected to significantly affect the performance of the system in skewed applications, and the design of skewed PCSSS bridges could be completed assuming a monolithic slab span system. Composite Action and Horizontal Shear Strength - To conclude the laboratory tests, the large-scale bridge specimens were loaded above the nominal flexural capacities to the limiting capacities of the actuators to investigate the ability for the precast slab span sections to remain composite with the CIP concrete topping. Placement of reinforcement for horizontal shear was observed to be difficult and time consuming for the fabricator, especially when finishing the top web surfaces. Furthermore, the reinforcement extending from the precast webs for horizontal shear extended out of the precast section with minimal clearance between the hook and the precast web surface to avoid interference with placement of the deck reinforcement in the field. In initial field applications of the PCSSS, the low clearance of this horizontal shear reinforcement may have limited its effectiveness because aggregate was unable to flow below the returned stirrups. Span 2 of the Concept 2 laboratory bridge was designed with the same horizontal shear layout utilized in the Center City Bridge, which satisfied the 2005 bridge design requirements. Span 1 of the Concept 1 laboratory bridge was designed with fewer horizontal shear ties than were used in Span 2 and in the Center City Bridge, and which did not satisfy the
xxx minimum horizontal shear reinforcement requirements of the 2005 bridge design requirements. The Concept 2 laboratory bridge was designed and constructed with no horizontal shear ties. In both bridges, the surface condition of the precast member was roughened to a surface consistent with a 1/4 in. rake. In the tests on both spans of the Concept 1 laboratory bridge and on the Concept 2 laboratory bridge, the sections were observed to remain composite well beyond service load levels, through the full range of loading to the maximum capacity of the loading system, which was in excess of the predicted nominal capacity of the Concept 1 and 2 bridges. The horizontal shear stress estimated in the Concept 2 system at the precast-CIP interface was subsequently calculated to be 135 psi. As the bridge had not yet been loaded to failure due to the limited capacity of the actuators, it may have been possible to generate even larger horizontal shear stresses. The results of the laboratory tests suggest that the bridge design specification should allow for the design of precast slab span structures without horizontal shear ties, and allow for the development of a maximum factored horizontal shear stress of 135 psi in sections with intentionally roughened surfaces (i.e., 1/4 in. rake) unreinforced for horizontal shear. Reflective Crack Control Across the Longitudinal Joint between Precast Flanges - Reflective cracking was intentionally induced in the Concept 1 and Concept 2 large-scale laboratory specimens to investigate the performance of the PCSSS through a range of loading that was designed to simulate both fatigue performance due to vehicular loading, as well as the influence of environmental effects. The performance of both spans of the Concept 1 laboratory bridge and the Concept 2 laboratory bridge was observed to adequately control cracking in the precast joint region throughout loading to simulate traffic and environmental effects related to the thermal gradient. Reflective cracking was also monitored throughout the range of testing for seven subassemblage specimens to quantify the relative performance of the respective design details for reflective crack control in each specimen. The ability for each specimen to control the width of cracking was desirable, as large cracks were expected to cause degradation of the longitudinal joint region including providing a potential avenue for the ingress of moisture and chlorides. Each of the subassemblage specimens performed adequately throughout the range of loading, though variations in the extent of cracking indicated some relative differences. The two specimens with the largest reinforcement ratios for crack control, SSMBLG5-No.6Bars (Ïcr=0.0061) and SSMBLG6-Frosch (Ïcr=0.0052), performed well relative to the remaining specimens. In these two specimens, measured crack widths were consistently smaller than the remaining specimens. SSMBLG7-Control2 also indicated better than average performance through visual observations; however the analysis of the embedded instrumentation suggested that the behavior of this specimen was similar to the specimens in the group not including SSMBLG5-No.6Bars and SSMBLG6-Frosch. The behavior of SSMBLG7-Control2 was attributed to a relatively smooth precast flange surface achieved prior to the placement of the CIP concrete (which was done in anticipation of studying a debonded flange surface, which was abandoned to allow for a second control specimen to be tested). The relatively smooth flange surface was expected to better distribute transverse stresses across the precast flanges in the joint region, thereby reducing the potential stress concentration at the interface between the adjacent precast flanges which created a longitudinal joint, however it was observed via an analysis of the horizontal crack propagation using the concrete embedment resistive strain gages that a single crack was present internally in the specimen, suggesting that the smooth flange surface did not distribute the transverse stress adequately well so as to promote the development of multiple cracks. A completely debonded surface, however, was not expected to be desirable, as it would likely promote delamination of the horizontal precast flange-CIP
xxxi interface, which was expected to promote cracking at the vertical precast web, where cage reinforcement was not present to aid in the control of cracking. In the subassemblage study, the maximum transverse 9 in. spacing for crack control appeared to be sufficient as long as enough reinforcement was provided to ensure that the reinforcement did not yield upon cracking. This was evident through the good performance of the SSMBLG5-No.6Bars and SSMBLG6-Frosch specimens. The maximum transverse reinforcement spacing was further investigated by evaluating the performance of the Concept 1 and 2 laboratory bridges which provided more realistic boundary conditions in the longitudinal joint region above the precast flanges. In this study, it was found that the 9 in. maximum transverse reinforcement spacing provided in the Concept 2 laboratory bridge did not correlate with an improvement in the control of cracking near the longitudinal trough area relative to the 12 in. maximum spacing provided in the Concept 1 spans, and therefore an economical design may favor 12 in. transverse reinforcement spacing to 9 in. spacing with no expected reduction in performance. An increase in the maximum transverse reinforcement spacing to 18 in. is not recommended, primarily because cracking in SSMBLG2-NoCage (which was reinforced with only transverse No. 4 bars spaced at 18 in.) was generally largest. The crack widths in SSMBLG2-NoCage increased with the least increase in the applied load relative to the other subassemblage specimens which had transverse reinforcement spacings no larger than 9 in. The subassemblage specimen with transverse reinforcement spacing no larger than 9 in. was observed to provide acceptable crack control. Furthermore, little difference was observed between the performance of the sections of the Concept 1 laboratory bridge where reflective cracking was observed, with No. 6 transverse hooked bars, and the performance of the Concept 2 laboratory bridge where reflective cracking was observed, with No. 4 transverse hooks. There was, however, a noticeable increase in the relative performance of SSMBLG5- No.6Bars compared to SSMBLG1-Control1, in which the only nominal difference was the larger bars in the former specimen. Because the increased performance observed in SSMBLG5-No.6Bars, which performed similar to SSMBLG6-Frosch, was achieved with larger bars and a maximum transverse reinforcement spacing of 9 in., it was suggested that a design with No. 6 bars and less cage reinforcement was likely to be more economical and easier to implement in the field than the closely spaced reinforcement cage provided in SSMBLG6-Frosch, which had a 4.5 in. bar spacing. Design Recommendations and Examples â Recommended changes to the bridge design and construction specifications are proposed to implement this promising new system. The PCSSS bridge design guidelines cover both component and system issues including âspallingâ reinforcement, load distribution, effect of restraint moments, composite action, and reinforcement to control reflective cracking. Two MathCAD® examples were created to illustrate the design issues associated with a simply- supported PCSSS and a three-span system made continuous. Because of the effects of thermal gradients in generating large restraint moments, it is recommended that the PCSSS bridges be designed as a series of simply-supported spans. Longitudinal and Transverse Joints in Decked Bulb-T (DBT) and Full-Depth Precast Panel on Girder Systems: Introduction Two issues that limited the PCSSS bridge concept with regard to the potential for accelerated bridge construction applications were (1) the significant use of CIP to complete the composite system, which would slow the construction process, and (2) the limitation of the system to short- to moderate- span lengths. As a consequence, the study included CIP connection concepts that minimized the use of CIP by
xxxii limiting its application to the joints between the flanges of decked bulb-Tâs or between full-depth precast deck panels on girders. The investigated joints used two layers of reinforcement to provide the ability to transfer moment as well as shear through the deck. Two types of details were investigated to reduce the width of the joint: U-bar details (with deformed wire reinforcement (DWR) and stainless steel (SS)) and headed reinforcement details. Longitudinal and Transverse Joints in Decked Bulb-T (DBT) and Full-Depth Precast Panel on Girder Systems: Research Methodology and Findings Two types of details were investigated to reduce the width of the joint: U-bar details (with deformed wire reinforcement (DWR) and stainless steel (SS)) and headed reinforcement details. Initial tests were conducted using monolithic specimens that contained these details to simulate longitudinal and transverse joint connection concepts (i.e., flexural and tension test specimens, respectively). Based on the performance of the initial tests, the most promising connection concept in terms of behavior, constructability and cost, was investigated in additional tests where parameters were varied to refine the proposed connection concepts. Effects of variables including overlap lengths, rebar spacings, and concrete strengths were investigated. Based on capacity, service level crack widths, constructability, and cost, the U-bar detail, with No. 5 equivalent deformed wire reinforcement at 4.5 in. spacing with 6 in. overlap length and two transverse lacer bars was recommended for the longitudinal and transverse joints. The tests were based on uncoated reinforcement. If epoxy-coated reinforcement was used, larger joint widths may be required to develop the reinforcement across the joint. An alternative is to use stainless steel reinforcement which performed well in the initial study, but was an expensive alternative. The investigation included the development of performance specifications to achieve high performance durable closure pour (CP) materials for both overnight cure and 7-day cure applications. Based on extensive literature reviews and the experimental investigation, performance criteria for selecting durable CP materials were developed as listed in Tables 1 and 2.
xxxiii Table 1: Proposed performance criteria of CP materials Performance Characteristic Test Method Performance Criteria Compressive Strength (CS), ksi ASTM C39 modified 6.0â¤CS @ 8 hours (overnight cure) @ 7 days (7-day cure) Shrinkagea(S), (Crack age, days) AASHTO PP34 modified 20<S Bond Strength (BS), psi ASTM C882 modified 300<BS Chloride Penetrationb(ChP), (Depth for Percent Chloride of 0.2% by mass of cement after 90-day ponding, in) ASTM C1543 modified ChP<1.5 Freezing-and-thawing Durability (F/T), (relative modulus after 300 cycles) ASTM C666 Procedure A modified Gradec 1 Grade 2 Grade 3 70%â¤F/T 80%â¤F/T 90%â¤F/T a: No S criterion need be specified if the CP material is not exposed to moisture, chloride salts or soluble sulfate environments. b: No ChP criterion need be specified if the CP material is not exposed to chloride salts or soluble sulfate environments. c: Grades are defined in Table 2. Table 2: Application of CP material grades for freezing-and-thawing durability Freezing- and- thawing Durability (F/T) Is the concrete exposed to freezing- and-thawing environments? Yes Is the member exposed to deicing salts? Yes Will the member be saturated during freezing? Yes. Specify F/T- Grade 3 No. Specify F/T- Grade 2 No. Specify F/T- Grade 1 No. F/T grade should not be specified. Numerical studies of bridge systems were conducted with a number of variations to investigate service static and fatigue loadings that might be expected in the longitudinal and transverse joint connection concepts. The analytical parametric study considered parameters such as different loading locations, effect of bridge width, design truck and lane loading versus design tandem and lane loading, girder geometry (depth, spacing and span), bridge skew, single-lane loading versus multi-lane loading, and impact of cracking of the joints. Through this investigation, a database of maximum forces to be expected in the joint was developed. These forces were subsequently used to determine the fatigue loading demand for the large-scale longitudinal joint specimen (flexure and shear-flexure) tests and the large-scale transverse joint specimen (tension) tests. Large-scale longitudinal and transverse jointed specimens were fabricated to investigate the flexure and flexure-shear behavior of the longitudinal joints and the tension behavior of the transverse jointed specimens. The tension tests on the transverse jointed specimens were intended to simulate continuity provided by the joints over the piers, where it was assumed that the deck would transmit tension
xxxiv equilibrated by compression in the girder. The large-scale specimens were fabricated with the most promising connection detail which was a U-bar connection concept fabricated with deformed wire reinforcement (DWR). The specimens were subjected to static and fatigue tests with the loads determined in the numerical parametric study. The tests were evaluated in terms of load-deformation response, strain distribution, crack control, and strength. The studies indicated that the proposed longitudinal joint detail had sufficient strength, fatigue characteristics, and crack control for the maximum service loads determined from the analytical studies and was deemed to be a viable connection system to provide continuity in jointed deck systems over piers. The tests also confirmed that the U-bar detail was a viable connection system for the transverse joint. The joint with the 7-day cure material was able to achieve higher strengths which might be attributed to the section with the lower strength overnight cure material being unable to fully develop the reinforcement. To reduce the crack sizes in the joints, it is proposed to reduce the service stresses in the joints. This could be accommodated economically by using more lower-grade reinforcement (i.e., Grade 60 rather than Grade 75 bars). Longitudinal and Transverse Joints in Decked Bulb-T (DBT) and Full-Depth Precast Panel on Girder Systems: Conclusions and Recommendations The research completed during the NCHRP 10-71 study resulted in the development of a comprehensive design guide for the design and construction of longitudinal and transverse joints for full depth deck panels and decked bulb Tâs (DBTs). The design guide covers the detailing requirements for both loop bar and headed bar details. Adequate performance of these systems requires the use of lacer bars which improve the mechanical anchorage of these systems. Tests were conducted to investigate the behavior of these systems in shallow decks to emulate the flanges of DBTs. These shallow deck thicknesses required the use of tighter bends than presently allowed by the bridge design specifications and thus the recommendations are restricted to wire reinforcement and stainless steel reinforcement which may accommodate tighter bends due to their higher levels of ductility. Another important feature of these joints is the performance of the closure pour materials, which was also investigated through a series of laboratory tests that included an evaluation of the shrinkage and freeze-thaw durability characteristics of candidate overnight-cure and 7-day cure materials which might be considered in accelerated construction applications. Three MathCAD® examples were developed to illustrate the proposed detailing for longitudinal joints between decked bulb-Ts, longitudinal joints in full-depth precast panels on girders, and transverse joints.
1 Chapter 1 Introduction and Research Approach 1.0 Introduction The aging highway bridge infrastructure in the United States is subjected to increasing traffic volumes and must be continuously renewed while accommodating traffic flow. Speed of construction, especially for the case of bridge replacement and repair projects, is a critical issue. Disruption of traffic and inconvenience to motorists, let alone major safety issues arising from detours, has encouraged the development of rapid construction methods. The issue of speed of construction, combined with higher labor costs and more variable quality control associated with on-site concrete casting, construction and motorist safety issues, political pressures, and environmental concerns, has paved the way for wider acceptance for the use of precast elements to speed construction. Depending on the specific site conditions, the use of prefabricated bridge systems can minimize traffic disruption, improve work-zone safety, minimize impact to the environment, improve constructability, increase quality, and lower life-cycle costs. This technology is applicable and needed for both existing bridge replacement and new bridge construction. Over the past 50 years, thousands of short to medium span bridges have been built using precast concrete elements. Replacing an entire highway bridge including the substructure over a weekend has been accomplished through intense planning (Merwin 2003). In 1993, four bridges, each with spans ranging from 700 to 900 ft., were erected in less than 36 hours each including the substructures (Endicott 1993). Interestingly, the finished cost of the replacement project was significantly lower than the competing cast-in-place (CIP) alternatives. For many deficient bridges in the United States on the waiting list for replacement, it is imperative that new bridge construction be as economical as possible and yet be long lasting and nearly maintenance free (Tokerud 1979, Anderson 1972). There are a large number of papers on the use of precast concrete elements in bridge systems including research on the use of precast elements such as deck panels for rapid deck replacement. On deck elements alone, there are nearly 200 references. The papers include research studies conducted at a number of universities including the University of Illinois, Chicago (Issa, 1995), and University of Nebraska (Tadros, 1998). Strong momentum exists for the growing use of precast construction; two recent projects to investigate precast decked systems include NCHRP 12-65 Full-Depth, Precast-Concrete Bridge Deck Panel Systems and NCHRP 12-69 Design and Construction Guidelines for Long-Span Decked Precast, Prestressed Concrete Girder Bridges. The present project NCHRP 10-71 Cast-in-Place Reinforced Connections for Precast Deck Systems complements the work that was developed under those studies. NCHRP 12-65 addressed the development of transverse and longitudinal connections between full- depth, precast-concrete bridge deck panels, with emphasis on systems without overlays and without post tensioning through the connection. NCHRP 12-69 addressed I-beam, bulb-tee, or multi-stemmed girders with integral decks cast and prestressed with the girder. The girders are erected abutting flanges of adjacent units, and load is transferred between the adjacent units using connections developed in the project. The focus of the present project, NCHRP 10-71, was to develop specifications, guidelines, and examples for the design and construction of durable CIP reinforced concrete connections for precast deck systems that emulate monolithic construction, considering issues including speed of construction, durability, and fatigue. The typical sequence of erecting bridge superstructures in the United States is to erect the precast prestressed concrete or steel beams, place either temporary formwork or stay-in-place
