UPDATED RESEARCH FOR COLLISION DAMAGE …

1 UPDATED RESEARCH FOR COLLISION DAMAGE AND. REPAIR OF prestressed concrete BEAMS. final report Prepared for the National Cooperative Highway RESEARCH Program Transportation RESEARCH Board of The National Academies Kent A. Harries, , FACI, Jarret Kasan, University of Pittsburgh, Pittsburgh PA. Richard Miller, , FPCI, Ryan Brinkman University of Cincinnati, Cincinnati OH. May 2012. The information contained in this report was prepared as part of NCHRP Project 20-07, Task 307, National Cooperative Highway RESEARCH Program. SPECIAL NOTE: This report IS NOT an official publication of the National Cooperative Highway RESEARCH Program, Transportation RESEARCH Board, National RESEARCH Council, or The National Academies.

2 1. 2. EXECUTIVE SUMMARY. Collisions between over-height vehicles and bridges are becoming more commonplace. Recent catastrophic collapses have led to a re-evaluation of the condition of many prestressed structures resulting in bridges being posted and, in some cases, emergency decommissioning of structures. COLLISION DAMAGE , however, is generally far from catastrophic. Nonetheless, sound repair techniques are critical if additional DAMAGE (typically related to corrosion) is to be mitigated. The objectives of NCHRP 20-07/Task 307are to: i) develop criteria to evaluate whether to repair or to replace a prestressed concrete girder damaged by a vehicular impact; ii) identify the gaps in the available information and practices related to repair of COLLISION DAMAGE of prestressed girders; and iii) prepare a recommend practice report guide.

3 The primary deliverable of this project is the Guide to Recommended Practice for the Repair of Impact-Damaged prestressed concrete Bridge Girders. The Guide is provided as Appendix A of this report . The Guide serves to update the 1985 NCHRP report 280: Guidelines for Evaluation and Repair of prestressed concrete Bridge Members which remains a primary reference for this topic. The report identifies, using multiple examples, the nature of impact related DAMAGE . An extensive review of literature covering inspection, assessment and subsequent repair methods for impact-damaged prestressed concrete girders is presented in Chapter 1.

4 The emphasis of this review is on fiber-reinforced polymer (FRP) based repair techniques that have been developed since the publication of NCHRP report 280. An approach to rating impact damaged girders consistent with AASHTO bridge rating procedures is presented. Additionally, a minimum residual strength below which repair is not recommended is established. These approaches lead to establishing criteria for both the repair or replace' and repair or do nothing' decisions. Nine repair techniques are described; four are generally recommended as being practical for repairing impact damaged prestressed concrete girders: externally bonded carbon fiber reinforced polymer (EB- CFRP); externally bonded post-tensioned CFRP (bPT-CFRP); post-tensioned steel (PT-steel); and internal strand splicing.

5 In addition, external repairs in combination with strand splicing are discussed. In order establish limitations associated with repair methods, three prototype structures and over 440. individual DAMAGE and repair scenarios were considered. From these analyses and designs, DAMAGE classifications based on strand loss and limitations of repair techniques are established. Other practical geometric constraints associated with repair techniques are also described and quantified. 3. 4. TABLE OF CONTENTS. EXECUTIVE SUMMARY .. 3. LIST OF FIGURES .. 8. LIST OF TABLES .. 9. ACKNOWLEDGEMENTS .. 10. CHAPTER 1 BACKGROUND .. 11. Introduction.

6 11. Objective of NCHRP 20-07 Task 307 .. 12. Nature of Impact DAMAGE to prestressed concrete Bridge Elements .. 12. Factors Affecting Impact DAMAGE .. 12. Examples of Impact DAMAGE .. 17. Examples of Impact DAMAGE and its Repair .. 17. Examples of Impact DAMAGE and Temporary Repair .. 17. Assessment Techniques for prestressed concrete members .. 32. Visual and Manual 33. Surface Potential Survey/Half-Cell Potential Survey .. 33. Remnant Magnetism .. 33. Acoustic 34. Linear Polarization .. 35. Electrical Resistance .. 35. Fiber Optic Sensors .. 36. Impact-Echo .. 36. Electro-Chemical Impedance Spectroscopy (AC Impedance).

7 36. Surface Penetration Radar .. 36. Magnetic Field Disturbance .. 37. Electrical Time Domain Reflectometry (ETDR) .. 37. Magneto-Elastic .. 37. Computed Tomography (CT).. 37. Radiography .. 37. New Prototype Instrument for Measuring Remaining Prestress .. 38. Flat Jack Method .. 38. Nebraska Method .. 38. Hole Drilling Strain Gage Method .. 38. Repair, Rehabilitation and Retrofit Techniques for prestressed concrete Elements .. 39. Conventional Repair Methods .. 39. 5. Refined DAMAGE Classifications .. 48. Emerging Repair Materials and Methods .. 49. Case Studies .. 64. Aesthetic Repairs .. 68. Survey of Current State of 71.

8 CHAPTER 2 RESEARCH PROGRAM AND 73. RESEARCH Approach .. 73. Analysis of Girders .. 74. Assessment of Efficacy of Repair .. 75. Removal of Strands to Affect DAMAGE Spectra .. 76. Prototype Structures .. 76. Adjacent Box Girder Prototype AB .. 76. Spread Box Girder Prototype SB .. 77. I-Girder Prototype IB .. 79. Prototype and Repair Combinations .. 80. Limitations of Repair Techniques .. 83. Residual Capacity and Strengthening Limits .. 83. Limitations Associated with Girder Geometry .. 84. Limitations Associated with Repair 86. Results of Parametric Study .. 91. AB Prototype .. 91. SB Prototype .. 93. IB Prototype .. 95. DAMAGE Location Along Span.

9 103. Strand loss near 103. Synthesis of Parametric Study .. 104. Maximum Effect of CFRP Repair Techniques .. 105. Hybrid Repairs with Strand Splices .. 109. CHAPTER 3 RECOMMENDATIONS AND CONCLUSIONS .. 110. Guide to Recommended Practice for the Repair of Impact-Damaged prestressed concrete Bridge Girders .. 110. Gaps in Existing Knowledge and Need for Further RESEARCH .. 110. REFERENCES .. 111. NOTATION .. 120. APPENDIX A - Guide to Recommended Practice for the Repair of Impact-Damaged prestressed concrete Bridge 122. APPENDIX B AB Prototype Design 160. 6. APPENDIX C SB Prototype Design Example .. 172. APPENDIX D1 IB Prototype Design Example.

10 184. APPENDIX D2 IB 3-3-2 Hybrid Repair Design Example .. 198. APPENDIX D3 IB 3-3-2 PT-Steel Design Example .. 204. APPENDIX E Survey Responses .. 212. 7. LIST OF FIGURES. Figure 1 Examples of DAMAGE associated with vehicle impact.. 11. Figure 2 Examples of typical DAMAGE due to vehicle 12. Figure 3 Continuum of corrosion DAMAGE (Naito et al. 2006 and Harries 2006).. 14. Figure 4 Typical corrosion DAMAGE following impact-related 15. Figure 5 Repair methods presented in Shanafelt and Horn (1980).. 42. Figure 6 Strand splices (Shanafelt and Horn 1980).. 43. Figure 7 ABITB stressing gage (ABITB 2005).. 46. Figure 8 Schematic representations of CFRP applications.