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Extending the Life of Steel Girder Bridges through the Use of Post-Installed Shear Connectors

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Mike Engelhardt's presentation at the 2017 CTR Symposium http://ctr.utexas.edu/ctr-symp/

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Extending the Life of Steel Girder Bridges through the Use of Post-Installed Shear Connectors

  1. 1. Graduate Students: Kerry Kreitman, Hemal Patel, Amir Ghiami Azad TxDOT Project 0-6719 FERGUSON STRUCTURAL ENGINEERING LABORATORY Faculty: Michael Engelhardt, Todd Helwig, Rich Klingner, Eric Williamson Extending the Life of Steel Girder Bridges through the Use of Post-Installed Shear Connectors TxDOT: Darrin Jensen, Yuan Zhao, Dingyi Yang, Jamie Farris, Manuel Padron, Michelle Romage-Chambers, Paul Rollins, Leon Flourney
  2. 2. Develop technique to strengthen existing continuous multi-span non-composite steel girder bridges Project Objective
  3. 3. Older Non-composite Bridge steel girder concrete deckPost-installed shear connector
  4. 4. Critical Issue for Practical Application Minimize number of post- installed shear connectors. Need to employ partial composite design.
  5. 5. Bridge Deck Girder Flange Post-Installed Shear Connector: Adhesive Anchor
  6. 6. Strengthening Concept Partially composite Partially compositeNon-composite Positive moment Positive momentNegative moment Increased strength Increased strength Continuous, non-composite girder
  7. 7. YIELD YIELD Strengthening Concept: - Allow yielding in negative moment region / redistribute moment to positive moment regions - Strengthen positive moment regions with post-installed shear connectors using partially composite design
  8. 8. Research Questions • Is moment redistribution possible for partially composite girders (i.e., can we develop “shakedown”) ? • What is the fatigue strength of the adhesive anchor shear connector ? • How do we compute the shear connector fatigue demands for a partially composite girder? • Can we demonstrate good performance in large-scale tests? • Can we develop a straightforward design procedure?
  9. 9. Bridge Survey 7-8’ 7-8’ 7-8’ Compact W30-W36 shape 6.5” deck 50-100’ 50-100’ 50-100’ Cover plates top and bottom over piers 2-6 lanes Typically no skew or curvature 2-5 span unit No shear connectors Constructed 1950-1970 H15 or H20 design loads
  10. 10. 0 2 4 6 8 10 12 14 NumberofBridgeUnits Inventory HS Load Rating Initial Concept Studies Existing Strengthened (30%) Bridges can be significantly strengthened: Achieve HS 20 rating with low composite ratios and minimal redistribution Exceeds current standardsDeficient compared to current standards Conduct load rating for 13 bridges
  11. 11. Fatigue Testing
  12. 12. Fatigue Testing 0 10 20 30 40 50 60 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 StressRange,σr(ksi) Number of Cycles at Failure, N 0 0.01 0.02 0.03 0.04 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 Avg.SlipRange,sr(in) Number of Cycles at Failure, N = 0.66 = 0.86 Stress Range: Slip Range: = 101 − 13.6 log ≥ 15 = 0.0537 − 0.00725 log ≥ 0.008
  13. 13. Fatigue Testing Key Results: • Adhesive anchor shear connector has much better fatigue performance than welded shear studs. • Developed fatigue performance predictions based on both stress-range and on slip-range.
  14. 14. Large-Scale Testing Girder 1: 84’ long; 30% composite; 56 connectors Girder 2: 104’ long; 20% composite; 40 connectors
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  17. 17. Testing Program • Elastic testing – Before and after installing connectors • Fatigue and shakedown testing – In various orders for each span • Ultimate strength testing
  18. 18. Typical Shakedown Results Loading Pattern: 0 0.02 0.04 0.06 2 3 4 5 6 7 8 ChangeinDefl.(in) Cycle Number Shakedown criterion
  19. 19. Typical Ultimate Strength Results 0 50 100 150 200 250 0 3 6 9 12 15 Load(k) Total Deflection at Load Point (in) Predicted partially composite limit load Predicted non- composite limit load Connector failure Maximum load applied in shakedown test
  20. 20. Summary of Large-Scale Test Results Exceeded predicted strengths at all limit states – Shakedown was observed to occur in partially composite strengthened girders – Excellent high cycle fatigue performance – Fatigue loading did not adversely affect strength – Ultimate strength developed at predicted levels with significant ductility
  21. 21. Finite Element Modeling • ANSYS software • Extend experimental results • Evaluate fatigue demands on shear connectors using slip based approach Cross section view Isometric view (underside) Concrete deck Steel beam
  22. 22. -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0 8 16 24 32 40 48 56 64 72 80 SlipUnder~50kipP2Load(in) Distance Along Beam (ft) Slip Profiles 50 kips 50 kips ANSYS
  23. 23. Parametric Studies • Recommendations for connector layout: – Location of connector groups is most influential – Consider constructability 15% of span length 12” spacing (approx.)
  24. 24. Recommended Design Procedure Evaluate strength of existing bridge Set strengthening targets Check negative moment regions and redistribute moments as necessary Design connectors for positive moment regions Locate connectors and check fatigue strength
  25. 25. Research Questions / Answers • Is moment redistribution possible for partially composite girders (i.e., can we develop “shakedown”) ? YES – Shakedown in possible and predictable • What is the fatigue strength of the adhesive anchor shear connector ? Equations developed (based on exhaustive testing) to predict fatigue life of shear connectors, based both on stress-range and slip-range.
  26. 26. Research Questions / Answers • How do we compute the shear connector fatigue demands for a partially composite girder? Compute slip demands on shear connectors under fatigue truck (can use commercial FEA software or “UT-SLIP.”) • Can we demonstrate good performance in large-scale tests? Large-scale specimens showed excellent performance under all loading conditions. • Can we develop a straightforward design procedure? Yes.
  27. 27. Conclusions of Research Study Efficient strengthening solution – Avoid load-posting or costly deck replacements – Significant increase in load rating (up to 90%) – Excellent structural behavior – Simple and quick installation process – Straightforward design process
  28. 28. Implementation Strengthening technique currently being implemented on bridge in Lakeport, Texas

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