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Session 10 Purdue Research Updates Use of railroad flatcars as bridges on low-volume roads

Session 10 Purdue Research Updates Use of railroad flatcars as bridges on low-volume roads. Dr. Robert Connor Ryan Sherman Jason Provines Purdue University Wednesday, March 9, 2011. Use of Railroad flatcars as bridges on low-volume roads. Topics. Introduction Field instrumentation

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Session 10 Purdue Research Updates Use of railroad flatcars as bridges on low-volume roads

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  1. Session 10 Purdue Research Updates Use of railroad flatcars as bridges on low-volume roads

  2. Dr. Robert Connor Ryan Sherman Jason Provines Purdue University Wednesday, March 9, 2011 Use of Railroad flatcars as bridges on low-volume roads

  3. Topics • Introduction • Field instrumentation • Load rating procedure • Future tasks

  4. Introduction • Typical RRFC • 1 main longitudinal girder • 2 smaller exterior girders • Bridges • Span up to 90’ • Single or multi-span • 2 or 3 flatcars wide • Longitudinal connection

  5. Railroads to County Roads • Retired from railroad industry • Age: 40-50 years • No specs prior to 1964 • Fatigue considerations • Derailment • Economics • Attractive option for county roads • Easy installation • Span up to 90 feet • Low maintenance & cost

  6. Examples of RRFC Bridges They even make models!

  7. Load Rating RRFC Bridges • Not typical bridges • Past methods • Arkansas State University • FE modeling • Not using anymore • Iowa State University • 3 distribution factors • Need experimental data • Use field instrumentation

  8. Field Instrumentation Objectives • Understand how flatcars distribute live load • Let the cars tell us • Transverse distribution • Between cars & within car • Use field data to develop accurate load rating method

  9. Bridges for Instrumentation • 133 bridges in Indiana • 7 selected for instrumentation • Longer, single spans • Deck type • Cross section • Longitudinal connection • Low load rating • Access

  10. Bridges for Instrumentation

  11. Field Instrumentation

  12. Strain Gage Plans • What are we looking for? • Load distribution • Overall (global) behavior – main girders • Local behavior – stringers & ext. girders • Location of gages & test trucks • 103 gages on 7 bridges TYPICAL GAGE PLAN

  13. Strain Gage Installation Sealing Welding Wiring Data-logger

  14. Controlled Load Testing • 3 testing lanes • Left • Right • Center • 3 testing speeds • Crawl • Static • Dynamic • Axle dimensions & weights

  15. Load Test Data • Real time data • Does it make sense? • Troubleshooting • Where do we start?

  16. Load Rating Main Girders • What is total moment on bridge? • How much moment applied to each girder? • Distribution factor • How to calculate stress on girder? • Effective section • Difference between actual stress vs. calculated stress? • Stress reduction factor

  17. Distribution Factor - Comparison • Measured = stress in loaded girder/total stress between girders • Lever Rule is reasonably conservative for typical bridges

  18. Distribution Factor - Comparison • Special cases: Increase lever rule by 10% • CL-179: “Unknown” geometry • CL-406: “Car hauler” ?

  19. Effective Section • Have moment, now calculate stress • Need section properties • What cross section to use?

  20. Effective Section • Typical flatcar without composite deck • Main girder + 2 stringers/side • Use section properties to get stress

  21. Effective Section • Flatcar with composite concrete deck • Entire car including composite deck • Is it composite? • Rivet heads

  22. Stress Reduction Factor • Have stress, now match actual with calculated • Statics over-predicts stress • Typical flatcar with no composite deck • Stress multiplied by 0.85 • Reasonably conservative • Composite concrete deck • No reduction in stress • “Car hauler” • No reduction in stress

  23. Summary of Main Girders • Distribution factor • Lever rule is reasonably conservative • 10% increase • “Unknown” geometries • “Car haulers” • Effective section • No composite deck • Main girder + 2 stringers/side • Composite concrete deck • Entire car including composite deck • Stress reduction factor • Typical flatcar with no composite deck • 0.85 reduction • Flatcar with composite concrete deck or “car hauler” • No reduction

  24. Future Tasks • Continue with load rating procedure • “Fine tune” process for main girders • Develop similar method for stringers & deck? • Implementable • Applicable to Indiana inventory • Simple, yet not overly conservative • Develop inspection methods/criteria • Factors specific to RRFCs • Develop acquisition guidelines • Field experience & load test results

  25. Questions?

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