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Spliced Girders A Producer’s Perspective

Spliced Girders A Producer’s Perspective. by Chad Saunders Chief Engineer Bayshore Concrete Products presented at the Virginia Concrete Conference Richmond, Virginia March 11, 2005. Bayshore Concrete Products Cape Charles, VA.

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Spliced Girders A Producer’s Perspective

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  1. Spliced GirdersA Producer’s Perspective by Chad Saunders Chief Engineer Bayshore Concrete Products presented at the Virginia Concrete Conference Richmond, Virginia March 11, 2005

  2. Bayshore Concrete ProductsCape Charles, VA 90 acre casting facility on Cape Charles Harbor and Chesapeake Bay

  3. The shape. How did we get here? PCEF Prestressed Concrete Committee for Economic Fabrication • A committee established by FHWA for economic fabrication of prestressed/precast concrete • Consists of Mid Atlantic states

  4. PCEF Cross Section Variability 6” 7” 8” Different web thicknesses = diff. soffit

  5. PCEF Cross Section Variability 58” 59” 60” 12” wider top flange = same side form with blockout removed

  6. Form modification

  7. VDOT PCBT • 32” bottom flange width • 7” thick bottom flange • 7” web • 47” top flange width

  8. Rte 123 over the Occoquan RiverFairfax and Prince William Counties VDOT’s first PCBT spliced girder bridge

  9. Location Close proximity to I-95 and Route 1 = detour = high traffic

  10. Town of Occoquan Affluent neighborhood = pressure for aesthetic design

  11. Who’s Who • Owner – VDOT • Designer – Moffatt & Nichol • General Contractor – Archer Western • Erection Engineer – McNary Bergeron • Precast – Bayshore Concrete Products • PT Hardware - VSL

  12. Erection plan Approach Girders (4 spans) End Span Haunch Drop In Haunch End Span

  13. Bridge Cross Section At Haunch Piers Other piers

  14. Concrete • Concrete – 28 day: 8000 psi • Concrete - release: 5800 psi • Low permeability • Release strength cylinders matched cured

  15. Approach Girders • 4 span unit • Pieces: 58 total beams • Type: PCBT-77 • Length: 144 ft • Weight: 73 tons • Strand: 0.6” LRS • Cast two per pour Cross section

  16. Approach Girder Casting setup Gravity abutment to withstand prestress force Conventionally prestressed with draped strands

  17. Maturity meter testing Research for more accurate prediction and control of camber by VA Tech

  18. Forms and casting Side forms with fall protection rail Placing concrete with Tuckerbuilt

  19. Storage 300 ton twin gantry crane in background

  20. Spliced Girders End span • Pieces: 28 total beams • Length: 127 ft • Weight: 88 tons Haunch • Pieces: 28 total beams • Length: 98.5 ft • Weight: 77 tons Drop-In • Pieces: 14 total beams • Length: 137 ft • Weight: 87 tons

  21. Special form needs End span and Drop-In • 34” soffit • (4) sections of end block form (end span only) • Extra 2” angle full length of side forms to create 6” thick top flange Haunch • Complete form system including soffit and side forms Approach • Standard PCBT-77

  22. Erection Sequence Temporary support Erect haunch segment then end span segment Back span = 185 ft Erect drop-in segment Main span = 225 ft

  23. Erection Sequence Make closures and begin PT Remove strong backs Cast deck and complete PT

  24. End Span and Drop Incross sections Type: Modified PCBT-77 Depth: 79” Strand: 0.6” LRS Variations: 6” thick top flange 9” wide web for PT tendons = 34” wide bottom flange & 49” wide top flange Cast two per pour End Span and Drop-In End Block at End Span

  25. End Span end condition PT ducts: (3) 4” OD for 0.6” LRS Extremely congested area due to bursting reinforcement

  26. End Span and Drop-In connection at splice with haunch Very congested area due to splice plates with welded rebar and projecting rebar

  27. Casting setup Ducts in place Setting ducts

  28. End block Up close near anchorage Horizontal reinforcement

  29. End block Termination of end block Pre-assembly of end cages

  30. Splice End Top splice plates Bottom plates and projecting bars

  31. Haunch Type: Modified PCBT-77 Depth: varies from 79” to 12’-6” Strand: 0.6” LRS Variations: 6” thick top flange 9” wide web for PT tendons = 34” wide bottom flange & 49” wide top flange Cast one per pour

  32. Haunch Challenges: • 12’-6” depth at midpoint = extreme height full length • Most strands located in top flange • Location of the PT tendons makes concrete placement and consolidation difficult = addition of pour windows • Extra setup required for storing and handling of variable depth side forms and beams NTS nts

  33. Bed setup

  34. Pulling strand

  35. Stressing

  36. Rebar andPT tendons

  37. How did he tie the bars in the top flange?

  38. Forms

  39. Grout vents Top Splice Plate

  40. Look at the view from up here. Pouring with buckets

  41. First casting is a success Girder bracing

  42. Shipping • All beams to be shipped by barge starting early April 2005

  43. Erection Phase I – setting beams from the existing bridge

  44. Erection Phase II – setting beams from the phase I bridge

  45. Lessons learned • Producer - Seek possible use of SCC concrete for heavily congested area • Contractor - Get “construction engineer” involved early to ensure means and methods are established (i.e. temporary bracing embedments, special lifting requirements, strong back design, etc.) • Engineer - Require complete shop drawings from PT supplier • DOT – consider having a notch in back span girder(s) designed and included in plans to ensure maximum flexibility in construction sequence

  46. Rte 33 over the Pamunkey RiverWest Point and New Kent County What’s Next?

  47. Location

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