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PA Non-composite Adjacent Box Beam Bridges

PA Non-composite Adjacent Box Beam Bridges. A presentation adapted from the AASHTO T-18 Bridge Inspection Technical Committee Meeting. PennDOT June 2006. KEY TOPICS. SR 1014 Failure on 12/27/05, PennDOT ’ s Non-composite Adjacent Box Beam Action Items, Bridge Inventory Impacts,

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PA Non-composite Adjacent Box Beam Bridges

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  1. PA Non-composite Adjacent Box Beam Bridges A presentation adapted from the AASHTO T-18 Bridge Inspection Technical Committee Meeting PennDOT June 2006

  2. KEY TOPICS • SR 1014 Failure on 12/27/05, • PennDOT’s Non-composite Adjacent Box Beam Action Items, • Bridge Inventory Impacts, • Preliminary Research Findings, • Lessons learned.

  3. Washington County, PA SR 1014 over I-70 December 28, 2006

  4. SR 1014 over I-70 Failed Beam 14’-5” I-70 EB • Built1960 (ADT = 500) • Spans of 54’, 89’, 89’, 42’ • AASHTO Skew 51° • Vertical Clearance over I-70 14’-5”

  5. SR 1014 Bridge Cross Section Span 1 & 4 Span 2 & 3 8 Members @ 4’-0” + 7 joints @ ½” min. = 32’-31/2”

  6. SR 1014 FASCIA DETAILS • 60 3/8” PS strands • 250 ksi strand • 5,900 psi concrete • Cover ~ 1”+ • Bituminous overlay without membrane

  7. SR 1014 BEAM COLLAPSE Factors contributing to failure: • Visible and hidden strand corrosion, • Open Barrier Deflection joint, • No load transfer through shear key, • Original fabrication quality control, • Collision damage, • Salt spray, • Deck drainage leaking thru parapet joint.

  8. SR 1014 STRAND LOSSES The extent of non-detectable strand loss was revealed as beam dissection progressed: • Visual Inspection 2004 • 20 Strands Lost • Visual Assessment Post-Collapse • 28 Strands Lost (+40%) • Lab Assessment of Strand Failures • 39 Strands Lost (+95%)

  9. ACTION PLAN • Re-inspect all adjacent box beams • Structurally Deficient (SD) – By Feb 28 • Remaining 700+ By August 15 • Research - Test Beams • New Condition Rating Guidelines • New Rating Guidelines • Issued moratorium on non-composite adjacent box beam bridges

  10. 1st Generation of P/S Beams Built 1952~1962 as alternate designs. Typical Suspect Details include: • Small diameter strands (1/4” & 5/16”), • CaCl used for high early strength, • Un-vented voids w/cardboard forms, • Shear reinforcement details, • Grout/shear keys (ongoing issue), • Dimensionally-challenged.

  11. Box Beam Bridge Inventory • 801 total bridges, • 101 SD bridges before re-inspections, • 682 re-inspections completed as of 6/9/06, • 213 SD bridges after re-inspections, • 4 Bridges closed, • 12 Bridges load posted, • 17 Bridges width or lane restricted.

  12. Research - Load Tests • Two SR 1014 Beams were salvaged for full scale load tests, • Load test of interior girder confirms additional non-detectable losses, • Fascia Beam testing confirms open barrier joint contributions to failure, • Test beam fails between exposed strands and open joint.

  13. Lessons learned • Adjacent box beams are robust, but not indestructible, • Strand corrosion is very pervasive, • No proven inspection method to determine deterioration, • First generation beams had suspect details, • Questionable quality control of 1st beams, • Open barrier joint attracts cracking, • Poor load transfer = loss of redundancy, • No cost effective rehab/repair schemes.

  14. Thank you for your attention. Any questions?

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