Transcript 2006 Scott 1 - American Association of State Highway and

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,
Preliminary Research Findings,
Lessons learned.
Washington County, PA
SR 1014 over I-70
December 28, 2006
SR 1014 over I-70
Failed Beam
14’-5”
I-70 EB
Built 1960 (ADT = 500)
Spans of 54’, 89’, 89’, 42’
AASHTO Skew 51°
Vertical Clearance over I-70 14’-5”
SR 1014 Bridge Cross Section
Span 2 & 3
Span 1 & 4
8 Members @ 4’-0” + 7 joints @ ½” min. = 32’-31/2”
SR 1014 FASCIA DETAILS
60 3/8” PS strands
250 ksi strand
5,900 psi concrete
Cover ~ 1”+
Bituminous overlay
without membrane
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.
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%)
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
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.
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.
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.
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.
Thank you for your attention.
Any questions?
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