Steel Bridge Rehabilitation Using Advanced Composites

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Steel Bridge Rehabilitation Using Advanced
Composites

• A. Chacon, M. Chajes, M. Swinehart,
• T. Miller, D. Richardson, and G. Wenczel,
• University of Delaware
• New Mexico State University

IABMAS04, Second International Conference on
Bridge Maintenance, Safety and Management, Kyoto,
Japan October 18-22, 2004
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Acknowledgments

• This material is based upon work supported by the
  National Science Foundation under Grant No.
  EEC-0139017 (NSF Research Experiences for
  Undergraduates).

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Overview

• Motivation
• Methodology
• Results
• Importance
• Conclusions

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Motivation
5
Bridge Deterioration

• Nearly 600,000 bridges in the US NBI
• Roughly 15 classified as structurally deficient
• 56 have steel superstructures (50,000 bridges)

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Advanced Composites

• High strength-to-weight ratio
• Lightweight
• Non-corrosive
• Ease of construction
• Resistance to environmental factors

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Applications of Composites to Infrastructure Rehab

• Past use of FRP mostly on concrete bridges
• Technology used on two steel bridges in Delaware
• First project (2000) and second project (2002)
  have demonstrated that retrofit of steel elements
  using CFRP plates increases stiffness of those
  members
• Repair process is fast and easy, reducing
  inconvenience to traveling public

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Methodology
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Comprehensive Research Program

• Materials selection
• Bonding
• Durability
• Force transfer
• Field demonstrations
• Pre-repair diagnostic testing and in-service
  monitoring
• Post-repair testing to evaluate effectiveness
• Long-term monitoring

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Field Demonstration-1I-95 Bridge in Delaware

• Effect on stiffness
• Environmental durability of retrofit
• Fatigue resistance of retrofit

• 3 simple spans
• (7.5m, 19m, 7.5m)
• Steel slab-on-girder
• 6,000 ADTT

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Field DemonstrationDetails

• Girder selection
• Pre-retrofit load testing
• Flange preparation
• Plate bonding
• Post-retrofit load testing

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Girder Selection
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Plate Bonding

• Pre-assembled CFRP plate sections

• CFRP plates 37 mm wide x 5 mm thick (strength 931
  MPa, modulus 110 GPa)
• Full-width CFRP plate sections created using
  several plates

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Plate Bonding

• Work platform

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Plate Bonding

• Steel surface pretreatment

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Plate Bonding

• Plate surface cleaned

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Plate Bonding

• Adhesive application

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Plate Bonding

• Placement of glass corrosion barrier

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Plate Bonding

• Plate installation and clamping

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Plate Bonding

• Completed retrofit

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Results I-95 Bridge
Diagnostic Load Tests

• Enables evaluation of bridge performance when
  subjected to trucks of known weight
• Enables pre-rehab and post-rehab performance to
  be compared

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Post-Retrofit Load Test
() strain indicates tension

• 12 increase
• in stiffness measured, 10 predicted

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Field Demonstration-2 Ashland Bridge in Delaware

• Carries Delaware SR 82 over Red Clay Creek
• Steel through girder bridge with concrete deck
• Girder span length of 30.5 meters

• Concrete deck on non-composite floor beams (floor
  beams are W24x100 sections spaced at 1.8 m and
  spanning 8.2 m)

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Ashland Bridge Details

• Floor beams and concrete deck deteriorated
• Solution CFRP plates and replacement of deck

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Bridge Rehabilitation

• Rehab Process
• Concrete deck removed
• Pretreatment applied to steel and CFRP surfaces
• Two-part epoxy applied to both surfaces
• Glass fabric layer used to prevent galvanic
  corrosion

• CFRP plates 37 mm wide x 5 mm thick (strength 931
  MPa, modulus 110 GPa)
• Full-width CFRP plate sections created using
  several plates

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Bridge Rehabilitation

• CFRP plates bonded to steel floor beam
• Adhesive allowed to cure under clamping force for
  24 hours

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Results Ashland Bridge
Diagnostic Load Tests

• Quantify bridge performance due to trucks of
  known weight (260 kN)
• Enables pre-rehab and post-rehab performance to
  be compared

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Instrumentation Plan

• Pre-test used 16 strain transducers
• Post-test used 20 strain transducers

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Pre-Rehabilitation Test
June 13, 2002

• Showed that 260 kN trucks did not cause stresses
  and strains of concern (posting was 130 kN)
• Demonstrated that slab and girder were acting
  compositely even though not designed that way
• Field testing more accurate than theoretical
  calculations

Strain Time History Max. Strain 155 me (31 MPa)
() strain indicates tension
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Post-Rehabilitation Test
June 24, 2003

• Same load passes as used during the pre-rehab
  test
• Two floor beams with CFRP plates were
  instrumented
• Three other floor beams instrumented
• Both through girders instrumented

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Through Girder Behavior
() strain indicates tension

• Peak strains for the pre-test were 140 µe (comp.)
  and 99 µe (tens.)
• Peak strains for the post-test were 111 µe
  (comp.) and 101 µe (tens.)
• Some shift in the neutral axis did occur

Pre-Test
Post-Test
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Floor Beam Behavior
() strain indicates tension
Pre-Test
Post-Test
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Analytical Predictions

• 5.5 reduction in stress due to CFRP plates
  predicted
• 6 reduction in stress due to CFRP plates measured

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Importance

• Two steel bridges in DE have been used to
  demonstrate this new repair technology
• Pre- and post repair tests have verified that
  CFRP repairs can effectively be used
• Long-term durability of the repair will continue
  to be evaluated

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Conclusions

• Advanced composites can be used for steel bridge
  rehabilitation
• Application procedure is very simple
• Designs can be based on simple analytical models
• Long-term durability of the repairs on two field
  demonstration projects will continue to be
  monitored

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Thank You
Questions