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Inspection and Maintenance of Weathering Steel Bridges Michael J. Todsen, P.E. PowerPoint Presentation
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Inspection and Maintenance of Weathering Steel Bridges Michael J. Todsen, P.E. Iowa Department of Transportation. Investigators. Douglas D. Crampton, P.E., S.E. Wiss, Janney, Elstner Associates. History of Weathering Steel Bridges in Iowa. 1930’s: Weathering steel first evolved

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Inspection and Maintenance of Weathering Steel Bridges

Michael J. Todsen, P.E.

Iowa Department of Transportation

slide2

Investigators

Douglas D. Crampton, P.E., S.E.

Wiss, Janney, Elstner Associates

history of weathering steel bridges in iowa
History of Weathering Steel Bridges in Iowa
  • 1930’s: Weathering steel first evolved
  • 1964: First used for a bridge application
  • 1980: Michigan moratorium, Iowa followed
  • Research studies
  • Mid-1990’s: Weathering steel bridges reintroduced in Iowa
  • Recent years: Certain Iowa bridges are not performing properly
  • Currently Iowa has approximately 139 weathering steel bridges
  • 97% were constructed after 1994
age of weathering steel bridges
Age of Weathering Steel Bridges

Number of Bridges

Year of Construction

questions for study
Questions for study
  • A few of bridges with flaking patina, heavy chloride contamination
  • What is a good patina?
  • Objective evaluation method?
  • Inspection procedures?
  • Effectiveness of washing?
  • Washing methods?
typical patina behavior
Typical Patina Behavior

Excessive chlorides,

poor exposure,

increased time of wetness

Protective Rust

project objectives
Project Objectives
  • Identify problematic bridges
  • Identify problematic locations or details
  • Evaluate inspection techniques
  • Prioritize bridges:
    • Condition
    • Location
    • Exposure
  • Recommend maintenance program
inspection and testing methods
Inspection and Testing Methods
  • Visual Inspection
  • Chloride Testing
  • Tape Adhesion
  • Color Testing
  • Core Samples
  • SEM/FTIR/XRD
inspection and testing methods1
Inspection and Testing Methods
  • Goals of Inspection Method:
    • Consistent
    • Reliable
    • Repeatable
    • Objective Results
  • Visual Inspection: easy and practical, but not always objective
  • Tape Adhesion Tests: simple, practical, and objective
  • Color Testing: not always consistent
  • Chloride Testing: not always reliable
  • Core Samples, SEM, XRD: not practical or cost effective
inspection and testing methods2
Inspection and Testing Methods

Non-Protective

Thick Rust

Increasing

Flake

Size

Protective Rust

proposed rating scale nbis format
Proposed Rating Scale (NBIS Format)
  • Overall Appearance
  • Flake Size and Density
  • Color and Consistency
iowa weathering steel bridges conditions affecting patina performance
Iowa Weathering Steel BridgesConditions Affecting Patina Performance
  • Chloride Use:
    • Salted from above
    • Salt spray from below
    • Both
    • Time of wetness
  • Location:
    • Urban
    • Suburban
    • Rural
  • Exposure:
    • Bold
    • Sheltered
    • Tunnel Effect
  • Service Below:
    • Interstate or waterway
    • Low clearance?
    • High % trucks?
  • Detailing
washing methods
Washing methods
  • Existing washing specifications (flushing):
    • Designed to not damage paint
    • Minimum 5 gallons/minute
    • Maximum 1000 psi
  • Proposed specifications (power wash):
    • Remove contaminations from surface
    • 3.5 gallons/minute
    • 3500-5000 psi, 15deg nozzel
    • Tip 12” from surface, 3-6 sf/gallon
prioritization and maintenance2
Prioritization and Maintenance

Proposed Washing Intervals

prioritization and maintenance3
Prioritization and Maintenance

Proposed Patina Maintenance

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Questions?

http://www.iowadot.gov/research/bridges_structures.html

Michael J Todsen, P.E.

Iowa Department of Transportation

(515) 233-7726

michael.todsen@dot.iowa.gov