Weathering Steel
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9/14/2011 1 STEEL BRIDGE FORUM Raleigh, NC September 14, 2011 Weathering Steel The Other Corrosion Protection System Bill McEleney Director, National Steel Bridge Alliance High Strength – Low Alloy Steel High strength low alloy steel • ASTM A709 - Grades 50W, HPS 50W, HPS 70W, & HPS 100W • Expect 4 times the corrosion resistance of High strength - low alloy steel carbon steel • Forms tight oxide coating (patina)
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Transcript of Weathering Steel
9/14/2011
1
STEEL BRIDGE FORUM
Raleigh, NC
September 14, 2011
Weathering SteelThe Other Corrosion Protection System
Bill McEleney
Director, National Steel Bridge Alliance
High Strength – Low Alloy Steel
High strength low alloy steel
• ASTM A709 - Grades 50W, HPS 50W, HPS 70W, & HPS 100W
• Expect 4 times the corrosion resistance of
High strength - low alloy steel
carbon steel
• Forms tight oxide coating (patina)
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Protective Patina
Weathering Steel
• Patina is a thin layer of dense corrosion b d t th t t ki t t tby-products that acts as a skin to protect against further corrosion.
• In use in United States since 1933.
• Developed for coal hopper cars to combat the corrosive effects of sulfur on steelthe corrosive effects of sulfur on steel.
• New High Performance Steel (HPS) has improved weathering characteristics.
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Simple, Low Maintenance Bridge
Use of Weathering Steel
BENEFITS CAUTIONSBENEFITS• Lower Fab Cost
• Shorter Fab Time
• No Field Painting
• Natural Appearance
• Minimal Maintenance
CAUTIONS• Not appropriate in foggy,
coastal regions
• Not for use in tunnel-like conditions where deicing salts are used
E l ti d d i• Lower Life Cycle Cost
• Evaluation needed in heavy industrial areas (corrosive chemicals)
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Uncoated vs. Coated
Use of weathering steel is growing due to:Use of weathering steel is growing due to:
• Reduced cost for blast cleaning, edge grinding and surface preparation
• Avoided cost of first coating systems
Ti i th f b i ti t ll• Time in the fabrication process to allow curing between coats
• Reduced maintenance costs; traffic impact
Cost Studies
• FIRST COST SAVINGS:FIRST COST SAVINGS:
10 TO 18%
• LIFE CYCLE SAVINGS:YES - ???YES - ???
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Relative First Costs
Material costs 3 - 4 cents/pound more
• But, painting costs significantly higher
• 12 – 20 cents/pound
• Net costs favors Weathering Steel
Material costs 3 4 cents/pound more
Net costs favors Weathering Steel
Lewisburg, PA
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Example – Lewisburg, PA
• 1223’ bridge length (886 tons total)• Material extra (@ $.03): $ 53,160• Painting cost avoided (3 coats): $ 270,674• Net 1st Cost Savings: $ 217,514• Life Cycle Cost Savings (est ): $ 1 5 M• Life Cycle Cost Savings (est.): $ 1.5 M
Design Considerations
• SITE EVALUATION• Environmental / Climatic
• Site Configuration
FHWA Technical Advisory T 5140.22
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Good Site for A588
Adequate Clearance Over Water
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Avoid Tunnel-Like Conditions
Design Considerations
• SITE EVALUATION
• DETAILS – DRAINAGE CONTROL
FHWA Technical Advisory T 5140.22
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Jointless Bridge Detail for Drainage
Jointless Bridge
536 feet continuous
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Expansion Dam – Drain Trough
Protect Steel Beneath Joints
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Weathering Steel
Design Considerations
• SITE EVALUATION
• DETAILS – DRAINAGE CONTROL
• DETAILS – STAINING
FHWA Technical Advisory T 5140.22
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Wrap For Stain Control
Drip Pan For Stain Control
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Pier Design For Stain Control
Pier Design For Stain Control
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Substructure Coating for StainControl
Substructure Material forStain Control
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Substructure Material forStain Control
Drip Bars For Stain Control
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Drip Bar Detail For Stain Control
Design Considerations
• SITE EVALUATION
• DETAILS – DRAINAGE CONTROL
• DETAILS – STAINING
• DETAILS – SURFACE PREPARATION
not in FHWA Technical Advisory T 5140.22
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Blast (SP-6) For Aesthetic Patina
Blast Fascia Only
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Maintenance Actions
• Implement procedures to detect and minimize corrosioncorrosion
• Control roadway drainage
• Regularly remove all dirt debris, etc that trap moisture
R l l t ti hi h t• Regularly remove vegetation which prevents natural drying
• Maintain covers and screens over access holes
FHWA Technical Advisory T 5140.22
Weathering Steel
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That’s Nice, But…
• .. what about when weathering steel doesn’t g‘work’?
• weathering steel issue or other?
• field painting of weathering steel
• FHWA Report – Maintenance Coating of W th i St l FHWA RD 91 087 M h ‘92Weathering Steel; FHWA-RD-91-087, March ‘92
Weathering Steel
• A proven, effective corrosion control tsystem
• Specific site conditions
• Cost effective
• Low maintenance
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STEEL BRIDGE FORUM
Raleigh, NC
September 14, 2011
QUESTIONS ??
Bill McEleney
Director, National Steel Bridge Alliance
In Florida?
SunCoast Parkway - 1999
• 3 overpasses
• Guardrail
• Light poles
• Less than 10 miles from Gulf of Mexico
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Van Dyke over SunCoast
Van Dyke over SunCoast
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Van Dyke over SunCoast
Van Dyke over SunCoast
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Van Dyke over SunCoast
Van Dyke over SunCoast
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Van Dyke over SunCoast
Van Dyke over SunCoast
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Van Dyke over SunCoast
Caldwell over SunCoast
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W. Bowman over SunCoast
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W. Bowman Over SunCoast
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STEEL BRIDGE FORUM
Raleigh, NC
September 14, 2011
QUESTIONS ??
Bill McEleney
Director, National Steel Bridge Alliance
