Bridges: Past, Present, and Future

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Bridges Past, Present, and Future

• Dr. Lisa Spainhour
• Dept. of Civil and Environmental Eng.
• FAMU-FSU College of Engineering

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What Defines a Bridge?

• Four main factors define a bridge
• Span (simple, continuous, cantilever)
• Travel surface (deck, pony, through)
• Form (beam, arch, truss, etc.)
• Material (timber, concrete, steel)

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Bridge BasicsSpan Types
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Bridge BasicsTravel Surface
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Bridge BasicsTypes

• Five main types of bridges
• Beam bridge
• Truss bridge
• Arch bridge
• Cable-stayed bridge
• Suspension bridge
• Bridges may combine different types

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Beam Bridges

• Simple span top surface in compression, bottom
  in tension
• Cantilever span top in tension, bottom in
  compression
• Best for spans lt 1000, requires many supports to
  cross a long distance

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Beam BridgesTypes
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Beam BridgesExamples
Pony plate girder bridge
Stone footbridges
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Beam BridgesExamples
I-540/I-70 Interchange, NC
Lincove Viaduct, NC
I-44, 16th St. Overpass, OK
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Truss Bridges
Cantilever truss
Simple truss

• Overall behavior like a beam with less material
  in the middle
• Each member either in tension (e.g. bottom chord)
  or compression (e.g. top chord)
• Rigid because bar ends pinned into triangles
• Best for spans lt 2000.

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Truss BridgesTypes
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Truss BridgesExamples
Baihe Bridge, China
Stillwater Bridge, MN
Smithfield Street Bridge, PA
Bridge No. 1482, MN
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Covered Truss Bridges
Stone Mt. Covered Bridge, GA
Germantown Covered Bridge, OH Inverted bowstring
truss (1870s)
Town lattice truss (1830s)
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Cantilever Truss Bridges
Kingston-Rhinecliff Bridge, NY
Firth of Forth, Scotland (1890)
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Arch Bridges

• Under load, ends try to move outward, require
  strong abutments or ties to resist spreading
• When supported at ends, arch is in compression
• Best for spans of 1000 to 2000.

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Arch BridgesTypes
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Arch BridgesExamples
The Pont du Gard Aqueduct, France (Ca. 100 AD)
Thomas Aqueduct, MD (1835)
Rio Cobre Bridge, Jamaica (1800) Wrought-Iron
Ties, Cast-Iron Deck
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Arch BridgesConstruction
New River Bridge, WV
Natchez Trace Arch, TN
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Tied Arch BridgesExamples
Bayonne Bridge, NJ
Willamette River Bridge, OR
I-64 Ohio River Bridge, IN
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Suspension Bridges

• Cables (thousands of steel wires) under tension
• Towers under compression
• Require anchorages at ends to resist span
  deflection, bending of towers
• Best for spans of gt 3000.

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Suspension BridgesExamples
Menai Suspension Bridge, United Kingdom
(1826), Removed from service in 1940
Luding Iron-chain Bridge, Over Dadu River,
China (1705-06)
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Suspension BridgesExamples
Humber Bridge, England
Brooklyn Bridge, NY
Golden Gate Bridge,CA
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Tacoma Narrows Bridge Failure
Galloping Gertie
After Failure
Approach Span, After Failure
Replacement Bridge
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Cable-Stayed Bridges

• Cables under tension
• Towers, deck under compression (w/post-tensioning)
  
• No end anchorages, require less cable, and are
  faster to build than suspension bridges
• Best for spans of 1000 to 3000.

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Cable-Stayed BridgesExamples
Clark Bridge, IL
Sunshine Skyway, FL
Puente del V Centerario Seville, Spain
Normandy Bridge, France
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Cable-Stayed BridgesExamples
Footbridge, Aarhus, Denmark
Santarem-Almeirim Bridge, Portugal
Salzburg, Austria
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Cable-Stayed BridgesExamples
Leonard P. Zakim Bunker Hill Bridge, Over
Charles River Boston, MA
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Bridge BasicsMaterials

• Past
• Stone
• Timber
• Iron
• Present
• Steel
• Steel-Reinforced Concrete
• Prestressed Concrete

• Future
• Those with asterisks
• Fiber-Reinforced Polymers (FRPs)
• ???

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Bridge MaterialsFRP
Wickwire Run Bridge, West Virginia
No-Name Creek Bridge, Kansas
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FootbridgesEntirely FRP
Fiberline Bridge, Denmark
Parsons Bridge, Wales
Aberfeldy Footbridge, Scotland
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Modern Timber Bridges

• Gluelam Beams Arches
• Short lengths of treated wood bonded with epoxy
• Stiff, strong components
• Custom designed off-site
• Natural, aesthetic appearance

Keystone Wye Bridge, South Dakota, 1968
Unknown
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Modern Timber Bridges

• Stress-Laminated Bridge Decks
• Short lengths of treated wood run lengthwise
• Steel or FRP rods crosswise through holes in deck
• Stressing the rods puts steel in tension, timber
  in compression. Creates strong, stiff deck.

Wisconsin River Bridge
Steel rod anchorage
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Summary/Questions

• Four main factors define a bridge
• Span (simple, continuous, cantilever)
• Travel surface (deck, pony, through)
• Form (beam, arch, truss, etc.)
• Material (timber, concrete, steel)
• Each is suitable for different sites/conditions
• What factors affect the selection/design of a
  bridge?